>
>I have a (slightly non-sequiter) question: why do I
>always see stuff about the SB220 but never ANYTHING
>about the SB221?
>
>I have the SB221. I never have even seen one for sale
>- even on eBay.
>
>Anybody know what the differences are between the
>SB220 and the SB221??
>
>Thanks,
>Mike
>
? The SB-220 has a 5-pos. bandswitch and a 10m pi input instead of
4-pos. and no 10m pi input. The missing bandswitch contact can be added
with #0-80 hardware. //
The 220 has a Tune-C that usually breaks down at c. 4kV -- before the
open contacts on the (c. 5kV) bandswitch can arc. This protects the way
more frangible bandswitch from inadvertent arcing. Early production
SB-221s used the 4kV SB-220 Tune-C. However, at some point, Heath
switched to a wider spaced Tune-C on the SB-221. As a result,
intermittant arcing shifted from the Tune-C to the bandswitch. This is
not good news. The easiest fix is to bend the first rotor plate on the
wide spaced Tune-C so that the breakdown potential is lowered c. 20% to
4kV. // The SB-221 has an 11m filter that must be removed if 10m
capability is added. // Like the 220, the 221 T/R switches way too slow
for modern radios. High-speed switching can be added for c. $60 US.
(see Figure 7 on my Web site, or see January 1994 *QST*). // A
stepstart will prolong the life of the power switch. Lower Rp
suppressors will reduce tank arcs. // The ALC on both the 220 and
221is about as useless as the tits on a boar pig.
cheers, Mike
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|