Hello from Lincolnshire.

Oh hello - you must be new. Introduce yourself to the radio world here!
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BPMR_Lincs
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Hello from Lincolnshire.

Post by BPMR_Lincs » Wed May 31, 2017 8:36 pm

Just to say hello, I'm not going to be building any multi-watt transmitters with large antenna arrays, just looking to build a low power Medium Wave AM 'exciter' capable of driving a noise free signal into my collection of valve radios now that AM has all but shut down.

If I had the room I'd like to scale up to a few watts of RF that might make it across 5 miles of flat Lincolnshire coastal area. As I don't I probably won't get this ambitious.

I did have an FM station which put out around 30W of stereo (when I had the stereo encoder available!) for an input of probably 1kW of electricity supply that used four output stages from PYE Westminster PMR radios connected in series and seriously over driven on the supplies. Those QQV06 valves took some hammer...

Still, hello, I'm not that good with RF design so sticking to low power is probably safest.

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teckniqs
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Re: Hello from Lincolnshire.

Post by teckniqs » Wed May 31, 2017 11:09 pm

MW hasn't been shut down in Lincolnshire.

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radionortheast
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Re: Hello from Lincolnshire.

Post by radionortheast » Fri Jun 02, 2017 6:27 pm

hello sstrans have transmitter kits that could cover a house, you get few streets away if you knew what you where doing had space for an aerial

BPMR_Lincs
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Re: Hello from Lincolnshire.

Post by BPMR_Lincs » Sat Jun 03, 2017 2:56 pm

teckniqs wrote:
Wed May 31, 2017 11:09 pm
MW hasn't been shut down in Lincolnshire.
Ha! There isn't anything left that you'd want to listen to on AM that's for certain. Even if I liked listening to whatever it is that took over Virgin 1215 (which I don't) the signal is very weak and subject to interference, after that and Radio 5 Live (which fades in and out chronically on both frequencies) what else is left? Radio Lincolnshire (Yuk!) if they're still on AM? Nothing much else makes it out here, in any kind of signal quality.

I used to like to listen to Arrow Rock from the Netherlands, but they've closed their AM frequency.

If only Union Jack had an AM licence...

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Re: Hello from Lincolnshire.

Post by BPMR_Lincs » Sat Jun 03, 2017 4:44 pm

radionortheast wrote:
Fri Jun 02, 2017 6:27 pm
hello sstrans have transmitter kits that could cover a house, you get few streets away if you knew what you where doing had space for an aerial
In a first floor flat, I have zero room for any realistic aerial sadly.

I've seen the SSTRAN kits, they look good, but I wonder if they'd be much of an improvement (with little or no aerial) over my (self designed and built) very low power AM transmitter. This is not much more than an oscillator, modulated and fed into a wire stretched around the cornice of the flat. This works (importantly it sounds excellent) but is on a fixed frequency which isn't on any 9kHz channel, this isn't a problem for the valve radios as they don't care about 9kHz spacing, but I would like to put it on a channel if only for my later transistorised collection. I built a synthesiser which allows me to select a frequency at will, but it has a whine permanently in the background which I never managed to eliminate, this makes it rather worse than my own design once modulated as it sounds terrible in the background, whistling away.

I have it in mind to build a 4060/4046/40103/4053 PLL/Modulator similar to that suggested by Albert H in this post: viewtopic.php?f=11&t=1598#p17429 but using a 4053 as a gated AM modulator.

It was a search for this that led me to this site. I initially plan to build it without such a high power output stage, at the moment I'm waiting for the crystal and some of the ICs to arrive. If the performance of this isn't adequate for covering the flat with signal, I might be able to utilise the PLL section and use it unmodulated to drive the output stage with modulator of Albert's design.

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Re: Hello from Lincolnshire.

Post by BPMR_Lincs » Sat Jun 03, 2017 4:54 pm

Should anyone be interested, here is the very simple 'Transmitter" I'm currently using. Very low output power, but no inductors required. Superb audio quality.
My_AM_TX.jpg
The 2n2219 transistors could be replaced with any similar medium power NPN transistors. The modulator transistor T1 will benefit from a small heatsink as it runs warm to the touch. The crystal oscillator came from an old PC motherboard, it possibly should be run at less than 12V but it has been working for a number of years like this and despite getting very hot hasn't blown up yet. Of course the 4060 could have it's own crystal, but at the time I made it, I didn't have one suitable to hand, and did have the 25MHz oscillator package.
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radionortheast
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Re: Hello from Lincolnshire.

Post by radionortheast » Sun Jun 04, 2017 10:07 am

my first transmitter that went beyond the town used 2n2219, fm transmitter, it would come clearly in the park mile away else where you had to be on the ley side of a hill, it was exciting when it started reaching outside of the town, even if was weak. It was a very tempremental transmitter, would settle down after abit, leaving on, guess worry and excitement where the samething, wondering what had happened when i couldn’t hear it. I would often find the transistor had bubbled and turned a dark grey, other times it was the resistor would burn, really worried me the day local radio station began testing on the same channel, was on the other side of leeds bradford at the time trying my luck trying to hear the signal, i was bit far away the power was too low, year or 2 later did suceed, with 1w vco it was pretty much a god sent after the crude transmitter i’d been using, never repeated the range with 1w since.

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Re: Hello from Lincolnshire.

Post by Albert H » Sun Jun 11, 2017 4:15 am

teckniqs wrote:
Wed May 31, 2017 11:09 pm
MW hasn't been shut down in Lincolnshire.
Medium Wave is almost dead in much of Europe. The French shut down all their dozens of stations earlier in the year, and there's only multiple "Gold", TalkSport and God Botherers unless you speak asian languages.

I think it's time for some Medium Wave fun! Rigs are easy to build. but aerials are big. There are ways of making (relatively) short but quite efficient aerials......

I put a relatively simple synthesised rig on here a short while ago, and everyone complained that it was too complicated. I'll put up a dead simple rig that anyone who can solder will be able to make.
Is it meant to smoke like that? :shock:

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Re: Hello from Lincolnshire.

Post by Albert H » Sun Jun 11, 2017 4:20 am

BPMR_Lincs wrote:
Sat Jun 03, 2017 4:44 pm
I built a synthesiser which allows me to select a frequency at will, but it has a whine permanently in the background which I never managed to eliminate, this makes it rather worse than my own design once modulated as it sounds terrible in the background, whistling away.
The whistle is probably because your reference is off frequency! Have you got a frequency counter? If not, switch your synthesiser to the same frequency as the weaker Radio 5 at your place. Tweak the reference for zero beat. You'll then find that whatever frequency you dial up will be accurate.
Is it meant to smoke like that? :shock:

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