Stations that were linked over fm or relayed how was it done

[radionortheast]

I remember hearing this was done, were a station had a little 0.5w, 1w, in the fm band that was linked to the main transmitter. I also saw this been done by someone in another country, they only had the main transmitter in a tree outside, suppose thats just how they frost themselves.

I think I remember reading the wakefield transmitter for dream was fed from the leeds tx on 107.8, seemed quite a close channel spacing to do that. When the relay was in York it was too far away to do this, they used a 15w link, some were outside of the fm band which really popped, was maybe to far for away for stereo. Relays didn’t happen up north, I don’t remember them happening other than that, I think there were some stations in London that had relays, wonder how it worked. I think broadcast receievers are expensive can’t see how they could be used, if you had a penthouse you could have one.

With licenced stations the whole feeding from another fm transmitter is rare, chance of it been interupted by a foreign station, maybe get lucky have bailando paradisio coming across all radio channels, they could get hijacked, like the southern tv hijacking. There was rumour if the feeds went down for a national station, they maybe had a back up, were they get them over fm the nearest transmitter, remember hearing something about there been a broadcast chain. That maybe the reason even those these frequencies could be used, they had to kept clear, maybe just rumour or rumour has it.

I suppose usually a uhf link would be directional, so perhaps would not beable to be picked up from two different locations, unless they were in the same direction, or of the phouse lol. Seems like the link is in horizontal mode which helps from overload from the ding dong, the main tx is in vertical…suppose makes it interesting is if they are both in vertical at close frequencies. I was thinking if there some were high up, they would likely receieve a good signal from the other transmitter but the receive aerial been in horizontal would away to combat it.

[EFR]

I have done some linking on FM back in the day, just trow one cheap portable radio to the second transmitter site, listening main transmitter.

Second transmitter output has to be clean and about 1-2Mhz is enough between them.

[Albert H]

My very earliest links were done using a cheap broadcast tuner modified to go below Band II. We used about ½W on 82.2 MHz to link from our studio to the main transmitter site. The receiver board I used was one sold cheaply by "Henry's Radio" in London's Edgware Road. It had a "tuned" lamp output, which I used to drive a little relay, and turn on the supply to the main rig.

The transmitter fed a dipole in the loft above the studio, and the main site had a dipole in the roof of the garage that housed our main output medium Wave transmitter. The link system worked flawlessly for the two years that we ran from that site, and probably only cost about £10 to build at 1972 prices!

[shuffy]

During the 80's & 90's there were 2 stations in the Stockport area which used links in, or near, the FM band. The first, in late 1984, used a 5W VFO rig on (approximately) 105.8MHz which at various times (although never simultaneously as per the original plan) was feeding a rig in the lower half of Band II on a high point 5 miles away from the studio, and an AM rig just under a mile away. The link receivers were car radios. Probably the highest quality receivers commonly available at the time. Back then the FM band didn't contain any broadcast stations above 105MHz so the link stuck out like a sore thumb and was easily audible on a normal FM radio over a fair chunk of south Manchester. Distribution of the signal was the main priority but obfuscation of the link wasn't really possible due to limited availability of specialist kit and test equipment. Miraculously, the studio itself wasn't raided.

The second one, about a decade later was just above the top of Band II around 110MHz between suburbs just over 2 miles apart. The RF parts were purpose built based on circuits culled from domestic receivers and a 10.7Mhz IF strip kit (ambit?) which could fire up the main rig via a relay. Antennas were, if memory serves, a dipole and a basic domestic 3 element FM Yagi both horizontally polarized. This station did get raided but not for linking in the air band specifically - he'd had a falling out with someone from another station and let's say things went downhill after that.

Both these arrangements worked OK with the main (Band II) rigs running between 50 and 100W in close proximity to the link RX and in the case of the 2nd station, albeit the weaker of the 2, less than 5MHz difference between the link and broadcast frequencies.

[Persona Non Grata]

Aitband links are a pretty terrible idea. Frequencies which appears empty on the ground may still be carrying navigation beacons audible to aircraft 10km up in the sky

That said I know of a licenced station which was using them for outside broadcast links back in the early 1990's. The station in question later lost their licence (for other reasons) but remained on air for a few years as a pirate although during their licenced phase used to scream and b1tch to the authorities about other pirates on their turf

Complete scumbag behaviour !

Incidentally back in the day when the VHF allocations were being divided up I wonder who the hell decided it was a good idea to have a safety of life navigation allocation right next door to a high power broadcasting band in the first place ?

[Albert H]

Actually, PNG, it's not too bad an idea. The predominent "unintended" outputs from broadcast rigs tend to be harmonics, the second harmonic output will fall way up in Band III (175 - 216 MHz), so would be very unlikely to cause intereference to aircraft band services.

These days, the first harmonic outputs I see from Band II rigs tend to be odd ones - third, fifth and so on. This is because the majority of PAs I see nowadays aren't "single-ended" types - they're usually FETs in parallel (or the Motorola "Gemini" FETs which are pairs). The even harmonics tend to be nulled. The big advantage of this approach is that the output filter requirements become less stringent, and so can have lower insertion loss.

[shuffy]

Actually, PNG, it's not too bad an idea.

Albert is of course talking about the band allocations but in terms of linking in the air band, agree 100% it's a bad idea. Studio was 2 miles from the airport too, and I think right under the flight path! I think the guy did it that way as he wouldn't have to build anything "exotic" for his link system, it would basically be Band II kit with minimal modification. Wonder why he didn't go "low" though.

[Albert H]

Way back - late 70s and early 80s - the Gas Board used to use just below Band II for their mobile radios! I remember (vaguely) one of Dawson's London stations in that period relaying the Gas Board for a day or two!!

[reverend]

Back in summer '87 three of the local pirates joined force. All were previously on/around 105 MHz but it was found that more spacing was needed between the RX and TX frequency otherwise the receivers at the relay sites were overloaded by the TX. The 'feed' station changed frequency to 102.3 MHz, and the two relays were on 105.3 and 105.5. TX power at each site was around 40 Watts. It was only done the once, but provided really good coverage of the city and surrounding areas.

[pirateaddict]

Or8 reverend...Were these in t'sheffield?
I still can't believe i missed the early pirates in Sheffield...87 I'd have been 13-14 years old and was into the recording the charts on a Sunday..Used to tune up n down the dial but realised that there wasn't anything above 105 so very rarely went there at all... Wasn't tuning around at the right time i now realise
February 86 started recording the charts and only realised in mid march that radio 1 went on radio 2 fm on a Sunday for the charts lol... Recording MW was great

[shuffy]

only realised in mid march that radio 1 went on radio 2 fm on a Sunday for the charts lol...

They'd been doing that since the 70s (Now THAT was a simulcast)! Hmm. God I'm old.

[shuffy]

Way back - late 70s and early 80s - the Gas Board used to use just below Band II for their mobile radios! I remember (vaguely) one of Dawson's London stations in that period relaying the Gas Board for a day or two!!

In the 80s, there was a local pirate who linked in Band III - occasionally you could hear PMR breakthrough as their rig was near a well known PMR site for a while. This station's link was also jammed by a ham who'd discovered the frequency, he used to go over the top of them doing silly voices and threatening to continue to jam them unless they played whatever song he wanted

Probably late 70's / early 80's, I used to hear gas board mobiles at the top end of Band II, 107 and up. If I tuned right down the bottom of the band, I could hear a local taxi firm, using what sounded like AM IIRC. I never quite worked out the PMR allocations around Band II but I suppose I was quite young and probably wouldn't have known who to ask or where to get band plans from.