No Spam (ckh) wrote in message news:ifgU75G3LLdo-pn2-kEdUYg28iQwO@localhost...
On Sun, 7 Sep 2003 19:36:42 UTC, (N2EY) wrote:

It might take ten times the power to run a tube rig on idle as
solid state. I'm not sure of the real numbers but I'd guess 5
watts for my solid state ICOM and 50 watts for my SB-102.

Most manufactured solid-state rigs require 1-2 amps on receive - that's 12-24
watts.

I'm surprised that it's that high but I was guessing the draw based
on what it takes to run simpler electronics.

I took a quick spin through the QST Product Reviews of ICOM HF rigs,
looking at "drain on receive". The IC-703 draws the least (.58 amps)
but it's not 100 W, as I recall. The IC-725 clocked in at 0.84 amps.
Then came the IC-728/729 (0.95), IC-707 (1.0) IC-706MkIIG (1.4),
IC-737 (1.45), IC-718 (1.7), IC-736 (1.7), IC-746PRO (1.9) and the
IC-756ProII at a whopping 3.2A (!). Looks like an average of 1.5 amps
or so to me.

The AC-powered ICOMs I looked at were as power-hungry as tube rigs.
The old IC-765 was rated to draw 80W on receive and up to 650W (!!) on
transmit. The IC-775 review says "150 VA on receive, up to 760 VA on
transmit", which brings into play the fact that AC supplies are not
always purely resistive loads.

I don't know what model ICOM you refer to but 5 watts at 12 volts is less than
half an amp.

The SB-102 requires 12 volts at 4.75 amps (or so) to light the heaters, 300
volts at about 100 mA B+, and some bias. Works out to 57 watts of heaters, 30
watts of B+ and maybe 3 watts of bias - say 90 watts total. Press the key and
you add 800 volts at 240 mils - about 280-290 watts total.

ah, I forgot the idle plate current. My guestimate of "The 6 or 12
volts to light the filaments is probably 50-60 watts." was close.

Very close!


Remember, though, that the efficiency of the power supply has to be considered,
both in the solid-state and tube case. In the case of heater power, a
transformer is very efficent (90-95%). Unregulated DC from a typical SS suply
is almost as good - (80-90%). Regulated DC (typical series-pass-transistor SS
supply) can be much worse - down to 50% (worst case) when a big supply runs at
light load, because the pass transistor has to burn up a lot of volts.

Forgot that too.

PS efficiencies vary all over the place. Dynamotors are maybe 60%
efficient. Power transformers can be 95% efficient or better. The rest
are in the middle someplace.

So in the case of a tube rig that needs 90 watts from the power supply on
receive, the AC demand might be 110 watts. Compare that to an SS rig that needs
2 amps at 12 volts on receive but has a power supply with ~50% efficiency at
light load - total AC demand 90-100 watts. (This is why switching supplies are
so popular - they are very efficient).

If your primary power source is 12 volts, it's a whole different ball game
because the SS rig doesn't even need a power supply.

--

On transmit, my ICOM spins the fan and draws 20 amps at 12 volts,
240 watts. The SB-102 might take 300 watts.

Both are reasonable numbers, but note that often the "12 volts" is actually
more like 13.8.

The Elecraft K2/100 requires only 250-350 mA (depends on options) at nominal 12
volts on receive. I don't know of any full-feature rigs that draw less on rx.

I've been looking at the Elecraft. Seems like a nice package.

I built K2 #2084 and it's a real winner. Receiver only draws 260 mils
with all the goodies turned on.

I'm
not real interested in the state-of-the-art prebuilt rigs because
they are beyond my ability to fix. I have a small-ish collection
of Heathkit SB's that I'm fixing up.

The Elecraft is a kit, and the instructions are better than anything
I've seen, going back to Heathkit and EFJ. There is an online
reflector and archive plus tech support. They are very "fixable" rigs,
but I've had almost no trouble with mine in 2+ years. You can build it
one option at a time.

One guy modded his old HW-101 to be an external amp for his K2. And it
still works as an HW-101!

The only bad thing is that they don't glow.

The SB family shares a lot of parts, and they're not rare. The HW-100
and '101 also share lots of parts with the SB series. Pick up a few
hangar queens and you're set for most parts.

One trick some folks do is to resurrect an HW-101 and install the VFO
from a derelict Tempo One. The Tempo VFO is the same tuning range but
has a nice gear drive and accurate readout.



73 de Jim, N2EY