[Amps] Convert Heathkit SB-220 to 50Mhz

[Dino Darling]

This would make a great article for QST!  But I wouldn't blame you for not 
wanting to put your head on the chopping block!

At 10:43 AM 08/18/2004 -0700, you wrote:
>I don't know what conversions you've seen, but I've converted three SB-220s
>to six meters over the years, and each the same way.  In all cases, I got
>rid of the bandswitch entirely and used that hole to mount a 2-30pF vacuum
>variable capacitor; got rid of the LOAD cap entirely and used the original
>TUNE cap as the new 6m LOAD capacitor; re-wound the plate RFC with many
>fewer turns (only need about 1/4 the original winding length for 6m);
>eliminated the original bandswitched input networks and replaced them with a
>single network for 6m only; added more front panel grounding (aluminum
>bracket) for the new plate tune & load caps (the inductance via the front
>panel is too high); replaced the original parasitic suppressors with new
>ones having the carbon resistor soldered across 1/2-turn of copper 1/4" wide
>strap; stuff like that.  The conversion takes about one full day (8 hours)
>and works well.
>
>With good tubes, I get about 900W output on six.  The original T-R relay
>isn't the greatest on 50 MHz, and I often go to a conventional Dow-Key
>dual-pole coaxial relay like the DK-260 to pick up about a dB or so in
>performance (even on receive).  Of course, I add the "standby switch" mod
>and also the "low voltage keying mod" to any SB-220 before I even get
>started!
>
>Are you familiar with this stuff?
>
>73 de Steve WB2WIK/6

Dino...k6rix at earthlink.net