Ooooops! As a new subscriber to this group, I wasn't aware that a debate to
this effect had taken place!
I appreciate and value ALL the feedback that I have received. One gentleman
suggested a parallel radiator system (that I had been toying around with)
for better efficiency. I shall try that as well and compare results.
All I can say at this time, with real world tests (through crude and
backyard!), is that the trap at 14.5 Mhz produced MUCH better results than
at 13.5 Mhz. Someone wondered if the SWR and hence max power output was
different. In actual fact, the SWR and output was better when I had the trap
at 13.5. The reduced signal strength was noticeable both on RX and TX of the
local station around 4 miles away.
In fairness to Tom (again I have NO CLUE that this was a sensitive topic), I
found similar theory at L.B Cebik's site (To trap or not to Trap). LB has
been a friend and a GURU over the years and that is why I have started to
wonder if there was a "rule of thumb" difference as regards trap resonant
freq and operating freq.
I am also wondering about the different loading effects on the radiator. The
higher trap freq brings the 20m section closer to a full 1/4 wave at 20m,
but the 13.5 trap shortens this down to 14.4" I would imagine that the
longer radiator would naturally make the system more efficient. Incidentaly,
please note that the higher trap resoannt freq improved BOTH 20m and 40m
The final analysis is that I still find 20m down by about 10db over a
monoband 16.4" ground plane with the same radials. Need to regain at least
half of those dog biscuits to justify having this system up eh fellas ?!
Has anyone on the list actually dipped a decent commercial 20m trap? would
love to hear of the findings.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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