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Thread: drop in output power

  1. #1

    Default drop in output power

    Hello I'm Bob and I have a Ten-Tec 580 Delta, just yesterday 11th of feb' suddenly it's output dropped by 50% drawing only 9amps instead of the usual 18 amps from the psu. There was no symptoms to suggest this was about to happen so I was hoping some kind fellow radio ham might give me a clue as to what's going on with my rig. Thank you.
    Bob. GM0LQY.

  2. #2


    Your finals are bad.

    Check the coax and antenna with a antenna analyzer, see if you have a problem with your transmit antenna / coax first.

    Did you check it in CW mode - using a true 50 ohm dummy load?

  3. #3

    Default drop in output power

    Hello Sixmeter, many thanks for your advice, unfortunately I don't have an antenna analyzer however there is an atu in line and the problem is still there when hooked up to the dummy load. Thanks again for your help.
    Bob. GM0LQY.

  4. #4


    ATU = Antenna Tuning Unit, most ATU's won't tune over much of a range , maybe 4:1 or 6:1...

    Instead of insisting that the radio accept the antenna, make the antenna resonant and then you won't even need a ATU.

    It sounds like you need to find yourself an Elmer, since after all - this is physic's and you don't seem to comprehend, regardless if you are using a 3 watt AM Citizens band radio or a 1000 watt SSB transmitter, the physic's part is still the same.

    If you want to play radio, you need to invest in a certain amount of equipment, you can't just rely on instinct - like CB, where if it is wrong, all it does is burns out the finals. You hooked the dummy load up where? The end of your coax? - then you have a coax problem.

    If you hooked it up to the transceiver and it won't tune, then you probably burned out the ATU or the jumper cable is bad - shorted out or not bonded properly to the PL connector. Don't laugh, I had brand new ones that were bad. Went on a DXpedition and thought I had a antenna problem, when all it was - was the coax jumper... We lost our 6m station because of that one cheap jumper.

  5. #5


    when hooking up to a dummy load,the ATU is not necessary.
    To verify that the problem is with the radio, get a known good short coax jumper and hook directly to the dummy load.
    If you still have the issue, it is the radio... if not, maybe the radio was reducing power to protect itself, I can not say because I am not familiar with that radio and do not know if it has that capability or not. Your stating that it dropped to 50% power made me think that self protection was a possibility, I am not certain you would actually get 50% power out if the finals were blown...finding an elmer in your area would be a good idea. Good luck.

  6. #6


    The first thing I would do is rule out the power supply. Linear-style power supplies typically use pass transistors and if some of them fail, the supply can seem normal except for reduced output.


  7. #7


    good point Ben, none of our comments even addressed that possibility.

  8. #8

    Default Drop in output power.

    Hello guys, many thanks for your kind comments and advice. I did connect the rig straight to a dummy load with a good patch lead and the power loss is still there. Also connected the rig via only a swr meter to my g5rv which is resonant at 14.250 mhz but still the same result. I tested the PSU and its output is 100% so assuming the rig is seeing the correct impedance there must be a faulty board component but the manual i have is a bit short in fault finding and remedies so it looks like an expensive holiday for the old fellow. I'am wary of running the rig in its present state in case it results in more damage. Also sixmeters I don't instinctively mess around with stuff I don't know about is why i joined Ham Forum. I am not a radio engineer but having passed my RAE with two credits followed by a 100% cw test in 88. I consider myself a bit more advanced than a cb'er but I know you meant well so thank you for your input. many thanks again kind Hams all your comments and advice has been greatly appreciated. Best 73!
    Bob. GM0LQY.

  9. #9


    You're welcome.

    The damage done to your transceiver, is already done..

    Here is a short story for you - I bought a brand new Kenwood TS 590s in the fall of 2011 after listening to the whining / complaining of the local club members - at a field days site.
    Each expert operator had their own opinion on what was good and what their transceiver was - in their opinion.
    No one wanted to let others operate their station.
    I said screw it and bought my own HF radio.
    First year, life was good. I made lot's of contacts and I operated about 16 hours of the contest with no issues.
    Second year, the club decided to save a couple of bucks and they bought one of those cheap Harbor Freight gasoline generators.
    Without knowing that they had changed generators, I was all fat, dumb, happy, hooked up my radio, power supply, ground, computer and when I went to connect the printer cable to the sound card in the radio, there was a bright flash.
    The floating ground in the non - true AC power generator crashed my 85 amp - 12v power supply.
    The radio / computer died and I was very upset.
    After about 5 minutes, when the generator stabilized, the circuit breaker inside of the commercial power supply reset, the power supply came on, the computer came on.
    The radio only shows about 50 watts average, about 65 watts when I push it with the compressor.

    It's been that way now for 4 years, Kenwood wants $300+ to fix it, and I can buy a used radio for about $900.00
    My philosophy is - as long as it still works, and it isn't costing me anything, why fix it?

    NO - there is no user serviceable parts inside of a modern HF transceiver. Even the days of a regular Joe - buying a certain board, putting it in themselves, is pretty much over.
    What we have to look at is - why did it blow? If you don't fix the problem - it will reappear on the new board, sometimes quicker then the first time.

    I don't know what it is with those damn G5RV antennas, the SOB that invented it should have been shot.
    I personally believe that Lou Varney went to his grave - wishing that he never invented it.
    Yes it is resonant - a little - on 20 meters.
    Your problem was trying to tune it to other bands.

    I don't throw insults to hurt peoples feelings, I give advice to make people look - harder - at the problem, and make them prove to me that I am wrong.
    The way the G5RV worked was that it was used, along with a Johnson Matchbox tuner, into a tube type radio, which had an adjustable PI network that did not care if the load was truely 5o ohms, all it cared about was that you could tune the final tank circuit so the maximum amount of power could be applied, with the minimum amount of deflection.
    A Thermionic Valve - Vacuum Radio Tube - is very forgiving. High Power Transistors are not! PERIOD!

    Take that G5RV and give it away, throw it away, get rid of it....
    I have two / used / MFJ 949 antenna tuners, each was burned up with - You Guessed It - a G5RV.
    Some fool trying to tune up on 10 or 40 meters.. In quick fashion it got hot or arced over and boom - instant paper weight!

    I'm surprised that your neighbors didn't hang you with it, I received X amount of complaints - in the first three days - from neighbors that said that their computer router crashed and it was causing interference to their home electronics.
    Yes - I bought one of the fool things, thinking that the advice given to me was a bunch of bull... Boy was I wrong!
    The only thing the G5RV is good for - is if I wanted to use the Copper Clad wire to make a resonant dipole. Throw the ladder line away. Get a balun, use coax.

    I did about 20 hours of research on the 20m - G5RV and Lou Varney.
    Did you know that he recommended using 65 feet of RG8U ( 66 velocity factor) coax - after the ladder line, as a matching network?
    I've seen all kinds of Kamikaze type things done - including running it straight thru the window - directly into the MFJ 949 tuner...


  10. #10


    Yaesu FT101ZD + Daiwa CN419 manual ATU, then Kenwood TS-930S-AT, with built in auto ATU.

    Add 1 x 1/2 size G5RV, fed with around 30 feet of RG58 to the PL239 at the bottom of the ladder. Result? No issues, no burnt out radios, no need to tune at all on 20m, and either ATU coped happily on 10, 15, 20m. Much DX done with no problems. I will put one up again just as soon as my son moves out in the summer and I get my shack back. And yes, I've also gone the dipole, balu, co-ax route, but it didn't fare any better than the G5RV, so I'm sticking with it.

    You probably won't accept this as 'proving you wrong', 6m, but I can only offer my personal experiences as evidence that the G5RV CAN work very nicely indeed.
    Current radios: VHF/UHF: 2 x Baofeng 2/70 Handhelds. VHF: Kenwood TR9130 2m multimode. HF: Kenwood TS930S-AT
    Home antennas planned: G5RV / G7FEK / end fed wire. 1/2 wave vertical for 10m. 6 element beam for 2m. Vertical collinear for 2/70
    Website for the 'day job':

  11. #11


    Louis Varney was a clever fella - He was an officer in the Royal Signals during WW2 and specialised in antennas for direction finding and interception. He came from Essex (Colchester or Chelmsford, I think) and did a talk at the Lowestoft Radio club back in the 80s when I was first licensed. He spent a lot of time talking with the old boys who all seemed to have been doing things with radio in the war - very much a closed shop radio was back then! They ALL had G5RVs in the gardens, because people thought they were washing lines. Hams kept very quiet back then because they interfered with TV so much. You had to be brave to advertise what you did as a hobby.

  12. #12
    Super Moderator 5B4AJB's Avatar
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    Mar 2008
    Meneou, Cyprus


    I met Lou at the Kempton Park rally once, he said the famous G5RV antenna was a "compromise".

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