FM DXing in the UK During the 1970s

Guy Stanbury



INTRODUCTION

My interest in 87-108 MHz VHF-FM broadcast reception was originally sparked off when I met a gentleman by the name of Robert Dewick of Bradwell-on-Sea, Essex (his eldest son Richard was in the year above me at school - we were good friends back then and still keep in touch).

Bob’s home was on the Essex marshes and when I visited at Richard’s invitation, I was fascinated by the multitude of broadcast FM stations he could hear, initially on a valved ‘Hacker’ VHF radio and a solid-state Trio tuner amplifier. Bob was of an age that meant he was among the first people in the UK to hear Captain Armstrong’s FM experiments during the mid-1930’s. Indeed, I still have the 1935 edition of ‘Wireless World’ that Bob gave me, which he’d used when building his shortwave receiver.

Bob introduced me to the Fuba UKA 8 antenna (rope and pulley rotated!) and upon his recommendation, I became an avid reader of Austin Uden’s ‘FM Diary’ that was carried by the UK Wireless World magazine for many years.

My Essex home DX monitoring room photo reproduced above was taken in 1977, and includes Stolle 2010 rotator control box, masthead preamplifier gain and tuning control box, reel-to-reel tape deck, PW Sandown FM tuner, Ambit Mark III tuner module prototype (on evaluation), RCS401 frequency counter, Gould Advance OS250B oscilloscope, and Gould Advance RF signal generator.

When I left college in 1978, I applied to the BBC for work. Helped and encouraged by my careers master, and having impressed the recruitment team with my enthusiasm for and knowledge of long-distance VHF-FM reception, I was offered a post by the BBC’s Monitoring Service at Caversham Park near Reading, Berkshire. I started in April 1979 and was promptly shipped off to undertake shift-keeping duties at the Monitoring Service’s Engineering Reception Station. This was located in an electrically quiet location about six miles away at Crowsley Park, near Henley-on-Thames, Oxfordshire. I recall a technition by the name of Dave Kenny who was based at Caversham, and he was also a bit of a FM-DX buff – we kept in touch and would ring up one another whenever high pressure was becoming settled over the UK / near Continent. My involvement meant that I was well-placed to keep tabs on matters VHF (and up). I well remember some spectacular Sporadic E openings; on one occasion I counted (and frequency-measured for the operational log) over 150 Italian broadcast stations in one hour. No RDS either, so identifying them was a real challenge … get to 108.0 MHz, go back down to 87.5 MHz, do a re-calibration of the panoramic display, set up the zero-beat signal generator to check carrier frequencies and start again … (those that were legit. e.g. RAI were easy, but there were also myriads of pirate signals). Band II’s exploded! - call the shift supervisor over – “Geoff? Band II SpE path’s opening up to Yugoslavia, now … can you get on the phone to BBC Engineering Information Department and give them the good news so they can fend off the phone calls from hundreds of irate listeners?”

In the mid to late 1970s I contributed broadcast FM DX reports to Ron Ham's 'VHF column' as included in 'Practical Wireless' magazine. Other contributors to Ron's column included Ian Rennison (Horsham, Sussex). At the time I was also planning on extending my monitoring activities to UHF TV DX.

In 1981, I moved across to BBC Transmission, working in Transmitter Operations (nominally based at Home Moss, West Yorkshire) until 1988, when I transferred to Transmitter Capital Projects Department (or TCPD – otherwise known as “Two Cock-ups Per Day” by the Ops boys). I started in the Broadcast Communications Section on BBC Local Radio studios throughout the UK, installing and commissioning broadcast TV and radio receiving antenna systems, radio car VHF/UHF link base station systems, selective calling and so on. In 1992 I moved into the area that dealt with transmitter monitoring and control systems (telemetry/fault reporting etc.) and became involved in a two-year project that saw the complete re-engineering of fault reporting systems on some 380 BBC UK domestic broadcast transmitter sites. After that project finished, I was seconded to and spent three months in Antenna Department working on low-power FM relays before moving into Site Sharing Section in 1994. I stayed there during (and for eighteen months after) the sell-off of the BBC’s transmission services and assets in the mid-90’s. After a short spell with Merlin Communications working on satellite earth station monitoring and control systems, I joined NTL (old Independent Broadcasting Authority) and worked on broadcast radio system projects, including analogue AM/FM, Digital Audio Broadcast radio regional/local expansion and core IP infrastructure upgrades. Unfortunately, NTL’s share price went into free-fall during the summer of 2001; events of 9/11 didn’t help and having been offered a silver-plated parachute I was made redundant in 2002, along with some 300 hundred other engineering specialists (NTL is now Arqiva, having been acquired in 2004 by a consortium led by Macquarie Communications). These days I’m part-retired, part self-employed and operate my own small company delivering rural broadband solutions by satellite.

DX EQUIPMENT



PW Sandown FM tuner-cabinet front: this was my version of the 1974 design by Messrs. Ames/Carey, modified/upgraded as follows:

(1) 10-turn wirewound potentiometer / Beckman Instruments ‘Duo-Dial’ turns-counter for referencing broadcast station frequencies against a graph-paper scale. I remember having many problems with temperature-related drift of the varicap tuning voltage supply - subsequently, I built a frequency counter using the ‘General Instruments’ Application Note for their AY-5-8100 chip plus Futaba 5-LT-03 fluorescent display. Although it worked well, screening out the RF hash from the FM front-end was a nightmare! In the end, the counter had to go into a physically separate box, with the main board itself inside a die-cast box such that every connection routed via feed-through capacitors and heavily-screened cables. See http://www.radiomuseum.org/tubes/tube_ay-5-8100.html.

(2) RCA CA3052 audio preamplifier (see attached) plus 2 x TBA810 configured as a stereo audio preamp / low-power driver amp for headphones. This was the most successful audio project I have ever built and supported RIAA-equalised phono inputs, reel-to-reel/cassette deck line inputs/outputs as well as the tuner line-level input. I still have some of the FM-DX tapes I made – French/Dutch/Belgian/West German broadcast stations, also a very good recording of a multi-tone pager system (believed to have been called “SEMAFOON”) which operated from stations in the Netherlands and Belgium. The paging center was located in The Hague. It used four closely spaced frequencies just below the broadcast band (87.15, 87.2, 87.25, 87.30 MHz) each site activating in turn to radiate a pattern of tones. It was a great indicator of enhanced tropospheric propagation i.e. if I could hear the ‘tweedlie-deedlies’ I knew the band would be active and that it was worth ‘having a trawl’. The tuning meter would twitch quite spectacularly when this came in because I’d calibrated the CA3089E’s tuning output to be as close a match to the 100-0-100 µA meter scale i.e. +100kHz .

(3) A later modification was the ability to superimpose a ramped DC voltage to the tuner’s varicap line and take a sniff of the CA3089E signal strength meter output to an oscilloscope – a sort of home-brewed ‘panoramic adaptor’ if you like. I used the ICL8038CC function generator chip which produced sine, triangle and square-wave outputs whose frequency and duty-cycle could be adjusted. I tweaked it so that the triangle became a sawtooth and the square wave became the ‘scope timebase trigger pulse. I soon discovered that my Local Oscillator was also being ramped at frequencies 10.7MHz away and thus wreaking havoc with neighbouring receivers … so I had to use it with discretion! Incidentally, the original ‘scope I used for this purpose was an old Cossor 1049 Mk IV – I picked up three from the local techno-scrap dealer, along with a ‘Record Instruments’ 1-hour / 24-hour gearing chart recorder, the latter still in its original packing. “R.I.” were still around (Altrincham) and very kindly sent me some brand new rolls and ink capsules for it - so I built a fixed-frequency FM receiver (based on the Larsholt 7252 tunerset via Ambit again), tuned this to a low-power Belgian RTBF outlet (Froidmont: 103.7MHz) and connected its signal strength meter output to the pen recorder. This gave an excellent indication of Band II activity and hence a good visual warning of any development of Continental tropo.

Antiference 6 element FM Yagi.

This was my original FM-DX Yagi antenna and started life as a four-element to which I added two extra directors. If you look carefully, you’ll quickly see that the spacing of the two forward directors relative to the others doesn’t ‘look right’ and indeed, it was the lacklustre performance of this antenna that prompted me to go for the Fuba UKA 8-over-8 option.

I’d acquired a copy of Henry Jasik’s ‘Antenna Engineering Handbook’ (which I still have) and soon realised that using two commercial multi-element antennas (each with a twin reflector arrangement) in a stacked array was more likely to yield a worthwhile improvement in F/B ration and gain, as compared to just adding directors where phasing/spacing was very much a hit and miss approach.

The rotator was a Stolle type 2010 ; initially, I used only one support bearing with the drive mounted at the top of the pole.

Early experiments in building a home-brew rotator included a seriously cannibalised/modified motor assembly from an old Collaro record turntable; this operated a cord and pulley arrangement which I’d knocked up in the metalwork workshop at school; the cord was 150lb test fishing line and as you’ll no doubt realise, not only was accuracy non-existent, mechanical backlash was a real problem. Going one way was easy enough, but since the Collaro motor was a shaded-pole uni-directional device, in order to reverse the antenna rotation, one had to manually disengage the drive (by means of a gear-lever!), grasp hold of the final drive pulley and yank the system back again. Very crude, but reasonably effective (and great fun to build).

VHF-FM DX Fuba UKA 8-over-8 rotatable stacked array.

This design incorporated a masthead preamplifier (located in the grey box mounted between each antenna). I’d experimented with 2x2N3819 FETs in cascode as a manually tuned signal preamplifier at the back of the set and quickly appreciated that the best place for amplifying a signal is right by the antenna. The one in the photo used the first stage of an Ambit EF5800-series front-end module. As a varicap-tuned, dual-gate MOSFET circuit, the design lent itself well to remotely optimising tuning and gain. It was also spectacularly easy to build as obtaining the first-stage of the circuit could be easily achieved by means of a well-placed hacksaw cut across the width of the PCB J I also took the opportunity to re-engineer the Stolle rotator system such that the rotator was fitted between two of the standard Stolle support bearings; this ensured the drive’s thin shell bearings were only called upon to handle torque-related loads rather than supporting the weight of the entire array as well. I recall having to get courageous and hacksaw off the small bit of casting that was originally intended to act as a vertical ‘stop’ when using the rotator drive in its conventional position.

Fuba UKA 8-over-8 rotatable stacked array and mast wall mounting bracket.

I’d already decided to engineer the facility for relatively easy maintenance and hence the mast design incorporated a hinged section near ground-level. With care (and in calm-weather conditions only), the entire array could be lowered using a double pulley system. However, it still needed “Armstrong technology” to get it back up again (and almost always a second person as ‘banksman’ while U-bolts were worked on).

The UKA 8 I’m working on at the moment is connected to a Sony tuner-amplifier of similar vintage – see attached photo of STR6046 – it works a treat and we have a broadcast station called Smooth Radio here on 105.7 MHz which specilaises in 1970s classic rock and pop. The causality (synchronicity?) of all this connecting together right now is really rather heart-warming.

I'm currently refurbishing a VHF Band II antenna that I'd kept from my previous FM-DX activities having moved away from Essex in 1982. It's the Fuba "UKA Stereo 8", originally made by Hans Kolbe of (then West) Germany to a specification that I believe may have dated from around 1964. In parallel with refurbishing the original, I'm building a copy from stock alloy/stainless steel. The dipole junction box uses a standard domestic weatherproof box with plenty of space inside; I feel a tuneable pre-amp would be a useful option.

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