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[TowerTalk] CL-35???

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Subject: [TowerTalk] CL-35???
From: (Dennis Schaefer)
Date: Thu, 11 Oct 2001 23:59:23 -0500
Thanks for all the help with my poorly performing CL-33.   I received
several good suggestions and considered them all, including more than one
that said "get a Bencher or Force 12".   

I decided I should define my expectations.    I want an antenna that will
allow me to work the Dxpeditions on the first day or so instead of waiting
until the pileups thin out!   I would like to be competitive with other
small stations in contests,  not limited to search and pounce completely.
I'm not particularly interested in the WARC bands.  The home system needs
to be  easy to maintain, because several of us are also building  a contest
station on a hilltop at an old AT&T microwave site we bought.     


1.  Buy a Bencher or Force 12 antenna.    Great antennas but  it's too soon
after the last round of ice storms to do that - maybe later.        

2.  Monobanders.    Labor intensive - avoiding interaction/loss of gain
requires wide separation/ multiple towers, or side/ ring rotators, etc.
Will get plenty of this fun at the club contest station.  

3.  Modify the present antenna.   One recurring suggestion  was to replace
the trapped reflector on the CL-33 with three full-size reflector elements.
   I liked this approach because the Mosley, while performance-challenged,
is physically strong and survived the ice.     

Modifying the present antenna seems like the best solution for now.   I
also have an old CL-36 (24 ft boom) in the garage with a couple of bad trap
coils.   I've been drawing possible configurations and could not find a way
to get 3 bands that I was comfortable with.   If I put on the full size
reflectors,  I would still have  3 elements on each band with a grand total
of 8 trap coils.    

Here is the plan I came up with and I would like some comments on it.  This
is not of general interest, so just reply to me unless you think your
answer would benefit everybody.   

THE PLAN: Use the CL-33/CL-36 parts to build a 10 and 20 meter antenna on a
24 foot boom.    Use the driven element from the Classic-33 but eliminate
the 15 meter trap coils.   Eliminate the classic feed system and adjust the
D.E. for resonance on 10 and 20 meters.  

Add full-size reflectors and directors for 10 and 20.    This leaves a
grand total of two trap coils in the antenna.     

Why 20 and 10?     I think there will be less interaction between the
elements because of the frequency separation.    Using only two small  trap
coils  add less inductive loading on 20 meters.   I have another tower,
rotator, guy wire, and 15M monobander in storage.    I can manage two
towers (about 60 ft each), and this will allow using 2 radios at the same

Pending suggestions from TowerTalkians, here is how I see finalizing the

1.  Use YO to design a 3 element 20 meter yagi on a 24 foot boom with 50
ohm match  and use the results for the 20M reflector and director
dimensions and  D.E. placement.     

2.  Use YO to design a 3 element 10 meter yagi and use the results for the
10M reflector and director dimensions and spacing from the D.E.     4
elements on 10 ?  Probably not in the space I have but we'll see.   I don't
know what happens when you get directors for different bands too close to
each other.    

3.  Use EZNEC to look at the integrated array on each band and see if I
have any obvious problems.

Please let me know if you see any problems with my approach, or have any
suggestions.   I'd like to insulate the parasitic elements - worthwhile?  I
know elements + boom segments can cause spurious resonances that can add to
the  "one boom/ two antenna" problems.    What is a good method of
insulation?    U-bolts and some kind of plastic (phenolic???) plates?        

This is going to be fun!     Thanks for reading, and for any input. 

Dennis,   W5RZ


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