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RE: [linrad] AM and FM
- Subject: RE: [linrad] AM and FM
- From: Leif Åsbrink <leif.asbrink@xxxxxxxxxxxxxxxxxxxx
- Date: Sat, 17 Jan 2004 03:12:49 +0100
Hi Jim and all,
> It will be interesting to see if you make a noise blanker that
> works on FM. The Ham rigs fail badly at that.
Oooh, the Linrad blanker will work fine:)
> One idea comes to mind, perhaps down the road on FM.
> When you expect a 5Khz deviation FM signal, you could set
> the maximum IF bandwidth properly as an initial setting.
> The dynamic bandwidth of the signal would then be measured
> and the IF filter bandwidth would be changed quickly to match
> the instantanious deviation level. The result should be an improvment
> in S/N especially at times that the transmitter is not fully modulated.
> This would feature would be much easier in software then in hardware.
This is one way of doing it, but the advantage will be small.
When the signal is strong enough to allow an instantaneous
bandwidth measurement the signal is already fairly good....
There are conventional methods used in satellite TV for example.
It is possible to lower the threshold where S/N starts dropping
rapidly. see for example:
Zaba, thanks for the link:)