FreeDV

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  • Updated 3 years ago
Is there a standard/common tx/rx bandwidth for this mode?
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Guy G4DWV/4X1LT

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Posted 3 years ago

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hans weijers

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I use USB for all bands because FREEDV is a digital mode and passband is from 700Hz to 2300Hz, which works just fine.
Centerfrequency is 1500Hz from the fictive / suppressed carrier as is the case with RTTY etc.
Just give it a try, you always can go a bit narrower if needed on a crowded band..
73, Hans - PA0HWB
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Guy G4DWV/4X1LT

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Mni tnx Hans
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Ken - NM9P, Elmer

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Centered on 1500, I have found that about as narrow that I want to go is about 700 Hz each side of center. Or 1400 Hz. Anything more narrow may cut into data sub carriers.
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Guy G4DWV/4X1LT

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Thanks Ken, that is a bit different to what Hans suggested. Any reasons for your preference for a more narrow tx band?

I was just wondering in my OP is there were some sort of standard as before SSDR got the plugin, the FreeDV software http://freedv.org/tiki-index.php was the way to go.

Hope ur keeping well.

73
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Ken - NM9P, Elmer

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Hello Guy,
I just looked at the trace with the zoom fairly high and brought the skirts in until I had everything but didn't cut into the data sidebands.  The advantage is probably a minute improvement in SNR over the 1600 or 1800 wide filters.  I haven't been able to prove it as far as decoding goes, but I have noticed a difference in the signal before decoding.

As it stands now, I need about an S5 signal to get reliable decoding.  Not exactly a weak signal band.  and there is always a sort of robotic sound to the voices, especially if they have too much bass turned up.  I assume these are digitization artifacts.  I seem to get better results when I roll off my oudio below about 300 significantly.  Thank goodness (or FRS) that we have savable TX profiles!

I would like to see the FDV masters expand the bandwidth just a little and increase the voice fidelity a little bit.  With a few more data bits in there it could possibly be very nice, and still about half the bandwidth of a 3 KHz wide SSB signal.

Ken - NM9P
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Guy G4DWV/4X1LT

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Tnx for additional info Ken.