[pskmail] Re: Test Alpha Fldigi version for FM (VHF/UHF) links
- From: Larry Levesque <ka1vgm@xxxxxxxxx>
- To: pskmail@xxxxxxxxxxxxx
- Date: Wed, 21 Mar 2012 07:12:25 -0400
Thanks for the tips.
It is running fine on my Ubuntu 10.04 machines.
I will be doing some testing over VHF simplex in the next week or so.
I just sent a 30k file in under 2 minutes. Wow!!
On Wed, Mar 21, 2012 at 09:59:00PM +1100, John Douyere wrote:
> Some extra information regarding the usage of the new modes in FM.
>
> In my test I have noticed that it is easy to overload the TX audio and
> start loosing decoding accuracy on the other side.
>
> Since the ALC level is not related to the audio level in FM, the indicator
> I use is the Modulation level (FT-8x7 series).
>
> As an example I found that having the modulation indication at about 1/3 of
> the maximum for a single carrier PSK is about right, giving a reasonable
> audio level but no visible distortion.
>
> The multi-carrier modes can be a trap since the average level is lower than
> a single PSK carrier modulation but the peaks are the same. So it sound
> lower but the level must not be increased to compensate, otherwise the
> peaks get truncated and the decoding suffer too.
>
> In SSB, the multi carrier PSK modulations will result in an average power
> well below that of the single carrier PSK, but again we should not try to
> compensate for it.
>
> Under these modulations, if you push the TX audio level ALC too high you
> actually may well be getting only 20% of the max RIG power at the output,
> with the ALC way up.
>
> Hope this helps,
>
> 73, John
--
Larry Levesque
www.surrycomputerservices.com
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