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

    I have a FL-2100B that the SWR is high between the exciter and amplifier on the higher bands in standby or off. 80 and 40 is ok but SWR rises on 20 15 and sky high on 10. Input SWR is less than 1.3 on all bands in operate. Is this inherent of this amplifier or is there a problem that I cannot locate? I checked the relay and input/output wiring and all seems as designed. I also tested this with the output connected to a 50 ohm dummy load. I also tried different jumpers to rule that out.

    Sean Davis

    REASTON QRZ Member

    Try cleaning the relay contacts. Or your antennas have swr problems.
  3. N8VIL

    N8VIL Ham Member QRZ Page

    Yes. The relay and associated wiring seem ok and as designed. Same result into dummy load also. I have a SWR meter between amp and load. SWR from amp into antenna and dummy load is good. Just the SWR between exciter and amp is high.

    Attached Files:

    Last edited: Jan 10, 2016

    REASTON QRZ Member

    When the amp is off or in standby, the relay connects the input coax connector to the output coax connector with a straight wire or coax. There is something wrong there (between input and output connector if you have a dummy load at the output but the radio reads a high swr instead a low swr from the dummy load through the wiring. There isn't much else there to consider except something really weird.
    Last edited: Jan 10, 2016
  5. N8VIL

    N8VIL Ham Member QRZ Page

    The circuit is pretty straight forward. I am just wondering if the wiring approach they used is causing the problem. Relay contacts have been cleaned and DC ohm test through both antenna connectors is good. Problem only noticeable on 20 (1.5) -- 15 (1.8) -- 10 (3.0+). 80 and 40 is 1.1. While in operation I have great input SWR. I am wondering what other users of the FL-2100B are experiencing to rule out a design flaw in the wiring. It could be something obvious and simple that I am just missing. I am an experienced tech but this has me baffled at the moment.
  6. KM5FL

    KM5FL Ham Member QRZ Page

    In all the FL-2100,B,F,Z models I've repaired, I've never encountered a "design flaw" exhibiting the symptoms you're experiencing, but that doesn't mean it isn't possible.. However, I believe either you haven't successfully cleaned the relay contacts (paying close attention to the N/C connections), or there is a poor/open solder connection on the jumper where it joins the input terminal to the output terminal on the relay..

  7. G3YRO

    G3YRO Ham Member QRZ Page

    I would say it IS a design flaw . . .

    Into a dummy load, my VSWR Bridge shows straight -through readings into the Linear of 1.3:1 on 20m, 1.5:1 on 15m, and 2:1 on 10m.

    As you will see, the actual non-coax wiring to and from the relay and connectors is rather long . . . I also I doubt if the pick-up line for the SWR Bridge is actually 50 ohm impedance (and it's quite long). So I presume that's what is causing it.

    At the end of the day, these Amplifiers were designed to be used with Valve PAs, where that kind of indicated VSWR wouldn't cause any problem.

    I bet if you try a longer length of coax between your rig and the amplifier you will see different readings.
  8. N8VIL

    N8VIL Ham Member QRZ Page

    I kind of suspected that to be the case. I did everything as far as connection issues and relay cleaning. My main reason for asking the question was to get feedback from other users of this amplifier and their experiences on feed through SWR. If I get ambitious enough, I may break the connection at the input of the SWR bridge and terminate the connection with a 50 resistor and check if that is the issue. I also thought the lead length and type may be causing problems at higher frequency. Other than that, the amplifier operates flawlessly with excellent output and input SWR.
  9. WA4SIX

    WA4SIX Ham Member QRZ Page

    I think that you will find the former suggestion of properly cleaning the NC (Normally Closed) contacts of the relay should help. I am not sure if you can install a "Wetting circuit".

  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Could well be poor choice of wiring internally.

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