[aprssig] Radio/GPS power control

J. Lance Cotton joe at lightningflash.net
Fri Jul 23 12:53:57 EDT 2004

Scott Miller wrote:

> The radio power control output function has been implemented in the latest
> OpenTracker firmware.  It'll now send a signal (5 volts, 25 ma max) from 0
> to 255 seconds prior to transmitting to allow an external relay or other
> switching device to turn on the radio.

How does it handle channel-busy situations? My empirical evidence from the 
TT3 was that if it turned on the relay and the channel was busy for n 
seconds, where n>~5, it would keep the relay on, but not transmit when the 
channel was clear, until the next scheduled TX time. This was with 
SmartBeacon and corner pegging on, so that may have made Byon's algorithm 

Does the OT keep the relay on until it finally get the posit out? Does the 
OT keep updating the position packet to the latest position/speed while the 
channel is busy (the TT does)?

> I'm thinking about producing a power control module that'd plug into the
> OpenTracker and handle the switching, with a couple of 25-amp APPs for power
> input and output.  Has anyone used the PCB-mount APP pins?  Any comments on
> their durability?  I'm worried about the pins flexing and pulling up traces.

While perhaps harder to kit, a good strain relief is very important. I find 
that a cheap way is to solder your cables as normal, and then drill two 
holes in the PCB and use a 4" zip-tie to cinch the cables down to the PCB. 
Two zip-ties in a row is even better.

> Scott
> N1VG

J. Lance Cotton, KJ5O
joe at lightningflash.net

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