[1000mp] Roofing filter

[George, W5YR]

Most noise blankers depend upon recognizing the short rise time of noise
pulses to differentiate between signal and noise. The more selectivity ahead
of the blanker, the longer the rise time and the less capable the blanker
accordingly.

This is why the Collins and Drake rigs of the 60's and 70's used separate
receivers for generating noise blanking pulses. They were relatively "wide
open" at around 45 MHz.

Present-day receivers compromise by locating the blanker after the roofing
filter(s) but before the main IF filtering.

But they are a compromise . . .

73, George W5YR
Fairview, TX
w5yr at att.net
http://www.w5yr.com


----- Original Message ----- 
From: "Jay Kesterson" <k0gu at verinet.com>
To: <1000mp at mailman.qth.net>
Sent: Monday, May 17, 2004 7:50 AM
Subject: [1000mp] Roofing filter


> "Joe Subich, K4IK" wrote:
> >
> > It is not switchable.  One gives up FM and "wide" AM.
> >
> > 73,
> >
> >    ... Joe, K4IK
>
>    Previous discussions about a narrow roofing filter in the
> FT-1000MP indicated it would greatly reduce the
> effectiveness of the noise blanker. I would be interested to
> hear more comments on this subject.
>
> -- 
> 73, Jay  K0GU  DN70mq          k0gu at verinet.com
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