[hpsdr] Residual noise in SSB mode TX...with no input connected

[Doug W5WC]

Hi Paul,

You might try adjusting the 'Line In Gain'. You will find this control on
the Setup=>Transmit page.

This adjusts the hardware preamp that's on your Penny board and it will
affect the SNR. The Mic Gain can be adjusted from -40dB to +40dB. The
controls you see to the left of the 'Mic In' and 'Line In' sets the maximum
and minimum levels you can adjust the console slider to. A blue 'MIC' button
means the transmit audio chain is muted.

73, Doug
W5WC

-----Original Message-----
From: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] On Behalf Of Paul Wende
Sent: Saturday, February 09, 2013 9:29 PM
To: hpsdr at lists.openhpsdr.org
Subject: [hpsdr] Residual noise in SSB mode TX...with no input connected

***** High Performance Software Defined Radio Discussion List *****

Hi Guys,

Well I had a wonderful day of playing radio today, my first day with the
HPSDR on SSB and I worked all over Europe and Japan on 20 and 15M. I
received great audio reports despite my locally monitored "crappy" sounding
audio. I don't like the way it sound sin the headphones on SSB. I am using
the Penelope, Mercury and Magister, driving the Collins HF-8020. 

That is the setup, and what I am seeing is this. I normally drive the line
in on the d-sub on the Penny, with broadcast processors, but today I noticed
that even with NOTHING connected to the d-sub, or the mic input, I was
seeing quite a lot of noise on the panadaptor, and hearing it in a separate
RX, without the amplifier on, i.e., just 100mW out of the Penny. This was
with the mic gain at +10 or whatever max is on Power SDR V2.2.9, as high as
it would go. The noise was a linear decrease as I dropped the slider down to
minimum. At minimum gain, the noise is gone. This is also with the mic
button not lit up blue, i.e. it was using the line in. When I clicked the
MIC button, and made it blue, the noise went away. I disconnected the d-sub
cable and it made no difference.

I need to use the line in as my audio chain is all +4dBm. I could pad down
to use the mic input, but I want to fix this noise on the line in.

Any thoughts?

Thanks all,

Paul
VE7KHz

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