Comments for "FM Broadcast Band Transmitter"

6th June 2008 15:58

Alan Yates wrote...


I haven't really played with this transmitter for years.

I still have it of course, I might find it and dig it out over the long weekend to sketch the circuit diagram for you. It isn't very exotic, just an oscillator and amplifier chain. If I was to build it again there are a few things I'd change, in particular I'd use toroidal RFCs instead of commercial chokes and probably a better oscillator coil more suited to VHF. I'd also consider a lower frequency VFO and multiplication chain instead of having the VFO run at the TX frequency.



4th June 2008 20:28

Bert wrote ...


I have a request: can you please provide us with some information on the experiments and improvements you have done on this transmitter? And don't forget to post some schematics too!

All the best.

30th January 2008 14:05

Alan Yates wrote...


Ah, the things we do in our youth... Although I never did anything especially evil like deliberately blocking a commercial station, I did make a few "enemies" in my CB days.

At one point someone who shall remain nameless put a jammer near my site, tuned up to about 27.154 MHz, producing quite an annoying 1 kHz S9 signal on my radio right on the SSB call channel. It took me only hours to find it, which disappointed them no end, they were hoping to keep it running for weeks by regularly changing the batteries.


30th January 2008 13:35

Daryl wrote ...

Hi Alan,

I enjoy reading about other peoples pirate days as I have been there too.

confining my piracy to the FM broadcast bands, built countless transmitters back then and thought I would quickly tell you where I ended up in my achievements with it in the end.

I initially started with small low powered TXs and antennas like 1/4 wave groundplanes and J poles with 5 watt transmitters made out of second hand bits from VHF radios. I then got an old FM 92 I think it was and made a 30 or so watt PA. Then I made a 4 element yagi with a gamma match which worked very well (PVC support and aluminium tube adjustible telescoping sections). Got out 40km and I was in a very flat area. Then I moved from my home town to a city with a population about 5 to 6 times larger but was in a gully. However I put in a petition to be moved to a house I knew was available that was up on a nice hill (250 + feet above sea level). Excellent views for miles away from and over the city. I made another 4 element yagi and 25 watt PA which I eventually used to drive an MRF455 amp. which being a HF transistor has much less gain on the FM broadcast band (I think a bit under 6 dB). Don't worry I had a 7 element low pass filter built into it!). So I was getting nearly 80W into the yagi but only in mono.

There is also a long story about, in the town I used to live, me having a squabble with the local community radio station suspending my programme over a politically driven disagreement with me and another finnancial member which was very unreasonable so I went home and TXed over them intermittently and this reached most of their sponsors in the main street which resulted in some very dirty looks toward me from some of the people on the board of the station as they highly suspected me but couldn't prove it!

I, in moving here, was not allowed membership and a show at this cities station as I think they were in correspondence with one another (both places only being 50Km apart) and they must have told the management of the station here, knowing where I moved.

I therefore waited a few months and did it to them too (from my very high location) just to make a point, intermittently cutting them out over 70% of the town with loud guitar riffs at intermittent intervals and very peculiar music snippets. I only did this for a few weeks in a very unpredictable fashion and stopped to avoid being busted and then didn't do much FM BCBing unless the antenna was turned away from the main part of the town and I was running 1 watt or less for experementing on QRP. My yagi had very high front to back.

Anyway I hope you have got a degree of entertainment out of my personal pirating story!

Best Regards,

Daryl :-)

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