Topband: High Z vs Low Z shunt feed tower

[k6se@juno.com]

Ford, N0OQW wrote:

"I measured the transformer with the autek.  It seems to be very low
insertion loss and doesn't get more than just warm after many minutes of
800 watts."
----------
If the transformer is getting warm at only 800 watts, that's lost power.
==========

"But, will it provide a better pattern or ERP?  That's the issue.  I am
certain I could figure out 50 different ways to get a match.  
----------
Assuming lossless components in either case (450 ohms or 50 ohms), the
pattern and ERP will be the same.
==========

Does it improve my SNR?"
----------
Anything you do to the feed system, good or bad, will not change the
receive S/N an iota.  There's no difference in S/N on a given antenna
whether it's 1% or 100% efficient (as long as you do not change the
antenna itself).

Some hams may think that the S/N will improve if you add radials.  Not
so.  Only the radiation efficiency of the antenna will improve.
==========

"I figure I could easily spend a weekend up and down the tower and drop a
few bucks in components."
----------
That's one advantage of going to a 50-ohm tap height -- much less to
climb to get to the attachment to the tower.  I particularly don't like
climbing very high, myself.
==========

"I am investigating whether anybody would "hear" any difference.  I have
a system that seems to work.  I could easily modify things and get them
to the point where I can't go back to as good as what I've got.  I am
nervous about messing with it.  I will if it makes the difference between
a QSO or not."
----------
You'll never know the answer to that unless you change the feed system. 
The only real way to know is to take a field strength reading (at a mile
or so away) before you make any changes, then another after altering the
feed.
----------
 
"At this point I am leaning towards Rauch's response--Splitting hairs..."
----------

Changing the feed would probably add less than a dB to your signal.  I
guess we'll never know for sure.

73, de Earl, K6SE



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