Michael Black schrieb:

Early double conversion receivers would have their IF in the 2MHz or so
range.

As for an example, all the Grundig Satellits from the 208 up to the 3400
(the last drum tuner model) used a combo of 1.85 MHz 1st IF and 460 kHz
2nd IF; this combo supposedly only generates a very small number of
birdies on SW. BTW the lowest SW range (2...3 MHz or somesuch) usually
was single conversion there.

And there was a whole other design of double conversion receivers that were
common at one time. These were in effect a single conversion receiver
that covered a fixed range of 500KHz or so. The exact turning range varied
with receiver, but it was usually in the low MHz range. In order to
get other bands, a crystal controlled converter was placed ahead of this
receiver, and you'd need another crystal for each band you wanted to tune.

A number of Drake receivers come to mind here, but also several (usually
pocket-sized) dual conversion receivers with crystals for the broadcast
bands built-in (particularly Sony models with a 1st IF of 10.7 MHz -
ICF-7600A, ICF-7601, ICF-SW20/22).

It's only in the past twenty to thirty or so years that upconversion to a
frequency above 30MHz became common, especially for hobby receivers.

That's about right, the first comsumer-level 55.845 MHz designs are from
the early 80s (Grundig Satellit 600, Sony ICF-7600D/ICF-2002). IFs that
high weren't practical before mass-production PLL circuitry came along,
a simple matter of frequency stability. (Given the same stability in
ppm, an oscillator on 1.85 MHz +/- 460 kHz or 10.7 MHz +/- 455 kHz will
be much less drifty than the same part on 55.845 MHz +/- 455 kHz. With a
PLL, this pretty much becomes a non-issue, but you get no small amount
of phase noise in return, which can frequently be observed with PLL rigs
from the '80s or with inexpensive PLL receivers even today.)

Stephan
--
Meine Andere Seite: http://stephan.win31.de/
PC#6: i440BX, 1xP3-500E, 512 MiB, 18+80 GB, R9k AGP 64 MiB, 110W
This is a SCSI-inside, Legacy-plus, TCPA-free computer
Mail to From: not read, see homepg. | Real gelesene Mailadr. s. Homep.

PS:

High 1st IFs like 55.845 MHz aren't quite uncritical, particularly with
very compact receivers - you easily get leakage around the 1st IF
crystal filter. You can observe this very nicely with Sony's ICF-SW7600
(-910 kHz rejection ~20 dB) or ICF-SW7600G/GR (~30-40 dB rejection). It
would be interesting to know the performance of the little ICF-SW07 in
this regard.

Stephan
--
Meine Andere Seite: http://stephan.win31.de/
PC#6: i440BX, 1xP3-500E, 512 MiB, 18+80 GB, R9k AGP 64 MiB, 110W
This is a SCSI-inside, Legacy-plus, TCPA-free computer
Mail to From: not read, see homepg. | Real gelesene Mailadr. s. Homep.

I was disappointed in the strong images in my FP200. Then I realized that
should there be interference on the desired frequency, the image just might be
in the clear for solid listening. G

Bill, K5BY

High 1st IFs like 55.845 MHz aren't quite uncritical, particularly with
very compact receivers

That's high?

My radio's first IF is 240.1 MHZ.

you easily get leakage around the 1st IF
crystal filter.

Good information. I didn't know that before.

And just the other year or so, I didn't know anything about IF frequencies or
radio image frequencies.

I still don't know much about them.