[TowerTalk] Portable tribander design help?

[n4kg@juno.com]

Portable Wire Antennas  de  N4KG

Two element inverted vees are simple to make
and effective.  The reflector needs to be 1/2 WL
electrical length (35 ft on 20M, 24 ft on 15M, 17.5 ft
on 10M).  Feed impedance will be around 30 ohms
which can be transformed up to 75 ohms with 1/4WL
of 50 ohm cable (RG68) followed by any length of RG59.
75 ohms is easily matched by most pi-networks or
automatic antenna tuners.  There are other more
complicated coax tricks that can be used to get to
50 ohms if you are fussy.  Last year I installed a 2L40
inverted vee beam using a rope boom between 50 ft
lighting fixtures at a baseball field for Field Day.  
Fed with RG8X and used an internal tuner. Worked GREAT !

Two element  DELTA  LOOPS  are very easy to build
and match.  Feed with an odd number of  1/4 wavelengths
of 75 ohm coax and you will be very close to 50 ohms.
Support the elements from 0.15 WL booms (rope, wood,
PVC, aluminum tubing) and pull the lower ends out with
nylon cord (yes it stretches when wet).  KILLER antennas.
Use the antenna book formula dimensions:
(DE = 1005 / F,  REF = 1030 / F).

de Tom  N4KG

>>>>>>>>>>>>>>

On Sat, 6 Jan 2001  Jim Idelson <k1ir@designet.com> writes:
> Hi guys,
> 
> No intention to start a controversy. I've already decided that an 
> aluminum yagi - even a small one - probably isn't the right solution 
> for this trip. We already have ski bags full of skis! I like the 
> idea of a super-tiny wire beam . . . it'll fit into the luggage very 
> nicely, and should be easy to install. I don't think I'm going to be 
> able to erect any kind of mast, and although the management is 
> pleased to allow operation, I think wires will be more visibly 
> acceptable in this case. That said, I have also received several 
> requests for a posting if I come up with a nice 20/15/10 triband 
> wire solution. None yet, though. I do appreciate all the positive 
> comments on the C3 family. I have purchased and installed one for a 
> friend. It's a fantastic product for the right application. Oh, one 
> more thing . . . I'm really interested in the design and 
> construction aspects of this project. It'll be fun! And, the plan is 
> to do it all well ahead of time here in the states, and test out ev!
> erything at home, and pack it all for instant assembly in EU. Thanks 
> to all for the suggestions. Please send more if you have 'em.
> 
> Jim K1IR
> 
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