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Re: System RX comparison:



On Thursday 27 December 2001 04:20 pm, nick wrote:
> I am using an AIDC3733 and 2x3' BBQ dish mounted at 15' and looking
> through leafless trees.
> Most times I can get marginal beacon print using IZ8BLY's P3D decoder
> (latest vers).
> The satellite is now at 61500km range, 83 deg offpoint.  Beacon decode
> is about 20% successful.
> Never has the beacon been 100% at any range/offpoint.  The best print
> has been ~75%.
> Is this reasonable performance?

NO IT IS NOT.

HI Nick...... first of all with 83 deg Squint, you would be lucky to copy any 
good crc's. 

The best Win based decoder I've seen is AO40RCV ...it does an outstanding job.

I regularly get 100% good CRC's for half an hour at a time at good squints. 
(< 25 deg off pointing), using ao40rcv.


>
> I estimate another 3-4dB improvement possible by adding an inline IF amp
> for an IF of
> 123MHz and 75' of RG6 coax.

Changing gain at the IF will probably yield no improvement in S/N ratio, 
period. This is the wrong place to add a preamp. Put it out a the antenna, 
and you will see a dramatic improvement. They guys on the list can suggest a 
good preamp to mount at the antenna...that's the only way you are going to 
improve things...and it will make a BIG difference. You need the preamp at 
2.4 gig, not the IF freq. If you put a really good low noise preamp ahead of 
that downconverter, (< 1 dB NF, 15 dB gain), I would expect no less than 6 dB 
of receive threshold improvement. 

There also may be mods you can do to the DC to help it's performance, but you 
would have to ask others about that. 

With the following setup, I see the MB beacon 20 to 28 dB above the noise 
level any time the squint is < 25 deg:

(Measurements made with calibrated attenuator, not guessed with an S-meter)

39" Huperlink BBQ Dish, horizontal polarization.
UEK-3000 downconverter, 0.6 dB NF, 30 dB gain 
80' of LMR 400 from dc to Yaesu FT-847 on 145 Mhz

>
> Is there a more effective soundcard decoder out there?

ao40rcv...a google search will show you where to download it.

http://www.qsl.net/ae4jy/

version 1.40 is latest.




> What is the best solution for a tracking interface between InstantTrack
> and a G5400B rotor?
> I think there was a kit available from South America.
>
> At this range, 60W at the feed of an Msquared 44-el cross yagi is just
> about LEILA trip-level.

Also get a copy of Clay's Excel spreadsheet to evaluate system performance 
and you will be able to see when you should trip leila, what your rx 
performance is, all sorts of stuff. Best thing for ao-40 since sliced bread. 
I don't recall its name at the moment and I'm in Linux at the moment, so 
can't check the file name easily. (dual boot machine).

If you can't find it, let me know and I'll send it to you as an email 
attachment.

73....hasan

-- 
hasan schiers, N0AN
schiers@netins.net
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