I am carrying out my pre-planning for the completion of my CW MG, but Covid constraints are a major obstacle to gaining the remaining 28 points. This work took me to planning my first activation of the well named Black Hill G/SP-002. I have walked over this hill several times, once on a “Pennine way” walk in the 1970’s. As I pondered which access route to use, I noted the Holme Moss BBC transmitter site which I vaguely remembered visiting with my father in the early 1960’s.
A look on the web and I found a bit of fuzzy video on Youtube showing the open day in 1961.
Suddenly memories of the open day came flooding back. The 800ft mast, the man climbing the mast, the control room and the BBC engineers dressed in grey flannels and sports coats with leather patches on the elbows and smoking pipes. It is quite amazing to see members of the public crowding round the transmitter panels, with children only inches from the controls. The video is very much “of its time”, with a brass band accompaniment, but I was there on that day!
At 250kW, my first transmitter. Perhaps that is why I am not a QRP man?
It was only about 115kW ERP per channel when you were a youngster. 2x 10kW transmitters per channel into 8 tiers of 4 slots per tier. Now it’s 250kW ERP on 4 BBC channels and Classic FM. I think a lot of the gain increase came when they replaced the horizonal slot antennas with mixed polarisation on the new mast in the mid-80s
Over 8000 visitors drive to see a TV transmitter in the middle of nowhere!
People wouldn’t bother today. It shows there was nowt else to do for entertainment in them days.
When the first section of the M6 motorway [Preston bypass] was opened in 1958, there were bus tours along it cos folk wanted to see it or they drove their 1950s cars flat out on it [no Motorway speed limits then], many of them breaking down [the cars that is].
But it was real Dan Dare stuff back then. We’re around the same age and have seen huge but essentially incremental changes to technology over our lifetimes. At Holme Moss in 1951, they went from no VHF radio and no VHF TV to it being an obsolete TV transmitter in 18 years as UHF colour TV came about. Such a chance to see technology was bound to be popular.
Nowadays technology is ubiquitous. I have a surplus Android phone that has more computing power than the whole of our Alma Mater had when we were students there and it sits in the kitchen just as a Spotify access device so I can listen to music in the kitchen whilst working from home.
I wonder how many of those cars were close to boiling over by the time they climbed up to the summit?
David @G0EVV, here’s more men with pipes, a BBC “How we built Holme Moss” from 1951
I just love seeing all the workmen with no hard hats, no hi-viz jackets, no gloves. There’s a guy using a pneumatic drill into stone and a bloke with his face less than 2 feet from the drill with no safety glasses. We can joke about Health&Safety gone mad now but how did anyone live long enough to get to retirement back then?
Many didn’t, that’s why the regulations appeared! The old attitude was that if somebody died, why worry, there’s a replacement waiting for a job outside the gate! The growth of unions and the post-war Labour governments put a stop to that attitude.
Pipes were cool after the war. In my youth I knew many old aircrew (they weren’t so old then!) who all told the same story, they took up smoking a pipe because it involved work (rolling the tobacco, filling and tamping the pipe, lighting it and keeping it going, then knocking out the “dottle” and cleaning the pipe) and this work distracted them in the tension filled hours before going “on ops”, that so many never came back from!
I read that the Apollo 11 [16-bit?] guidance computer had a 4kB RAM and 72kB [non-reprogrammable] ROM – with the processor probably made from Mil-spec TTL logic. I bet they had a team of engineers who programmed it in assembler language and machine code to squeeze functionality into every last byte of memory - cos that’s what I was doing in 1977 on my first professional embedded microprocessor design [using the Motorola 8-bit 6800].
Contrast that with my last embedded systems project before I retired from electronics [2008] - we used C++ running on a commercial operating system and weren’t too bothered about program size or performance due to the amazing advances in silicon technology in the three decades since I started work.
Many of the programmers on Apollo were women. Few got the recognition they deserved at the time and most are still unknown. The Apollo software is available on line so you can see how to write memory constrained, CPU constrained software to handle a series of tasks. It did a rigorously defined set of jobs and did them well with no “input from marketing”
The Apollo software was a classic co-op multitasker OS, all the individual processes were designed to run for some number of cycles then yield back to OS. If anything over-ran (because it had crashed etc.) the system did a soft-restart. It was good enough to put 12 men on the moon and bring them back so I used the same idea for the software running an in-vitro histological tissue processor. I had a hardware watchdog with an interrupt half-kicking the watchdog and the exec completing the kick. If either the interrupts died or a single control task failed to yield in time then you got a watchdog kick and the system went into a failsafe mode. As soon as the toggling stopped then another hardware watchdog dumped the power to the heaters. This was the best way to stop boiling many tens of patients cancer biopsies. It left the machine in a mess when the staff came in the next day but the biopsies were recoverable and the processing could be continued. That way the doctors didn’t have to say to the patients “we don’t know if your lump is malignant because the machine ate your biopsy. Come back in a few weeks when your lump has regrown big enough and we’ll have another go. It would help us if you don’t die before then.”
The top shows 2 tiers of 4 vertical dipoles give a vertical polarised signal. They were all fed in phase to get an omnidirectional pattern on Band 1. Beneath them are the Band II FM antennas. Here there are 8 tiers of 4 vertical slots giving horizontal polarised signal. Again all fed in phase to get an omnidirectional signal. Observant readers will notice there are 2 tiers of panels at the top with no slots. These are possible mounting places for the vertical dipoles at the top. Future expansion could well have been another BBC TV channel on Band III in which case the dipoles would be relocated on the blank panels and a Band III antenna placed at the top. With Band III being around 200MHz the maximum height would be needed to get the coverage needed. In those days the BBC had their own masts and when commercial TV started the ITV companies built their own masts for Band III. Colour TV on Band IV/V (470-890MHz) would need so many transmitters to approach the coverage of Band I/III that the BBC and ITV decided to share sites.
This is the classic BBC design of the time. The slot antenna is made from 4 aluminium panels to form a tube about 2m in diameter. All the panels bolt to each other side to side and top to bottom. The 10 tiers form a fundamental part of the mast structure… there is no lattice mast inside the panels so they support themselves and the top structure and antenna. This was a clever idea at the time. But as FM radio take up grew massively, the in-car signal suffered from the polarisation loss between a vertical antenna on the car and the fact all BBC transmitters were horizontally polarised. The BBC had to replace all the masts of this design with new bigger lattice masts to support the weight and an extra number of mixed polarisation antennas that were needed. Most masts were replaced in the early 80s as Radio 1 got an FM frequency.
One of the few masts of this period still standing is the original BBC Kirk O’Shotts mast. This was the first TV transmitter site in Scotland in 1952 and was almost identical to Holme Moss. When Band I TV was closed down in 1984, the FM antennas were added to the Black Hill mast (the commercial mast) a few miles away. The Band I and Band II structural slots were removed lowering the mast by about 150ft. A small stub mast and 8 tiers of 4 vertical dipoles for Band III DAB was added later.
They must have made it from proper steel (no Middle Kingdom rubbishy monkey-metal) and done proper maintenance because the original Kirk O’Shotts mast is still standing and used 68 years later.
Wow David that brought back some memories Thanks ! My dad and I were there also on that day I saw my dad in the film but not me…maybe I was getting sweets or something. Anyways thanks for putting it on.
Pleased to help, just shows what is out there, captured on the wobbly web. I noted a Ford Popular car (the pop) on the film, just like the one my dad had, no way to say it is the same one though.
I hope to do the deed of activating Black Hill on 23/24 December, “all things being equal”.
Thanks to all for their contributions.
Mike, G3YPE,
The band 1 dipoles at the top of the structure housed 100kw of heating to help de-ice the antenna. It was only switched on after load shedding the band 2 transmitters on to the standby diesel generators. This was to prevent us exceeding our allocated maximum demand from the electricity supplier and the high penalty costs.
The weather had the final say in 1984 during the dismantling of this mast, we had severe icing of the structure due to freezing fog. The new mast was in position and in use. The stays from the old mast were interleaved with those on the new mast. The ice built up to about 2 feet in diameter on the stays which would not have been a problem, but the stays to the 600 foot level were temporary for the dismantling and were much smaller diameter, plus the shackles in the stays were not rated for this greatly increase load. The site was abandoned. The stays held but ice build up on the slot antenna cylinder approx 100 feet long and 3 feet thick posed a threat. Rain spread in from the southwest and the temperature rose quickly. That piece of ice slid off intact, crashing through the reinforced building flat roof damaging and flooding the high voltage switch room. The new mast was undamaged but some 1/4 inch steel plate protecting the feeder run was bent downwards onto one of the 6 1/8 inch feeders feeding power to half of the new vhf array. It was difficult to know how far the outer of the feeder had collapsed. We used a high voltage test set to determine the flash over voltage of the feeder, which we found to be severely reduced. We had the feeder x-rayed using a gamma source which confirmed the feeder had been crushed to about 50% of it’s normal inner to outer spacing. The length of feeder from the mast base was cut out and a new length installed. The damaged section was cut out from the removed section and mounted on a piece of wood that resided in my office as a display piece. I assume that it is still there.
