[OZAPRS] VHF to HF Gateway for portable use ?

Andrew Errington a.errington at lancaster.ac.uk
Wed Dec 10 15:54:25 EST 2008


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
>
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