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Re: Computer Woes...



Hi All,
    I have waited a bit to let some of the dust settle, from reading the 
comments it seems that many did not really read my note.

  I gave credit where credit is due,Emily is a worthwhile volunteer that has 
made significant contributions to Amsat,But I also think that there is room 
for improvement like there is for all of us including me.

  One person said it was and attack and I should have tried other means...

guess he missed " Now before anyone jumps and complains why I am airing this 
here and not
via other means you have to understand I have tried."

Here is a copy of the note I sent in one of my attempts... it is long please 
bear with me...

I quote...
 Ron and Emily,

    Might I suggest you rework your article
http://www.amsat.org/amsat-new/echo/ModeJ.php

your Theory..

"The idea is to channel the 70cm energy from the antenna into the preamp
while shunting the 2m energy into a load.  Since we are working with the 3rd
harmonic (down 9db from the fundamental), radiating 100 watts (probably 50W
at the antenna but still assuming 100 watts for the sake of the article)
would be the equivalent of radiating 12.5 watts minus the free space loss
between the antennas and the inefficiency of the 70cm antenna for receiving
2m. Again assuming the worse case scenario of no free space loss but that
the antenna is 9db loss for inefficiency, the amount of the energy entering
the front end of the preamp would be 1.56W. This is enough to desense most
any preamplifier. The true amounts are probably much less since the Yagis
will channel energy away from the active element of the 70cm antenna.

Adding the duplexer should provide another 60db of isolation. This would
further reduce the energy entering the preamp to approximately 2.9
microwatts or about 58 nanovolts which should be enough to avoid desense."

is partially incorrect,  a correctly working rig has a 3rd harmonic greater
than 60db down to start with,even if it didn't and had a strong harmonic
then your filter wouldn't work... your filter would not be able
differentiate between a real signal and the harmonic...what your actually
seeing is fundamental overload, the 2m signal is so strong  that it is
overloading the front end of the 70cm receiver.

You are correct that your filter does provide more isolation and that is
what corrects the desense.

"The idea is to channel the 70cm energy from the antenna into the preamp
while shunting the 2m energy which is causing the desense into a load,
adding a duplexer should provide another 60db of isolation which should be
enough to avoid desense."

  This might be a better theory since its about impossible to calculate the
exact amount of 2m rf energy that the 70cm front end see's, it varies
between every installation, antenna type,spacing,filtering at the 70cm front
end all come into play.

    Its a good article but it needs to be correct or  the bad theory causes
the reader stop and question the entire article...

73

Kevin WA6FWF

end quote...


I made a attempt to point out what was wrong and how to fix it... I may not 
be 100% correct either but I do know I am closer to the target, it removes 
the questionable power calculations and the 3rd harmonic info which is 
wrong.
  The response?  nothing absolutely nothing...

I crossed paths again with Emily on another subject, I added a P.S. again I 
tried....

quote" BTW you going to do anything about your article on the website? it 
really is
wrong, if you don't believe me just check around and ask others they will
tell you the same..."

again She could have fixed it.... could have asked others... could have 
responded....  what did happen?
nothing absolutely nothing...

I think I made honest effort to try and fix this problem off the BB.

One thing for sure I bet now  someone who is 100% correct and has a way with 
writing will come up with a proper theory and it will get fixed...

Now as far as my comments about the glossary, I never meant to imply that 
Emily did all of those,I was just pointing out some of the problems I had 
trying to get one of them  fixed.

I think others have pointed out some of the ones that need fixing,again try 
looking at this as an attempt to have a worthwhile glossary,not to figure 
out who wrote which one and point blame,lets just fix some of these issues 
Please.

73
Kevin WA6FWF
#19623
----
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