I have done some modifications to the shematic, so i have uploaded an
revided shematic.

I can't see the reason for floating the B-, to mesure the current i
would just add an 0.1 ohm resistor between the PSU's - tab and ground.
It sould be easy to mesure the current over that? or is it somting I
have missed?

I also have to order an transformer, since there are just 2 producers
of small transformers, i would have to order an 600V and use an
voltage doubler. I could get an 700VA transformer realy cheap, but is
it enoug? I've read that SSB only has an dutty of about 20%.

73 de Thomas.

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

Hello Thomas,

A couple of suggestions for your amplifier...

First, I would float the B- to make metering of plate and grid current
readily available to you. It takes no more than two resistors and a few
diodes to protect the metering to make this big improvement.

Second, I would suggest that you do not do T/R keying of the bias the
way that is shown on your schematic. That method is similar to the
Clipperton L and a few others. The flaw is that during the

transition of

the contacts the cathode will rise to near full anode potential and

when

you make contact with your bias circuit, you are hitting it with a very
high voltage at that moment. A simple cure for it without changing the
circuit entirely, and this applies to the Clipperton L as well, is to
place a jumper across the wiper and the normally closed contact of the
keying relay. That will keep the cutoff resistor in the circuit all the
time and prevent the cathode voltage from soaring. I would also place a
fuse in series with your bias circuit rated at just over your maximum
expected plate current. Also, a Metal Oxide Varistor or an NE-2 neon
bulb in parallel with the bias circuit will help protect it against
transient voltages. You may want to increase the value of the cutoff
resistor to about 20K to minimize the current in standby.

73, Tony W4ZT

The best way to measure a transformer gut temp is measure the winding resistance cold then hot and determine the real temperature rise by the copper constant. I think it is about .4%/degreeC. wa1gfz

R L Measures wrote:

All,

I hate to say that some dumb a$$ deleted almost everything I had
written except some corrections about the windings. I'd about bet they
were the one who wrote the screwed up stuff I had to correct. The guy
who edited it wrote he thought only 5-6 people might find it helpful.
Now, the page is about worthless but just to describe what a
transformer is. All the useful formulae are now gone. It's a shame I
didn't save it all as there was about 16 hours work in that. I did
leave the a$$hole a scaving responce and asked a question wanting to
know if they want people to learn or not. I think most in the
discussion are audiophiles who don't know one end from the other.

Best,

Will

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

All,

I finally did finish all I was going to do on Wikipedia about power
transformers. I found I also had to edit a few stubs and others. The
definition of Oersted was completely screwed and they had it tagged
for a re-write which I did the complete thing, and it's now correct.

I

had to correct the one on Gilberts too. They're still may be more,

and

if any of you were to catch these, please let me know.

I hope any who use this will find it helpful as it now has the most
info on the web about them. I do still hope a few here might add to
the RF transformer parts. Anyone can edit these by the way, and you
don't have to join anything.

Thanks,

Will

On Sep 26, 2006, at 5:02 PM, pentalab wrote:

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

RICH SEZ.. SSB has a duty cycle of less than 20%, so it's quite

different than RTTY.

### Dream On.... unless you chopped all the audio off below
350 hz..... or the plate current meter ballistics are out to
lunch.

During an ahhhhhhhh, I see about 1/3 of A0 anode current. If one transmits half the time, that's a duty-cycle of 1/6.

### Average plate current on SSB is about 1/2 that of the
dead cxr condition.

... closer to 1/3

### see above.

Average power output [not pep] is only
aprx 1/5 th the pep output of the amp.

### Next step is... we will try and meausre the heat on the
outer core with a Fluke 62 mini IR thermometer. Of
course... the heat deep inside the core will always be way
more.

Resin potting helps dissipate heat from deep in the core.

I have loads of air blown across it anyway.... and
reg is not too bad.

### I'm convinced 2 ga wire from main panel to HV supply

[and internal wiring] is not big enough !

RICH SEZ .. The Plywood Box amplifier was 100' from the breaker

box. It did 14k out pep and the wire was #4 Cu.

### #4 is too puny...esp 100' away. Heck that amounts to a
200' loop !! 4 ga CU won't handle 400+ A on peaks...
without a big v drop.... esp with 200' of loop resistance....
never mind ur small ga aluminium drop wires coming into the
house.. on top of that.

#### The next question is/was gonna be.... how was ur HV
regulation... with a dead cxr ???? [static] and also on ssb
[dynamic] ??? You can't even run a dead cxr.... with just
your 40 A breaker. You need a bare minimum of a 100 A
breaker.

### What's a fairly precise way to measure peak AC current
[under load] from the 200 A main panel ????

A 1-milliohm resistor in series with a calibrated oscilloscope to
measure the V-drop across it. The Plywood Box drew so much peak
current that the 240v wires could be heard vibrating in the attic
when I used a 30pps pulser to tune the sucker up. Also, at night,
the neighbor's porch-light blinked.

#### A 1 milliohm resistor... inserted in one leg of the 240 v
line that will handle 400 + A is gonna be a trick.

It's just a matter of execution.

Since we
know the exact length of the cable.... and it's exact dc
resistance... perhaps measuring the V drop end to end will
work?? ....

That would work. With a C-filter, for every ampere indicated, expect 10 amperes peak.

or perhaps measuring the peak v across the 240v
line.... using the peak max/min function on a fluke 87 [1 msec
snap shots] .... or my scope might work... and trigger off
the 'lows' in the acv ??

### A fwb gives better reg than a doubler... for the same size
caps.

Sure, but with the required size caps for a FWD, the % regulation is pretty much the same.

That 50 ohm glitch R we have in the B+ doesn't help
matter's any.... I lose 150 vdc right there.

... which is not noticeable at the Rx end. Originally, the Plywood Box
amplifier stupidly had a 25w glitch resistor -- most definitely a blunderous mistake.

Later..... Jim VE7RF







Yahoo! Groups Links

R L MEASURES, AG6K. 805-386-3734
r@...

All,

I finally did finish all I was going to do on Wikipedia about power
transformers. I found I also had to edit a few stubs and others. The
definition of Oersted was completely screwed and they had it tagged
for a re-write which I did the complete thing, and it's now correct. I
had to correct the one on Gilberts too. They're still may be more, and
if any of you were to catch these, please let me know.

I hope any who use this will find it helpful as it now has the most
info on the web about them. I do still hope a few here might add to
the RF transformer parts. Anyone can edit these by the way, and you
don't have to join anything.

Thanks,

Will

Jim,

I forgot to add, the calculations about voltage arcing I'm thinking of
are for only up to say 3 kVA in size. When you get on up in size, the
volts per turn, and per layer can raise due to the turns per volt
dropping. After 3 kVA, I'm not sure what they would equal up to be.
What I generally figure on these is about 2500 Vac at 3 kVA max. That
will give a 3500 Vdc OCV from a cap input.

Now you take a big one like your speaking of with 6 kV and the size it
is in kVA, the volts per turn, and per layer could be high. A big
transformer could get up to like 1/4 turn per volt or more, and at say
6000 Vac, there would be 4 or more volts per turn. What the worry
would be is arcing between the layers of turns. At say 250 turns,
you'd have 1000 volts per layer. Of course then you thicken up the
paper between layers and the wire insulation. I think you can see
where this is all going, the bigger in size in kVA with HV, the worse
off you are. Dahl could have been telling you about them instead of
smaller ones like 3 kVA and under.

Best,

Will

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

### someone listed on 'amp's.. think it was Johm Lyles... about
15 x diff xfmr makers in the USA. Someone got a cheap

quote

from 'magcapengineering' xfmrs.... about $100.00 less than the
Dahl.... then we he got it.... found that the DC secondary
resistance was 65 ohms !! [ 5-10 ohms is more like it.]

Use

a large C input filter... and the V reg sucked... the high peak
currents will cook the cheaper xfmr's. Rich claims the

Dahl's

will do about 4 x their rating on ssb.

No, the one in mention was Hal Mandel W4HBM. He had Dahl design a
transformer for him, and I can't remember if it was a anode or a
heater, but in two tries, Dahl got it wrong, both transformers went
poof for the rated load. I'm not sure, but afterwards, He got his
money back, and I think had the same transformer company in Kentucky
wind one that worked perfectly right from the box. The windings from
Dahl were wound with too small a wire both times if I recall. I
remember helping him troubleshoot it on amps, and the first thing I
said was the transformer wasn't right, and he found that the case
after checking it.

### Hope it's not Hammond. Hammond makes superb stuff....
however.. they don't have a clue as to how to build Hypersil
anything... just standard EI stuff. Hammomnd thinks the way to
build a plate xfmr is to center tap it. All their plate xfmrs

were

known as 'high reactance types'... all had center taps... and all
were made for tube rectifiers... and choke input.

No, they're not Hammond, they're a large company named MCI that
specializes in all types.

Hipersil is only a trademark held by Westinghouse which means high
permeability silicon steel. Hipersil's equivelants are M-6 in EI
cores, Hypertran, and Microsil. Microsil is used by Magnetic Metals.
Hypertran is Armco Steels (AK Steel) brand name for the steel. It is

a

cold rolled, grain oriented steel with a silicon content of around

3-

1/2%. Westinghouse actually sold out years ago on the steel used in
the manufacturer. One can build an EI core with M-6 that weighs just
15% more than a C-core. The only savings of the C-core would be the
rounded over corners in weight.

### Dahl and some engineers do it themselves. IF u just take

his

standard 45-65-127-253-440 lb cores.... and specify the sec taps

u

want... they always turn out great. The primarys are all wound
the same with the +10 0 -10.... 208....240 set up.

How can they select so many voltages for different amps with one

core

when the whole design considers the incoming / outgoing voltages and
currents to figure the core size? My guess was, when Hal and I

spoke,

that Dahl was taking a few cores and trying to make them work in a
bunch of other designs. You can end up finding out that after it's
started, the size wire you wan't wont fit in the window, or there's
not enough room for the number of turns, and then drop it down to

make

it fit. That's not good engineering practice, and the efficiency
wouldn't be good over it. I noticed myself that Dahl only uses a few
sizes of C-cores, and used the same ones in many different amp-brand
replacements. They're all listed in his Ham catalog on their

website.

There's probably 1000+ different stock C-core sizes available from
Magnetic Metals.

### Primary KVA = DC input x 1.22 That allows 11% for

power

factor... and 10% for core losses. His CCS ratings are

based

on a 50 deg C temp rise over ambient. I have seen several.

..

almost all vault transformers where the temp rise spec is sky
high... typ as much as 155 deg C.[over ambient] Why they

run

em so hot is beyond me. Power co's do the same thing

with

pole pigs... they run em hot. Ever wonder how a 50 KVA xfmr

can run 16 x homes...all with "200 A" service ?? There is
hardly any oil in em either.... the oil is just to transfer

heat

to the outside case [I suspect the cases are aluminium..never
seen rust on em]... and keep moisture out during storage.

A transformer running into a full wave bridge, with capacitor input,
needs about 1.6 to 1.8 times more rms current than the DC supply
current for the load. Most HV supplies require about 1.6 as 1.8 is

if

regulators are used afterwards. That has a lot to do with

transformer

failures I think when one orders them. See Hammond and Thordarson
transformer engineering portions of their websites, and a number of
others that show the same formulas. You can get by with a little

less

for SSB only operation as the book "Reference Data for Radio
Engineers" gives 1.45 times the DC current.

Ref:

These days, they're using met-glass which has a high perm, with a
higher flux density than Hipersil, plus they're immersed in oil.

Once

a pole pig is out of the oil, it's kva rating drops drastically. The
heat being carried away is the reason why they can be ran where
they're at. Without oil, at the same load, the wire would cook. Some
air cooled types can be pretty ran hot, at about 115 deg C, and up

to

17 kilogaiis flux density if a high-temp wire is used. Though the
magnetizing current rises rapidly above 15 kg and the losses really

go

up. If one used formvar or polyimide coated wire at those
temperatures, the transformer would smoke in no time.

### How do u propose to get 3 kva output.... with only 1.5

kva

input ??? U need loads of square/rectangular wire to wind
em.... no round wire is used in any dahl's...other wise u end up
with too many air gaps between turns....and more chance of
corona.

When I say 3 kVA or 1.5 kVA input, I mean the power of the amps

there

for. I will simply supply a 3 kVA transformer. The customer needs to
figure the size they need by the math, or have me to do it for them.

Naw, round wire has been used for years and years with no problems.
It's more like he uses square because that's all he wants to stock

for

certain sizes. Square wire will arc over too if the insulation used
isn't correct. The insulation thickness in mils, and type is what
determines if it will arc between turns, but here's the kicker,
there's no where near the full voltage between turns, nor between
layers. Matter of fact, there's no where near the voltage between
turns or the layers to puncture standard insulation. If it was,

either

he had over 1kv per layer at the least, or between turns, and that
just simply can't be the case. At one tun per volt, if we had 5000V,
and 5000 turns, that's 1 volt per turn. We'd probably have at least

10

layers or more, but at 10 layers, that's 500 volts per layer. I

doubt

one could get 500 turns in a layer, most likely 20 layers or more
total. The thing is, the larger the core, the turns per volt drops,
and at 1 turn per volt, that equals about 1 kVA. If he said that the
wires insulation has to match the full output voltage, he needs some
more schooling, or he's yanking your chain.

### Back in the 'old days' pumping dahl's with silicone
varnish glop was an option.... and several of the ones that

didn't

pay for the option....and stored em in damp locations... had em
short out, etc. Corona is bad news.

I agree, if they're going to be where it's damp, it should be dunked
in varnish. Actually, the only ones I never did varnish was the ones
in school as they had to be re-wound again by another student.

I'd be interested in these other xfmr builder's specs.

Ten-Tecs' supplier is;

MCI Limited:

Others;

Galaxy Transformer:

and

Ed Dennis, Heritage Transformer:

Heritage Transformer Co, Inc.
13483 Litchfield Rd.
Eastview, KY 42732.
270-862-9877.
e-mail hertiran@...

I don't have a URL for them anymore, and a search didn't show a
website. They used to have one, maybe someone else knows it.

Later......Jim VE7RF

Best,

Will

### someone listed on 'amp's.. think it was Johm Lyles... about
15 x diff xfmr makers in the USA. Someone got a cheap quote
from 'magcapengineering' xfmrs.... about $100.00 less than the
Dahl.... then we he got it.... found that the DC secondary
resistance was 65 ohms !! [ 5-10 ohms is more like it.] Use
a large C input filter... and the V reg sucked... the high peak
currents will cook the cheaper xfmr's. Rich claims the Dahl's
will do about 4 x their rating on ssb.

No, the one in mention was Hal Mandel W4HBM. He had Dahl design a
transformer for him, and I can't remember if it was a anode or a
heater, but in two tries, Dahl got it wrong, both transformers went
poof for the rated load. I'm not sure, but afterwards, He got his
money back, and I think had the same transformer company in Kentucky
wind one that worked perfectly right from the box. The windings from
Dahl were wound with too small a wire both times if I recall. I
remember helping him troubleshoot it on amps, and the first thing I
said was the transformer wasn't right, and he found that the case
after checking it.

### Hope it's not Hammond. Hammond makes superb stuff....
however.. they don't have a clue as to how to build Hypersil
anything... just standard EI stuff. Hammomnd thinks the way to
build a plate xfmr is to center tap it. All their plate xfmrs were
known as 'high reactance types'... all had center taps... and all
were made for tube rectifiers... and choke input.

No, they're not Hammond, they're a large company named MCI that
specializes in all types.

Hipersil is only a trademark held by Westinghouse which means high
permeability silicon steel. Hipersil's equivelants are M-6 in EI
cores, Hypertran, and Microsil. Microsil is used by Magnetic Metals.
Hypertran is Armco Steels (AK Steel) brand name for the steel. It is a
cold rolled, grain oriented steel with a silicon content of around 3-
1/2%. Westinghouse actually sold out years ago on the steel used in
the manufacturer. One can build an EI core with M-6 that weighs just
15% more than a C-core. The only savings of the C-core would be the
rounded over corners in weight.

### Dahl and some engineers do it themselves. IF u just take his
standard 45-65-127-253-440 lb cores.... and specify the sec taps u
want... they always turn out great. The primarys are all wound
the same with the +10 0 -10.... 208....240 set up.

How can they select so many voltages for different amps with one core
when the whole design considers the incoming / outgoing voltages and
currents to figure the core size? My guess was, when Hal and I spoke,
that Dahl was taking a few cores and trying to make them work in a
bunch of other designs. You can end up finding out that after it's
started, the size wire you wan't wont fit in the window, or there's
not enough room for the number of turns, and then drop it down to make
it fit. That's not good engineering practice, and the efficiency
wouldn't be good over it. I noticed myself that Dahl only uses a few
sizes of C-cores, and used the same ones in many different amp-brand
replacements. They're all listed in his Ham catalog on their website.
There's probably 1000+ different stock C-core sizes available from
Magnetic Metals.

### Primary KVA = DC input x 1.22 That allows 11% for power
factor... and 10% for core losses. His CCS ratings are based
on a 50 deg C temp rise over ambient. I have seen several...
almost all vault transformers where the temp rise spec is sky
high... typ as much as 155 deg C.[over ambient] Why they run
em so hot is beyond me. Power co's do the same thing with
pole pigs... they run em hot. Ever wonder how a 50 KVA xfmr
can run 16 x homes...all with "200 A" service ?? There is
hardly any oil in em either.... the oil is just to transfer heat
to the outside case [I suspect the cases are aluminium..never
seen rust on em]... and keep moisture out during storage.

A transformer running into a full wave bridge, with capacitor input,
needs about 1.6 to 1.8 times more rms current than the DC supply
current for the load. Most HV supplies require about 1.6 as 1.8 is if
regulators are used afterwards. That has a lot to do with transformer
failures I think when one orders them. See Hammond and Thordarson
transformer engineering portions of their websites, and a number of
others that show the same formulas. You can get by with a little less
for SSB only operation as the book "Reference Data for Radio
Engineers" gives 1.45 times the DC current.

Ref:

These days, they're using met-glass which has a high perm, with a
higher flux density than Hipersil, plus they're immersed in oil. Once
a pole pig is out of the oil, it's kva rating drops drastically. The
heat being carried away is the reason why they can be ran where
they're at. Without oil, at the same load, the wire would cook. Some
air cooled types can be pretty ran hot, at about 115 deg C, and up to
17 kilogaiis flux density if a high-temp wire is used. Though the
magnetizing current rises rapidly above 15 kg and the losses really go
up. If one used formvar or polyimide coated wire at those
temperatures, the transformer would smoke in no time.

### How do u propose to get 3 kva output.... with only 1.5 kva
input ??? U need loads of square/rectangular wire to wind
em.... no round wire is used in any dahl's...other wise u end up
with too many air gaps between turns....and more chance of
corona.

When I say 3 kVA or 1.5 kVA input, I mean the power of the amps there
for. I will simply supply a 3 kVA transformer. The customer needs to
figure the size they need by the math, or have me to do it for them.

Naw, round wire has been used for years and years with no problems.
It's more like he uses square because that's all he wants to stock for
certain sizes. Square wire will arc over too if the insulation used
isn't correct. The insulation thickness in mils, and type is what
determines if it will arc between turns, but here's the kicker,
there's no where near the full voltage between turns, nor between
layers. Matter of fact, there's no where near the voltage between
turns or the layers to puncture standard insulation. If it was, either
he had over 1kv per layer at the least, or between turns, and that
just simply can't be the case. At one tun per volt, if we had 5000V,
and 5000 turns, that's 1 volt per turn. We'd probably have at least 10
layers or more, but at 10 layers, that's 500 volts per layer. I doubt
one could get 500 turns in a layer, most likely 20 layers or more
total. The thing is, the larger the core, the turns per volt drops,
and at 1 turn per volt, that equals about 1 kVA. If he said that the
wires insulation has to match the full output voltage, he needs some
more schooling, or he's yanking your chain.

### Back in the 'old days' pumping dahl's with silicone
varnish glop was an option.... and several of the ones that didn't
pay for the option....and stored em in damp locations... had em
short out, etc. Corona is bad news.

I agree, if they're going to be where it's damp, it should be dunked
in varnish. Actually, the only ones I never did varnish was the ones
in school as they had to be re-wound again by another student.

I'd be interested in these other xfmr builder's specs.

Ten-Tecs' supplier is;

MCI Limited:

Others;

Galaxy Transformer:

and

Ed Dennis, Heritage Transformer:

Heritage Transformer Co, Inc.
13483 Litchfield Rd.
Eastview, KY 42732.
270-862-9877.
e-mail hertiran@...

I don't have a URL for them anymore, and a search didn't show a
website. They used to have one, maybe someone else knows it.

Later......Jim VE7RF

Best,

Will

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

RICH SEZ.. SSB has a duty cycle of less than 20%, so it's quite

different than RTTY.

### Dream On.... unless you chopped all the audio off below
350 hz..... or the plate current meter ballistics are out to
lunch.

### Average plate current on SSB is about 1/2 that of the
dead cxr condition.

... closer to 1/3

### see above.

Average power output [not pep] is only
aprx 1/5 th the pep output of the amp.

### Next step is... we will try and meausre the heat on the
outer core with a Fluke 62 mini IR thermometer. Of
course... the heat deep inside the core will always be way
more.

Resin potting helps dissipate heat from deep in the core.

I have loads of air blown across it anyway.... and
reg is not too bad.

### I'm convinced 2 ga wire from main panel to HV supply

[and internal wiring] is not big enough !

RICH SEZ .. The Plywood Box amplifier was 100' from the breaker

box. It did 14k out pep and the wire was #4 Cu.

### #4 is too puny...esp 100' away. Heck that amounts to a
200' loop !! 4 ga CU won't handle 400+ A on peaks...
without a big v drop.... esp with 200' of loop resistance....
never mind ur small ga aluminium drop wires coming into the
house.. on top of that.

#### The next question is/was gonna be.... how was ur HV
regulation... with a dead cxr ???? [static] and also on ssb
[dynamic] ??? You can't even run a dead cxr.... with just
your 40 A breaker. You need a bare minimum of a 100 A
breaker.

### What's a fairly precise way to measure peak AC current
[under load] from the 200 A main panel ????

A 1-milliohm resistor in series with a calibrated oscilloscope to
measure the V-drop across it. The Plywood Box drew so much peak
current that the 240v wires could be heard vibrating in the attic
when I used a 30pps pulser to tune the sucker up. Also, at night,

the neighbor's porch-light blinked.

#### A 1 milliohm resistor... inserted in one leg of the 240 v
line that will handle 400 + A is gonna be a trick. Since we
know the exact length of the cable.... and it's exact dc
resistance... perhaps measuring the V drop end to end will
work?? .... or perhaps measuring the peak v across the 240v
line.... using the peak max/min function on a fluke 87 [1 msec
snap shots] .... or my scope might work... and trigger off
the 'lows' in the acv ??

### A fwb gives better reg than a doubler... for the same size
caps. That 50 ohm glitch R we have in the B+ doesn't help
matter's any.... I lose 150 vdc right there.

Later..... Jim VE7RF

Hello Thomas,

A couple of suggestions for your amplifier...

First, I would float the B- to make metering of plate and grid current readily available to you. It takes no more than two resistors and a few diodes to protect the metering to make this big improvement.

Second, I would suggest that you do not do T/R keying of the bias the way that is shown on your schematic. That method is similar to the Clipperton L and a few others. The flaw is that during the transition of the contacts the cathode will rise to near full anode potential and when you make contact with your bias circuit, you are hitting it with a very high voltage at that moment. A simple cure for it without changing the circuit entirely, and this applies to the Clipperton L as well, is to place a jumper across the wiper and the normally closed contact of the keying relay. That will keep the cutoff resistor in the circuit all the time and prevent the cathode voltage from soaring. I would also place a fuse in series with your bias circuit rated at just over your maximum expected plate current. Also, a Metal Oxide Varistor or an NE-2 neon bulb in parallel with the bias circuit will help protect it against transient voltages. You may want to increase the value of the cutoff resistor to about 20K to minimize the current in standby.

73, Tony W4ZT




la3pna wrote:

On Sep 26, 2006, at 1:15 PM, pentalab wrote:

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

For the price they charge for the suckers, they out to gold plate

them too!

Don't be blinded by all the Dahl-Hipersil hoopla, there's a few

other very good companies who make some gem dandy transformers, and
for a way better price. I'll dig up a couple of address for you
later today.

### someone listed on 'amp's.. think it was Johm Lyles... about
15 x diff xfmr makers in the USA. Someone got a cheap quote
from 'magcapengineering' xfmrs.... about $100.00 less than the
Dahl.... then we he got it.... found that the DC secondary
resistance was 65 ohms !! [ 5-10 ohms is more like it.] Use
a large C input filter... and the V reg sucked... the high peak
currents will cook the cheaper xfmr's. Rich claims the Dahl's
will do about 4 x their rating on ssb.

A Dahl 4500va-rated transformer will do 14k RF out pep.

...

R L MEASURES, AG6K. 805-386-3734
r@...

Yeah, that's correct.
If you compare them then you would see that I have copyed part's of it.
I think that the Ameritron amp. is running the tubes a bit to hard.
An other thing i have done is that i have added an adjustabile bias and
not an string of diodes like ameritron has done.

73 de Thomas

tir, 26,.09.2006 kl. 17.09 -0400, skrev KR4DA:

--
Best Regards/MVH
Thomas S Knutsen
LA3PNA

On Sep 26, 2006, at 1:49 PM, pentalab wrote:

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

Not so amazing for those who realize that Mu goes down as anode-

I increases.
### agreed.



### Those 253 lb Dahl's are a bargain.....

A Dahl 253-pounder is a serious waste of greenbacks for 15k out

on SSB because one of his 68-pounders will do 15k out.

As I see it, a 253-pounder is more than enough for a

8910/4cx15,000J.

### I find that hard to believe !... but I may well be wrong.
With 6800 Vdc @ 3A = 20.4 Kw dc input. Primary KVA = 20.4 x
1.22 = 24.88 Kva.

SSB has a duty cycle of less than 20%, so it's quite different than RTTY.

### A Dahl 253 lb'er has a 5200/5400 sec.... rated at just
3 A CCS. [ Sec = 16 KVA CCS.... primary = 17.6kva ]

### So we are running it on SSB at aprx 24.88 /17.6 = 1.41 or
41 % over it's rating.... on ssb. So far so good.

### Average plate current on SSB is about 1/2 that of the
dead cxr condition.

... closer to 1/3

Average power output [not pep] is only
aprx 1/5 th the pep output of the amp.

### Next step is... we will try and meausre the heat on the
outer core with a Fluke 62 mini IR thermometer. Of
course... the heat deep inside the core will always be way
more.

Resin potting helps dissipate heat from deep in the core.

I have loads of air blown across it anyway.... and
reg is not too bad.

### I'm convinced 2 ga wire from main panel to HV supply [and
internal wiring] is not big enough !

The Plywood Box amplifier was 100' from the breaker box. It did 14k out pep and the wire was #4 Cu.

Either 3 x 000 CU or just
locating the HV supply next to the main 200 A panel would be the
ticket... then longer runs of DC HV to the RF deck.

### What's a fairly precise way to measure peak AC current
[under load] from the 200 A main panel ????

A 1-milliohm resistor in series with a calibrated oscilloscope to measure the V-drop across it. The Plywood Box drew so much peak current that the 240v wires could be heard vibrating in the attic when I used a 30pps pulser to tune the sucker up. Also, at night, the neighbor's porch-light blinked.

### spending $7.5 K to $10 k on a new Alpha /Acom is an even
greater waste of greenbacks imo.

Agreed, Jim, and the educational fun value is zero.

I put several L4B's nose to
tail... on different bands! [the L4b's will handle 2kw on bypass..
with flat bypss swr]. Heck I could afford to blow 1/2 of em
up... and still have a few left over. A pair of sb-220's would
also work... just tune em up on diff bands...... plus u got a back
up amp... if one blows up.... or u got one of em offline.. in the
shop.. being modified.

Jim VE7RF

...


R L MEASURES, AG6K. 805-386-3734
r@...

Yahoo! Groups Links

R L MEASURES, AG6K. 805-386-3734
r@...

You dont need matched tubes -- just put some resistance in the cathodes and they self match -- rich knows more about how to get the right values of resistance -- im still learning
Steven Grant W4IIV


At 04:54 PM 9/26/2006, la3pna wrote:

开云体育

Very good English
Anyway I had a Ameratron (sp) AL 811H
This was a 4 tube 811 amp.
Try researching it for CKT diagrams and? ideas.
I think the schematic is on the Ameratron web page.

la3pna wrote:

Hi group.
I'm Thomas, La3PNA and I'm in the progress of starting to build an HF
amplifier with 4 811A tubes. I'm gone to use 4 of them because, I got
the tubes, sockets and Plate caps for 4. I have drawn an shematic that
can be found in the folder "LA3PNA 811 amplifier" in the Files section.

I have drawn it as an one band unit, mostly since the rotary switches
in Eagle are stupid drawn, I would like to make it work at all nine
HF bands, from 160M to 10M.

I wrote an e-mail to R L MEASURES and got an nice answer on some of my
questions. He recomended to use 5 of 811, but i think that it is a bit
hard to get 5 matched tubes?

I have found out that one 811 tube has an impedance of 300 ohm's so 4
of them should give an inpedance of 75 ohms. Is this correct? found
the data in an old ARRL handbook, on an article on an one tube amp.

Hope that some of you have time to take an look at my design and
please let me know if there is any errors.

73 de Thomas LA3PNA
PS: sorry for my bad English.

-- 
de KR4DA Bob Middleburg, FL
HK0/KR4DA J79DA FG/KR4DA

Hi group.
I'm Thomas, La3PNA and I'm in the progress of starting to build an HF
amplifier with 4 811A tubes. I'm gone to use 4 of them because, I got
the tubes, sockets and Plate caps for 4. I have drawn an shematic that
can be found in the folder "LA3PNA 811 amplifier" in the Files section.

I have drawn it as an one band unit, mostly since the rotary switches
in Eagle are stupid drawn, I would like to make it work at all nine
HF bands, from 160M to 10M.

I wrote an e-mail to R L MEASURES and got an nice answer on some of my
questions. He recomended to use 5 of 811, but i think that it is a bit
hard to get 5 matched tubes?

I have found out that one 811 tube has an impedance of 300 ohm's so 4
of them should give an inpedance of 75 ohms. Is this correct? found
the data in an old ARRL handbook, on an article on an one tube amp.

Hope that some of you have time to take an look at my design and
please let me know if there is any errors.

73 de Thomas LA3PNA
PS: sorry for my bad English.

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

Not so amazing for those who realize that Mu goes down as anode-

I increases.
### agreed.



### Those 253 lb Dahl's are a bargain.....

A Dahl 253-pounder is a serious waste of greenbacks for 15k out

on SSB because one of his 68-pounders will do 15k out.

As I see it, a 253-pounder is more than enough for a

8910/4cx15,000J.

### I find that hard to believe !... but I may well be wrong.
With 6800 Vdc @ 3A = 20.4 Kw dc input. Primary KVA = 20.4 x
1.22 = 24.88 Kva.

### A Dahl 253 lb'er has a 5200/5400 sec.... rated at just
3 A CCS. [ Sec = 16 KVA CCS.... primary = 17.6kva ]

### So we are running it on SSB at aprx 24.88 /17.6 = 1.41 or
41 % over it's rating.... on ssb. So far so good.

### Average plate current on SSB is about 1/2 that of the
dead cxr condition. Average power output [not pep] is only
aprx 1/5 th the pep output of the amp.

### Next step is... we will try and meausre the heat on the
outer core with a Fluke 62 mini IR thermometer. Of
course... the heat deep inside the core will always be way
more. I have loads of air blown across it anyway.... and
reg is not too bad.

### I'm convinced 2 ga wire from main panel to HV supply [and
internal wiring] is not big enough ! Either 3 x 000 CU or just
locating the HV supply next to the main 200 A panel would be the
ticket... then longer runs of DC HV to the RF deck.

### What's a fairly precise way to measure peak AC current
[under load] from the 200 A main panel ????

### spending $7.5 K to $10 k on a new Alpha /Acom is an even
greater waste of greenbacks imo. I put several L4B's nose to
tail... on different bands! [the L4b's will handle 2kw on bypass..
with flat bypss swr]. Heck I could afford to blow 1/2 of em
up... and still have a few left over. A pair of sb-220's would
also work... just tune em up on diff bands...... plus u got a back
up amp... if one blows up.... or u got one of em offline.. in the
shop.. being modified.

Jim VE7RF

...


R L MEASURES, AG6K. 805-386-3734
r@...

Hello,

This email message is a notification to let you know that
a file has been uploaded to the Files area of the ham_amplifiers
group.

File : /LA3PNA 811 Amplifier/811.jpg
Uploaded by : la3pna <snknutse@...>
Description : First shematic.

You can access this file at the URL:


To learn more about file sharing for your group, please visit:


Regards,

la3pna <snknutse@...>

--- In ham_amplifiers@..., "craxd" <craxd1@...> wrote:

For the price they charge for the suckers, they out to gold plate

them too!

Don't be blinded by all the Dahl-Hipersil hoopla, there's a few

other very good companies who make some gem dandy transformers, and
for a way better price. I'll dig up a couple of address for you
later today.

### someone listed on 'amp's.. think it was Johm Lyles... about
15 x diff xfmr makers in the USA. Someone got a cheap quote
from 'magcapengineering' xfmrs.... about $100.00 less than the
Dahl.... then we he got it.... found that the DC secondary
resistance was 65 ohms !! [ 5-10 ohms is more like it.] Use
a large C input filter... and the V reg sucked... the high peak
currents will cook the cheaper xfmr's. Rich claims the Dahl's
will do about 4 x their rating on ssb.

One in Canada who makes the ones for Ten-Tec.

### Hope it's not Hammond. Hammond makes superb stuff....
however.. they don't have a clue as to how to build Hypersil
anything... just standard EI stuff. Hammomnd thinks the way to
build a plate xfmr is to center tap it. All their plate xfmrs were
known as 'high reactance types'... all had center taps... and all
were made for tube rectifiers... and choke input.

## Hammond does make superb EI custom fil xfmrs. Also their
7.5v-21 A and 5v-30A are dirt cheap. [$40.00 US funds]... run
barely luke warm... but only come with 115 V primarys.



There's one in Kentucky, that does a really good job, but I can't
remember the name without looking it up. Another is Galaxy
Transformer who makes some big ones for a builder down in Florida.

If you get a chance, ask Hal Mandel about a dealing he has with

Dahl on a custom transformer. It made me wonder who they had there

designing them.

### Dahl and some engineers do it themselves. IF u just take his
standard 45-65-127-253-440 lb cores.... and specify the sec taps u
want... they always turn out great. The primarys are all wound
the same with the +10 0 -10.... 208....240 set up.

### Primary KVA = DC input x 1.22 That allows 11% for power
factor... and 10% for core losses. His CCS ratings are based
on a 50 deg C temp rise over ambient. I have seen several...
almost all vault transformers where the temp rise spec is sky
high... typ as much as 155 deg C.[over ambient] Why they run
em so hot is beyond me. Power co's do the same thing with
pole pigs... they run em hot. Ever wonder how a 50 KVA xfmr
can run 16 x homes...all with "200 A" service ?? There is
hardly any oil in em either.... the oil is just to transfer heat
to the outside case [I suspect the cases are aluminium..never
seen rust on em]... and keep moisture out during storage.

If things work out, I'll be doing a few C-cores up to 3 kVA output

(1.5 kVA input) for a few friends. I just got an e-mail back from
the core supplier today.

### How do u propose to get 3 kva output.... with only 1.5 kva
input ??? U need loads of square/rectangular wire to wind
em.... no round wire is used in any dahl's...other wise u end up
with too many air gaps between turns....and more chance of
corona.

### Back in the 'old days' pumping dahl's with silicone
varnish glop was an option.... and several of the ones that didn't
pay for the option....and stored em in damp locations... had em
short out, etc. Corona is bad news.

I'd be interested in these other xfmr builder's specs.

Later......Jim VE7RF

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

Rich Sez... Jim A Q of 15 on 10m is quite common.

With a Q of only 8, a Pi-network's transformation ratio isn't

all

that great.

### The way around that problem on 10/12m is this.....[a] Use a
10-1000 pf ceranic vac cap for 160-10m.... the other cap is a 12-
500 pf jennings... also good.... IE: use a low min C cap.

### [b] either insert .6 uh b4 the main pi-net.... OR just tap
into the masn tank coil.... at the .6uh point... with the tune
cap..... amounts to the same thing... and both work good.

### with a low 1000-1500 ohm plate load Z..... AND that .6 uh
coil in front of the pi-net...... the LC action of the anode
C and the .6 uh.... will transform the plate load Z DOWN a huge
amount..... which is what the PI-Net is then designed around....
and it's then happy.

## Using that procedure... you can get a Q of 10 pretty easy.

## an almost identical procedure is to design the 10m tank coil
in the normal fashion.... then CENTER TAP it with the vac tune
cap. Broadcast stations use this trick all the time.

## A Q of 8-10 is plenty imo. A Q of 7-8 is kinda low... and
makes the load control very broad. Ten tec uses a real low Q on
160m on their 2x 3-500Z amp.... simply cuz their tune cap is only
375 pf to start with... so they added more tank coil to
compensate... makes the loading control real broad.... and hard
to hit a peak on the wattmeter.

### I use a Q of 10 [new calc method... which equates to 8
calculating it the old way]. THEN...it tunes up real
smoothly... plus..... if u wanna run less suds.... by backing off
the drive.... and retweaking.... the plate load Z will go UP....
and PI net Q goes UP.... and it still works good... since the Q
has now gone up from 10 to 12 [new method of calculating Q]

### You run a Q of 15+ on 10m.... you will cook tank
coils ! What's worse is when trying to re-use the 10m tap on 12
m.....Q goes up even more.... and u will vapourize stuff.

### IMO... to get these tubes to run right on 10/12m.... it's
almost better to build a mono band 10/12m RF deck..... an re-use
the existing HV supply + fil supply, etc.

Jim VE7RF

On Sep 26, 2006, at 11:25 AM, pentalab wrote:

Lemme get this straight

To calculate Grid diss..... we take RMS cathode V x DC grid
current ???

RMS cathode-grid potential multiplied by - meter indicated - DC grid current is an okay approximation. The actual dissipation calculation involves integral calculus.

If that's the case..... that equates to 1.2 KW of drive to
a 3CX-6000A7..... to just max out the grid [rated at 225 W
CCS].

Drive And degree of loading determine grid dissipation.

On ssb..... I don't think it's a problem anyway. We tried it
last night..... 1200 w of drive = 15 kw output... no sweat....
no fuss ..no muss.... and clean too.

Amazing.. how the gain keeps going down,as drive increases.

Not so amazing for those who realize that Mu goes down as anode-I increases.

With 100 w of drive = 3 kw out. 200 w of drive = 5 kw out.
800 w of drive = 11.5 kw out.

You just gotta love all these surplus vac caps, cheap copper
tubing from home depot, surplus 7-16 Din's, surplus vac relay's
etc. Those 253 lb Dahl's are a bargain.....

A Dahl 253-pounder is a serious waste of greenbacks for 15k out on SSB because one of his 68-pounders will do 15k out.
As I see it, a 253-pounder is more than enough for a 8910/4cx15,000J.

...


R L MEASURES, AG6K. 805-386-3734
r@...