Inside a Megawatt FM transmission tower and control room. - Page 1
Forum section: electronics / rf-microwave

author: BrianHG
author_rank: Super Contributor
timestamp: November 13, 2022, 11:01:00 pm
content: Inside a Megawatt FM transmission tower and control room.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: November 14, 2022, 11:05:02 am
content: Very interesting! only slightly annoyed that they misrepresent the power of the antenna by stating the EIRP instead of the actual power :p

author: coppercone2
author_rank: Super Contributor
timestamp: November 20, 2022, 12:06:04 am
content: love the extra room cooling fan. 1% cooling trimare those heavy airline sections brazed together or just bolted? It looks like steam style construction. If I did not know what that was, I would have thought the transmitter room is some kind of industrial steam dryer. It looks like its almost entirely bolted together.I wonder what the longest piece of non joined pipe is in that network. Do they have some long feeders or is there some kind of maximum section length? I don't think I noticed any really long uninterrupted runs.

author: TheMG
author_rank: Frequent Contributor
timestamp: November 20, 2022, 02:26:33 am
content: They are just bolted together. No brazing.It's meant to be easily serviceable if you need to rearrange things, or replace a damaged section.

author: coppercone2
author_rank: Super Contributor
timestamp: November 20, 2022, 02:28:25 am
content: I think I saw another transmitter that had much longer tubes and like brazed elbows, this one seems like a 12-15 foot maximum section? But its also a higher power level, that one had like 3 inch tubing max

author: radiolistener
author_rank: Super Contributor
timestamp: November 20, 2022, 02:47:10 am
content: 500 kW short wave transmitter with reconfigurable phased arrayI think it's ERP (Effective Radiated Power) is incredible, probably something like 10-100 MW...

author: BrianHG
author_rank: Super Contributor
timestamp: November 20, 2022, 03:51:45 am
content: That's massive for a small 2 person family to operate from basically home.I wonder how many are actually listening to their content on the other side of the world. You would need some good reflection characteristics in the atmosphere.When they focus their antenna, I wonder if they are cooking any life along that beam...

author: radiolistener
author_rank: Super Contributor
timestamp: November 24, 2022, 05:54:32 pm
content: Yesterday we have blackout in my city, and I listened radio. I tuned 9330 kHz and found WBCQ AM station with a pretty good quality.The transmitter is located 7060 km away from me, on another side of Earth and I can listen it with pretty good quality on internal ferrite antenna

author: BrianHG
author_rank: Super Contributor
timestamp: December 10, 2022, 06:09:04 am
content: Part 2, ERP explained...

author: BrianHG
author_rank: Super Contributor
timestamp: December 10, 2022, 06:10:43 am
content: Quote from: radiolistener on November 24, 2022, 05:54:32 pmWow....

author: janoc
author_rank: Super Contributor
timestamp: December 10, 2022, 11:35:12 am
content: Quote from: BrianHG on December 10, 2022, 06:10:43 amThe wonders of shortwave radio. The only way we had to communicate in real time around the world before satellite and internet (not counting wired telegraph - that wasn't quite real time).Whenever I turned on my scanner or SDR, I could also hear regularly hear Radio Beijing, lots of Arabic & Persian speaking stations, broadcasts in Spanish from South America, US stations ... All that on a small wire antenna in a flat in France/Germany.And it will only get better as we are getting out of the solar cycle minimum and the ionosphere gets more active, opening even the higher bands. I remember during the last solar maximum in the 90s I had a CB (28 MHz or so) - and during the day I had CB FM stations from South America booming out of the speaker due to the sporadic E propagation. Local contact were often impossible due to that interference. And that's CB - imagine when you are blasting out hundreds of KW of power into a huge antenna and also at a lower frequency (thus tends to propagate better/farther even in the absence of Es prop).

author: DavidAlfa
author_rank: Super Contributor
timestamp: December 10, 2022, 01:03:26 pm
content: Saw the video a while ago, seeing those right-angled transmision lines everywhere was strange.

author: radiolistener
author_rank: Super Contributor
timestamp: December 10, 2022, 01:26:37 pm
content: Quote from: janoc on December 10, 2022, 11:35:12 amSometimes, in the deep night, I receive signals from a low power stations in digi mode (FT8), about 5-100 W at 7 or 14 MHz which are located more than 12000 km away from me. But it needs to catch best time for signal propagation in order to receive it. Unfortunately time window for such reception is too short, about one hour or even smaller.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 10, 2022, 02:57:53 pm
content: Quote from: janoc on December 10, 2022, 11:35:12 amUndersea cables were around a little longer than shortwave radio, & pretty much paralleled it in development.Initially using telegraphy, then single channel speech, then AM multichannel, followed by DSB suppressed carrier, then SSB/ISB. These were upconverted to higher frequency carriers, which enabled many more channels.Similar systems were used on land based cable systems.In the early/mid 1960s, the ABC in Australia, & the BBC in the UK had regular programmes for "family get-togethers" over the Seacom & Compac cables.Apart from that, a lot of other material was regularly transferred across those, & other cables.

author: Red Squirrel
author_rank: Super Contributor
timestamp: December 11, 2022, 03:45:14 am
content: Really impressive stuff. As someone that works in telecom it's cool to see a more RF oriented side of things. Really interesting gear, and all the rigid coax etc is pretty neat.

author: janoc
author_rank: Super Contributor
timestamp: December 11, 2022, 08:35:56 pm
content: Quote from: vk6zgo on December 10, 2022, 02:57:53 pmSure - but the cables were at the time used for telegraphy only - and that wasn't quite real time communication. You had to prepare your message, go to the nearest telegraph office, get it sent to wherever the nearest telegraph station to the recipient of the message was and then a postman (usually) had to deliver it. In some cases it could take days or even weeks if it was to some remote area. That's why I have explicitly omitted it from such comparison.Radio allowed point to point communication, all over the world - and even for "mere mortals", without having to rely on telcos and telephone/telegraph service which was not everywhere. Radio amateurs tinkering with radios have been around pretty much from the time of Marconi - and many played key roles in many well known events. E.g. in 1928 the Italia airship crashed on its way from the North pole and their shortwave distress calls were picked up by their support ship only thanks to a Russian amateur who has heard them & relayed them to the authorities. Same thing happened during the Heyerdahl's Kon-Tiki expedition in 1947 - HAMs on HF were the main way of communication for this crazy expedition in the Pacific. WWII has seen many HAMs play important role in the resistance, despite owning a radio station being punished by death/concentration camp.These days satellite coms have pretty much eliminated most of such uses - yet both ships and planes still carry (and use!) HF radios when sailing/flying over the oceans.I think you know all this, given that you are also a HAM but I am putting it here for the sake of others who may not be aware.

author: eti
author_rank: Super Contributor
timestamp: December 12, 2022, 01:02:49 am
content: It SCREAMED to me"Dad is a hardware person, I am a software person, I am a bit out of my depth and this is not my realm"when he called cables"wires".It was a very interesting tour, thank you for sharing this.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 12, 2022, 05:23:58 am
content: Quote from: janoc on December 11, 2022, 08:35:56 pmCommercially, radio was initially all radiotelegraph, so the average person would have done exactly as you recounted above.The public Telegram system was pretty much "agnostic" as to whether the message was delivered by radio, landline, or undersea cable.The development of Radiotelephony was pretty much in "lockstep" with that of long distance Line telephony over the early development of both.Plain old telephones were already around prior to Marconi's first successes.QuoteAll of the above is correct, but doesn't back up your original statement :-"The wonders of shortwave radio. Theonlyway we had to communicate in real time around the world before satellite and internet (not counting wired telegraph - that wasn't quite real time)."