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SSB Audio Problems

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Paul Wilton

SSB Audio Problems

Thanks for all the advice received so far from everyone on the list.

A couple of clarifications
a) I do not believe I have an A-C field problem. I will double check
everything but I didn't have anything within close range.

b) I don't also believe I have an RF induced problem since I am using a
well shielded dummy load

c) Re the power control, the behaviour I am seeing is occurring AFTER I
hit the PTT. The output of pin 6, U2 (PWR CTRL) on the SSB board seems
to drift upwards from 1 to 5 volts pretty slowly. However, if I turn
the power control down, it drops very quickly. Perhaps this is the
intended behaviour.

d) Annoyingly the raspy CW seems to be intermittent - it has now has
stop misbehaving now that I have time to look at it. I intend to listen
to the BFO/VFO on another receiver next time it happens.

Thanks again for all the advice.

Paul
M1CNK

Message: 19
Date: Sat, 12 Nov 2005 12:59:58 -0800
From: "Ron D'Eau Claire" <[hidden email]>
Subject: RE: [Elecraft] Problems with SSB Audio
To: "'Elecraft Discussion List'" <[hidden email]>
Message-ID: <000101c5e7cc$0addcd60$c5ddfea9@RONPORTABLE>
Content-Type: text/plain; charset="us-ascii"

"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

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Paul Wilton

Re: SSB Audio Problems

Confession time - the raspy noise did turn out to be a AC magnetic field
problem. I have a 2 foot long fluorescent tube above my desk, about 4
foot away from my K2. That is what was causing the raspy audio.

That leaves just one question- when a constant signal is injected into
the audio input in SSB mode, surely the output should also be a constant
level RF carrier. What I when looking at the RF with a scope, the peak
level jumps around by about 10-20% of the average peak level with a
random jump a few times a second. On CW the level is rock solid. Is
this expected or am I worrying about nothing in particular? It was
this behaviour that made me look at pin 6 of U2 on the SSB board since
this also seems to jump around once it has slowly reached its final value.

73

Paul
M1CNK

Paul Wilton wrote:

> Thanks for all the advice received so far from everyone on the list.
>
> A couple of clarifications
> a) I do not believe I have an A-C field problem. I will double
> check everything but I didn't have anything within close range.
>
> b) I don't also believe I have an RF induced problem since I am using
> a well shielded dummy load
>
> c) Re the power control, the behaviour I am seeing is occurring AFTER
> I hit the PTT. The output of pin 6, U2 (PWR CTRL) on the SSB board
> seems to drift upwards from 1 to 5 volts pretty slowly. However, if I
> turn the power control down, it drops very quickly. Perhaps this is
> the intended behaviour.
>
> d) Annoyingly the raspy CW seems to be intermittent - it has now has
> stop misbehaving now that I have time to look at it. I intend to
> listen to the BFO/VFO on another receiver next time it happens.
>
> Thanks again for all the advice.
>
> Paul
> M1CNK
>
> Message: 19
> Date: Sat, 12 Nov 2005 12:59:58 -0800
> From: "Ron D'Eau Claire" <[hidden email]>
> Subject: RE: [Elecraft] Problems with SSB Audio
> To: "'Elecraft Discussion List'" <[hidden email]>
> Message-ID: <000101c5e7cc$0addcd60$c5ddfea9@RONPORTABLE>
> Content-Type: text/plain; charset="us-ascii"
>
> "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
>
>
>

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Stewart Baker

Re: Re: SSB Audio Problems

Paul,

It might be worth doing the new VCO transformer mod. This adds a ferrite ring
around the VCO toroid. Unfortunately this is an option and not standard on K2's.
The power jumping may be reduced with this mod. Although you say the CW output
is stable.
http://www.elecraft.com/Apps/Power_Control_Mod.html

73
Stewart G3RXQ

On Sun, 13 Nov 2005 21:06:53 +0000, Paul Wilton wrote:

> Confession time - the raspy noise did turn out to be a AC magnetic field
>
> problem. I have a 2 foot long fluorescent tube above my desk, about 4
> foot away from my K2. That is what was causing the raspy audio.
>
> That leaves just one question- when a constant signal is injected into
> the audio input in SSB mode, surely the output should also be a constant
> level RF carrier. What I when looking at the RF with a scope, the peak
> level jumps around by about 10-20% of the average peak level with a
> random jump a few times a second. On CW the level is rock solid. Is
> this expected or am I worrying about nothing in particular? It was
> this behaviour that made me look at pin 6 of U2 on the SSB board since
> this also seems to jump around once it has slowly reached its final value.
>
> 73
>
> Paul
> M1CNK
>
> Paul Wilton wrote:
>
>> Thanks for all the advice received so far from everyone on the list.
>>
>> A couple of clarifications
>> a) I do not believe I have an A-C field problem. I will double
>> check everything but I didn't have anything within close range.
>>
>> b) I don't also believe I have an RF induced problem since I am using
>> a well shielded dummy load
>>
>> c) Re the power control, the behaviour I am seeing is occurring AFTER
>> I hit the PTT. The output of pin 6, U2 (PWR CTRL) on the SSB board
>> seems to drift upwards from 1 to 5 volts pretty slowly. However, if I
>> turn the power control down, it drops very quickly. Perhaps this is
>> the intended behaviour.
>>
>> d) Annoyingly the raspy CW seems to be intermittent - it has now has
>> stop misbehaving now that I have time to look at it. I intend to
>> listen to the BFO/VFO on another receiver next time it happens.
>>
>> Thanks again for all the advice.
>>
>> Paul
>> M1CNK
>>
>> Message: 19
>> Date: Sat, 12 Nov 2005 12:59:58 -0800
>> From: "Ron D'Eau Claire" <[hidden email]>
>> Subject: RE: [Elecraft] Problems with SSB Audio
>> To: "'Elecraft Discussion List'" <[hidden email]>
>> Message-ID: <000101c5e7cc$0addcd60$c5ddfea9@RONPORTABLE>
>> Content-Type: text/plain; charset="us-ascii"
>>
>> "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
>>
>
> _______________________________________________
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>
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