[VHFcontesting] Multiband VHF antennas

[Tom Carney]

Earlier I had done some modeling of a 2M/432 single feedline antenna 
using the open sleeve technique.  These had not proven useful so I had 
abandon the approach.  Now, prodded by KK6MC's post, I tried again.

This time I started with 4 element 2M OWA beam instead of a conventional 
design.  Right off, it looked promising.  The 2M OWA beam modeled at 8.8 
dbi (free space), flat SWR, on a 33 inch boom.  Just by adding a 432 
open sleeve "driver", I obtained over 7dbi with and SWR below .125 to 1 
on 432.

I then started adding 432 elements.  With a 432 reflector and a single 
director, I obtained got up to over 9dbi with a slightly better SWR.

Unfortunately, ever thing I tried to add more 432 elements, degraded the 
performance.

Still, it's a simple antenna.  with four 2M elements, 3 three 432 
elements on a 33 inch boom I obtained almost 9dbi on both bands.  The 
pattern on 432 is more like a mushroom than what you would expect from a 
conventional yagi.  A very broad front lobe with only 8db front to back. 
  Not a world beater but looks promising for a Joe706 antenna.

It's fairly critical on the spacing of the 432 driver but even a tenth 
of an inch mistake doesn't degrade things a lot.

You should have a choke balun however.  Not sure the simple coin of coax 
will work at 432.  Might be a problem.

I'll keep experimenting.

73,

Tom K6EU