Fw: [AReU] Fw: 18 "Dish Network" Dish

[w4tas]

I have a patch feed, a 2.5 turn helix feed and Ed had a dipole feed 
from an old MMDS antenna. I have ordered a wide band LPDA 
antenna good from 2.1 to 6 GHz and if it gets in we will give it 
a try both as a dish feed and by itself. If it comes in we will try it 
with a RHCP helix transmit antenna and a dipole feed antenna on 
transmit. I am designing the signal source to be very stable in 
output  and the frequency source is a 40 MHz oscillator block 
with a TTL output. Nice for harmonics. The multiplier will be an 
MMIC with skewed bias for good harmonic generation. All of this 
will be built in an aluminum enclosure with multiple bypass paths 
on the power input to eliminate leakage. The output will be filtered 
to "clean up" the 2.4 GHz signal. All harmonics should be at least 
25 db down as the output filter seems to be relatively sharp and 
the nearest harmonic will be 40 MHz away.

I thought we would set up the signal source about 200 yds away 
from the test site and install a 3.5 turn RHCP helix to simulate 
the AO40 satellite. We would use the same downconverter for 
each receive antenna and go through 2 ea. zero to 30 db commercial 
attenuators good to 2.5 GHz (brand new and $10.00 each--what 
a find!). This will give us a 60 db range and that should do the job. 
By using an FM receiver on 2 meters we will adjust 
each attenuator for the same S meter reading for each antenna 
and compare the attenuator settings to determine the difference 
in gain. 

I will build another RHCP helix to compare the difference between 
having a LHCP receive and RHCP transmit antenna (should be 
gigantic!). I will try out a dipole transmit antenna with a dipole 
receive antenna as well. 

I realize that my helix antennas are not characterized to 50 ohms 
but I have no choice as I do not have a return loss bridge good to 
these frequencies. When I get the signal source going and if I 
have enough power output for my old spectrum analyzer to 
read after taking the losses, I will look for a return loss bridge 
to at least measure the return loss and tune them up a bit. 

I have a HP 614A that puts out a bodacious signal to 2 GHz.  
If I use a 1N21 diode for a multiplier and filter it through a 
interdigital or tuned stub filter it puts out a great signal on 
the second harmonic of 1.2 GHz and should be adequate 
if the signal source fails to be strong enough. 

I have a double concern about the source. If it 
is too strong I will overload the receivers and will have leakage 
when using attenuators to get the signal down to a reasonable 
but if it is too weak I will not be able to detect it on my 
spectrum analyzer. Oh the problems !!!!
I love it!!!!! 

Thats my story Ray and I'm sticking to it. Hope to see you soon 
and hope you and yours had a VERY Merry Christmas and 
are looking forward to a great new year. 

73

Tony




-----Original Message-----
From: Ray LaRue <w4byg@earthlink.net>
To: areu@mailman.qth.net <areu@mailman.qth.net>
Date: Wednesday, January 02, 2002 4:22 PM
Subject: Re: [AReU] Fw: 18 "Dish Network" Dish


>Sounds like another field test coming up.  Could be fun.  
>
>FYI, the 18" dish used by Direct TV and Echostar calculates to have
>about 18.5 db gain a 55% efficiency @ 2.4ghz.  If your really good with
>physically matching the feed to the dish, you might get 19 db gain at
>60%eff.
>
>Let me know how you do in the "tests".
>
>Warm Regards, And Happy New Year,
>Ray, W4BYG
>_______________________________________________
>AReU mailing list
>AReU@mailman.qth.net
>http://mailman.qth.net/mailman/listinfo/areu