On Wed, 21 Nov 2007, Casual Fool wrote:

On Tue, 20 Nov 2007 06:42:39 -0800 (PST), "
wrote:

Look at QTH .com, HF radio / DX-100 he says it delivers 275 watts
out into a 50 ohm load..I think that must be about 300 %
efficient ..Extra class says that.. OHWELL....


275 watts may be correct, under two conditions, (1) The Bird Wattmeter
is a peak wattmeter, and the peak reading button is pressed in. (2)
The actual output of a class C modulated final (s) modulated by a
class B modulator is four times the carrier power. That said, he may
be correct, as long as he is speaking into the microphone and watching
the peak power, which would be in this case, true power. In fact, it
would be a little low.. My DX-100 while tuned to around 120 watts
carrier, and then tone modulated with a 1000/1575 cps dual tone puts
out a little over 448 watts on a Bird 4391 digital wattmeter, peak
mode, into a 1000 watt Bird dummy load.. This is why FCC regs now only
allow AM operation with a 375 watt carrier, 375w carrier X four =
1500w PEP, true power.. I do agree with all else everyone said, there
is no way a pair of 6146s in a DX-100 are going to produce a 275 watt
carrier.. Perhaps, solid stated rectifiers, new tubes, you may see 170
watts, but that would really be pushing it.. Best Regards, FWIW, Tony
WB8MLA


I agree with this. I have no idea why people like to "spin" their data but
any DX-100 should be discussed in terms of putting out about a 100-110
watt CW carrier and forget the crap about "peak" power that is there for
milliseconds, and ignores the likelyhood that there is also zero output
for milliseconds, too. A 275 watt carrier is going to mean about 350 watts
input and at 70% efficiency we're talking about double the watts converted
to heat on the plates that the plates are rated for. Did that guy say what
the plate current was and what the plate voltage was on key-down? Start
drawing overcurrent out of the HV power supply and that plate voltage is
going to drop a fair bit.

When I was a kid, a lot of guys were putting 6293s in their finals and
taling about more DC input (BFD), but they never said what their actual
plate voltage & current were. Where's the power going to come from for the
modulators? Did that extra plate current start saturating the modulation
transformer secondary? You'd get some extra heating there, too (not good).