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RM Italy KL 503 HD power spike question

Discussion in 'CB and Export Equipment and Accessories' started by Wayfarer, Aug 2, 2021.

  1. Wayfarer

    Wayfarer Member

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    I just got a new KL 503 HD for use with my Lincoln II+. Seems to be working great. However, it is exhibiting some odd behavior. When I let off the key, it jumps up to full power for about a half a second before dropping back to zero. The spike goes up along with the step that the amp is set on. At 1 it spikes to 50W, at 2, 100W and so on all the way up to 6, 250W. This is on both AM and SSB settings.

    For example, with the Lincoln on USB/LSB with no modulation and no power output with the key down, the amp puts out zero watts, as it should. But as soon as I release the PTT, the amp shoots all the way up to max power (depending on where the amp is set 1-6), holds steady at max power for a half a second, then drops back to zero. At first I thought maybe I had my roger beep on accidentally, but it wasn't on.

    This is with a Daiwa power meter that I use on all my other radios and has never exhibited this behavior, so I believe the power readings are accurate. The spike is noticeable on both AM and SSB settings on the amp.



    I've never had an RM Italy amp before. Is this normal?
     
    #1 Wayfarer, Aug 2, 2021
    Last edited: Aug 2, 2021
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  2. loosecannon

    loosecannon Sr. Member

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    sounds to me like your mic button is connecting the TX before the RX is released.

    this is what's known as "make before break" as opposed to "break before make" which is what you'd want.

    mic switches work by applying ground to either the RX wire, or the TX wire depending on where the slide switch is.

    your mic sounds like it's applying ground to the RX side before releasing ground from the TX side.

    in D104's you would just bend the tabs a bit to make one disconnect before the other connected.

    in a mobile mic there's not much to be done besides trying to release the mic button a bit slower and see if that helps.
    LC
     
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  3. Wayfarer

    Wayfarer Member

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    Then there might not be anything I can do, the amp I guess is doing what it's supposed to do, and it may just be incompatible with my Lincoln II+ ... which is bone stock, by the way, including the mic. I have a Palomar 250 that works perfectly fine with the Lincoln II+, so I may just have to go back to it.

    Tomorrow I'll try some other radios with the KL 503 just to make sure it's an issue with the Lincoln and not the amp.

    Edit: I just tried several other radios, a Kenwood, a Galaxy, and a Flex, and the amp does NOT have any power spike when letting off the mic. So it does indeed appear to be an incompatibility with just my Lincoln II+. Not sure if this is a design flaw with the Lincoln, or something going on with my particular radio. FWIW, it's new as of a month ago and has not been modified.

    Too bad because I had been waiting a long time for the KL 503 HD to be back in stock - was looking for a nice power bump over my old reliable 30+ year old 125-ish watt Palomar. The RM Italy amp is very nice other than this power spike issue.
     
    #3 Wayfarer, Aug 2, 2021
    Last edited: Aug 2, 2021
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  4. NightThumper

    NightThumper Sr. Member

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    Is the Rodger beep turned on?
     
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  5. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Do you have a way to monitor the Lincoln II from another radio?

    When you have that "rise", it scares me to think that the Lincoln is delayed - you proved that by switching the amp to another radio and was not able to recreate the condition.

    So that means the Lincoln might need a little work - not sure what kind of work.

    Why a concern? That lag, if it's RF related but you can't hear it - it becomes an issue - not just for the amp - but if your Lincoln is not shutting down the TX correctly - like a lagging IF in the Mixer during switchover - that signal can easily kill ANY amp you use with it.
     
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  6. Wayfarer

    Wayfarer Member

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    There is no spike whatsoever from the Lincoln barefoot or when paired with my other amps. The only time there is this spike is when the Lincoln is paired with the KL 503. It does it whether it's in the mobile or in the shack. SWR is 1.1 into an MFJ dummy load, and everything is properly grounded, so no stray RF. It's only the Lincoln/KL503 combo that does it. Paired with any other radio/amp, both the radio and amp each perform flawlessly.

    I'm thinking there must be some particular incompatibility that somehow triggers a feedback loop in the Lincoln which the amp picks up for a half second and retransmits before shutting down. It's as if the roger beep is turned on but it's not a roger beep. From a second receiver the spike just sounds like hash.

    I think it's just one of life's great unsolved mysteries. Probably just going to go back to my old Palomar and "settle" for 125 watts out.
     
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  7. Handy Andy

    Handy Andy Do Your Research First, Then Decide...

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    Sounds like Hash...

    Hmm...wonder if your Gate Bias is just a tad too high? Either or - or both sort of thing.

    Not all radios "quench" their RF signal as quickly as say, a Cobra 29 or other AM only types that use the Pre-Driver Emitter to Ground at the Mic (Pin 3 to Pin 1) to complete the TX keying circuit.
     
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