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K3: 6M SSB audio hash

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James C. Hall, MD-2

K3: 6M SSB audio hash

Hello:

I've noticed some audio hash on my SSB signal on 6M only when the PA relay
kicks in at 13 watts. My long microphone cable goes to a Multi-Switcher ->
W2IHY Noise Gate/Equalizer -> Heil Goldline microphone. This completely
disappears when I use a Kenwood hand mike direct to the K3. Thinking that
this was a classic "RF on the line" problem, I clipped on multiple ferrite
chokes with many turns on the cable coming from the K3, the Goldline mike,
and in between the switcher on noise gate. This didn't even slow it down !
Hmmm. Interestingly when the PA relay is off at 8 watts, there is absolutely
no hash.

For now, I'll just use the hand mike on 6M (which requires a bit more mike
gain) to keep a clean signal. Has anyone else noticed this ? Got a solution
?

73, Jamie

WB4YDL

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James C. Hall, MD-2

RE: K3: 6M SSB audio hash

Bob:

As a follow up, I doubt it's the Goldline mic/cable itself, as I get the
same hash with a Heil headset plugged into the switcher.

73, Jamie

WB4YDL

_____

From: [hidden email] [mailto:[hidden email]]
Sent: Friday, June 06, 2008 4:42 PM
To: James C. Hall, MD
Subject: Re: [Elecraft] K3: 6M SSB audio hash

You found out that the hash is not coming from rf on the line. Try the
Goldline mic direct. Then add the switcher (or equalizer). Then add the
other one. See when the hash shows up. This may help you narrow the
problem down.

-----Original Message-----
From: James C. Hall, MD [mailto:[hidden email]]
Sent: Friday, June 6, 2008 04:27 PM
To: [hidden email]
Subject: [Elecraft] K3: 6M SSB audio hash

Hello: I've noticed some audio hash on my SSB signal on 6M only when the PA
relay kicks in at 13 watts. My long microphone cable goes to a
Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
This completely disappears when I use a Kenwood hand mike direct to the K3.
Thinking that this was a classic "RF on the line" problem, I clipped on
multiple ferrite chokes with many turns on the cable coming from the K3, the
Goldline mike, and in between the switcher on noise gate. This didn't even
slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
there is absolutely no hash. For now, I'll just use the hand mike on 6M
(which requires a bit more mike gain) to keep a clean signal. Has anyone
else noticed this ? Got a solution ? 73, Jamie WB4YDL
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No virus found in this incoming message.
Checked by AVG.
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8:01 AM

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James C. Hall, MD-2

RE: K3: 6M SSB audio hash

In reply to this post by James C. Hall, MD-2

Bob:

Thanks for the reply. Unfortunately, I dont have a Kenwood cable for the
Goldline mike thats the beauty of the switcher. My primary rig is an
FT-1000MP MkV thus the Yaesu cable. The switcher allows that cable/mic to
be used with multiple rigs, Yaesu or not.

73, Jamie
WB4YDL

________________________________________
From: [hidden email] [mailto:[hidden email]]
Sent: Friday, June 06, 2008 4:42 PM
To: James C. Hall, MD
Subject: Re: [Elecraft] K3: 6M SSB audio hash

You found out that the hash is not coming from rf on the line. Try the
Goldline mic direct. Then add the switcher (or equalizer). Then add the
other one. See when the hash shows up. This may help you narrow the
problem down.
-----Original Message-----
From: James C. Hall, MD [mailto:[hidden email]]
Sent: Friday, June 6, 2008 04:27 PM
To: [hidden email]
Subject: [Elecraft] K3: 6M SSB audio hash

Hello: I've noticed some audio hash on my SSB signal on 6M only when the PA
relay kicks in at 13 watts. My long microphone cable goes to a
Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
This completely disappears when I use a Kenwood hand mike direct to the K3.
Thinking that this was a classic "RF on the line" problem, I clipped on
multiple ferrite chokes with many turns on the cable coming from the K3, the
Goldline mike, and in between the switcher on noise gate. This didn't even
slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
there is absolutely no hash. For now, I'll just use the hand mike on 6M
(which requires a bit more mike gain) to keep a clean signal. Has anyone
else noticed this ? Got a solution ? 73, Jamie WB4YDL
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James C. Hall, MD-2

RE: K3: 6M SSB audio hash

In reply to this post by James C. Hall, MD-2

Bob:

As a follow up, I doubt its the Goldline mic/cable itself, as I get the
same hash with a Heil headset plugged into the switcher.

73, Jamie
WB4YDL

________________________________________
From: [hidden email] [mailto:[hidden email]]
Sent: Friday, June 06, 2008 4:42 PM
To: James C. Hall, MD
Subject: Re: [Elecraft] K3: 6M SSB audio hash

You found out that the hash is not coming from rf on the line. Try the
Goldline mic direct. Then add the switcher (or equalizer). Then add the
other one. See when the hash shows up. This may help you narrow the
problem down.
-----Original Message-----
From: James C. Hall, MD [mailto:[hidden email]]
Sent: Friday, June 6, 2008 04:27 PM
To: [hidden email]
Subject: [Elecraft] K3: 6M SSB audio hash

Hello: I've noticed some audio hash on my SSB signal on 6M only when the PA
relay kicks in at 13 watts. My long microphone cable goes to a
Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
This completely disappears when I use a Kenwood hand mike direct to the K3.
Thinking that this was a classic "RF on the line" problem, I clipped on
multiple ferrite chokes with many turns on the cable coming from the K3, the
Goldline mike, and in between the switcher on noise gate. This didn't even
slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
there is absolutely no hash. For now, I'll just use the hand mike on 6M
(which requires a bit more mike gain) to keep a clean signal. Has anyone
else noticed this ? Got a solution ? 73, Jamie WB4YDL
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Don Wilhelm-4

Re: K3: 6M SSB audio hash

In reply to this post by James C. Hall, MD-2

Jamie,

The Heil headset will plug directly into the rear panel jacks - why not
give that a try as an added piece of evidence that it is not the microphone.

Most likely, something is being picked up on those long microphone
cables and is not a K3 problem at all. Are all the mic cables
shielded? Are all the cable shields connected to the plug/jack shell?
They should be.

I have not investigated the W2IHY equipment, but my understanding is
that it is setup primarily for pro mics which use balanced AF lines for
the mic audio. My suspicion is that there is something awry with the
balanced to unbalanced arrangement when used with unbalanced line
microphones such as you have there.

As far as why it shows up only when the PA turns on, I can only
speculate there too, but remember that there is more gain in the
transmit stages when the PA turns on, and that added gain may make any
small AF line pickup more pronounced in your transmit signal. If it
were from RF coupling into the audio, it would vary smoothly from low
power to high power and all RF levels in between - you indicated only
that it was there with the PA on, but did not say that it got worse as
power was increased.

73,
Don W3FPR

James C. Hall, MD wrote:

> Bob:
>
>
>
> As a follow up, I doubt it's the Goldline mic/cable itself, as I get the
> same hash with a Heil headset plugged into the switcher.
>
>
>
> 73, Jamie
>
> WB4YDL
>
>
>
>
> From: James C. Hall, MD [mailto:[hidden email]]
> Sent: Friday, June 6, 2008 04:27 PM
> To: [hidden email]
> Subject: [Elecraft] K3: 6M SSB audio hash
>
> Hello: I've noticed some audio hash on my SSB signal on 6M only when the PA
> relay kicks in at 13 watts. My long microphone cable goes to a
> Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
> This completely disappears when I use a Kenwood hand mike direct to the K3.
> Thinking that this was a classic "RF on the line" problem, I clipped on
> multiple ferrite chokes with many turns on the cable coming from the K3, the
> Goldline mike, and in between the switcher on noise gate. This didn't even
> slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
> there is absolutely no hash. For now, I'll just use the hand mike on 6M
> (which requires a bit more mike gain) to keep a clean signal. Has anyone
> else noticed this ? Got a solution ? 73, Jamie WB4YDL
>
>

James C. Hall, MD-2

RE: K3: 6M SSB audio hash

Thanks Don:

I still suspect the 10' cable to the NCS Multi-Switcher is acting like an
antenna at that high a frequency - however, nothing changed with multiple
ferrite chokes along this line. Good idea to check the back mic connector,
although direct attachment of the hand mike and the headset to the front
connector did not cause the hash. The cable is a very well constructed cable
made by NCS for the K3 (Kenwood). I can certainly ask NCS (I forgot his
name, but he's very approachable) regarding the shielding characteristics. I
use the same cables for the other radios.

You asked if it gets worse with increase in power - yes, but not very much.
It's nearly an all or nothing deal.

When using my K2/100 with 6M transverter through the W2IHY unit, there is no
problem at all. The only difference is a longer cable to a different port on
the multi-switcher to reach the K3 - which is on the other side of my
monitor/desk.

73, Jamie
WB4YDL

-----Original Message-----
From: Don Wilhelm [mailto:[hidden email]]
Sent: Friday, June 06, 2008 5:17 PM
To: James C. Hall, MD
Cc: [hidden email]
Subject: Re: [Elecraft] K3: 6M SSB audio hash

Jamie,

The Heil headset will plug directly into the rear panel jacks - why not
give that a try as an added piece of evidence that it is not the microphone.

Most likely, something is being picked up on those long microphone
cables and is not a K3 problem at all. Are all the mic cables
shielded? Are all the cable shields connected to the plug/jack shell?
They should be.

I have not investigated the W2IHY equipment, but my understanding is
that it is setup primarily for pro mics which use balanced AF lines for
the mic audio. My suspicion is that there is something awry with the
balanced to unbalanced arrangement when used with unbalanced line
microphones such as you have there.

As far as why it shows up only when the PA turns on, I can only
speculate there too, but remember that there is more gain in the
transmit stages when the PA turns on, and that added gain may make any
small AF line pickup more pronounced in your transmit signal. If it
were from RF coupling into the audio, it would vary smoothly from low
power to high power and all RF levels in between - you indicated only
that it was there with the PA on, but did not say that it got worse as
power was increased.

73,
Don W3FPR

James C. Hall, MD wrote:

PA
> relay kicks in at 13 watts. My long microphone cable goes to a
> Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
> This completely disappears when I use a Kenwood hand mike direct to the
K3.
> Thinking that this was a classic "RF on the line" problem, I clipped on
> multiple ferrite chokes with many turns on the cable coming from the K3,
the
> Goldline mike, and in between the switcher on noise gate. This didn't even
> slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
> there is absolutely no hash. For now, I'll just use the hand mike on 6M
> (which requires a bit more mike gain) to keep a clean signal. Has anyone
> else noticed this ? Got a solution ? 73, Jamie WB4YDL
>
>
No virus found in this incoming message.
Checked by AVG.
Version: 8.0.100 / Virus Database: 270.0.0/1487 - Release Date: 6/6/2008
8:01 AM

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Don Wilhelm-4

Re: K3: 6M SSB audio hash

Jamie,

Since you did not have a problem with the K2/xvtr with the same setup
brings up another thought - the K2 required a high level of mic audio
input while the K3 has plenty of mic gain.
If you have not tried it yet, you may want to reduce the mic gain
setting on the K3 and increase the gain in your external units. Using a
higher level of audio drive to the K3 just might reduce the problem or
even eliminate it. If nothing else, it might point the finger at
something you may not have considered.

I know I am posing more questions rather than providing answers, but
that is partly how troubleshooting is done.

73,
Don W3FPR

James C. Hall, MD wrote:

> Thanks Don:
>
> I still suspect the 10' cable to the NCS Multi-Switcher is acting like an
> antenna at that high a frequency - however, nothing changed with multiple
> ferrite chokes along this line. Good idea to check the back mic connector,
> although direct attachment of the hand mike and the headset to the front
> connector did not cause the hash. The cable is a very well constructed cable
> made by NCS for the K3 (Kenwood). I can certainly ask NCS (I forgot his
> name, but he's very approachable) regarding the shielding characteristics. I
> use the same cables for the other radios.
>
> You asked if it gets worse with increase in power - yes, but not very much.
> It's nearly an all or nothing deal.
>
> When using my K2/100 with 6M transverter through the W2IHY unit, there is no
> problem at all. The only difference is a longer cable to a different port on
> the multi-switcher to reach the K3 - which is on the other side of my
> monitor/desk.
>
> 73, Jamie
> WB4YDL
>
> -----Original Message-----
> From: Don Wilhelm [mailto:[hidden email]]
> Sent: Friday, June 06, 2008 5:17 PM
> To: James C. Hall, MD
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3: 6M SSB audio hash
>
> Jamie,
>
> The Heil headset will plug directly into the rear panel jacks - why not
> give that a try as an added piece of evidence that it is not the microphone.
>
> Most likely, something is being picked up on those long microphone
> cables and is not a K3 problem at all. Are all the mic cables
> shielded? Are all the cable shields connected to the plug/jack shell?
> They should be.
>
> I have not investigated the W2IHY equipment, but my understanding is
> that it is setup primarily for pro mics which use balanced AF lines for
> the mic audio. My suspicion is that there is something awry with the
> balanced to unbalanced arrangement when used with unbalanced line
> microphones such as you have there.
>
> As far as why it shows up only when the PA turns on, I can only
> speculate there too, but remember that there is more gain in the
> transmit stages when the PA turns on, and that added gain may make any
> small AF line pickup more pronounced in your transmit signal. If it
> were from RF coupling into the audio, it would vary smoothly from low
> power to high power and all RF levels in between - you indicated only
> that it was there with the PA on, but did not say that it got worse as
> power was increased.
>
> 73,
> Don W3FPR
>
> James C. Hall, MD wrote:
>
>> Bob:
>>
>>
>>
>> As a follow up, I doubt it's the Goldline mic/cable itself, as I get the
>> same hash with a Heil headset plugged into the switcher.
>>
>>
>>
>> 73, Jamie
>>
>> WB4YDL
>>
>>
>>
>>
>> From: James C. Hall, MD [mailto:[hidden email]]
>> Sent: Friday, June 6, 2008 04:27 PM
>> To: [hidden email]
>> Subject: [Elecraft] K3: 6M SSB audio hash
>>
>> Hello: I've noticed some audio hash on my SSB signal on 6M only when the
>>
> PA
>
>> relay kicks in at 13 watts. My long microphone cable goes to a
>> Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil Goldline microphone.
>> This completely disappears when I use a Kenwood hand mike direct to the
>>
> K3.
>
>> Thinking that this was a classic "RF on the line" problem, I clipped on
>> multiple ferrite chokes with many turns on the cable coming from the K3,
>>
> the
>
>> Goldline mike, and in between the switcher on noise gate. This didn't even
>> slow it down ! Hmmm. Interestingly when the PA relay is off at 8 watts,
>> there is absolutely no hash. For now, I'll just use the hand mike on 6M
>> (which requires a bit more mike gain) to keep a clean signal. Has anyone
>> else noticed this ? Got a solution ? 73, Jamie WB4YDL
>>
>>
>>
> No virus found in this incoming message.
> Checked by AVG.
> Version: 8.0.100 / Virus Database: 270.0.0/1487 - Release Date: 6/6/2008
> 8:01 AM
>
> ------------------------------------------------------------------------
>
>
> No virus found in this incoming message.
> Checked by AVG.
> Version: 8.0.100 / Virus Database: 270.0.0/1487 - Release Date: 6/6/2008 8:01 AM
>

Joe Subich, W4TV-3

RE: K3: 6M SSB audio hash

In reply to this post by Don Wilhelm-4

> I have not investigated the W2IHY equipment, but my understanding
> is that it is setup primarily for pro mics which use balanced AF
> lines for the mic audio. My suspicion is that there is something
> awry with the balanced to unbalanced arrangement when used with
> unbalanced line microphones such as you have there.

There is a significant problem in using balanced input with any
"amateur mic" - including Icom, Kenwood, Yaesu and Heil. Yaesu,
Kenwood and Heil connect the shield of the mic cable to the mic
return and not chassis (ground). Icom uses the shield as the
mic return.

When the shield of the mic cable is tied to the low side of a
balanced input, RF that SHOULD go to ground/chassis is forced
through the mic preamp instead. With the shield tied to the
mic return there is effectively a 10' piece of wire (antenna)
connected to the mic input unless the mic return is tied to
the chassis and the chassis is connected to a solid RF ground.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Don Wilhelm
> Sent: Friday, June 06, 2008 6:17 PM
> To: James C. Hall, MD
> Cc: [hidden email]
> Subject: Re: [Elecraft] K3: 6M SSB audio hash
>
>
> Jamie,
>
> The Heil headset will plug directly into the rear panel jacks
> - why not
> give that a try as an added piece of evidence that it is not
> the microphone.
>
> Most likely, something is being picked up on those long microphone
> cables and is not a K3 problem at all. Are all the mic cables
> shielded? Are all the cable shields connected to the
> plug/jack shell?
> They should be.
>
> I have not investigated the W2IHY equipment, but my understanding is
> that it is setup primarily for pro mics which use balanced AF
> lines for
> the mic audio. My suspicion is that there is something awry with the
> balanced to unbalanced arrangement when used with unbalanced line
> microphones such as you have there.
>
> As far as why it shows up only when the PA turns on, I can only
> speculate there too, but remember that there is more gain in the
> transmit stages when the PA turns on, and that added gain may
> make any
> small AF line pickup more pronounced in your transmit signal. If it
> were from RF coupling into the audio, it would vary smoothly from low
> power to high power and all RF levels in between - you indicated only
> that it was there with the PA on, but did not say that it got
> worse as
> power was increased.
>
> 73,
> Don W3FPR
>
> James C. Hall, MD wrote:
> > Bob:
> >
> >
> >
> > As a follow up, I doubt it's the Goldline mic/cable itself,
> as I get the
> > same hash with a Heil headset plugged into the switcher.
> >
> >
> >
> > 73, Jamie
> >
> > WB4YDL
> >
> >
> >
> >
> > From: James C. Hall, MD [mailto:[hidden email]]
> > Sent: Friday, June 6, 2008 04:27 PM
> > To: [hidden email]
> > Subject: [Elecraft] K3: 6M SSB audio hash
> >
> > Hello: I've noticed some audio hash on my SSB signal on 6M
> only when the PA
> > relay kicks in at 13 watts. My long microphone cable goes to a
> > Multi-Switcher -> W2IHY Noise Gate/Equalizer -> Heil
> Goldline microphone.
> > This completely disappears when I use a Kenwood hand mike
> direct to the K3.
> > Thinking that this was a classic "RF on the line" problem,
> I clipped on
> > multiple ferrite chokes with many turns on the cable coming
> from the K3, the
> > Goldline mike, and in between the switcher on noise gate.
> This didn't even
> > slow it down ! Hmmm. Interestingly when the PA relay is off
> at 8 watts,
> > there is absolutely no hash. For now, I'll just use the
> hand mike on 6M
> > (which requires a bit more mike gain) to keep a clean
> signal. Has anyone
> > else noticed this ? Got a solution ? 73, Jamie WB4YDL
> >
> >
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

Jim Brown-10

RE: K3: 6M SSB audio hash

On Fri, 6 Jun 2008 21:22:41 -0400, Joe Subich, W4TV wrote:

>There is a significant problem in using balanced input with any
>"amateur mic" - including Icom, Kenwood, Yaesu and Heil. Yaesu,
>Kenwood and Heil connect the shield of the mic cable to the mic
>return and not chassis (ground). Icom uses the shield as the
>mic return.

>When the shield of the mic cable is tied to the low side of a
>balanced input, RF that SHOULD go to ground/chassis is forced
>through the mic preamp instead. With the shield tied to the
>mic return there is effectively a 10' piece of wire (antenna)
>connected to the mic input unless the mic return is tied to
>the chassis and the chassis is connected to a solid RF ground.

This is not correct. There is nothing wrong with connecting an
unbalanced mic to a balanced input -- you simply unbalance the
input by grounding one side of the input. You lose the benefit of
the balanced circuitry's ability to reject noise, but the input
will work fine. The correct wiring is simply hot to one side,
shield to the other side AND the chassis.

I do have a serious quarrel with the W2IHY equalizer though -- it
is FAR more complex and expensive than needed to get great audio
from a pro mic with a ham rig. All you really need for an
equalizer is a good quality capacitor of suitable value in series
between the mic and the mic input of the radio. The capacitor is
chosen to provide a low frequency rolloff fairly high in the
audio passband. See

http://audiosystemsgroup.com/HamInterfacing.pdf

I have used a circuit like this with an EV RE16 and several rigs.
Total cost about $0.50. It would work equally well with any good
low-Z dynamic mic. I've also changed values in coupling
capacitors in the K2 to achieve the same result, and that works
quite well too. You don't need the capacitor with a K3, of course
-- the equalizer in DSP does the job.

Pro dynamic mics are easily connected to ham rigs -- since
they're balanced, one side of the balanced output goes to the mic
input, the other side goes to audio return, and the shield goes
to the chassis. I've done this quite successfully with an Omni V,
a TS850, and FT1000MP. By successfully, I mean that I get VERY
competitve, clean, contest-quality audio that cuts through QRM
and noise.

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Joe Subich, W4TV-3

RE: K3: 6M SSB audio hash

> This is not correct. There is nothing wrong with connecting an
> unbalanced mic to a balanced input -- you simply unbalance the
> input by grounding one side of the input. You lose the benefit of
> the balanced circuitry's ability to reject noise, but the input
> will work fine. The correct wiring is simply hot to one side,
> shield to the other side AND the chassis.

That is *NOT* what is happening ... the mic connection does not
simply "unbalance" the mic input because one side of the preamp
is still not grounded. What is happening is that the mic is
connected to the preamp in a balanced configuration but the
shield is left floating on the mic end and tied to the mic
return at the transmitter input. The mic return is then tied
back to the chassis through an RF choke (DC return).

What happens is that you now have a shield (unbalanced for RF
pickup) over top of the twisted pair (nicely balanced) mic
leads. Worse, the RF choke from mic return to ground makes
it almost certain that any RF on the mic shield will be forced
through the preamp instead of being bypassed harmlessly to the
chassis/ground.

It would be better if the mic return (and shield) was connected
directly to the chassis at the mic connector than the present
situation ... but not as good as if the shield were connected
to the chassis (usually PTT ground) and the mic treated as a
floating/balanced input.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Brown
> Sent: Saturday, June 07, 2008 12:46 AM
> To: Elecraft List
> Subject: RE: [Elecraft] K3: 6M SSB audio hash
>
>
> On Fri, 6 Jun 2008 21:22:41 -0400, Joe Subich, W4TV wrote:
>
> >There is a significant problem in using balanced input with any
> >"amateur mic" - including Icom, Kenwood, Yaesu and Heil. Yaesu,
> >Kenwood and Heil connect the shield of the mic cable to the mic
> >return and not chassis (ground). Icom uses the shield as the
> >mic return.
>
> >When the shield of the mic cable is tied to the low side of a
> >balanced input, RF that SHOULD go to ground/chassis is forced
> >through the mic preamp instead. With the shield tied to the
> >mic return there is effectively a 10' piece of wire (antenna)
> >connected to the mic input unless the mic return is tied to
> >the chassis and the chassis is connected to a solid RF ground.
>
> This is not correct. There is nothing wrong with connecting an
> unbalanced mic to a balanced input -- you simply unbalance the
> input by grounding one side of the input. You lose the benefit of
> the balanced circuitry's ability to reject noise, but the input
> will work fine. The correct wiring is simply hot to one side,
> shield to the other side AND the chassis.
>
> I do have a serious quarrel with the W2IHY equalizer though -- it
> is FAR more complex and expensive than needed to get great audio
> from a pro mic with a ham rig. All you really need for an
> equalizer is a good quality capacitor of suitable value in series
> between the mic and the mic input of the radio. The capacitor is
> chosen to provide a low frequency rolloff fairly high in the
> audio passband. See
>
> http://audiosystemsgroup.com/HamInterfacing.pdf
>
> I have used a circuit like this with an EV RE16 and several rigs.
> Total cost about $0.50. It would work equally well with any good
> low-Z dynamic mic. I've also changed values in coupling
> capacitors in the K2 to achieve the same result, and that works
> quite well too. You don't need the capacitor with a K3, of course
> -- the equalizer in DSP does the job.
>
> Pro dynamic mics are easily connected to ham rigs -- since
> they're balanced, one side of the balanced output goes to the mic
> input, the other side goes to audio return, and the shield goes
> to the chassis. I've done this quite successfully with an Omni V,
> a TS850, and FT1000MP. By successfully, I mean that I get VERY
> competitve, clean, contest-quality audio that cuts through QRM
> and noise.
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

Phillip Buckholdt-2

Re: K3: 6M SSB audio hash

In reply to this post by Jim Brown-10

Do you have anything plugged into the rear headphone jack ? I have a pair
oof Bose powered speakers plugged in and at higher power levels, I get
severe RFI,
. With the same speakers on my K-2/100 or my IC-7000 I have no trouble. When
I had a IC-746 I had no RFI in the speakers.

Just a thought.

Phil K8MBY

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Elecraft List" <[hidden email]>
Sent: Saturday, June 07, 2008 12:45 AM
Subject: RE: [Elecraft] K3: 6M SSB audio hash

> On Fri, 6 Jun 2008 21:22:41 -0400, Joe Subich, W4TV wrote:
>
>>There is a significant problem in using balanced input with any
>>"amateur mic" - including Icom, Kenwood, Yaesu and Heil. Yaesu,
>>Kenwood and Heil connect the shield of the mic cable to the mic
>>return and not chassis (ground). Icom uses the shield as the
>>mic return.
>
>>When the shield of the mic cable is tied to the low side of a
>>balanced input, RF that SHOULD go to ground/chassis is forced
>>through the mic preamp instead. With the shield tied to the
>>mic return there is effectively a 10' piece of wire (antenna)
>>connected to the mic input unless the mic return is tied to
>>the chassis and the chassis is connected to a solid RF ground.
>
> This is not correct. There is nothing wrong with connecting an
> unbalanced mic to a balanced input -- you simply unbalance the
> input by grounding one side of the input. You lose the benefit of
> the balanced circuitry's ability to reject noise, but the input
> will work fine. The correct wiring is simply hot to one side,
> shield to the other side AND the chassis.
>
> I do have a serious quarrel with the W2IHY equalizer though -- it
> is FAR more complex and expensive than needed to get great audio
> from a pro mic with a ham rig. All you really need for an
> equalizer is a good quality capacitor of suitable value in series
> between the mic and the mic input of the radio. The capacitor is
> chosen to provide a low frequency rolloff fairly high in the
> audio passband. See
>
> http://audiosystemsgroup.com/HamInterfacing.pdf
>
> I have used a circuit like this with an EV RE16 and several rigs.
> Total cost about $0.50. It would work equally well with any good
> low-Z dynamic mic. I've also changed values in coupling
> capacitors in the K2 to achieve the same result, and that works
> quite well too. You don't need the capacitor with a K3, of course
> -- the equalizer in DSP does the job.
>
> Pro dynamic mics are easily connected to ham rigs -- since
> they're balanced, one side of the balanced output goes to the mic
> input, the other side goes to audio return, and the shield goes
> to the chassis. I've done this quite successfully with an Omni V,
> a TS850, and FT1000MP. By successfully, I mean that I get VERY
> competitve, clean, contest-quality audio that cuts through QRM
> and noise.
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>

James C. Hall, MD-2

RE: K3: 6M SSB audio hash

In reply to this post by Jim Brown-10

Jim and Joe:

This is all very interesting. What do you see as my solution ? Do I need to
add a ground in some way to the cable ?

73, Jamie
WB4YDL

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Jim Brown
Sent: Friday, June 06, 2008 11:46 PM
To: Elecraft List
Subject: RE: [Elecraft] K3: 6M SSB audio hash

On Fri, 6 Jun 2008 21:22:41 -0400, Joe Subich, W4TV wrote:

>There is a significant problem in using balanced input with any
>"amateur mic" - including Icom, Kenwood, Yaesu and Heil. Yaesu,
>Kenwood and Heil connect the shield of the mic cable to the mic
>return and not chassis (ground). Icom uses the shield as the
>mic return.

>When the shield of the mic cable is tied to the low side of a
>balanced input, RF that SHOULD go to ground/chassis is forced
>through the mic preamp instead. With the shield tied to the
>mic return there is effectively a 10' piece of wire (antenna)
>connected to the mic input unless the mic return is tied to
>the chassis and the chassis is connected to a solid RF ground.

This is not correct. There is nothing wrong with connecting an
unbalanced mic to a balanced input -- you simply unbalance the
input by grounding one side of the input. You lose the benefit of
the balanced circuitry's ability to reject noise, but the input
will work fine. The correct wiring is simply hot to one side,
shield to the other side AND the chassis.

I do have a serious quarrel with the W2IHY equalizer though -- it
is FAR more complex and expensive than needed to get great audio
from a pro mic with a ham rig. All you really need for an
equalizer is a good quality capacitor of suitable value in series
between the mic and the mic input of the radio. The capacitor is
chosen to provide a low frequency rolloff fairly high in the
audio passband. See

http://audiosystemsgroup.com/HamInterfacing.pdf

I have used a circuit like this with an EV RE16 and several rigs.
Total cost about $0.50. It would work equally well with any good
low-Z dynamic mic. I've also changed values in coupling
capacitors in the K2 to achieve the same result, and that works
quite well too. You don't need the capacitor with a K3, of course
-- the equalizer in DSP does the job.

Pro dynamic mics are easily connected to ham rigs -- since
they're balanced, one side of the balanced output goes to the mic
input, the other side goes to audio return, and the shield goes
to the chassis. I've done this quite successfully with an Omni V,
a TS850, and FT1000MP. By successfully, I mean that I get VERY
competitve, clean, contest-quality audio that cuts through QRM
and noise.

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
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No virus found in this incoming message.
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5:48 PM

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James C. Hall, MD-2

RE: K3: 6M SSB audio hash

In reply to this post by Phillip Buckholdt-2

Good thought, Phil. Actually I have an external speaker plugged in, a NCS 8
ohm, and I did try unplugging the speaker to see what would happen. Same
story - no change in hash. The answer has got to be in the cable itself. If
it's verified with a solution, I can actually have another cable made.

73, Jamie
WB4YDL

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Phillip Buckholdt
Sent: Saturday, June 07, 2008 7:34 AM
To: Jim Brown; Elecraft List
Subject: Re: [Elecraft] K3: 6M SSB audio hash

Do you have anything plugged into the rear headphone jack ? I have a pair
oof Bose powered speakers plugged in and at higher power levels, I get
severe RFI,
. With the same speakers on my K-2/100 or my IC-7000 I have no trouble. When

I had a IC-746 I had no RFI in the speakers.

Just a thought.

Phil K8MBY

----- Original Message -----
From: "Jim Brown" <[hidden email]>
To: "Elecraft List" <[hidden email]>
Sent: Saturday, June 07, 2008 12:45 AM
Subject: RE: [Elecraft] K3: 6M SSB audio hash

_______________________________________________
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No virus found in this incoming message.
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5:48 PM

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Jim Brown-10

RE: K3: 6M SSB audio hash

In reply to this post by Joe Subich, W4TV-3

On Sat, 7 Jun 2008 01:41:02 -0400, Joe Subich, W4TV wrote:

>That is *NOT* what is happening ... the mic connection does not
>simply "unbalance" the mic input because one side of the preamp
>is still not grounded. What is happening is that the mic is
>connected to the preamp in a balanced configuration but the
>shield is left floating on the mic end and tied to the mic
>return at the transmitter input. The mic return is then tied
>back to the chassis through an RF choke (DC return).

That is an improper connection, a violation of AES48, and a
violation of good engineering practice. The ONLY proper connection
of ANY cable shield is to the shielding enclosure. A balanced
input can take (at least) two forms. One is a transformer. The
other is a differential input stage. The mic must be connected to
the two terminals of those inputs, and the shield must go straight
to the chassis, NOT through a choke.

You say "What is happening" -- do you mean that this is wiring
provided by the W2IHY box? If so, I agree it is really bad.

>It would be better if the mic return (and shield) was connected
>directly to the chassis at the mic connector than the present
>situation

Absolutely -- it is the ONLY right way to connect a cable shield.

>... but not as good as if the shield were connected to the
>chassis (usually PTT ground) and the mic treated as a
>floating/balanced input.

WRONG! What you have just described is perfect example of a pin 1
problem, and a VERY common cause of hum, buzz, and RFI.

See AES48. http://www.aes.org/publications/standards/list.cfm

See also the tutorials on my website.

http://audiosystemsgroup.com/publish

The pro audio world figured this out long ago. Virtually all EMC
authorities agree. It's really sad that hams have kept their heads
in the sand about it.

73,

Jim Brown K9YC

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Jim Brown-10

RE: K3: 6M SSB audio hash

In reply to this post by James C. Hall, MD-2

On Sat, 7 Jun 2008 09:08:59 -0500, James C. Hall, MD wrote:

>This is all very interesting. What do you see as my solution ? Do I need to
>add a ground in some way to the cable ?

I missed the details of exactly what you are trying to connect to what. As I
understand it, you are trying to connect an unbalanced mic to a balanced input.
The proper connection for that is to connect the two mic wires (the hot and the
shield) to the balanced input AND to connect the shield DIRECTLY TO THE CHASSIS
by a very short path.

Many products are manufactured in such a way that what I have described is
difficult -- the shield connection goes to the printed circuit board, wanders
around a while, and eventually finds the chassis. This is called a Pin 1 problem
(because it was first well understood in the pro audio world, and pin 1 is the
shield contact of a pro connector), and it is a MAJOR cause of hum, buzz, and
RFI.

If the cable shield does not go straight to the chassis, it cannot function as a
shield. If it has a long (inductive) path to the chassis, it provides a VERY
strong path for RFI into the box. See the tutorial on my website, cited in an
earlier email.

73,

Jim Brown K9YC

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Joe Subich, W4TV-3

RE: K3: 6M SSB audio hash

In reply to this post by Jim Brown-10

Jim,

Which is it? In this reply you say:

> >... but not as good as if the shield were connected to the
> >chassis (usually PTT ground) and the mic treated as a
> >floating/balanced input.
>
> WRONG! What you have just described is perfect example of a pin 1
> problem, and a VERY common cause of hum, buzz, and RFI.

but in the reply to Jamie you say:

> The proper connection for that is to connect the two mic
> wires (the hot and the shield) to the balanced input AND
> to connect the shield DIRECTLY TO THE CHASSIS by a very
> short path.

Your description says the very same thing as I did ... mic wires
floating with the shield connected directly to the chassis.

The point is that Icom, Yaesu, Kenwood and Heil all float the
mic return above the chassis and then connect the shield of the
mic cable to the floated mic return! The shield should be
connected to the PTT return - which is connected to the chassis.

Elecraft connect the mic return to chassis inside the K3 *BUT*
Pins 7 and 8 (PTT and mic return) have series chokes which result
in about 5 Ohms of resistance between both pins and the case.
The same is true for the shield/sleeve of the rear panel mic
jack ... the sleeve is floated by an RF choke with about 5 Ohms
of DC resistance.

The best solution for all amateurs is to connect the mic return
pin on the mic connector to the shell to tie both mic return and
shield to the chassis by the lowest possible resistance path.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Brown
> Sent: Saturday, June 07, 2008 12:12 PM
> To: Elecraft List
> Subject: RE: [Elecraft] K3: 6M SSB audio hash
>
>
> On Sat, 7 Jun 2008 01:41:02 -0400, Joe Subich, W4TV wrote:
>
> >That is *NOT* what is happening ... the mic connection does not
> >simply "unbalance" the mic input because one side of the preamp
> >is still not grounded. What is happening is that the mic is
> >connected to the preamp in a balanced configuration but the
> >shield is left floating on the mic end and tied to the mic
> >return at the transmitter input. The mic return is then tied
> >back to the chassis through an RF choke (DC return).
>
> That is an improper connection, a violation of AES48, and a
> violation of good engineering practice. The ONLY proper connection
> of ANY cable shield is to the shielding enclosure. A balanced
> input can take (at least) two forms. One is a transformer. The
> other is a differential input stage. The mic must be connected to
> the two terminals of those inputs, and the shield must go straight
> to the chassis, NOT through a choke.
>
> You say "What is happening" -- do you mean that this is wiring
> provided by the W2IHY box? If so, I agree it is really bad.
>
> >It would be better if the mic return (and shield) was connected
> >directly to the chassis at the mic connector than the present
> >situation
>
> Absolutely -- it is the ONLY right way to connect a cable shield.
>
> >... but not as good as if the shield were connected to the
> >chassis (usually PTT ground) and the mic treated as a
> >floating/balanced input.
>
> WRONG! What you have just described is perfect example of a pin 1
> problem, and a VERY common cause of hum, buzz, and RFI.
>
> See AES48. http://www.aes.org/publications/standards/list.cfm
>
> See also the tutorials on my website.
>
> http://audiosystemsgroup.com/publish
>
> The pro audio world figured this out long ago. Virtually all EMC
> authorities agree. It's really sad that hams have kept their heads
> in the sand about it.
>
> 73,
>
> Jim Brown K9YC
>
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

Jim Brown-10

RE: K3: 6M SSB audio hash

On Sat, 7 Jun 2008 17:50:13 -0400, Joe Subich, W4TV wrote:

>Jim,

>Which is it? In this reply you say:

>> >... but not as good as if the shield were connected to the
>> >chassis (usually PTT ground) and the mic treated as a
>> >floating/balanced input.
>>
>> WRONG! What you have just described is perfect example of a pin 1
>> problem, and a VERY common cause of hum, buzz, and RFI.

>but in the reply to Jamie you say:

>> The proper connection for that is to connect the two mic
>> wires (the hot and the shield) to the balanced input AND
>> to connect the shield DIRECTLY TO THE CHASSIS by a very
>> short path.

>Your description says the very same thing as I did ... mic wires
>floating with the shield connected directly to the chassis.

I'm not ambiguous, you are! :) "PTT ground" is ambiguous, and implies
that it goes somewhere and eventually finds the chassis. I'm talking the
CHASSIS. Period.

>The point is that Icom, Yaesu, Kenwood and Heil all float the
>mic return above the chassis and then connect the shield of the
>mic cable to the floated mic return!

>The shield should be
>connected to the PTT return - which is connected to the chassis.

The shield should be connected STRAIGHT to the CHASSIS, not to something
that is connected to the chassis. That "connected to" covers a multitude
of sins -- like a circuit trace that several inches to a phone jack
that's screwed to the chassis. That trace has inductance, and the voltage
drop across that inductance causes mischief!

>Elecraft connect the mic return to chassis inside the K3 *BUT*
>Pins 7 and 8 (PTT and mic return) have series chokes which result
>in about 5 Ohms of resistance between both pins and the case.
>The same is true for the shield/sleeve of the rear panel mic
>jack ... the sleeve is floated by an RF choke with about 5 Ohms
>of DC resistance.

Yes, they do, and I have a BIG problem with that. I had that discussion
with Wayne about three years ago. I'm not at all happy with the audio
interface on the K3. For one thing, those transformers are unshielded,
and pick up hum from power transformers nearby (like the power supply for
my power amp, which right under the operating desk). There's low level
hum when my line input is turned on (so I can playback contest messages
from the computer, or send AFSK). The hum is there with or without a
cable plugged in. This hum pickup is so bad on my neighbor's K3 that it
regenerates to full power! I suspect he has an unusually strong magnetic
field.

The one saving grace of what they are doing with the shield is that it is
also bypassed to the KIO audio daughterboard. It isn't clear to me how
the bypass capacitors on that daugherboard gets to the chassis. If it's a
short (small fraction of an inch), great. If it isn't, it's a potential
RFI problem, especially at higher frequencies. A clue (not an encouraging
one) -- the retaining screws for the DB connectors are 8 ohms off of the
chassis of the radio! Not a good thing! I haven't measured the audio
daughterboard chassis, but I suspect the same problem there. So far, I
have not had RF feedback problems, but my QTH is not challenging in that
regard -- only my 160M vertical is closer to the radio than 100 ft.

>The best solution for all amateurs is to connect the mic return
>pin on the mic connector to the shell to tie both mic return and
>shield to the chassis by the lowest possible resistance path.

The cable shield must go to the chassis. If that is the mic return, so be
it. BUT it doesn't help if the shell isn't connected to the chassis! I
use an EV RE16 with my ham rigs (a balanced dynamic mic). The shield goes
to the connector shell, the mic lines go to the mic input and the mic
return. My Yaesu FT1000MP has a pin 1 problem at its mic input that
causes it to have RF feedback on 15M and 75M. I can measure that pin 1
problem by the test method shown in my AES paper on the topic, and,
indeed, it peaks on 15M and a bit above 75M. That paper is on my website.

Putting it simply, MANY ham rigs are built with pin 1 problems. That is,
they have a design flaw that causes hum, buzz, and RFI when we connect
cables to them.

73,

Jim Brown K9YC

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Jerry Flanders

Quadra band data interface pullups?

In reply to this post by James C. Hall, MD-2

Are pullups required on the band data signal lines for automatically
band switching the Yaesu Quadra?

Jerry W4UK

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Joe Subich, W4TV-3

RE: K3: 6M SSB audio hash

In reply to this post by Jim Brown-10

> >Your description says the very same thing as I did ... mic wires
> >floating with the shield connected directly to the chassis.
>
> I'm not ambiguous, you are! :) "PTT ground" is ambiguous,
> and implies that it goes somewhere and eventually finds the
> chassis. I'm talking the CHASSIS. Period.

Then I should not have said "PTT Ground" but that is how Icom,
Kenwood and Yaesu all label their mic connectors. In all three
brands, the "PTT ground" is DC return and is, in fact, chassis
ground - usually a short jumper from the "PTT Ground" pin to
the chassis or the ground trace on a circuit board which contains
mic connector which is tied to chassis with multiple grounding
and mounting screws.

The whole point is that all of the "big three" manufacturers use
the shield in their microphones improperly by connecting it to an
ungrounded mic return instead of the chassis ("PTT Ground"). In
the schematics I have checked, every one provides a DC return for
the mic/preamp using an RF choke but connects the mic shield to
the mic return instead of the chassis.

73,

... Joe, W4TV

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Jim Brown
> Sent: Saturday, June 07, 2008 7:09 PM
> To: Elecraft List
> Subject: RE: [Elecraft] K3: 6M SSB audio hash
>
>
> On Sat, 7 Jun 2008 17:50:13 -0400, Joe Subich, W4TV wrote:
>
>
> >Jim,
>
> >Which is it? In this reply you say:
>
> >> >... but not as good as if the shield were connected to the
> >> >chassis (usually PTT ground) and the mic treated as a
> >> >floating/balanced input.
> >>
> >> WRONG! What you have just described is perfect example of a pin 1
> >> problem, and a VERY common cause of hum, buzz, and RFI.
>
> >but in the reply to Jamie you say:
>
> >> The proper connection for that is to connect the two mic
> >> wires (the hot and the shield) to the balanced input AND
> >> to connect the shield DIRECTLY TO THE CHASSIS by a very
> >> short path.
>
> >Your description says the very same thing as I did ... mic wires
> >floating with the shield connected directly to the chassis.
>
> I'm not ambiguous, you are! :) "PTT ground" is ambiguous,
> and implies
> that it goes somewhere and eventually finds the chassis. I'm
> talking the
> CHASSIS. Period.
>
> >The point is that Icom, Yaesu, Kenwood and Heil all float the
> >mic return above the chassis and then connect the shield of the
> >mic cable to the floated mic return!
>
> >The shield should be
> >connected to the PTT return - which is connected to the chassis.
>
> The shield should be connected STRAIGHT to the CHASSIS, not
> to something
> that is connected to the chassis. That "connected to" covers
> a multitude
> of sins -- like a circuit trace that several inches to a phone jack
> that's screwed to the chassis. That trace has inductance, and
> the voltage
> drop across that inductance causes mischief!
>
> >Elecraft connect the mic return to chassis inside the K3 *BUT*
> >Pins 7 and 8 (PTT and mic return) have series chokes which result
> >in about 5 Ohms of resistance between both pins and the case.
> >The same is true for the shield/sleeve of the rear panel mic
> >jack ... the sleeve is floated by an RF choke with about 5 Ohms
> >of DC resistance.
>
> Yes, they do, and I have a BIG problem with that. I had that
> discussion
> with Wayne about three years ago. I'm not at all happy with the audio
> interface on the K3. For one thing, those transformers are
> unshielded,
> and pick up hum from power transformers nearby (like the
> power supply for
> my power amp, which right under the operating desk). There's
> low level
> hum when my line input is turned on (so I can playback
> contest messages
> from the computer, or send AFSK). The hum is there with or without a
> cable plugged in. This hum pickup is so bad on my neighbor's
> K3 that it
> regenerates to full power! I suspect he has an unusually
> strong magnetic
> field.
>
> The one saving grace of what they are doing with the shield
> is that it is
> also bypassed to the KIO audio daughterboard. It isn't clear
> to me how
> the bypass capacitors on that daugherboard gets to the
> chassis. If it's a
> short (small fraction of an inch), great. If it isn't, it's a
> potential
> RFI problem, especially at higher frequencies. A clue (not an
> encouraging
> one) -- the retaining screws for the DB connectors are 8
> ohms off of the
> chassis of the radio! Not a good thing! I haven't measured the audio
> daughterboard chassis, but I suspect the same problem there.
> So far, I
> have not had RF feedback problems, but my QTH is not
> challenging in that
> regard -- only my 160M vertical is closer to the radio than 100 ft.
>
> >The best solution for all amateurs is to connect the mic return
> >pin on the mic connector to the shell to tie both mic return and
> >shield to the chassis by the lowest possible resistance path.
>
> The cable shield must go to the chassis. If that is the mic
> return, so be
> it. BUT it doesn't help if the shell isn't connected to the
> chassis! I
> use an EV RE16 with my ham rigs (a balanced dynamic mic). The
> shield goes
> to the connector shell, the mic lines go to the mic input and the mic
> return. My Yaesu FT1000MP has a pin 1 problem at its mic input that
> causes it to have RF feedback on 15M and 75M. I can measure
> that pin 1
> problem by the test method shown in my AES paper on the topic, and,
> indeed, it peaks on 15M and a bit above 75M. That paper is on
> my website.
>
> Putting it simply, MANY ham rigs are built with pin 1
> problems. That is,
> they have a design flaw that causes hum, buzz, and RFI when
> we connect
> cables to them.
>
> 73,
>
> Jim Brown K9YC
>
>
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Jim Brown-10

RE: K3: 6M SSB audio hash

On Sun, 8 Jun 2008 14:28:45 -0400, Joe Subich, W4TV wrote:

>Then I should not have said "PTT Ground" but that is how Icom,
>Kenwood and Yaesu all label their mic connectors. In all three
>brands, the "PTT ground" is DC return and is, in fact, chassis
>ground - usually a short jumper from the "PTT Ground" pin to
>the chassis or the ground trace on a circuit board which contains
>mic connector which is tied to chassis with multiple grounding
>and mounting screws.

Joe,

Thanks for hanging in on this issue, because it is VERY important.

My point is that what you have described is ALSO WRONG. That short jumper
can cause common impedance coupling, as the voltage drop across it is
added to circuit common. That "short jumper" has inductance, and at some
frequency, and/or at some power level, the voltage drop across it becomes
strong enough to cause RFI.

On my website are photographs of very high quality (and very expensive,
German-made) condenser mics with serious RFI problems. In one of them,
the cable shield goes to the shell of the mic with a jumper less than one
inch long. In downtown Chicago, where TV transmitters are on tall
buildings, that mic begins to detect TV broadcast stations at roughly 180
MHz. An older mic from the same manufacturer begins detecting at TV
channel 2 (54-60 MHz) and FM broadcast! Mics with shorter jumpers begin
having trouble only on higher UHF channels. They ALL have trouble with
cell phones. Documentation of this, along with the extensive testing I've
performed, are on my website.

http://audiosystemsgroup.com/publish

The voltage drop across that inductance is proportional to frequency,
inversely proportional to distance between the victim equipment and the
transmitting antenna, and proportional to the square root of the
transmitter power!

I will keep repeating this until it becomes clear. The ONLY good place to
terminate a cable shield is to the shielding enclosure DIRECTLY. Any
other connection sets up the possibility of common impedance coupling --
what pro audio folks call "the pin 1 problem."

>The whole point is that all of the "big three" manufacturers use
>the shield in their microphones improperly by connecting it to an
>ungrounded mic return instead of the chassis ("PTT Ground"). In
>the schematics I have checked, every one provides a DC return for
>the mic/preamp using an RF choke but connects the mic shield to
>the mic return instead of the chassis.

I also see this, and I strongly agree with you that it is VERY WRONG, and
is often the cause of RFI into the ham rig (what we call RF feedback).
This improper connection of cable shields is the primary cause of RFI of
all types, including RF in the shack. Add to this the US members of that
group, which should more properly be called the big five. The K2 and the
K3 have improperly terminated shields at some connectors. So does my Ten
Tec Omni V.

One piece of good news -- the front panel mic connector on the K3 IS
mounted directly to the shielding enclosure. So are all the RF
connectors.

n Sun, 8 Jun 2008 09:39:20 -0700, Brian Lloyd wrote:

>I guess that people forget that, in shielding equipment, they are
>building a Faraday cage around it. That means that you need to
>terminate your shield at the OUTSIDE of the equipment, not inside. One
>wants to continue the Faraday cage all the way out to the input
>device. This means that the shield of any wire needs to be attached to
>the chassis externally. That isn't hard to understand. I know that I
>solved the problem in my designs by using shielded twisted-pair for
>phono cartridge input and tying the shield to the chassis.

YES!

73,

Jim Brown K9YC

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