Mark Zenier ) writes:
In article ,
Brian Hill wrote:

"Michael Black" wrote in message
...

"Brian Hill" ) writes:
I just bought these two off Ebay and was wondering if anybody has any
experience with these two radios. I bought em both for obvious collector
reasons. The R-530 has the Wadley loop circuit which I'm interested in.
And
I got the SW1 because it's one of the first micro portables with descent
performance and I collect Sony's. I would like to find the Original
Barlow
Wadley XCR-30 someday.

Look again, the Galaxy does not use a Wadley loop.

It uses a phase locked loop synthesizer to generate the first local
oscillator
signal every 500KHz (or is it 1MHz in the Galaxy?).

A Wadley loop, while providing the same overall effect, is a result of the
right mixing, adding and subtracting, in the signal chain.

What confuses people is that the design of the synthesizer in the Galaxy
uses a similar bit to the Wadley, putting the reference frequency through
a
multiplier that puts out signals at every harmonic of that reference. IN
the Wadley, that signal is used to generate the needed beat signals, in
the Galaxy that signal is compared to the local oscillator in a phase
detector
to lock the local oscillator.

Visually change the multiplier to a programmable divider chain, and in the
Galaxy you'd have a more recognizeable synthesizer. It just came before
programmable dividers were cost effective, just as the case with the
National HRO-500, so they went with the muliplier, though there is a
tradeoff in use and performance compared to a synthesizer with a
programmable
divider.

Change the mulitplier in the Wadley to a divider, and the thing won't work
^^^^^^^^^^
Minor quibble: comb generator (or something like that)

at
all.



Michael


Hum? I'm just going by what I read. Fred Ostermans book needs an update!
Where did you get your info? The tech manual? Thanks

There was a really good thread on the Wadley Loop in the
rec.radio.amateur.homebrew newsgroup several years back.

I've posted explanations (or what I hoped were decent explanations)
in the past to various newsgroups. Oddly, one of them landed on the
Wadley Loop page, http://www.qsl.net/vk3jeg/b_wadley.html
but whoever put it there had changed a word or two, so it looks like
I'm saying the HRO-500 used a Wadley loop, when I was correcting someone
who said it did.


The really cool feature was how the first oscillator was used to mix
both the incoming RF (to the frequency range of the 1 MHz wide first
IF), and (with another mixer) to tune one of the harmonics out of the
comb generator into the range of a narrow bandpass filter. This was
amplified and mixed with a crystal oscillator (in such a way that the
offset/drift of the first LO was inverted) and that was used as the
second LO to mix the first IF down to the second IF's frequency range.
So as long as the harmonic of the reference was in the range of the
synth's bandpass filter, the offset and drift of the first LO was
canceled.

How good is a FRG-7 with intermod, though?

That's the question. It adds an extra mixer stage in the signal chain
in order to get the "synthesizer". It is a neat arrangement, but just
a few years later, the same effect came from having a PLL synthesizer
out of the signal chain. Though as I write this, I do wonder if someone
looked at the Wadley loop and wondered how to get rid of that extra
mixer in the signal chain, and realized a bit of change would fix that.
Obviously there is vast similarity between the Wadley loop and the
synthesizer in the Galaxy and HRO-500, with that multiplier of the
reference (and yes, comb would fit better there), and the need to tune
the MHz knob to get a beat note.

Michael