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Connecting an Elecraft K3 to a Drake L-7 amp.

Discussion in 'Amateur Radio Amplifiers' started by NF9L, May 9, 2012.

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  1. NF9L

    NF9L Ham Member QRZ Page

    I just got a good deal on a very clean Drake L-7 amp (2- 3-500Z tubes). I was hoping someone might know how to connect them together. The amp has the normal RF in and out connectors. It also has two rca connectors, one says VOX and the other says AGC.

    Thanks for any help
  2. W1QJ

    W1QJ Ham Member QRZ Page

    vox line is for tripping the antenna relay, agc is the alc connection. Check your K3 manual for a ground on transmit for amps and connect to the vox rca input, then check for the alc connection and connect to agc rca. The connections should be discussed in the K3 manual
  3. W9GB

    W9GB Ham Member QRZ Page

  4. KO6WB

    KO6WB Premium Subscriber QRZ Page

    The KEY OUT jack on the back of the K3 is connected to The VOX on the L-7. Make sure the keying voltage coming out of the L-7 is a positive voltage under +200VDC and under 5A.
    The ALC circuit should not be connected. The only reference I found on the K3 ALC specification is that the level must vary between 0 to +5 VDC. This is completely reversed from what most amplifiers will supply, which is in the range of 0 to -11VDC.
    The newer K3's have a modification to the ALC that allows negative voltage control which is the way everybody else does it. Check your K3 for the modification. Information here;
    Hope this helps
    Last edited: May 10, 2012
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