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Homebrew Equipment A place to show, design and discuss the weird and wonderful electronic creations from the hands of individual members. |
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12th Nov 2008, 10:11 pm | #1 |
Hexode
Join Date: Jan 2007
Location: Weeting, Norfolk.
Posts: 465
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Glowbugs.
Two simple CW xtal-control transmitters, each for the 40mb, that I have built over the last two nights. One is a home design using an EL90 that is to be used at our club room (henced supervised operation - will have to wait untill my intermediate to use it here) and the other is a kit-built design using a H7A (12K5) putting out approx 200mw (comparable to the Pixie QRP set) using a 12V power supply.
I was wondering if any forum members have operated similar sets and how they've got on? The EL90 set - expected output around 1-1.5 watts with 250 DC on the plates. Now needs some tidy up work to keep fingers away from HT. Filament provided by a single PP3. The crystal socket is an old valve base. This was built entirely from my scrap box, with the exception of the ceramic base. I have one spare (B7G size) should anyone want it. http://i148.photobucket.com/albums/s...g/DSCF0572.jpg The 12K5 'Hollow Pixie'. Both plates and filament use 12V DC. The crystal soldered in is 7.040KHZ. I might wind another coil and try it on 20mb as well http://i148.photobucket.com/albums/s...g/DSCF0574.jpg
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Real radios glow in the dark M6GLD |
12th Nov 2008, 10:21 pm | #2 |
Rest in Peace
Join Date: Jul 2004
Location: Dartford, Kent, UK.
Posts: 1,661
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Re: Glowbugs.
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12th Nov 2008, 10:31 pm | #3 |
Hexode
Join Date: Jan 2007
Location: Weeting, Norfolk.
Posts: 465
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Re: Glowbugs.
I can't - simple answer! Instead the battery EMF drops it down to around 7.5V (fresh battery) and runs for around 3 hours or so. The heater glows quite bright for the first few hours of use. I assume that there is enough emission there for this set to work, but its all very experimental. I haven't built a PSU for it yet either, but I have an EZ81 tucked away for that. If I can find an old transformer I might be lucky enough to get one with a filament winding.
Regards, Robs
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Real radios glow in the dark M6GLD |
7th Dec 2008, 4:11 pm | #4 |
Retired Dormant Member
Join Date: Dec 2008
Location: Tournon D'Agenais, France
Posts: 5
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Re: Glowbugs.
Re Glowbugs
Astonishing construction technique ! Its a VERY long time since I saw a bread board hay-wired like that !! Norman Wells |
8th Dec 2008, 1:42 am | #5 |
Hexode
Join Date: May 2005
Location: Wigan, Greater Manchester, UK.
Posts: 479
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Re: Glowbugs.
I like the use of the Fahnestock clip in the project, in fact, I'd like to see more outlets for this simple device, a very useful piece of equipment for breadboard design.
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12th Dec 2008, 11:48 pm | #6 |
Hexode
Join Date: Jan 2007
Location: Weeting, Norfolk.
Posts: 465
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Re: Glowbugs.
Norman:
As you can see, I put an awful lot of thought into the planning.... Exposed wiring and HT are not a good mix, this set now has all live points covered up. A suitable DC PSU is next on the list. Alf: Thankyou with regards the clips - I can't see why they are not more widely used! I have seperated the filament and voltage rails on this kit now and with 20-30vdc on the plate I can push output into the 300-450mW range (Yes - just under half a watt!) I have made a handful of local contacts with this TX but it needs a decent antenna. With it able to operate off 12v I aim to do some portable working... Regards, Robs
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Real radios glow in the dark M6GLD |