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Thread: Low power related to antenna mismatch?

  1. #1

    Default Low power related to antenna mismatch?

    I just installed a fan dipole AND just got my first rig, a Heath HW-101. The rig is not putting out much power, barely twitching the needle. I haven't yet put a SWR meter or antenna tuner on the dipole (waiting for both to get here), but my question is this: will a mismatch between transceiver and antenna cause rig to put out less power? I'm trying to troubleshoot whether the rig is at fault or it's just not happy with the antenna. (Previous owner of Heath says it was putting out 100W last week, so it's a real dilemma.). Thanks for any insights. KI5DQT

  2. #2

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    I am not real familiar with a Heathkit radio. My dad had one in the early 70s and that’s what got me interested in amateur radio but I have never purchased one yet. As for your question. A modern transceiver will definitely drop in power when the antenna is not matched properly. Radio at that age would most likely be extremely dangerous transmitting. I would think it would be easy to burn out the finals when the antenna is not matched properly. The quick answer to your question is yes I believe the power would be dramatically dropped if the antenna is not matched.

    Transmit on very low power with your tuner and SWR in line until you get it matched.



    Roger



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    73
    K5MOW

  3. #3

    Join Date
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    Without knowing the specifics of how you are going about this, are you certain you are loading the transmitter up properly? It seems to me with the two knobs in the upper left you should be able to peak and dip the finals to achieve max zap. Unless you are trying to tune up in an ssb mode...

    Try using a cw key (or just any old switch will do) to engage the transmitter and tune 'er up. If I'm not mistaken, that rig should be able to handle a bit of mismatch with ease by simply tuning the knobs. Perhaps you should scour the net for detailed tuning instructions for your rig so you are nearly guaranteed of getting it right the first time. Just my .02¢

  4. #4
    K7KBN's Avatar
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    Another piece of equipment that would be useful here is a dummy load. That would rule out the antenna and feedline.
    You DID get the operating manual for the 101, right? I built the HW-101 back in the 1970s. With its pi-network output, a separate "tuner" is often not required. I operated mine for a couple of years before I ever used an SWR indicator. My 20 and 15 meter dipoles each had over 2:1 - almost 3:1, but the transmitter was putting out full power CW with no strain.

    More modern rigs, especially the solid-state final-types, are much more finicky with loads they don't like. That's where the dummy load shines. Just a 50 ohm, non-inductive resistor or combination of resistors equaling about 45-55 ohms and sized to handle the transmitter power. Presents a near-textbook load for the typical "50 ohm" output of a typical ham transmitter.
    Last edited by K7KBN; Fri 15th Mar 2019 at 07:08.
    73
    Pat K7KBN
    Semper ubi sub ubi.

  5. #5

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    Quote Originally Posted by KI5DQT View Post
    I just installed a fan dipole AND just got my first rig, a Heath HW-101. The rig is not putting out much power, barely twitching the needle. I haven't yet put a SWR meter or antenna tuner on the dipole (waiting for both to get here), but my question is this: will a mismatch between transceiver and antenna cause rig to put out less power? I'm trying to troubleshoot whether the rig is at fault or it's just not happy with the antenna. (Previous owner of Heath says it was putting out 100W last week, so it's a real dilemma.). Thanks for any insights. KI5DQT
    You need to perform the initial tune up. See the "Transmitter Section" of page 140 in the manual.
    I don't think the rig cuts back on power in a mismatch situation, so keep your test transmissions short.

    Ben

  6. #6

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    What's reception like? Do you get a sharp peak in performance at the frequencies you think the antenna is resonant? Does the background noise shoot up at a certain frequency and then drop off again the other side - that will give you a clue if your antenna is actually working. If your antenna appears to function on the wanted bands, then I'd give it a shot - but if you need proof of matching, then wait for the VSWR meter and set your mind at ease - Me, I'd listen for somebody calling and respond to them and see what happens.

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