horizontally polarised FM pirates

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87to108
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horizontally polarised FM pirates

Post by 87to108 » Tue Jun 07, 2022 7:45 pm

Must have been very unusual for an FM pirate to use horizontal polarisation (instead of vertical or even mixed H and V)
but from this footage, Andromeda broadcasting to Manchester, in the early 1980s, did so:



though way back then, very few car radios had FM anyway? (where Vertical polarisation is important) , and many people were using fixed horizontal polarised receive aerials at home (for BBC FM)

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Re: horizontally polarised FM pirates

Post by jvok » Tue Jun 07, 2022 8:32 pm

Im more interested to know how they got the coverage they claimed on only 1 watt. A high site is great and all but still doesn't explain how they manage 50 miles coverage.

Quieter band back then I guess?

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Re: horizontally polarised FM pirates

Post by Albert H » Wed Jun 08, 2022 1:35 am

Some stations back in the early 80s used slant polarisation to give signals receivable both by domestic horizontal aerials and vertical car (and portable) aerials. The most sophisticated of us used circular or sometimes "mixed" polarisation in an effort to get the best signal to the most receivers. Power outputs were frequently 10 - 40 Watts, with just a few stations achieving the magic "ton" (100 Watts).

The first higher powered stations were Thameside and Invicta - both at around 100 Watts - and it wasn't until the power FETs arrived at the end of the 80s that power levels increased much more.

Back in the 70s and 80s, the noise floor was much lower, and there were far fewer stations around, so you could achieve worthwhile coverage with just 10 to 15 Watts (a favourite device was the TP1028 which TRW rated at 10 Watts RF out, though by using a slightly higher supply voltage and critical tuning, you could get as much as 20 Watts out). Some fairly well-known stations seldom used much more than 40 or 50 Watts!

I built a huge number of rigs using a Mullard RF power module - the BGY33. This needed about 150mW in for around 20 Watts out. and was the PA stage I used for the first "frequency agile" PLL rigs that I built in the mid-80s. These rigs used an SP8629 prescaler (÷100) and a 4040, 4060 and 4046 CMOS ICs and a standard 4 MHz crystal for the reference, and could be diode-programmed for any frequency in Band II. The exciter I used an oscillator at ½f, followed by a buffer stage, a diode-based doubler, and a filter stage feeding into a pair of BSX20s delivering the 150 - 180 mW I needed.

The BGY33 was designed for battery use at (nominally) 12V, so I emptied several branches of Halfords of their (then) £8 car battery chargers. I removed the output leads (and used them later for high current DC supply wiring), fitted a heatsink to the back panel, spray-painted the bright red case to a dull matt black and assembled the rig inside the nice, vented metal box with a neon mains indicator, mains rocker switch, and even a chromed handle on top! I used the mains transformer that had powered the charger (it was capable of several Amps) and the ammeter was removed, and on the more expensive version I fitted an SWR meter and forward / reverse switch - the cheaper version just had the aperture covered by a piece of PCB material.
"Why is my rig humming?"
"Because it doesn't know the words!"
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sinus trouble
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Re: horizontally polarised FM pirates

Post by sinus trouble » Wed Jun 08, 2022 11:01 pm

Wow! The BGY33 brings back some memories! :)

I first saw them published in a Book i found at the local Library back in the early 90s

Even if my pocket money would barely cover it? Most electronic stores were reluctant to help sourcing one for me!

:(
I am as stupid as I look! :|

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Re: horizontally polarised FM pirates

Post by radium98 » Fri Jun 10, 2022 5:15 pm

there are also fake bgy33 or copies , that work on other band of fm , but om you will get only 7w , i still have a transmitter with a enuine PH bgy33c putting 22w

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yellowbeard
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Re: horizontally polarised FM pirates

Post by yellowbeard » Fri Jun 10, 2022 8:22 pm

These guys seem to have stock of new genuine items, but I'd phone them for confirmation:
https://www.donberg.ie/descript/b/bgy_33.htm
I got one from them waaay back in the day, it wasn't cheap then and it's still savage money today - they are a lovely yoke though. One of the Dutch shops was selling pulled BGY133's recently for €45 ish, but I can't find it any more so probably out of stock. Our Greek buddy Moutoulos has the swanky PCB's with the output filter:
https://www.moutoulos.com/eshop/rf-pcb/ ... d-20w.html
Here is the artwork if you want to build your own:
https://www.piratenpraten.nl/schemas/3- ... or%20133)/

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Re: horizontally polarised FM pirates

Post by Albert H » Sat Jun 11, 2022 1:14 am

Stone me!! €121.07 per piece! I used to buy them in trays of 40 for about £120! I still have two of them somewhere. They were very convenient for the RSL market.

We had a neat version with a 180mW exciter (using four transistors) and a 4059-based PLL with rotary BCD- coded switches to set frequency. The whole rig - including power supply was built into a 1U 19" rack box. It took balanced stereo audio in through a couple of XLR connectors, through a two-band limiter, through a stereo coder into the exciter, and later versions had an optional RDS encoder crammed in too. RF out was through an "N"-type connector, and mains in through the usual IEC connector. The power output level could be varied between 5 and 20 Watts, and there was VSWR protection built-in too. The front panel had a row of bi-colour and multi-colour LEDs to show condition - green LEDs showed power, RF out, locked on frequency, temperature OK, VSWR OK, and OK audio levels. Any amber or red LEDs showed that there was some kind of fault condition (or over-level audio) . There was also remote monitoring facilities.....

One of the first ones ended up in Belgrade in 1989, driving a big valved PA for "B92" - the station for the Yugoslavian revolution!
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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Re: horizontally polarised FM pirates

Post by sinus trouble » Mon Jun 13, 2022 12:03 am

Haha! Yes back then, The BGY33 was fascinating to me! :)

It would be great for nostalgic memories that was never achieved? However technology has moved on so much! The pursuit seems somewhat pointless!
I am as stupid as I look! :|

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Re: horizontally polarised FM pirates

Post by Persona Non Grata » Mon Jun 27, 2022 12:26 pm

jvok wrote: Tue Jun 07, 2022 8:32 pm Im more interested to know how they got the coverage they claimed on only 1 watt. A high site is great and all but still doesn't explain how they manage 50 miles coverage.
Maybe the listeners 50 miles away were using horizontally polarised multielement aerials as well ?

A lot of the multielement aerials on the market are only designed for horizontal polarisation even though most broadcasters these days use mixed or pure vertical polarisation. :?

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Re: horizontally polarised FM pirates

Post by 87to108 » Thu Jun 30, 2022 2:21 pm

Persona Non Grata wrote: Mon Jun 27, 2022 12:26 pm A lot of the multielement aerials on the market are only designed for horizontal polarisation even though most broadcasters these days use mixed or pure vertical polarisation. :?
That can be said about many TV aerials, such as this 'caravan/camper van' UHF aerial which is designed for Horizontal only:

https://maxview.co.uk/product/caravan-t ... w-omnimax/

It is for horizontal polarization, but as you probably know well, in the UK whilst the main TV sites are H, the relays are usually Vertical. Many coastal places (where caravanners may go on holidays) can have a poor (or no) signal from a main Freeview transmitter and may be served by Vertical polarized relays instead, yet this type of aerial will respond poorly to V polarization, and cannot be readjusted to V.

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Re: horizontally polarised FM pirates

Post by radionortheast » Fri Jul 15, 2022 9:08 am

I think this had to be more than 1w, more likely 25-40w, as everyone would have had specialized radios or no man made interference, it would more explain the fluke reception in Dublin, as I once had an RSL fade up from Reading. I would regularly get the ones from the wireless company, had to change the frequency of my transmitter, the one from the air show in lincolnshire would come up clearer on the hills, even thought I was miles away from it. 1w itself from a hill can travel far, I don’t think you’ll get much coverage, you would have to be on a hill right next to the place you wanted to cover, you’d get auttenuation everytime the signal passes throught buildings. If you were in a built up area say in town using 1w, you would at best only get a few 100 meters, even with the aerial on the roof the signal would be traveling throught buildings you would problalby get better signal outside of the town, I guess it would depend how big the town it is.
There was an RSL I used to pick up that was 1watt from 13kms away, the signal was alright 5kms away on a car radio don’t think you got much farer than that thought, unless it was your own transmission you problably wouldn’t bother with it.

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Re: horizontally polarised FM pirates

Post by Albert H » Sat Jul 16, 2022 3:54 am

Basic rule of VHF transmission:

Your signal ALWAYS goes to the horizon, no matter how much power you're using!

The carrier power will determine the signal to noise ratio. If the signal is noisy or distorted, people won't listen to it. More power means better noise quietening. Despite the signal actually getting there, if it's a weak signal, it won't be discernible when it gets to the horizon!

I used to run a little station in California, from a VERY high site. We used a directional transmit aerial (there wasn't much point in wasting signal towards a mostly empty desert!), and a small rig running between 40 and 50 Watts (according to how well the batteries were charged). We ran from "Leisure" batteries, recharged by solar panels and a little wind turbine. Over there, we seldom needed to take a charged battery up to the site, but at some times of year, it could be overcast, with little wind, so we always kept a couple of fully charged spares fairly close to the site.

It was linked from the city below on UHF (my usual TV Yagi to TV Yagi link setup), and we (mostly) ran live programmes. It broadcast each weekday evening and into the early hours, and all weekends. We had remote telemetry set up, so that we could remotely monitor the state of the batteries and the Charging and Discharging Currents and instantaneous battery voltage. The main output rig could be switched remotely over the link, so everything would be "dead" if one of us had to go up there to change the battery!

Despite the fairly low power, we covered a population of about 3 million (though we never really were able to measure our "reach"). We got lots of feedback from listeners, and interviewed lots of famous musicians (who all took our little station very seriously!).

Done right, with effective aerials and a good height advantage, even quite low power can achieve good coverage.
"Why is my rig humming?"
"Because it doesn't know the words!"
;)

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