[BULK] - [Amps] Convert Heathkit SB-220 to 50Mhz

[Steve Katz]

Manuel, is nobody answering you on this?

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

"There is no reason anyone would want a computer in their home." - Ken
Olson, Chairman & Founder, Digital Equipment Corporation (1977)

> -----Original Message-----
> From:	Manuel "Teknik forumet" [SMTP:manuel at limmared.nu]
> Sent:	Wednesday, August 18, 2004 10:52 AM
> To:	Amps at contesting.com
> Subject:	[BULK] - [Amps] Convert Heathkit SB-220 to 50Mhz
> 
> Hi
> 
> 
> 
> Have get a Heathkit SB-220 and like to convert it to 50Mhz.
> 
> Have seen different modds on the Internet, so i like to know the best way
> to
> mod this amp?
> 
> Anyone?
> 
>  
> 
> Manuel SM6TMR
> 
> manuel at limmared.nu
> 
> 
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