ORIGINAL MESSAGE:

On Mon, 20 Nov 2006 20:51:00 -0000, "n2mg" <n2mg@...>
wrote:

The rate is 20x the current subscription rate - has been for at least
30 years.

I paid $135 (20 x $6.75) in 1975-ish just before the rate went to
$8.25/year or $165/life.

Mike N2MG

------------ REPLY FOLLOWS ------------

I've always found it odd that the rate is not based on life
expectancy. Someone 60 should pay the same as someone 20?

Weird.

Bill, W6WRT

Here's a question. Can one still be an ARRL life member ??

The last I heard, yes.

As in.... pay XXX dollars. Im talking about today....now.

### My buddy is an ARRL lifer. I'm sure it cost him something
bizzare like a few hundred bucks... back in 1976. Thought it
like $500.00 to $750.00

The rate is 20x the current subscription rate - has been for at least
30 years.

I paid $135 (20 x $6.75) in 1975-ish just before the rate went to
$8.25/year or $165/life.

Mike N2MG

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

RICH SEZ...Perhaps it might be a good idea to read the specs on

the 250v-rated MOV's, Jim.

### I did. And the 250 v rating is for a 250 V max rms CCS
condition.

RICH SEZ... The critical thing is: at what potential does the unit

begin to conduct current.

Depending on who makes a MOV.... clamp V is always
way higher than that.... which is why old books always said to

use twice the PIV needed for a FWB. These days it's triple the PIV

needed [at least for commercial recifier assys].

RICH SEZ...In the 8169 / Plywood Box #2 amplifier, I deliberately

used a HV rectifier safety factor of 33% based on my measurement
of the actual PIV. There has never been a failure.

### A few good spikes down the power line and the diodes WILL
fail....esp with only 33% more PIV....and little or no additional
protection. A broadcast engineer buddy of mine told me one of the
site's he looks after had a really good spike come down the
line.... took out everything... including diodes, and the tube
itself. The spike managed to get past ALL the MOV's as well.
That's a disaster for a Broadcast station. Smoked the standby 2nd
TX as well.

### Imo... 6A10 [1 kv- 6A CCS - 400 A surge ] diodes are
so cheap anyway.... I don't see any reason not to use at least 200-
300% more PIV. 300% IS STANDARD these days.. in the commercial
world.

### with a safety factor of only 33%.... the diodes would fry...
LONG before any MOV cliped the spikes off.

### MOV's are just a series of "grains" inside. The series
grains will start to short out with successive hits from
transients, spikes, surges, etc. The actual V rating of the MOV
will slowly start to go down. That's why 130V rated MOV's
are normally used. A 250 v rated Mov is cutting it too fine
for folks whose line V can reach 247-250 V.

RICH SEZ....You seem to assume that conduction for a 250v rating

begins at 251 x 1.14 volts. It does not.

### I already know that. Rich..... take a 0-277 v variac..... and
a 250 V rated MOV..... and apply >250 V on it for 1 hr...then
tell us what happens !

### Check out Joslyn's website in the USA. They are the number
one maker of commercial MOV assemblies for use in commercial /
industrial environments. You won't see any 250 v rated MOV's
used on any 240 V circuits.

RICH SEZ....chortle. My guess is that Joslyn has yet to try

measuring the zener- v of a 250V rated MOV.

### These guys wrote the book on MOV's. Latest ones they make are
the fastest yet... 1 nano second. The run o mill MOV's from
Mouser etc.. are not fast. Selenium transient suppressor's are
faster than MOV's.... but won't take the high joules. Some schemes
use Selenium suppressor's in parallel with MOV's. The selenium's
clip the super fast portion of the tansient... the MOV clips the
slower portion/higher energy portion.

### The whole point here is... with successive hits... the V rating
of any MOV starts to drop... another reason we fuse em.

### Most newer homes in Florida have giant MOV's located just below
the main 200 A service panel... connected to main Buss... via a
20-60A breaker.

### I was convinced that the huge C filter in any HV supply
would absorb any spikes/transients... they don't. The PIV across
the non conducting diodes is still sky high also.

## Spikes/transients will make it's way past huge lead acid
batteries on any UPS power supplies as well as standard -54v
telco batteries. [24 x 2400 AH cells in series = 1 string... as
many as 10 strings in parallel..each cell is >500 lbs. The -54
vdc then typ feeds >100 x DC to DC supplies... fused on input
side... and the 5 vdc @ 40A output side uses a breaker. When u
see 40 A output breakers popped open after a major event
[extremely rare] makes you wonder how a spike got through layer
after layer of protection.

### Rich... you hook ur stuff up any way you want. Me... I play it
safe. I have seen way too much damage done in the last 30 yrs, to
come home and then wire stuff up mickey mouse style. Diodes are
cheap, MOV's are cheap. Correct V sized MOV's are just as cheap as
incorrectly sized MOV's. Fast fuses are just as cheap as slow
ones. Glitch R's are cheap... and ditto with fast HV fuses.
Putting a 2nd HV fuse between plate xfmr sec and input of FWB has
saved our bacon twice now.

### Adding some electronic plate/grid overcurrent protection is a
good idea too. On W7DS's triode board... it also has provisions
for monitoring the HV as well. When HV drops too low... amp kicks
offline... so no way to drive it with no/reduced plate V.

I'm not even gonna argue anymore about this topic... I said my
piece.

later.... Jim VE7RF

...

later

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

So I went ahead and put some whiskers, er, feelers out for info on
fixed vacuum capacitors in high voltage service.

Info Item 1:

Glass fixed vacuum capacitors are used in DC + RF applications
as voltage blockers. They need to be operated in a vertical
geometry so the electrodes are at top and bottom, and they should be
i an airstream to cool them as they will warm up with KVaR flowing.

Info Item 2:

Glass and ceramic fixed vacuum caps should be three times the voltage
that they will see, which corresponds to the positive peak RF voltage
plus the unloaded DC voltage.

The reason I get involved with this thread is that I was presented a
lovely Jennings 2,000pF glass fixed vacuum cap rated at 20KV and at
75 amperes @ 32MHz.

The presenter of this item said to me that builders will oftentimes
physically warm up the fixed glass vacuum caps for a short while upon
actual install day to "condition" the devices, and that shortly
thereafter, with normal service their internal heating will continue
the conditioning process.

This same source of information also told me that since many glass
fixed vacuum caps are symmetrical, the RF engineers involved with the
equipment maintenance will periodically turn them upside down and run
them that way until turning them over again.

You guys are killing me.

BOB DD

On Nov 20, 2006, at 5:11 AM, Harold Mandel wrote:

At the potential required to effect a change the resulting amperage might be
deleterious.

Why not e-mail Jennings to see their fix?

This could be interesting, Hal.

Hal
W4HBM

-----Original Message-----
From: ham_amplifiers@... [mailto:ham_amplifiers@...]
On Behalf Of Mike Sawyer
Sent: Monday, November 20, 2006 7:57 AM
To: ham_amplifiers@...
Subject: Re: [ham_amplifiers] Re: AC HiPot tester question

Now, let me ask a question of social and political importance: Is it
possible to 'remove' the whisker by introducing and hi(er)-voltage to the
vacuum cap? The reason I ask is that this was practice used to recover
Ni-Cad batteries. A whisker would develop between anode and cathode and a
charge capacitor, several times the actual output of the cell would be
placed across it, (reversed polarity if memory serves me), and physically
'burn' the offending whisker.
Mod-U-Lator,
Mike(y)
W3SLK
----- Original Message -----
From: craxd <mailto:craxd@...>
To: ham_amplifiers@...<mailto:ham_amplifiers@...>
Sent: Monday, November 20, 2006 12:29 AM
Subject: [ham_amplifiers] Re: AC HiPot tester question

It sounds to me that Jennings wants things two different ways. First
they say don't momentarily test a vacuum cap with DC, but it's okay
to put one in service as a DC blocking cap, de-rated or not. From
everything I've ever read, the whisker problem is caused over time,
not in one minute of use. A DC blocker cap could be in an amp for a
lifetime. That's a good sales gimmick to sell hipots though. I've
never seen that warning either by Comet, or by any of the Russian
manufactured caps. If the cause is over the copper being too soft
used for the plate cups, it ought to be changed to a hard copper or
an alloy to stop it. I can see soft copper for the bellows, but not
the plate cups.

Thank God Rich and I didn't question the Jennings engineers on the
other list as we would have been sent another e-mail by the unknown
admin chastizing us for ever questioning these professionals with
published papers, etc....

Best,

Will

--- In ham_amplifiers@...
<mailto:ham_amplifiers%40yahoogroups.com> , R L Measures <r@...> wrote:

On Nov 19, 2006, at 2:59 AM, pentalab wrote:

--- In ham_amplifiers@...

<mailto:ham_amplifiers%40yahoogroups.com> , R L Measures <r@...> wrote:

...
RICH SEZ.... A 20kV rated C to block 7000V DC sounds like over-

engineering since the actual AC potential across the blocker is
minimal.

#### Rich... Jenning's engineers tell me when using either fixed
glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of the
FIXED vac cap has to be a MINIMUM of 3 X No load plate V......
other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

So why does the statement I quoted in the Jennings catalog on p.4
about DC operation state otherwise?

### Ur gonna get "whisker's" anyway in plate block service for
a fixed vac cap.... so the 20 kv cap... will actually be over
time... a lot lower than 20 kv. IF u Hi-pot test a fixed vac cap
that has been used for plate block service.... u will see it no
longer hi pot tests to 20+ kv any more.

### other than 11m ops... I never see fixed vac caps used as plate
blockers.

I do, Jim. Even 500pF is plenty for a DC blocker at 1.8MHz (XC =

190-

ohms) in typical amplifiers since RL is in the kilo-ohms range.

11m ops don't need much C for 11m... 100-250 pf max
is what they typ use. Their requirements are for a plate block cap
that handles LOTS of RF... esp for 4x20's, etc.

Tom Rauch apparently knows a Ham who mistakenly used a 100pF DC
blocker in a homebrew amplifier. The amplifier produced the

expected

output from 1.8 to 28 MHz. Sometime later, when a friend was

being

shown the amplifier, he noticed that there were only twp zeros

after

the 1 on the blocker cap. When a 1000pF cap was substituted for

the

100pF cap, the output did not increase although the tuning changed
slightly on the 1.8MHz band.
...
R L Measures, AG6K, 805.386.3734
r@... <mailto:r%40somis.org> , rlm@..., www.somis.org

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

On Nov 20, 2006, at 4:56 AM, Mike Sawyer wrote:

Now, let me ask a question of social and political importance: Is it possible to 'remove' the whisker by introducing and hi(er)- voltage to the vacuum cap?

I have done this, Mike, but one must be careful not to overdo the procedure.
To begin with, connect a 20M to 100M HV-rated resistor in series with the high-potential tester to seriously limit current. . . When a vacuum-C has been in storage for a long time, it is not unusual to find that as applied potential rises, it will "tink" (indicating a flashover) briefly discharging the cap several kV below its rated peak-V. This does not mean that the cap is feculent. By slowing raising the applied potential until the cap tinks, Cu whiskers can be burned off, raising the cap's piv each time the procedure is repeated. However, at some point in the tinling procedure, the piv will begin to DEcrease -- i. e., the procedure becomes destructive rather than constructive. IOW, this is yet another case where mo' is Not always mo' betta. It is my opinion the 3 or 4 tinks is about the limit.
cheerz

...
Mike(y)
W3SLK
----- Original Message -----
From: craxd
To: ham_amplifiers@...
Sent: Monday, November 20, 2006 12:29 AM
Subject: [ham_amplifiers] Re: AC HiPot tester question

It sounds to me that Jennings wants things two different ways. First
they say don't momentarily test a vacuum cap with DC, but it's okay
to put one in service as a DC blocking cap, de-rated or not. From
everything I've ever read, the whisker problem is caused over time,
not in one minute of use. A DC blocker cap could be in an amp for a
lifetime. That's a good sales gimmick to sell hipots though. I've
never seen that warning either by Comet, or by any of the Russian
manufactured caps. If the cause is over the copper being too soft
used for the plate cups, it ought to be changed to a hard copper or
an alloy to stop it. I can see soft copper for the bellows, but not
the plate cups.

Thank God Rich and I didn't question the Jennings engineers on the
other list as we would have been sent another e-mail by the unknown
admin chastizing us for ever questioning these professionals with
published papers, etc....

Best,

Will

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

On Nov 19, 2006, at 2:59 AM, pentalab wrote:

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

...
RICH SEZ.... A 20kV rated C to block 7000V DC sounds like over-

engineering since the actual AC potential across the blocker is
minimal.

#### Rich... Jenning's engineers tell me when using either fixed
glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of the
FIXED vac cap has to be a MINIMUM of 3 X No load plate V......
other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

So why does the statement I quoted in the Jennings catalog on p.4
about DC operation state otherwise?

### Ur gonna get "whisker's" anyway in plate block service for
a fixed vac cap.... so the 20 kv cap... will actually be over
time... a lot lower than 20 kv. IF u Hi-pot test a fixed vac cap
that has been used for plate block service.... u will see it no
longer hi pot tests to 20+ kv any more.

### other than 11m ops... I never see fixed vac caps used as plate
blockers.

I do, Jim. Even 500pF is plenty for a DC blocker at 1.8MHz (XC =

190-

ohms) in typical amplifiers since RL is in the kilo-ohms range.

11m ops don't need much C for 11m... 100-250 pf max
is what they typ use. Their requirements are for a plate block cap
that handles LOTS of RF... esp for 4x20's, etc.

Tom Rauch apparently knows a Ham who mistakenly used a 100pF DC
blocker in a homebrew amplifier. The amplifier produced the

expected

output from 1.8 to 28 MHz. Sometime later, when a friend was

being

shown the amplifier, he noticed that there were only twp zeros

after

the 1 on the blocker cap. When a 1000pF cap was substituted for

the

100pF cap, the output did not increase although the tuning changed
slightly on the 1.8MHz band.
...
R L Measures, AG6K, 805.386.3734
r@..., rlm@..., www.somis.org

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

On Nov 19, 2006, at 10:04 PM, pentalab wrote:

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

On Nov 19, 2006, at 7:32 AM, pentalab wrote:

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

Which MOV's do you use and where do you get them?

### From Mouser... Digi key has em as well... aprx 2" tall x
1/2" thick x 2.75" wide base. Those are the 130 v units.
The closest ones for the 240 V service are 250 V rated. IMO..
250 V rated Mov's are cutting it too close.

RICH SEZ...Perhaps it might be a good idea to read the specs on

the 250v-rated MOV's, Jim.

### I did. And the 250 v rating is for a 250 V max rms CCS
condition.

The critical thing is: at what potential does the unit begin to conduct current.

Depending on who makes a MOV.... clamp V is always
way higher than that.... which is why old books always said to use
twice the PIV needed for a FWB. These days it's triple the PIV
needed [at least for commercial recifier assys].

In the 8169 / Plywood Box #2 amplifier, I deliberately used a HV rectifier safety factor of 33% based on my measurement of the actual PIV. There has never been a failure.

### MOV's are just a series of "grains" inside. The series
grains will start to short out with successive hits from
transients, spikes, surges, etc. The actual V rating of the MOV
will slowly start to go down. That's why 130V rated MOV's
are normally used. A 250 v rated Mov is cutting it too fine
for folks whose line V can reach 247-250 V.

You seem to assume that conduction for a 250v rating begins at 251 x 1.14 volts. It does not.

A few too many
hits on the MOV.. and it's continuous V rating will drop to the
point where it will conduct.... and short out. UNLESS it's
fused.... it's gonna burn up... or explode.

Be there, done that. 1000J is pretty nasty.

Way too many house
fires caused by MOV's as is.

### Check out Joslyn's website in the USA. They are the number
one maker of commercial MOV assemblies for use in commercial /
industrial environments. You won't see any 250 v rated MOV's
used on any 240 V circuits.

chortle. My guess is that Joslyn has yet to try measuring the zener- v of a 250V rated MOV.

...

later

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

On Nov 20, 2006, at 2:34 AM, pentalab wrote:

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

The point here is.... by oversizing the HV fuse.... the load is
then transfered to the 100 A breaker in the 240 v main 200 A
panel.... which of course didn't blow open...... instead the
glitch R's fried themselves... !
You need well over 100 A to open a 100 A panel breaker.

RICH SEZ... Which is why I used a 40A thermal-magnetic breaker for

the 8170 amp.

#### Which will be on the ragged edge of opening...

Precisely, but so far never has.

since we
already determined you are sucking 110 A on keydown cxr.

We? YOU assumed that I was stupid enough to do this.

Would
be kind of nice to run a dead cxr..for at least 3-7 seconds.. just
to take steady state plate/grid current readings. You can't do
that with a 40 A breaker. With a 2 x pole [50 A per pole]
breaker.. with it's poles wired in parallel.. and tie bar removed...
and 2 x such assys' used... one per hot leg... u can then have all
4 poles activated for dead cxr stuff... and kick one pole off
per breaker... for ragged edge ssb operation. IE: toggle from
a 100 A breaker... down to a 50 A breaker.

BTW... that Dahl A-540 hypersil C core 253 lb plate xfmr I
have... has a .01 ohm primary.

RICH SEZ...How did you measure this?

### with a B+K 875-B... also used a HP DVM [very expensive
box... just back from the cal lab, reads some extra zero's] The
Fluke 87 will only read to 1/10ths of an ohm. Also, low
resistance readings can be even more accurately done using mho's/
siemens. .01 ohm = 100 mho's. .001 ohm = 1000 mho's .0001
ohm = 10,000 mho's. I have gear that will read higher than
10,000 mho's. In all cases... the sec was shorted, when
taking pri readings... and vice versa.. when taking sec readings.

A 1 significant digit reading does not imply great gobs of accuracy. I measure low resistances by putting 1.000A through them and measuring the mV drop with my Fluke DMM.

RICH SEZ... Thus, my guess is that the short-circuit current
would be c. 470A-rms. The secondary current under a short would
be 470A / 21.6 = 21.7A-rms.

Jim: Why would a HV fuse in the secondary be better than a

250V fuse in the primary?

### Cuz a 3 A sandfilled fuse.. with 8 kv/50 ohm glitch = 160
A of fault current. 160A of fault current has a tendency to
blow a HV sand fuse in < 2 msecs.

The glitch R begins to limit fault current in no time, and it's peak current that does the damage.

...

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

On Nov 20, 2006, at 12:17 AM, pentalab wrote:

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

...

RICH SEZ.... A 20kV rated C to block 7000V DC sounds like

over-

engineering since the actual AC potential across the blocker

is

minimal.

####### The AC potential across the cap has nothing to do with
it.

#### Rich... Jenning's engineers tell me when using either

fixed

glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of

the

FIXED vac cap has to be a MINIMUM of 3 X No load plate

V......

other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

RICH SEZ... So why does the statement I quoted in the Jennings

catalog on p.4 about DC operation state otherwise?

#### Dunno. Eimac sez the same thing, de -rate vac caps to
1/3 for plate block use !

RICH SEZ.... I did not read this in any Eimac literature,

#### You don't have friends at Eimac... like me.

.. and Tom Rauch?

RICH SEZ...and it does not make good sense

### sure it does. Apply continuous DC HV to a vac cap.,. and
eventually... DCV rating.. due to whisker growth...

I have seen whisker growth in vacuum caps that have been in long-term storage. However, when such caps are high-potted, after a few tinks the stickers apparently burn off and the piv capability returns.

DROPS...hence size the caps DC HV rating at least 3 x the plate
supply's unloaded v to start with. That's what Jenning's sez...

So why does the Jennings Vacuum and Gas Capacitor catalog say on p.6:
"DC -- Vacuum capacitors should not be operated in DC applications above the peak RF working voltage."
"DC Plus RF -- For DC plus RF applications, the sum of the DC plus the peak RF voltage should not exceed the peak RF working voltage."

that's what Eimac sez... that's what 11m ops say... or else it's
flash kablamo time ..... end of story.

hardly. Page 6 still has you by the short hair.

RICH SEZ...since the prima facie consideration for a DC blocker is
the current rating at 29MHz - since at 10m, the DC blocker
typically carries c. 90% of the tank's RF circulating current.

#### "prima facie consideration" ? Are you OJ's lawyer too ?

Johnny's dead, I'm not quite there yet - despite the plenitude of fervent prayers of Mormons, Muslims, Jehovah's Witnesses, SDAs, and Roman Catholics. .

- prima facie - adv.
1. At first sight; before closer inspection: They had, prima facie, a legitimate complaint.

### yes... 10m and above is the worst case scenario for a plate
block cap.... that's what I have been saying all along.

The 11m ops also highly agree. The
11m ops tell me if they try and use a 16 kv test rated fixed vac
cap with 10.5 kv dc on it..... it will eventually arc.

RICH SEZ... Probably true since Jennings advises that 60% of the DC

test V is the max WV when using DC + RF.

### what ? Jenning's sez the max AC RF working V is 60%
of the DC test V.

Page 6. The Vacuum and Gas Capacitor Catalog:
"RF Working Voltage is the maximum RF voltage that can be applied to the capacitor without affecting its ability to withstand instantaneous overloads, It is generally 60% of the Peak Test Voltage rating. ..."

They are asuming and also implying you have
employed a plate block cap already.

Staying below the peak RF WV ability is the prime concern no matter the application.

What they are refering too is
using a vac cap as a C1/C2 tune/load cap... or using a vac cap to
pad a tune/load cap. In any event... the AC voltage across a
plate block cap is so low... u can ignore it.... UNLESS you insist
on using really small value plate block caps... then you end up
with high AC voltages across em.... as in plate current X Xc
of plate block cap.

Agreed

### for 10.5 kv dc no load... you want at least a 25-30 kv test v
rated fixed vac cap.

According to page 6,

"DC Plus RF -- For DC plus RF applications, the sum of the DC plus the peak RF voltage should not exceed the peak RF working voltage."

Example -- A 1000pF DC blocker, using an 8281 running at 10.5kV with a typical tank Q, would have c. 20A of tank circulating current flowing through the DC blocker at 29MHz, so there would be c. 105volts drop across it. Thus, according to p.6, a capacitor with 10,500v plus 105v = 10,605 / 0.60, so a 17,500 DC-test V or higher unit should be used. However, amplifiers with 10,500v anode supplies are not all that common in Hamdom. Also, 10,500v is getting pretty close to the land of x-rays.

...

RICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at

1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the
kilo-ohmS range.

#### No way. 500pf = 176 ohms of XC.

RICH SEZ.... The rule of thumb is a 5 to one ratio for a coupling

reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or
higher RL should be okay.

### No way. Where did u cook up this 5 to one ratio ??? Not
in any of my engineering books. Any big metal tube operating
with a 880 ohm plate load Z... is gonna be sucking loads of plate
current. 4-5 A typ. 5 A x 176 ohms XC = 880 vac You just
lost it right there!

#### 100 pf = 884 ohms XC [1.8 mhz] gimme a break !

RICH SEZ... With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would

probably work okay if the Tune-C could tune it out.

#### Now it gets even worse ! 5 A x 884 ohms = 4400 vac dropped
across the plate block cap..

Where did the 1.5A come from?

...

### a 100 pf plate block doorknob cap wouldn't last 30 seconds

in a 3x3

RICH SEZ... Why would the capacitor dissipate heat?

#### lemme see. With say 2.5 A of plate current at 5 kv under
load... and on 29 mhz... current through the 100 pf plate block
cap = 32 A.

How did you calculate this, Jim?

A HT-57 100 pf cap is only rated at 13.7 A @
30 mhz [with 13.7 A, the 100 pf cap's temp is 55-65 deg C...149
deg F..... and well over 100+ deg C.. with 32 A flowing through
it] Use multiple metal tubes on 10m or bigger single metal
tubes with lots of anode to chassis C..... look out.

### with 32 A through a cap rated for 13.7 A = meltdown. [5.5 x
more heat. 32/13.7= 2.34 2.34 squared = 5.5 more trbl] Don't
gimme this nonsense about pulse tuning and SSB being a 15% duty
cycle. The correct component here is 6 x 500 pf HT-57's... or
3-4 x 200pf HT-57's. I use 6 x 500 pf HT-57's.... then it
will have low XC on 160m too.

Later... Jim VE7RF

to be continued ...


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

At the potential required to effect a change the resulting amperage might be
deleterious.

Why not e-mail Jennings to see their fix?

Hal
W4HBM

开云体育

On Nov 19, 2006, at 10:28 PM, pentalab wrote:

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

RICH SEZ... I did the calculations for the 8170 amplifier with

Ohm's Law. The calc. peak mains current was c. 300A. The
measured result was 1200v- pk into 50-ohms on SSB.

### 1200 V pk equates to 14,396 watts pep output into a 50 ohm
load..

Correct

..14,395.65 /.63 = 22,850 w dc input.

My guess is that the efficiency was closer to 60%.

Primary VA = 22,850
x 1.22 = 27,877 va 27,877 /240v = 116.155 A

Only if one assumes that the filter-C stores zero Joules in the 70%
interim between 30pps, 30% duty-cycle tuning pulses. .

.... not
including fil xfmr, blower etc. Peak current is aprx 375A
with big wire and a big C filter... every 8.3 msecs.

The mains ESR was measured at 0.079Ω, add 200' of #4 Cu. Xfmr pri. R
= 0.075Ω, sec R = 12Ω, and the turns ratio is 240/3000 = 12.5. I
came up c. 300A-pk - which could have been in the ballpark since my
wife could hear the wires vibrate in the attic when I tuned the
sucker up.

### Rich... tell us how you take a steady state plate meter
readings and grid current.

For designed-for-SSB amplifiers, I don't. The plate/anode current
meter is used only to adj. ZSAC. During speech, it probably indicated
c. 1/3 of the anode current, or perhaps 1.3 A. . . After adjusting
for zero grid-current and 0.5A of ZSAC, and tuning-loading for the
specified screen-current I was done with meter readings. The next
step was optional -- to measure peak-V into 50-ohms with an
oscilloscope and a HV multiplier probe.

.... with out blowing ur under rated 40 A
house breaker ???? IE: a dead cxr... for just 3-6
seconds... just long enough to measure grid/plate current + fil V,
loaded plate V, etc. Forget the fil v/ plate v...... focus on
just the plate + grid current.

With an amplifier that was designed for SSB-only, only a dead-head
would use a dead-carrier.

### If u just pulse tune it...and talk...fine... I do too. Unless
both ur plate/grid meter's are peak reading types.... I can't see
how it's done.

Easy: grid current is zero, ZSAC is whatever is specified, with a
30% duty-cycle tuning-pulser, multiply the screen-current reading by
3.3. For example, normal screen-current is 120ma, so when the meter
peaks at 36mA with the Tune-C control, the 8170 or 8171 is ready for
use.

### IMO.. the entire system should be configured to at least
handle a 4-7 second dead cxr.... without blowing breakers,
melting coax, frying tank coils etc.

To have been able to go on the A0 trip would have required a HV
transformer that weighed and cost triple, plus the added cost of 200'
of #2 Cu.
The total cost for the Plywood Box 8170 project was $1200, not
counting the 200' of #4 Cu for the 240v 50a outlet.

### For a 8170/8171.... I'd use a 100A breaker... and a bare min
of 2 ga wire... and considering the 300-400A peak current draw
every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless
of length.

For RTTY, this makes sense, but for SSB, it's greenbacks flushed down
the crapper.

### BTW... what's the CCS rating of the SB-220's plate
xfmr ??? I heard it was 1200 va.

It's not speced, Jim, but the core dimensions figure out to c. 550w.

Now Rich has stated it's only
600Va. I'm sure the smaller SB-200 is 600 va CCS.

### Will a SB-220 stock... in good condition, on low plate
V...be capable of delivering 600W CCS RTTY ???

I have no idea, Jim. Continuous broadcasting is something I have zero
interest in.

later

...

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

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

The point here is.... by oversizing the HV fuse.... the load is
then transfered to the 100 A breaker in the 240 v main 200 A
panel.... which of course didn't blow open...... instead the
glitch R's fried themselves... !
You need well over 100 A to open a 100 A panel breaker.

RICH SEZ... Which is why I used a 40A thermal-magnetic breaker for

the 8170 amp.

#### Which will be on the ragged edge of opening... since we
already determined you are sucking 110 A on keydown cxr. Would
be kind of nice to run a dead cxr..for at least 3-7 seconds.. just
to take steady state plate/grid current readings. You can't do
that with a 40 A breaker. With a 2 x pole [50 A per pole]
breaker.. with it's poles wired in parallel.. and tie bar removed...
and 2 x such assys' used... one per hot leg... u can then have all
4 poles activated for dead cxr stuff... and kick one pole off
per breaker... for ragged edge ssb operation. IE: toggle from
a 100 A breaker... down to a 50 A breaker.

BTW... that Dahl A-540 hypersil C core 253 lb plate xfmr I
have... has a .01 ohm primary.

RICH SEZ...How did you measure this?

### with a B+K 875-B... also used a HP DVM [very expensive
box... just back from the cal lab, reads some extra zero's] The
Fluke 87 will only read to 1/10ths of an ohm. Also, low
resistance readings can be even more accurately done using mho's/
siemens. .01 ohm = 100 mho's. .001 ohm = 1000 mho's .0001
ohm = 10,000 mho's. I have gear that will read higher than
10,000 mho's. In all cases... the sec was shorted, when
taking pri readings... and vice versa.. when taking sec readings.


RICH SEZ... Thus, my guess is that the short-circuit current
would be c. 470A-rms. The secondary current under a short would
be 470A / 21.6 = 21.7A-rms.

Jim: Why would a HV fuse in the secondary be better than a

250V fuse in the primary?

### Cuz a 3 A sandfilled fuse.. with 8 kv/50 ohm glitch = 160
A of fault current. 160A of fault current has a tendency to
blow a HV sand fuse in < 2 msecs. Fast 100 A fuses in the
primary would work... but with 470 A... would not open as fast.
Only 1 x HV fuse needed..... VS TWO x 100 A high speed fuses
in 240 v primary.

.... LOADS... as my buddy with the same 253 lb xfmr
just found out. 253 lb xfmr with a core good for 20 KVA
CCS with a 100 A slo breaker... vs lowly glitch R [wound with
nichrome wire no less] .... no contest.... glitch loses every
time........ unless a correct sized HV fuse is used !

RICH SEZ.... When a correct size HV fuse is used and a short is

applied, does the glitch R survive?

### sure. Doesn't even put a dent on the Glitch R. You can
crowbar the thing all day long.

#### We did find out where the HV arc was happening.... was
between OUTPUT of parasitic suppressor globar clip.. and the 20-
17-15m 1/2" tubing tank coil... bad arc. When driven... the
anode V rises to almost double [restored tank sine wave back
feeds through plate block caps to anode.. adds to the existing dc
HV.] Fix was to rotate the coil on it's axis a bit.

## Last time... the arcing was caused by LOOSE strap from C1
vac tune cap to 20-17-15 m tank coil. STRAP had flopped over a
bit.... and arc occured between parasitic suppressor coil and
this loose strap. Of course in both cases.. ALL the tank
components are at chassis grnd... including tune/load
caps/bandswitch/ both tank coils, etc.... due to the HB 45 uh 18
ga solenoid wound safety choke... wired between chassis and hot
side of vac LOAD cap. [45 uh choke wound on 1" diam solid Teflon
rod... bullet proof... also identical to the 45 uh RF choke used in
the 2 x piece plate choke set up 135/180 uh + 45 uh]

### This safety RF choke HAS to be rugged... no place for your
ARRL hand book 2.5 mh 30 ohm 36 ga.... pi wound assy. Those
things will blow into a million pieces when you try and stuff 160
A through em. They also have more than a tendency to blow up..
with NO HV fuse.... and also with no glitch R.... well... use ur
imagination... 8 kv / 1.4 ohms ESR from modern day lytics + plate
choke = 5700 A Actually.. it's not that bad... since the DC
resistance of any floozy RF safety choke will limit current...
then the choke explodes. A 45 uh 18 ga safety choke is
compact... and a snap to make. Drill + tap a 1/4-20 thread into
the base... and it's easy to mount. 2 x Transverse brass threads
terminate the 18 ga magnet wire.

Later... Jim VE7RF

later... Jim VE7RF

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

--- In ham_amplifiers@..., "Robert B. Bonner"
<rbonner@...> wrote:

Guys,

My first job out of my undergrad program was with a building

automation (energy) company. We installed PFC caps on buildings
all over the place.

For the Super Big guns that are running 100 AMP primarys with

three phase power supplies doing PFC will just make the power to
the primary smoother and your power company happier. I don't think
it is worth the expense for correction caps. Either way I would
install them on the amplifier not the building.

### On HV supplies with resonant choke filters.... they all have
a better power factor... compared to a simple C input filter.
When you increase the C in a C filter HC supply... the power
factor gets WORSE. Sounds to me like this 90 deg lag is not a
fixed thing... but vary's... depending on power factor itself...
IE: .8 pf vs .9pf vs .98pf

### Since a simple C input filter has a WORSE PF than a resonant
choke filter.... my electrician buddy is suggesting the huge C is
responsible for the worsening pf.... and NOT the XL of either
the pri/sec of the plate xfmr. If that's the case... Dahl is
probably right, he should know. Dahl is telling me on a large C
input filter, that you can't use PF correction caps on the pri
of the plate xfmr. It just makes the PF worse still... and
magnetizing current increases. Since the C filter on the output
side is responsable for the lousy PF on a C input filter... probably
what's needed is a choke.. or XL across the plate xfmr pri.... or
perhaps in series with the plate cfmr pri ??

### Even if it could be done... the load is not constant on the HV
supply... it's nil [except for magnetizing current and bleeder] on
RX.... and vary's on TX from ZSAC... to full bore. Any
compensation would probably have to be relay switched out on RX...
and optimized for an average load on TX... on ssb anyway.

BOB DD


WILL SEZ... I looked through about every book I have on

transformers and power supplies, and never found anything about
using a cap for power factor correction. There's plenty about using
a cap with an AC motor, but nothing about transformers. The
Standard Handbook For Electrical Engineers only show adding them to
motor circuits or circuits feeding motor loads. Nothing under the
transformer section.

### That's what I suspected. I don't see any PFC caps on SW
broadcast TX either... not at 1st glance anyway. None of them are
using C input filters I believe.... might be wrong. With 3 phase
HV... ripple is only 4.8 % b4 any filtering. A simple C input
filter would reduce the ripple to zip. However a resonant
choke would do the same thing.. and have a better power factor at
the same time. For 24/7 operation.. and huge power... any
savings would add up.

WILL SEZ... The only way to cut back on magnetizing current is to

use more iron in the core lowering its flux density. The more iron
for the same amount of turns, the current drops. I researched
magnetizing current in C-core Hipersil (or M-6) transformers some
time back, and seen they had a good bit more magnetizing current
than most EI cores using M-19 steel. The reason being is they run
Hipersil from 15 to 17 kilogauss. M-19 and M-22 are ran from 14 to
10 kilogauss. Over 15 kilogauss in Hipersil, the current really
shoots up. The way to cure this is to have a transformer wound with
the same number of turns, but with a larger core area in either a C-
core or an EI core. One would have to tell the winder to use a
lower flux density of say 12 to 10 kilogauss using a C-core with
Hipersil or M-6 for a low magnetizing current. M-19 for an EI core
may be a better choice if available as it will be a good bit
cheaper. The core loss isn't much greater than M-6 either.

### I'm gonna ask Dahl what kind of hypersil he uses. The 120
lb 10 kva hypersil pole pig I have has 1.9 A of magnetizing
current at all times. The 253 lb Dahl hypersil has only 1.6
A of magnetizing current [it's a 3 A CCS sec = 15.5 kva CCS] I
was expecting a LOT more magnetizing current from the 253 lb
xfmr. [esp since it's double the weight of my pole pig]. The
1.6 x 240v = 384 Va of magnetizing va is small... compared to the
4.5 A int load you can pull off the sec. Still.. that's 384-va
on RX all the time.

### BTW... it's 384 va... whether FWB/caps/bleeder connected...
OR disconnected.. makes no difference.... even when sucking 100
w of bleeder diss. Ditto with pole pig supply.

### Dahl tells me the A-540 core he uses on all the 253 lb'ers is
good for 20 KVA CCS. Once u get a sec over 4 kv... the CCS I
rating drops from 4 A... down to 3 A. At 7.5 kv sec... it's
then down to 2.5 A CCS. My xfmr [due to wire ga on sec] is
rated at 15.5 kva..... however the core itself is good for 20 kva.

later... Jim VE7RF

Best,

Will





Yahoo! Groups Links

craxd wrote:

The boards are okay I guess but there is nothing special about the current trips. All they do is sense a voltage drop across a resistor with higher current and trigger an opto-couplers LED with it. This is turn will open a circuit by a relay or transistor circuit.

What you say here is true, Will. Each individual circuit is simple. The major benefit to the boards is that you can buy one that has the circuits designed and ready to go. Not only that, but the trips are linked together to provide fault lines, both hard and soft, which can save more than just a little trouble fixing something. Ian and Paul both make good boards. My personal favorite is Paul's. He uses multi turn pots and the 26V supply is on board including the power transformer for it and the bias regulator circuit is there too. This not only eliminates the need for you to provide another supply but also provides the juice for the t/r and control relays as well. You can also implement as much or as little of it as you like.

Another thing I seen in one board is that they sample a little of the screen or bias voltage and put that into a regulator to get the control voltage for a relay, etc. That was done to keep from having another coil on the transformer for low voltage. However, you need one anyhow for the antenna relay, and others.

I haven't seen that.

I design my own as to me any of the boards I've seen are a little over-kill and over complicated for my taste. The more components placed in any circuit raises the likelyhood of failure in the future expotentially. I can make just as good of a regulator circuit with a few transistors and zener diodes. This for either a series pass or shunt regulator.
Best,
Will

<snip>
If you want cheap and easy, a simple design on proto board is fine for just the things you want. That's why I put together a simple bias board based on the same circuit commonly used with the TL431 reference to use as a retrofit bias board <>. Not everyone wants a complex system and not everyone appreciates the protection that you can have by using one of the control boards. It's just a personal choice and nice that we have those options today. My personal choice for home brew is to include the protection... Wouldn't build without it. For a retrofit, it usually isn't that practical or economical to do.

Besides the trip circuits used on the control boards there have been several older commercial amps like the B&W PT2500 that included a grid trip circuit. It isn't all that difficult to build and use.

I find the three lead regulators much more reliable than any series regulator built with a few transistors and zeners. They have over current protection and are so much simpler to use.


Regards, Tony

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

...

RICH SEZ.... A 20kV rated C to block 7000V DC sounds like

over-

engineering since the actual AC potential across the blocker

is

minimal.

####### The AC potential across the cap has nothing to do with
it.

#### Rich... Jenning's engineers tell me when using either

fixed

glass/ceramic vac cap as a PLATE Blocker.... MIN V rating of

the

FIXED vac cap has to be a MINIMUM of 3 X No load plate

V......

other wise u get "whisker's" growing on the OFC plates on the
cap..... which will REDUCE the caps V rating.

RICH SEZ... So why does the statement I quoted in the Jennings

catalog on p.4 about DC operation state otherwise?

#### Dunno. Eimac sez the same thing, de -rate vac caps to
1/3 for plate block use !

RICH SEZ.... I did not read this in any Eimac literature,

#### You don't have friends at Eimac... like me.




RICH SEZ...and it does not make good sense

### sure it does. Apply continuous DC HV to a vac cap.,. and
eventually... DCV rating.. due to whisker growth...
DROPS...hence size the caps DC HV rating at least 3 x the plate
supply's unloaded v to start with. That's what Jenning's sez...
that's what Eimac sez... that's what 11m ops say... or else it's
flash kablamo time ..... end of story.






RICH SEZ...since the prima facie consideration for a DC blocker is
the current rating at 29MHz - since at 10m, the DC blocker
typically carries c. 90% of the tank's RF circulating current.

#### "prima facie consideration" ? Are you OJ's lawyer too ?

### yes... 10m and above is the worst case scenario for a plate
block cap.... that's what I have been saying all along.

The 11m ops also highly agree. The
11m ops tell me if they try and use a 16 kv test rated fixed vac
cap with 10.5 kv dc on it..... it will eventually arc.

RICH SEZ... Probably true since Jennings advises that 60% of the DC

test V is the max WV when using DC + RF.

### what ? Jenning's sez the max AC RF working V is 60%
of the DC test V. They are asuming and also implying you have
employed a plate block cap already. What they are refering too is
using a vac cap as a C1/C2 tune/load cap... or using a vac cap to
pad a tune/load cap. In any event... the AC voltage across a
plate block cap is so low... u can ignore it.... UNLESS you insist
on using really small value plate block caps... then you end up
with high AC voltages across em.... as in plate current X Xc
of plate block cap.

### for 10.5 kv dc no load... you want at least a 25-30 kv test v
rated fixed vac cap.

...

RICH SEZ... I do, Jim. Even 500pF is plenty for a DC blocker at

1.8MHz (XC = 190- ohms) in typical amplifiers since RL is in the
kilo-ohmS range.

#### No way. 500pf = 176 ohms of XC.

RICH SEZ.... The rule of thumb is a 5 to one ratio for a coupling

reactance. 176- ohms of XC and a RL of 176-ohms x 5 = 880-ohms or
higher RL should be okay.

### No way. Where did u cook up this 5 to one ratio ??? Not
in any of my engineering books. Any big metal tube operating
with a 880 ohm plate load Z... is gonna be sucking loads of plate
current. 4-5 A typ. 5 A x 176 ohms XC = 880 vac You just
lost it right there!

#### 100 pf = 884 ohms XC [1.8 mhz] gimme a break !

RICH SEZ... With a pair of 3-500Zs, RL is c. 2k, so 884-ohms would

probably work okay if the Tune-C could tune it out.

#### Now it gets even worse ! 5 A x 884 ohms = 4400 vac dropped
across the plate block cap........ not to mention the 45-63A of RF
flowing through it ..on 10m ! [using a 100 pf plate block cap +
big metal tubes]

### Stick a single 100 pf HT-50/58 cap in any 1500W amp....
run it at 1500 W RTTY/FM on 1.8 mhz for say 20 mins.... and
let us know what happens.

RICH SEZ... > no

#### It would vaporize.... that's why.

### a 100 pf plate block doorknob cap wouldn't last 30 seconds

in a 3x3

RICH SEZ... Why would the capacitor dissipate heat?

#### lemme see. With say 2.5 A of plate current at 5 kv under
load... and on 29 mhz... current through the 100 pf plate block
cap = 32 A. A HT-57 100 pf cap is only rated at 13.7 A @
30 mhz [with 13.7 A, the 100 pf cap's temp is 55-65 deg C...149
deg F..... and well over 100+ deg C.. with 32 A flowing through
it] Use multiple metal tubes on 10m or bigger single metal
tubes with lots of anode to chassis C..... look out.

### with 32 A through a cap rated for 13.7 A = meltdown. [5.5 x
more heat. 32/13.7= 2.34 2.34 squared = 5.5 more trbl] Don't
gimme this nonsense about pulse tuning and SSB being a 15% duty
cycle. The correct component here is 6 x 500 pf HT-57's... or
3-4 x 200pf HT-57's. I use 6 x 500 pf HT-57's.... then it
will have low XC on 160m too.

Later... Jim VE7RF

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

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

RICH SEZ... I did the calculations for the 8170 amplifier with

Ohm's Law. The calc. peak mains current was c. 300A. The
measured result was 1200v- pk into 50-ohms on SSB.

### 1200 V pk equates to 14,396 watts pep output into a 50 ohm
load....14,395.65 /.63 = 22,850 w dc input. Primary VA = 22,850
x 1.22 = 27,877 va 27,877 /240v = 116.155 A .... not
including fil xfmr, blower etc. Peak current is aprx 375A
with big wire and a big C filter... every 8.3 msecs.

### Rich... tell us how you take a steady state plate and grid
current meter readings..... with out blowing ur under rated 40 A
house breaker ???? IE: a dead cxr... for just 3-6
seconds... just long enough to measure grid/plate current + fil V,
loaded plate V, etc. Forget the fil v/ plate v...... focus on
just the plate + grid current.

### If u just pulse tune it...and talk...fine... I do too. Unless
both ur plate/grid meter's are peak reading types.... I can't see
how it's done.

### IMO.. the entire system should be configured to at least
handle a 4-7 second dead cxr.... without blowing breakers,
melting coax, frying tank coils etc.

### For a 8170/8171.... I'd use a 100A breaker... and a bare min
of 2 ga wire... and considering the 300-400A peak current draw
every 8.3 msec..... 3 x 000 CU is the real ticket.... regardless
of length.

### BTW... what's the CCS rating of the SB-220's plate
xfmr ??? I heard it was 1200 va. Now Rich has stated it's only
600Va. I'm sure the smaller SB-200 is 600 va CCS.

### Will a SB-220 stock... in good condition, on low plate
V...be capable of delivering 600W CCS RTTY ??? If so...
the plate xfmr would have to be a 1200 va unit.

Later... Jim VE7RF

#### 3/000 CU from main 200A panel to HV supply is what's
really needed. Snip a few strands to make it fit the 100 A
breaker at EACH end.

later... Jim VE7RF

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

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

On Nov 19, 2006, at 7:32 AM, pentalab wrote:

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

Which MOV's do you use and where do you get them?

### From Mouser... Digi key has em as well... aprx 2" tall x
1/2" thick x 2.75" wide base. Those are the 130 v units.
The closest ones for the 240 V service are 250 V rated. IMO..
250 V rated Mov's are cutting it too close.

RICH SEZ...Perhaps it might be a good idea to read the specs on

the 250v-rated MOV's, Jim.

### I did. And the 250 v rating is for a 250 V max rms CCS
condition. Depending on who makes a MOV.... clamp V is always
way higher than that.... which is why old books always said to use
twice the PIV needed for a FWB. These days it's triple the PIV
needed [at least for commercial recifier assys].

### MOV's are just a series of "grains" inside. The series
grains will start to short out with successive hits from
transients, spikes, surges, etc. The actual V rating of the MOV
will slowly start to go down. That's why 130V rated MOV's
are normally used. A 250 v rated Mov is cutting it too fine
for folks whose line V can reach 247-250 V. A few too many
hits on the MOV.. and it's continuous V rating will drop to the
point where it will conduct.... and short out. UNLESS it's
fused.... it's gonna burn up... or explode. Way too many house
fires caused by MOV's as is.

### Check out Joslyn's website in the USA. They are the number
one maker of commercial MOV assemblies for use in commercial /
industrial environments. You won't see any 250 v rated MOV's
used on any 240 V circuits. Their's come in several
configs.... like 130/135 v MOV's from each hot leg to neutral....
and or... 275 V rated Movs across the 240 V line.... or 225 V
rated Mov's from hot to neutral on a 208 3 phase setup.
Their's are all fused as well as alarmed. The latest versions
all have "event counter's" in em.. with time date stamps, etc.
Some of the ones we use at work are 4" square and 1"
thick...each... amd fused... and alarmed.

### Dahl sells MOV's. Why do you think his large bolt down
ones are ALL 275 v rated ....and not 250 V rated ???

### Rich... you just love to cut corner's and engineer stuff
right to the peg... with zero leeway. Rauch does the same. The
whole beauty of HB stuff is one can build it right the 1st
time.... with no corners cut... and loads of headroom.

Later.... Jim VE7RF

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