Radio communications OT.

[JRouche]

Although at least some people knew about 'short waves' in 1923 Britain and no doubt other countries were still building huge longwave stations years after then.

Right? The long wave communication didnt need to be there until Submarine stuff. Its a thing,

So we built a few long wave antenna out here on the west coast. There are some on the east and other counties.

I would suspect they are still using these installations. I went to in San Diego was as large as any cattle fence. Yeah, this ant. was massive. Low freq, large ant. High freq, tiny ant.

Thats the Lenzs Law? Hahaaa JR

[The Artful Bodger]

Right? The long wave communication didnt need to be there until Submarine stuff.

Long wave communications was 'the thing' before WWI...

Louisbourg, Nova Scotia


As the original, powerful spark gap transmitters would create large quantities of electrical interference, stations could not transmit and receive at the same time - even if different wavelengths were used. By 1913, the increasing amount of transatlantic radio telegraph traffic required that existing half-duplex operation be upgraded to a link which could carry messages in both directions at the same time. This was done by geographically separating the receiving stations from the existing transmitter sites; new receiving stations at Letterfrack, Ireland and Louisbourg, Nova Scotia effectively doubled the capacity of the Marconi Company to carry transatlantic telegraph traffic. Instead of the 500 kHz and 1 MHz frequencies common in shipboard radio at the time, Marconi was to use longwave frequencies of 37.5 kHz for transmission from Glace Bay, Cape Breton, Nova Scotia to Letterfrack and 54.5 kHz for transmission from Clifden, Ireland to Louisbourg in order to establish reliable transatlantic communication day and night.^[11]

https://www.wikiwand.com/en/List_of_Marconi_wireless_stations

[Fasturn]

I am suprized at the number of HAM's on this site. I think most played with CB radio as a kid. I did the crystal radio, CB and on to the Extra class HAM license. In 2008 I pass the T2 ( commercial telegraph license ) they wanted $68 bucks to renew so I let it lapse. Spark Gap, was the early means of wireless telegraph. Built lots of RF feeds for aero space as high as 100 GHz. As a machinist and background in RF , I could talk to the engineers when things failed.
Still like to use my 1959 blue racer bug on 7 MHz. My last home project was a 7 MHz lump loading coil for a friend ( N5QXP ) I still get a kick out of wireless com.....less the smart phone !

[The Artful Bodger]

. Spark Gap, was the early means of wireless telegraph.

Indeed it was and most of those transmitters were operating on low frequencies, i.e. long waves. The transmitters were huge both in power and physical size. The Marconi 300kW transmitter built at Carnarvon, Wales, in 1916 used rotary spark wheels of 5ft diameter and the noise of the spark discharges reputedly could be heard a kilometre away.

[Fasturn]

Indeed it was and most of those transmitters were operating on low frequencies, i.e. long waves. The transmitters were huge both in power and physical size. The Marconi 300kW transmitter built at Carnarvon, Wales, in 1916 used rotary spark wheels of 5ft diameter and the noise of the spark discharges reputedly could be heard a kilometre away.

Well well said! I was driving with a mobile radio on 14 MHz. A construction site had a pump engine running and I could hear it for 500 meters on the reciever. Broad band or harmonics , said to my self, - pulsed, this would be spark gap morse. On this site there are many that are well read with electrical, mechanical and other types of engineering. We were the STEM generation ! Now it has to be taught ? ¿

[mickeyf]

I am suprized at the number of HAM's on this site.

Shouldn't be. My observation is that people who are interested in technology at all tend to be interested in technologies in general. I messed with electronics as a kid, studied chemistry as a young adult, was a machinist apprentice for a while, finally did post grad work in Geographic Information Systems, and ended up with a career in software development.

[boslab]

I remember building a crystal radio with the kids years ago, no battery, it worked, I thought it was awesome but the kids were underwhelmed to be honest,
I remember my dad telling me about the cable radio in skewen, South Wales, it was red dragon radio, apparently the first in the U.K., perhaps the world, he used to deliver recharged glass lead acid batteries on a bicycle to run the radios, I saw one of the cells, a square glass thing, times change!
mark

[darryl]

6000 meters is 500 hz- I haven't done the math, but ok. You'd have to raise that by a factor of 100 just to get out of the audio range. And you'd still have a relatively long antenna at 60 meters. Times have changed for sure.

This low frequency reminds me of the device I built long ago to pick up audio frequency radio waves. I still have it. It's a pickup coil about two feet across, with a great many turns of wire on it. Unless I go out into the boonies, by far the largest signal I pick up is 60 hz. The circuit has a notch filter to deal with that, and let's me hear atmospheric noises that propagate at audio frequencies. If you want to learn more about that, look up Dawn Chorus. I don't know how well I can verify this, as being at home the power line noise swamps almost everything you could pick up and hear- I think I did hear this Dawn Chorus once, but there were a great many other noises- one of which I'm sure was somebody using a skilsaw somewhere nearby. I could hear lots of chirps and squeaks, some sounding interesting, some sounding like if I listened long enough, perhaps I could identify.

Another device I built was a frequency shifter that would pick up ultrasonic signals and translate them to a lower frequency. Could be interesting if I marry these two devices- maybe one day I'll do that.

[Mike Burch]

6000 meters is 500 hz- I haven't done the math, but ok. You'd have to raise that by a factor of 100 just to get out of the audio range. And you'd still have a relatively long antenna at 60 meters.

Sorry, but I think that's well adrift.

Wavelength times frequency equals velocity of propagation. Radio waves travel at the same speed as light—300,000,000 metres per second. If I divide 300,000,000 by 6,000 I get 50,000.

So a wavelength of 6,000 metres is a frequency of 50,000Hz, i.e., 50KHz. That's well above audio (in my ageing case by a whole order of magnitude!).

The wavelength of a 500Hz signal would be 600 kilometres, which would tend to preclude the use of a resonant antenna.

60 metres is the broad designation of the newest HF ham radio allowance, at five-point-mumble megahertz. The half-wave dipole antenna for that band is therefore a bit less than 30 metres long, which is relatively short.

[Fasturn]

Darryl - Mike

You guys make my head hurt. I have trouble getting on 160 meters / 1.8 MHz. 234 / 1.8 is 130ft vertical . Full 1/4 wave.
The neighbors would not like that. LoL