[OZAPRS] Re: Re: VHF to HF Gateway for portable use ?

Tony Hunt wavetel at internode.on.net
Thu Dec 11 13:22:03 EST 2008


Andrew this is a good question.. The problem is that different TNCs have
different text formats output in converse mode.. Also mobile motorbike
station A transmits a frame and it would then be put into the next TNC  with
the callsign being transmitted from the 4WD as its own callsign with the
posit of the motor bike slung onto it  with the motor bikes callsign stuck
at the beginging of the frame along with the rest of the data and path. It
would be unlikely to show up as a proper posit or even a 3rd party frame as
the formatting would not be right. For sure the info would goto air etc but
it would be discarded as a invalid frame by the servers and the clients
gating it.

Ive often toyed with the idea of putting 2 TNCs back to back in KISS mode
but never tried it. This might have something.,. KISS mode is pretty much
universal.. What this would do if it worked is just translate the frame from
one speed (on air) on one frequency to another speed (on air) on another
frequency .

What you really need to do is have the motor bike with callsign A and the
support 4WD as a gateway with callsign B. The motor bike could beacon via
the usual VHF path ideally and the Gateway could be setup to translate this
to the HF path recomended. This is pretty exeptional and you wouldnt want to
run it in the metro area.
However if you put 2 TNCs back to back in KISS mode you can forget all this.
The paths callsign and frames would be solely determined from the motorbike.
So the motorbike would have to run the HF paths and setups on VHF trackers
at 1200Bd then the VHF TNC in the 4WD would pipe it across the KISS serial
link at say 9600Bd and the HF TNC would put it out onto 30m at 300Bd with
the correct tones and TXdelays etc.

The legalities are another thing with all this.
If you want to look at the motor bike and the 4wd being connected via a ext
cord then you could say they are the same station..

Once again Ive never seen this actually work.. Maybee someones tried it and
can tell us why it wont work.. I would love to know more..

Tony Hunt  VK5AH

----- Original Message ----- 
> Date: Wed, 10 Dec 2008 17:54:25 +1300
> From: Andrew Errington <a.errington at lancaster.ac.uk>
> Subject: Re: [OZAPRS] VHF to HF Gateway for portable use ?
> To: Australian APRS Users <ozaprs at aprs.net.au>
> Message-ID: <200812101754.25540.a.errington at lancaster.ac.uk>
> Content-Type: text/plain;  charset="iso-8859-1"
>
> I've been thinking about this over the weekend.
>
> Let's say you had two TNCs (single channel, simple design) and you placed
them
> both in CONV mode.  Each TNC is connected to a radio- one is HF, one is
VHF-
> and the TNC is configured with the appropriate on-air settings (baud rate,
> tones, etc.).  Now, on the serial port you hook up data in from one TNC to
> data out from the other, and vice-versa (and GND of course).  Now you've
got
> a VHF to HF gateway.  Wouldn't it Just Work?  If not, why not?  What would
be
> the simplest alternative that would work?
>
> The data path would be:
>
> bike tracker VHF Tx -> 4x4 VHF Rx -> TNC 1 AF in -> TNC 1 serial out ->
TNC 2
> serial in -> TNC 2 AF out -> 4x4 HF Tx
>
> Obviously there is a reverse path, but for APRS positioning only this is
not
> required.
>
> The reason for asking is that I have built one of Bob Ball's (WB8WGA)
> PIC-based TNC, which is a cheap platform for this kind of experiment.  The
> initial drawback is that it doesn't support HF baud rate or tones, but the
> firmware is available and hackable.
>
> 73,
>
> Andrew
> ZL3AME
>
> On Saturday 06 December 2008 13:25, Geoff wrote:
> > Folks,
> >
> >
> >
> > A few of the blokes from the Blue Mountains ARC are planning a trip next
> > year out to Cameron Corner (Corner of NSW, QLD and SA).
> >
> >
> >
> > There are a couple of motorbikes in the convoy, and what they were
looking
> > at doing was to run APRS on the bikes (VHF) and relay their position via
a
> > mobile VHF to HF gateway in one of the support 4x4 vehicles.
> >
> >
> >
> > Does anyone know of an easy way to achieve a compact gateway?   The only
> > thing I can think of at the moment is to back-to-back two TNC's, or have
a
> > laptop in the vehicle running an APRS client app that supports
gatewaying.
> > Of course the bike posits would be sent at HF rates whilst this gateway
> > operation was being conducted..
> >
> >
> >
> > Interested in any ideas I can pass back to the guys..
> >
> >
> >
> > Cheers,
> >
> > Geoff   VK2XJG
> >
> > _______________________________________________
> > Ozaprs mailing list
> > Ozaprs at aprs.net.au
> > http://aprs.net.au/mailman/listinfo/ozaprs
>
>
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> End of Ozaprs Digest, Vol 12, Issue 11
> **************************************
>


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