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#1
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#2
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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 |
#3
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#4
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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 |
#5
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#6
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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 |
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