The loop I built decades ago is made from 2 turns of 1" CATV hardline of 40"
diameter which is remotely tuned by a set of BCB diodes and feeds PP U-310
Fets. There has never been a problem of BCB or any other intermod even when
doing BCB DXing.
Some loops have such poor Q that they are wide open to interference
problems. The hardline I chose has the lowest C per foot and therefore the
highest Q with the resultant narrow bandwidth and need to retune for even a
small QSY. The preamp is very helpful and is not run at high gain, just
enough to give a comfortable signal level.
Preamps can be unstable at any frequency and need attention to layout
detail, bypassing, properly sized inductors, etc.
Carl
KM1H
----- Original Message -----
From: "Guy Olinger K2AV" <olinger@bellsouth.net>
To: "rick darwicki" <n6pe@yahoo.com>
Cc: <topband@contesting.com>
Sent: Wednesday, September 14, 2011 7:20 PM
Subject: Re: Topband: BCB interference on 160
> The problem would be that you need to trap out the BC signals BEFORE they
> reach the tuning diodes. In the good ole days with signals that were no
> more powerful than now, a small antenna, a coil, capacitor, and a diode
> would produce enough rectified audio to drive a pair of headsets WITHOUT
> any
> amplification whatsoever. So there is plenty of RF to intermodulate two BC
> signals on a tuning diode, even if the IM is 60 or 70 dB down. 73, Guy.
>
> On Tue, Sep 13, 2011 at 10:42 PM, rick darwicki <n6pe@yahoo.com> wrote:
>
>> Hi all,
>>
>> I recently built a sheilded RX loop for 160 per N6RKs Contest Jouranal
>> artical. It is diode tuned and covers about 1.5-4 mhz. I am hearing two
>> AM
>> radio stations on 1830 khz.
>> They are 640 and 1190 combined. 640 is a 50KW station about 12 miles east
>> and 1190 runs about 1.5 kw at night.
>>
>> The anetnna is all sealed up and on the roof. I would like to cure the
>> problem without changing to back to back tuning diodes.
>>
>> I'm thinking a series trap tuned to 1190 or 640 or both. Maybe a high
>> pass
>> filter.
>>
>> Any suggestions? I can built it, I don't want to spent $200 for the W3s
>> highpass hi hi
>>
>>
>> Thanks,
>>
>> Rick, N6PE
>>
>> =============================================================================
>> If I agreed with you we'd both be wrong.
>> _______________________________________________
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
>>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
>
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_______________________________________________
UR RST IS ... ... ..9 QSB QSB - hw? BK
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