Test tones in HDSDR

From Yahoo Softrock40 Group:-

77216Re: softrock40

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Mar 21, 2014
I couldn't wait to get home from a business trip and try out LC's apparently undocumented HDSDR test tones. This is an extremely useful capability and I have not seen it talked about. After some trial and error here is what I find.

The test tones are available in the AM/FM/LSB/USB modes. When in any of these modes, if you press CTL Shift G you will activate the tone generator. Subsequent presses of the same key combination will cycle you through 9 different tone/level combinations. I measured them by transmitting on an RXTX 80/40 and receiving the attenuated signal on an RXII/HDSDR and the spectrum analyzer. Here is the sequence that results from initial and subsequent combo presses:

1) Transmit on and 750 Hz at -20 dB from reference level
2) 750 Hz at -6 dB
3) 750 Hz at 0 (my arbitrary reference level, more below)
4) 750 Hz and 1750 Hz at -26 dB from reference
5) 750 Hz and 1750 Hz at -11 dB
6) 750 Hz and 1750 Hz at -6 dB
7) 750 Hz,1750 Hz, and 2350 Hz at -29 dB
8) 750 Hz,1750 Hz, and 2350 Hz at -14 dB
9) 750 Hz,1750 Hz, and 2350 Hz at -11 dB
10) Transmit off

The level measurements are probably + or - 1 dB and the tone frequencies were read out from the HDSDR spectrum display. It seems the intention was probably -20, -6, and 0 for each of the combinations.

In my first attempt to use the tones I went to #3 and raised the output level until the RF output just stopped increasing. This appears to be a good way to set the power levels for HDSDR for CW.

In my second attempt I went to #6 and adjusted the output power level slider to get my desired IMD3 level as read out on the RXII/HDSDR spectrum display. A great way to set the transmitter up for SSB. You just have to choose wisely on the desired IMD3 level: -24 dB by custom, with pretty good power and not so clean spurs, or -40 for clean as a whistle but relatively low power out.

Very very cool! An extremely useful tool for setting levels in HDSDR and for testing the RXTX transmit function.

Thank you LC!

PS: If you could find a way to make/break #3 from the RXTX paddles you would give us a GREAT CW transmitter. I'm just sayin'...........

Warren Allgyer

And LC's reply:-

Hello to Warren, Chris, Lee and everyone,

your measurent is quite good Warren. The exact amplitudes are:
1) amplitude = 0.1
2) amplitude = 0.5
3) amplitude = 0.99
4) amplitude = 0.5 * 0.1
5) amplitude = 0.5 * 0.5
6) amplitude = 0.5 * 0.99
7) amplitude = 0.33 * 0.1
8) amplitude = 0.33 * 0.5
9) amplitude = 0.33 * 0.99
what gives the levels  -20, -6, -0.1 ;  -26, -12, -6.1  and  -29.6, -15.7, -9.7 dB.
The factors 0.5 for 4-6 is to avoid oversteering with 2 tones. Factor 0.33 for 7-9 with 3 tones.

As Warren did, one should set 3) and reduce output power until having a clean output carrier. That is to avoid oversteering of output soundcard and amplifier ..

The 3 tones are chosen with 700, 1700 and 2300 Hz. This are the values in the code.
They are sort of prime, so that harmonics of lower tones don't interfere with higher tones.
I've no clue why you measure additional 50 Hz offset for each tone! But i did not test this for a long time!

Other "Easter Eggs"? Go, find them! ;-)


I understand what you are "just sayin" with RXTX paddles. But! I have absolutely no possibility to do so!!! HDSDR itself has no way to talk to the SoftRock hardware directly. Only the ExtIO from Fred can communicate with the SoftRock .. and would need to pass the paddle's state to HDSDR. But the Si570 ExtIO does NOT pass any such information concerning paddles! That is, why it's impossible to do in HDSDR.
If you know, that CW paddles are utilized in Rocky or PowerSDR (i never tried), then you should talk with Fred Krom, the developer of the ExtIO.

I'll add a CW control over serial port. ADDED see here.

kind regards,