K3 Noise Transient measurements

[Mike Scott-7]

I put an oscilloscope on the right external speaker (8-ohms) of my K3 and
set up on 40M SSB @ 2.7 KHz bandwidth. The audio gain is at 9 O'clock. Band
noise is high at S-7, no signals heard. I measured steady state and start-up
noise transient voltages. Audio gain is set to Hi.

peak-to-peak noise in steady state is 0.3 volts

peak-to-peak noise during start-up transient is 5 volts

I compute this as a +24-dB start-up blast, very startling to hear

On CW 400 Hz filter I get 0.3 volts and 3.5 volts peak-to-peak or +21 dB
start up transient.

I believe that a signal or strong band noise needs to be present for this
effect to be heard. I went to 10M with S-0 band noise and I can not measure
or hear a startup transient at all. So if anyone tries to replicate this
problem from a quiet location, better hook up a noise bridge.

I believe that someone has noted that the effect has something to do with
AGC. I believe this to be correct as I can get the same noise blast by
turning the AGC off.

AGC settings as follows (I believe all default):
AGC Hold 000
AGC PLS nor
AGC SLP 012
AGC THR 005
AGC -F 120
AGC -S 020

Mike Scott - AE6WA
Tarzana, CA (DM04 / near LA)
K3-100 #508/ KX1  #1311


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[Don Wilhelm-4]

Mike,

The AGC thing may be why I don't hear it - Whenever I power on the K3 I
most always have the dummy load connected to it.  I power on first and
then select the antenna.

73,
Don W3FPR

Mike Scott wrote:

> I put an oscilloscope on the right external speaker (8-ohms) of my K3 and
> set up on 40M SSB @ 2.7 KHz bandwidth. The audio gain is at 9 O'clock. Band
> noise is high at S-7, no signals heard. I measured steady state and start-up
> noise transient voltages. Audio gain is set to Hi.
>
> peak-to-peak noise in steady state is 0.3 volts
>
> peak-to-peak noise during start-up transient is 5 volts
>
> I compute this as a +24-dB start-up blast, very startling to hear
>
> On CW 400 Hz filter I get 0.3 volts and 3.5 volts peak-to-peak or +21 dB
> start up transient.
>
> I believe that a signal or strong band noise needs to be present for this
> effect to be heard. I went to 10M with S-0 band noise and I can not measure
> or hear a startup transient at all. So if anyone tries to replicate this
> problem from a quiet location, better hook up a noise bridge.
>
> I believe that someone has noted that the effect has something to do with
> AGC. I believe this to be correct as I can get the same noise blast by
> turning the AGC off.
>
> AGC settings as follows (I believe all default):
> AGC Hold 000
> AGC PLS nor
> AGC SLP 012
> AGC THR 005
> AGC -F 120
> AGC -S 020
>
> Mike Scott - AE6WA
> Tarzana, CA (DM04 / near LA)
> K3-100 #508/ KX1  #1311
>
>
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[N5GE]

On Fri, 12 Dec 2008 17:43:34 -0500, you wrote:

>Mike,
>
>The AGC thing may be why I don't hear it - Whenever I power on the K3 I
>most always have the dummy load connected to it.  I power on first and
>then select the antenna.
>
>73,
>Don W3FPR
>
[snip]

I just tried it again here with a foreign BC station at 7.150 that has a -61dBm
signal on LP-PAN/PowerSDR.  Turned the rig off leaving it on the signal and then
turned it on again.  No pops heard.

I'm not using measuring equipment here, but it seems to me I'd know it if it was
happening with the spikes you reported.

Tom Hinson Childers, N5GE

K3 #806, XV144, XV432
Mini-Modules

http://www.eQSL.cc/Member.cfm?N5GE 
http://www.n5ge.com
http://www.swotrc.net

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