Lot of work for naught.. the power limit on 630M is 5 watts and even
with a very poor antenna
you only need 100 to 200 watts to get 5 out of the antenna. A single
or two MOSFET amplifier
will do that no problem and will fit in a mini-box.
NO3M has converted a SB-1000 think it was, he used it under his
experimental license which has
higher power limits. Google NO3M and there are pictures or some info.
There are a couple others on line that converted tube amps. Almost none
use them now.
MOSFET amps are doing 80 to 90 percent efficiency, why waste a tube amp
at 50 to 60
percent.
No high voltage, no fans, much better ways to go these days,
especially on 630M
73 Merv K9FD/KH6
"U may well have a tough time stuffing parts into a SB-200 chassis. This is where
a simple, bigger box would help out. Something like a single 3-400Z / 3-500Z would do
the trick, dead simple. Then u could also stuff a 4-400 A / B /C in there as well."
Yes, it may make sense to pull some of the larger tuning and LP filtering
components into a separate case, outside the SB-200 case. One nice thing about
VLF is that tolerances are very loose for things like lead lengths. Just be
sure that wires carrying high voltages are very well insulated.
I'm certainly open to having a second case with the additional filtering
components. That second case won't have a power supply or tubes needing
cooling, which simplifies things greatly.
I'm not dead set on starting with an SB-200 by any means. If a junk 3-500Z or
4-400 amp drops into my lap, I could just as readily run with that. I will
check out NEARFEST on the spring and see what turns up.
If anyone in New England reads this and thinks they may have a suitable amp for
sale (no tubes is fine, burned bandswitch is fine, power supply must be good,
price must reflect condition; looking for a low-priced junker amp for extensive
modifications), please reach out to me directly.
73,
Cathy
N5WVR
<n5wvr@arrl.net>
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