[RTTY] Some basic RTTY radio questions

[John Barber]

Very interesting indeed.

Some of us have stuck with operating methods that were best practice 30
years ago, forgetting that we are using 21st century decoders. I have been
trying different AGC settings for a while, but still can't leave the radio
filtering wide open. It just doesn't seem right!

Chen's suggestion of separate AGC for the ears can be achieved in an
external headphone amplifier. A simple solution which I use much of the time
in contests is to hang the phones round my neck, The weak signals are still
audible and the strong ones won't cause damage to my ears.

John GW4SKA



-----Original Message-----
From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of Bill Turner
Sent: 08 March 2016 09:52
To: RTTY Reflector <rtty at contesting.com>
Subject: Re: [RTTY] Some basic RTTY radio questions

Well, this is all very interesting. Thanks to David and Chen for
enlightening me. Your recommendation is something I would never have
guessed, but of course I don't write RTTY demodulator software. 

I will definitely be trying out different AGC settings in future contests. 

Thanks again,

73, Bill W6WRT


------------ ORIGINAL MESSAGE ------------(may be snipped)

On Mon, 7 Mar 2016 20:22:59 -0000, David wrote:

>I see Chen got into this one before me. Chen and I both design and make 
>available RTTY decoders. The internal workings of those decoders for 
>best performance requires that the AGC does not change the receiver 
>gain abruptly and it stays reasonably constant over several character 
>times. Fast AGC will cause problems with the automatic threshold 
>"circuit" (software actually),w which can be avoided by using slow AGC.
>
>As Chen says manual gain control that is set and left is best of all 
>but in something like a RTTY contest not practical as the human also 
>wants to hear the signal at a reasonable level. So the compromise is 
>slow AGC. Hang AGC can also work well if the parameters are set correctly.
>
>73 David G3YYD
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