On New Year's Day, 2006, I acquired a Henry 13.56 MHz RF Generator....and converted it over the following 6 months as shown on this page.



Rear view of the Henry 3000D converted to 6m.  Note the 50k cutoff resistor and 12 VDC zener diode mounted on the back panel.  You can also see the new 7/16 DIN RF connector installed in the rear of the Tank Compartment.  No RF is run under the chassis in that half of the amplifier.





Top view of the tank compartment from the rear of the RF deck.  The blocking capacitors used were a pair of 200 pF attached to a copper strap that is silver soldered to the anode clamp.  The coil side of the connection is to a silver plated brass plate, with the coil silver soldered to it.  A pair of 50 pF blocking capacitors were tried, but this circuit would not resonate because the slug could not be pulled far enough back out of the main tuning coil, and the loading capacitor needed more capacitance.  Using a pair of 500 pF blocking capacitors required that the slug be inserted about halfway into the coil.  Using a pair of 200 pF blocking capacitors seemed to work just as well, and only required the slug to be inserted about 1/4 of the way into the large tank coil.



The B+ is delivered to the tube via the copper strap, that simply is held underneath the anode clamp.  The RF choke was the one that came with the 14 MHz RF deck, except that only the wide spaced turns are used - the rest of the choke was cut off so the choke was shortened, and the end support bracket was moved several inches toward the rear of the RF deck (as you can see in the photo, in which the two original mounting screws for the RF choke support bracket are still plainly visible).  The final RF choke was 42 turns of #18 enamel wire on a .7" diameter Teflon form, 2.75" long.  A pair of right angle drives turn a 1/4-20 threaded brass rod, that moves the copper shorting slug into the coil for tuning.  Unit is shown tuned to 50.150 MHz.  The 1.75" OD copper tuning slug has Teflon plugs in each end, fastened with a brass screw running through the slug.   A 9/32" O.D. piece of brass hobby tubing (held in place by 1/4" O.D. brass rod running through it) supports the slug by running through the top of it.  The slug is moved back and forth  by turning a threaded brass rod that goes through the center of the slug.   The threaded brass rod goes through a panel bearing with a 1/4-20 brass nut silver soldered to it, which is mounted on a bracket silver soldered to the inside center of the 1.75" long slug.  The threaded brass rod and the 1/4" brass support rod are insulated  from ground, and supported by the two HDPE end plates.




Overall view of the RF deck from the top.  The coil was made by using almost two of the turns of the standard 14 MHz coil that came with the 3000D (1/2" diameter  tubing, 3.25" ID, 3" long).  The L coil was similarly made by using 3 turns from the original L coil (3/16"diameter tubing, 1.5"ID).  The original tuning shaft was left in its same location after removing the flapper tuning mechanism that came in the 14 MHz unit.  The original loading capacitor was used without any changes, except that the fixed doorknob capacitors in parallel with the variable capacitor (located under the silver plated brass plate at the right end of the coil) were changed from 4 capacitors to 3 capacitors (two 33 pF and one 25 pF).  Instead of an RF choke on the output connector, I used a shorted quarter wavelength of Teflon coax to provide additional second harmonic attenuation.  The initial test setup for checking out the tank circuit was to temporarily place an 1800 ohm carbon resistor between the tube's plate and chassis ground, and then connect an MFJ-259 Antenna Analyzer to the output connector.  

In the original RF deck, there were two ceramic standoffs that pushed down from the perforated cover onto the cooling fins of the tube to hold it in place.   I replaced these with a single teflon spacer between the cover and the center of the anode, so there would not be any obstruction air passing through the cooling fins.


The variable inductor is probably the most usual part of the RF Deck modification.  Hopefully, these notes will help anyone who is interested to understand what I did, so they can more easily get started on their own construction.  Two 1/2" thick HDPE 4" wide by 6" high end plates were used to support the slug assembly as it moves into the coil to reduce the inductance and tune the tank circuit.  The end plates were spaced 6" apart and secured to the chassis with angle aluminum brackets or the right angle drive assembly; they were mounted 3/4" out away from the front insdie panel of the RF Deck.  The HDPE end plate next to the loading capacitor is actually only 3" wide on the bottom - it has a 1" x 3" notch cut out of it to provide clearance for the connector plate and fixed doorknob capacitors between the loading capacitor and the tank coil.



The slug shafts were located so the 1-3/4" long slug (which is 1-3/4" in diamater) runs through the centerline of the tank coil, which is  3-1/2" above the bottom of the plate compartment.  The threaded rod goes through the center of the slug, and the brass hobby tubing for support and alignment runs through the slug 1/2" above it.  The threaded rod goes through bushings on each HDPE end plate, and is kept from moving back and forth by the flexible coupling connection it to the right angle drive assembly and by the locked double nuts on the far end of the shaft.  The alignment tubing is held betwee the two HDPE end plates by 1/4" brass washers that go over the 1/4" brass rod that runs through the alignment tubing and is secured on the outside of the HDPE end plates by cotter pins.  If you have more clearance, you could also use 1/4" brass threaded rod with nuts on each end to secure the alignment tubing.  An extra piece of teflon sheet was inserted between the variable loading capacitor plate and the HDPE end piece to prevent arcing off the ends of the brass rod which extends through the end piece to secure it.