UHF/VHF Cross Link for Emergency Use

This is an emergency self supplied, repeater system. It receives from vhf band and simultaneously transmits on the uhf band.
The box contains:

Battery Charger

There is 220--18-0-18v 15w transformer in the box. I have a couple of these so i used it, if you are going to buy new one single 15v 15w is better.
Whole system needs to 100mA during stand by and 1.7A during RX-TX.
I had 2 choices, one is putting a small 12v 3or4 A SMPS into the box and building a battery charger circuit. The second one is making a trickle charger and let battery to supply system even if there is an AC.
This is cheaper and easier. Normally, charge voltage is 13.2V, if want to increse it, you can add diode between 7812's ground pin and ground.
Each 1n4007 will add it to 0.6v. 10W Resistor limits charge current.

DC-DC Converter

Aselsan Radios are mil-spec, so they can work with 12v, however 7.4v is better for both radios and control circuit.
Linear regulators are cheap and easy to use, unfortunately they produce high amount of heat and waste valueable power.
I used my old LM2576 DC-DC converter board that can supply up to 2.85A(3A in theory) with variable voltage.
Firstly, i used a big heatsink however, i couldn't feel any heat even when i remove heatsink. So, a small plate/heatsink is ok.

DTMF Link Controller

Is Here!

Aselsan Handheld Radios

These are 4000 Series, military radios with pll controlled, 99 channel and built-in ctcss encoder-decoder.
I used these because they are old version so cheap and we can find them in junkyards easily.
On the other hand, they are very robust, battery friendly :) and they can work in a large temperature range.
They have lots of extra features like modem, remote programming, remote channel change, remote turn-on/turn-off, sending message etc.
Unfortunately, we can't use that features because Aselsan does not provide their special software for amateur use.
Aselsan radios are made in Türkiye.
I opened both radio's case and desoldered a channel encoder and soldered a wire to LSB hole. So, i can use 2 channels.
If you solder 2 wires you can use 4 ch. If you solder 3, you'll get 8 and if you solder 4 you can use 15ch+1 seach.
On RX radio I soldered a second wire for SQL output. Then i closed the radios. Mic, PTT, RX audio, TX audio connections made on headset connector.
I connected them to computer and programmed first two channels with my link rx-tx frequencies. I set CTCSS on by default on rx radio and set power level to high at default on tx radio.

Diplexer

Is Here!