FT 857 Power Failure when TX'ing on full power with extension cable.

Discussion in 'Mobile Radio' started by VK2MJM, Dec 20, 2014.

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  1. VK2MJM

    VK2MJM Ham Member QRZ Page

    I am find that my FT 857d loses power when transmitting on full power on HF while using the extension lead for the control head in the car. Does anyone know why that is and what to do about it?


  2. KV3D

    KV3D Ham Member QRZ Page

    It's possible that the power supply (whatever yours might be) isn't getting enough current to the radio. Just yesterday I had a similar problem with my IC-735. It would shut off when I TXed with 100 watts and the display would fade out at around 30 watts. Turns out that the necessary current was 20 amps, and my power supply only provided three!
  3. W1GUH

    W1GUH Ham Member QRZ Page

    Does it do this when you don't use the extension cable? It would be very
    strange if it behaved differently with or without the extension.

    The previous post is the most likely cause if you're using a PS and not a car battery.
  4. VK2MJM

    VK2MJM Ham Member QRZ Page

    Hi, Yes I've tried using full power with the short 10 cm lead, i.e. no extension lead, and there is no power failure. But with the extension lead it fails when TX'ing over anything over 50 Watts. I also had a brand new IC-7000 a few years ago. Got the extension lead and it did exactly the same thing. Not sure what it means, but as I am running off the car battery with a mobile installation, I have no other option at this point. Actually, it really shouldn't happen, because the radio is designed for mobile use.

    Any ideas?


  5. KD0SGX

    KD0SGX Ham Member QRZ Page

    How about the possible RF back into the rig? Since the length if the screen cable is longer more opportunity for this to happen. How's the Swr? Also you could try and inline coax choke to test about 24$ mfj makes one. Looks like a PVC pipe.

    Almost every time I have seen odd sissies like this it's been poor power or RF back into rig, for multiple reasons.


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