[amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
Gary "Joe" Mayfield
gary_mayfield at hotmail.com
Fri Oct 2 18:27:13 PDT 2009
We are missing the easy answer. He had diplexer that was off spec. It
happens.
73,
Joe kk0sd
-----Original Message-----
From: amsat-bb-bounces at AMSAT.Org [mailto:amsat-bb-bounces at AMSAT.Org] On
Behalf Of Jeff Yanko
Sent: Thursday, October 01, 2009 4:28 PM
To: Charles Suprin
Cc: Joe; AMSAT-BB; Gary "Joe" Mayfield
Subject: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
Hi Charles and the group,
FB on the numbers. Interesting to say the least and thanks for taking the
time to look further into this topic.
Questions? I have a few after looking at these numbers and performing more
observations.
First, are you testing just the diplexer and not the diplexer and the
antenna combined? This could result in an overall number and not just the
diplexer alone. How could there be a large discrepency between preliminary
reports, 2.65dB and .5dB now. Could be equipment calibration, human error,
etc. from previously tested, or attempted testing of the device. I don't
believe any improvements have been made to the Arrow diplexer, but who
knows?
Second, I switched back to the Arrow diplexer and made another comparison
with the Comet diplexer. Again, no comparison, the Comet outperformed. Why
would this happen if the two are pretty close to one another in numbers.
The Comet has .25db loss at VHF and .26 at UHF.
Third, with the Arrow diplexer I wouldn't begin to receive the birds until
almost 3 minutes after AOS, with the Comet diplexer a minute to 1.5 minutes
after AOS. Yes, watch calibrated to WWV and multiple times of acquiring the
birds. I've tried both setups with the HT and D710 and they both show the
same results respectively, Arrow diplexer vs. Comet diplexer. The antenna
and coax remain the same, the difference, the diplexer. May not be test lab
quality but something is proving itself. What is it?
Finally, is it just my Arrow diplexer? Doesn't appear to be shorted or any
defects to it. Actually looks great and assembled very well. I've
encountered others saying the same thing. However, a very noticable
difference to the overall performance.
73,
Jeff WB3JFS
----- Original Message -----
From: Charles Suprin
To: Jeff Yanko
Cc: Joe ; Gary "Joe" Mayfield ; AMSAT-BB
Sent: Thursday, October 01, 2009 1:09 PM
Subject: Re: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
Howdy Jeff,
Someone asked and here we go. A file attachment follows.
Actually the diplexer looks pretty good. Less than half a db of loss at
VHF and around half a dB at UHF. I checked the calibration and that was
within tenth of a dB over the entire range.
Any questions.
Charles
AA1VS
On Sat, Sep 26, 2009 at 6:26 AM, Jeff Yanko <wb3jfs at cox.net> wrote:
Hi Joe and all,
I doubt if the Arrow diplexer has 20dB of loss. If it did, we'd never
receive a signal! :)
I believe somebody here on the -bb will be performing a test on the
Arrow
diplexer using a vector/network analyzer. It will be interesting to say
the
least. There were preliminary reports saying the device had a loss
anywhere
from 2.65 to 2.80dB. That's close enough to 3dB which is technically
half
power loss. Add the loss of a short piece of coax and it will certainly
be
pushed over the 3dB line.
If I recall correctly, cross polarity is also a 3dB loss. I have
noticed
that when I rotate the antenna I might get a stronger downlink but I
never
lose it when I rotate it back. Before, when I would do that it would
drop
once I rotated in either direction from the peak signal. Basically what
is
going on is the lossy device is removed and replaced with a more
efficient
one, that extra net gain you just boosted now shows how the system on
the
antenna side of the diplexer is truly performing.
I don't have an antenna analysis program to perform a test, but what
does a
7 element 440 yagi pattern look like and what is its overall gain?
What we need to do is break down the antenna configuration into 3
segments,
see what their losses and gains are then combine them for the overall
figure. The 3 segment would be the antenna, the diplexer and the coax.
Each one will be tested individually to give an accurate number for
each.
73,
Jeff WB3JFS
----- Original Message -----
From: "Joe" <nss at mwt.net>
To: "Gary "Joe" Mayfield" <gary_mayfield at hotmail.com>
Cc: "'AMSAT-BB'" <amsat-bb at amsat.org>
Sent: Friday, September 25, 2009 6:42 PM
Subject: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
> as in the texts below, there is something else going on here.
>
> That Diplexor can not be all that bad. two reasons.
>
> How many db down is the front to side of that antenna?
>
> and I can not imaging someone would sell a diplexor that has greater
> than 20 db of losses.
>
> because of the statement that how criticalpolarity was with the
> original, and now the antenna has to be nearly 90 degrees cross
> polarized to make it drop out uhh
>
> that close to 30 db,
>
> at least 20,,
>
> something else is going on here
>
> Gary "Joe" Mayfield wrote:
>
>>>
>>>Another issue I came across was how wide the beamwidth is of the
Arrow
>>>Antenna between the Arrow diplexer and the new diplexer. I was
wondering
>>>
>>>
>>if
>>
>>
>>>this was going to happen and it did. The reason that this happened
was
>>>
>>>
>>with
>>
>>
>>>the old diplexer, the signal attenuated so much that you had to be
>>>pointed
>>>right smack dab on the bird, a few degrees off and you lost the
signal.
>>>Now, with the new diplexer, you can point the beam in the general
>>>
>>>
>>direction
>>
>>
>>>and still copy the bird. In most cases I had to turn the beam 90
degrees
>>>before I completely lost the downlink! Twisting the antenna to make
>>>polarization changes makes absolutely no difference now. This also
>>>attributes to the fact that now I'm copying the entire pass without
>>>
>>>
>>dropouts
>>
>>
>>>or fades. Makes sense. What I've regained over the lossy diplexer
makes
>>>
>>>
>>up
>>
>>
>>>for any polarization differences, etc. for a better copiable signal.
>>>
>>>Next weekend I will have to try more passes and get a feel of how
much
>>>
>>>
>>this
>>
>>
>>>system has changed.
>>>
>>>
>>>73,
>>>
>>>Jeff WB3JFS
>>>Las Vegas, NV
>>>DM26
>>>
>>>
>>>
>>>
>>>
>>>
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>>>
>>
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