Re: [amsat-bb] Uplink power

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

At 01:03 PM 12/18/2002 +0000, malcolm.hall2 wrote:
>Hi Guys
>We have heard all this talk about 'high power' before
>Now we are getting it on AO40!
>Back in the days when John LA2QAA and I were working FO 20 we both tried to
>stress the fact that high power was not the answer.
>At that time we were both running around 2-5w into the bird and getting 59
>reports,now I hear stations saying they are running 100w,ok FO20 is not in
>such good condition now
>The same criteria applies now on AO40 .
>It's the EARS not the MOUTH thats important ,improving the downlink will do
>away with need for 'high power' and lead to less stress all round!
>
>Merry Christmass guy's,and a Happy new year
>
>Malc G7NFO
>O to be young again!

In the first year of operation I "harped" that message a lot!  Have been
content for others to take up cause lately, since I have been off the air.
Guess its time the message goes out, again:

If you are not using a low-noise (and that means under 1 dB noise figure)
preamp on your 2401 MHz receiving system, you are not going to hear AO-40
well enough!  There are only a very few exceptions and they are
downconvertors with under 1 dBNF!  If you don't know what NF your convertor
has, then it needs a preamp!

The preamp MUST be connected directly to the feed of your dish.  If the
design of your dish absolutely prohibits this, keep the coax length to few
inches.  That coax is ruining the good NF of any preamp!

A dish is mandatory for good hearing.  Getting by using helix or yagis
doesn't make it!  Sorry this is just the facts!  That dish better have
close to 24 dBi gain, or you are not hearing well enough.  Minimum size
dish is the 60cm G3RUH and you better be using a super-preamp with it!  I
really suggest you have at least a 30-inch dish!  Getting a 3-foot dish
will make a complete difference in your operating experience!  Ignore all
Amsat pre-launch literature to the contrary!

When you have 24 dBi + 0.8 dBNF + 30dB gain, it doesn't matter much what
follows it!  You will be able to hear your own 5w uplink signal when squint
is good!  

A lot of guys will tell you oh I have this or that and "I do OK"!
Uhuh...they are probably the ones running -3 dB below the MB, too! 

My new hearing system will be a 8-foot dish, patch-feed, DEM preamp, Drake
downconvertor!  I can hardly wait to see how good that will be!  In fact it
will be good enough for eme!  The only difference between your AO-40
listening system and a Moon bounce station is (should be) the size of the
antenna!  The good news it is pretty easy to do!

So with that...I sure hope you have a nice Holiday!

Ed - AL7EB

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org