Icom ic fr3000 repeater / base - relay interface for lna

[wqzw301]

Does anyone know how or where, I can learn to use the 25 din accessary port to hook up an interface and relay for a linear low noise amplifier. 

Or even a relay to a bias tee?

I know on other transceivers without a keying switch (rca plug) it has been done.

It might be a bad idea... but i thought of it, and even if I don't do it, I have to know....

Please and thank you for any help

d

 

Edited February 26, 2022 by wqzw301

[WROZ250]

2 hours ago, wqzw301 said:

Does anyone know how or where, I can learn to use the 25 din accessary port to hook up an interface and relay for a linear low noise amplifier. 

Or even a relay to a bias tee?

I know on other transceivers without a keying switch (rca plug) it has been done.

It might be a bad idea... but i thought of it, and even if I don't do it, I have to know....

Please and thank you for any help

d

 

It looks like pin 14 might be a possibility.  Would be simple enough to test, it's basically a switch (open collector).

The 25Pin connector is generally used for connecting to a controller.

[wqzw301]

Thank you!

And do you think 25 to ground also?

[WROZ250]

3 hours ago, wqzw301 said:

Thank you!

And do you think 25 to ground also?

Well, yes.  The open collector output on Pin 14 is going to require a reference.  Basically, and since I don't know the current/voltage rating of the transistor, I'd suggest driving a 5, 10, or 12V relay (with the appropriate current limiting resistor) from Pin 13, through said resistor, through the relay coil, and then to/into pin 14.  It may be the open collector output is at the same potential as pin 25.  Does that all make sense?

I suggest reading through the manual, preferably the service manual, to discover the ratings for the open collector on pin 14.  I think the relay or even an opto-isolator is the safe way to go. 

Indeed, feed the +15V on pin 13 (again through a dropping/current limiting resistor) to the LED anode in the opti-isolator, and then the LED cathode to Pin 14 would let you drive/control almost anything safely, without fear of shorting out or over-current anything in the repeater (Think 4N28 type or similar).

[WROZ250]

OK, I was just looking at the schematic in the service manual (I have the same repeater), and the (open collector) output transistor, 'XP4311' (actually it's an IC with 2 transistors in it) on pin 14 is rated at 50V @ 100mA max.  That should be enough to drive a smaller relay coil.  However, I'd still go with an opto-isolator as there is virtually zero chance of over currenting the circuit in the repeater.

Just my opinion.

[WROZ250]

One more thing, the emitter of the (open collector) transistor is referenced to ground internally (I assume it is the same as pin 25) so you should not require that connection.  Indeed, everything on that port that has an associated ground is to the same reference, at least on the schematic.

[wqzw301]

Thank you very much!

[wqzw301]

So - Pin 14 - Open collector=off / 0 V=on
Does that mean when the transceiver transmits there is no signal from pin  - but while transmitting the pin supplies a signal to open a relay switch or close the switch depending on the type of relay?

[WROZ250]

Well, looking at the schematic, my interpretation is that it is 0 (zero) volts when on and some sort of high impedance when off.  Pin 14 is literally an open collector, meaning there is nothing connected to the collector of the transistor and, when activated, there is a low impedance path to ground.  Remember that these manuals were translated from Japanese to English and so sometimes things don't sound correct, even with major brands like Icom.

A simple (safe) test would be to take a LED and feed it 15V from Pin 13 (via a dropping resistor, Figure ~ 1K to 1.2K ohm for a typical/common LED) to the Anode and then connect the Cathode (banded end or side with the flat spot) to pin 14.

(I'd test this for you but my repeater is buried in a rack.) 

If the circuit functions as I believe it does, then the LED will be off until the transmitter is active. Worse case, it would be the reverse of that, with the LED on and then turning off when transmit is active, but I don't expect that to be the case based on the schematic.

Hope that helps...

[wqzw301]

How about a rca to an Amplifier keying relay buffer ?