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Old 15th May 2019, 1:12 pm   #1
davew
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Default Short Wave listening

I was wandering round the NVCF at the weekend which always takes me back to my youth remembering about all the fun I had messing about with and building valve TXs RXs and various bits and pieces.
It got me thinking about the Radio Constructor "Discovery" SW set I built in I think 1970 and the excitement of saving pocket money and building it bit by bit - It was a 2 valve TRF set using Denco coils.
As I remember it worked pretty well but I never really got into Amateur radio in a big way always preferring to attempt to build the perfect Hi-fi!

Anyway, it got me all enthusiastic and I've decided I'd like to build another set and do a bit more Short wave exploring
My questions are (and sorry if a bit daft)

What is the state of Amateur radio now? I done a lot of looking round the net but not got any definitive "feel" of how much old style comms there still is - I've seen a lot of Software related stuff that I just don't understand.

So if I tuned my old Discovery to Top band, will I still hear much!?

Also, I fancy building a simple superhet, preferably valve - Any suggestions please?


Thanks


Dave
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Old 15th May 2019, 1:28 pm   #2
Bazz4CQJ
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Default Re: Short Wave listening

Hi Dave,

If I start by saying that I built a two-valve TRF around 1968, then that suggests we were running quite close. I had a lot of fun with that radio!

However, Amateur Radio has changed so much since then and it's hard to know where to start. But I'll begin with the "invasion" of Japanese equipment in the 1970's. Before that, people were building their own, or modifying ex MoD stuff or ex-radio telephones. Now you could get good modern gear at modest prices off the shelf. About the same time there was major shift from AM use to SSB among amateurs. I think many became disillusioned to some degree, and perhaps that's why some now enjoy restoring vintage radios.

Another change since ~1970 is that the magazines have either gone, or morphed in to rather different animals. I cannot remember when I last bought any of the surviving mags

If you've just come back to ham radio, spend a little time re-discovering it and see if you can find a niche(s) which attracts you. Activity on top band is generally low, but there are local hot spots.

B
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Old 15th May 2019, 4:07 pm   #3
G4YVM David
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Default Re: Short Wave listening

The biggest change is the appalling state of the sun...some days and nights you'll be lucky to hear ANYTHING. Mind you, other days its great. I don't think you'll be disappointed
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Old 15th May 2019, 4:32 pm   #4
HamishBoxer
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Default Re: Short Wave listening

Plenty of 20m activity every weekend calling cq contest.Round here there 2 or 3 most nights on 160m plus me once a month 2130 Sunday night reading RSGB news.

80m and 40m yes time dependant.This all ssb plus VMARS regular net on 3.615 (AM) .
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Old 15th May 2019, 7:05 pm   #5
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Default Re: Short Wave listening

If you fancy building a superhet I would just look at some domestic radio circuits of the era and modify the design to your own taste. Use an old scrap set for parts maybe? IF transformers are probably hardest to find, but the rest of the stuff can be had fairly easily. There was an excellent book called "Radio for Boys" by Bradley I think. This has all the info you need, including a mains valve superhet which I built and it works. Get the earlier version of the book as the later edition is transistor based. The addition of a BFO is probably a good idea if you want to listen to amateur transmissions. These can be added on without the complexity of product detectors, but obviously performance will be limited. All good fun particularly if you like a design challenge and experimenting a bit.
Alan.
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Old 15th May 2019, 7:12 pm   #6
ex seismic
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Default Re: Short Wave listening

There is very little amateur AM on any band nowadays except the weekly VMARS net on Saturday mornings on 3.615MHz. For a general view of what activity there is at any time look at the Hack Green web SDR site.

Domestic broadcasting on short waves is also rapidly dying but there are stations still around. The web SDR at Twente University is general coverage so includes the broadcast bands as well as amateur.
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Old 15th May 2019, 8:44 pm   #7
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Default Re: Short Wave listening

These days there's very little of interest on the shortwave broadcast-bands: the old-time 'nation state' operators [Radio Nederland etc, along with the wackier propaganda-stations] have all gone.

There's still a bunch of interesting Sunday-morning free-radio stations around 6.2 to 6.4MHz though, if you're really into 1970s/1980s music-heard-through-severe-fading!

Amateur-wise: nobody uses AM-voice these days, it's 99.99% SSB - which means you need 'tight' IF-filters, and non-drifty local-oscillators/BFOs. The biggest problem you're likely to find - irrespective of the receiver you use - is the level of QRM from plasma-TVs, light-dimmers, SMPS wall-warts etc: a good antenna can help here (magnetic-loops, for example) but the limit to weak-signal reception is no longer receiver-noise like it was decades back.
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Old 15th May 2019, 9:12 pm   #8
Bazz4CQJ
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Default Re: Short Wave listening

Who is going to tell him about SMD's ?
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Old 15th May 2019, 9:29 pm   #9
Ed_Dinning
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Default Re: Short Wave listening

Hi Dave, I think the Radio for Boys book is on the web somewhere.
Mail me when you get your design together as I may be able to help out with IFT's, tuning caps and other bits.

Cheers, Ed
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Old 15th May 2019, 11:58 pm   #10
m0cemdave
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Default Re: Short Wave listening

You will find the biggest problem on the shortwave broadcast bands is the large number of "ethernet over mains" systems now in common domestic use.
Although many of them are designed to avoid wiping out the amateur bands, nobody ever lobbied the manufacturers to protect the broadcast bands.
They sound a bit like a troop of horses clattering over cobblestones, and completely wipe out reception.

There is also a high level of what sounds like white noise which is caused by badly balanced overhead telephone lines carrying VDSL internet. This won't stop until the UK catches up with the developing world and replaces copper landlines with FTTP.

And of course all the switch mode power supplies in use in your and your neighbours' homes. Wall warts, phone chargers, general domestic electronic equipment - all made as cheaply as possible in China and much of it with no RF noise suppression. Not to mention plasma screens!

The result of the above, (unless you live in an isolated house a couple of hundred yards from anyone else) is that you need a carefully designed aerial that maximises wanted signals over general noise pickup. So at the same time as building your radio, build a loop antenna (plenty of designs on the internet) and find somewhere to install it away from all the garbage. If you don't do so, you will be very disappointed...
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Old 16th May 2019, 5:13 am   #11
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Default Re: Short Wave listening

Quote:
Originally Posted by davew View Post

Also, I fancy building a simple superhet, preferably valve - Any suggestions please?
Thanks

Dave
It is hard to go wrong building a valve based single conversion superhet. You could go with a common type of design using a 6A8 converter and 6k7 IF and a twin gang capacitor. Philco made a real beauty that covered 5.7 MHz to 18.2 as I recall in one band and the tracking errors not too extreme (look up the schematic for model 38-7).

Or, you could go down the other road like the Eddystone 640 use an RF stage like an EF39 or 6k7, converter like a 6k8 or ech35 and another 6k7 IF and go for a 3 gang variable capacitor and divide the shortwave band in two or three segments for very low tracking errors.

A lot of noise on the SW bands can be ignored by using a ferrite rod, but depending on the particular rod, over about 12MHz they lose this utility.

This home made radio goes from 5.7MHZ to 18.2MHz and uses a rod:

http://www.worldphaco.com/uploads/TH...OC16_RADIO.pdf.

(also being 12V valves you cannot zap yourself )
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Old 16th May 2019, 6:49 am   #12
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Default Re: Short Wave listening

Amateur radio has certainly changed. The biggest change recently has been the growth of FT8 and other digital modes. Like you I am not interested in those. But what it means is that the traditional modes, SSB and CW, have been largely deserted for anything like the traditional chats we used to enjoy. Tune the bands outside contest weekends and you will hear nothing at all on those modes, but as soon as you tune to the FT8 channels they are full of strong wobbly carriers. Not helped of course by the current state of the sun and lack of sunspots, but the main issue there is simply nobody on there to work.

73 Dave G3YMC
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Old 17th May 2019, 3:06 pm   #13
SteveCG
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Default Re: Short Wave listening

A few weeks ago I picked up at a car boot for not much a rather tatty 1970's ITT, made in HongKong, LW/MW/FM/SW 'rgd' branded transistor mains/portable - no model number on it (no telescopic aerial either!). Also it still had those blue and red conversion stickers the BBC produced for their wavelength changes.

Firstly I was pleased by the sound quality (a decent sized loudspeaker), secondly its SW was a band-spread 49m band (6.3 -> 5.9 Mc/s). Not much there apart from SM PSU type noises, however what there was, albeit mainly 1960s/70s/80s rock (English and German) made a refreshing change from the usual playlist of the UK domestic commercial stations.

I guess it all depends on what you want from your SW listening. I feel my money was well spent.
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