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Radio (shortwave, in this case), just for a change ...

You can have hours of fun these days with (clever) stuff like this:- SDR. "Click to tune"!

I know there are a few ex-Signals types about on the forum (not to mention ex-REME Tels). Also Ham Radio enthusiasts, sea-going radio operators and so forth.

So ... is anyone up for a discussion on stuff like (to name but two of the many possibilities):-

1) HF "skip-zone"
2) Shannon's Law

Happy to chat about RF propagation, sporadic E layers, zone of silence and the like but I feel in the modern age of mobile phones most people are happy just to dial/text/surf and the theory gets a little left behind.
Roughly on the subject of Shannon's law how about fun things like FEC and ARQ wrt data transmission. Are these still used in mobile applications and if not what has superseded them?
Over to you Geoff

I was boning up on HF "skip-zones" following something I saw on another forum. Blokes roaming around deserts in Land-Rovers and so forth encountering certain difficulties in that regard (no doubt you know of the type of equipment concerned - but I'm using OPSEC here, Ed). Problems when the vehicles were on the move, apparently. In other words, "battlefield" communications over both long and short distances. And where the theory is not only needed, but also gets put to good use (hopefully).

Yes; Shannon's Law is (nothing to do with the above but is ...) to do with data throughput (and the limits thereof).

Regarding the other stuff you've mentioned, that's also to do with digital transmission, I would say (that is, "modern" as far as I'm concerned). So I shall need to consult Mr.Google; but as far as I've noticed so far cell-phones don't use half-whip aerials and such like (more's the pity).

ARQ - "Say again, over"?

But what did you think of the link (SDR)? Pretty nifty, I thought.

How's your Morse these days, Ed? Still practising?

Remember that I was just a humble ECE (that is, not Tels or Radar) - although we did all sit C&G Telecommunications and Radio & Line exams (the first tech qualifications I ever attained) - but that was almost fifty years ago now (so I expect they don't use Miller oscillators et al any more). We had the Larkspur family of radios back in my day, and I'm pretty sure there's been at least two generations of kit since then (and another on the way, apparently).

< zone of silence > zzzZZZZZZ

Ahh yes the Larkspur, replaced by the Clansman if memory serves (PRC349 etc).
Don't practice the old morris code much these days but I am sure it will come in useful again following apocalypse/alien invasion/world war three when all other communication fails!
SDR is a nice piece of kit but kind of takes away the challenge of DX (long distance) reception (just log into the receiver nearest the geographical area you want to tune in to).
For anyone else who may have read the earlier post ARQ is automatic request and FEC is forward error correction, both modes used to minimise data loss in the good old days of data comms, originally used on RTTY (radioteletype). Ahh yes the good old days of AFSK/FSK and mechanical teleprinters, Creed 444 (aka the post office type 15), still got one around somewhere.

... then Bowman.

The thing about Morse is that it allows you to tap out messages on the radiator pipes. Just make sure that you avoid capture in "warmer climes" (no radiators).

Surely you have more than the one Creed, though, Ed? How else do you get reports from your outposts?

I imagine that DX-ing is great fun - but it means you have to have a load of kit, does it not (plus somewhere handy to stash it all)?

But about the apocalypse and what-have-you - yes; never allow yourself to become reliant on GPS, internet connections, and all the rest. And always have a camping stove (brew* kit) near at hand - and a butane-powered soldering iron in your toolkit.

1) More
2) Clansman
3) Bowman:- try Google!

* As in tea (not "home-brew").

Another interesting site.

And another.

BTW I've spent a bit of time trying to hound down a site about (army-style) generator* sets - eg, 10 kVA, 27.5 kVA, the (so-called) "silent generator", plus the smaller ones ... and all the rest. But I've run out of time. Does anyone know of one?

* There was a time when I was "into" generator sets; a much over-looked (but essential) "area of interest", in my humble opinion. See here for typical current (pun!) stuff.

Meanwhile, I've found that the best places to "see what's available" (and also "eye candy") for generators is eBay.

1) UK
2) US

Not familiar with generators I'm afraid although I do have a WWII German unit in running condition!
I do have nice collection of Marconi Marine equipment from Radar to HF transmitters and DF sets though so if anyone has anything Marconi to sell let me know. Some of it is for restoration when I get round to it (the usual problem).
DF (direction finding) was always interesting using the Bellini Tosi system, goniometer etc and always fascinated me. Of course you had other navigational aids, Decca, Loran etc all now sadly redundant with GPS. Mind you if the powers that be decide to screw the world up all they have to do is shift the timings so everything is 1 mile East of it's actual position. See what grinds to a halt then.
Anyway back to the original discussions here is a question. For years we heard about sun spot activity and it's effects on radio propagation etc. Have these effects been negated by the use of satellite and other super high frequency comms? Discuss.

No time to think about that one right now, Ed; hopefully someone else will pipe up (come on air?) before I get back. But off the top of my head I would say "yes" ... as I think that sunspots only affect the "lower" radio frequencies - the ones that make use of the ionosphere. In a word, HF.


But ... goniometer; the only time I've come across them was on the Milan ant-tank missile.

And ... GPS; no doubt there's a big "Off" switch somewhere. But I'll grant you that the PTB are currently doing OK in their project to screw up the world without (as yet) taking such a drastic step.

OK ... which Stromerzeuger ... manufacturer, model, year?

PS: I came across a pile of (twenty or more) Meccano Magazines from the early 1950's at a car-boot sale today. The seller wanted a quid for each of them (original price 9d. then 1/-). They were in pristine condition too. But I resisted the temptation, as I'm still trying to "simplify" (draw down) my stuff, rather than seeking a return to "collector" mode. And ... anyway!

Yes.

Bellini-Tosi? See Google. But what about huff-duff!

There are a number of forums about (old) generators - but this one could be the best.

But here's another one for you, Ed.