Finally got the AH-4 working properly

Discussion in 'Mobile Radio Systems' started by HB9FUH, Jan 7, 2016.

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  1. HB9FUH

    HB9FUH Ham Member QRZ Page

    You might recall a couple of months I was having problems with very high SWR on my IC-7000, running through an AH-4 tuner to a whip. Today I eventually got the time to pull apart the rear of the vehicle in order to look at the tuner.

    There didn't appear to be any obvious damage, relays were definitely firing when I hit the "Tune" button, but still very high SWR on anything below 28MHz. Eventually out of desperation I removed the jumper on J5 and put it on J6 (according to the technical manual, that's what you do for testing). Powered it up, then put the jumper back in the right position, and suddenly it worked again! I could tel straight away, as receive volume increased massively. Made two QSOs to Minsk and Greece, both reported 59.

    So, all good in the end :)
     
  2. HB9FUH

    HB9FUH Ham Member QRZ Page

    The problem started again, took a look at the wire linking the AH-4 to the whip, seems it was arcing to the body. Replaced it with some military antenna wire, and re-routed it into the centre of the grommet (it was on the side, so quite close to the metal), hopefully that will survive a little longer.
     
  3. K0BG

    K0BG Ham Member QRZ Page

    That is why I originally referred you to my web site. The output voltage can get over 10kV, or as much as 10 amps, depending on what the impedance is.
     
  4. HB9FUH

    HB9FUH Ham Member QRZ Page

    Yes, I knew that. I was just surprised that the insulation on my wire had broken down.
     
  5. KF5FEI

    KF5FEI Ham Member QRZ Page

    Maybe a hunk of Packard 440 would be the fix? Hit a neon sign shop and see if they'll give you some scraps.
     
  6. HB9FUH

    HB9FUH Ham Member QRZ Page

    Thanks, I'll see if the replacement works first.
     
  7. KK4YDR

    KK4YDR XML Subscriber QRZ Page

    You need to apply a little Copedeance grease to lower your SWR.
     
  8. WA4SIX

    WA4SIX Ham Member QRZ Page

    Good old fashioned non resistor/spiral wound spark plug wire or neon wire (As above) should work fine.
    For neon wire, any local sign shop will have many scraps, or sell it to you at about a buck a foot.
    Best option is to call a sign shop, ask for the owner, ask about the neon wire, then ask what beer or coffee they like. Show up with refreshment & have a source for life.

    Ed
     
    VK2CCR likes this.
  9. KH6AQ

    KH6AQ Ham Member QRZ Page

    The center conductor from solid dielectric RG-58 will work fine at 10 kV. For higher current ampacity the center conductor from solid dielectric RG-8 will do the job.
     
  10. WA4SIX

    WA4SIX Ham Member QRZ Page

    With the solid dielectric coaxes that I have seen, I would not want to use them in a mobile application, due to fatiguing the conductor.
     

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