[TowerTalk] Trap Resonance

[Peter Cattell]

Jim,

how did you measure the TH6 trap resonant frequencies?  I tried using a Dip
Meter. I wrapped 3 turns around the trap, 3-4 turns around the Dip Meter
coil using the 16-45MHz range, and got no dip.  I then wrapped about 30
turns around the trap ang got about a good dip at about 31MHz for the 10m
trap.  I suspect however that I was really measuring the effect of the 30
turns of wire interacting with the trap. 

I note also that the trap covers are DC connected to both the cold and hot
ends of the traps.  This surprised me as I thought the cover formed part of
the capacitance for the trap circuit as for my previous beam.  

All comments welcome!

Peter
=======================================

At 10:40 pm 11/08/97 -0700, you wrote:
>Hello Peter-
>
>I have a TH6DXX TOO.  I cleaned it up and tested the antenna with a GDO last
>summer.   The first trap from the boom on the driven element is 10 meters  I
>found it to be on 28.75,  the second trap from the boom is the 15 meters
>trap and I found it to be 21.200.   These measurements are + or - several
>KHZs.   The reflector is only the 15 traps and it was on the same frequency
>as the driven 15 meter trap.   The director is the tem meter trap and it was
>on the same frequency as the driven on ten.
>
>I hope that makes sence and it will help.   I also use a spectrum anylzer
>and a return loss bridge and it checked out good too.   Of course the swr
>bridge is also a good way to see if things are some what correct before
>installing it at the top.
>
>I tried pointing the director up leaving the reflector on the ground for
>some type of reading.   Then I put it on a 20 foot pipe and tied it to a
>fence post away from everything.  This was the best of readings.   When it
>was mounted at the 60 foot level it was a bit higher in freq but was basicly
>the same swr.
>
>73's jim
>
>
>
>
>
>
>
>
>
>At 02:13 PM 8/12/97 +1000, you wrote:
>>Gi'day from 'down under',
>>
>>I have been reading postings from this group with much interest for the
>>last 2 months.  This is my first post.  I bought a few weeks ago a Hy-Gain
>>TH6 DXX Thunderbird Yagi.  I have disassembled it, cleaned all overlapping
>>sections of tubing, coated them with Aluminox conductive paste and
>>reassembled it.  Prior to raising it on the tower, I would like to check
>>that all traps are OK.
>>
>>I intend to look for 0.0 DC resistance over all trap connections.  My
>>question is: 
>>
>>"what resonant frequencies should I look for using a GDO hooked onto the
>>hot end of the traps and should I disconnect the traps fromn the elements
>>when measuring the freguencies of resonance"?
>>
>>Also, is this the best way of ensuring the traps are OK?  Should I be doing
>>any other tests on the traps on the ground - e.g. using a noise bridge?
>>
>>Peter (VK4GPP)
>>Brisbane
>>Australia
>>
>>
>>
>>
>>--
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>>
>
>

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