[VHFcontesting] Cushcraft A270-10S (triband VHF/UHF) beam question

[Alex]

Hi Tom,

 

The ham I bought the antennas from also used them as a rover antenna. It came with three harnesses. One harness was to stack two of these beams and then the other two are the duplexers (two equal lengths of coax with a SO-239 T connector if I remember correctly). I recently moved again and will have to look to see if I can find the antennas again. What I ended up doing with one antenna was to drop the 70cm elements and then reposition the first director so that I’d have a nice 2m beam. 

 

Thanks for sharing your thoughts. I appreciate it. I had posted my experiences before years ago, but got no responses. At that time I concluded that these interlaced beams were probably useful for repeater work, but not as horizontal antennas for CW/SBB use. I figured that that is why you only saw images of these interlaced beams mounted vertically.  Something that John also noticed.

 

73,

--Alex KR1ST

 

From: Tom Carney [mailto:wa4qvq at gmail.com] 
Sent: Thursday, April 17, 2014 5:44 PM
To: alex at kr1st.com
Cc: vhf contesting
Subject: Re: [VHFcontesting] Cushcraft A270-10S (triband VHF/UHF) beam question

 

Hi Alex

 

I also have an A270-10S but have been fairly pleased with the antenna.  Now, I agree, it not an antenna for serious VHF/UHF work.  I use it in my rover station.

 

I've also run some basic test to see what the pattern would look like and found the pattern fairly consistent with the EZ-NEC model of the antenna.  Per the model, it's a better antenna on 2M than 432.  

 

Interestingly, if you reversed the coax from the duplexor to the driven elements, you will get the pattern you described on 432.  SWR would be a bit high but not too bad.  However if you reversed the 2M coax (connected to 432 DE) you would get a very high SWR.  I have to wonder if your duplexor was faulty although I can't come up with anything that would give you a cardioid pattern on 2M.  

 

73,

 

Tom K6EU

 

 

 

On Wed, Apr 16, 2014 at 6:17 PM, Alex <alex at kr1st.com> wrote:

Hi John,

I bought two A270-10S antennas with a phasing harness from a fellow ham. I
put the stack at 30 feet (horizontally of course) and did some experiments.
I found that the performance was very disappointing on both bands . A simple
4 stack of halos at the same height would outperform the stacked beams on
70cm. It was marginally better than a single stack of halos at the same
height on 2 meters. The feed line lengths were the same on all antennas,
except that the halos were fed with RG-8x and the beam was fed by the
Wireman's LMR-400 equivalent...

Then I decided to try a single beam and had someone a few miles down the
road send a test signal while I rotated the antenna to get an idea of what
the azimuthal pattern was. It turned out to be a sort of deformed cardioid
pattern, barely directional, and the direction of maximum gain was about 30
degrees off. The pattern was similar on both 2 and 70 cm. My conclusion was
that these antennas were useless for weak signal SSB or CW.

Think about it. How often do you hear the question being asked about the
optimal vertical distance between a 2 and 70cm beam. I don't think anyone
ever answered "zero" to that question.

73,
--Alex KR1ST

-----Original Message-----
From: VHFcontesting [mailto:vhfcontesting-bounces at contesting.com] On Behalf
Of John Geiger
Sent: Monday, April 14, 2014 3:55 PM
To: vhf contesting; vhf at w6yx.stanford.edu; 50mhz; 6meter at yahoogroups.com
Subject: [VHFcontesting] Cushcraft A270-10S (triband VHF/UHF) beam question

I have a question about the Cushcraft 6m/2m/70cm yagi. Every picture I see
of it has the 6m elements horizontal and the 2m/70cm portion vertical. That
wouldn't work for me, I want to use it on 2m and 70cm SSB. It is possible to
mount all 3 bands with horizontal elements?

It looks like it is physically possible, but will it hurt performance, or
will it still work ok that way?

John AF5CC
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