yes, interestingly, there was an article in 73 magazine IIRC some years
back which described how to retroactively add IF shift to some older radio
receiver(s) using only a handful of parts,

Sounds like a worthy article, and a VERY worthy project. Is there somewhere I
could find this article online (or a similar project for retro-fitting IF
shifting to older receivers)?
Linus

GrtPmpkin32 ) writes:
yes, interestingly, there was an article in 73 magazine IIRC some years
back which described how to retroactively add IF shift to some older radio
receiver(s) using only a handful of parts,

Sounds like a worthy article, and a VERY worthy project. Is there somewhere I
could find this article online (or a similar project for retro-fitting IF
shifting to older receivers)?
Linus

Assuming the same issue had an article about adding an FM detector to
old shortwave receivers, I don't think the "IF shift" article is
worth tracking down.

Unless the description was horrible, the thing made no sense. My recollection
is that he put a varicap across an IF transformer, and called that IF shift.
Tha author showed no understanding of what IF shift was.

Michael

I'll try to find the cite to the 73 article, it is in my articles files
IIRC ;-) Can't be that complicated*, but whether it will work well with
all older radio receiver designs? Should be available via interlibrary
loan, or I can mail you a photocopy if you can't find or get it locally?

from google,
http://www.universal-radio.com/catal...hf/3450if.html
another reference to the 73 article,
http://lists.contesting.com/archives.../msg00290.html

grins bobm

*Since my Drake R4B has IF shift, in a tube/transistor hybrid, it can't be
that complicated to have IF shift in your radios ;-) ;-)
--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************

but whether it will work well with
all older radio receiver designs?

I guess I should have been a little less vague. I wouldn't want to add an IF
shift function to a tube model, I just thought it would be neat to try to
install such a function on a more modern radio which didn't have that feature.

Should be available via interlibrary
loan, or I can mail you a photocopy if you can't find or get it locally?


I will look around, starting from the leads you provided. If you do find a
copy, let me know. I'll pay for the trouble! :-)
Linus

yes, I found the brief article and the cite is 73 Amateur Radio Magazine,
August 1989, p.53, "IF Shift, Cheap - Easy IF Shift Add-on to your Older
Rig" by Terry F. Staudt, LPE, W0WUZ (LPE is licensed professional
engineer, IIRC?). He reviewed a number of 1970s upgraded receivers (A, S,
or Mk II versions ;-), and discovered how they did IF shift or passband
tuning in those updated models. The modification uses a varicap Motorola
MV 1872 and a pot and trimmer capacitor to vary the first IF transformer
frequency. He added it to a Galaxy V mk II transceiver, noting "the
circuit works wonders". You do have to make two adjustments to the
modified IF transformer to preserve selectivity etc., which he describes
briefly ;-)

If you can't find the article locally, let me know, email me directly with
your address to and I'll mail you a photocopy.

Drake IF tuning, IIRC, the R4C had an odd "feature" (aka bug ;-) in
that it didn't provide IF or passband tuning in all modes, as the earlier
Drake R4B did, although you could modify the R4C to do so (and other
mods too).

I probably shouldn't note that I found another 73 article in my search
that discusses how crystal filters could be built to provide any desired
CW or SSB bandwidth (though you might have to grind a crystal or two to
get precisely the bandwidth you want ;-) ;-)

grins ;-) bobm

--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************

(Bob Monaghan) wrote in message ...
yes, I found the brief article and the cite is 73 Amateur Radio Magazine,
August 1989, p.53, "IF Shift, Cheap - Easy IF Shift Add-on to your Older
Rig" by Terry F. Staudt, LPE, W0WUZ (LPE is licensed professional
engineer, IIRC?). He reviewed a number of 1970s upgraded receivers (A, S,
or Mk II versions ;-), and discovered how they did IF shift or passband
tuning in those updated models. The modification uses a varicap Motorola
MV 1872 and a pot and trimmer capacitor to vary the first IF transformer
frequency. He added it to a Galaxy V mk II transceiver, noting "the
circuit works wonders". You do have to make two adjustments to the
modified IF transformer to preserve selectivity etc., which he describes
briefly ;-)

If you can't find the article locally, let me know, email me directly with
your address to and I'll mail you a photocopy.

Drake IF tuning, IIRC, the R4C had an odd "feature" (aka bug ;-) in
that it didn't provide IF or passband tuning in all modes, as the earlier
Drake R4B did, although you could modify the R4C to do so (and other
mods too).

I probably shouldn't note that I found another 73 article in my search
that discusses how crystal filters could be built to provide any desired
CW or SSB bandwidth (though you might have to grind a crystal or two to
get precisely the bandwidth you want ;-) ;-)

grins ;-) bobm

Thanks for digging that up, it saves me looking for the issue that's
somewhere in a box.

Then, as I remembered and had intended to write the magazine at the time,
it's not IF shift. At the very most it's a tuneable peak within the
passband of the receiver.

He's tuning a single tuned circuit. That IF transformer will not provide
much selectivity, more important won't provide good skirt selectivity.
One tuned circuit won't do that, even if the IF frequency was low enough,
he'd need to be tuning all the tuned circuits in the IF strip. And given
that there is a crystal filter, and in the example in the HF range, the
IF transformers cannot supply anything narrower than the crystal filter.

He's not adjusting the crystal filter so the unwanted signal falls out
of the passband. The crystal filter supplies the ultimate selectivity.
So the good shape factor of the filter is not part of the "IF shift";
he is only shifting a far inferior selective element through the
passband of that crystal filter.


The article can provide no solution to "easy" IF shift.

Michael

Hi Michael,

you may well be right, though there weren't any followup complaints or
correction IIRC on the article. With 73 magazine in bankruptcy court now,
it is too late for you to publish a correction ;-)

I don't think the idea was to replace or supplant the crystal filter skirt
selectivity with IF shift, or to change or shift the crystal passband.

Since some radio receivers only have one IF stage and one IF transformer,
as an example, shifting its frequency would be shifting the entire IF ;-)

Then again, some of the 455 Khz IFs use murata style resonators which are
at least as good and selective as some quartz crystal filters (so I'm
told, anyway ;-) In such a case, it would seem possible that detuning the
first IF transformer so an interfering signal is above or below the main
IF passband and out on those many dB down skirts, while leaving the
desired signal within the IF passband, with resonator skirts or subsequent
crystal filtering etc. providing the selectivity, as usual, could work?

Again, I can't reject the idea out of hand, for all radios or setups. When
an LPE (licensed professional engineer) tells me he has reviewed many
example cases and studied how IF shifting works, it carries more weight
than some of the stuff I see on and off-line ;-) ;-) At least the cost of
the experiment is low (~$5?), so it may be worth testing for some
experimenters?

regards bobm


--
************************************************** *********************
* Robert Monaghan POB 752182 Southern Methodist Univ. Dallas Tx 75275 *
********************Standard Disclaimers Apply*************************

(Bob Monaghan) wrote in message ...
I'll try to find the cite to the 73 article, it is in my articles files
IIRC ;-) Can't be that complicated*, but whether it will work well with
all older radio receiver designs? Should be available via interlibrary
loan, or I can mail you a photocopy if you can't find or get it locally?

[stuff deleted]
grins bobm

*Since my Drake R4B has IF shift, in a tube/transistor hybrid, it can't be
that complicated to have IF shift in your radios ;-) ;-)

But there's a world of difference between something built from the ground
up, and trying to modify an existing radio.

The basic concept is tuning the receiver so the unwanted signal is out
of the IF passband. Technically you could do it manually, and indeed the
concept existed before receivers had it as a feature. For an AM
signal, it is simply a matter of mistuning the receiver; people doing
this without thinking of the process. But once you "mistune" the
receiver so the unwanted signal is knocked out, an SSB or CW signal will
not be tuned properly. You have to adjust the BFO so it beats the wanted
signal down to it's proper frequency. Imagine tuning the receiver up
1KHz, what was a 1KHz beatnote before now becomes a 2KHz beatnote, so
you've got to set the BFO so it's again a 1KHz beatnote.

Go back enough decades, and the BFO was tuneable, so one could play around
with this. But once BFOs became crystal controlled, it wasn't possible and
even with a tuneable BFO the technique can be cumbersome.

I seem to recall that one of the early Collins SSB receivers had it,
and did it simply by having a control that tuned both the main tuning a
bit and the BFO frequency. But that requires a tuneable BFO and an analog
main tuning.

One, or some, of the Drake receivers actually tuned the filter. This
was possible because those receivers used an LC-tuned filter at 50KHz,
and so unlike a crystal filter, one could add a front-panel control
to tune that filter.

But most applications of IF shift require some kind of conversion stage,
either in the signal chain or outside it, in order to use the BFO as
both the BFO and a control to shift the IF passband.

The Drake R4-C (I couldn't easily dig up a block diagram for the "B")
has three IF frequencies, one at 5.645MHz (a somewhat wide crystal
fitler), one at 6.695MHz (a mode-specific crystal filter there)
and the third at 50KHz (an LC filter).


A B
-----5.645MHz---Mixer---5.695MHz---Mixer---50KHz---Product
filter | filter | detector
| | |
| fixed |
| osc |
| ---------------------------------|
variable
50KHz
oscillator

So as the oscillator signal into Mixer A is varied, it tunes the
rest of the receiver through the passband of that 5.645MHz filter.
But, since that oscillator also feeds the product detector, the
beat note remains constant.

One can get away without so many conversions in the signal chain,
but it still requires mixers. The Kenwood TS-820, for instance,
is single conversion. But the BFO signal is mixed with the local
oscillator signal (and filtered carefully) before going to the
mixer between the antenna and the IF stage. So again, as
the BFO is varied, the filter is moved but not the beat note.

There is no simple way to add IF shift to a receiver. At the very least
it requires bringing the IF out, and passing it through some stages
of mixers and a filter, and then feeding it back, into the receiver.
I've seen such articles, and it risks degrading the receiver, if you
don't use the right conversion frequencies or good mixers.

Or you modify the whole local oscillator chain, so it works like
the Kenwood above.

Neither is an easy step.

Like I said, my recollection of that 73 article was that it was
nonsense. I'm sure it simply added a varicap to an IF transformer
in the existing receiver, as if tuning one LC circuit would allow
for tuning the whole IF strip. Even if I'm misremembering, or
missed the explanation (as I said, the article did not give a good
indication that the author understood IF shift), merely making an
oscillator variable does not make for IF shift.

Michael