[NLRS] Unknown antenna for eme last weekend

[Chris Elmquist]

Hi Mike...

That looks like a Hygain circular polarized OSCAR antenna to me.  I have
one and also the 2m version.

It should be resonant around 435 though and not 460.  I would suspect
either the MFJ unit's accuracy at that frequency or a failure in the
circularity switcher... which is the little piece of PVC pipe where the
feed connector is mounted.  There is a small RF relay in there which is
used to change the polarity from RH circular to LH circular when +12 is
applied to the pigtails coming out of the PVC housing.

The feedpoint of each yagi is not 50 ohm in this design.  It is more
like 90 or 100 ohm which is then paralleled via the circularity switch
to obtain a 50 ohm match to your feedline.  The coaxes coming out the
back of the circularity switch are also not 50 ohm but 90 or 100 as well.

I will dig up the docs that I have and send them to you offlist.

Chris N0JCF

On Tuesday (04/20/2010 at 10:41AM -0500), Mike KBØozn wrote:
> 
> 
> Hi all,
> I like so many tried to receive the Arecibo signals.  I got a tripod 
> with an AZ EL rotor (that's supposed to be on the roof  lol) and a cross 
> pol. 70cm antenna set up.
> 
> I hooked it up to a 857 and proceeded to hear static......  Sigh, well, 
> I gave it an hour break and lo and be hold there was some sort of tone 
> there.  I got the laptop out and used winrad to watch the output of the 
> radio and sure enough there was something there.
> 
> So, I did hear something.  Yea, my first signals from the moon.
> But, boo in that this antenna must stink or something.
> 
> So I put the MFJ 269 on it and found that at 432 it was infinite swr but 
> that it started to come down around 460 which is where the MFJ269 peters 
> out.
> 
> So, I took some pictures of the feed section of the antenna in hopes 
> that someone could help me to identify it and thus find out the specs 
> and thereby hopefully figure out how to fix it.
> 
> The pics are at: 
> http://picasaweb.google.com/102080719020464367699/UnknownAntenna#
> 
> Any thoughts or ideas you have would be much appreciated.
> 
> Mike
> KB0ozn

-- 
Chris Elmquist