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Old 1st Dec 2017, 6:20 pm   #21
Philips210
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Hi Bazz.

Yes that could be a little problem finding the correct socket at a reasonable price. I suppose it's feasible to make something suitable using individual sockets set in a resin to the lead pattern of the 6CW4.

Regards
Symon.
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Old 1st Dec 2017, 6:23 pm   #22
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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Symon, you'll need a socket for the Nuvistor and, they're around but not common. The last ones I saw online (some time ago) were being sold in packs of 4 for 22.
Wow, that's steep. I've sent the Nuvistor now...

I'm sure someone on the forum has one.

It's not a show-stopper, in any case. They're tiny and the leads need to be short because of the frequencies involved. It would be possible to make a case or solder directly to the pins.
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Old 1st Dec 2017, 10:24 pm   #23
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Of course, many of the Soviet Nuvistor clones have wire-ended connections. I've never used one, but it is probably quite a good idea. If you drill a hole through a piece of copper-clad board, you can sit the Nuvistor in that with the bottom of it just slightly higher than the copper. The leads then come out at 'component height' on the board. That's what I've done a couple of times with socket type Nuvistors. My last Nuvistor project was about a year ago, when Skywave and I were in pursuit of sensitive, wide-range RF voltmeters, an area where outcomes were mostly quite disappointing .

Was it just coincidence that this thread started with a mention of Voyager, and BBC4 showed a truly excellent documentary about Voyager last night?
Don't think I learned much that was new, but sat riveted to the TV. One bit that was new was the last minute panic, prior to launch, which lead to them wrapping lots of wiring in the spacecraft using "Bacofoil" from the corner store just down the road from JPL. They conceded that some standard design and procurement procedures at JPL may not have been "fully" complied with during that activity!

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Old 1st Dec 2017, 11:30 pm   #24
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Quote:
Originally Posted by G6Tanuki
For reference, here's a grabbed-from-a-1970s-RSGB-publication table of noise-figures of RF amplifiers and mixers.
Those figures are actually equivalent noise resistance. That is, the resistor which if connected to the grid (at room temperature) would generate the same noise in the anode current as the valve itself.

Quote:
Originally Posted by Radio_Wrangler
The 7360 makes a good showing as well.
I suspect that figure just treats the 7360 as a pentode. I think there would also be a contribution from partition noise between the two anodes. If the 7360 really has a noise resistance as low as 1500 then it would be easy to make a sensitive HF receiver with it, but anecdotal evidence is that you need very tight coupling and very good matching in the input RF circuit - unlike a normal RF pentode where looser coupling and approximate matching is good enough.

The other thing to say is that the table gives HF performance (shot and partition noise). For VHF and up you also need to take account of grid noise and grid input conductance. That is where valves like the 6AK5 score: at HF it is no better than many RF pentodes (and worse than some) but it deteriorates less as the frequency goes up.
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Old 2nd Dec 2017, 4:33 pm   #25
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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Originally Posted by Bazz4CQJ View Post
Of course, many of the Soviet Nuvistor clones have wire-ended connections. I've never used one, but it is probably quite a good idea.
Thanks! I hope Symon can source a real one but tbh I think this method would work just as well and would be aesthetically identical.

Quote:
Originally Posted by Bazz4CQJ View Post
Was it just coincidence that this thread started with a mention of Voyager, and BBC4 showed a truly excellent documentary about Voyager last night?

Don't think I learned much that was new, but sat riveted to the TV. One bit that was new was the last minute panic, prior to launch, which lead to them wrapping lots of wiring in the spacecraft using "Bacofoil" from the corner store just down the road from JPL.
Ahaha, no, it wasn't a coincidence! They must have read the thread (correlation/ causation joke!) I did know about the doc and thought it would be nice to get something going. And I did enjoy remembering my investigation of tiny signals from space.

Not everyone 'gets' this as this space listening isn't communicating intelligence/ what we define as 'meaning', but just as I enjoy the challenges of controlling unwieldy amounts of power electronically, so do I enjoy the other end of the spectrum, seeing uV or uA signals in a receiver front end!
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Old 2nd Dec 2017, 6:00 pm   #26
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Curiously, there was a brief mention of one Voyager on the news today. It seems that the main thrusters, used to orient the spacecraft to point its antenna towards home, are degrading. So for the first time since 1980, they tried firing the backup set and they performed 100%. Way to go !

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Old 2nd Dec 2017, 10:49 pm   #27
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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So for the first time since 1980, they tried firing the backup set and they performed 100%. Way to go!
I agree with that.

Imagine how beautifully made this spacecraft is both with the physical construction and the electronics. Probably has radiation hardened TTL's for a lot of its logic circuitry and more than likely the entire craft does not contain a single electrolytic capacitor !
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Old 2nd Dec 2017, 11:50 pm   #28
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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Imagine how beautifully made this spacecraft is both with the physical construction and the electronics.
Indeed, I can imagine. I would just love to see photographs of the electronics - and also the wiring loom.

Avionics wiring looms seem fascinatingly complex and intricate, to me, almost like a being... I remember seeing a cross-section of I think an Avro Vulcan, just incredible.
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Old 3rd Dec 2017, 2:56 am   #29
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

I've attached an image of a 1969 vintage Intelsat 3 satellite, which gives an idea of the internal construction standards.

I was told that one of my electronic dynamo regulator designs for vintage cars got built in the Intelsat workshops by an engineer who was a British car enthusiast, but I never got to see a photo of it, no doubt it would have been better made than anything I could have dreamed of.
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Old 3rd Dec 2017, 6:05 pm   #30
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Even more interesting; probably the biggest techonolgical secret this country ever had was the 1970’s-80’s “Chevaline” project. This was a UK-designed mid-life update for the Polaris nuclear missile. These days you can find endless pages about it via Google. But at the time, it was most secret, mainly because successive Governments hid the huge cost (mostly over-spend) from Parliament for the best part of a decade. Only Mrs T had the nerve to finally make it public.

There’s an overview here https://en.wikipedia.org/wiki/Chevalineand some pictures here https://fas.org/nuke/guide/uk/slbm/chevaline.html. Unfortunately no clear pictures of the electronics, but discrete components on solder-tag boards were predominant. It's important to recall, this unit was effectively a fully stabilised spacecraft, albeit one which spent a very short time in space!

It was replaced by Trident around about 1992 and many people were “a bit surprised” that a number of the Chevaline vehicles (minus their shrouds and fully exposed as in the pictures above) were soon put on display in museums (I was there on the first day they were on display). After some months, however, these were hastily withdrawn from display, had various bits removed and then returned to the museums. Of course, these days, we just buy stuff from overseas.

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Old 3rd Dec 2017, 6:08 pm   #31
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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I've attached an image of a 1969 vintage Intelsat 3 satellite, which gives an idea of the internal construction standards.
Breathtaking work there, thanks for the pic! This is very much 'my' era. I was six years old at the time, very impressed by tech and extremely fascinated by these forays for years after. I was just starting to dissassemble my first valve radio to see what was inside.

It was quite a careful dissection for my age and I kept the most impressive looking components and tried to find out what they did: not easy as I didn't have a mentor of any kind, but I was quite patient. I remember being very intrigued by the big multi-gang tuning capacitor as well as by the internal construction of the valves.
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Old 3rd Dec 2017, 6:21 pm   #32
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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Originally Posted by Bazz4CQJ View Post
It's important to recall, this unit was effectively a fully stabilised spacecraft, albeit one which spent a very short time in space!
I'm reminded of a [possibly apocryphal] Zen-tech story where a weapons-guidance-electronics type from one of the big manufacturers was explaining the design of part of his guidance-system - where he described in great detail the attention he'd paid (and the money spent) to ensure his missile would be really stable and repeatable in service.

Someone asked him "How long will this equipment be live for?"

He replied "something like 20 years" at which point his questioner said "if it takes 20 years from launch for your missile to hit its target your company's out of the contract!".

Strategic nuclear missiles - do they come with an "Explode-by" date??
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Old 3rd Dec 2017, 8:17 pm   #33
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Just a tip if anyone wants nuvistors: look out for Tektronix 1A1 or dead 453’s with serial numbers less than 20,000. They have two socketed nuvistors in the front end and a whole world of reusable parts. If they are beyond repair it makes sense to recycle accordingly.

I’m ashamed to say I had six dismantled 1A1’s I got in an eBay auction for 5 which were stuffed with nuvistors and sockets. They went back on eBay thinking I’d never have a use for them. Went for 75. Nearly fell off my perch!
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Old 3rd Dec 2017, 8:50 pm   #34
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

I'd like to stick up for the humble field-effect transistor.

There have been some very good FET-based VHF converters over the years. Many from a period now considered classic. They're in the RSGB handbooks, or the circuits of the microwave modules ones can be found. If you want to be very posh, you could clone one of the Mutek front-ends. Chris Bartram made a very good job of those.

Low noise small signal VHF work is where transistors are getting into their strengths and valves are starting to have difficulties.

In order to be a compleat electronics guy, you need to understand valve gear because there is still a lot of nice classic valve gear around. But you also have to understand transistor stuff because it has some great tricks up its sleeve and there is also some rather nice solid state gear around. Both sorts have some real stinkers, of course.

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Old 4th Dec 2017, 4:12 pm   #35
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

Must admit, for VHF converters I always liked the double-balanced-diode-mixer approach [MD108/SBL1 etc] - their strong-signal-handling capacity being a particular feature, important if you've got any powerful two-way or broadcast-transmitters in the area.

One of these with a low-gain RF amp [grounded-grid/gate/emitter stage according to taste?] coupled with loads of local oscillator drive to ensure the mixer really *is* being switched by what amounts to a square-wave, will get you going.

I did once build a VHF converter with push-pull 6J6 double-triodes as RF amp and mixer, as the only way to hear 2-Metre signals when I was line-of-sight to the Blaenplwyf VHF Band-II transmitter and its hundreds of Kilowatts.....
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Old 4th Dec 2017, 4:46 pm   #36
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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In order to be a compleat electronics guy... you also have to understand transistor stuff because it has some great tricks up its sleeve and there is also some rather nice solid state gear around. Both sorts have some real stinkers, of course.
David
But David, some of just want to be amateurs, hobbyists. We made conscious decisions not to be professional electronics engineers. Achieving the sort of understanding that people like you have of state of the art "transistor stuff" is very hard to do. I recall when Skywave had his thread about RF voltmeters and someone modelled a FET circuit and said it showed 'negative resistance', I sighed deeply; I'd just got to grips with 'imaginary impedance'. Not everyone on the forum wants or can be a "complete electronics guy" - that's why you and others are so useful, to help us lesser mortals .

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Old 4th Dec 2017, 5:43 pm   #37
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Default Re: Home brew converter to listen to Satellites, plus capture of Voyager TX by NASA

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I was told that one of my electronic dynamo regulator designs for vintage cars got built in the Intelsat workshops by an engineer who was a British car enthusiast, but I never got to see a photo of it, no doubt it would have been better made than anything I could have dreamed of.
Now I can place you.

Best not to discuss cars in these forums though.
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