[600MRG] FreeDV digital voice on 630 meters - Test Observations

[Andy - KU4XR]

Hi all:

Thanks for the replies to my query about FreeDV.. I took a chance and tried testing the 800XA mode.. 
I tried decoding my on air transmissions using my SDR and a second instance of FreeDV on the same PC..
It didn't work very well - BUT - I have absolutely NO experience using this mode so problems encountered
might be a result of over taxing the PC... just don't know... hi - hi...
The audio sounded like me.. not as robot as I thought it would be, but it was very choppy - in and out of sync..
That is probably due to my Osc. drift ( I have a 10 MHz OCXO on the way ).. The software states that it can
handle a drift of " less than 200 Hz " so, that's pretty tight, and I know I drift more than that..
The thing that really made me leary was watching my RF Ammeter bouncing around during a transmission..
In my understanding - That Should Not Happen ! If it is truly Constant Level - FSK - my brain tells me that
the meter should rise, and stay put !! This made me fear it was actually sending Asymmetrical modulation
and was driving the Non-Linear PA totally nuts... The fear factor took over and I shut it down.. I didn't want
to possibly blow my PA out, or tear the band to pieces.. There is No Documentation on the 800XA mode to
be found, all information is focused on the Linear modes 700C, 700D, and 1600.. The mode is interesting to me,
but I would rather be safe than sorry..

73 all:

Andy - KU4XR
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On Thu, 11/22/18, Andy - KU4XR via 600MRG <600mrg at mailman.qth.net> wrote:
 
 Hi All:
 
 FreeDV has a " Non-Linear " mode for voice... I won't pretend to know how it works, It has been explained to me
 that it takes analog input and converts it to " Constant Level - FSK Envelope " for transmission ... the software
 decodes it on the receiving end, and outputs a " robot sounding voice " ... The mode is 800XA ..
 Has anyone tried it ? And if so, any success ? Specs claim it is capable of decoding down to the noise level,
 below where standard SSB would be ripped apart by noise.. 
 Just exploring another communication possibility so, thanks for any comments..
 
 73:
 
 Andy - KU4XR