One of the things about being a radio communications engineer is that I look at antennas (aerials) in the same way that birdwatchers look at birds: noticing the everyday but also recognising the unusual. So, a spotters’ guide to some unusual antennas on this house in Cambridge:

Let’s start with the run of the mill: the blackbirds of the antenna world. Two Sky mini dishes. Useful fact: all Sky dishes point roughly south-east (as that’s where the satellite is), so you can use them to get your bearings if you need to.

Equally mundane, up here on the chimney pot, is an ordinary TV aerial. In Cambridge these point towards Madingley (NW of the city) because that’s where there’s a convenient small hill with the transmitter on it.

Now things get more interesting. The bottom one is just a TV aerial that’s been dislodged by a storm and now hangs at the wrong angle. But above it we have a pair of antennas that probably were last used in the early 1980s. They would have received black-and-white 405-line TV.

405-line was broadcast at a lower frequency than modern TV. In fact, two different sets of frequencies (“bands”) were used. The original BBC stations were in “Band 1” at around 50-60MHz, and later stations (including all of the ITV ones) were in “Band 3” at around 200MHz.

Hence we see two antennas: the lower one is for Band 3 (most likely for watching ITV) and then above it, the single long bar is what’s left of the Band 1 antenna for watching the BBC. A lower frequency needs a physically larger antenna, and the big Band 1 ones often fell apart.

So now we come to the rarest spot: this octagonal grey thing. This is the remnant of an early attempt to provide broadband in Cambridge. A company called Ionica launched this service back in 1995, but went bust in 1998. Their antennas are still around more than 20 years later.

Ionica’s technology didn’t work that well, it seems. https://en.m.wikipedia.org/wiki/Ionica_(company).
The service came from access points around the city. Let’s have a guess. It seems that this antenna is looking at the top of the tower of the Carter bridge. I think the grey lump on the right is it.

So: one terraced house, two bits of obsolete radio history!

CORRECTION: the main TV transmitter for Cambridge is Sandy Heath (near Sandy in Bedfordshire). There is a transmitter at Madingley, which in days of yore used to put out Channel 5 on analogue. Now it puts out the local "That's TV" service. Thanks Kev: https://twitter.com/Boredstoopid/status/1298157091560071168?s=20

CORRECTION: Ionica's business model was actually cheaper phone lines and not internet access - their archived website makes for hilarious reading with hindsight. https://web.archive.org/web/19980117225448/http://www.ionica.co.uk/ - thanks Martin: https://twitter.com/bigcheeseradio/status/1298156681839353861?s=20

Turns out my ex-colleague Jamie (he's a mechanical engineer) designed the mounts for the Ionica antennas. Amazing! https://twitter.com/jimjam1971/status/1298171569865469957?s=20