[NLRS] 6 and 2 meter antennas

Wed Jan 25 11:01:31 EST 2012

Is it possible that you might win in a tradeoff of height for gain by putting some (relatively) small antennae higher up?

Let's say 13db gain at 50 ft vs 16db gain at 30 feet including the difference is coax loss?

If you move the antennae spacing to 1 wl at higher band, how much cross coupling is there between bands? Is protecting preamps a concern?

One year Ron and I went to the four corners by Mankato for a contest and ran 432 and 1296 simultaneously using 24 elements on each spaced maybe 18 inches apart on boom. It worked well, and his 3rd harmonic didn't cause me any desense.

----- Original Message -----
From: Dr. Gerald N. Johnson [mailto:geraldj at weather.net]
Sent: Wednesday, January 25, 2012 09:48 AM
To: nlrs at mailman.qth.net <nlrs at mailman.qth.net>
Subject: Re: [NLRS] 6 and 2 meter antennas

While researching and computing for my 2011 Aurora presentation on how 
close can you stack yagis, I found the first 9 elements of the FO12 
design on a 10' boom had the same pattern and practically the same gain 
as the M2 2m9ssb on a 14.5 foot boom. I built a copy of what I call the 
FO 9 for 432 on a 1 meter boom and sent it to CSVHF where it came in a 
dB better than computed. I suspect WB0TEM's reference antenna has begun 
to fail from old age.

In my paper (subsequently published in NEWSVHF/MUD 2011 and submitted 
for CSVHF 2012 and on line at:
http://www.geraldj.networkiowa.com/papers/Aurora2011/) I found that the 
penalties for spacing yagis closely is not severe. And that the 1/2 boom 
length spacing isn't necessary, that about 1 wavelength on the high band 
is enough to have virtually no effect on the high band gain. The low 
band itsn't affected by the high band antenna at all. Conventional 
wisdom for eons is that the minimum spacing should be a half wave based 
on the concept of capture area. What I found by computing and by a 
limited experiment is that for a short yagi half boom length hurts worse 
than 1 wavelength spacing and that for a long yagi, one can slip closer 
than 1 wavelength without a severe gain and pattern penalty.

There is a paper on the Directive Systems web site all about capture 
area and the required spacing for multiband yagis based on that concept.

In my paper the last two figures tell it all, one has gain loss plotted 
vs boom length, the other has gain loss plotted vs wavelength. There is 
a wide spread vs boom length, but the curves bunch when plotted vs 
wavelength.

There are two schools of thought on stacking, most of the world and then 
WA5VJB and me. Interestingly in 1948 the ARRL ranking VHF guru W1HDQ in 
a QST article concluded close spacing was fine and then in the earliest 
ARRL VHF Handbook I have that he edited, the 1/2 boom length rule of 
thumb is all that's admitted.

I've not noticed any of the LFA tested at US VHF conference antenna gain 
events. But there is where many an antenna with great claims has been 
shot down as not producing, including designs of mine.

In my opinion you should stack closely and get the 432 way up top, that 
on the chimney you may work only the super stations beyon 100 miles with 
the antenna on the chimney. I took down my array from 60 feet plus and 
moved and for temporary use have been using a couple smaller antennas on 
a tripod on the roof (tripods were already on the house I bought on a 
hill top) and with trees and a machine shed out back above the antennas, 
performance is not great. 6m sporadic E is more forgiving, I've worked a 
lot with a yagi at 15 feet elevation and last year FD and June conest 
with a dipole in the garage.

There could be 432 activity, used to be some other than contests and I 
have a couple contest certificates for 432 only activity. Today with the 
multiband stations nobody even listens during a contest other than 6 and 
2 and then runs the bands too quick for tailgating to work. GRUMP!

The K1FO designs are very well proven and THEY WORK! FO12 for 2m is 
reasonable for size and maybe FO22 for 432 though it will be a lot more 
directive and so need more careful aiming than the 2m antenna.

Put something up with as fat a feedline as you can't afford and as high 
as you can, but remember than any antenna at any height fed with any 
coax gets out better than it did IN the box on the dealer's shelf. And 
there are manufactures that make more than outrageous gain claims which 
are consistently shown up at CSVHF and other conference antenna 
measuring tests that are published on line as well as in the subsequent 
proceedings.

73, Jerry, K0CQ

On 1/25/2012 7:05 AM, kp hpjr wrote:
>
>
>
> GM,
> I'm in the process of deciding which direction to go in regards to changing my 6 and 2m antennas.
>
> Currently I run a 2/432 8 element Quad at 50'.
>
> I'm considering the following antennas and would like some input from this group.
>
> For 6m these have my attention:
> DS50-4HP 50 MHz Yagi from Directive Systems http://www.directivesystems.com/
> LFA 406-11.5'  4 element Loop Fed Array. http://www.texasantennas.com/index.php?option=com_content&view=article&id=218&Itemid=223
> M2 6M3 http://www.m2inc.com/index.php?ax=amateur&pg=76
>
> For 2m, These have my attention:
> M2 2M9SSB or the 2m12
> DSFO-144-12 from Directive Systems
> LFA-902 http://www.texasantennas.com/index.php?option=com_content&view=article&id=214&Itemid=220
>
>
> The LFA antennas look appealing if in fact they do what is claimed and reduce the local noise pickup. But I know of no one that has or uses these newer antennas. And I'm not really aware of how well they are constructed for that matter so any input would be great.
>
> Choosing any of these options clearly leaves me w/o 432.
>
> My only option then would be to mount a 432 yagi at about 19' on the side of our chimney and turn with TV rotor. At that height, how well will an antenna on that band perform? I'm begining to think that, for the most part, the only real contacts to be had from this area on 432 are what is available during the contests. So I would assume that even at 20' or so, I'd still be able to make the QSO out at a range of 100-200 miles w/o much trouble. Would this be correct?
>
> Thanks for taking the time to look at these questions from a newb! LOL
>
> Kirk, N0KK
>
>
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