Back In January Ian Robertson visited me, and I gave him 3 radios, and he gave a surprise present of an AM low-power transmitter kit.

Finally today the time had come to put it together. It went together with only a couple of small hitches of my own making.

Before powering up I didn't insert the IC chips, as I didn't want an accident with wrong voltages, short circuits etc. Everything seemed ok, so I added the ICs, set the frequency to 999 and applied power. Nothing. So I tried 909 which is supposed to be an empty channel (but there's a station there tonight). Twiddling the filter switches brought a bit of interference, so I twiddled a bit more and got a signal.

They supplied a long wire to use as an antenna, so I strung it up. They also supplied another wire for the earth, but I simply joined this to the other wire to make a longer antenna. The other end went to the antenna plug for the unit. With this and yet more twiddling it registered about s9+80dB on the comms receiver. The closest radio in the house also showed a strong carrier, so I felt it was time to proceed.

I dug out an old solid-state receiver which had suffered some kind of issue a couple of years ago. This was connected to the transmitter via the RCA connectors. When switched on MMM was immediately received without an aerial. I joined up a random wire and got 4/5. Turning up the gain control on the transmitter produced modulation. Trying a few valve radios around the house showed a lovely strong signal, so I have no doubt it should radiate to the neighbours as well. I left the FM radio tuned to a station I hadn't heard of before, VOX-FM 106.9 (community station in Wollongong, currently playing heavy metal music), and let it do its thing for a while.

Now, the problems. The gain is at full blast by about position 2 - any further does nothing. Same with the modulation control, it distorts by 2 and any further does nothing. The compression control seems to have no effect at all. I mounted the 15 volt regulator a bit too high and the case can't be fully screwed together. Lastly, the only power supply I had which has the right voltage has a square connector, but the back panel expects a round connector - so I had to leave the back off.

Overall though, I'd call this project a success. The homebrew station is currently blasting the ears off any radio in the vicinity with loud music.

(The station that I heard on 909 was a foreign-language station - it sounded like Japanese and pushed a signal strength of 6.)

Yep, a future project for me also ....

At least we have two "reasonable" stations in Melbourne, 1278 and 1377 ... except for the Funeral and Retirement/Aged Care advertising ..... and I like to play some other music ..... Pink Floyd etc..

The signal is much stronger than the Sydney stations, so it causes some interference to 2GB and 2UE, at least inside the house.

I will take a drive in the car and see how far the signal goes - I'm not expecting anything outside my block.

Then I will retune the transmitter to higher up the band - there's no local stations or anything interesting up there, so nobody will be impacted.

The frequency range is quite extensive, it has a PLL circuit, something like on a CB radio. Zero to 2295, although obviously the full range won't be available.

I found that the signal just covers my side of the block, as expected. I couldn't try the other side due to a huge amount of powerline hash over there.

The transmitter has been retuned to 1386 which appears to be unused around here. There's some moderate hash on the frequency, which has no effect in the house but will prevent neighbours from hearing my station. Currently piping 2WS over it, for the purposes of testing.


EDIT: moved the transmitter next to my jukebox computer and joined them. Now I can broadcast my collection of music to any radio in the house.