[TowerTalk] HF Beam Questions...

[na9d at speakeasy.net]

Hi all,

This past weekend, I was finally able to put up my Bencher Skyhawk beam that I'd purchased from another ham last spring.  Now I have some questions!

The beam is mounted at a height about 53 feet.  Above it, I have stacked the following antennas:  11 element 2m beam, 17 element 432 MHz beam, 3 element 6 meter beam (in that order).

Each antenna is approximately 2.5 to 3 feet above the one below it.  Also on the very top is a Comet VHF/UHF vertical.

The tower is guyed Rohn 25.  At present, I have EHS guy wires that have been broken up with one insulator on most of the guys but 2 insulators on the longest guy leg.  It's not ideal and I plan on putting up non-conductive guys probably next spring.

My Skyhawk's SWR on 20 meters is about 1.6:1 or so across the band.  On 15 meters it looks quite good except for the lower portion of the CW band.  On 10 meters the SWR looks fine higher in the band but below 28.4 MHz, the SWR goes above 2:1.

My question is are the VHF antennas above the Skyhawk affecting the SWR?  Or could it be the guy wires or could it be both?  It seems like I remembered reading here or somewhere that with stacked beams, ones that are non-resonant at the frequency of interest will really appear to have no affect.  That's kind of the principal used when manufacturers put effectively 3 monoband Yagis on one boom with three feedlines.  But are these beams adding excess capacitance?

Is there anything that can be done?

Secondly, I don't seem to have that great of a front to back ratio with the antenna.  One day of playing around with it isn't much for sure.  But I was expecting the see a more dramatic drop in signal strength between stations on the front of the beam vs. the back.  I know S-meter's aren't all that accurate, but I seem to get somewhere between 1 to 2 S units in f/b ratio.  Yet, the beam is spec'd at 20 dB.  I don't seem to hear a 20 dB drop in signal strength.  I've never had a beam like this (previously had a TA-33) so I don't know what really to expect or look for.  Maybe I am seeing what I should be seeing....

Could all the other hardware up there be screwing up the antenna pattern as well?

Maybe there is nothing to be done and I just have to live with things as a compromise setup (I don't have the real estate to put up another tower for VHF/UHF).

Any advice or help would be greatly appreciated.

Thanks and 73,

Jon
NA9D