On 2023-09-07 00:43, Harry Brash wrote:

I’ve since turned off the PA and am feeding a sample of the PA drive
to my SDRPlay RSP1 SDR receiver using SDRUno. I’ve turned up the
mike gain to max (30). The “no talk” noise level is still there

*** Here's an experiment: Try disconnecting the cable between the main board and the QSE.
Does the "no talk" noise go away?

- Jerry, KF6VB

Hello Harry-
I was able to do some fault finding by switching to CW, straight key. That mode gives a chance to measure levels and trace through the board if necessary. A dry joint on anything up to and including the output of the QSE could be at fault. Look for the similarity between I and Q all the way to the output mixer ‘3253.?
Since V10/11 boards create CW as well as SSB through the ?audio adapter, this is a valid technique. I found a poor solder connection was at fault for my case.?

Larry
KB3CUF

in page 126 the RF Pre-Amp gain is about 6dB,but i compute the gain is about 7.1dB,where is the problem？

I’m wondering if there is a set of ‘expected signals and voltage levels’ available for the T41.? I’ve done a lot of fault finding in the past and such information was usually included in service manuals.? That page was often “dog-eared” as it was most used.

For example, I’ve just been looking at the signal levels in the QSE (V10) and I was surprised to see audio pk to pk levels under 100mV being applied to the multiplexer at maximum voice levels.? With that type of device and a 3V3 supply I was expecting at least 1V pk to pk.

I’ve since turned off the PA and am feeding a sample of the PA drive to my SDRPlay RSP1 SDR receiver using SDRUno.? I’ve turned up the mike gain to max (30).? The “no talk” noise level is still there but not excessive except below 100Hz.? I altered the mike compensation to cut out low frequencies but couldn’t detect any difference.? The QSE output signals don’t look too bad on the SDRUno screen but I can’t get the signal level into the QSE multiplexer above about 400mV pk-pk no matter how loud I talk.? Presumably, something in the software is applying AGC of some kind.?

Can anyone please tell me how to increase that voltage level in the software or maybe explain why it should be limited to 400mV pk-pk?

Thanks

73 Harry GM3RVL

The FX-4CR is a competitor and its small size is a real plus for those doing any ?OTA's. I have one and am really impressed with it. It can display a wider spectrum display than the G90 (48KHz vs 24KHz), had a very readable (albeit small) display,? and has 20W on all bands and all modes (even AM on 6M). Personally, I think it's better than the G90. The only thing missing is an ATU. I wrote a first impression article on it for QRPQ, but no word yet if it was accepted.

Jack, W8TEE

Bill:

Any issue with noise pickup? The magnet idea I mentioned before works well, doesn't add more wiring, and is cheaper.

Jack, W8TEE

yes! but not work!!! something wrong!

naturally in reverse order:)On Tue, Sep 5, 2023 at 10:07 PM, Harry Brash wrote:

Larry

I've been doing some tests on my V10 board system using Ver49.2.

I'm running the T41 PA into a dummy load and monitoring the stray emissions on a nearby SDRPlay/SDRUno combination.

Pressing PTT on SSB with no mike input I get the attached display on SDRUno.

The calibrations are not readible in the pic but the vertical cal lines are 100Hz apart and I calculate the spikes are 57Hz apart.

I know some folk are suspecting 60Hz mains hum but what I'm seeing here in Scotland is not mains hum as our mains is 50Hz.

I think chasing mains earth loops may be a red herring.

My own guess is there may be something wrong in the computer processing?

73? Harry GM3RVL

?On Tue, Sep 5, 2023 at 10:07 PM, Harry Brash wrote:

Larry

I've been doing some tests on my V10 board system using Ver49.2.

I'm running the T41 PA into a dummy load and monitoring the stray emissions on a nearby SDRPlay/SDRUno combination.

Pressing PTT on SSB with no mike input I get the attached display on SDRUno.

The calibrations are not readible in the pic but the vertical cal lines are 100Hz apart and I calculate the spikes are 57Hz apart.

I know some folk are suspecting 60Hz mains hum but what I'm seeing here in Scotland is not mains hum as our mains is 50Hz.

I think chasing mains earth loops may be a red herring.

My own guess is there may be something wrong in the computer processing?

73? Harry GM3RVL

?Hello Harry-
Here is my results with the floating ground I detailed earlier- mic gain -40 pic 1
then mic gain 0 pic 2
but no interference bars like before picture 3?

Larry

Larry

I've been doing some tests on my V10 board system using Ver49.2.

I'm running the T41 PA into a dummy load and monitoring the stray emissions on a nearby SDRPlay/SDRUno combination.

Pressing PTT on SSB with no mike input I get the attached display on SDRUno.

The calibrations are not readible in the pic but the vertical cal lines are 100Hz apart and I calculate the spikes are 57Hz apart.

I know some folk are suspecting 60Hz mains hum but what I'm seeing here in Scotland is not mains hum as our mains is 50Hz.

I think chasing mains earth loops may be a red herring.

My own guess is there may be something wrong in the computer processing?

73? Harry GM3RVL

Picture… Larry KB3CUF?

Ok, I floated the ground to QSE. I used a 3 pin dupont on a short TRS 1/8 and did not connect the shield to the center pin, although the shield runs the length of the wire, just hangs at the 3 pin connection that Line out R, L comes off the Teensy audio board.?

And now the audio spurs are gone. The ratty audio that tracks with mic gain remains, but the 60, 156, etc on either side of the carrier are now not there.?

That leads credence to my theory that there was a ground loop.?

Im going to try minimal mic gain and an external mic preamp to see if that helps the audio.?

Larry
KB3CUF

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The designated quiet zone near by sugar grove naval radio station maybe. ?And that anechoic chamber i built in the garage once. ?

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Who wants that?

"By the way do you know any location where a signal that low won't be buried in the environmental noise?"

How about an inefficient antenna?

A receiver located on the far side of the Moon?

--
73 Greg KF5N

I know that Greg, however, I wanted to show the 0.25uV signal in a realistic display. By the way do you know any location where a signal that low won't be buried in the environmental noise?
Al
AC8GY

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Not exactly the right impedance, but would be useful to make a point...


Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ VP2EHZ

Owner - Operator
Big Signal Ranch – K9ZC
Staunton, Illinois

Owner – Operator
Villa Grand Piton – J68HZ
Soufriere, St. Lucia W.I.
Rent it: www.VillaGrandPiton.com

Moderator: North American QRO Group at Groups.IO.
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email: bill@...

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