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#11
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On Sun, 7 Jan 2007 13:28:57 -0000, Steve H mycalland remove the blank@arrl .net wrote in :
"C. J. Clegg" wrote in message news ![]() Looking for the best all-tube general-coverage (0.5-30) receiver I can get. Need good operation on SSB and CW and capability on AM, along with sensitivity, stability, ruggedness, and availability of replacement parts e.g. tubes (that last one might be difficult...). I'm thinking Collins 51Jx or R-390, although I remember that I really liked an old Hammarlund I had once... Would like to stay under $1000 but if I had to I suppose I could go as high as $2000 for something that's really mint. What do you guys recommend I look for? Have a look on ebay for a RACAL RA17 , they tend to go cheaply as there are so many about. No problem with replacement valves. My correspondent in .UK who has an RA-17 _loves_ it. He has had various other fairly-good RXes, including at least one Collins 51J, but thinks his RA-17 beats them all hollow. Look up "Wadley loop"[1] for insight into why the RA-17 is pretty darned stable. Or simply look at http://www.televideo.ws/wadley.html, http://www.qsl.net/vk3jeg/b_wadley.html, and http://www.qsl.net/n4xy/rcvr_racal.html for a start. If I had house space for an RA-17, I'd be looking for one -- to go with the R-390, 2 R-390A, FRG-100, DEBEG 2000, RA-6217E, ITT/Mackay 3020, and the ricebox appliances. [1] With the quotes this time. -- Mike Andrews, W5EGO Tired old sysadmin |
#12
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On Sun, 07 Jan 2007 09:26:41 -0500, Roger D Johnson wrote:
Virtually all of the high end military vacuum tube boat anchors were designed before SSB became common. They require an external converter or the addition of a product detector and AGC mods to work properly. My Racal RA-17 works fine on SSB, you just have to remember to adjust the attenuator and/or IF gain to stop the detector overloading. Agc is switchable for short/long time constant. There are external ssb and isb adapters, the set has connectors for one, but I've not found one yet... -- Cheers, Stan Barr stanb .at. dial .dot. pipex .dot. com (Remove any digits from the addresses when mailing me.) The future was never like this! |
#13
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Mike Andrews wrote:
On Sun, 7 Jan 2007 13:28:57 -0000, Steve H mycalland remove the blank@arrl .net wrote in : Have a look on ebay for a RACAL RA17 , they tend to go cheaply as there are so many about. No problem with replacement valves. My correspondent in .UK who has an RA-17 _loves_ it. He has had various other fairly-good RXes, including at least one Collins 51J, but thinks his RA-17 beats them all hollow. Look up "Wadley loop"[1] for insight into why the RA-17 is pretty darned stable. Or simply look at http://www.televideo.ws/wadley.html, http://www.qsl.net/vk3jeg/b_wadley.html, and http://www.qsl.net/n4xy/rcvr_racal.html for a start. Yes, the Racal receivers are definitely nice, and good performers. I have a RA2617D, which is a solid state version of the RA17. It uses the same Wadley loop to create the 1 MHz hetrodynes that do the conversions for the 1 MHz bands. It is an interesting way of gaining stability from the hetrodyne conversions without requiring the hetrodyne oscillator to be especially accurate, or stable. -Chuck |
#14
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The relatively inexpensive Yaesu FRG-7 also uses the Wadley loop. It's
an excellent performer for the price (although solid state). Terry W8EJO Chuck Harris wrote: Mike Andrews wrote: On Sun, 7 Jan 2007 13:28:57 -0000, Steve H mycalland remove the blank@arrl .net wrote in : Have a look on ebay for a RACAL RA17 , they tend to go cheaply as there are so many about. No problem with replacement valves. My correspondent in .UK who has an RA-17 _loves_ it. He has had various other fairly-good RXes, including at least one Collins 51J, but thinks his RA-17 beats them all hollow. Look up "Wadley loop"[1] for insight into why the RA-17 is pretty darned stable. Or simply look at http://www.televideo.ws/wadley.html, http://www.qsl.net/vk3jeg/b_wadley.html, and http://www.qsl.net/n4xy/rcvr_racal.html for a start. Yes, the Racal receivers are definitely nice, and good performers. I have a RA2617D, which is a solid state version of the RA17. It uses the same Wadley loop to create the 1 MHz hetrodynes that do the conversions for the 1 MHz bands. It is an interesting way of gaining stability from the hetrodyne conversions without requiring the hetrodyne oscillator to be especially accurate, or stable. -Chuck |
#15
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Stan Barr wrote:
On Sun, 07 Jan 2007 09:26:41 -0500, Roger D Johnson wrote: Virtually all of the high end military vacuum tube boat anchors were designed before SSB became common. They require an external converter or the addition of a product detector and AGC mods to work properly. My Racal RA-17 works fine on SSB, you just have to remember to adjust the attenuator and/or IF gain to stop the detector overloading. Agc is switchable for short/long time constant. There are external ssb and isb adapters, the set has connectors for one, but I've not found one yet... I'll put a good word in for the RA-17 as well. Ergonomically I think it's a little better than the R-390A, and it's a lot easier to work on, though I don't think the RF performance as good. On the other hand, it's a lot better than the newer solid-state Racal receivers. I was really shocked to compare the R-17 with an R-1750 on a marine install... CW stuff that was easy to copy on the R-17 was down in the noise floor on the newer receiver. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#16
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On 7 Jan 2007 10:15:35 -0800, Nomad wrote:
The relatively inexpensive Yaesu FRG-7 also uses the Wadley loop. It's an excellent performer for the price (although solid state). Somebody once wrote about them that Yaesu were so pleased at getting the Barlow-Wadley loop working in solid-state that they forgot to give the receiver any rf performance :-) There's a whole raft of mods to bring it up to scratch though... -- Cheers, Stan Barr stanb .at. dial .dot. pipex .dot. com (Remove any digits from the addresses when mailing me.) The future was never like this! |
#17
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Stan Barr ) writes:
On 7 Jan 2007 10:15:35 -0800, Nomad wrote: The relatively inexpensive Yaesu FRG-7 also uses the Wadley loop. It's an excellent performer for the price (although solid state). Somebody once wrote about them that Yaesu were so pleased at getting the Barlow-Wadley loop working in solid-state that they forgot to give the receiver any rf performance :-) There's a whole raft of mods to bring it up to scratch though... The Wadley loop is often seen in mystical terms, presumably because people aren't bothering to understand it. Obviously, it was a way in the fifties to get rid of that need for crystals every 500KHz, yet in retrospect I'm not sure that the effort couldn't have been put into a synthesizer. After all, generating a first mixer signal every 500KHz requires about the same circuitry if done with a PLL. A few years later there were receivers that used PLLs for such signals, though over the years I've seen posts where people mistake those PLLs with Wadley loops. The problem with the Wadley loop is that it puts at least an extra mixer in the signal path, and by definition you can't put ultimate selectivity until three mixers down. Done right, as I'm sure it was done in the Racal receivers, it works. But done carelessly, and you have a receiver that uses a more esoteric design but automatically comes out worse than something done a different way. After the Racal, it mostly seems to have been used to cut costs, but once you reduce costs the extra mixers in the signal path are a liability. Moving the "synthesizer" out of the signal path means you don't have that extra mixer in the signal path. And I'm not convinced that making a decent PLL that only has to generate signals every 500KHz is harder than all the filtering and isolation that the Wadley loop requires. People have confused the PLL in the HRO-500 and the mix-sixties Galaxy receiver with the Wadley loop because on some level they are similar. I've explained the Wadley loop in the past so I'm not going to explain it again, but the HRO-500 PLL used a crystal oscillator at 500KHz, generated lots of harmonics, and then the variable oscillator would be locked to the harmonic of the reference. You'd be tuning the oscillator with a manual variable capacitor, with a small varicap to actually tune it to look by the voltage out of the phase detector. There is similarity to the Wadley loop, but they aren't the same thing, and you get the "synthesizer" out of the signal path in the receiver. The circuitry would be about the same, if not a tad simpler, for the PLL. SO in the end, I'm not convinced of the Wadley loop being anything more than a neat trick, which at first seemed like a great solution in the fifties but in retrospect may not have been. Come the seventies with the FRG-7, there ultimately was no good reason to use the Wadley loop in there, and using a PLL might have given it better specs. Michael VE2BVW |
#18
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On 7 Jan 2007 13:43:22 -0500, Scott Dorsey wrote:
I'll put a good word in for the RA-17 as well. Ergonomically I think it's a little better than the R-390A, and it's a lot easier to work on, though I don't think the RF performance as good. There's no doubt the 390 has better if filters than the Racal. On the other hand, it's a lot better than the newer solid-state Racal receivers. I was really shocked to compare the R-17 with an R-1750 on a marine install... CW stuff that was easy to copy on the R-17 was down in the noise floor on the newer receiver. My RA-17 is racked up with a RA-1792, (synthesised solid-state, mine has provision for remote control and modified eproms to allow tuning down to 0Hz!) the 1792 has better performance than the 17 but I still prefer the older rx for general tuning around. -- Cheers, Stan Barr stanb .at. dial .dot. pipex .dot. com (Remove any digits from the addresses when mailing me.) The future was never like this! |
#19
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Stan Barr wrote:
My RA-17 is racked up with a RA-1792, (synthesised solid-state, mine has provision for remote control and modified eproms to allow tuning down to 0Hz!) the 1792 has better performance than the 17 but I still prefer the older rx for general tuning around. Try working one channel while an adjacent transmitter is operating a few hundred KC away and you'll see why the RA-17 beats the RA-1792 for full-duplex radiotelephone service hands down. The filters on the RA-1792 sure are nicer than on the RA-17, though, and consequently audio quality on SSB is a whole lot better with less noise. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
#20
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On Sun, 07 Jan 2007 08:49:06 -0500, K3HVG wrote:
What's not been said is what you really want to do with the gear. Is it simple short-wave listening or serious collecting? Good evening, Jeep. Technically, it's neither, but it's more the former than the latter. I need something that can be used on certain military HF networks outside the amateur bands. I have been told that (for some goofball reason) I'm not allowed to say exactly which networks, but it isn't anything that would be particularly hard to guess if anyone cared to give it a few minutes of thought. :-) The main reason I want old and all tubes and etc. is something I hesitate to mention, because every time I do, I get ridiculed as a Chicken Little and a paranoid (though, as we all know, it ain't paranoia if the sonsabitches really are out to get you!). I firmly believe, in my heart of hearts, that sooner rather than later the United States (which, to answer your other question, is the side of the pond I'm on) will receive one or more nuclear attacks. It could be a 10-kiloton device that gets smuggled into downtown Washington in the back of an SUV, or it could be a Jericho-style widespread attack, or anything in between. When that happens, much of the solid state gear (radios, computers, cell phones, the Internet, packet BBSs, etc.) within a fairly large radius of ground zero will be reduced to doorstops and paperweights. Assuming I'm still around after the attack, and since I'm within reasonable EMP distance of a few large cities, I would like to have set up at least a basic communications capability that has a chance of surviving that. A really good receiver is a first step that, as you all have noted, shouldn't cost too much. Of course, that begs the question of how I'm going to power the damn thing if commercial power is down, but I guess I'll have to, as they say, jump off of that bridge when I come to it. Anyway, I really do like the old gear, and though I'll almost certainly never be a serious collector, I wouldn't mind having, up and running, a few quality pieces from back in the day. |
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