NASA Navtex modification

[wetstuff]

Okay, here's a challenge for any electrical types out there .....

NASA's Navtex engine is fed from you battery and has three output wires - one common wire and one for each Navtex frequency.

Now this suggests to me that there is no switch to flick to get the engine to listen to the different frequencies - so it must be listening to both at the same time.

If this is the case then both frequencies should be able to be listened to by an external device simultaneously. Has anybody tested this / can anybody test this?

If this does not happen how does the frequency selection take place without some sort of switch ( unless continuity of circuit acts as a switch of sorts)?

Also, woul dit be possible to modify the engine so that both frequencies were listened to at the same time and output at the same time?

All the best,

John

 

[nimbusgb]

Nope!

One common wire, one output and one input. The associated software is used to tell the box at what time to listen to which frequency.

Nasa pc engine manual

 

[wetstuff]

Sorry, should have said I have the Raymarine version - so no software control, output selection is from the choice of wires /forums/images/graemlins/smile.gif

John

 

[nimbusgb]

Raymarine version?

 

[wetstuff]

Yep - the "Raymarine" version has bare wire ends for connecting to any NMEA capable receiver ( chart plotter) rather than a 9 pin D plug for a PC.

Good this challenge, innit? /forums/images/graemlins/smile.gif

 

[crossbones]

The "raymarine version" of the nasa pc navtex cannot receive both frequencies at the same time. The black wire is the data output. In normal use ( with the red wire disconnected) it is listening on the international frequency. (518 Khz). Connect the red wire to supply negative and it listens to the national frequency. (490 Khz).
The ordinary pc navex has an internal clock and can be programmed to swap frequencies at specific times of day and records messages internally.

 

[wetstuff]

Ta for that.

Real shame they don't do a simultaneous version. Mind you at their prices getting two is still probably cheaper than the competition.

Cheers,

John