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Tube equipment question
Solid state transmitters are notoriously finicky about matching to the
antenna. Tube equipment is not, so I am told, and early experience seems to bear that out. Certainly I can see one of my newer rigs start to fold back at 2:1. What are the practical limitations of the Tube finals apparent flexibility? Is it safe to compare the load, plate, and drive controls to some of the functions of a tuner? (possible real dumb question) - 73 de Mike KB3EIA - |
Tube equipment question
On Mar 4, 9:48?am, Mike Coslo wrote:
Solid state transmitters are notoriously finicky about matching to the antenna. Tube equipment is not, so I am told, and early experience seems to bear that out. I disagree some with that, having entered HF radio comms QSYing 1- to 15-KW transmitters. Failure to properly neutralize a final RF amp can result in heating sufficient to melt the glass envelope enough to let air in and thus destroy the tube (an 833 that was mounted on the control console at Army station ADA for weeks as a reminder). Certainly I can see one of my newer rigs start to fold back at 2:1. That's a somewhat arbitrary level that is designed into most solid-state PAs. One can run them without the VSWR sensing but it isn't a good idea. For one thing, RF power transistors are expensive and replacement is not the relatively easy task of just unplugging the old tube and plugging in the new one. It's a mechanical task and one has to remember to properly heat-couple the new PA transistor...the amount of waste heat is concentrated in a much smaller space than big tube envelopes-bases. What are the practical limitations of the Tube finals apparent flexibility? That's in many decades of old literature and covered extensively. Data from commercial service transmitters is more comprehensive than amateur types as a general rule. Some of that may be hard to get now. Is it safe to compare the load, plate, and drive controls to some of the functions of a tuner? (possible real dumb question) Not dumb, it's more like comparing potatoes and peas. The long-common tube tuning controls are directly connected to variable, relatively narrow-band tuning and impedance-matching passive circuits. The tube plate source impedance is relatively high compared to the antenna feedline, even if that feedline is 600 Ohms balanced. The common pi-network is both a resonating network and an impedance-changing circuit. An antenna tuner is very simlar to a tube pi-network but operates either to change (narrowband) impedances up or down relative to the feedline characteristic impedance. Again, passive components do the work of transformation. By contrast, most of the solid-state power amplifiers are broadband, much more so than common tube circuits. Since their input-output impedances are relatively low and known (and predictable) over a wide frequency range, they can use broadband transformers for matching. The end result in the design is one without many of the tube controls' necessity. Usually, but not always, either type of amplifier is still suceptible to damage from mismatching load impedances. The mismatching just takes on a slightly different form between the two. 73, Remember: All electronics works by smoke. If the smoke gets out, it won't work... :-) |
Tube equipment question
On Mar 4, 12:48?pm, Mike Coslo wrote:
Solid state transmitters are notoriously finicky about matching to the antenna. Tube equipment is not, so I am told, and early experience seems to bear that out. IMHO, it's really a matter of the actual circumstances. As far back as the late 1950s there were hollow-state ham rigs made that were meant for 50 ohm loads only. In fact, there were some HF tube ham rigs made that required no conventional tuneup at all (CE 100V, 200V, 600L). Certainly I can see one of my newer rigs start to fold back at 2:1. Most hollow-state ham rigs can handle 2:1 SWR no problem. Sometimes there is less tolerance for loads that are highly reactive, though. What are the practical limitations of the Tube finals apparent flexibility? It's really a matter of how the rig was designed. Many 1950s hollow-state ham rigs were built with pi-networks that could match a wide variety of loads efficiently. The EF Johnson Viking 2 is a classic example of that type. Many homebrew designs also had such pi-networks. The problem is that the components for such a wide-range network tend to be large, heavy and expensive. So in the late 1950s and early 1960s, rigmakers designed more for compactness than for wide matching range. Still, the typical ham rig of those days could usually handle SWR of 2:1 or less with no problems. Is it safe to compare the load, plate, and drive controls to some of the functions of a tuner? (possible real dumb question) Not a dumb question at all IMHO. The short answer is "no". Tuning up a hollowstate ham rig is a similar but not identical to adjusting the typical tuner. Some may tell you that all it takes to tune up a tube transmitter is to "peak the grid and dip the plate", but that's simply not correct. Tuneup procedures vary according to rig design and you have to be specific. Of course once you get the hang of it, the procedure rapidly becomes second nature. What specific hollowstate rigs are you considering? 73 de Jim, N2EY |
Tube equipment question
On Mar 4, 5:48 pm, Mike Coslo wrote:
Solid state transmitters are notoriously finicky about matching to the antenna. Tube equipment is not, so I am told, and early experience seems to bear that out. I don't know if "finicky" is a good term, Mike. "Different" might be the best word to use. Transmitters with vacuum tube finals can match a wider range as a rule, but there is a limit to what they can handle. Some of the older Johnson and Globe/WRL rigs matched a wider range than some of the other brands. Certainly I can see one of my newer rigs start to fold back at 2:1. Most Japanese gear is designed to do just what you're experiencing. That's a form of protection for the final transistors. Ten-Tec does it differently. Ten-Tec rigs do not start to reduce power. They depend upon the supply to fault and trip if too much current is drawn. That's why it is important to use a Ten-Tec supply with them or to use a fast breaker rated to trip near the maximum current draw expected of the transmitter. What are the practical limitations of the Tube finals apparent flexibility? That depends entirely upon the design specifications set by the manufacturer. If the manufacturer's manual says "45-90 ohms", that's the practical limitation. Some of those old Globe transmitters used to have ranges of up to 1000 or 2000 ohms as I recall. At the other end of the spectrum, Hallicrafters produced some transmitters without even a loading control. These were designed to be used with an antenna presenting something very close to 50 or 75 ohms. Is it safe to compare the load, plate, and drive controls to some of the functions of a tuner? (possible real dumb question) Not the "drive" control, but certainly the other controls of a tuner could be considered comparable to the "tune" and "load" controls. If the only antennas we have are trapped verticals, tribanders or dipoles/inverted vees cut for the band to be used, we might get away with not having to use a tuner at all. Still there are likely to be frequencies significantly removed from the antenna's resonant frequency where one might need a tuner to enable the transmitter to make full power. We aren't likely to need a wide range tuner for those times. A simple T-match will likely enable us to find a combination of settings which will present a low VSWR to the transmitter. The main alternative is to have a variety of antennas which present a VSWR of under 2:1 to a transmitter. Dave K8MN |
Tube equipment question
Mike Coslo wrote:
Solid state transmitters are notoriously finicky about matching to the antenna. Tube equipment is not, so I am told, and early experience seems to bear that out. Certainly I can see one of my newer rigs start to fold back at 2:1. What are the practical limitations of the Tube finals apparent flexibility? Is it safe to compare the load, plate, and drive controls to some of the functions of a tuner? (possible real dumb question) - 73 de Mike KB3EIA - Most quality built amps will cover 2-30mhz, they only need the proper filters behind 'em to keep 'em clean, and of course, you exciter needs to put out a clean sig. Motorola has a great circuit using four 250W transistors to get you a kilo. It can be found on the web. There are scores of tech papers by motorola on 100W to 1K and beyond amps, a little research on the web should discover them. JS -- http://assemblywizard.tekcities.com |
Tube equipment question
On Mar 4, 12:53?pm, wrote:
On Mar 4, 12:48?pm, Mike Coslo wrote: Some may tell you that all it takes to tune up a tube transmitter is to "peak the grid and dip the plate", but that's simply not correct. Tuneup procedures vary according to rig design and you have to be specific. Sorry, but that was procedure for pre-WW2 high- power HF transmitters. While it is a simplistic phrase, it still applies. A more exact procedure was to tune up the exciter with reduced drive power and literally peak the grid current. Plate current was then observed with the plate tuning adjusted for a slight, but observable dip in plate current. Of (perhaps) greater importance was setting the neutralizing control for minimum grid current; "dipping" the plate current should produce the least grid current peak on adjusting the plate tuning. For best results on setting the load-side capacitor of the common pi-network without a bidirectional power meter, a detector way out in the field with meter next to the transmitter is the simplest way to "tune" that capacitor. However, with about 34+ other high-power transmitters all in the antenna field, that is impractical; presets for that control would suffice. The load capacitor of a pi-net has the least effect on tuning to a new frequency. When someone does about two QSYs per shift on at least 15 different transmitters with pi-network output circuits (all with vacuum tube PAs), yes, one "gets used to it" but what I described was the correct phrase. The pi-network has been around and used in HF transmitters since at least the late 1930s and has survived past the start of the semiconductor era. However, the convenience of broadband transistor power amplifiers has pretty much tossed that whole tube tuning procedure. Used with a Bruene detector sensor for an automatic antenna tuner, it makes QSYing a snap, even jumping bands (with a broad- band antenna, of course). "Peak the grid and dip the plate" is an old correct phrase. It will be found mentioned in the current US amateur radio question pools. Yes, there are exceptions. I was once involved with a distributed amplifier design that would cover over an octave of spectrum using tubes and was NOT tuned at all in normal operation. Since that one involved over a dozen vacuum tubes (ceramic-metal medium-power types), it would not be suitable for ordinary amateur radio HF transmitter stations. The vertical amplifier of the old Tektronix 54n series oscilloscopes used push-pull tube-type (all glass envelope "receiving" type) distributed vertical deflection amplifier. The pi-network output circuit was a favorite among amateur homebrewers for decades due to its simplicity and better ability to attenuate harmonics, that coming to be more and more prominent in regulations as HF users became more plentiful. |
Tube equipment question
" wrote in
ups.com: Failure to properly neutralize a final RF amp can result in heating sufficient to melt the glass envelope enough to let air in and thus destroy the tube (an 833 that was mounted on the control console at Army station ADA for weeks as a reminder). I would also suspect that when dealing with 15 KW transmitters, errors would be pretty unforgiving. What are the practical limitations of the Tube finals apparent flexibility? That's in many decades of old literature and covered extensively. Data from commercial service transmitters is more comprehensive than amateur types as a general rule. Some of that may be hard to get now. I'm going to have to try to find some of the literature. Remember: All electronics works by smoke. If the smoke gets out, it won't work... :-) Thanks much Len - I'm digesting the info now. I know it seems a little strange to become interested in tube equipment at this late stage, butour hobbies sometimes take us in strange directions. 8^) - 73 de Mike KB3EIA - |
Tube equipment question
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Tube equipment question
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Tube equipment question
"Mike Coslo" wrote in message
6 wrote: If the only antennas we have are trapped verticals, tribanders or dipoles/inverted vees cut for the band to be used, we might get away with not having to use a tuner at all. Still there are likely to be frequencies significantly removed from the antenna's resonant frequency where one might need a tuner to enable the transmitter to make full power. We aren't likely to need a wide range tuner for those times. A simple T-match will likely enable us to find a combination of settings which will present a low VSWR to the transmitter. The main alternative is to have a variety of antennas which present a VSWR of under 2:1 to a transmitter. That brings up a related issue. Lots of Hams today are restricted to one antenna, yet they would like all band operation. I think it would be a great idea for a manufacturer to have a transciever that included a tuner right in the rig itself. - 73 de Mike KB3EIA - They do exist, although being primarily interested in VHF/UHF operation (we only recently had the morse requirement for HF dropped over here in the UK, but that's another topic..!!) I've had little experience of them. I do remember vividly using a Drake commercial HF transceiver (I think it came out of a ship's radio room) back in the late 80's at a special event station that had this feature, you could operate on any band without any form of tuning at all, although of course how much power would get out on a really bad antenna is debatable ;-) Of course if you've enough money, there are those antennas that tune themselves. A friend has a 3-element beam that is computer controlled; as you tune across the bands, the elements automatically adjust themselves to the correct length..! I don't recall the make/model, but it is of American origin, does anyone know of it..? 73 Ivor G6URP |
Tube equipment question
"Ivor Jones" wrote in message ... "Mike Coslo" wrote in message 6 wrote: [snip] That brings up a related issue. Lots of Hams today are restricted to one antenna, yet they would like all band operation. I think it would be a great idea for a manufacturer to have a transciever that included a tuner right in the rig itself. - 73 de Mike KB3EIA - They do exist, although being primarily interested in VHF/UHF operation (we only recently had the morse requirement for HF dropped over here in the UK, but that's another topic..!!) I've had little experience of them. My main HF rig and my husband's main HF rig both have built in tuners. Both work pretty well. However they do not have the range of outboard tuners. I do remember vividly using a Drake commercial HF transceiver (I think it came out of a ship's radio room) back in the late 80's at a special event station that had this feature, you could operate on any band without any form of tuning at all, although of course how much power would get out on a really bad antenna is debatable ;-) A lot of commericial and military equipment have built in tuners with quite significant tuning ranges. Of course this comes at a price so amateur gear doesn't have as much range in their tuning capacity on the built in tuners. Of course if you've enough money, there are those antennas that tune themselves. A friend has a 3-element beam that is computer controlled; as you tune across the bands, the elements automatically adjust themselves to the correct length..! I don't recall the make/model, but it is of American origin, does anyone know of it..? 73 Ivor G6URP I think it is called the SteppIR. Too rich for my pocket book. Dee, N8UZE |
Tube equipment question
On Mar 4, 6:57�pm, Mike Coslo wrote:
wrote groups.com: Most hollow-state ham rigs can handle 2:1 SWR no problem. Sometimes there is less tolerance for loads that are highly reactive, though. What are the practical limitations of the Tube finals apparent flexibility? It's really a matter of how the rig was designed. Many 1950s hollow-state ham rigs were built with pi-networks that could match a wide variety of loads efficiently. The EF Johnson Viking 2 is a classic example of that type. Many homebrew designs also had such pi-networks. The problem is that the components for such a wide-range network tend to be large, heavy and expensive. So in the late 1950s and early 1960s, rigmakers designed more for compactness than for wide matching range. Still, the typical ham rig of those days could usually handle SWR of 2:1 or less with no problems. Is it safe to compare the load, plate, and drive controls to some of the functions of a tuner? (possible real dumb question) The short answer is "no". Tuning up a hollowstate ham rig is a similar but not identical to adjusting the typical tuner. Some may tell you that all it takes to tune up a tube transmitter is to "peak the grid and dip the plate", but that's simply not correct. Tuneup procedures vary according to rig design and you have to be specific. Of course once you get the hang of it, the procedure rapidly becomes second nature. I enjoy twiddling knobs, kind of the same way I like a manual transmission. 8^) It's a question of skill vs. automation. What specific hollowstate rigs are you considering? * * Last year at Dayton I purchased a 40 and 80 meter Heathkit single * * Bander as a learning tool - they are pretty simple. I restored the * * 80 meter unit, and will start on the 40 meter one sometime. I think you mean the Heath HW-12 and HW-22, or the later A models of the same rigs. They are from the early-to-mid 1960s, and have very limited matching range. They are really only meant to match a 50 ohm load. Note that there isn't even a LOADING control on them. The Single Banders were Heath's answer to the "SSB is too expensive" idea. Every possible simplification and economy measure was used in them, yet the result is a usable 100 W class SSB transceiver for one HF ham band. Note that the 75 meter one stops at 3.8 MHz. Heath figured that by simplifying the output pi network to the most extreme degree, they could save a few dollars. Coming up with a 50 ohm antenna was the ham's problem. I am now * * looking at a Kenwood TS-830S. It's a hybrid, with tube finals. I * * really like it so far, although I don't see it replacing my IC-761. That's a pretty good rig for its era. The matching range is limited but it will handle 2:1 SWR without problems IMLE. I am hooked on computer control of the newer rig - sometimes! Other * * times I just like that retro aspect. One of the great things about amateur radio today is that we can use a wide variety of technologies for the same or similar purposes. I find it ironic that the evolution of the "state of the art" has come full circle in about a half-century, at least in HF/MF: - Ham rigs of the 1950s usually had wide range pi-nets which required adjustment, but would match almost anything without an external device. - Ham rigs of the 1960s and 1970s usually had restricted-range pi-nets which were easier to adjust, but sometimes required an external matching device. - Ham rigs of the 1980s and later usually have solid-state finals and no adjustment - and usually require an external matching device. 73 de Jim, N2EY |
Tube equipment question
On Mar 4, 7:09?pm, Mike Coslo wrote:
. Lots of Hams today are restricted to one antenna, yet they would like all band operation. I think it would be a great idea for a manufacturer to have a transciever that included a tuner right in the rig itself. Many rigs offer that as an option. For example, the Elecraft K2 can be equipped with the optional KAT2 internal automatic antenna tuner. In my experience, the KAT2 can match at least a 10:1 SWR, if not more. It doesn't have manual adjustments, however - it's a form of autotuner. The 100 watt version of the K2 can be equipped with the matching external tuner. One interesting feature of these autotuners is that they automatically reduce power to a few watts while the tuning routine is operating. I don't know of any solidstate HF ham rig with a *manual* tuner built-in. 73 de Jim, N2EY |
Tube equipment question
On Mar 4, 3:56�pm, Mike Coslo wrote:
" wrote roups.com: * *Failure to properly * *neutralize a final RF amp can result in heating sufficient * *to melt the glass envelope enough to let air in and thus * *destroy the tube (an 833 that was mounted on the control * *console at Army station ADA for weeks as a reminder). * * * * I would also suspect that when dealing with 15 KW transmitters, errors would be pretty unforgiving. What are the practical limitations of the Tube finals apparent flexibility? * *That's in many decades of old literature and covered * *extensively. *Data from commercial service transmitters * *is more comprehensive than amateur types as a * *general rule. *Some of that may be hard to get now. * * * * I'm going to have to try to find some of the literature. Besides old ARRL Handbooks prior to the 1970s, I'd suggest finding the site that has digitized copies of GE Ham News. Those were (bi-monthly?) hand-outs by GE to push their tubes (naturally) but they contained lots of different ham projects (using tubes, of course). I found such a site a few years ago but didn't bookmark it. Was incomplete then but being worked on. The 1960s was a good peiod for new designs in USA amateur radio. I used to grab my boss' copies as soon as he was done with them back then. :-) 73, Len |
Tube equipment question
On Mar 4, 4:09�pm, Mike Coslo wrote:
wrote: * * * * That brings up a related issue. Lots of Hams today are restricted to one antenna, yet they would like all band operation. I think it would be a great idea for a manufacturer to have a transciever that included a tuner right in the rig itself. IF and only IF they appear on some modern-day surplus market, look carefully at an AN/PRC-104. That is a manpack HF radio with an extra box on the side for an automatic tuner for the whip antenna. It's been in military service (land forces) for about 20 years now and several companies are trying to get in with new replacements for it...Harris for one (if I remember the military news). Neat little thing, frequency-synthesized, SSB, can be keyed. Designed and manufactured by Hughes Aircraft Ground Systems. QRP of course but the military used the same R/T for higher-power vehicular and fixed HF sets (higher power antenna tuners, too, in those). All solid-state, of course. I have the TM on it in PDF in case you were really interested in that...:-) 73, Len |
Tube equipment question
"Dee Flint" wrote in
: My main HF rig and my husband's main HF rig both have built in tuners. Both work pretty well. However they do not have the range of outboard tuners. I should have noted large range and balanced/unbalanced output. My IC-761 has an autotuner on it that works pretty well with my vertical antenna. The dipole is run with balanced line, and needs a different tuner. A lot of commericial and military equipment have built in tuners with quite significant tuning ranges. Of course this comes at a price so amateur gear doesn't have as much range in their tuning capacity on the built in tuners. Size can be an issue too. The IC 761's tuner is a pretty tiny thing. I had to take an IC 765's autotuner 9 (very similar) apart once to repair it, and it was around the size of one of the mfj tiny tuners. A little bigger components, plus a 4:1 balun, and they would have it. - 73 de Mike KB3EIA - |
Tube equipment question
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Tube equipment question
" wrote in
oups.com: Besides old ARRL Handbooks prior to the 1970s, I'd suggest finding the site that has digitized copies of GE Ham News. Those were (bi-monthly?) hand-outs by GE to push their tubes (naturally) but they contained lots of different ham projects (using tubes, of course). Got it! Thanks a lot Len - I googled them up, and have enough reading material to keep me busy for a while. the site is: http://bama.sbc.edu/ge_ham_news.htm - 73 de Mike KB3EIA - |
Tube equipment question
On Mar 4, 11:21 pm, "
wrote: On Mar 4, 12:53?pm, wrote: On Mar 4, 12:48?pm, Mike Coslo wrote: Some may tell you that all it takes to tune up a tube transmitter is to "peak the grid and dip the plate", but that's simply not correct. Tuneup procedures vary according to rig design and you have to be specific. Sorry, but that was procedure for pre-WW2 high- power HF transmitters. Sure it was. While it is a simplistic phrase, it still applies. A more exact procedure was to tune up the exciter with reduced drive power and literally peak the grid current. Plate current was then observed with the plate tuning adjusted for a slight, but observable dip in plate current. Of (perhaps) greater importance was setting the neutralizing control for minimum grid current; "dipping" the plate current should produce the least grid current peak on adjusting the plate tuning. A number of amateur transmitters/transceivers have used a quick peaking of the drive/preselector control followed by adjustment of tune and load controls for maximum output, keeping readings within operating parameters. I've never seen an amateur transmitter with a front panel neutralizing capacitor. Neutralization is normally a set and forget procedure which one needn't worry about until the final tubes are replaced. Tuning for maximum output for a given amount of drive has become the norm in tuning high power, vacuum tube linear amplifiers. All one needs do is make certain that the bottles don't aren't drawing too much grid current. A check of linearity can be made with the station monitor 'scope. The load capacitor of a pi-net has the least effect on tuning to a new frequency. That would depend upon the antenna being used and the amount of frequency change as well as the type of equipment being used. Some manufacturers switch in some fixed capacitance on various bands or portions of bands. The pi-network output circuit was a favorite among amateur homebrewers for decades due to its simplicity and better ability to attenuate harmonics... ....but the Pi-L did a much better job of attenuating harmonics with only a little more circuit complexity. Quite a number of Novice licensees found themselves in receipt of OO notices or letters from the FCC when using a simple pi-net output tank with a multiband antenna. Dave K8MN |
Tube equipment question
On Mar 5, 3:26 am, Mike Coslo wrote:
wrote groups.com: The simplicity was what attracted me to them. No filters, nonotch, no pbt, no RIT, no - well you get it. Note that the 75 meter one stops at 3.8 MHz. Heath figured that by simplifying the output pi network to the most extreme degree, they could save a few dollars. Coming up with a 50 ohm antenna was the ham's problem. The 75 meter rig I have tunes to 4 MHz. It's also a HW22a, probably a later mod. But all that simplicity is a good thing for a lad raised mostly on integrated circuits! 8^) The 75m transceiver is the HW-12A. It runs 3.8-4.0 MHz. That's all the phone band there was back when the rig was produced. There's a mod in one of the mags--CQ, I think--that puts in a fixed silver mica cap with a little trimmer cap in parallel for making the thing work on both 3.8-4.0 and 3.7-3.9 MHz at the flip of a mini-toggle switch. That'd give you a bit more room to roam. I am now looking at a Kenwood TS-830S. It's a hybrid, with tube finals. I really like it so far, although I don't see it replacing my IC-761. That's a pretty good rig for its era. The matching range is limited but it will handle 2:1 SWR without problems IMLE. I have been pretty impressed so far. The receiver seems pretty hot, certainly the sound is *good*. I'm listening to it right now, and it is simply very legible. Tuning is only one speed, and a tad fast. Seems strange just having SSB and CW, but overall I think I'll keep it. In it's era, the TS-830 was somewhat of a DXer's and contester's dream machine. That receiver has an extra filter slot for cascading filters. One can still buy after market filters for it. Dave K8MN |
Tube equipment question
On Mar 4, 10:23�pm, Mike Coslo wrote:
* * * * I should have noted large range and balanced/unbalanced output. My IC-761 has an autotuner on it that works pretty well with my vertical antenna. The dipole is run with balanced line, and needs a different tuner. --- * * * * A little bigger components, plus a 4:1 balun, and they would have it. Well, sort of. The Ancient Ones used antenna matching devices to feed balanced lines. The Johnson Matchboxes are one example of a commercial version. Most Handbooks have examples of link-coupled balanced wide-range tuners. The problem was that such link-coupled tuners are large and not easy to bandswitch. About 1970, a new idea in tuners appeared: Use an unbalanced matching network such as a T or L network with a roller inductor or tapped inductor, with a balun if balanced output was wanted. 4:1 iron-core toroid baluns were compact and broadband, the T or L tuner could be made wide-range without complex bandswitching, and the whole works seemed an improvement on the old link-coupled balanced tuner. The problem was that baluns aren't magic devices. The system works well if the shack-end of the transmission line is around 200 ohms impedance and not too reactive. But in many cases the shack-end impedance with balanced line is very high or very low, and/or very reactive. Under such conditions the balun may not do a very good job because it is being asked to work far outside its design parameters. Also, if the shack-end impedance is low (say, 12 ohms), the use of a 4:1 balun will make it so low (3 ohms) that it may be outside the efficient matching range of the T or L network. These conditions may be partially remedied by use of a balun that can be switched to either 4:1 or 1:1 ratio, and by choosing antenna and feedline combinations that don't result in extreme values of shack-end impedance/reactance. But that reduces the flexibility of the system. The "unbalanced tuner followed by a balun" idea is clearly one where "newer" wasn't necessarily "better" in all cases. Yet it became very popular because it usually worked. But in many cases the balanced line was actually doing a lot of radiating and there was considerable loss in the system. Back in 1990, AG6K came up with an answer to the shortcomings of that method. He put a 1:1 balun between the rig and a simple balanced tuner, so the balun only has to deal with a pure 50 ohm load once the tuner is adjusted. Although AG6K favors baluns made from coax wound on PVC pipe, other forms of balun such as ferrite-bead and wound-toroid can be used if preferred. You can read AG6K's article he http://www.somis.org/bbat.html and judge for yourself. AG6K's approach used two ganged roller inductors and a single variable capacitor, compared to most commercial manual tuners that use two variable caps and a single variable inductor. Because there are only two controls, remoting the tuner is made easier. 73 de Jim, N2EY |
Tube equipment question
Mike Coslo wrote:
A little bigger components, plus a 4:1 balun, and they would have it. I wish that the manufacturers would include the provision for balanced feedline. The random-length dipole, fed with balanced line, is an ideal antenna in many cases. It's especially appropriate for disaster situations (and simulated disasters, like Field Day). Find the two highest supports that are available, as far apart as possible, measure the distance, cut the wire and install the middle insulator and feedline, hoist each end, and you're done. Now you've got a reasonably efficient radiator (especially if there's enough distance between those two supports) that you can use on any band, and the length of the feedline isn't particularly critical. But it takes a tuner and balun to make it work, and if this was included in the rig and was automatic, it would be ideal. 73, Steve KB9X |
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Tube equipment question
From: Mike Coslo on Sun 4 Mar 2007 22:56
" wrote: Besides old ARRL Handbooks prior to the 1970s, I'd suggest finding the site that has digitized copies of GE Ham News. Those were (bi-monthly?) hand-outs by GE to push their tubes (naturally) but they contained lots of different ham projects (using tubes, of course). Got it! Thanks a lot Len - I googled them up, and have enough reading material to keep me busy for a while. the site is: http://bama.sbc.edu/ge_ham_news.htm Thanks for the reminder on BAMA contents. BAMA has more than just old tube equipment manuals. :-) Good site! On the general subject of tube PA matching to load, some remarks: The automatic antenna tuner might have its beginning at Collins Radio of the 1950s decade. Reference is the T-195 transmitter, part of a set that used the special version of the R-390 series called the R-392, designed and built for the USMC, first fielded in 1955, intended to be Jeep mounted. The basic whip antenna matching was a servoed single variable L and a single variable C to a conventional PA output tank...so-called Ell-network, switchable to the four possible L-C connection possibilities. On an Army demo in late 1955, I was most impressed when the demonstrating officer simply removed half of a whip section (!), hit the tune function, and the servo system re-tuned to this new antenna impedance in seconds. :-) Warren Bruene must have had a hand in that Autotune labeled antenna matcher because it has the first instance I've seen for the "Bruene detector" in the transmission line to get both amplitude and phase of the RF. Slight variations of that exist today, generally with a toroid for current output and a small capacitor for voltage output, both combined into dual diode detectors. Today's antenna auto-tuning subsystems use binary-progression switched single inductors and single capacitors with the servo system basically a microcontroller plus small frequency counter (sometimes) that can determine which L or C to switch and remember the frequency and setting. SGC (Stoner Goral Company) in the Puget Sound area of Washington state has at least three models for both maritime and amateur radio HF use. The Big3 (Icom, Yaesu, Kenwood) have them, either built-in or as out- board boxes. Several independent USA companies have them. ALL (no exceptions) antenna tuners have limits on their impedance matching capabilities, whether "Pi-L" output tanks or big boatanchor style structures that look very impressive. There are few overall advantages in any configuration with the possible exception of Simplicity of the single L, single C variety now common to today's autotuning matchers. ALL, even the popular Pi-network, have limits that can be proven mathematically; if the math doesn't fit, no amount of publicity or historical references will make it fit better. If you or anyone else would like an algebraic-only math explanation of the four combinations of single L and C matching combinations...with their limits of load impedance variation, I'll be happy to forward them by e-mail attachments. No binary files here and the equations, figures are better shown in the PDF format. 73, |
Tube equipment question
On Mar 4, 10:56 pm, Mike Coslo wrote:
the site is:http://bama.sbc.edu/ge_ham_news.htm Mike, If you like the BoatAnchor Manual Archive, you may be interested in these sites. Lots of downloadable manuals and data: First is Pete Millett's book site: http://www.pmillett.com/tecnical_books_online.htm Has some incredible stuff, like complete ARRL and Radio Handbooks, Radiotron Designer's Handbook, Reference Data for Radio Engineers, and much more. All in PDF. CAUTION! Some files are quite large, and will take a long time to download via dialup. One trick I have used is to set up a dialup download late at night, hit the button and go to bed. and tube data, from the RCA HB-3 books: http://www.pmillett.com/hb-3_tube_manual.htm arranged by inidvidual tube type, for easy download. The Glowbugs website has lots of downloadable info: http://www.mines.uidaho.edu/~glowbugs/index.html including some good manuals and articles on WW2 military surplus: http://www.mines.uidaho.edu/~glowbug...__Surplus.html http://www.mines.uidaho.edu/~glowbugs/PDF%20files/ Some of these are quite large, too. "Bunker of Doom" site with lots of stuff: http://www.bunkerofdoom.com/ Tube manuals, for example. Transformer catalogs and other data: http://www.bunkerofdoom.com/xfm/index.html Another good site: http://www.antiqueradioarchives.com/archives_index.htm 73 de Jim, N2EY |
Tube equipment question
On Mar 5, 3:20 pm, Michael Coslo wrote:
wrote: On Mar 5, 3:26 am, Mike Coslo wrote: The 75m transceiver is the HW-12A. It runs 3.8-4.0 MHz. That's all the phone band there was back when the rig was produced. Thanks for the correction Dave. I should have looked at the back of the unit when I was composing my email Not a problem. I'm fairly familiar with the series since I ran them mobile for a number of years. There's a mod in one of the mags--CQ, I think--that puts in a fixed silver mica cap with a little trimmer cap in parallel for making the thing work on both 3.8-4.0 and 3.7-3.9 MHz at the flip of a mini-toggle switch. That'd give you a bit more room to roam. Now there is serendipity for ya! I was trying to align the thing, and having some trouble with the top end. And the unit had this extra switch on the front. Since I couldn't find the schematic for the "a" version, I wasn't sure if that switch was part of th ea version or not. Preliminary looks made me think that it might have been something to lower the frequency down to the CW portion of the band. But it looks as if my rig has that mod . If I run across the mod, I'll forward a scan of the information to you. There was another easy mod which padded the carrier oscillator frequency in order to roll off some of the annoying high frequency hiss on receiver, while adding fullness to the transmitted audio. It had the added benefit of more carrier output for tune up. Your HW-12A may have that mod as well. In it's era, the TS-830 was somewhat of a DXer's and contester's dream machine. That receiver has an extra filter slot for cascading filters. One can still buy after market filters for it. I can believe that it was very popular. The hybrid concept is interesting. I especially like that you can turn the tubes off if you just want to listen. The '830 doesn't get points for being an early hybrid, but it does get points for having that cascaded filter availability. The early Hybrids were rigs like the Yaesu FT-101 and variants along with the Kenwood TS-520 and TS-820. Drake used a hybrid design in the T4-XC/R4- C transmitter/receiver pair but there was a mix of tubes/solid state devices in the receiver. The Drake 2-C receiver might have been the earliest hybrid design amateur receiver. Dave K8MN |
Tube equipment question
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Tube equipment question
On Mar 6, 4:30?pm, Michael Coslo wrote:
wrote: You can read AG6K's article he http://www.somis.org/bbat.html and judge for yourself. I have gathered the parts to make just that!. I'd have it up now, but I switched to a coax fed antenna for a while, and built a more traditional tuner. In the interim I went back to balanced line. The AG6K tuner can be used with balanced or unbalanced line. All you have to do to use it with an unbalanced line is to ground the coax shield at the tuner end of the coax balun, and use the "other side" to feed the ungrounded line. A simple SPST switch of adequate ratings can do the job. The AG6K tuner, as described, has adequate matching range for most dipole-fed-with-balanced-line amateur antennas. A little care in choosing the antenna and feedline length can make the tuner's job a lot easier. Reg Edwards' DIPOLE3 program can be a big help in figuring out the shack-end impedance of various antenna/transmission line combinations. AG6K's approach used two ganged roller inductors and a single variable capacitor, compared to most commercial manual tuners that use two variable caps and a single variable inductor. Because there are only two controls, remoting the tuner is made easier. Some day I'll report on how mine is doing. In the present situation I don't need remote tuning, but will probably motorize the unit anyway. Although not mentioned in the article, the roller inductors could be replaced by a pair of tapped coils and a double-pole switch. The tap positions would have to be found by experiment, but could be made permanent once they were found. Tuner adjustment could then consist of simply selecting the correct tap postion with the switch, and adjusting the variable capacitor for minimum SWR. Automatic tuners are not new to amateur radio, btw. An automatic balanced tuner was described in QST for July, 1952. It would automatically retune itself within an amateur band. Changing bands meant changing coils, but once that was done the tuner would do the rest automatically. 73 de Jim, N2EY |
Tube equipment question
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Tube equipment question
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Tube equipment question
On Mar 7, 12:01�pm, Michael Coslo wrote:
wrote: On Mar 6, 4:30?pm, Michael Coslo wrote: I have gathered the parts to make just that!. I'd have it up now, but I switched to a coax fed antenna for a while, and built a more traditional tuner. In the interim I went back to balanced line. The AG6K tuner can be used with balanced or unbalanced line. I should have been more clear about the reasons. The tuner that I made is a massively retro unit that is kinda pretty. Cherry finished wood face, with real old time knobs and cranks. If I went to the balanced one now, I'd need to start over again. I will eventually build the AG6K type balanced tuner of course, but want to enjoy this one for a while. Understood. Reg Edwards' DIPOLE3 program can be a big help in figuring out the shack-end impedance of various antenna/transmission line combinations. * * * * I have all his programs. Me too. In several places! Upon his demise, his family and a number of interested amateurs made sure to archive and distribute them. We miss Reg over on rraa. I miss him too. I read his bio somewhere - very impressive. A real class act. Although not mentioned in the article, the roller inductors could be replaced by a pair of tapped coils and a double-pole switch. * * * * The tuner can be hot switched, I assume? Depends on the switch, but I would not do that even with heavy-duty switches. Puts an unnecessary strain on the rig feeding the tuner. Automatic tuners are not new to amateur radio, btw. An automatic balanced tuner was described in QST for July, 1952. It would automatically retune itself within an amateur band. Changing bands meant changing coils, but once that was done the tuner would do the rest automatically. To be really accurate, such a tuner might best be called "semi automatic". You had to manually set it up for each band - it couldn't usually find a match by blind luck. But once you had the coil and taps set, it would find a match and follow you up and down the band. Although the original used a balanced link-coupled tuner, the principles could be applied to any tuner that meets the basic concepts. One modern-day use I can see for such a tuner is for 80/75 meters with, say, a dipole. You could QSY anywhere in the band and the tuner would automatically follow. * * * * Thanks for the reference, Jim. It should be interesting to see how they did it then. I looked up the articles. Here's how they did it: The key to the system is the in-line phase detector. It looks a lot like the sensing element of an SWR bridge, but what it senses is the power factor (reactance ratio) of the load. The phase detector has two DC outputs. If the load is resistive, the two outputs are equal. If the load is inductive, one output is higher than the other, and if the load is capacitive the other output is higher. The DC outputs are fed into a sort of DC differential amplifier (couple of 6SN7s) which operate a pair of relays. The relays control a reversible 2 rpm motor that turns the big splitstator capacitor in the tuner. If the two outputs are equal, neither relay energizes and the motor doesn't run. If the load is capacitive, one relay energizes and turns the motor one way, and if the load is inductive the other relay energizes and turns the motor the other way. No operator attention was needed at all once the system was set up. You didn't have to push a "TUNE" button or anything else - the tuner would simply do its thing when you transmitted. In a later article, the same idea was applied to a mobile installation, retuning the antenna loading coil automatically. This was long before "screwdriver" antennas! The whole thing is so simple that at first I wondered why it wasn't more common back then. The answer is that most rigs of that era had lots of adjustments, and automating one of them didn't really save all that much in most cases. Today, with no- tune rigs, maybe it's worth another look. 73 de Jim, N2EY |
Tube equipment question
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Tube equipment question
On Mar 7, 9:17�pm, Cecil Moore wrote:
wrote: The whole thing is so simple that at first I wondered why it wasn't more common back then. Ever watch an ART-13 tune itself? -- 73, Cecil *http://www.w5dxp.com Heh, I have, about 20 years after it first came out. That, and I used to align R-391s...which were much more fun to watch. ADA had one commercial Collins Autotune transmitter for about two years, three racks wide, all the Autotune rotary power came from a single quarter-horsepower reversible motor. Fastest-reversing motor I'd seen up to 1953. 73, Len AF6AY |
Tube equipment question
On Mar 8, 12:17?am, Cecil Moore wrote:
wrote: The whole thing is so simple that at first I wondered why it wasn't more common back then. Ever watch an ART-13 tune itself? Yep, Cecil, quite a show! But the Collins Autotune is really a form of mechanical memory re-tuning, like the mechanical pushbuttons on an old-style car radio. A human operator tunes up the ART-13 manually, locks the settings into one of the Autotune 'memories' then the Autotune remembers the exact settings of each control and resets them, when requested. What the Autotune does not do is to adjust any of the controls to some electrical parameter in the rig itself - plate current, low SWR, resonance, etc. It just puts all the knobs back where they were. Still very impressive, though. And about a decade before the articles I mentioned. 73 de Jim, N2EY |
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