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Re: AO40 telemetry CRC problem



Dear Nicolaus,

Thank you very much for your very interesting suggestions. I found the battery
idea excellent, and I will try it myself soon. I also noted your comments
concerning doppler and squint angle. I was (and still am) a bit puzzled because
the s/n ratio of the beacon signal at my station is very good (in the order
of 15 to 20 DB) and under these conditions psk31 copy is perfect and even
rtty is usually very good. Obviously, the psk sent by ao40 must be more complex
in format and more sensitive to aderse conditions (I must admit that I know
hardly anything about that - I will catch up on that!).

In any case, thanks again for your answer, and I look forward to meeting
you on the bird.

Allbest, Piero HB9DSU

*** ham radio, music and more - www.qsl.net/hb9dsu ***

>-- Original Message --
>From: "Nicolaus Sallay" <n.sallay@horizon.com.br>
>To: "Piero Calvi-Parisetti" <pcalvi@bluewin.ch>
>Subject: Re: [amsat-bb] AO40 telemetry CRC problem
>Date: Tue, 23 Dec 2003 07:42:50 -0400
>
>
>Hello Piero,
>
>- I have been waiting to some one more qualifyied than I to reply to you,
>but I did not have seen any returmn mail to your question.
>
>I only recently returned to the AO-40 activity, specifically on 2.4g and
>so I had to relearn a lot.
>Let me try to give you some indication on what to work.First I am using
>an AIDC 3137 converter plus a homemade power supply.Floor noise of
>the converter is S5/3. So I had to lower this noise to a bettere value and
>I obtained this by feeding the sistem with 24 volt battery a  regulating
>circuit to obtain 14,0 V DC at the input of the converter.Noise is now 5/2.
>I will not speak about antenna optimization because, first you know that
>and secondly I woud have to write the whole day and this is a hard job.
>Last not least, the most important point to copy CRC's continuously is
>a sattelite slowly moving in space.A high speed acsendig condition is
>extremely hard to follow due to, to fast doppler condition.
>Using, in my case, a 90 cm offset parabolic, elevation 60 deg, and a 
>SQUINT ANGEL below 35 deg you will be eable to start to copy CRC
>values in a rate up to 10% of the amount send. As the Squint Angel decrea-
>ses to lower values, 30, 27, 25 degrees and so on , you will start copy
>90-100% of all CRC's send by AO-40.
>As you may have seen, the point is the amount of offpointing between
>the sat antenna and your ground station.The lower the Squint Angel number
>is the better the condition to read the CRC's.It will make no difference
>by using IZ8BLY or AO40Rcv decoding program, the final result will
>be the same.
>I hope I could shed some light in to you problem to better understand the
>issue.
>Have a nice Christmas and Happy New Year
>
>73
>Nicolaus Sallay-PP8DA
>n.sallay@horizon.com.br
>Verificado c/Norton Antivirus 2003
>
>
>----- Original Message ----- 
>From: "Piero Calvi-Parisetti" <pcalvi@bluewin.ch>
>To: <amsat-bb@AMSAT.Org>
>Sent: Friday, December 19, 2003 4:40 PM
>Subject: [amsat-bb] AO40 telemetry CRC problem
>
>
>> Hello everybody again,
>> 
>> I must apologise for taking advantage of the experienced crowd on this
>BB,
>> but all the queries I had so far were responded to quickly, competently
>and
>> solved my problem right away. So, here we go again...
>> 
>> Why do the CRC constantly fails even if I receive the midle beacond between
>> 3 and 4 S units over the noise level? I have tried different settings
of
>> the sound card, to no avail. IZ8BLY's software shows quite some data,
but
>> the CRC fails constantly and other programmes show nothing. 
>> 
>> I'll be grateful for any advice.
>> 
>> And, if you have a minute, check out my homepage at www.qsl.net/hb9dsu
>-
>> there are a couple of fun satellite pictures.
>> 
>> Thanks a lot and 73. Piero HB9DSU
>> ----
>> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
>> Not an AMSAT member? Join now to support the amateur satellite program!
>> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>> 
>> 
>
----
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