Thanks Mirko,
Very Good information. What is needed is to reduce noise lower than signals.
73
Bruce-k1fz
On Thu, 22 Dec 2016 22:36:30 +0100, S57AD wrote:
As far as I recall, Inrad sells front-end xtal filters. Some 25
years ago
when I lived in Belgrade, at YU1EXY we had two six-pole filters for SSB
part of 40M band but I can't recall and difference with or without those
filters. Beside those two xtal filters we used 8 pole Cohn LC filter with
4-gang variable capacitor and with very step curve (I think it was 600 or
800 Hz at -6 dB), which drastically reduced noise and QRM. We could hear
3rd or even 4th layer of callers in 40m pile-ups.
As for xtal front end filters, I think 4O3A produces such a filters to be
used at in-band stations, but didn't have chance to try & use them...
73, Mirko, S57AD
2016-12-22 21:57 GMT+01:00 K1FZ-Bruce :
Tim,
My single crystal was in the 1950's.
A crystal lattice could take in much of the 160 meter band and be
pratical.
Thanks for your input.
73
Bruce
On Thu, 22 Dec 2016 15:49:12 -0500, Tim Shoppa wrote:
Bruce - It has long been rumored that the big EU multi-multis have
a crystal filter at their run frequency receivers. e.g. if they are running
on 7003.4, they have a crystal filter in front of their receiver for
7003.4. have never observed that in my visits but maybe in decades past,
when receivers had less damage range, it would've made sense. Also a good
reason to put up a fight for ownership of YOUR run frequency HI HI
I believe EMRFD has a schematic for a single-frequency receiver, maybe
not exactly like you described but similar in principle. Let me see if I
can dig it up.
Tim N3QE
On Thu, Dec 22, 2016 at 3:41 PM, K1FZ-Bruce wrote:
We know that limiting the noise pick up from more directions of an antenna
we can usually hear better. We also know if we limit the noise from a
receiver IF we can hear less noise, and better yet, if we
have a roofing filter earlier in the receiver we can eliminate even more
noise in relationship to the wanted signals.
What if we take it a step further, could we limit the band-with of the
antenna signal with a crystal lattice for 160 meters before the receiver.
Years ago I played around with a single crystal at the input of an old
tube type receiver. It was remarkable what I could hear on 40 meters,
on what seemed to be one frequency.
73
Bruce-k1fz
http://www.qsl.net/k1fz/beverage_antenna.html
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