[Premium-Rx] Antenna question

[Jack Smith]

A couple of observations on nulling medium wave signals with a loop 
antenna.

1) Nearby  radiating objects can degrade the null or shift the null 
bearing or both. My loop test bed (with both Pixel and Wellbrook loops 
on a common cross arm) is perhaps 50 or 60 feet from my 100 ft tower 
with transmitting antennas. Above 1 MHz or so, the tower re-radiates 
enough medium wave band signal to materially degrade the nulls on all 
the test loops.

2) Skywave signals may or may not be nulled and if they can be nulled 
the bearings may be different than would be the case for a ground wave 
signal from the same location. This is a matter of physics and not loop 
construction.

Jack K8ZOA

On 11/13/2012 2:06 PM, Al Klase wrote:
> Mac,
>
> I thinkj you're going to find that, on the broadcast band,  a simple
> tuned loop will out perform all but the most sophisticated (and large)
> wire antennas.
>
> Something like this will work wonders:
> http://www.njarc.ar88.net/LOOP/Easy_loop.pdf
>
> Here in Jersey City, I can tune WSB in Atlanta on 750 KHz, then null WSB
> by turning the antenna, and hear YVKS, Caracas, VE on the same freq.
> They identify as "ere ce ere" RCR , Radio Caracas Radio.
>
> More related BCB DX info here: http://www.njarc.ar88.net/contest.html
>
> Al
>
> On 11/13/2012 12:35 AM, Mac McCullough wrote:
>> Readers:  several things prompt this question, foremost I am sorta stuck
>> here at home with limited mobility for a bit longer.. But I am wanting to
>> improve my RECEIVER listening ability.. I have ample Premium Rx's  but
>> honestly I am never satisfied with my antenna efforts when listening beyond
>> HAM freq's where I typically do have good or great antenna selections to
>> choose from..
>>
>>
>>
>> But as an example once I want to listen to the AM Broadcast Band my antenna
>> selection is lame, I have a 100' long wire up and it comes in and I just get
>> it stabbed into a RX antenna port via some mish/mash of adaptors or such..
>> never sure or even trying for an IMPEDANCE match of any sorts and I know I
>> am missing utilizing the RX best performance for lack of a good antenna, I
>> am sure my noise floor is considerable higher ...  Do most of you try for a
>> good impedance match or what is your thinking here please ... while most
>> modern Premium Rx use a 50 ohm input, the R-390 wants 125 or some such
>> match..  so you can see I have several demands or at least needs I think
>> deserve more attention that what I am offering at the present ..
>>
>>
>>
>> Thanks for all possible help and ideas ..  mac/mc  w5mc
>>
>>
>>
>>
>>
>>
>>
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