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On Nov 1, 2006, at 12:20 PM, zerobeat40 wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

zerobeat40 <zerobeat40@...> wrote:
Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will
work.

!. I would use 50v transistors.

For 50V transistors operating at 100W per pair, the required resistor
is 0.8 ohms, wherein you'd need 0.8nH of inductance or less, still at
15 watts. Can you find that one? For MRF150s, it's 0.5 ohms, needing
less than 0.5nH of inductance, this time at 25 watts.

Let us know.

Z

Do you have a FCC callsign?

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

zerobeat40 <zerobeat40@...> wrote:
Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will
work.

!. I would use 50v transistors.

For 50V transistors operating at 100W per pair, the required resistor
is 0.8 ohms, wherein you'd need 0.8nH of inductance or less, still at
15 watts. Can you find that one? For MRF150s, it's 0.5 ohms, needing
less than 0.5nH of inductance, this time at 25 watts.

Let us know.

Z

On Nov 1, 2006, at 10:56 AM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 31, 2006, at 12:18 PM, FRANCIS CARCIA wrote:

I suspect you would be better off with a 300 watt amplifier

running

closer to class A with transformer feed back, Most RF

transistors

RICH SEZ... I would use 50v transistors.

### Kinda tough in a mobile application...

3, YC--156s mobile. Roger that good buddy.

or some emergency
application where u use 12 vdc batteries, etc. These 50 vdc
finals don't seem to be much better than 30 vdc finals. I
believe there are some 70-100 v devices out there too.

I drive a car that uses a 208v battery.

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 31, 2006, at 12:18 PM, FRANCIS CARCIA wrote:

I suspect you would be better off with a 300 watt amplifier

running

closer to class A with transformer feed back, Most RF

transistors

RICH SEZ... I would use 50v transistors.

### Kinda tough in a mobile application... or some emergency
application where u use 12 vdc batteries, etc. These 50 vdc
finals don't seem to be much better than 30 vdc finals. I
believe there are some 70-100 v devices out there too.

### On another note.... some where I saw the specs for the common
transistor PA all these 11m ops use.. The manufacturer depicted a
graph of IMD vs power out in pep. Interesting, cuz the lower the
power out... the IMD just kept getting better.

### I still believe these 200 w xcvr's are the way to go... then
u can get a clean 50-150w out of them. Crank the idle current up
a bit... and watch the imd drop some more.

### There's no point in trying to achieve Class A specs like the
MK-V's I have.....at that point the xcvr is now better than the
linear amp behind it. The total systen IMD is gonna be the lesser
of the two. ..... unless u run the linear in class A.... which is
going to require a huge amount of anode dissipation. A sliding
bias scheme would be the ideal ticket... to minimize anode diss
during Class A. Krell does this with their Class A audio amps...
works too.

Later... Jim VE7RF

Let us know when you find that resistor.

Z

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:

tnx, Tony. Since adding RF-NFB to a transistor amplifier is as
simple as adding unbypassed R to the emitter leads, it puzzles

me

why

Ham transceiver manufacturers don't wake up and start building
pristine radios.

Since the TS-830S uses essentially a copy of the KWM-2's RF
amplifier, it isn't surprising that the 830 has a reputation

for

cleanliness.

cheerz

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 3:17 PM, pentalab wrote:

--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:

RICH SEZ.... 3A diodes will do 200a-pk. Not many HV transformers

will. The original Plywood Box amplifier used 150a-pk, 2.5A avg
diodes in a FWB > and the diodes survived at least 4 flashovers

to gnd without benefit of a HV fuse.

### All as you are doing is stressing the hell outa the diodes.
The 5th time you might not have been lucky. For a 14 kw amp,

like ur plywood box.... you shoulda been using 1 kv-6A diodes
[400A surge] like a 6A10.... the 0nly diode worth buying these
days.

### Rich, with that 40 A undersized breaker you have installed
in the 240 V line... it would be on the ragged edge on ssb to
start with... in a pre-heated condx.... a flashover would tip it
over the edge. IF you installed a 100-125A breaker, you could
have smoked the diodes. As is, with 14 kw out... ur line

current from the 240 V line would be 110 A on keydown... close to
55A on ssb.


########### Lemme re-phrase that..... "with a 253 lb dahl and a
100-125 A breaker, and no HV fuse... you have a good chance of
stressing the diodes... esp the smaller variety..... use a 440 lb
dahl and a 150 A breaker.. and NO hv fuse, imo ur plane nuts "#####

It worked okay on SSB.

Later... Jim VE7RF

Later... Jim VE7RF

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@, www.somis.org

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 3:05 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 30, 2006, at 1:21 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:...

RICH SEZ....Probably 90% of 'em will tell us that heavy straps

have zero L.

### WIDE straps do have zero L.

Not a sound wager, The 100Ω MOF resistors we use in our suppressor
retrofit kits are 20mm long and they have c. 11nH of inductance.

I measure ZERO L on a 3'
length of 3/4" wide Cu strap on my B+K 875-B. It reads down
to .1uh Even if it was .049uh or less... it would still read
00.0 uh. Let's say it was .049uh for 3' [36"]..... then a 3.6"
length of 3/4" wide strap is gonna be just .0049 uh. ... which
is zip imo. 1" wide strap will be even less uh.

You would do well to read Fred Terman's chapter on inductance.

end

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 2:00 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 30, 2006, at 1:43 PM, pentalab wrote:

it off... all was well. If that had been the INPUT

insulator,,, I

could have easily smoked the 3 A diodes,

RICH SEZ.... 3A diodes will do 200a-pk. Not many HV transformers

will. The original Plywood Box amplifier used 150a-pk, 2.5A avg
diodes in a FWB > and the diodes survived at least 4 flashovers to
gnd without benefit of a HV fuse.

### All as you are doing is stressing the hell outa the diodes.

So why didn't they fail?

The 5th time you might not have been lucky. For a 14 kw amp, like
ur plywood box.... you shoulda been using 1 kv-6A diodes [400A
surge] like a 6A10.... the 0nly diode worth buying these days.

### Rich, with that 40 A undersized breaker you have installed
in the 240 V line... it would be on the ragged edge on ssb to
start with... in a pre-heated condx.... a flashover would tip it
over the edge. IF you installed a 100-125A breaker, you could
have smoked the diodes. As is, with 14 kw out... ur line current
from the 240 V line would be 110 A on keydown... close to 55A on
ssb.

Why design one to run A0 when A0 is illegal and it triples the cost and weight of the PS?

Later... Jim VE7RF

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 1:49 PM, pentalab wrote:

--- In ham_amplifiers@..., "Phil Clements" <philc@...>
wrote:

I already had a monster blower on hand when I put my YC-156 amp
together. I drilled a hole in the wall, and ran the cooling air
thtough a 10 foot hose from another room. I hear no more noise

than

the cooling fan on my PC makes here in the ham shack.

### I learn something new every day ! I never tried remoting a
blower. I had been told that a lot of the noise was from the
actual airflow through the tube itself, so never tried it.

With the 4cx3000A, most of the noise comes from the exhaust side of the variegated anode cooling fins. The sound made is similar to wind blowing through pine trees.

### ...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 1:29 PM, pentalab wrote:

--- 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 !

Apples amd grapefruit.

### 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.

What is the potential across the 250v-rated fuse if the tube happens to be conducting heavily when the fuse opens?

...

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 !

It happened. The PB amplifier was tuned up with a 30% duty cycle 30pps pulser.

Duty cycle on ssb is damned near 50%..

Not true.

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...

I never did.

just to take some steady state plate/grid cuurent
readings.

There is no grid current in AB1. It didn't matter what the A0 plate/ anode current was. I only used the meter to set ZSAC. On an "ahhhhh" or with the tuning pulser running, the anode current meter indicated c. 1a - which was probably about 1/3 of what one would measure with an oscilloscope connected across a precision shunt R. .

Ur telling me b4 ur plate V was dropping 1000 V, while
talking.... what is it with dead cxr... 2 kv ???

I never ran A0. If I had designed it to run A0, I would have needed to use a 180lb HV xfmr and 3x as much filter C.

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.

I could not care less what the steady state current was.

### 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%.

True, but freshly-calibrated NBS-traceable oscilloscopes are used to calibrate wattmeters.

[using V squared /R] In any event, the scope leads will
exhibit swr, and other bugs.

A x1000 scope probe has very little C.

Later... Jim VE7RF

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 12:40 PM, pentalab wrote:

--- In ham_amplifiers@..., Jan Erik Holm <sm2ekm@...>
wrote:

Well right now I dont have any "official test lab" figures,
however W8JI has measured (if you trust him, I do in this
case) -47 dB.

### W8JI, ALSO claimed in the same sentence, -52db for a Drake
T4XC !

From TV sweep tubes? Not likely. .

I owned 4 of em yrs ago... and I got the same results as
the ARRL lab did... a paltry -30 db pep...

This is roughly what I've measured on the air.

or just -26db compared
to one tone... which is typ of sweep tubes. Even to get that,
Drake used 70 ma of zsac @ almost 700 Vdc.... so the idle POWER
on the pair of sweep tubes was = 99% of the rated plate
dissipation !

### What power level did u run the FT-1000D tests at ?? I
currently have 2 x FT-1000D's.... and 2 x FT-1000MP-MK-V's.
haven't measured any of em. Seems to me the arrl lab measured -
36db PEP when then 1000-d was run full bore at 200 w out.
Yaesu claimed -36db, compared to ONE tone [-42 db pep], when run
at 150w out.

### Would be interesting to know what the 1000-D is at say 100
w output ? I'm betting it's very good.

Reducing pep out sometimes slightly increases distortion.

###...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

Yahoo! Groups Links

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

On Oct 31, 2006, at 12:18 PM, FRANCIS CARCIA wrote:

I suspect you would be better off with a 300 watt amplifier running closer to class A with transformer feed back, Most RF transistors have internal emitter resistors to balance the parallel cells. Making feedback work over a wide frequency range takes real talent and good pc board layouts. gfz

zerobeat40 <zerobeat40@...> wrote:
Hey, I tried to put the NFB into a solid state amp once, being used as
a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will work.

!. I would use 50v transistors.

Let us know when you find that resistor.

Z

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

tnx, Tony. Since adding RF-NFB to a transistor amplifier is as
simple as adding unbypassed R to the emitter leads, it puzzles me

why

Ham transceiver manufacturers don't wake up and start building
pristine radios.

Since the TS-830S uses essentially a copy of the KWM-2's RF
amplifier, it isn't surprising that the 830 has a reputation for
cleanliness.

cheerz

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., Tony King - W4ZT <w4zt-
060920@...> wrote:

Jim...

pentalab wrote:

### W8JI, ALSO claimed in the same sentence, -52db for a

Drake

T4XC ! <snip>

There is NO mention of Drake or T4XC on that entire web page that

I

posted the quote from

<>. It

just ain't there.

#### Tony.... W8JI has mentioned his findings on the Collins AND
the drakes several times now on.... 'amps'. It's buried who
knows where. When 1st saw it, he mentioned the drakes in the same
sentence as the Collins gear. When I saw that, I'm wondering to
myself.... if he's got the drakes wrong.... what else does he
have wrong ? No way in hell ur gonna get -58 db pep from any
drake T4XC...couldn't been a typo... since he quotes the same
drake numbers time and again.

later... Jim VE7RF

73, Tony W4ZT

--- In ham_amplifiers@..., "pentalab" <jim.thomson@...>
wrote:

RICH SEZ.... 3A diodes will do 200a-pk. Not many HV transformers

will. The original Plywood Box amplifier used 150a-pk, 2.5A avg
diodes in a FWB > and the diodes survived at least 4 flashovers

to gnd without benefit of a HV fuse.

### All as you are doing is stressing the hell outa the diodes.
The 5th time you might not have been lucky. For a 14 kw amp,

like ur plywood box.... you shoulda been using 1 kv-6A diodes
[400A surge] like a 6A10.... the 0nly diode worth buying these
days.

### Rich, with that 40 A undersized breaker you have installed
in the 240 V line... it would be on the ragged edge on ssb to
start with... in a pre-heated condx.... a flashover would tip it
over the edge. IF you installed a 100-125A breaker, you could
have smoked the diodes. As is, with 14 kw out... ur line

current from the 240 V line would be 110 A on keydown... close to
55A on ssb.


########### Lemme re-phrase that..... "with a 253 lb dahl and a
100-125 A breaker, and no HV fuse... you have a good chance of
stressing the diodes... esp the smaller variety..... use a 440 lb
dahl and a 150 A breaker.. and NO hv fuse, imo ur plane nuts "#####

Later... Jim VE7RF

Later... Jim VE7RF

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@, www.somis.org

### Never had any problem remoting the RF deck/Hv supply either...
since we can see the wattmeters in both places... and easily tune
the amp in the other room. With variable 0 to -10 vdc in the
remote location... fed back to the ALC jack on the xcvr... and a
footswitch/wattmeter in both locations... it's easy to tune the amp
up. Just run into another room... adjust drive level... tweak
it... once the numbers are all written down, it's a moot point
anyway.... just change bands and dial by the numbers.

My shack is really small 8 x 10 x 7.5' ceiling. ...... the
concern with a remote blower would be cooking the shack with too
much hot air !!! ... even in winter.

My shack is not much larger than yours, Jim. My Harris RF-110A is
sitting in the bathroom. There is a large cooling fan in the ceiling
to pull the hot air into the attic. The Harris is no-tune, 1.8-30 mhz.
All I need is a band switch and a few toggle switches on the end of a
30 foot cable coming from the amp to change bands, bias, and a few
lamps to show what the amp is doing. The blower on the RF-110 is
incredibly loud! If you have ever heard one, you will never forget it;
like a screaming banshee. It runs on 400 hz, and I think the blades
are almost turning at mach 1! These things were installed in the
bowels of Navy ships where it made no difference. The only amp here in
the shack is a Henry 2000D converted to single-band. (160 meters)I
operate 99% CW, and only in the winter. The blower is not that bad,
but my earphones cover most of it up. I really enjoy all those toasty
BTU's coming out the top of the cabinet on a cold winter morning.

(((73)))
Phil Clements, K5PC

(((73)))
Phil Clements, K5PC

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 30, 2006, at 1:21 PM, pentalab wrote:

--- In ham_amplifiers@..., R L Measures <r@...>

wrote:

. He needs a 15k or 20k!

RICH SEZ.... Paralleling 3 tubes triples C-feedback, and

that

is

not desirable unless one is trying to build an oscillator.

The

tube that is best suited for 20k - 35k out is the

8281/4cx15000A.

200w will drive one in AB1.

### So what ?

RICH SEZ... Anecdotal sure-cures don't cut the parasitic

mustard.

### Anecdotal??

RICH SEZ... Yes

Tell that to the 300 guys who run the above
tubes just fine...sans suppressor. IMO... having the grids

bolted right to the chassis IS 99.99% of the stabilty secret.

RICH SEZ....Probably 90% of 'em will tell us that heavy straps

have zero L.

### WIDE straps do have zero L. I measure ZERO L on a 3'
length of 3/4" wide Cu strap on my B+K 875-B. It reads down
to .1uh Even if it was .049uh or less... it would still read
00.0 uh. Let's say it was .049uh for 3' [36"]..... then a 3.6"
length of 3/4" wide strap is gonna be just .0049 uh. ... which
is zip imo. 1" wide strap will be even less uh.

Semi
floated grids on a 3-500Z is just asking for trbl.

RICH SEZ... My dipmeter says the 3-500 grid resonance frequency is

c. 1MHz higher grounding with caps instead of straps.

### So what ? At least 3000 guys out there will tell you that
grnding the grids on a 3-500Z with wide strap eliminated their
parasitic problems on a 220/221/Tl-922... plus the improved imd...
plus drive power requirements DROPPED 22-25 watts.

...
RICH SEZ... What is Svetlana's price for an 8281?

### RF parts wants $1995.00 for a Svetlana 4x15.... PLUS
another $395.00 for a svetlana SK-300A socket. .. so

$2400.00

in total. You can get 2 x new Eimac YC-243's for slightly

less...

and crank an easy 30 k out the back door.... and cool em way
easier.

RICH SEZ... The YC-243 is similar to the 3cx10,000A7 / 8160.

Driving a 2-holer to full throttle would take c. 2600w and the Pi
tuned input would be a handful.

### A YC-243 is just the socketless version of a 3CX-6000A7/YU-
148. I badgered Reid Brandon to have it built. 860 w of drive
yields 14 kw out... every night. Everyone has an IPA anyway. An
L4B, on low V [1900v] mode, will yield 625w of drive for 3 x YC-
156's..... an excellent IPA.

### Building a PI-tuned input to handle 1500+ watts is a SNAP.
Two broadcast variables and a tapped 4 uh coil. The broadcast
variables are padded on 160m. In the latest project, the builder
used 8 ga solid copper wire for the 4 uh coil.... handles 1.5
kw just fine. I used 7 ga wire on my 3x3. 6 ga wire is
readily available.... as is 1/8"... 3/16"... and 1/4" tubing.
4 uh is good down to 160m. For a 80-10m tuned input... a
2 uh coil is all that's needed [for a 50 ohm tubeZ]. Heck,
Multronics still makes the 4.2 uh roller coil.... made from 8 ga
wire.

### The little bandswitch used is the small type. We used 3 x
wafers on the latest project.... one wafer to change taps on the 4
uh coil.[and pad one air cap on 160m]... 2nd wafer just pads the
2nd air cap on 160m, 3rd wafer is used to turn on the plate
choke vac relay. [shorts out the 180 uh plate choke... leaving
the 2nd 45 uh plate choke still in the circuit].

### You can see pix of all this stuff on the 'photo' page. Since
it's below the chassis, it's cooled from the blower... and runs
stone cold. The 4 x 500pf padders per broadcast cap don't drift
either.

### Check the air specs on a 3x 15 or a 4 x 15.... horrendous.
Something like 840 cfm @ 6.4" h20.

RICH SEZ... Who runs A0?

### RTTY, FM, AM...ESSB class A ...+ brief cxr for metering
purposes. If stuff is OFF resonance, and anode diss goes UP....
better have plenty of air.

And it's not 6 kw anode diss.... it's an easy 9.7 kw.

RICH SEZ.... With hydrogen cooling?

#### Listen carefully! It's 6 kw with an INLET air temp of 50
deg C [121 deg F] and 204 cfm. With an INLET air temp of 20-
25 deg C [68-77 deg F].. it's only 120 cfm.

### With an INLET temp of 20-25 deg C.. AND 300-310 cfm @ .9" h2o
... anode diss INCREASES to 9700 watts. It's got a BIG cooler
on it... 6.125" diam. The kicker is, the "stem" is smaller diam
than a YC-156/4x10, etc. Which means there is a LOT of fin area
down below. It's the easiset tube to cool outa all of em... bar
none. No horrendous pressure requirements. Even with just 6 kw
anode dissipation.... all that's required is 120 cfm @ .15" h2o.

what Ham transceiver will allow testing of IMD below –40db?

### MK-V.... -60db... depending on band.. sometimes -66db.

later... Jim VE7RF

...

R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

On Oct 30, 2006, at 1:43 PM, pentalab wrote:

it off... all was well. If that had been the INPUT

insulator,,, I

could have easily smoked the 3 A diodes,

RICH SEZ.... 3A diodes will do 200a-pk. Not many HV transformers

will. The original Plywood Box amplifier used 150a-pk, 2.5A avg
diodes in a FWB > and the diodes survived at least 4 flashovers to
gnd without benefit of a HV fuse.

### All as you are doing is stressing the hell outa the diodes.
The 5th time you might not have been lucky. For a 14 kw amp, like
ur plywood box.... you shoulda been using 1 kv-6A diodes [400A
surge] like a 6A10.... the 0nly diode worth buying these days.

### Rich, with that 40 A undersized breaker you have installed
in the 240 V line... it would be on the ragged edge on ssb to
start with... in a pre-heated condx.... a flashover would tip it
over the edge. IF you installed a 100-125A breaker, you could
have smoked the diodes. As is, with 14 kw out... ur line current
from the 240 V line would be 110 A on keydown... close to 55A on
ssb.

Later... Jim VE7RF

...
R L Measures, AG6K, 805.386.3734
r@..., , rlm@..., www.somis.org

--- In ham_amplifiers@..., "Phil Clements" <philc@...>
wrote:

I already had a monster blower on hand when I put my YC-156 amp
together. I drilled a hole in the wall, and ran the cooling air
thtough a 10 foot hose from another room. I hear no more noise

than

the cooling fan on my PC makes here in the ham shack.

### I learn something new every day ! I never tried remoting a
blower. I had been told that a lot of the noise was from the
actual airflow through the tube itself, so never tried it.

### Never had any problem remoting the RF deck/Hv supply either...
since we can see the wattmeters in both places... and easily tune
the amp in the other room. With variable 0 to -10 vdc in the
remote location... fed back to the ALC jack on the xcvr... and a
footswitch/wattmeter in both locations... it's easy to tune the amp
up. Just run into another room... adjust drive level... tweak
it... once the numbers are all written down, it's a moot point
anyway.... just change bands and dial by the numbers.

My shack is really small 8 x 10 x 7.5' ceiling. ...... the
concern with a remote blower would be cooking the shack with too
much hot air !!! ... even in winter.

### with a bigger room.... I can see the merits of a remote blower
[s]. With the entire amp remoted.... in summer time, one can
exhaust the hot air outside.... and in winter, exhaust to the
inside.

later... Jim VE7RF

(((73)))
Phil, K5PC

Alternative topologies, and using higher voltage devices make things
much easier. Common-emitter can be troublesome. We ended up going
common-drain (simple source followers), running 28V, and using a
diff-amp as the voltage gain stage, then resistive feedback to the
input stage. So, the feedback was DC to 100MHz or so. Ended up with
about 150W capability and IMD3 measured -58dBc rel one carrier. 5ths
and higher order were down substantially more.

We had tried simple xfmr feedback, problem was that the 2nd/4th/6th
order products, down near DC, were re-mixing with fundamentals to
create 3/5/7, etc. Weren't able to make xfmrs that operated close
enough to DC to get around that prob.

We worked with the semi mfr as well, trying to get internal resistors.
Turns out the technology used for emitter ballasting is fundamentally
non-linear. Good for balancing DC idle currents, but not very good
for negative feedback. In the MRF150 type devices, no such ballasting
is used, rather they depend on having 32 identical devices adjacent to
each other on a wafer, and bonding in direct parallel. Semiconductor
physics allows you to do things like that, expect adjacent devices to
be identical enough to directly parallel. In the MRF154, which was 4
X MRF150 in a single package, the drains and sources were in direct
parallel, and the only isolation resistors were in the gate paths,
cutting down on some form of cross-coupled VHF oscillation between
devices.

At one point, we feared we'd have an expensive hybrid design facing
us, but coming up with the diff-amp input, two stage buffer and final
output FETs, and getting the customer to buy off on 28V operation, did
the job. Complex circuit when we were done, and way more gain than
you want usually from a single stage, but we got the performance
without a custom hybrid design.

Hard to believe I was once in that industry...this was shore-based
marine SSB, we were supposed to meet a final system IMD of 36dBc rel
one carrier, including all stages...so we made them all super-clean,
and beat the spec by 10dB. Adjacent channel power measured far down
as well, but I don't recall the figure.

Actual torture test was to put band-limited white noise through it,
and see how much energy was in the next adjacent channel. A variation
on that test is still in use commercially, known as the "noise power
ratio" test.

Z

--- In ham_amplifiers@..., FRANCIS CARCIA <carcia@...> wrote:

I suspect you would be better off with a 300 watt amplifier running

closer to class A with transformer feed back, Most RF transistors have
internal emitter resistors to balance the parallel cells. Making
feedback work over a wide frequency range takes real talent and good
pc board layouts. gfz

zerobeat40 <zerobeat40@...> wrote: Hey, I tried to put the

NFB into a solid state amp once, being used as

a driver for commercial HF SSB. It was not so easy.

Assuming a pair of NPN transistors delivering 100 watts at 30MHz,
running from 13.8VDC, producting -30dBc IMD that we want to improve by
about 10dB. The correct value resistor is approx 0.2 ohms and it must
dissipate 15 watts, if the amp is to survive clumsy tuning into an
antenna tuner at full power. You could get away with a 5 watt device
if you insisted on only SSB (no CW or FM) and only into a matched
load. Smallest resistor I was able to find to meet this was a chip
style component, about 1/2 inch X 1/2 inch. It measured 5nH of
inductance. At 30MHz, XL=nearly one ohm. The stage gain at 30MHz was
reduced to approx 2dB, and the phase shift of this inductance reduced
the IMD benefits of the NFB to having no IMD reduction at all. At
1MHz, the solution worked very nicely - stage gain stabilized at 14dB,
and IMD measured about -42dBc (referenced to either of two incident
carriers)

If you could somehow create a 15 watt resistor that is 0.2 ohms and
under approx 0.2nH of inductance, then your proposed solution will work.

Let us know when you find that resistor.

Z

--- In ham_amplifiers@..., R L Measures <r@...> wrote:

tnx, Tony. Since adding RF-NFB to a transistor amplifier is as
simple as adding unbypassed R to the emitter leads, it puzzles me why
Ham transceiver manufacturers don't wake up and start building
pristine radios.

Since the TS-830S uses essentially a copy of the KWM-2's RF
amplifier, it isn't surprising that the 830 has a reputation for
cleanliness.

cheerz

--- 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

Jim...

pentalab wrote:

--- In ham_amplifiers@..., Jan Erik Holm <sm2ekm@...> wrote:

Well right now I dont have any "official test lab" figures,
however W8JI has measured (if you trust him, I do in this
case) -47 dB.

### W8JI, ALSO claimed in the same sentence, -52db for a Drake T4XC ! <snip>

There is NO mention of Drake or T4XC on that entire web page that I posted the quote from <>. It just ain't there.

73, Tony W4ZT