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Re: Is my AO40 beacon strength average ?


It's impossible to tell from how you describe your station. Using something
without specifying the order isn't enough information, so let's start over

Is your setup like this: (this is the preferred and proper setup)
Eliminating the first foot of coax is even better of course)

Ant > 1 ft of coax > Preamp > 1 ft of coax > Downconverter >  20m of coax >

You don't even mention your Downconverter. What is it and where is it?

or are you set up like this:

Ant > 20m of coax > preamp > downconverter > ft-847?

or like this:

Ant > 1 ft coax > preamp > 20m coax > Downconverter > short coax > FT-847?

Each one of these acts totally differently and will produce drastically
different signals.

When you ask questions, you really need to provide more info so we can help.
Here is what is needed for ANYONE to give a decent answer to questions about
signal levels:

Ant: Brand/size/polarization and/or gain in dBi or dBc
Length of Coax and type between Ant and preamp or downconverter
NF and Gain of the preamp (or at least its brand and model)
NF and Gain of the Downconverter (or at least its brand and model)
Length of Coax and type between the Downconverter and your Radio

What is the S-meter reading with no signals, just the Downconverter
What is the S-meter reading with the beacon?

You say your noise level is < S-1 and the beacon is S-3. That isn't all that
bad, depending on how many dB you have from less than S-1 to S-3.

On my 847 I see the MB at S-7 and the noise floor at S-2.5 or S-3. Measured
with a calibrated attenuator this is > 20 dB signal to noise ratio, which is
very good.

If you are using Jim's dish and feed, you should have up to 5 dB more gain
than I do on my receive system, if your downconverter and preamp are the
equal of the UEK-3000. My system looks like this:

Ant: HyperLink Tech 39" BBQ dish, 24 dB gain linear (horizontal)
1' coax
UEK-3000 Downconverter: 0.6 dB NF, 30 dB gain
80' LMR-400 coax, < 1.2 dB loss at 2m

On the TX side, I can't tell what your antenna is from it's description.
What is an 8 9 ele vert beam? If it is a 9 el yagi, you have about 10 dB
linear gain, or 7 dBc, which is a bit puny. You also don't tell us what kind
of coax and how long it is for your transmit part of the station.

My system on TX:

FT-847 @ 12 watts out on 70cm
80' LMR 400 coax, 2 dB loss at 70cm
M2 CP-30, 14.2 dBc gain

This system produces a 12 dB signal to noise ratio on my signal. In other
words, I hear myself, using my system 12 dB above the noise. This
corresponds to about S5 on my FT-847. The Beacon is S7, I'm S-5, noise floor
is S2.5.

Your tx gain or EIRP is down quite a bit due to low TX antenna gain. As you
can see you are about 7 dB below mine just in the antenna. I can't compare
losses because you didn't provide that information. You can make up for that
with transmit power. As you can see from the example, I'm only running 12 w
out, and you have 50 available. (but how much tx coax loss do you have?)

Back to the "old saw".....

If you have a PC (IBM variety, not mac or linux), you can download an Excel
spreadsheet from AMSAT ftp site that will answer all these questions for
you. You can then play and learn how all this fits together. The spreadsheet
is specifically designed for AO-40 Link Budget Analysis. There is even a set
of instructions on how to use it. If you can't find it on amsat, let me know
and I can email it to you as an attachment.

Play with it and you will see exactly how loud you should be, and whether or
not your system is performing properly. You can then decide what changes to
make that will improve your system, without spending any money.

Hope this helps. 73

...hasan, N0AN

----- Original Message -----
From: <darren.rainer@btinternet.com>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, December 10, 2002 6:57 AM
Subject: [amsat-bb] Is my AO40 beacon strength average ?

> Hi all, I am wondering if my received signal from AO40 is average for my
> I am using the following :
> FT847
> 20 metres of RG213
> DB6NT MKU24 pre-amp
> G3RUH 60cm dish and patch feed.
> AO40s beacon never peaks above S3. My noise floor < S1.
> I can hear my signal coming back about S2 using 50 watts into a 8 9 ele
vert beam on 70cm. I tried a 1m prime focus dish last night and got the
beacon to S5. Is there anyone out there using a 60cm dish and patch getting
S9 signals ? or are some of the reports a bit on the keen side.
> I have painted the dish with plasticote paint which is non metalic, but
wondering if this could be having some effect.
> Regards
> Darren Rainer G4VTQ
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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