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AC hum on tune

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k5oai

AC hum on tune

This one is a bit hard to describe, so please bare with me.

I was talking to some locals (1-5 miles) this morning on 80m LSB.
I was told that when I was tuning up a hum was heard on my signal
by the guys, which were in LSB on their receivers

I tried with low power 1w
I tried with higher power 90w
I tried it through the external amp
I tried it with the external amp off
I tried it direct to the antenna
I unplugged everything from the K3 but the power and antenna
I have switched power supplies,
I have switched AC outlets in the room.

They say they still hear the hum.

I switched to cw and
when they were still listening in LSB,
they still heard the hum on my cw signal.

IF they switch to cw on their rigs,
they do NOT hear any hum on my cw signals.

what in the world is going on here?
do I have a problem or not?
--
GB & 73
K5OAI
Sam Morgan
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KARL MARDERIAN

Re: AC hum on tune

Bad power supplies, check for hum from them. Ground radio and/or power
supplies. The A/C hum has to come from the wall supply.
That's my two cents, good luck.
N6XVT 73

Sent from my iPhone

On May 16, 2010, at 8:43 AM, Sam Morgan <[hidden email]> wrote:

> This one is a bit hard to describe, so please bare with me.
>
> I was talking to some locals (1-5 miles) this morning on 80m LSB.
> I was told that when I was tuning up a hum was heard on my signal
> by the guys, which were in LSB on their receivers
>
> I tried with low power 1w
> I tried with higher power 90w
> I tried it through the external amp
> I tried it with the external amp off
> I tried it direct to the antenna
> I unplugged everything from the K3 but the power and antenna
> I have switched power supplies,
> I have switched AC outlets in the room.
>
> They say they still hear the hum.
>
> I switched to cw and
> when they were still listening in LSB,
> they still heard the hum on my cw signal.
>
> IF they switch to cw on their rigs,
> they do NOT hear any hum on my cw signals.
>
> what in the world is going on here?
> do I have a problem or not?
> --
> GB & 73
> K5OAI
> Sam Morgan
> ______________________________________________________________
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Guy, K2AV

Re: AC hum on tune

Sometimes hum will be induced from transformers in the vicinity. Run
the K3 on a card table by itself and see if the hum follows you.

73, Guy.

On Sun, May 16, 2010 at 12:16 PM, Karl Marderian <[hidden email]> wrote:

> Bad power supplies, check for hum from them. Ground radio and/or power
> supplies. The A/C hum has to come from the wall supply.
> That's my two cents, good luck.
> N6XVT 73
>
> Sent from my iPhone
>
> On May 16, 2010, at 8:43 AM, Sam Morgan <[hidden email]> wrote:
>
>> This one is a bit hard to describe, so please bare with me.
>>
>> I was talking to some locals (1-5 miles) this morning on 80m LSB.
>> I was told that when I was tuning up a hum was heard on my signal
>> by the guys, which were in LSB on their receivers
>>
>> I tried with low power 1w
>> I tried with higher power 90w
>> I tried it through the external amp
>> I tried it with the external amp off
>> I tried it direct to the antenna
>> I unplugged everything from the K3 but the power and antenna
>> I have switched power supplies,
>> I have switched AC outlets in the room.
>>
>> They say they still hear the hum.
>>
>> I switched to cw and
>> when they were still listening in LSB,
>> they still heard the hum on my cw signal.
>>
>> IF they switch to cw on their rigs,
>> they do NOT hear any hum on my cw signals.
>>
>> what in the world is going on here?
>> do I have a problem or not?
>> --
>> GB & 73
>> K5OAI
>> Sam Morgan
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
> ______________________________________________________________
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>
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>

k5oai

Re: AC hum on tune

In reply to this post by KARL MARDERIAN

On 5/16/2010 11:22 AM, Dale Putnam wrote:
> Hey Sam,
> Good Morning, what may be happening, is your power supply has an
> excessive amount of hum, or filtering has degraded. Why they may not
> hear the hum when they use cw, is that their receivers cut off the hum
> because the cw filtering doesn't usually listen that low. If you have
> another supply, changing to it may have a significant impact.
>
I just went to battery power and hear the same hum

I have turned on a radio shack swl receiver sitting across the room
and am using 0.10w output
into the same antenna (dipole 24 ft up on roof)
So now I hearing what I think they were talking about
it's not exactly what I would call an 60 cycle ac hum
but it does modulate the tune signal at a low frequency rate

Ok including what should answer others posts as well.
the only other ac field near by is a computer switching supply about a foot
below, I don't think switching supplies create the kind of fields we are talking
about in other posts?

--
GB & 73
K5OAI
Sam Morgan
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Jim Wiley-2

Re: AC hum on tune

Sam -

If you are running the K3 on battery power, then obviously power supply
hum isn't the problem. Some possibilities:

Try changing the orientation of ANY AC operated device near the K3. If
possible, remove the item temporarily as a test. If it is not possible
to move the external device, then at least try rotating it 90 degrees in
at least 2 planes (one at a time) and test again. I have experienced
instances where a external magnetic field was "modulating" a VCO inside
a radio, and causing the sort of problem you are experiencing. The
problem may be coming from something other than a power supply. I had
an instance where the magnetic field from a TV set's horizontal
oscillator was affecting the VCO in a Kenwood 9800 VHF set, and causing
it to transmit spurs up and down the band at 15.75 kHz intervals. That
computer power supply could be a possible culprit. Try turning it off
(remove the power cord to insure a complete shutdown) just to see for
sure.

If you have not already tried this, try running the K3 with no external
connections at all - other than perhaps the battery source. That means
no antenna, no microphone or key paddle, nothing at all. It goes
without saying that any other connections should be removed for this
test - no computer interface, no external speaker, no nothing except for
the K3 by itself. I believe you should be able to key up the K3 from
the front panel using either a "test" mode or manually operated
transmit. Set the power to as low as it will go before making this
test. 1 watt or less of RF will not damage the radio even if the
antenna is completely disconnected. Listen on another receiver to see
if you still hear the hum. If you do, and if you have eliminated any
possibility of influence by an external AC field, then the problem is
internal to the K3, and it needs repair. If not, then try attaching
external connections one at a time until the hum comes back, and you
have found the basic problem.

It is possible that a "ground loop" from one or more external
connections is causing the problem.

Let us know what you find after making these tests.

- Jim, KL7CC

Sam Morgan wrote:
> <snip>
>

> I just went to battery power and hear the same hum
>
> I have turned on a radio shack swl receiver sitting across the room
> and am using 0.10w output
>
>
<snip>
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W8JI

Re: AC hum on tune

In reply to this post by k5oai

> I just went to battery power and hear the same hum
>
> I have turned on a radio shack swl receiver sitting across
> the room
> and am using 0.10w output
> into the same antenna (dipole 24 ft up on roof)
> So now I hearing what I think they were talking about
> it's not exactly what I would call an 60 cycle ac hum
> but it does modulate the tune signal at a low frequency
> rate
>
> Ok including what should answer others posts as well.
> the only other ac field near by is a computer switching
> supply about a foot
> below, I don't think switching supplies create the kind of
> fields we are talking
> about in other posts?

Sam,

It is common for me to hear hum or buzz on local receivers
very near a transmitter. Even on perfectly clean
transmitters unless I use a line tap to sample signal all
sorts of stuff mixes in. I've never really looked into why.
My guess would be it is some nasty multipath being modulated
by something. Just a guess.

I'm not saying you don't have hum, but just cautioning you
to be careful when listening on a local receiver near a
transmitter. I can replicate hum on my shop receivers even
with a very clean transmitter on the bench.

That aside, did you try disconnecting everything except the
K3 antenna and power supply?

Switching supplies do not normally cause 60 or 120 Hz
problems.

73 Tom

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Julian, G4ILO

Re: AC hum on tune

W8JI wrote

Sam,

It is common for me to hear hum or buzz on local receivers
very near a transmitter. Even on perfectly clean
transmitters unless I use a line tap to sample signal all
sorts of stuff mixes in. I've never really looked into why.
My guess would be it is some nasty multipath being modulated
by something. Just a guess.

I'm not saying you don't have hum, but just cautioning you
to be careful when listening on a local receiver near a
transmitter. I can replicate hum on my shop receivers even
with a very clean transmitter on the bench.

That aside, did you try disconnecting everything except the
K3 antenna and power supply?

Switching supplies do not normally cause 60 or 120 Hz
problems.

73 Tom

I agree with Tom. I have wasted a lot of time trying to eliminate a non existent problem caused by local monitoring.

Obviously as you have had reports from other stations there must be something wrong but I don't think the K3 is particularly prone to transformer induced modulation. Mine sits right next to a Diamond GSV3000 power supply which has a huge great transformer in it and I have never had a problem.

Julian, G4ILO. K2 #392 K3 #222 KX3 #110
* G4ILO's Shack - http://www.g4ilo.com
* KComm - http://www.g4ilo.com/kcomm.html
* KTune - http://www.g4ilo.com/ktune.html

k6dgw

Re: AC hum on tune

Julian, G4ILO wrote:
>
> Obviously as you have had reports from other stations there must be
> something wrong but I don't think the K3 is particularly prone to
> transformer induced modulation. Mine sits right next to a Diamond GSV3000
> power supply which has a huge great transformer in it and I have never had a
> problem.

Don't know about the K3, but my K2 exhibits hum if I put it on top of
the linear power supply. I'm using a big switcher AD6E graciously gave
me now and it works fine. Incidentally, I had the same problem with a
Motorola Maxtrac 70cm radio on top of an Astron linear supply.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2010 Cal QSO Party 2-3 Oct 2010
- www.cqp.org
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k5oai

Re: AC hum on tune

In reply to this post by W8JI

Well at this point I have:
gone on battery power
nothing is hooked up to the K3
except the 12v power lines from the battery

all reports of a hum on my tune signal
have come from stations 1/2 mile to 3 miles away
my output power was varied from 1w to 100w
only difference was the hum was louder with more power

one station 75.5 miles away did not hear the hum however
the 80m band was QRN with storms and local noise at the rx station

clues?:
hum is louder on 80m than on 17m
nothing different if I go to battery or on ac/dc power supplies

at this point I think for my next try
(since I have been using it on SSB only so far)
I will get on cw and see if I can get any R5 S9 T(1-6) reports
If I don't I will quit freaking out and be satisfied for now.

If that is successful I will start adding things back to the rig
ground, serial cable, line out, (external) tuner, IF output cable,
amp and keying line to amp, ground to amp, coax switch,
ground to coax switch, other antennas to coax switch, etc etc etc.....

hmmmmm lots of *stuff* involved when you get back to that point
hopefully somewhere along the way,
something will show it's self as the culprit

Thanks to all who have offered suggestions on and off list.
--
GB & 73
K5OAI
Sam Morgan

On 5/16/2010 3:03 PM, Tom W8JI wrote:

> It is common for me to hear hum or buzz on local receivers very near a
> transmitter. Even on perfectly clean transmitters unless I use a line
> tap to sample signal all sorts of stuff mixes in. I've never really
> looked into why. My guess would be it is some nasty multipath being
> modulated by something. Just a guess.
>
> I'm not saying you don't have hum, but just cautioning you to be careful
> when listening on a local receiver near a transmitter. I can replicate
> hum on my shop receivers even with a very clean transmitter on the bench.
>
> That aside, did you try disconnecting everything except the K3 antenna
> and power supply?
>
> Switching supplies do not normally cause 60 or 120 Hz problems.
>
> 73 Tom
>

Mike WA8BXN

Re: AC hum on tune

Did you try running your monitor receiver on battery?

73 - Mike WA8BXN

-------Original Message-------

From: Sam Morgan
Date: 5/16/2010 8:03:33 PM
To: Tom W8JI
Cc: [hidden email]
Subject: Re: [Elecraft] AC hum on tune

Well at this point I have:
Gone on battery power
Nothing is hooked up to the K3
Except the 12v power lines from the battery

All reports of a hum on my tune signal
Have come from stations 1/2 mile to 3 miles away
My output power was varied from 1w to 100w
Only difference was the hum was louder with more power

One station 75.5 miles away did not hear the hum however
The 80m band was QRN with storms and local noise at the rx station

Clues?:
Hum is louder on 80m than on 17m
Nothing different if I go to battery or on ac/dc power supplies

At this point I think for my next try
(since I have been using it on SSB only so far)
I will get on cw and see if I can get any R5 S9 T(1-6) reports
If I don't I will quit freaking out and be satisfied for now.

If that is successful I will start adding things back to the rig
Ground, serial cable, line out, (external) tuner, IF output cable,
Amp and keying line to amp, ground to amp, coax switch,
Ground to coax switch, other antennas to coax switch, etc etc etc.....

Hmmmmm lots of *stuff* involved when you get back to that point
Hopefully somewhere along the way,
Something will show it's self as the culprit

Thanks to all who have offered suggestions on and off list.
--
GB & 73
K5OAI
Sam Morgan

On 5/16/2010 3:03 PM, Tom W8JI wrote:

______________________________________________________________

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W8JI

Re: AC hum on tune

In reply to this post by k5oai

Sam,

First, you may be on a wild goose chase or you may have a
problem. I would like to hear a recording of the "hum".

Second, never rely on any "I can't hear it" report. Too much
of hearing a problem teeters on the skill of the person
doing the test, his equipment, his noise floor, your signal
level at his house, and so on.

The entire process you are involved in now is notoriously
unreliable because you are depending on very poor test
setups run by others with unknown experience or skills to
determine the problem.

Mike WA8BXN suggested: "Did you try running your monitor
receiver on battery?" and I agree with his suggestion. No
one knows you monitor setup is clean, especially for local
signals.

Like I said earlier. Virtually every rig I run on my shop
test bench without a closed sampling system, like running it
into a dummy load with a high attenuation line tap, has hum
induced by all the lights or something in the shop. I can
move coaxial cables around and hear the hum change, and that
hum really is not on the signal at all. It is some multipath
artifact.

Understand I'm not saying they are wrong, but no one could
say they are right with the information now.

73 Tom

----- Original Message -----
From: "Sam Morgan" <[hidden email]>
To: "Tom W8JI" <[hidden email]>
Cc: <[hidden email]>
Sent: Sunday, May 16, 2010 8:03 PM
Subject: Re: [Elecraft] AC hum on tune

> Well at this point I have:
> gone on battery power
> nothing is hooked up to the K3
> except the 12v power lines from the battery
>
> all reports of a hum on my tune signal
> have come from stations 1/2 mile to 3 miles away
> my output power was varied from 1w to 100w
> only difference was the hum was louder with more power
>
> one station 75.5 miles away did not hear the hum however
> the 80m band was QRN with storms and local noise at the rx
> station
>
> clues?:
> hum is louder on 80m than on 17m
> nothing different if I go to battery or on ac/dc power
> supplies
>
> at this point I think for my next try
> (since I have been using it on SSB only so far)
> I will get on cw and see if I can get any R5 S9 T(1-6)
> reports
> If I don't I will quit freaking out and be satisfied for
> now.
>
> If that is successful I will start adding things back to
> the rig
> ground, serial cable, line out, (external) tuner, IF
> output cable,
> amp and keying line to amp, ground to amp, coax switch,
> ground to coax switch, other antennas to coax switch, etc
> etc etc.....
>
> hmmmmm lots of *stuff* involved when you get back to that
> point
> hopefully somewhere along the way,
> something will show it's self as the culprit
>
> Thanks to all who have offered suggestions on and off
> list.
> --
> GB & 73
> K5OAI
> Sam Morgan
>
>
> On 5/16/2010 3:03 PM, Tom W8JI wrote:
>
>> It is common for me to hear hum or buzz on local
>> receivers very near a
>> transmitter. Even on perfectly clean transmitters unless
>> I use a line
>> tap to sample signal all sorts of stuff mixes in. I've
>> never really
>> looked into why. My guess would be it is some nasty
>> multipath being
>> modulated by something. Just a guess.
>>
>> I'm not saying you don't have hum, but just cautioning
>> you to be careful
>> when listening on a local receiver near a transmitter. I
>> can replicate
>> hum on my shop receivers even with a very clean
>> transmitter on the bench.
>>
>> That aside, did you try disconnecting everything except
>> the K3 antenna
>> and power supply?
>>
>> Switching supplies do not normally cause 60 or 120 Hz
>> problems.
>>
>> 73 Tom
>>
>
>

W8JI

AM again

This time receive....

I have filters from 2.7 kHz narrower in my K3. It just
doesn't sound good on AM receive. Isn't there some way to
widen it out on AM without buying AM filters I'll hardly
use?? I have some AM transmitters so I'm not worried about
TX.

I only operate AM a few hours a year.

Thanks, Tom

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Don Wilhelm-4

Re: AM again

Tom,

Unless you add the 6 kHz or the FM filter, you will have to use SSB or
Sync AM to receive those AM signals.
Any other method will restrict your AM passband to less than 1600 kHz
for the highest demodulated frequency.
If you want to transmit AM as well, you must have the 6 kHz filter.

73,
Don W3FPR

Tom W8JI wrote:

> This time receive....
>
> I have filters from 2.7 kHz narrower in my K3. It just
> doesn't sound good on AM receive. Isn't there some way to
> widen it out on AM without buying AM filters I'll hardly
> use?? I have some AM transmitters so I'm not worried about
> TX.
>
> I only operate AM a few hours a year.
>
> Thanks, Tom
>
>

Geoffrey Mackenzie-Kennedy

Re: AM again

In reply to this post by W8JI

Would you consider building a simple L-C filter consisting of a couple of
resonators?

This would help to reduce the potential high amplitude spurious responses
present on the high frequency side in the 8215 kHz to 15 kHz mixing process.

73,
Geoff
GM4ESD

From: "Tom W8JI" <[hidden email]>
Sent: Tuesday, May 18, 2010 4:02 AM

> This time receive....
>
> I have filters from 2.7 kHz narrower in my K3. It just
> doesn't sound good on AM receive. Isn't there some way to
> widen it out on AM without buying AM filters I'll hardly
> use?? I have some AM transmitters so I'm not worried about
> TX.

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k5oai

Re: AC hum on tune

In reply to this post by KARL MARDERIAN

Figured out the culprit of my "AC hum on your tuneup signal"

There is a local ham here who is blind, therefore,
He has one heck of an ear for all things audio,
He helped me setup my TX EQ a while back,
and it finally dawned on me to ask him to listen to my tune signal,
and sure enough, he was able to hear and identify it.

But it's not a power supply's 60cps or even 120cps,
it's a slight bit of RF on my signal.
of course, it's more prevalent when using the the amp,
(450w out of an AL-811, driven with 32w from the K3)
and when I go to 100w out of just the K3 it's almost inaudible.

So, suspicions confirmed, the K3 is NOT sick,
nor is it poorly designed,
sorry about that last comment,
but due to the tone of a few recent posts,
I felt the need to restate the obvious here! :-)

Now, back to chasing my rf grounding gremlins around the shack.
tag ur it, sigh, hi hi.

Thanks again Elecraft for great products and service.
--
GB & 73
K5OAI
Sam Morgan
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