780xlt point A tap

[Steve]

I know this is an old topic by now.
I need to know the proper way to connect tap point A on the 780xlt to the comm port on my computers. I know that tap point A is to the internal data slicer for LTR. The part I need to know is what kind or type cable I need to run from the tap point jack to the comm port and the wiring diagram.
Any help or assistance will be welcomed.


Thanks


Steve
KD4LCY

 

[ECPD279]

If you run a line from the tap point to pin 6 on the db-9 on the back of the radio you can use the same cable you use for programming. All you have to do is set the Trunker pin setting to DSR.

 

[pmn929]

I made the connection from tap point A, and I get around 1.5 – 2v when in trunking mode… But when I run slicer on a Motorola CC slicer shows no activity. Is the voltage just not enough for the computer I’m using?

Any help would be appreciated.

Thanks,
- Matt

 

[EricCottrell]

Hello,

You need to connect Point A to the input of a RS-232 driver and not directly to the RS-232 connector.

73 Eric

 

[Steve]

780xlt tap point A

Since I was the orginal poster, I have to ask for some help.
I have not tapped my 780xlt yet. So my question, where do I find the or a RS-232 driver in the 780xlt to tap? So for my tapping activity has been tapping the tap point and adding a jack on my other scanners.
So I am at a lost concerning the RS-232 driver location.
Sorry for the dumb question.

Steve
KD4LCY

 

[pmn929]

I think I got this to work using a TTL to RS232 converter I had made for a Motorola GPS unit. It includes a 12v to 5v converter to power the MAX232A chip.

I was surprised though at all of the mentions of using the A tap, and no mention anywhere of having to make a TTL to RS232 converter.

 

[EricCottrell]

Hello,

The A point on the 780XLT is either LTR or Motorola. To make it work for LTR you have to program a bank as LTR and do a scan with that bank active and no Motorola or EDACS bank active in Trunk mode (the word Trunk displayed). You can go out of trunk mode and do searches or scan other banks as long as you do not turn the scanner off or scan a motorola bank.

73 Eric

 

[ECPD279]

I have point A and point B tied directly to pin 6 via an SPDT toggle switch and a 1K resistor and it works like a charm.

 

[pmn929]

The lowest resistor I could find laying around was about 10k, but I don't think thats why mine wouldn't work without the RS232 converter. I guess I could try a lower value and see.

 

[pmn929]

Ok, so I guess the part where it says value isn't critical isn't true. I replaced the 10k with a 1k and it works like a champ without the rs232 driver.

- Matt