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

[Steve Katz]

Oops, forgot to mention, my plate tank for 6m (SB-220 mod) is 3-1/2 turns of
1/4" copper tubing on a 1-1/2" diameter form (inside diameter of the tank
coil); plate TUNE cap is 2-30 pF Jennings vacuum variable, either 5kV or
7.5kV (either model seems to work); plate LOAD cap is the original TUNE cap
from the SB-220.  I don't re-use any of the original tank circuitry at all,
except for the old TUNE cap, which I re-use as the new LOAD cap for six.

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:	Steve Katz 
> Sent:	Wednesday, August 18, 2004 11:12 AM
> To:	'Manuel "Teknik forumet"'
> Cc:	'amps at contesting.com'
> Subject:	[BULK] - RE: [BULK] - [Amps] Convert Heathkit SB-220 to
> 50Mhz
> 
> 
> Manuel,
> 
> I'd suggest you go ahead and try that, but in my experience, that's a
> lousy
> modification.  It assumes you're sacrificing only the 10m band for 6m, and
> leaving the other bands intact, including the bandswitch and its wiring,
> with its parasitic reactance.  I've never found that to work efficiently
> or
> in a stable manner on six meters, but you can certainly give it a try.
> 
> My SB-220 mods sacrifice the amp for six meter operation only, and I get
> rid
> of the bandswitch altogether.  It's the only way I've found to make it
> work
> with full-time stability and high efficiency (900W output power at 50
> MHz).
> 
> WB2WIK/6
> 
> > -----Original Message-----
> > From:	Manuel "Teknik forumet" [SMTP:manuel at limmared.nu]
> > Sent:	Wednesday, August 18, 2004 11:31 AM
> > To:	Steve Katz
> > Subject:	SV: [BULK] - [Amps] Convert Heathkit SB-220 to 50Mhz
> > 
> > Hi
> > Thank´s for this information.
> > I have found a lot of mods, but nerly evryones are like 
> >  1) Move the 10-meter tap on the plate coil (L6) to a point 1-2/3 turns
> > from
> > the plate-tune capacitor. A grid-dip oscillator can be used to check
> > resonance at 50 MHz. 
> > 2) Unwind the 10-meter input coil (L1), leaving 2-3/4 turns. 
> > 3) Replace C33 and C34 by a single 10 pF mica capacitor. 
> > 4) Change C35 (115 pF) to a 33-pF mica capacitor.
> > 
> > Manuel SM6TMR
> > 
> > -----Ursprungligt meddelande-----
> > Från: Steve Katz [mailto:stevek at jmr.com] 
> > Skickat: den 18 augusti 2004 19:44
> > Till: 'Manuel "Teknik forumet"'; Amps at contesting.com
> > Ämne: RE: [BULK] - [Amps] Convert Heathkit SB-220 to 50Mhz
> > 
> > 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
> > > 
> > > 
> > > _______________________________________________
> > > Amps mailing list
> > > Amps at contesting.com
> > > http://lists.contesting.com/mailman/listinfo/amps
> > 
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