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

[Joe]

No, Cross polarization in the real world is 20 to 30 db loss.

In the theoretical world it's infinite,

http://www.amsat.org/amsat/archive/amsat-bb/200101/msg01220.html

Joe WB9SBD

Jeff Yanko 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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