KJ6KO Beacon Construction.
The beacons are a very simple configuration. The 2m beacon is an old Icom 245 with memory keyer programmed with the beacon's message.
The IC-245 is running about 4W thru two directional couplers that take a small portion of the transmitted signal and run it to the 432 and 1296 transverters. The remaining 2m signal then passes thru an 80W amplifier cut back to about 40W.
The 432 transverter has an output of about 5W into a TE Systems 180W amp running at around 100W. The relays have been removed from the TE amp and it is "locked" in the TX mode.
The 1296 transverter has about 2W output into a homebrew version of the DEM 18W amp running at around 10W.
Since the old IC-245 reverts back to 144.00 upon a power failure, there is a battery backup and remote "on/off" capabilities in the case of an unforseen, long power outage.
Here is a rough block diagram of the setup.
I chose this route since it is usually cheaper and easier to find an old all mode radio at a swap than to find the time to build a beacon from scratch.
Using an FM radio for a beacon.
This sounds like a good idea?? Well, the problem of using an FM radio and simply keying the PTT is that it will have terrible "key clicks" and "chirping". A solution I found was with my 222 beacon radio which is a Midland 13-509. By locking the radio in the TX mode and keying a low level stage of the PA cured the chirping, but there were still key clicks that were over 100Khz wide! The early stage of the PA in the 13-509 has a separate power lead that made it easy and by adding a capacitor across the keying circuit completely eliminated the problem. I can now only hear clicks about 10Khz away with an S9+40 signal. See the circuit below. The actual component values will vary with each application and will take a little experimenting to get it right.
Another problem is with power out on these old FM rigs. Most of them used a large resistor to lower the collector voltage and drop the output to around 1W. In my case, I needed about 7W. Changing the resistor resulted in SEVERE heat in the resistor. I solved the problem by leaving the radio in the HIGH power mode and installing an attenuator in between two low level stages of the PA before the keyed stage. This worked perfect. The 13-509 draws about 3 amps at 7W with virtually no heat and drives a converted 160 Mhz amp to 35W output. Total system current is around 5A!
Your beacon should NOT look like this.....................................THIS is a little better!!......HI HI.