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Re: Just starting out, main interest digital portable.

One more thought:
Check with Chas, w4hfz@amsat.org.  He spent a lot of time working at this and
has great notes and experience.

Good luck with it!


Howard Long wrote:

> 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.
> > ----
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> >
> ----
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