John Byrns wrote:

3. TRF receivers have been mentioned, and everyone seems to assume
that a TRF receiver would consist of cascaded single tuned
resonators with RF amplifier stages between. There is no reason why
double tuned circuits, similar to those used in the IF transformers
of a superhetrodyne can't be used in a TRF receiver, with all the
selectivity/bandwidth benefits that brings to the party. For
examples see the Western Electric No. 10A receiver, the J.W. Miller
TRF receiver, the early Altec AM receiver, as well as others.

I did a cursory check on the Internet, but did not yet find any
schematics for the mentioned receivers. Are they online somewhere?
Anyone?

I also found the following article from John posted back in 2000,
where he talks about the double tuned TRFs, such as WE-10A, J.W.
Miller, Collins (which I assume is the same one Volker Tonn
mentioned today), Meissner, and the Weeden (the last of which John
noted to be the best designed of all of them):

http://groups.google.com/groups?selm...&output=gplain

Unfortunately the URLs to the TRF schematics at John's site are not
working.

John, how exactly do these double tuned circuits work in TRF circuits
compared to using single tuned resonators, as depicted on slide 7 of:

http://www.technology.niagarac.on.ca...531unit6rx.ppt

John, I also recall you mentioning a while back about "modernizing"
one of these TRF receivers. What is the current state of your research
on these circuit designs? Have you advanced to the point that a
detailed schematic is right around the corner?

Thanks for posting your thoughts.

Jon Noring