To: | "[email protected]" <[email protected]> |
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Subject: | Re: LF: A/G FREQS |
From: | M0FMT <[email protected]> |
Date: | Tue, 26 Jun 2012 17:42:37 +0100 (BST) |
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Well Graham when I were a Jate we only had one xtal and a QQV02-6 on 432.00 amplitude modulated on the plate in the good old days. After all its just the product of mixing two frequencies 432 with audio in a nonlinear device like a Class C amp works from almost DC to light!. Nowerdays I guess you would PWM the carrier on the PA gate/ base producing the same effect and using considerably less power over all. Class E an all. 73 es GL Pete M0FMT IO91UX From: Graham <[email protected]> To: [email protected] Sent: Tuesday, 26 June 2012, 17:09 Subject: Re: LF: A/G FREQS Steady on Mal ! this is getting technical
!"
Your right , FM has a cut off point ,
where demodulation fails and also a capture
effect , where the stronger of 2 signals will
acquire and hold the demodulator ..always
fun on 2 mtrs when a mobile suddenly
takes the channel
Am has no cut off point , but gradual
degradation until the recovered audio is no longer
usable ......eg, mcw would readable much
lower than AM speech
I think much over 250/300 MHz its
actually not possible to produce AM , could
be wrong , but there is a limit , may
be by high level modulation falls over , dont
see why could not be via transverting
.......
G..
As stated Air/Ground vhf/uhf is AM and
simplex working. I have also noticed a well modulated AM transmitter
is more potent than a FM transmitter when working at max range. On AM the RX
bandwidth can be opened up to receive several stations simultaneously then
select the one of interest by closing down the selectivity, the same applies on
CW. On FM if you tried this the transmission would fall into a black
hole, in other words the FM rx has to be tailored to the
exact bandwidth of the transmission (same deviation value)
g3kev
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