[amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE

[Jeff Yanko]

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
>>>
>>>
>>>
>>>
>>>
>>>
>>>_______________________________________________
>>>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
>>>Not an AMSAT-NA member? Join now to support the amateur satellite 
>>>program!
>>>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>>
>>>
>>>
>>
>>_______________________________________________
>>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
>>Not an AMSAT-NA member? Join now to support the amateur satellite program!
>>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>
>>
>>_______________________________________________
>>Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
>>Not an AMSAT-NA member? Join now to support the amateur satellite program!
>>Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>>
>>
>>
>>------------------------------------------------------------------------
>>
>>
>>No virus found in this incoming message.
>>Checked by AVG - www.avg.com
>>Version: 8.5.416 / Virus Database: 270.13.113/2395 - Release Date: 
>>09/25/09 17:52:00
>>
>>
>>
> _______________________________________________
> Sent via AMSAT-BB at amsat.org. Opinions expressed are those of the author.
> Not an AMSAT-NA member? Join now to support the amateur satellite program!
> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
>