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Problems with SSB Audio

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Paul Wilton

Problems with SSB Audio

Following some reports of bad audio (confirmed by self listening), I
have been looking at my SSB adaptor in my K2.

So far I have reached the following conclusions
a) Its not RF leakage - running with a Dummy Load still creates it
b) If I monitor the RF output with my 100MHz scope, in CW the
amplitude is clean and stable and I can change its level with the power
control pot. If I inject a single audio tone into the mic input, then
the output is cleanish but keeps jumping in amplitude - approximate a
few times a second.
c) Looking around the SSB board, I make the following observations
(with the power control pot on about 10W)

The PWR CTRL line from Pin 6 on U2 slowly rises stopping at about
5.5v after 5seconds. At the end of its rail, it "jumps" a little.
The ALC THR line from Pin5 on U2 goes instantly to the correct value.
The Base of Q1 (VRFDET) jumps around
The ALC line (Pin 2 of U1) also jumps around

It looks as if I have something amiss around the level control loop on
the SSB card. It works ok on CW.

My K2 has been working fine for a couple of years now so it is strange
it has stopped. Any suggestions where to look?

73

Paul
M1CNK

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Geoffrey Mackenzie-Kennedy-2

Re: Problems with SSB Audio

Hello Paul,

My K2/100 (with KSB2) is about the same age as yours, and some time ago it
started to act up - going as far as shutting down completely with just the
display showing the last frequency to which it was tuned. In my case the
problem was cured by removing the MCU U6 on the Control Board from its
socket, and then putting it back again. The type of IC sockets used in the
K2 do not seal the IC pin - socket connection, and corrosion can build up
causing problems. Later, and I am not suggesting that you do this as it is a
gruesome task, I replaced the socket supplied for U6 with a turned pin type
which does seal the connection, but was not brave enough to change all the
others!

Just a thought.

73,
Geoff
GM4ESD

----- Original Message -----
From: "Paul Wilton" <[hidden email]>
To: <[hidden email]>
Sent: Saturday, November 12, 2005 3:11 PM
Subject: [Elecraft] Problems with SSB Audio

> Following some reports of bad audio (confirmed by self listening), I have
> been looking at my SSB adaptor in my K2.
>
> So far I have reached the following conclusions
> a) Its not RF leakage - running with a Dummy Load still creates it
> b) If I monitor the RF output with my 100MHz scope, in CW the amplitude
> is clean and stable and I can change its level with the power control pot.
> If I inject a single audio tone into the mic input, then the output is
> cleanish but keeps jumping in amplitude - approximate a few times a
> second.
> c) Looking around the SSB board, I make the following observations
> (with the power control pot on about 10W)
>
> The PWR CTRL line from Pin 6 on U2 slowly rises stopping at about
> 5.5v after 5seconds. At the end of its rail, it "jumps" a little.
> The ALC THR line from Pin5 on U2 goes instantly to the correct value.
> The Base of Q1 (VRFDET) jumps around
> The ALC line (Pin 2 of U1) also jumps around
>
> It looks as if I have something amiss around the level control loop on the
> SSB card. It works ok on CW.
>
> My K2 has been working fine for a couple of years now so it is strange it
> has stopped. Any suggestions where to look?
>
> 73
>
> Paul
> M1CNK
>

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Paul Wilton

Re: Problems with SSB Audio

Geoff,
I did try this but it didn't solve it.

What I have found is that I was wrong in believing the CW was OK - its
not - it has a very raspy signal to it. So I will try to track that
down first.

I am confused about the behaviour of U2 on the SSB board - it seems to
take a long time to ramp up if it is setting the PWR level. However,
before I worry much more about this one, I'll try and track down my
raspy CW signal first.

73

Paul

Geoffrey Mackenzie-Kennedsy wrote:

> Hello Paul,
>
> My K2/100 (with KSB2) is about the same age as yours, and some time
> ago it started to act up - going as far as shutting down completely
> with just the display showing the last frequency to which it was
> tuned. In my case the problem was cured by removing the MCU U6 on the
> Control Board from its socket, and then putting it back again. The
> type of IC sockets used in the K2 do not seal the IC pin - socket
> connection, and corrosion can build up causing problems. Later, and I
> am not suggesting that you do this as it is a gruesome task, I
> replaced the socket supplied for U6 with a turned pin type which does
> seal the connection, but was not brave enough to change all the others!
>
> Just a thought.
>
> 73,
> Geoff
> GM4ESD
>
>
> ----- Original Message ----- From: "Paul Wilton" <[hidden email]>
> To: <[hidden email]>
> Sent: Saturday, November 12, 2005 3:11 PM
> Subject: [Elecraft] Problems with SSB Audio
>
>
>> Following some reports of bad audio (confirmed by self listening), I
>> have been looking at my SSB adaptor in my K2.
>>
>> So far I have reached the following conclusions
>> a) Its not RF leakage - running with a Dummy Load still creates it
>> b) If I monitor the RF output with my 100MHz scope, in CW the
>> amplitude is clean and stable and I can change its level with the
>> power control pot. If I inject a single audio tone into the mic
>> input, then the output is cleanish but keeps jumping in amplitude -
>> approximate a few times a second.
>> c) Looking around the SSB board, I make the following observations
>> (with the power control pot on about 10W)
>>
>> The PWR CTRL line from Pin 6 on U2 slowly rises stopping at about
>> 5.5v after 5seconds. At the end of its rail, it "jumps" a little.
>> The ALC THR line from Pin5 on U2 goes instantly to the correct value.
>> The Base of Q1 (VRFDET) jumps around
>> The ALC line (Pin 2 of U1) also jumps around
>>
>> It looks as if I have something amiss around the level control loop
>> on the SSB card. It works ok on CW.
>>
>> My K2 has been working fine for a couple of years now so it is
>> strange it has stopped. Any suggestions where to look?
>>
>> 73
>>
>> Paul
>> M1CNK
>>
>
>
>
>
>

Ron D'Eau Claire-2

RE: Problems with SSB Audio

"Raspy" is often the description given a signal from a K2 that is sitting
too close to a transformer so the a-c magnetic field modulates the VCO. If
you have a power supply, desk lamp with a transformer built in, or any other
transformer operated device nearby, try turning it off and see if your
signal clears up.

If so, there's a mod for the K2 that will dramatically improve its
resistance to magnetic field effects. See www.elecraft.com for details.

About the power control, are you expecting it to go to work before your
transmit? It won't! The power control sets the "requested" output. The
actual output doesn't change until you transmit again, and transmit long
enough for the power monitor to note the actual output and adjust the
circuit to match the "requested" level you set with the POWER control. It's
not uncommon for ops to turn on a rig and notice that even though it's been
in receive for half an hour, when the hit the key the power stays at zero
for the first dash or several dits, depending upon the keying speed. That's
because the power control circuits are only then getting some RF to work
with to set the actual power output correctly.

Ron AC7AC

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Paul Wilton
Sent: Saturday, November 12, 2005 12:46 PM
To: Elecraft Discussion List
Subject: Re: [Elecraft] Problems with SSB Audio

Geoff,
I did try this but it didn't solve it.

What I have found is that I was wrong in believing the CW was OK - its
not - it has a very raspy signal to it. So I will try to track that
down first.

I am confused about the behaviour of U2 on the SSB board - it seems to
take a long time to ramp up if it is setting the PWR level. However,
before I worry much more about this one, I'll try and track down my
raspy CW signal first.

73

Paul

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Steve & Anne Ray

Re: Problems with SSB Audio

In reply to this post by Paul Wilton

Sounds like the problem I had with my K2 on 80 meters, I tracked it down to
rf getting into my Astron 12A power supply. It only did it on 80 and 160
and running the K2 into a dummy load did not correct the problem. The
problem would show up with the K2 running as low as 4 Watts. The power
supply was setup below my steel operating desk. Tried a number of things
to cure it and finally tried another power supply, a Tripp Lite 7 Amp supply
cured the problem. I have since put a line filter on the input to the
Astron 12A and an output filter and reduced the problem of rf getting into
the Astron supply, but not completely cured it. The Trip Lite supply looks
similar into the design as the Astron, yet it is not susceptible to rf.

By the way I use a Astron 20A to run my KPA 100 with no problems and it also
ran the K2 with no problems. I now use the Astron 20A for the KPA 100 and
the Trip Lite for the K2 and the KAT100 with no problems. I recently tried
some additional filtering (ferrite choke) on the Astron 12A and still have
problems with it. Guess I will use the Astron 12A for some other stuff
where it will not be subject to rf.

72,

Steve Ray K4JPN ex K1VKW

EM82ep Warner Robins GA

Elecraft K2 1422 & KPA-100

Heath Fan HW-101, HW-8

http://www.thewinstonator.com/k4jpn.htm

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Geoffrey Mackenzie-Kennedy-2

Re: Problems with SSB Audio

In reply to this post by Paul Wilton

Paul,

In the CW mode, the sidetone oscillator Phase/ Frequency modulates to some
degree the BFO, thus the sidebands appear around the carrier. I mention
this only for "information purposes" as I doubt that the raspy sound you are
getting is related to this problem. From my K2/100 the sidebands are some
80db below carrier (measured on 40m). The sidetone signal gets into the BFO
varicap circuit at U8 on the Control Board in my K2/100.

If Ron's suggestion does not solve the problem, can you listen to the BFO
and VFO signals?

73,
Geoff
GM4ESD

----- Original Message -----
From: "Paul Wilton" <[hidden email]>
To: "Elecraft Discussion List" <[hidden email]>
Cc: "Geoffrey Mackenzie-Kennedsy" <[hidden email]>
Sent: Saturday, November 12, 2005 8:45 PM
Subject: Re: [Elecraft] Problems with SSB Audio

> Geoff,
> I did try this but it didn't solve it.
>
> What I have found is that I was wrong in believing the CW was OK - its
> not - it has a very raspy signal to it. So I will try to track that down
> first.
>
> I am confused about the behaviour of U2 on the SSB board - it seems to
> take a long time to ramp up if it is setting the PWR level. However,
> before I worry much more about this one, I'll try and track down my raspy
> CW signal first.
>
> 73
>
> Paul
>
>