KB0P's

ILink Station Layout



The following is a layout of my repeater system and what was needed to get it on the air. The ILink system was designed by Graeme, M0CSH, and I take no credit for its success. The circuit below is only required by repeater control stations (sysops) and not by the average PC user of ILink. This information is only provided to help other amateurs link their repeater to the ILink system.



ILink Block Diagram (click on image for close-up)

The link receiver consists of a separate Hamtronics R301 VHF receiver with the Hamtronics TD-5 subaudible tone decoder. The VHF receiver is tuned to 147.240 MHz and receives the repeater activity off-air. Whenever there is activity on the 147.240 repeater COR, the repeater generates a 77 Hz subaudible tone which in turn un-mutes my link receiver.

The link transmitter consists of a separate hamtronics T304 UHF transmitter which sends link audio to the repeater via a UHF link. Whenever the link COR is active at the repeater, the 77 Hz subaudible tone is disabled to prevent a feedback loop into my link system. The UHF link is voted at the repeater and its priority is set very low. This allows any 2 meter activity to override the link which in turn gives us full control of the link system.



ILink Circuit Board Layout (click on image for close-up)

This is the layout of my iLink board. When building this board, I used screw terminals for all of my external connections. I find this dresses up the board nicely, and makes it very convenient when testing the circuit out; there is no need to solder and unsolder connections. The circuit is build on perf board which was purchased from Radio Shack. A lot of my projects are down with perf board due to the time saved in laying out a board. Also, perf board is easy to work with if there is a time when I need to make a modification to the circuit.



ILink Schematic (click on image for close-up)

The ILink circuit was designed by Graeme, M0CSH. I drew up a schematic based on the original schematic obtained from Graeme, himself. As you can see, the ILink circuit consists of 2 main components, the EPROM and the DTMF Decoder IC's. Aside from these two components, which must be specially ordered, the remainder of the components are supplied by your neighborhood Radio Shack store.

The largest hurdle to over come when building the ILink board is trying to figure out how to program the EPROM (PIC). If you decided to build your own system, one of the tools you should purchase is a PIC programmer which could cost you about $65.00. You also have the option to build your own PIC programmer, which still adds some aditional cost to the original project. The other option is to order the pre-programmed PIC from Graeme, M0CSH. You will find more information on this at his website, AACNET MANAGEMENT.


ILink Circuit Parts List

I put together a parts list and supplier for all the part which you will need to build your own ILink circuit. Again, this circuit is only required by repeater control stations (sysops) and not by the average PC user of ILink.

1 -- PIC 16F84 IC -- Digikey, p/n PIC16F84-04/P
1 -- DTMF Decoder IC -- Holmate, p/n HT9170B
1 -- 2N4401 NPN transistor -- RS, p/n 276-2058
2 -- diodes -- RS, p/n 276-1122
1 -- 4 MHZ Ceramic Resonator -- Digikey, p/n X902-ND
1 -- 3.58 MHz Ceramic Resonator -- Digikey, p/n X901-ND
1 -- 100 Ohm resistor -- RS, p/n 271-1311
1 -- 680 Ohm resistor -- RS, p/n 271-1117
1 -- 1k Ohm resistor -- RS, p/n 271-1321
1 -- 4.7K resistor -- RS, p/n 271-1330
3 -- 100K Ohm resistor -- RS, p/n 271-1347
2 -- 0.1uF capacitors -- RS, p/n 272-135
1 -- 10uF capacitor -- RS, p/n 272-1025
1 -- 5 Volt Relay -- RS, p/n 275-240
1 -- Red LED -- RS, p/n 276-041
1 -- PKG of Terminals -- RS, p/n 276-1388
1 -- 5 Volt Regulator -- RS, p/n 276-1770

Misc. Parts -- Chip Sockets, Project Box, Stand Offs, Jacks


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