Re: [amsat-bb] 1.2G mast mounted amps

["Edward R. Cole" <al7eb@xxxxxxxxxxxxx>]

>From: "David A. Minster" <dminster@optonline.net>
>I am in the final configuration stage of my big antenna project.  I just
>completed construction of the 35 element M2 for 1.2G and will be
>testing/adjusting this week or next.  The question is:  is anyone mast
>mounting their 1.2G amplifier, and if so which amp are you using and how are
>you weatherproofing it?  I'll be driving the amp with an FT736R and the
>amp/antenna will be about 120' from the rig.  Based on some work the Steve,
>WI2W, did with the AO40 spreadsheet, it looks like I will need about 30
>watts +/- at the antenna for reach out to apogee with this M2 yagi.
>
>David
 
David,

I am just completing a casual survey of mode-L stations to see what their
experience is regarding this question.  I'll post a summary on the -bb in a
day or so...and maybe a more detailed article for the Amsat-NA Journal.

My personal experience is using a 15w Downeast Microwave transmit converter
with about 20-foot RG-8 coax [2 dB loss] to a 2345LY loop-yagi having 20
dBi gain.  I think I may have about 9w at the antenna.  I see about one
s-unit downlink signal above noise, which is adequate but not strong [what
I saw last night at squint 13, range 52,000 km].  I have decided to move
the converter to the crossboom adjacent to the loop yagi and use 6-foot of
1/2-inch Heliax to feed the antenna.  My calculations show that I should
get ~14w at the antenna from my 15w converter.  That should help.

A freind of mine is planning on mounting a DEM 2318 PA right at his 2345LY
antenna connector, so he should have 16-18w.  We think that will give him a
two+ s-unit over noise downlink signal.   He is also considering adding a
second 2345LY antenna for another 3 dB gain.  He is currently using the 10w
output from his FT-736R thru 32-foot of 7/8-inch Heliax.

If you can get 30w at the antenna [the M2-23CM35 yagi is supposedly also 20
dBi gain] you would have a very respectable signal from what I have seen.
What amp are you considering?  Getting power above 20w on 1.2G is not easy
or cheap!

Ed

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