[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

RE: Equipment for 38.4kbps on S-band?



Hi Chris

The de facto standard at the moment for 38k4 is a TNC3S or TNC31S. I have
modified a G3RUH high speed TNC2 clone with some success too. In addition,
if you can find the 38k4 documentation in English, there is the TNC7 Multi
is a cheaper option, and supports both RS-232 and USB connections -
http://www.tnc7multi.de/index.html.

I don't recommend increasing the IF bandwidth to compensate for Doppler -
this will add to the S/N. In fact, after conducting some real world tests, I
seriously recommend tightening up the Symek IFD with a pair of 80kHz ceramic
filters and using Doppler correction.

An alternative to using an IFD is to use an ICOM PCR-1000 that can be used
without modification into a 38k4 TNC. However I find that it suffers from
desense from strong in band and out of band signals.

There aren't any 38k4 sound card programs I'm aware of yet. Whoever writes
one first will be doing everyone a favour! I am skrptical that it can be
made to work well with most sound cards because almost all start rolling off
at 20kHz despite having 96 or even 192kHz sampling rates. Some of us are
experimenting with the M-Audio devices (Delta 44, Delta 66 [96kHz] and
Audiophile 192 [192kHz]) with some success for other modes, in particular
the SDR-1000. The M-Audio devices start to roll off close to Fs/2.

73, Howard G6LVB

-----Original Message-----
From: owner-AMSAT-BB@amsat.org [mailto:owner-AMSAT-BB@amsat.org]On
Behalf Of Chris Hill
Sent: 16 September 2005 07:39
To: amsat-bb@amsat.org
Subject: [amsat-bb] Equipment for 38.4kbps on S-band?


Hi All,

I am gearing up to receive the telemetry from SSETI-Express
(http://sseti.gte.tuwien.ac.at/WSW4/MOPWS/understanding4.php).

The reception of 9600bps FSK packet on 70cm seems straight forward (I'll be
using an FT-736R and an NB-96 TNC).

However, what gear would people recommend for receiving the 38400bps FSK
packet on 2.4GHz?  The Doppler will be around +/- 50kHz, which means the IF
filtering will have to be wider than the standard 110kHz used in Symek's IFD
board, or that Doppler tracking will be necessary.

What equipment would people recommend for demodulating the 38400bps packet,
too?  The Symek TNC31 TNC fitted with a T-M38 modem?  A high-speed,
USB-connected "sound card"?

All suggestions gratefully received!



73



Chris
vk6kch
----
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
----
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



AMSAT Top AMSAT Home