Hi George and the Gang!
I saw this post and wish to share some info here.
Several years ago, W8UVZ sent me the specs on the BC trapper which is the
wire version of the BC special loaner at about 102 feet total length.
I built two of these in 1995 using RG8X marine grade coax - and just as you
said - they smoked at 600 watts.
I then came up with an alternate gameplan that really WORKS using RG-213 coax
wound on standard 4" PVC septic tubing, schedule 40 PVC stock.
I have since built up about 7 of these BC trappers for a number of guys.
Pse don't HOLD me to these dimensions, but I think I used 10-12 turns of
RG213 close would around the 4" PVC for 80 and about 1/2 of that for 40M.
If you would like the EXACT grid dipped data, I would be glad to check my
files.
These RG213 traps are really RUGGED and can take 1.5KW with ease. One chap
(who shall remain nameless) in Conn runs 2 x 8877's into them - I will let
you guess the output power they are handling!!!) - and, so far, he too has
not smoked 'em either!
So I know they stand up and are really simple to make.
I use PVC end caps and 1/4 inch eyehooks to support the strain caused by the
weight of the traps. In tough environments, I use #10 stranded THHN
electrical wire for the L radiator itself - as a safety margin - but #12 THHN
has proven itself capable as well to take the weight.
Now - let me anticipate the next question - I am not in the business of
MAKING these traps. I did for a time - and it takes me about 2.5 hours to
make two traps - at a cost of materials of around $20 for the pair.
Obviously, my time invested at the typical K1ZM Communications. Inc billing
rate doesn't allow me to charge what these traps REALLY COST ME in terms of
my time - EG: about $170 a pair!
That having been said, I might be willing to do a pair (now and then) to help
out the Battle Creek crowd - but would much prefer that other interested
parties inquire to me DIRECTLY in order that I might tell them how to do it
instead - themselves!
Hope the message above is interpreted in the manner in which it was intended.
EG: I will gladly do my bit to help out deserving expeditions - and will
gladly help others build these traps - with the info required to get it
RIGHT!
But, I DO NOT WANT to be asked to build them for $25 a pair (at my cost of >
$170) - as was starting to be the case in 1995! HI HI!
One final point - When I first set up my station on Cape Cod in August 1996,
I used my 7th BC trapper at 102 feet using (2) of these same traps.
Interestingly enough, here were the SWR curves for 160/80/40 meters over a
radial system of 66 bare copper radials - on the ground - at varying lengths
of from 66-130 feet. The L radiator was hung from a tall pitch pine with 60
feet of it vertical and the remaining 42 feet bent over on its side to
another pitch pine also at about 60 feet in height:
160M 1832 1.1/1 (less than 1.5/1 from 1800 - 1860)
80M 3505 1.3/1 (stayed less than 2/1 to over 3550)
40M 7005 1.2/1 (stayed less than 2/1 to 7100)
Tuner required for 40M SSB and 75 Phone!
I ran full legal power into this system on all three bands with no problems -
so I am pretty sure it would work just fine for any dxpeditions that might be
contemplated. Even with the 4" diameter PVC traps -wound with RG213, the
total weight of this antenna when fully assembled is about 14-17 pounds. I
would imagine this reasonable for a dxpedition having some adequate means of
support (such as a 40 foot tall tree or telescoping FIBERGLASS mast!)
73
Jeff K1ZM@aol.com
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