Historic link frequencies

[Persona Non Grata]

Anyone know the exact UHF (or Band 3 etc) link frequencies used by Irish pirates of old ?

Here's a few from the 1990's
174.6 Freedom 92.0
175.01 Jazz FM 89.8
426.85 Heartbeat FM 105.7
441 Pulse FM 99.4/103.2
490.1 (UHF Channel 23) Power FM 98.6
843.7 (UHF Channel 67) Anna Livia 103.8 (Legal)
844.7 (UHF Channel 67) Radio Limerick 95.0 (Legal)

In the 1980's Nova IIRC were up around 950 MHz but were asked (i.e. told) by the authorities to move down as they were about to start testing something called Eircell (mobile phone network) also there was a time around 1993 when Radio Dublin were plagued with breakthrough from a retail security companies two way radios on their link frequency during the daytime.

Anyone know of any others ?

[Albert H]

Back in the 80s - before DAB - we used Band III. It was largely empty from 175 MHz up to around 225 MHz. A favourite link frequency was 202.7 MHz - that's a 48 MHz crystal x 4 + 10.7 MHz! I also had lots of ~49 MHz radio control crystals which gave useful frequencies around 207 MHz. My receivers were (usually) a BF981 RF amp, followed by another BF981 as the mixer, feeding the 10.7 MHz IF into an "Ambit" IF board, which came as a kit for about £4.50 each if you bought a few of them. The crystal oscillator was a BSX20 Colpitts with a tuned circuit in the collector of the transistor doubling the crystal frequency, followed by another BSX20 doubling to the injection frequency. There was a further tuned circuit going into gate 2 of the mixer FET to eliminate image reception. The whole receiver went into a little tinplate box, and was happy enough in pretty close proximity to a couple of hundred Band II Watts!

My link transmitters were PLL jobs, and often included audio limiters and stereo coders in the same box. The power output of the link rig was usually a Watt or so, but on a couple of occasions, I used as much as 10 Watts.

Unfortunately, other rig builders started to use Band II for their links, and usually didn't bother with PLLs, so drifting link rigs could sometimes be a nuisance. By 1984, I'd started building only UHF links (usually around the bottom of the TV Band IV), using TV Yagis for the link aerials, and getting silly range out of just a few milliwatts!

I built a number of links for Irish stations in those days, and I'll see if I can find any records of the frequencies used.

[radionortheast]

So what was with all the radio stations in churches over there in the past?, they would of been nice and high, they seem to like to do a similar thing in American, i've often seeing videos for church radio transmitters, guessing must be part 15

[Persona Non Grata]

Think the previous comment was posted in the wrong thread but church FM transmitters in Ireland have not completely disappeared (although most have moved to 27 MHz) I recently attended a funeral in one which was using MY old frequency.

I haven't pirated in twenty years but still..........

[radionortheast]

Think the previous comment was posted in the wrong thread but church FM transmitters in Ireland have not completely disappeared (although most have moved to 27 MHz) I recently attended a funeral in one which was using MY old frequency.

I haven't pirated in twenty years but still..........

assuming that is an attempt to shut me down, not aware of any thread dedicated to churches, it was aimed at Albert he answers without been obtuse..seems to me to a lot of people on these forums get off on been rude, the same as when they use ban me from radiowaves just for the fact I was not in Ireland, able to receive some of the stations, I suppose trying to shut a person down and what they have to say as unimportant goes back a long way

[Albert H]

I've been trying to find my notes on the link frequencies I used for Ireland. I still can't find those notebooks, but I did unearth the board layout (an acetate!) for my UHF PLL exciter. I sent quite a few of those to guys in Ireland. I also supplied the receivers, too.

One station in Ireland that I supplied link gear to were paranoid about their link being "overheard" on scanners. My solution was to put their audio on a subcarrier at 45 kHz, and fill the 20 Hz - 15 kHz part of their link carrier with white noise. Anyone with a scanner tuning through their link frequency might notice their "S"-Meter rise and fall as they tuned through it, but they wouldn't hear anything other than white noise!

[Persona Non Grata]

I used to try and listen on link frequencies wherever possible as they tended to have better audio.

The use of "covert" links like you describe was probably an anti-jamming measure as some stations experienced jamming/hijacking from RTE, rival stations or bored anoraks.

[87to108]

One station in Ireland that I supplied link gear to were paranoid about their link being "overheard" on scanners. My solution was to put their audio on a subcarrier at 45 kHz, and fill the 20 Hz - 15 kHz part of their link carrier with white noise. Anyone with a scanner tuning through their link frequency might notice their "S"-Meter rise and fall as they tuned through it, but they wouldn't hear anything other than white noise!

The downside is that the link has to be significantly more powerful to achieve the same thing, as subcarrier(s) will of course be more noise prone than baseband 0-15kHz audio (filled with noise in this case).
Also the path is more critical , as multipath on the link would be more of a problem than usual. Multipath can cause crosstalk of the baseband audio (noise in this case) and subcarriers.

A more powerful link might increase the chances of affecting nearby TVs in the immediate vicinity (if linking on UHF)

what if the station is stereo?, do two separate links gets used for Left and Right, or yet another, higher and more noise prone subcarrier get used for L-R. a lot of extra complexity if stereo involved.


A casual scanner user would probably think nothing of picking up a link frequency, they are probably scanning in Narrow FM mode, a wide FM mode (for STL) will just be a distorted mess. + scanners are often prone at picking up 'images' of strong FM stations on other frequencies outside Band II anyway (especiallly common handheld ones, desktop ones would I'd expect have better performance in this regard).
Other people, who might be trying to find the studio of a station, would often have other intelligence about where it was located anyway

[Albert H]

You're partially right. Using the subcarrier audio system required about 4 dB more S/N ratio for the same quietening carrier. This can be achieved by increasing TX power or by making a better receiver.

The reasons given for the use of this system included trying to fool COMREG!

[Persona Non Grata]

I'd imagine COMREG would have spectrum displays on their receieving gear so as they scanned the band they would be aware *something* was there and wouldn't be fooled by white noise even if they couldn't immediately discern actual audio.

But a lot could depend on timeframe. Back in the pre-COMREG days the old DoC investigation branch were poorly resourced and may only have had consumer level scanners and wotnot (some of them probably had amatuer radio licences) ?

[TheBMG]

At one stage about ten years ago both 98FM and FM104 were using 50mhz links from their OB units. Brutal but effective.

[87to108]

844.7 (UHF Channel 67) Radio Limerick 95.0 (Legal)

abandoned UHF STL 'beam' (co-ax hanging loose) and FM receive (top of pole) visible many years later:

https://www.google.com/maps/@52.6612716 ... 384!8i8192

[87to108]

Recently had a listen to a recording of the original pirate Q102 Dublin from 1985 on pirate.ie. Just curious I threw in the announced address (3 Upper Mount Street) to Streetview.... just to see how the building looks... I saw that older Streetviews (up to November 2022) show what I assume was the STL (Studio to Transmitter Link) antenna used by the station - a 12-element vertical polarised UHF Yagi... (its definitely not for TV reception if anyone thinks it is... )

https://www.google.com/maps/place/3+Mou ... FQAw%3D%3D

But the most recent view (Oct 2024) shows it now gone, so sadly it didn't manage to survive being up for 40 years!! (assuming it was the actual STL - anyone comment to confirm?)

It seems the studio was there only a short time as the following year in 1986, per info online (DX Archive) it has a new address just a few doors away

[mixfm]

we used to use band 1. 58 mhz in birmingham in the 90s with a mini yagi aerial on the balcony. used to get great resuilts 5 - 7 miles line of sight. the every now & then change the link freq to a different one to keep them on there toes.l.. good old days

[Persona Non Grata]

TTTR's Harold's Cross studios had STL antennae for years/decades after they closed but gone now AFaIK

Radio Dublin had their motorway light tower mast (sans aerials) at Vincent's Street West for many years after departing that locale as well.

Wonder what the new owners did with their BIG washing line pole ?

[reverend]

Back in the 80s - before DAB - we used Band III. It was largely empty from 175 MHz up to around 225 MHz.

Band III is still useable if you can slide in-between the DAB multiplexes but it's quite dirty. One other problem with Band III is making sure that there are no conflicts with the second harmonic of the Band II frequencies. Albert's link frequency of 202.7 MHz for example, wouldn't work very well with transmitters on or around 101-102 MHz as the receiver would be swamped by the second harmonic of the transmitter and no amount of filtering is really going to fix that.

I've used Band III links a few times. Once across central London: a 1 Watt TX feeding CT100 coax to a 3 element antenna on a rooftop and a similar 3 element antenna at the receiver. Managed a distance if over 4 miles with (almost) fully quieting stereo, well quiet enough that the modulation drowned out any residual noise. And that was over the rooftops of Pimlico and South Kensington. It's definitely easier to hide Band III antennas than Band I.

Around 950 MHz is where most USA radio stations put their STL links. FCC Part 72.502 allows STL links from 944 - 952 MHz and I believe they can extend above this too. There is therefore a lot of link gear for these frequencies (I picked up a nice 10W STL, receiver and antennas for around $100) but as the frequencies are used for 3G/4G in Europe, it's not really much use outside the Americas.

I don't know about Ireland, but there are various frequency lists/scans online for London and for Band I, the following frequencies were once in use:

54.25 Dem Radyo
54.90 Rush FM
55.75 Shine
56.30 Mega
56.70 Point Blank
56.90 Mystic
57.00 Unique
57.40 [unid]
58.20 [unid]
58.70 Unique
59.00 Unknown FM
60.50 Nigeria
60.70 Flex
61.30 [unid]
61.70 [unid]
64.45 House
67.00 [unid]

It's an old list and many of the stations are no longer around, but it shows just how busy the band once was.

[reverend]

One station in Ireland that I supplied link gear to were paranoid about their link being "overheard" on scanners. My solution was to put their audio on a subcarrier at 45 kHz, and fill the 20 Hz - 15 kHz part of their link carrier with white noise. Anyone with a scanner tuning through their link frequency might notice their "S"-Meter rise and fall as they tuned through it, but they wouldn't hear anything other than white noise!

The circuit below does something similar. It was 're-engineered' from a spy transmitter that was discovered in an Opec office. It produces a low frequency 'buzz' which modulates the transmitter, and the audio is then placed on a sub-carrier much higher in frequency so that a normal receiver wouldn't hear it. The idea was that it would sound like a TV transmitter if received on a normal receiver. Ingenious people these spies...!

opec_circuit.png

[Persona Non Grata]

Recently had a listen to a recording of the original pirate Q102 Dublin from 1985 on pirate.ie. Just curious I threw in the announced address (3 Upper Mount Street) to Streetview.... just to see how the building looks... I saw that older Streetviews (up to November 2022) show what I assume was the STL (Studio to Transmitter Link) antenna used by the station

It seems the studio was there only a short time as the following year in 1986, per info online (DX Archive) it has a new address just a few doors away

Q102 did move to a different address in the same street. 98FM (the licenced station) also used to broadcast from the same street.

[teckniqs]

54.25 Dem Radyo
54.90 Rush FM
55.75 Shine
56.30 Mega
56.70 Point Blank
56.90 Mystic
57.00 Unique
57.40 [unid]
58.20 [unid]
58.70 Unique
59.00 Unknown FM
60.50 Nigeria
60.70 Flex
61.30 [unid]
61.70 [unid]
64.45 House
67.00 [unid]

As far as I remember 57.4 was De Ja and 61.3 was Kool FM.

Here is a video I recorded back in 2010 with a scanner on the Band 1 frequencies, stood right by Charlton Althletic stadium and as you can see there was a lot on there back then. (including De Ja sprogging up the band, you can also hear 57.4 on numerous other freqs)
....I haven't tried checking again in London for many years but I have noticed I can no longer ever hear any London band 1 STLs any longer when up any hills to the south (when a few years ago you could get quite a few, now zilch!)

[87to108]

Here is a video I recorded back in 2010 with a scanner on the Band 1 frequencies, stood right by Charlton Althletic stadium and as you can see there was a lot on there back then. (including De Ja sprogging up the band, you can also hear 57.4 on numerous other freqs)
....I haven't tried checking again in London for many years but I have noticed I can no longer ever hear any London band 1 STLs any longer when up any hills to the south (when a few years ago you could get quite a few, now zilch!)

At the start of the video was that an actual transmission (rather than a receiver generated image of something higher) , AND slightly below 52MHz ?? seriously looking for trouble going on such a frequency!

(the posts about London may be more appropriate for the London section of the forum, they may get missed by some there with an interest in this, hope they find the above anyway)