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
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