Topband: "Thinking out loud"

[Bill Cromwell]

Hi,

I wonder if you could cover the whole band or just the part that 
interest *you*. I have a radio now that uses an xtal filter with about a 
7 kHz bandwidth on the 20 meter band. Probably those filters can be made 
wider with perhaps less filtering action - tradeoffs ya know. The idea 
isn't new and it works!

Merry Christmas and...

73,

Bill  KU8H

On 12/22/2016 05:56 PM, K1FZ-Bruce wrote:
> Thanks Mirko and Matt,
>
>
> This is not on the market yet, but should do a lot for noise on 160 
> meters.
>
> Bet a tube transmitter had  naysayers. Need  a spark to transmit. hi.
> 73
> Bruce-k1fz
>
>
> On Thu, 22 Dec 2016 16:18:56 -0600, Matt Murphy  wrote:
>
>       This appears to be the 4O3A unit. I hadn't realized these 
> existed, so I'm
> glad you posted the question:
>
> http://www.4o3a.com/index.php/products/ham-radio-gear/crystal-front-end-unit/ 
>
>
> On Thu, Dec 22, 2016 at 3:47 PM, K1FZ-Bruce  wrote:
>
>>
>> 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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