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  1. #271
    Senior Member Hidyn's Avatar
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    Is a reflected power meter an SWR meter? I have an external one I bought at a ham flea market. I went there for an antenna and picked up random stuff from random people just for the sake of visiting and browsing. Is it half decent? I wouldn't have a clue.

    I'll need a dummy load for sure, I heard you can DIY those fairly easily, right?

    I've heard about variacs, I think for controlling AC motors or something. Do you have any info on using one to power up the radio? I do suspect that it's been out of service awhile.
    "You can break the surgical procedure of removing an appendix down into about 30-35 individual steps each of which is not overly complicated or beyond an enthusiastic amateur."

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  2. #272
    Senior Member Doug_M's Avatar
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    Yes, reflected power is measured on an SWR meter. It is about checking the impedance matching (or mismatching). Your antenna and the feed line to it from your radio will impede the flow of energy coming out of your radio when you transmit. You want to have the best match possible (low impedance) to ensure you are getting the most RF energy transmitted and also so as not to cause damage to your transmitter.

    I've never built a dummy load but it shouldn't be too difficult. Paint can, oil, connector and probably a coil. I'm sure you could find plans on the net.

    Variac is a brand I believe but the device allows you to slowing increase the voltage. People talk about using them with old radios but I suspect most do not, simply because variacs are hard to find and expensive when you do. The big issue is capacitors. They don't last forever. Most older radios at some point need to have several capacitors replaced. A variac isn't going to prevent that eventuality, it will possibly simply postpone it on first power up.
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  4. #273
    Senior Member LB303's Avatar
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    My first DIY dummy load was good for 100W for a few seconds, and 10W indefinitely. Like Doug says, paint can, connector, resistor network. I used it dry, didn't want to deal with oil.
    Non-inductive resistors were always pricey, so like most hams on a budget, I went with a bunch of surplus ceramic wirewound ones that actually gave good performance (1.3:1 or better) up to 15m and 'good enough' (1.6:1) at 10m.

    Depends if you can source the parts, especially the power resistors cheap, this may actually be a better solution:
    https://www.amazon.com/Mfj-264-Dummy.../dp/B006OG7YUI
    $100 with the exchange rate seems not too outrageous. Good news is, ham radio gear is tariff-free from the US.

    And all I meant by 'half decent' was large enough to be readable. The point is to tune for a dip in the reflected reading, it's just easier when you can place a larger meter face in a convenient spot, rather than squinting at the mini meter that a transceiver will have.

    As with most of my old equipment, my variac was obtained thru a surplus store. It was a great tool for general experiments, including with vacuum tube apparatus. These days with the solid state rigs, there's a lot less need for it.
    Last edited by LB303; 10-15-2019 at 05:51 AM.
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  5. #274
    Senior Member Hidyn's Avatar
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    Well that SWR meter is definitely large and readable! I also have wire and oil for days, as well as a bag of SO-239 connectors.

    There's a couple of discussions online about using a variac to power up a radio, with a lot of opinions as to why and how. A lot of it is currently beyond me, but the instructions are fairly simple. I need to research reforming electrolytic capacitors.
    "You can break the surgical procedure of removing an appendix down into about 30-35 individual steps each of which is not overly complicated or beyond an enthusiastic amateur."

    -Survival and Austere Medicine, 3rd ed.

  6. #275
    The Gunsmithing Moderator blacksmithden's Avatar
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    You can pick up variacs on Amazon. They are nothing more than a variable voltage transformer. Old capacitors that havent had power on them for years tend to fail if you dump full voltage on them. By bringing the voltage up slowly, they can sometimes be saved.....conditioned if you will.....back into working order. You do this over a couple of hours, slowly increasing to output voltage. There are never any guarantees it'll work, but its worth a try.
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  7. #276
    Senior Member Hidyn's Avatar
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    I dunno guys. It almost sounds like re-capping is the better idea. The more I read about variacs and capacitors, the more it sounds like old capacitors just need replacing.

    It doesn't sound too terrible. Pop out the old, solder in the new. As long as you keep electrolytic ones installed properly, and use ones with appropriate voltage/capacitance/watt ratings, it should be fine.

    Of course I've only just started reading the manual online.

    Let's say I plug it in and turn it on. Am I only risking capacitors and tubes?

    Come to think of it, Doug is right. This sounds like it'll be cute and fun and all, and I'll definitely mess with it for the entertainment value, but I need to buy a modern reciever.

    Knowing how to use a ferrocerium rod is good. Doesn't mean you shouldn't have a bic in your pocket!
    "You can break the surgical procedure of removing an appendix down into about 30-35 individual steps each of which is not overly complicated or beyond an enthusiastic amateur."

    -Survival and Austere Medicine, 3rd ed.

  8. #277
    Senior Member LB303's Avatar
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    If it was point to point wiring like in my old HW-101 then I'd say all you are risking is the components.
    However that generation of radios from about 1970 onward went to a modular pcb style. A capacitor can fail one of two ways, short or open. If a capacitor fails open, which is more common, then you'll either have a failure to pass signal, or you'll notice a lot of ripple or distortion on the signal you do get. If a capacitor fails short, there's the possibility of a surge current that can vapourize the thin copper traces right off a pcb. Then you're into circuit reconstruction at a higher level.

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  10. #278
    Senior Member Doug_M's Avatar
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    I collect (well I don't any more) old computers from the late 70's/early 80's and never bothered with a variac and have never had a capacitor blow. I had one HF radio (FT-101) that is the same era as your 520 and it came with blown capacitors that did not damage the circuit board. What I'm saying is you'll be rolling the dice if you simply turn it on, but you'll probably be fine. Replacing capacitors is a common thing to do with all electronics from the 90s and older. You read about people doing it for old video game consoles, computers, radios, hi-fi gear, whatever. A worthwhile endeavour. It is one of those things that is relatively easy, but can be time consuming. That 520 is a model of radio worth preserving.
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  12. #279
    Senior Member Hidyn's Avatar
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    Well it turns out that it's a TS-820, so I wasn't terribly far off! I still don't physically have it, so I can't take pictures just yet.

    I downloaded the proper manual, as well as the service manual.

    I'll take good care of it! If the 520 is worth preserving, so is the 820!
    "You can break the surgical procedure of removing an appendix down into about 30-35 individual steps each of which is not overly complicated or beyond an enthusiastic amateur."

    -Survival and Austere Medicine, 3rd ed.

  13. #280
    Senior Member Doug_M's Avatar
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    Another fantastic radio! Still a solid state (rx) / tube (tx) hybrid so all the above thread applies. Wow, I'm jealous.
    Dictionary of the future:
    Global Warming was a popular computer simulation game,
    where the only way to win was not to play.

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