I got the impression that carrier has only appeared recently - withn the
last couple of months anyway, but my memory is probably fading with age
!
I spotted it since It was sitting only a few 10s of Hz from where Marco
was transmitting his low power tests. The interferer caused no problems
but did depress the AGC of the receiver somewhat in the 300 Hz bandwidth
filter.
On this subject, does anyone know of a low-cost source of 455 kHz
(series resonance) crystals. I want to make up a ladder filter for the
RA1792 with a much narrower bandwidth than the 300 Hz mechanical filter
included.
I've made a ladder filter at a centre frequency of 32765.5 Hz using
watch crystals, this has a bandwidth of 1.5 Hz but this would need a
down followed by up conversion to include within the receiver. A
crystal controlled LO capable of being pulled over the 10 Hz step size
would allow this filter to be built into the Rx, and would not need a
terribly stable conversion (provided it stayed within the bandwidth of
the ladder filter) as the drift of this oscillator would cancel out the
down followed by upconversion to 455 kHz.
Just a thought, but a ladder filter at 455 would be a lot easier.
Andy G4JNT
----------
From: Peter Dodd[SMTP:[email protected]]
Reply To: [email protected]
Sent: 2000-04-24 23:21
To: [email protected]
Subject: Re: LF: Carrier on 137.7446
Andy Talbot said
> There has been a strong carrier on 137.7446 kHz for at least a week.
No
> modulation and strength doesn't seem to vary.
> Can anyone else hear this ?
Yes, I can. It is so consistant (ever since we were allocated the
band) that I use it as frequency check marker when using Spectran or
Gram. It is clearly audible so I use it to check my receiver/antenna
system on audio CW as well. I understand that the signal originates
in France but I can't remember where I got this information.
--
Regards, Peter, G3LDO
<[email protected]>
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