DX-100
 

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....

DX-100
 

DX-100
 

On 11/20/07 9:40 AM, in article u_E0j.588$r81.428@trndny05, "Edward
Knobloch" wrote:

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....

He said 235W out, as visible on the Bird. He's got it dipped at 350mA,
and if he solid-stated the HV rectifiers and gets say 1KV on the plates,
it should be possible. (Granted, not for long until the 6146's give
out.) It's a very handsome DX-100.

73,
Ed Knobloch

All BS aside, NO DX-100 ever made would or ever did do 235W out.

DX-100
 

Don Bowey wrote:
On 11/20/07 9:40 AM, in article u_E0j.588$r81.428@trndny05, "Edward
Knobloch" wrote:

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....
He said 235W out, as visible on the Bird. He's got it dipped at 350mA,
and if he solid-stated the HV rectifiers and gets say 1KV on the plates,
it should be possible. (Granted, not for long until the 6146's give
out.) It's a very handsome DX-100.

73,
Ed Knobloch

Don Bowey wrote
All BS aside, NO DX-100 ever made would or ever did do 235W out.


Hi,
I don't know what's under that DX-100's hood (perhaps a third 6146,
per the mod appearing in the Yahoo Heathkit group archive,
or a couple of big sweep tubes) I am just
pointing out that the power output shown is consistent
with the plate current shown, assuming the original
HV transformer is used - no laws of physics are violated.

I think a pair of 6146's +might+ be able to make 235W out
using much higher than normal screen voltage,
but only for a matter of minutes before tube failure.
I'd interpret such high output on an unmodified DX-100
as a fault condition.

73,
Ed Knobloch

DX-100
 

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

DX-100
 

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).

DX-100
 

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.

Just a remark on Bird wattmeters:

- it is true that a peak wattmeter will correctly show the peak power of a 100%
amplitude-modulated carrier (4 times the unmodulated carrier power)
- conversely, a normal (i.e. non-peak) wattmeter will NOT correctly measure the
average power of a carrier 100% amplitude-modulated by a sinusoidal tone (that
is 1.5 times the carrier power).

Reason is that the (non-peak) wattmeter actually measures the average voltage
of a rectified RF signal sample and displays the measurement result in terms of
RF power by the use of a non-linear (quadratic) meter scale.

The average voltage of the rectified RF signal does not vary when modulation is
applied, as the positive peaks are perfectly compensated for by the negative
peaks. Such compensation does not instead occur with regard to RF power, as the
positive-peak power is, as already said, 4 times the unmodulated carrier power
and not just 2 times.

In conclusion the Bird wattmeter (and all other wattmeters working on the same
principle) will show the same RF power, independently of whether the carrier is
modulated or not. And that is clearly wrong.

Only measurement devices that actually measure RF power (e.g. bolometers) will
correctly show the modulated carrier power.

73

Tony I0JX

DX-100
 

On Wed, 28 Nov 2007, Antonio Vernucci wrote:

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.

Just a remark on Bird wattmeters:

- it is true that a peak wattmeter will correctly show the peak power of a
100% amplitude-modulated carrier (4 times the unmodulated carrier power)
- conversely, a normal (i.e. non-peak) wattmeter will NOT correctly measure
the average power of a carrier 100% amplitude-modulated by a sinusoidal tone
(that is 1.5 times the carrier power).

Reason is that the (non-peak) wattmeter actually measures the average
voltage of a rectified RF signal sample and displays the measurement result
in terms of RF power by the use of a non-linear (quadratic) meter scale.

The average voltage of the rectified RF signal does not vary when modulation
is applied, as the positive peaks are perfectly compensated for by the
negative peaks.

This is plausible only with a pure, single-tone sine wave audio input
signal. I have looked at my own voice on an AM-modulated carrier on a
scope: it is highly asymmetrical. Even the books sometimes mention this.

Such compensation does not instead occur with regard to RF
power, as the positive-peak power is, as already said, 4 times the
unmodulated carrier power and not just 2 times.

In conclusion the Bird wattmeter (and all other wattmeters working on the
same principle) will show the same RF power, independently of whether the
carrier is modulated or not. And that is clearly wrong.

There are peculiar circumstances when AM results in upward or downward
plate current deflections upon modulation ... all with their own
symtomology and causes.

Only measurement devices that actually measure RF power (e.g. bolometers)
will correctly show the modulated carrier power.

I think a scope looking at RF voltage (with either a digital or
electrostatic waveform "storage" functionality) into a pure resistive
dummy load would be just fine.

73

Tony I0JX