On Oct 30, 2006, at 5:14 PM, pentalab wrote:
--- In ham_amplifiers@..., R L Measures <r@...> wrote:
### what have u got against HV fuses Rich?
RICH SEZ.... Do you carry two spare tires in your car? As I see
it, overkill is not good engineering - except perhaps on a moon
mission if I going.
### RL Drake used a .82 ohm 1 watt reistor in the B+ as a HV
fuse.... it always blows
RICH SEZ.... It is not a fuse at 2500v, it was a temporary metal
vapor arc that had a v-drop of c. 20v during the period when it
should have been limiting current.
#### Rich, obviously a .82 ohm resistor is not gonna limit
current. It's in there as a HV fuse.. that's it.... and easily
replaced...
You missed the point: A fuse that creates a metal vapour arc when it opens does not adequately limit peak-I until the arc is extinguished. This is why 250v 3AG fuses are bad engineering practice when used in a several kV application.
either with another .82 ohm-1 watt R... or a single
strand of real small ga wire.
Small wire also forms a metal vapour arc as it melts.
Either way... it opens BEFORE the
primary circuit breaker's open up. I have never had the breakers
on all 4 of my L4B's ever open in last 30 yrs.
...
RICH SEZ....The Henry 2k-4 has a resonant-choke filter --
perfect
for 120v operation with virtually no drop in PEP out.
### Trbl is... you would have to run a new heavy duty 20-
30 A 120 V line into the shack to run a Henry 2K-4.. on 120 V.
RICH SEZ... Not true. They run FB on SSB from a 120v, 15a circuit.
####### DREAM ON !! 120v x 15 A = 1800 va To calculate AC
mains VA.... take the DC input in watts and multiply x 1.22 [this
factor's in 10% for core losses.. and another 11% for power
factor]
The duty-cycle of 2-way SSB is under 20%. The old Plywood Box amplifier did 14 out on SSB and it did not trip the 40a, 240v breaker.
EG 1500w out/.63 = 2380 w input. 2380 x 1.22 =2904 va. 2904
Va/120 v = 24.2 AMPS !! Ur 120 v line is gonna SAG way b4 the
15 A breaker pops open.. with it's rinky dink 14 ga cu wire.
In
which case, you may as well run a 240V line in the 1st place...
unless u are talking about 600 w pep out on ssb.
RICH SEZ... no, 1500 pep. Resonant-choke filter DC supplies are
wonderful until you have to lift the sucker.
#### Resonant-choke filters, imo... are the most useless bloody
things ever devised.... and don't tell me 50 kw Broadcast
staion's use em.. they don't....
end
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org
