Topband: [PVRC] 2-element receiving arrays

[Mike Fatchett W0MU]

Meaning,

We do the best we can and there is no and there will never be a perfect 
solution.  All we can do is attempt to eliminate as many variables as 
possible.   My circle array  works better than all of the other things I 
have tried.  It is near fencing, close to a power line etc.  I don't 
have unlimited flat land in the middle of nowhere.  Not optimal but it 
is what I can do.

I think people get caught up in perfection.  Put up stuff and try it!  
You might be surprised.  What works for me might not be a good solution 
for you, etc.

W0MU

> On 3/30/2023 7:47 PM, Frank W3LPL wrote:
>> Hi Dave,
>>
>> Anyone who has experimented with a high impedance antenna such
>> as an end fed half wave has experienced the extreme environmental
>> influence on the feedpoint impedance of a high impedance feed.
>>
>> The required spacing to trees and buildings is very difficult to predict
>> with any confidence. The impedance of a high impedance element
>> -- and hence the amount of voltag if feeds into the preamp --
>> is heavily influenced by its immediate environment.
>>
>> If all of the high impedance verticals in an array do not produce the
>> same voltages from the signals received by the array, the pattern
>> of the array and especially its nulls are significantly degraded.
>>
>> 73
>> Frank
>> W3LPL
>>
>
> Allow me to quibble a little with this analogy.  The 1/2 wave dipole
> is a tuned circuit with a Q in the low double digits.  This leverages
> any capacitance change.  The voltage probe antenna is just a plain
> non-resonant capacitance.  Still sensitive to nearby conductors, but
> probably not to the extent of the EFHW antenna.  I would be more
> worried about circuit capacitance in the hi-Z preamp.  In general,
> the capacitance of JFET's (or any FET's) is very loosely specified.
> The transconductance is also very loosely specified, and can
> act as a modulator of input capacitance due to the Miller effect.
> As if that isn't bad enough, the DXE preamp comes with tank circuits
> that you can optionally activate with jumpers.  This adds another
> random variable to the input capacitance.  Ideally, there would be
> a "factory select" padding capacitor to make the capacitance the
> same on all copies of the preamp.  AFAIK, no preamps have this
> feature. And finally, the CB whip moves around wildly in the wind.
> If there are nearby objects, this adds a time variability.
>
> 73
> Rick N6RK
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