[Milsurplus] Radio pic and early FM

[Nick England]

Well with a limiter and discriminator as FM receiver, you do indeed get
capture. The weaker signal gets limited out. Very common phenomenon on my
car radio where I get the station east of me or the one west, but never
both at the same time.

This is a reasonable article
https://en.m.wikipedia.org/wiki/Capture_effect



Nick England K4NYW
www.navy-radio.com


On Sat, Apr 19, 2025 at 4:47 PM Mike Feher <n4fs at eozinc.com> wrote:

> I agree, Kurt. I cannot see that being the reason for the military not
> using it back then. I got my ticket in '63 and started on 2M FM around '66.
> Used some modified GE units first then went solid state. Never experienced
> any so called "captured" effect.  73 - Mike
>
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell NJ 07731
> 908-902-3831
>
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net <
> milsurplus-bounces at mailman.qth.net> On Behalf Of Facility 406
> Sent: Saturday, April 19, 2025 3:37 PM
> To: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] Radio pic and early FM
>
> > The aviation industry deliberately passed on FM because to the
> > "capture effect."  An FM set, stuck on transmit, can block an entire
> channel.
> > This is bad news when your up in the air covering a large area.  On AM
> > you at least have a chance of hearing another weaker station.
>
> I've heard this all my life.
>
> And, living in Nevada, where stations are spread out, it's barely a thing.
>
> My personal observations, across 2+ decades, many FM
> receivers/transceivers, it works like AM.  Hear one, hear two, or more,
> but, also like AM, when closer to a stronger one, the stronger seems to
> take over.
>
> I can personally attest, for the FM broadcast band, 2m, and 440 MHz, there
> is little to no capture affect, just one station stronger than the other,
> and I observe it several times per week.
>
> I also monitor airband comms, almost daily.  One can hear one, two, three,
> with varying levels of interference to each other, to completely blocking.
> So, in this sense, AM will also "capture".
>
> AM, FM, they work the same, strongest "captures", modulation doesn't
> matter.
>
> Perhaps the "capture" thing was based on a particular model receiver,
> under certain conditions, and the notion stuck?
>
> I tune AM/FM just the same, reception is just the same, and being in a
> sparse/rural area, it's a good thing, as I often listen to both AM and FM
> in the boonies, and on the fringe of reception.
>
> Kurt
>
>
>
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