Are Walkman radios superhets?

[Cass Lewart]

I wonder if the walkman type AM/FM radios are superhets. I took one
apart and could not find any IF transformers. Same would apply to 400
MHz FRS band walkie talkies. I could not find a schematic.

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_/ Cass Lewart Voice (732) 264-9541 Fax (630) 566-0349/_/
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[CWatters]

Not really my field but...

They are sure to be superhet if not double superhet. They may not use wound
components in the IF filter see IF filter on this page...

http://www.rentcom.com/wpapers/telex/telex6.html


"Cass Lewart" <rlewart@shell.monmouth.com> wrote in message
news:bqu8mr$drf$1@news.monmouth.com...

I wonder if the walkman type AM/FM radios are superhets. I took one
apart and could not find any IF transformers. Same would apply to 400
MHz FRS band walkie talkies. I could not find a schematic.

--
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
_/ Cass Lewart Voice (732) 264-9541 Fax (630) 566-0349/_/
_/ e-mail: rlewart@monmouth.com _/_/_/_/_/_/_/_/_/_/_/_/_/
_/ N 40 deg 23' 41.9", W 74 deg 11' 29.7"/_/_/_/_/_/_/_/_/
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/

 

[Michael Black]

"CWatters" (colin.watters@pandoraBOX.be) writes:

Not really my field but...

They are sure to be superhet if not double superhet. They may not use wound
components in the IF filter see IF filter on this page...

http://www.rentcom.com/wpapers/telex/telex6.html


I've answered this thread elsewhere, months ago.

Certainly, those cheap FM only two button radios use a variant on the
Phillips TDA7000, ie a conversion to a very low IF frequency where
an active filter supplies the IF selectivity.

And it's slightly possible that some cheap AM radios use the later
variant on the old Plessey ZN414 (I think I got the prefix wrong)
TRF IC. Certainly, in the Phillips datasheet for the IC (I forget
the number offhand, something like a 7088) in those two button radios,
they show in one schematic circuitry for an AM section, and it's something
like those TRF ICs. Certainly, they must be used somewhere, since
they are being made.

I have no idea if such schemes are actually being used in "Walkmans"
though if they are, likely it's limited to the cheap ones.

I've opened up recent tiny cellphones, and hardly any of it is
recognizeable, let alone reusable. I suspect that's the case
in FRS radios. In the old 49MHz superhet walkie talkies, they
had fairly decent receivers; certainly they were the same basic
scheme used in a lot of low deviation FM receivers, dual conversion
with a wide ceramic filter at 10.7MHz and a ceramic filter at 455KHz.
I can't see them going to something inferior as they move up in frequency,
especially considering the FRS tend to be more expensive. It's just
that they use surface mount to make manufacturing cheap, and once
something becomes surface mount it's not nearly as identifiable
as those big green or orange filters of days gone by.

Michael

"Cass Lewart" <rlewart@shell.monmouth.com> wrote in message
news:bqu8mr$drf$1@news.monmouth.com...
I wonder if the walkman type AM/FM radios are superhets. I took one
apart and could not find any IF transformers. Same would apply to 400
MHz FRS band walkie talkies. I could not find a schematic.

--
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/
_/ Cass Lewart Voice (732) 264-9541 Fax (630) 566-0349/_/
_/ e-mail: rlewart@monmouth.com _/_/_/_/_/_/_/_/_/_/_/_/_/
_/ N 40 deg 23' 41.9", W 74 deg 11' 29.7"/_/_/_/_/_/_/_/_/
_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/_/