S J Birkill's experimental satellite receiving station, Sheffield 1981-82 -- broadcast TV coverage

Satellite TV pioneer S J Birkill contributed to a number of TV news programmes around the time the UK announced plans for a future DBS service. Nationwide, Newsnight, News at Ten, Look North, Blue Peter and Tomorrow's World all covered his experimental work at the Grenoside, Sheffield location between 1975 and 1982. Here is a selection of clips.

[@protvua]

I was born in 1981. That guy received sovetic tv from satellite. Great

[@protvua]

@Коала ТелеБачення where?

[@videosuperhighway7655]

Dude was a genius, building his own Microwave reception equipment, ie LNA, downconverters etc, in his home thats just crazy.

[@jamiemason9548]

Hi my father worked on this in the 1969 to 1989 worked with progress

[@myshadowisblack]

Steve was a real genius. Great guy.

[@weakbit633]

If we compare the first steps in satellite receiving from Mr. Steve Birkill at this time he received 4channels (different Color Systems I think SECAM or PAL[what was the Russia system?] and different Audio I.F. 6.6MHz) from one satellite position - to the to days Astra Group 19.2°East with over 1400 channels in digital quality so we see the +40years long development from the Television signals and systems that is transmit out over this microwave frequencies. Astonishing

[@volkerking5932]

How he can measure in this high frequency? He build his own LNC (Low Noise Converter) with a HEMT (High Electron Mobility Transistor) as a Amplifier and a Mixing 1st. Stage Converter to a lower frequency 1st IF. ~750MHz - 1700MHz. Interest the first 2,5cm (12GHz) wave where circular polarized and not linear then the today's satellite. Also he build a wideband amplifier too. (unbelievable) Today are also circular polarisation on the air. But I'm wondering that he can measure something in this high frequency? I'm wondering but it is possible to that at home! Super cool I like that very much!!! I would like to build also my own LNC but 40 years later how I can do this?

[@midvodian]

Hi Volker -- Measurement was pretty well impossible for the impoverished amateur experimenter back then. The circular depolarizer for instance was built from theory: for Ku-Band (11-12 GHz) I used diametrically opposed rows of set-screws set in the walls of the circular waveguide feed, spacings and tapered lengths to provide the differential phase-shift over the known bandwidth according to guide wavelength, but then the 'trick' was to spend time adjusting it empirically: rather than peak the wanted signal, I would first acquire the satellite in linear (plane-polarized) mode (3dB loss), then tweak to minimise, to null out the desired RHCP signal (i.e. set it for LHCP), then rotate the feed section 90 degrees to maximize RHCP. For C-Band (4GHz) my first feed worked the same way, though later I used a PTFE ('Teflon') slab set at 45 degrees to the feed element to provide the depolraization. The 10GHz local oscillator used a packaged tunable Gunn-effect device obtained on the surplus market (doppler radar components), with IF (referenced to UHF TV channels) to set the exact frequency within a channel or so, say +/- 8 MHz. The LNA was designed from theory (device S-Parameters, Smith Chart, microstrip substrate specs) then optimized by hand for best signal (as the hams used to say 'tune for maximum smoke!) . Things are a little easier today with availability of free CAD tools and an abundance of microwave semiconductors. Cheers -- Steve.

[@volkerking5932]

@@midvodian Hi Steve - well i see - to the Circular wave guides i used plexiglas for the Rotation of the wave inside the waveguide from a 4GHz LNC. But my Chinese 17Kelvin LNC that i bought in Ali for arround USD20,- was a 2 Antenna Vertical and Horizontal LNC. What i see on your Waveguide was the 1/4 wave Lambda distanced Allining skrews for made the circular wave to receive (this skrews are ina even in row [straigth]). I would like to build one LNC Holder for allining the exact position for the LNC on the Dish itself. My idea of the functions are changing the LNC Typ (Ku, C-Band linear, C-Band circular) also Focus and skew all mechanical. Thank you and Best Regards Volker

[@midvodian]

@@volkerking5932 Well, I haven't been involved with the satellite business for some years now, but what I would have given for a 17K LNC -- for any band -- back in 1980! Just one thought: Plexiglass (Perspex, acrylic sheet) might not be your best choice for a depolariser: I believe its loss tangent is several times that of Teflon (PTFE) at microwave frequencies -- you don't want to increase that spectacularly low noise temperature! Kind regards and best of luck with your satellite project -- Steve.

[@volkerking5932]

@@midvodian I know well that a peace of Plexiglass (Perspex, acrylic sheet) are more loose then a Teflon (PTFE) for depolarisation but at this time I have no other possible ways to do the depolarisation - that was the reason, it was weekend and here is no shop in Vienna (Austria) to buy a peace of Teflon. What I do to test materials like this, I put it in the microwave oven and feel if it warm up that is a lot of loose the Signal. I think the absorption in a material is the higher EpsilonR - everything absorb in thermal power and end in the death (thermal death I think it came from Kelvin). What do you think on a mechanical Movement for the LNC? Is it a good idea to align the Focus on the LNC and or the skew rotation for a better signal? I build in 1990 a Satellite Decoder for resynch the PAL Signal that are transmitted without a correct Horizontal-Sync (the Sync was bigger then the Video signal in each Line) and without the Vertical-Synch. With a small µController (8031, Latch 74hc573, Eprom 27c64 & a EPLD intel i5c060) I re synced the wrong Signal. Also the Video polarity was changed in every line and switched from frame to frame with different polarity as start. Later in the Y2K i repeat the building with a FPGA and the cable network used it here in Vienna. During you received the very weak Signal from the Arabic Satellite program it is very useful to re sync the weak video signal and for sure I used the same Video re synch electronic on my dish (1,40m bigger was not possible to install) in 1990 for weak signals (IRIB3 I think it was on an very east satellite) to re synching weak Signals. The Video appear in a Colour full stable picture frame on screen. Well the video signal was blur and washed out (there was no drop-out compensation like in a Beta or VHS Recorder where is inserted in to the Video information for the time of the drop-out from the previews line) but the brain will reorganize the little wrong parts and you think you see a good picture in sum. Please can you tell me where are the white/black horizontal flash spots (dorp-out) are came from? I heard about the FM demodulation and this is over the bandwidth out so if you limit/reduce the bandwidth. I've a old HP141T with a plugin 8555 (till 22GHz so god will) measure equipment and I will make a self build LNC for a Kit to build. What do you think about this (because this is total crazy then a LNC cost like notthing but for education I think it will be OK). Should we build a 21GHz LNC? I know this is much more complicated or 4GHz this is I think for sure complicate enough. Thank you and Best Regards Volker

[@midvodian]

​@@volkerking5932 www.ebay.de/itm/Teflon-sheet-10mm-thick-12-x-8-75/202651068605