[RFI] VHF-AM radios
EDWARDS, EDDIE J
EDWARDS, EDDIE J" <email@example.com
Tue, 23 Jan 2001 15:33:30 -0600
Excellent Dale! I do remember hearing about slope detection, don't remember
where though. It works like a champ. I'm sure that's all we did on the old
multi-band rcvrs since the frequency display was analog and not accurate.
I'm listening to the NOAA stn right now in AM mode by tuning 9 to 10 kc
higher or lower. It's not perfect but it does work.
Thanks for jogging my old memory Dale. :^)
de ed -K0iL
> -----Original Message-----
> From: firstname.lastname@example.org [SMTP:email@example.com]
> Sent: Tuesday, 23 January, 2001 1:21 PM
> To: EDWARDS, EDDIE J; firstname.lastname@example.org
> Subject: RE: [RFI] VHF-AM radios
> I believe that the ham rigs which offer coverage of AM Aircraft Band
> receive, actually have a separate AM IF and detector system for that part
> of VHF. I suspect that the radio micro-P simply switches in the correct
> detector chain for whichever frequency range the user wants. Most modern
> rigs use "one-chip wonder" FM receiver strips after the front end (usually
> from Motorola or Philips), and there are a few equivalent chips for AM
> reception (Harris or Philips). However, I have seen the AM stuff done
> discretes in some sets, apparently because that was cheaper than a special
> Those of us who used to operate 2m AM (eons ago) know that it is possible
> to use a technique called "slope detection" to copy FM sigs with an AM
> receiver. This does require being able to CAREFULLY and SLOWLY tune the
> receiver so that you can locate the center of the IF on either side of the
> FM carrier (the "slope") where the changes in deviation "swing" (which are
> a phase change) produce a limited amount of amplitude change. I have no
> clue if the sets under discussion employ that technique, but they might.
> If so, then these could make good VHF line noise detectors, but you might
> want to work on some means to add a signal strength indicator. You might
> also keep in mind using a VHF multi-mode rig. Some of the newer ones
> ('706, '817, '847) offer AM operation on 6 and 2 meters; others, like my
> FT-290, offer SSB, but no AM. However, if the noise blanker is disabled,
> impulse noise comes through just fine. A real noise tracking advantage
> the FT-290 and the new FT-817: battery operation and a carry strap. If
> you have the FBA8 C cell case for the '290, it will go anywhere you can
> The '817 appears to have batteries self-contained, as did the old
> this?) IC-202.
> 73, Dale
> "EDWARDS, EDDIE J" <email@example.com>@contesting.com on 01/23/2001
> 10:08:34 AM
> Please respond to "EDWARDS, EDDIE J" <firstname.lastname@example.org>
> Sent by: email@example.com
> To: "'RFI'" <firstname.lastname@example.org>
> Subject: RE: [RFI] VHF-AM radios
> I have often wondered how those radios perform dual-mode rcv. I have one
> home that rcvs 110-180Mhz in one band --one mode. Seems like something I
> should know, but have never ran across this info.
> I tried it with my R7000 on my desk and the audio quality of the AM air
> xmissions in FM-narrow mode is very poor, and the NOAA xmission is
> unintelligible on AM. FM wide is also very bad.
> Anyone know this secret?
> de ed
> > -----Original Message-----
> > From: Kelly Boswell [SMTP:email@example.com]
> > ----- Original Message -----
> > From: "Pete Smith" <firstname.lastname@example.org>
> > To: <email@example.com>
> > There FM.
> > > Are the NOAA weather broadcasts AM or FM?
> > --
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