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Re: Just starting out, main interest digital portable.



Hi Dale,

Firstly apologies for the long reply. You know how it is... I just like to
be thorough.

You may have already had some replies to your question.

A *portable* and *digital* station is quite a tall order IMHO, but a great
project nonetheless.

One of the questions I often ask is what equipment do you already have?

Another question in your case is how portable is portable? If you're looking
for a generous laptop-case sized scenario, you could just make it. So I'll
use that as a starting point. For portable ops you'll probably want to
consider reducing the number of 'bits' you need, like the use of integrated
TNCs/Modems either in the rig or written in software on the PC.

You said you were just starting out, so I'll make an assumption that you
have nothing (probably a bad assumption but you have to start somewhere).

Remember I'm just giving you suggestions... there's always more than one way
to skin a cat!

Essentially you need four groups of items:

(a) a computer & software
(b) a rig & PSU
(c) something between the computer and the rig
(d) an antenna

Well (a) is largely upto yourself - a laptop PC or Mac. It doesn't need to
be the latest all singing all dancing unit. But size may be important to you
(as they say) when you've got all the other junk which I'll describe later.
Consider a computer which has _real_ serial port(s) for rig doppler tuning
and external TNC control (if necessary). USB just means another piece of
junk and expense to provide serial capability. No radios currently have a
USB interface. Some tiny new computers (ie a Vaio) only have USB, or need a
docking station to provide serial interfaces. You can buy PCMCIA card single
and dual serial ports... but they're expensive, and similarly yet more junk
for your portable station.

If you want to be able to use a rig sans TNC/Modem, a PC with Linux will cut
down size as I understand the software has the Modem built in using the
sound card. This depends on whether or not you like Linux. Getting Linux to
work on a laptop can be a lesson in patience in my experience, especially
the GUI. I don't know if the Linux modem drivers work with any Pacsat
suites, but I presume that they do. Please no brikbats about
Microsoft/Mac/Linux!!! I'm not aware of any software modems which do 9600bps
reliably under Windows or on the Mac, and is compatible with programs such
as Wisp, but someone may know something I don't. With Windows and Mac you'll
probably therefore need a Modem/TNC either separately (see (c)) or in the
rig (see (b)).

Under Windows, Wisp is the software most use. It performs predictions and
controls TNCs and radio frequencies for doppler compensation. The good news
for portable operation is that because Wisp does most of the stuff for you,
you can concentrate pointing your antenna in the right direction. Indeed,
you'll likely end up being simply a rotator during the pass.

(b) is a bit tough for portable use. You can't use a TH-D7 for two-way
satellite communications. It will receive though. You *can* use a TM-D700.
What's great about the TM-D700 and TH-D7 is that they have an inbuilt 9600
modem & TNC. Add to the TM-D700 a 12V gel cell and you've got your rig and
PSU sorted out. The TM-D700 and TH-D7 can de used for the analog FM sats if
you fancy a change of mode. But they can't be used for the linear
transponder sats. The TM-D700 also has more than sufficient power for the
uplink. You're restricted to 9600 sats on the TM-D700. There's nearly no
1200bps AFSK satellite activity. Any 1200bps activity there is is BPSK which
the TM-D700 won't support at all. Another downside is that there's no DCD
indication other than squelch breaking on a TM-D700.

I think you should rule out HT's, both for uplink power requirements and
because you can't easily get 9600 in/out of any of them for full duplex
working.

Alternatively, a 'normal' radio can be used, but then you'll have to think
of (a) [Linux/software] or (c) [external TNC]. Power as well as size is
important when choosing a portable satellite unit. You may struggle on your
uplink probably struggle with 10W out. Dual band 2/70 FM only is cheap and
small, but remember you really want VU full duplex and duplex 9600
capability. If the rig is modern and will do simultaneous dual receive, or
says it'll transmit on one band while receiving on the other, you're
probably in business.

At the other end of the scale, in the multimode full duplex category,
there's nothing there right now which could be considered small enough to be
'portable' IMHO. I have taken my FT-847 out portable with a battery pack,
and it's not very portable. The closest I've got yet to portable working is
a 706MkIIG, a handheld RX and a gel cell, but then you'll have trouble
extracting 9600 out of a handheld RX - maybe it would work set to WFM, but
then that may be _way_ too wide. The benefit of this set up is that you can
work _all_ the analog sats with it.

Digital and portable - I'd say a TM-D700 and a battery pack.

(c) If you've got a built in TNC/Modem in the rig, or are running a software
TNC/Modem, all you need here is cable(s).

If, however, that's not the case, things get a bit hairy both from all that
additional junk you've got (TNC/Modems and extra cables) and the size of
your 'portable' station. Add to that the setup time and a quick 15 minute
QSO can take half an hour to set up for.

There are some quite small TNCs about which connect directly into serial and
parallel ports.

(d) Only one suggestion here - an Arrow. I use two of these phased for a
permanent station and they work fine. I have to use two because I can't
twist the antenna's boom from 120' away to correct for polarisation
mismatch. Hand held and it's easy with a bit of practice and diligent S
meter readings. The version they sell with the integrated duplexer only
supports up to 10W though. You might want to consider a heavier duty unit.
But be careful you don't fry yourself... 50W would be more than enough at
the antenna for your uplink.

Omnis really will frustrate you because of their performance.

In conclusion, my personal choice for digital portable use would be:
TM-D700, 12V 7AH Gel Cell, laptop PC with _real_ serial port running Windows
and Wisp, Arrow antenna with duplexer. A compass is always handy too. Make
sure your PC clock is always accurate if you're dependent on it for the
doppler tracking and interactive predictions from Wisp.

Just a suggestion of course - like I said there's more than one way to skin
a cat!

Sorry for the long note.

73 Howard G6LVB

----- Original Message -----
From: "Dale Coleman" <kf4sir@earthlink.net>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, October 03, 2000 12:27 PM
Subject: [amsat-bb] Just starting out, main interest digital portable.


> Hi all, I'm just starting out in my quest to learn more about satellite
> operations.
>
> My main interest is in the digital and portable area and I'm trying to
> figure out what equipment would be required.
>
> I'm in the process of joining AMSAT-NA and hope to get the AMSAT-NA
Digital
> Satellite Guide soon.
>
> While I'm waiting for it to come in does anybody have some web links that
> might help?
>
> Thanks, Dale KF4SIR
> --
> Dale Coleman
> kf4sir@earthlink.net
> Check out my ham radio web site:
> http://psk31relay.net
> use PSK31 to relay messages.
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>

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