[TowerTalk] MFJ 998RT Hi-Power Remote Auto Antenna Tuner

[W4AAW@aol.com]

I could not find any such remote control tuner, so I built one that handles even 1.5 kw on RTTY with ease.  I use it to tweak a 135' ladder-line-fed dipole to various portions of the 80M band/per contest.

Built a frame from aluminum angle stock that faces my Johnson kW Matchbox.  I had only to remove the knobs from the Matchbox's two 1/4" capacitor shafts.


Then I modified two $6 electric screwdrivers from BigLots.  Removed batteries and tacked on 9" leads (+ & -) to the battery holder.  

Mounted the E-screwdrivers on the frame to match the the Matchbox's capacitorsrs' shaft positions.  Used 1/4" shaft stock to mate the screwdrivers to the capacitor shafts with 1/4" shaft couplers.

Ran a four wire cable into the shack. 

Connected leads from each screwdriver to its own DPDT momentary reversing switch.  These in small box in shack.

Now feed power to tuner, sit in the shack and watch my VSWR meter.  Run each capacitor either direction until best match is found.  Absolute 1:1 match easily found.

Although designed for 6VDC, these El cheapo E-screwdrivers will just creep around, starting at about 2.8 VDC, and in either direction!

No cosmetic damage to the venerable kW Matchbox.  

Later, I may use 10 turn pots to indicate position of the caps, but I haven't found this feature to be necessary.

This will have zero appeal to Plug 'n Play fans.  About $20 worth of parts and some personal effort solved my problem.  No more trudging out in snow, cold or rain to tune up 80M antenna. It should work on a single band basis for other kW tuners and requires NO cosmetic damage to any tuner.

73 Mike W4AAW



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