Re: LF: A/G FREQS

[M0FMT <m0fmt@yahoo.co.uk>]

Hi Mal

 

Yes and AM has the same sort of transparency to co channel signals as SSB to a degree (same type of mode of course) where as FM captures the channel and cannot be over ridden unless the competing signal is about 3dB stronger. FM also seems to drop off very quickly with range especially if the audio modulation is not set to its optimum i.e with 6dB compresson (Pre emphasis, clipped, De emphasis, filtered). Further more this very narrow band FM IMHO is useless. And it is FM that we can thank for V/UHF channelisation it never used to be like that it was the availability of in the late 60s/70s of cheap Rice Boxes that turned it into an FM channalised wastland.

I think AM has a lot going for it and it amazes me that the Marine people opted for FM since they must have had advisers who were familiar with the days 2182. We try to keep AM going on TB and 4m around here but the FM seems to have hijacked 70.26 in the name of the RSGB.

 

73 es GL Pete M0FMT IO91UX

From: mal hamilton <g3kevmal@talktalk.net>
To: rsgb <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, 26 June 2012, 8:36
Subject: LF: A/G FREQS

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