--- In ham_amplifiers@..., R L Measures <r@...> wrote:
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.
### They STILL open faster than any 240 Vac breaker ever will !
### The sand filled HV fuse's [5" long] kill that vapour arc so
fast, it's unreal. ... not even an issue.
### There is Nothing wrong with using a 250v 3Agc fuse/fuseholder
in the CATHODE of a linear either [in the CT of the fil xfmr]....
just shunt the 3agc fuse holder with a 100 K - 2/3 watt MOF
resistor. Put some 6A diodes [6A10, 1 kv-400A surge] back to
back, installed between chassis and B- IF the cathode fuse
blows open... you still have the 100 K resistor across it... which
biases the tube off ! Works slick..... and every time too.
...
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]
RICH SEZ.... 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.
### Not a chance ! Duty cycle on ssb is damned near 50%..
looking at any plate current meter. Rich, with ur 100' run of
4 ga CU wire... and an undersized 65 lb dahl xfmr.. and a 40A
breaker.... there is NO way you could run it key down for 1-3
seconds... just to take some steady state plate/grid cuurent
readings. Ur telling me b4 ur plate V was dropping 1000 V, while
talking.... what is it with dead cxr... 2 kv ??? You will never
know with a 40A breaker. You would be drawing an easy 110 AMPS
with 14 kw out ! Rich, if you can't possibly measure steady
state plate current..... you have nothing to reference ur average
plate current to, during typ ssb.
### IMO... using a scope to measure power out is flawed. IF the
scope is out say 5%.... ur calculated power output will be out
10%. [using V squared /R] In any event, the scope leads will
exhibit swr, and other bugs.
Later... Jim VE7RF
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org
