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Antenna tuner with swr meter covering at least 135-1000KHz?

Discussion in 'The Low Bands - 630/2200 Meters - VLF' started by AF5IE, Jan 26, 2019.

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  1. KB2FCV

    KB2FCV Ham Member QRZ Page

    I would guess that anything commercial for that range will be surplus stuff out there.. maybe stuff meant for the NDB Beacon band (there are more and more of those being decommissioned, sadly). For our applications, I suspect anything needed for an antenna tuner will have to be scratch built / homebrew / built from found parts.

    I have a kit I need to put together to begin transmitting on this band but I'll still need to figure out what I'm going to do for an antenna. My receiver is an ARC-5! :)
  2. 2E0ILY

    2E0ILY Ham Member QRZ Page

    If you are going to TX on LF or MF a Scopematch, bought or home made, is the BEST device you can have they are an instant or continuous check on the antenna and can save boxes of blown FET's trying to transmit into an unsuitably matched aerial. Making an outdoor variometer motor driven, or automatically adjusted will save time and wet clothing, mine is a simple 1RPM Ebay sourced geared motor and a centre sprung off toggle switch in the shack. I haven't got around to limit stops, but tuning is so sharp minimal rotation of the variometer inner coil is required so I have yet to drive the gear off the quadrant ;) My friend and I have modded a well known MF amp design to use a single modern Cree silicon carbide FET and it gives a reliable 400 Watts plus on MF digi modes on 60V to the drain. A TS-590 using the DRIVE 0dBm socket is enough to act as the exciter. If we built another we'd increase to toroid core sizes one size up as on full whack it needs a small fan to keep them cool. the FET itself runs very cool on a minimalistic heat sink. Spend time resonating the antenna though they tend to be such a high Q that a mismatch WILL blow FET's. Next project is a valve (tube) amp :)
    WQ2H likes this.
  3. WQ2H

    WQ2H QRZ Lifetime Member #214 Platinum Subscriber Life Member QRZ Page

    RE: Variometer rotate mechanism

    If you've got an old antenna rotor around - that will work just fine !!
    (just make sure it's all in a waterproof enclosure) :rolleyes:

    KB2FCV likes this.

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