K9AY Antenna - Remotely Variable Termination

[tracey gardner]

Hi Clifford

Fine on the comments on your solutions.

A friend of mine tried the lamp method but felt that the slow response 
of the bulb made it difficult to achieve the optimum null.
I think that the combination that I've got here produces a variation
between 250 ohms and 1200ohms.

73s Tracey

========================================================================= 

on 27 Jan 99, Clifford Buttschardt wrote...

>Good comments.  I just built a variable termination for another fellow who
>has the K9AY already performing.  I used an old fashioned RAYSISTOR,
>something the Raytheon sold many years ago.  A homemade termination was
>also built using a grain of wheat bulb coupled to a Radio Shack CdS cell
>with a drop of clear salad oil!  This worked even better as the ON
>resistance was much lower.  Both devices were shunted with a 1500 ohm
>resistor which produces a high resistance limit.  In the latter case, the
>variable termination is to be used with a Flag or Pennant antenna on 160
>meters.  Incandescent lamps appear better as they do not produce RF noise.
>Cliff Buttschardt  K7RR/W6HDO
>
>On Wed, 27 Jan 1999, tracey gardner wrote:
>
>> 
>> 
>> Hi All
>> 
>> Further to my last message on the K9AY, which Andre' kindly put
>> out for me.
>> 
>> I forgot to mention that I am using a remotely variable termination,
>> similar to Steve Byan's unit, on my K9AY.
>> 
>> However I subscribe to the KISS principle and the variable
>> termination that I'm using consists of a discrete LDR and LED 
>> combination in a bit of plastic tubing and not the Vactrol which
>> isn't available over here.
>> 
>> The remotely variable termination makes all the difference to the
>> K9AY as you can optimise the null on the offending station.
>> 
>> 
>> 73s Tracey G5VU
>> 
>> 
>