[aprssig] Interesting Preliminary Findings on Soundcard "Soft TNC" Shootout

[Stephen H. Smith]

On 12/26/2011 12:03 PM, Bill Vodall wrote:
> Fascinating and informative report.  Thank you Stephen...
>
> Doesn't the UZ7HO system also have a feature where there are multiple
> receivers listening so it should be possible to decode more off
> frequency packets?   Could that be similarly tested by varying the
> frequency of the transmitted signal while comparing the performance of
> the different TNC's?
>
>

I mention the multiple "receivers" at the bottom of the post, where I recount 
my (informal) receive test on 30 meters.



However, the controlled tests were done on FM, not SSB.  (This is mainly 
because my IFR-1500 can only generate FM or AM but not SSB signals.)  Because I 
was using FM, I couldn't change the audio tones recovered by varying the RF 
frequency of the signal generator.

However, I guess I could simulate this by changing the audio tone freqs of the 
UZ7HO instance that was modulating the signal generator.

I would like to try this whole series of experiments on SSB, but I lack a 
low-level SSB signal source that can be accurately varied in 1 dB steps or less.



Aha! It just occurred to me that I may have such a source after all!   I have a 
"retired"  Yaesu FT-100 160-to-UHF transceiver with irreplaceable blown finals 
that has been living a second life as an MF-HF-VHF-UHF general-coverage 
receiver-only.  If I take the 1/10th watt TX signal from the exciter board 
(i.e. input to the low-level driver stage), bring it out through a cable, and 
run it through a step attenuator, I could have a controllable low-level HF/SSB 
sig gen........     [This particular "receive-only" transceiver served for 
three years as my receive-only 30-meter APRS igate RX while I was living in 
Pasadena, California.]


-------------------------------------------------------------------------------

--

Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

*****  NEW   Precision Mapping 9 For UIview Released! *****
    http://wa8lmf.net/aprs/PMap9_Notes.htm


  Vista & Win7 Install Issues for UI-View and Precision Mapping
     http://wa8lmf.net/aprs/UIview_Notes.htm#VistaWin7

30-meter HF APRS over PSK63
    http://wa8lmf.net/APRS_PSK63/index.htm

"APRS 101"  Explanation of APRS Path Selection & Digipeating
   http://wa8lmf.net/DigiPaths