[Lowfer] MFSK, PSK, receiver tuning info needed

[Stan]

Hello Andy,

I first had to understand where my receiver was tuned to in the 
different modes of USB, LSB,
CW and CW-R( reverse).

I typically use a ICOM IC=703+ to receive 137-185-508 KHz experimental 
bands.
I had to inject a known frequency signal, acurate to better than 1 Hz, 
to see how I came out on the audio
before I fed the audio to the PC and soundcard.

I had to understand how the audio output frequency changes as I change 
the RF input with the different detection modes.
For USB and a fixed freq RF input as I tuned up the audio freq went down 
the same amount.
For CW, the tuning  was as with the LSB but with the 800 Hz BFO offset.
For CW-R, USB was used but there was the BFO offset of about 800 Hz.
The BFO offset could be menu adjusted probably +/- a few hundred Hz in 
increments of 10 Hz.

I prefer the CW-R mode.

Your equipment may vary, so you have to test and know its performance.

I receive the signal of interest using CW-R and using whatever software 
digital mode I center the program on 800 Hz
and go from there. If the RX is slightly off, I can usually adjust the 
program to decode on that signal.
Multi PSK has a frequency (spectrum display) widow much much broader 
than the BW of the signal of interest.
I just tune the program to look at the signal I want it to look at.

You will need a very accurate test signal to verify/calibrate your 
soundcard and
 RX system if you want to use ARGO for QRSS/CW modes.

I use a HP-3336B with a GPS disciplined 10 MHz reference oscillator, for 
the accuracy needed.
ARGO lets me calibrate the PC/soundcard with a 1000.000 Hz input and I 
can test the
RX and PC/soundca/program combination with a test signal at the RF freq.
ARGO QRSS-CW modes require detailed calibration.
MultiPSK requires calibration , but to a lesser extent.

I can not calibrate with WWV at 15.0 MHz and use that calibration at 
other freqs. It does not work for me.
My ham RX LO accuracy is always off, high or low, with thermal drifts, 
and long term aging drifts.
So I do a calibration every RX session.

I also usually use a 250 Hz narrow IF filter for a center +/- 125 Hz 
bandwidth about 800 Hz in CW-R.

Practice with a second computer as a (audio) transmitter to the first 
computer's soundcard line input.
transmit the various modes and tune them in on the first computer.

HTH

Stan, W1LE  FN41sr    Cape Cod


> Hello All: My greatest extent in digital comms. was
> Packet on 2 meters probably 15 years ago. DEX has
> peaked my interest in trying MultiPSK software,
> however I really don't know how to properly tune my
> received signal. I will be using USB which tunes exact
> carrier frequency - no offset, so how do I properly
> tune any particular mode for proper decoding ?? For
> info purposes, my CW mode receives 800Hz up from
> displayed frequency. Right now seeing a lot of
> gibberish on the screen. I am familiar with the
> tracking LED's, but even when I tune and lock the
> green LED I still get gibberish, most likely I'm in
> the wrong mode. Got a lot to learn, so any help will
> be appreciated. Tnx, and 73, - Andy - KU4XR
>
>
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