Yaesu FL-2100B SWR in standby

Discussion in 'Amateur Radio Amplifiers' started by N8VIL, Jan 10, 2016.

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  1. N8VIL

    N8VIL Ham Member QRZ Page

    The length of coax will only hide the impedance bump in the amplifier. I want to correct the impedance mismatch inside the amplifier so input coax length won't be an issue.
    The next thing I am going to check once I get it tweaked in is to measure the power into the amp and out of the amp to see what the loss is in standby.
    Last edited: Jan 18, 2016
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I suspect you will indeed find loss on the higher bands...probably not on 80m. Check it on 10m and I wouldn't be surprised if its a couple dB.
  3. G3YRO

    G3YRO Ham Member QRZ Page

    Of course !

    BUT . . . it is inconceivable that on each band there is a different VSWR on the coax INTO the Amp . . . . but on the coax OUT of the Amp it is always 1:1 . . . that simply can't be, when it is part of the same coax line.

    As I say, you have something silly going on here . . . and I don't think you'll be able to sort out the problem until you sort out this weird discrepancy.

    As I suggested before, the first thing to try would be different lengths of coax between each of the elements.
  4. W1QJ

    W1QJ Ham Member QRZ Page

    This is typical, most open frame relays like the ones in most amps with open frame types have a bit of inductive reactance. It shows up more as frequency increases. The cap cancels it and lowers the swr. Some relays are better than others and even vary among same ones. I haven't figured out just why same ones differ but as a system the coax to and from contribute to the overall picture. One could rewire it with new coax and try different dressing methods to see if it gets better without the cap. But if it turns out to be the relay totally then rewiring won't help.
  5. N8VIL

    N8VIL Ham Member QRZ Page

    Looking at the open wire to and from the relay, although I haven't tested it, I believe it to be a combination of both.

    On another note. I also tested my AL-80A just to get a comparison. The SWR is good in pass through but just a little higher (1.1 to 1) on 20-15-10 meters. I also checked pass through power and did note attenuation on 20-15-10 meters. Power values are within the resolution of my meters.

  6. W1QJ

    W1QJ Ham Member QRZ Page

    Lets face it, once you open a coaxial feed line and then insert ANYTHING in between there is always going to be some sort of impedance bump be it small or large depending on how well the break is reassembled once the line picks up and goes to the load. In your case you have an open frame relay and unfortunately the relay does not keep a 50 ohm impedance through it. What you do with the length of the coax on either side will make little difference because the problem is in the relay itself. This is why "coaxial" relays are made. They tend to keep a close 50 ohm impedance through them. So unless you get rid of that relay and switch it out for a coaxial type, the bump is always going to be there.
    WA7PRC likes this.
  7. NN2NN

    NN2NN Ham Member QRZ Page

    I just started to have an issue with what I believe to be with the relay in my FL2100B. I want to clean the contacts and just looking for some advice on how to do this. I have the bottom cover off and I see the relay, however, it seems to be a sealed unit. Any help would be appreciated.
  8. N8VIL

    N8VIL Ham Member QRZ Page

    I carefully removed the plastic cover by carefully prying on the sides to release it from the base of the relay. I cut about a 3/16 strip of paper from a business card. Lightly soaked the cardboard strip with contact cleaner and cleaned the relay contacts in both positions. Do not use a burnishing tool or anything abrasive. I believe the contacts are silver plated and you do not want to burn through the silver plating. The paper is abrasive enough to clean the contacts with the cleaner without damaging the contacts.

  9. NN2NN

    NN2NN Ham Member QRZ Page

    Hey Sean, thanks for the reply.

    Steve NN2NN
  10. VE3TMT

    VE3TMT XML Subscriber QRZ Page

    I replaced the relay in mine. Much quieter switching.

    Food for thought....


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