Re: [TowerTalk] HF Beam Questions...

[Jon Ogden <na9d@speakeasy.net>]

I think I may have found part of my problem.

Tonight I climbed the tower and inspected the feed to the Skyhawk.  One 
of the feed straps coming from the balun was touching the outer part of 
the driven element.  From what I can tell, the feed straps and the 
outer part of the element should not be shorting out as where the 
straps attach are into dielectric.  I loosened the saddle clamps on the 
driven element and moved it slightly.

Now, when I tune up on 20m, my SWR is pretty much at 1.4:1 or so across 
the band.  15m is very good except for the lower end of the band where 
it rises to 1.7 or 1.8:1.  Ten meters still behaves pretty much like 
before.  Good SWR up higher, but bad in the lower part.

But the big difference seems now to be that I can hear the antenna 
pattern when turning the antenna and listening to stations.  There is 
no definitely nulls and definitely a f/b ratio.  So perhaps I was 
basically shorting out half the antenna.  I think my 10m SWR issue is 
likely related to my conductive guy wires.  These will be replaced next 
spring with fiberglass rod.

If anyone reading can give me any opinions/back me up on my findings, 
that would help.

Thanks es 73,

Jon
NA9D

On Monday, Sep 29, 2003, at 09:27 America/Chicago, na9d@speakeasy.net 
wrote:

> 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
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com  for "Self Supporting Towers", 
> "Wireless Weather Stations", and lot's more.  Call Toll Free, 
> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

Ham Radio Webpage: http://www.qsl.net/na9d   <- Updated on 1/12/03!!!
Digital Photography Page: http://homepage.mac.com/jogden

"Right is right, even if everyone is against it; and wrong is wrong, 
even if everyone is for it."
	                                                             - William 
Penn

_______________________________________________

See: http://www.mscomputer.com  for "Self Supporting Towers", "Wireless Weather Stations", and lot's more.  Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.

_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk