开云体育

Greg and Larry

Re voice peaks I was monitoring the audio lines into the multiplexer on a scope and the waveforms appeared to be limiting at 400mV pk-pk no matter how I shouted.

I'm getting 40dB plus carrier suppression up to 20m and in the 30dBs for higher bands at over 10W.? That will presumably get worse at lower powers.

I'm getting significant noise on TX at low frequency end of the spectrum (no talk) . I tried to kill it with the mic comp (which sets up ok) but it doesn't seem to work on the noise.??

73 Harry? GM3RVL

On 2023-09-07 08:05, Larry Acklin wrote:

OK, this tracks with what Greg suggested- additional attenuation at
the PA and raise the gains to compensate. The bassy audio quality
could be the microphone- Electret mics are variable in quality- or

I have gotten multiple reports of "muffled audio". I tried to address it by raising the
highs with the graphic equalizer function. My microphone is not fancy - it's a Baofeng that
came with a UBITX radio kit. I did replace it with a Yaesu desk mike. Which has much smoother
lows - but still muffled.

- Jerry, KF6VB

The SG5000 codec shows .6V RMS max out of the line out. That translates to well over 1V P-P.?

Perhaps the calibration of SSB PA level will help raise the output in conjunction with your increased mic gain. The SSB Calibration of PA output obviously is another setting in software. It seems to make a difference for me, and is quite sensitive in setting levels- to get the PEP I wanted meant I had to go way down with that setting. Means the PA is too sensitive I think. I’m using the K9HZ (Bill Schmidt) PA. A -10db pad will be in my next fact finding session.?

Larry
KB3CUF



Larry

It will take some calculating to discover the optimum amplitudes out of the Audio Hat.
Voice peaks need to be accounted for.? So you can't drive too hard or the peaks will get clipped.
The T41 power control is done by varying the I and Q amplitudes.? So that is another consideration.
If you want power varied from 1 watt to 20 watts that soaks up a lot of the DAC range.
And then you have to add the voice peak problem on top of that.

--
73 Greg KF5N

OK, this tracks with what Greg suggested- additional attenuation at the PA and raise the gains to compensate. The bassy audio quality could be the microphone- Electret mics are variable in quality- or possibly RF making it’s way backwards. The spurs are what I have been working on, the noise with no microphone attached is next.?

Good progress for you!

Larry
KB3CUF

Well, that’s encouraging progress. How were you able to increase the drive levels from the audio adapter to the qse? I’m not sure but I haven’t attempted that specifically. I’m measuring the output of the QSE at the fundamental frequency (CW mode) and get a bit better than 1 mW into the PA. I also have scoped the I and Q just before the output mux and see relatively good waveforms.?

Larry
KB3CUF

Hi Larry
Thanks for the reply.
My QSE V10 signals are all getting through to the output multiplexer. I've managed to raise the multiplexer inputs to around 400mV pk-pk and that has made a big improvement to the QSE output.? The spurs I mentioned before are not visible - suspicious but not complaining!
In parallel with that I've increased the attenuation on the PA input reducing the PA drive by about 10dB.? Long term, if this works, I'll change the preamp.to give less gain.
With those changes I've just had a 5&5 contact on SSB with a station in Kent (I'm in Edinburgh).? Conditions were not good but I got through OK with about 10W on 40m. He commented that the audio was very good except that it was very bassy which fits with what I'm seeing on the SDRPlay/SDRUno.? Ive tried to alter the audio by using the equalisation option.? It sets up fine but I don't think it's doing anything.
The noise is still there on TX although a lot smaller in proportion because I'm using a bigger drive signal.
I don't have any filter in the connection from QSE to PA.
I would like to raise the 400mV signal into the multiplexer.? I tried changing the scaling in
arm_scale_f32(float_buffer_L_EX, 20, float_buffer_L_EX, 2048); //Scale to compensate for losses in Interpolation??
I changed 20 to 40 and higher but it didn't seem to make any difference.? As they say it was worth a try!
I would like to raise the 400mV to probably 1.5V or even more.
Once I maximise the output of the QSE I'll reduce the PA preamp gain.
Thanks?
Harry? GM3RVL

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?