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G3RUH vs K5GNA




I started to work AO-40 about 2 months ago with a K5GNA complete package 
that I had modified by adding a screen covering the grill.  I was generally 
pleased with the results although the QSB was a bit annoying.

Over the weekend I purchased a G3RUH from a friend who upgraded to a 4' 
dish.  It offers quite a few features I was planning to homebrew into the 
K5GNA.  These were to modify the BBQ into a round dish, and adding a 
circular feed of some sort.  Since I live in a townhouse apartment I was 
still trying to workout the logistics of how to build the mods (space, 
tools, materials, etc) it was attractive to buy something that was 
virtually plug and play.  The G3RUH also offered a smaller size and 
circular patch feed. Here are my impressions:

Size:
G3RUH =60cm round (2827 cm2)
K5GNA = 62 X 90 cm rectangle (5580 cm2)

Feed:
G3RUH=Right Hand Circular patch feed
K5GNA=Horizontal Dipole

Modifications:
I had to build an adapter plate to match the 2x2" pattern of the G3RUH to 
the 3.5" width of the K5GNA brackets.  This was important it needed to fit 
over a 1" PVC "T" to allow me to easily tilt the dish up and down.  (see 
http://www.emilyshouse.com/W0EEC/AO-40.php for details)  Since I was going 
to use the same downconverter (AIDC 3731) I also had to remove the dipole 
and replace it with an N connector.  I have to hand it to Bob K5GNA - he 
thought of everything.  It took 3 minutes to remove 4 screws, swap the 
connection and replace the 4 screws.

Observations:
While no means scientific, the noise level of both antennas is comparable. 
I believe this is because the vast majority of noise is coming from the D/C.

It was very quickly apparent that the signal strength of the G3RUH dish was 
greater.  Once I found the middle beacon it was about 6db stronger than 
before using the K5GNA.  In terms of relative signal strength (with a noise 
level attenuated to S0) the middle beacon is now S8/S9 over the noise 
floor, and QSOs are S6+. The K5GNA levels under similar conditions produced 
signals of S5-6 for the middle beacon and S2-3 for QSOs. The patch feed did 
not appear to decrease noise from 2.4GHz appliances but I'm they weren't 
any stronger either.  This lead me to conclude the S/N ratio is better.

One thing I didn't expect was the gain of the G3RUH to be flat over a wider 
beam than the K5GNA.  Since I live in an apartment and manually position 
the dish this is a real benefit.  The K5GNA needed to be repositioned about 
every 15-20 minutes.  Today there was virtually no change in signal 
strength for almost 40 minutes.  I've enjoyed rain free weather since May 
but they are predicting a very wet winter.  So I'm going to really 
appreciate not having to go outside so often the rains come.

Lastly, the G3RUH is about 30 percent lighter than the G3RUH. Since I move 
my dish around a lot, this is important to me.

73,

Emily





W0EEC - CM87tm
ARRL - AMSAT - MSARC - ARCA - Project OSCAR
http://www.projectoscar.net
http://www.emilyshouse.com/W0EEC
http://www.experthams.net/ao7


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