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 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

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

On Oct 31, 2006, at 7:32 AM, Tony King - W4ZT wrote:

R L Measures wrote:

What is the total IMD of a KWM-2 ?

<snip>

Tom says the following:
"IM3 levels of -30 dB are really very poor. An old KWM2 I tested was -47
dB using ARRL standards. Compared to something like an IC-756, the
Collins had about 50 times LESS power in total adjacent channel
distortion products!"
<>

73, Tony W4ZT

.

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

R L Measures wrote:

What is the total IMD of a KWM-2 ?

<snip>

Tom says the following:
"IM3 levels of -30 dB are really very poor. An old KWM2 I tested was -47 dB using ARRL standards. Compared to something like an IC-756, the Collins had about 50 times LESS power in total adjacent channel distortion products!"
<>

73, Tony W4ZT

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.

Myself I have measured a KWM-2 compared to a FT-1000D, KWM-2
was almost 15 dB better, you can see here



I have a faint memory that Ive read someplace -56 dB however I dont
remember more.

In any case I think its safe to say that a KWM-2 is far better then -40 dB, or a 32S-3 for that matter.

73 Jim SM2EKM
-----------------------------------------------------------------------------
R L Measures wrote:

What is the total IMD of a KWM-2 ?

On Oct 30, 2006, at 9:25 PM, Jan Erik Holm wrote:

As far as I know a Collins KWM-2

/ SM2EKM
-------------
R L Measures wrote:

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

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

开云体育

As far as I know a Collins KWM-2

/ SM2EKM
-------------
R L Measures wrote:

If I recall, they have the QRO brand of amps set up this way, or I
seen one being modified I can't remember which. All they did was
mount a button type thermostat near the tube. Seems to me though they
used a single speed blower and used a resistor in series with the
line lead. The thermostat simply shorted out the resistor when it go
hot enough to close.

If it were me, I'd mount a small heatsink on the thermostat to catch
the hot air transfering it to the metal end of the thermostat. Maybe
make one from thin copper sheet (valley copper). One for a small
power transistor mounted on the metal end of the button would do it
and mount either near or in the heated air flow of the tube. You
would want a N/O type contact on the thermostat. You can buy these at
Granger for practically nothing along with the blower. The resistor
was a power resistor, maybe 25 watt, but I can't remember the value,
maybe 50 ohms or less.

Best,

Will


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

R L Measures wrote:

On Oct 30, 2006, at 11:08 AM, zerobeat40 wrote:

Forget the link to the datasheet:



The only thing I have against the YC-156 is the noise...damn,

they're

loud, if you're wanting to run power and keep 'em cool.

One advantage of an 8171 is that a quiet 1700rpm blower will cool

one

VFB on SSB.

You can get a 1500 RPM blower from Dayton that will cool the YC-156/

179

and not be loud. They've got a nice two speed blower that'll do

even

better if you sense the cooling air temp and switch the speed ;)

73, Tony W4ZT

On Oct 30, 2006, at 6:38 PM, Tony King - W4ZT wrote:

The only thing I have against the YC-156 is the noise...damn,
they're
loud, if you're wanting to run power and keep 'em cool.

You can get a 1500 RPM blower from Dayton that will cool the
YC-156/179
and not be loud. They've got a nice two speed blower that'll do

even

better if you sense the cooling air temp and switch the speed ;)

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.

(((73)))
Phil, K5PC

On Oct 30, 2006, at 6:38 PM, Tony King - W4ZT wrote:

R L Measures wrote:

On Oct 30, 2006, at 11:08 AM, zerobeat40 wrote:

Forget the link to the datasheet:



The only thing I have against the YC-156 is the noise...damn, they're
loud, if you're wanting to run power and keep 'em cool.

One advantage of an 8171 is that a quiet 1700rpm blower will cool one
VFB on SSB.

You can get a 1500 RPM blower from Dayton that will cool the YC-156/179
and not be loud. They've got a nice two speed blower that'll do even
better if you sense the cooling air temp and switch the speed ;)

Two speeds are good, Tony, and proportional speed control with a DC- brushless motor is better yet Tektronix was doing this 30-yrs ago.

73, Tony W4ZT




Yahoo! Groups Links

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

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.

either with another .82 ohm-1 watt R... or a single
strand of real small ga wire.

Small wire also forms a metal vapour arc as it melts.

Either way... it opens BEFORE the
primary circuit breaker's open up. I have never had the breakers
on all 4 of my L4B's ever open in last 30 yrs.

...

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]

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.

EG 1500w out/.63 = 2380 w input. 2380 x 1.22 =2904 va. 2904
Va/120 v = 24.2 AMPS !! Ur 120 v line is gonna SAG way b4 the
15 A breaker pops open.. with it's rinky dink 14 ga cu wire.

In
which case, you may as well run a 240V line in the 1st place...
unless u are talking about 600 w pep out on ssb.

RICH SEZ... no, 1500 pep. Resonant-choke filter DC supplies are

wonderful until you have to lift the sucker.

#### Resonant-choke filters, imo... are the most useless bloody
things ever devised.... and don't tell me 50 kw Broadcast
staion's use em.. they don't....

end

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

R L Measures wrote:

On Oct 30, 2006, at 11:08 AM, zerobeat40 wrote:

Forget the link to the datasheet:



The only thing I have against the YC-156 is the noise...damn, they're
loud, if you're wanting to run power and keep 'em cool.

One advantage of an 8171 is that a quiet 1700rpm blower will cool one VFB on SSB.

You can get a 1500 RPM blower from Dayton that will cool the YC-156/179 and not be loud. They've got a nice two speed blower that'll do even better if you sense the cooling air temp and switch the speed ;)

73, Tony W4ZT

On Oct 30, 2006, at 11:08 AM, zerobeat40 wrote:

Forget the link to the datasheet:



The only thing I have against the YC-156 is the noise...damn, they're
loud, if you're wanting to run power and keep 'em cool.

One advantage of an 8171 is that a quiet 1700rpm blower will cool one VFB on SSB.

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

On Oct 30, 2006, at 1:57 PM, Peter Voelpel wrote:

________________________________

From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of pentalab

### These YC-156/YC-179's.. with their almost 19db of gain..

RICH SEZ..... Eimac says the gain is 14.2db at 6kV.

### Who cares what Eimac sez ?

...
### ...
I rather do my own measurements.
Other builders talk like fishermen,

Excellent chortles, Tnx, Peter

when I visit them I see and measure the
truth ;-)

73
Peter

...

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

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

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

a friend and I had the same problem once with a qro rig and went

with two tall insulated standoffs with a singls strand of RG8
shield. Smaller wire would fuse at lower currents. gfz

## I have used the exact same deal... used one single strand from
the multi strands in the Belden 10 kv test prod wire. One day it
blew. [op error]... and blew right away [no load] when replaced.

### Stuck my dvm between chassis and top of each insulator [all
HV wiring removed at each end, no fuse wire]... and the output
insulator read a DEAD SHORT ! How can a 1.75" tall insulator
read a dead short? Got in with a dentist mirror.... and on the
back side.... it had vapour deposited top to bottom ! Scrubbed
it off... all was well. If that had been the INPUT insulator,,, I
could have easily smoked the 3 A diodes,

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.

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

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??

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.

Probably 90% of 'em will tell us that heavy straps have zero L.

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

My dipmeter says the 3-500 grid resonance frequency is c. 1MHz higher
grounding with caps instead of straps.

...
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.

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 4cx15000 drives to 60 in with 200w.

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

Who runs A0?

I saw a FM broadcast Tx
with 2 x 3x15's.... it had a 5 HP- 3 phase blower.... just to
cool em.

... and it sucked up floor tiles.

A lousy analogy woul be like trying to stuff 100 cfm
through a key hole.

Cooling a 4cx15,000A for SSB is way easier.

### These YC-156/YC-179's.. with their almost 19db of gain..

RICH SEZ..... Eimac says the gain is 14.2db at 6kV.

### Who cares what Eimac sez ?

I

...



### Notice how Eimac sez u need 450 w to drive a 3x3 ?

Piece of cake with an SB-200.

That put
hundreds of guys off using that tube for yrs on end. Folks didn't
like the 500 ma zsac either. Turns out with 50 w of drive = 1.5
kw out. 200 w of drive = 5200W out.... and that's with just
4.8 kv under load. The tube is squeaky clean with 150 ma of zsac.
Then along comes the 11m ops... running 8 kv under load.

I heard about Hams back East doing 8kV first. Hams are notorious for
running over-voltage -- like 1500v on 1625s (sic). A Ham friend of
mine ran 8500v mobile to a pair of 4-1000A on 75m. To power it, he
pulled a surplus 10kW, 240v Army motor-generator trailer behind his
GMC truckmobile. The two biggest problems he had was squirreliness
due to the extra gain with that much V, and corona up top. Bananas.

are
the 4-1000 for the new milenium... quick, where's that pole pig ?

### I'm serious....

RICH SEZ... Serious people look at the mfg's spec sheet instead
of speculating.

### So where's all the missing specs for a 3CX-6000A7 in AB-2,
GG ??? Eimac just gives us FM Class C broadcast specs.... turns
out they also quote running ZERO bias. Obviously, with zero
bias... it's in AB-2... NOT class C. They are also quoting near
impossible efficiency numbers... when figuring out their 'typ op
condx' and take plate v x plate I... and their "estimated
output"... and start coming up with ridiculous eff numbers....
meanwhile with zero bias... the tube(s) are more like pushing
Class A region... and cooking on idle.

Eimac to this day can't tell you what the input Z on that tube
is.

In g-g, cathode input-Z fluctuates wildly over the 360?.

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

With hydrogen cooling?

They can't even tell u what the grid current is gonna be....

In AB2 g-g, grid-I depends on how heavily it's loaded. In any event,
grid-I is okay as long as it's tuned for max pep out with max drive.

nor the
specs on the 3x6 for imd either.... turns out the 3x3 and 3x6
are the best imd triodes going.

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

...

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

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

### If u are gonna parallel a 2 x pole 50A breaker, so it

handles 100 A... you have to do it right.... enter on one
corner...and exit diagonally on the output. Then the current
will split 50-50 on the poles.

RICH SEZ.... At 60Hz?

### Yeah... at 60 hz...... 50hz if u live in EU.

Later

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

On Oct 30, 2006, at 9:01 AM, Frank Goenninger wrote:

Am 30.10.2006 um 12:02 schrieb R L Measures:

RICH SEZ....Hello, Frank == A HV fuse in the secondary does not

protect the HV- transformer any better than a circuit breaker in the
primary. cheerz

Yes, but it might protect a few other parts of the PS...

RICH SEZ....Such as _________?

### Don't get sucked into this arguement Frank.

### Rich..... seen any 10-100 kw broadcast stations... with NO
HV fuse in the B+ ??? I guess their all nuts too.

later.... Jim VE7RF

cheers, Frank

Thanks, Rich, for the heads up.

73, Frank DG1SBG

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

--- 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... either with another .82 ohm-1 watt R... or a single
strand of real small ga wire. Either way... it opens BEFORE the
primary circuit breaker's open up. I have never had the breakers
on all 4 of my L4B's ever open in last 30 yrs.

...

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]

EG 1500w out/.63 = 2380 w input. 2380 x 1.22 =2904 va. 2904
Va/120 v = 24.2 AMPS !! Ur 120 v line is gonna SAG way b4 the
15 A breaker pops open.. with it's rinky dink 14 ga cu wire.

In
which case, you may as well run a 240V line in the 1st place...
unless u are talking about 600 w pep out on ssb.

RICH SEZ... no, 1500 pep. Resonant-choke filter DC supplies are

wonderful until you have to lift the sucker.

#### Resonant-choke filters, imo... are the most useless bloody
things ever devised.... and don't tell me 50 kw Broadcast
staion's use em.. they don't.... only exception would be if only
single phase power is the only thing available.

### What's wonderful would be 60 hz, 3 phase power like
208/360/400/480 v.... and a 3 phase Dahl plate xfmr... with a 6 x
leg diode stack... and a small-medium C input filter. Then it's
no ripple, [ripple is 6 x F on 3 phase] and superb regulation..
and no ripple on harmonics of 6 x F either. I think the
German's have the right idea all along.



RICH SEZ... A $1 MOV would have prevented the problem.

### Mov's have also burned down many homes too. The newer ones

have internal fuses in em. We alarm all our coffee mug size MOV's
at work... on commercial AC power entrances.. or on the low V side
of vault xfmr's. They are all external fused MOV's. A relay
between output of fuse and input of MOV is norm on. When fuse
pops.. relay drops out... alarm comes on. Thye newer Joslyn
MOV's have 1 microsecond response time.

RICH SEZ...An ordinary 12vDC relay's coil can produce 400v

when

the EM field collapses.

### so what ?

RICH SEZ...ignore 400v?

### read the entire post b4 commenting Rich..... just stick a MOV
across it... end of problem. .... or a rvs connected diode.


### a 48 vdc relay's coil will easily produce 1100V back
emf.... hence the MOV... or bye bye whatever is connected to the
coil.

later... Jim VE7RF