Topband: Amplifier Help

[GEORGE WALLNER]

On Wed, 17 Feb 2010 20:54:15 -0800
  "Richard (Rick) Karlquist" <richard at karlquist.com> 
wrote:
> 
> 
> GEORGE WALLNER wrote:
>> 
>> 
>> 
>>   Niko Cimbur <ac6dd at yahoo.com> wrote:
>>> Can something like this be easily done?  
>>> I am not familiar with the two 750W amps they have, but 
>>> Would it be possible to build a 4 square and feed each 
>>> element with its own amplifier and switched phase delay? 
>>> 
>> 
>> Niko,
>> 
>> I have done this with a two element array and it worked 
>> great. Phasing control is much easier at low power 
>>levels, 
>> i.e. ahead of the amplifiers. You have to ensure that 
>>each 
>> antenna is matched properly. (I used LC matching 
>> circuits.) Driving a 4SQ is more complex but should be 
>> possible.
>> 
>> George, AA7JV
> 
> How did you determine it worked great?  In most two 
>element
> arrays the impedance of the rear element is virtually a
> short circuit
> Rick Karlquist

Rick,

The elements were 100 m long V beams that I used on 80 and 
40 meters. Each element had its dedicated auto tuner (and 
ballun). (This was when I was in AZ and had the space). I 
had two SG-500 500 W amps. The elements were in an 
end-fire configuration about 40 meters apart and the 
tuners had no problem matching them. I used a remote 
receiver with a small dipole to find the optimum phasing 
angle. Also, on 40 the antenna worked much better than my 
2 el Yagi!

73,

George, AA7JV



TKS,

George, AA7JV