Thanks Mirko,
Very Good information. What is needed is to reduce noise more (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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