[TowerTalk] log periodic choice

jim Jarvis jimjarvis at optonline.net
Sat Sep 13 12:27:35 EDT 2008


My 3 el steppIR took less than 15 seconds to go from 14.000 to 29.000.

I used it in a fully automated station,  using "point & click" on my  
bandmap, to
effect freq. changes during contests.   It was more like 5 seconds to  
go from
1kw out on 20 to 1kw out on 15m.   Barely enough time to take a sip  
of coffee,
and perfectly acceptable for a mult station in a contest situation.

It took the amp and transceiver about 3 seconds to get settled on the  
new
freq.   So the net difference between using my T8 and my 3 el SteppIR  
was
...  less than a sip of coffee.   nada.

HOWEVER, there are agile frequency hopping modes which require the
ability to implement wide changes in frequency within milliseconds.    
The LPDA
is more appropriate for those (non-amateur) applications.

Perhaps the greatest difference between the two antennas which I  
observed was
cross-mod on 15m in my 756pro due to front end overload from sw  
broadcast just
about 21,450.    They were more than 40dB louder than my signals of  
interest.
You could both HEAR the intermod, and see the bandscope baseline move  
with
the sw stations, 500KHz above.

Both the T8 and the SteppIR are good antennas, from good companies.
Both will do well. It's a question of attributes and price.

Someone asked me about the XR5, offline.   I have no direct  
experience with this
antenna.   From the specs, it MAY equal the measured performance of  
the T8, at twice the
price.   My only F12 experience comes from C31XR's, which we could  
never make
work on 15 meters with their single feedline system.   Separate feeds  
were needed.

N2EA


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