[160m] 160m Digest, Vol 56, Issue 1

[kd6nrp at earthlink.net]

Hi David:

Back in the mid-1980s a California company called Radio West sold a mediumwave (broadcast band) active receive antenna consisting of several ferrite rods glued end-to-end.

The unit had a deep null that was useful for nulling out interfering stations while DXing the crowded U.S. mediumwave band. I don't think it was very directional, however.

Regards,

Brian, KD6NRP


-----Original Message-----
>From: David Cutter <d.cutter at ntlworld.com>
>Sent: Aug 26, 2010 10:51 AM
>To: 160m at mailman.qth.net
>Subject: Re: [160m] 160m Digest, Vol 56, Issue 1
>
>I've seen 2 designs for ferrite rod rx antennas made in completely the 
>opposite style: one had several rods glued end to end with an LC tuned 
>circuit in the middle all mounted in a plastic water pipe for external use 
>and one in which all the rods are bundled together and mounted on a wood 
>base for indoor use.  I've often thought about making them to compare.  I 
>must try to locate those articles, but each claimed that it was the nulling 
>effect that gave the advantage, to point at a seriously offending station or 
>source of noise.
>
>David
>G3UNA
>
>
>>  I was thinking last night as i was listening to coast to coast on my
>> AM radio.
>>
>> The question is,  While i know for sure we could not use it for
>> transmitting,  But the ferrite bar antenna that is inside this radio,
>> How efficient are these anyway?  I know they are highly directional,
>> with very deep nulls.  But has anyone ever made one for use on 160 meters?
>>
>> And if so what did it perform like?
>>
>> The directionality would be nice. how about noise, or overall gain  etc?
>>
>> Joe WB9SBD
>> -- 
>>
>> The Original Rolling Ball Clock
>> Idle Tyme
>> Idle-Tyme.com
>> http://www.idle-tyme.com
>>
>>
>> ------------------------------>
>> Good thinking. The small rod antenna has an overall pattern much like a
>> small loop antenna. The rod length direction is like the axis of the small
>> loop antenna, and would be the direction of nulls.
>>
>> Unfortunately the are not highly directional, they are the opposite! The
>> pattern has very narrow very deep nulls, but in all other directions it 
>> has
>> strong response. This means the directivity is not good, only the nulls 
>> are
>> sharp and deep.
>>
>> It would be good for nulling noise or unwanted signals from a small 
>> specific
>> area, but not much good if noise comes from multiple directions.
>>
>> Efficiency is very low, very small fractions of one percent. This doesn't
>> matter much for receiving, but it does for transmitting!
>>
>> 73 Tom
>> 
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