On Nov 3, 2006, at 2:17 PM, jmltinc@... wrote:

In the VHF/UHF Handbook, chapter Receivers, Transmitters And Transceivers ,
section, 'Tuned Circuits'; the author writes: "If discs are used, the
capacitance varies in a very non-linear manner with the distance between them.
It is: C(pF) = 0.00885 x Area (sq mm) / Spacing (mm)"

The equation for capacitance vs area vs spacing is linear. What's up?

More taurine feces, John, Cheerz

John, N9RF



Yahoo! Groups Links

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

Gent's

Some poor fellow on the 'other' amp reflector smoked the 25 ohm 25
watt wire wound glitch R on his Henry 3K .

What was not mentioned was that Henry installs the glitch R in
the B-..... NOT the B+.... no big deal... cept the glitch R + all
wiring in/out of the glitch R has to use 10 kv wire.. and
glitch R well insulated from chassis... on stand offs.

He also smoked the safety diode between chassis and one end of
the glitch R. He had an arc between base of plate choke and
chassis.

Fault current simply flows from chassis up through under rated
puny glitch R.... through the glitch R... back to B-...... whereby u
guessed it.... the safety diode shorted out [wouldn't handle the
surge]... then the 4 kv is sitting right across the 25 ohm glitch
R... blowing it to Kingdome come !

The fellow replaced the glitch R... amp works.. BUT his grid meter
is off the scale ! As u can see if u trace it... with a shorted
safety diode.... the plate AND grid meter are now directly in
parallel ! [neg of grid meter bonded to chassis... flows along
chassis... through shorted safety diode back to B-... then to neg
of plate meter] 1/2 plate current flows through EACH meter..
then the grid meter get's smoked.

The fix is of course.. 2-3 x 6A diodes in parallel between
chassis and in his case.. glitch R.... OR B-.... if glitch R is in
the B+ lead ["normal amp"]

IF he had a HV fuse in the B+.... he would NEVER have smoked the
glitch R. The slow breaker in his 240 V line is just that... way
too damned SLOW.


Also... IF he had a FAST grid fuse between chassis and neg of
grid meter/shunt... u would not smoke the grid meter. He shoulda
also had safety diodes across both the grid + plate meter. On a
8877... it really needs electronic fast grid overcurrent
protection..... which I doubt would even work with the safety
diode shorted between chassis and his glitch R/ B-

To stop the arcing between base of plate choke and chassis...
install a teflon /plastic disc or square, between chassis and
bottom of plate choke. On a Henry.. with a choke in it... make
sure the bypass caps at the base of the plate choke are good for
10 kv. .... in case a wirewound let's go in the bleeder string...
otherwise.... no load plate V will skyrocket... as the HV supply
now looks like a C input filter.

later... Jim VE7RF

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

--- In ham_amplifiers@..., jmltinc@ wrote:

In the VHF/UHF Handbook, chapter Receivers, Transmitters And

Transceivers ,

section, 'Tuned Circuits'; the author writes: "If discs are

used,

the

capacitance varies in a very non-linear manner with the distance

between them.

It is: C(pF) = 0.00885 x Area (sq mm) / Spacing (mm)"

The equation for capacitance vs area vs spacing is linear.

What's up?

John, N9RF

########### Congrat's... u just found ur 1st mistake. If this is
orr's latest blue book..... which page is it on ??? I found 38
mistakes in it so far.. mainly typo's.... have not got to the
vhf/uhf stuff yet.

Jim

### You double the spacing between any two plates... and C

drops

to just 1/4 of the original. [ V rating doubles].

### conversely... u reduce the spacing by 1/2 the original...

and C

increases 4 x [V rating drops in 1/2]

later... Jim

--- In ham_amplifiers@..., jmltinc@... wrote:

In the VHF/UHF Handbook, chapter Receivers, Transmitters And

Transceivers ,

section, 'Tuned Circuits'; the author writes: "If discs are used,

the

capacitance varies in a very non-linear manner with the distance

between them.

It is: C(pF) = 0.00885 x Area (sq mm) / Spacing (mm)"

The equation for capacitance vs area vs spacing is linear. What's up?

John, N9RF

### You double the spacing between any two plates... and C drops
to just 1/4 of the original. [ V rating doubles].

### conversely... u reduce the spacing by 1/2 the original... and C
increases 4 x [V rating drops in 1/2]

later... Jim

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

wrote:

--- In ham_amplifiers@..., "zerobeat40"

<zerobeat40@>

wrote:

### When I look at the 2 x tone on the scope.... the

envelope varies from zero to full pep.

Z SEZ.... At what rate? The rate of the diff between the tones.

So, if your two tones are, say, 3Hz apart, then the power supply is
having to feed out current that varies at a 3Hz rate. Not a prob
with a bridge-cap power supply, but can cause wild fluctuations in
voltage for a choke-input supply.

### I get it now... at 3 hz... this would be like slowly turning up
the drive to the linear.. when on say cw mode... with a dead cxr...
up down up down.. etc. So what.... any HV supply should be able
to handle that.... esp a resonant choke set up???

### IOW... what u are saying is with a 3-20 hz rate... u are in
effect MODULATING the HV supply... at an AUDIO rate ???




On my bias
supplies... they are just a string of 6 A diodes with a 5000-
10,000 uf cap across em.. end to end.... and some .01 uf discs
between each end of string.... and chassis for bypass.

### Maybe for the bias... we need bigger bypass caps on each end
to chassis... like 1-10uf non polarized ... as well as the
usual .01 uf disc caps ??? [stagger tuned]

Z SEZ.... And, it's to test all the power supplies. The p-supply's
job is to feed out a fixed voltage, but let the current vary all
over the place, at any rate, without the voltage changing.

You can test it with CW pulses, then you have to use a scope to

watch power supply behavior.

### a scope across the last HV lytic [cold end] in a HV supply
should work... or the last two x lytics. A battery operated
digital fluke storage scope would be ideal... even for ssb.. or cw.





Or you can feed it two-tone IMD sigs, and measure the IMD coming
out to see if the power supply behavior is impacting the amp
performance.

### I have wondered about that.... Voice IMD vs HV
regulation... esp a C input HV supply. Well, I can easily add in
100uf and 50uf banks of caps... up to a whopping 450 uf of filter
cap [11 kv rated]

Z SEZ... No problem with a well-designed power supply, which has

low source

impedance from DC to high audio freqs.

### OK.. will big lytics in a HV supply handle high audio
freqs ??? Same question on my variable bias supply ??

Z SEZ....Maybe with modern PS design, it's a moot point. But, the

point is to test the PS regulation under dynamic load - varying
pulse rates.Z

### agreed... which is why I like putting loads of uf into my HV
supplies... kills 2 x birds at once.... results in superb dynamic
regulation.... and <1 % ripple. [ripple freq is of course 120 hz]

### since I mess with ESSB... and can easily put out 1.5 kw with
20 hz sine wave, voice etc... going into the analog BM... maybe
I should base stuff on down to say at least 30-50 hz.

### Right now.. I have several 2 x tone generators... none will
allow close spaced tones...they are all fixed.

Tnx Z... U answered my question.

later....... Jim VE7RF

Hey Jim,

No, the book is ARRL's VHF/UHF Handbook. The formula is correct, as it is
found elsewhere, including Orr's book (p 2-6, 23rd Edition). He includes the term
for inclusion of a dielectric.

He states (correctly, as the equation illustrates), that C is proportional to
the area of the plates and inversely proportional to the spacing between
them. Halve the spacing -- double the C.

My problem is the statement of Dick Bidulph, M0CGN, author of the ARRL
publication regarding the "nonlinear manner". Unless, of course, he is using a
nonlinear screw!

-J

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

--- In ham_amplifiers@..., "zerobeat40" <zerobeat40@>
wrote:

###> The 2 tone test is flawed, and isn't used anymore in the

commercial world. By juggling the spacing of the 2 x tones,

you can hit a .."sweet spot" and come up with really good IMD
numbers.

Z SEZ... That's usually with very wide spacing. At very narrow

spacing, you challenge the power supply bypassing, so the worst
numbers often occur at that test condition.

### Rauch sez the same thing....verbatim on his site...with no
explanation of course.


### OK... what am I missing here ??? I don't "get it". Why
would narrow two tone spacing... "challenge the power supply
bypassing" ??????

### Which supply.... the bias supply and or the HV supply???
What do you mean by "power supply bypassing"..... my giant 100 uf
C filter in my C input HV supply... or something else... like
bypass caps at the base of the plate choke ???

### When I look at the 2 x tone on the scope.... the envelope
varies from zero to full pep.

At what rate? The rate of the diff between the tones. So, if your
two tones are, say, 3Hz apart, then the power supply is having to feed
out current that varies at a 3Hz rate. Not a prob with a bridge-cap
power supply, but can cause wild fluctuations in voltage for a
choke-input supply.

And, it's to test all the power supplies. The p-supply's job is to
feed out a fixed voltage, but let the current vary all over the place,
at any rate, without the voltage changing.

You can test it with CW pulses, then you have to use a scope to watch
power supply behavior. Or you can feed it two-tone IMD sigs, and
measure the IMD coming out to see if the power supply behavior is
impacting the amp performance.

No problem with a well-designed power supply, which has low source
impedance from DC to high audio freqs.

In my early days in RF amp design (the amps were then being used in
the telephone system, to multiplex many long-distance phone calls onto
a single twisted pair), we made the mistake of a too-large plate
choke. That plate choke, when forced to dole out current pulses that
were fairly slow (several Hz), rang and resonated with the PS filter
caps (microfarards were a precious commodity in the 30s) and caused
arcing in the tubes.

Maybe with modern PS design, it's a moot point. But, the point is to
test the PS regulation under dynamic load - varying pulse rates.Z

I wrote:

In the VHF/UHF Handbook, chapter Receivers, Transmitters And Transceivers ,
section, 'Tuned Circuits'; the author writes: "If discs are used, the
capacitance varies in a very non-linear manner with the distance between them.
It is: C(pF) = 0.00885 x Area (sq mm) / Spacing (mm)"

The equation for capacitance vs area vs spacing is linear. What's up?

My question is perhaps not clear. The author states that "capacitance varies
in a very non-linear manner...". Yet the equation is linear. Now, what's up?

-J

In the VHF/UHF Handbook, chapter Receivers, Transmitters And Transceivers ,
section, 'Tuned Circuits'; the author writes: "If discs are used, the
capacitance varies in a very non-linear manner with the distance between them.
It is: C(pF) = 0.00885 x Area (sq mm) / Spacing (mm)"

The equation for capacitance vs area vs spacing is linear. What's up?

John, N9RF

--- In ham_amplifiers@..., "zerobeat40" <zerobeat40@...>
wrote:

###> The 2 tone test is flawed, and isn't used anymore in the

commercial world. By juggling the spacing of the 2 x tones,

you can hit a .."sweet spot" and come up with really good IMD
numbers.

Z SEZ... That's usually with very wide spacing. At very narrow

spacing, you challenge the power supply bypassing, so the worst
numbers often occur at that test condition.

### Rauch sez the same thing....verbatim on his site...with no
explanation of course.


### OK... what am I missing here ??? I don't "get it". Why
would narrow two tone spacing... "challenge the power supply
bypassing" ??????

### Which supply.... the bias supply and or the HV supply???
What do you mean by "power supply bypassing"..... my giant 100 uf
C filter in my C input HV supply... or something else... like
bypass caps at the base of the plate choke ???

### When I look at the 2 x tone on the scope.... the envelope
varies from zero to full pep.

### What's supposed to happen... if say the two tones are
a multiple of each other... like 1000 hz and 2000 hz..... or 500
hz + 1000hz? This is supposed to be a big 'no-no'. Looks to
me like they would still be .."in phase" regardless of spacing ?

### What 'bad' is supposed to happen if the two tones are say
1000 hz.... and 1120 hz..... or 1000 hz and 1060 hz ??? Is
the 120/60 hz difference freq supposed to modulate the linear
at an audio rate or something ???

I'm completely lost.

later.... Jim VE7RF

On Nov 2, 2006, at 11:03 PM, pentalab wrote:

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

On Nov 2, 2006, at 6:46 PM, zerobeat40 wrote:

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

wrote:

On Nov 2, 2006, at 2:49 PM, zerobeat40 wrote:

My word, did I write that? At my age, I am often guilty of

mis-

types
of all sorts. 20 mA is far more than I would expect, and I

seem to

recall that I did the experiment shortly after writing about

it

here.
I probably posted the results as well. Certainly there is

grid

current in the normal direction.

Not with several volts negative on the grid with respect to

the

cathode.

Did you measure it or are you still depending on the data sheet?

Both. but not with a uA meter.

#### well, I just tried it on one of my 3 x L4B's.... I get ZERO
grid current with no drive applied.... whether both 3-500Z's
installed... or just ONE 3-500Z installed...... and that's with
2650 V..... doesn't matter whether I run ZERO bias... 2.1 V
bias... 4.2 v bias... or 7.0 v bias.

Which is what the characteristic curves indicate.

The grid meter is a 0-400
ma deal. I suppose one could insert a Fluke 87 dvm in series
with the grid shunt.... and take a dead on reading. IF there is
gonna be any grid current.... it's gotta be pretty close to zip.

As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the

grid. Grid

current will not be zero unless the tube is cutoff.

hardly

Did you measure that, or are you still consulting the road map

which

may or may not agree with the roads?

What's my surname?

### I think it's still Measures.

Correct, and I measure things to find answers.

Please do not hesitate to point out errors and inconsistencies.

Never, ever.

Glad to hear it. I'm thankful for this new group, we need never
mention the old one and we'll likely be happier.

The AMPS group is doing today what it was originally designed to
do: save Tom from the problems he caused to himself during the
parasitics debate on rec.amateur-radio.homebrew - an uncensored
Newsgroup. I got booted off of AMPS 4-times for questioning Tom's
questionable statements. As I see it, a discussion group that
allows any participant to get away with technical bologna and
censors members who ask embarrassing questions is rotten.

...
### I see we are up to aprx 158 members I think... and almost 900
posting's.

### after reading 'AMPS' since day 1.... I'm surprised at the
amount of really bad advice handed out over 10 yrs.... that never
got challenged. Some of us could separate 'wheat from
chaffe'... but I'm afraid a lot of newbies just got bamboozled.
A huge amount of good idea's too in the last 10 years.

Agreed, Jim. All in all I think AMPS did moderately okay up to the time that Bill Fisher died and someone with an axe to grind took over.

Later... Jim VE7RF

Yahoo! Groups Links

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

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

On Nov 2, 2006, at 6:46 PM, zerobeat40 wrote:

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

wrote:

On Nov 2, 2006, at 2:49 PM, zerobeat40 wrote:

My word, did I write that? At my age, I am often guilty of

mis-

types
of all sorts. 20 mA is far more than I would expect, and I

seem to

recall that I did the experiment shortly after writing about

it

here.
I probably posted the results as well. Certainly there is

grid

current in the normal direction.

Not with several volts negative on the grid with respect to

the

cathode.

Did you measure it or are you still depending on the data sheet?

Both. but not with a uA meter.

#### well, I just tried it on one of my 3 x L4B's.... I get ZERO
grid current with no drive applied.... whether both 3-500Z's
installed... or just ONE 3-500Z installed...... and that's with
2650 V..... doesn't matter whether I run ZERO bias... 2.1 V
bias... 4.2 v bias... or 7.0 v bias. The grid meter is a 0-400
ma deal. I suppose one could insert a Fluke 87 dvm in series
with the grid shunt.... and take a dead on reading. IF there is
gonna be any grid current.... it's gotta be pretty close to zip.

As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the

grid. Grid

current will not be zero unless the tube is cutoff.

hardly

Did you measure that, or are you still consulting the road map

which

may or may not agree with the roads?

What's my surname?

### I think it's still Measures.

Please do not hesitate to point out errors and inconsistencies.

Never, ever.

Glad to hear it. I'm thankful for this new group, we need never
mention the old one and we'll likely be happier.

The AMPS group is doing today what it was originally designed to

do: save Tom from the problems he caused to himself during the
parasitics debate on rec.amateur-radio.homebrew - an uncensored
Newsgroup. I got booted off of AMPS 4-times for questioning Tom's
questionable statements. As I see it, a discussion group that
allows any participant to get away with technical bologna and
censors members who ask embarrassing questions is rotten.

#### The 'amps' group on contesting.com is pretty well a dead
duck these days. Last heard, they were debating drill speeds
for drilling HARD steel. Of course, someone suggested
starting with a small bit like 1/8"... then work ur way up in
size..... and use plenty of cutting fluid. The bad advice
given was recomending a speed of 1000 rpm for the 1/8" bit....
which is WAY too fast. On my vertical/horizontal bandsaw...
made for cutting aluminum, steel, and hard steel.... speeds are
200 ft per min... 120... and 80.. respectively. Of course, our
local idiot at the local tool place sez 1500-2000' per minute is
just fine for cutting thick 6061-T6 aluminium. Ditto with
using wax on Greenlee punches. Correct glop is called A-9 cutting
fluid [for aluminium] A-9 is this green glop... works great on
drill bits too... cut's like butter... just 1-2 drops needed.

### I see we are up to aprx 158 members I think... and almost 900
posting's.

### after reading 'AMPS' since day 1.... I'm surprised at the
amount of really bad advice handed out over 10 yrs.... that never
got challenged. Some of us could separate 'wheat from
chaffe'... but I'm afraid a lot of newbies just got bamboozled.
A huge amount of good idea's too in the last 10 years.

Later... Jim VE7RF

On Nov 2, 2006, at 6:46 PM, zerobeat40 wrote:

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

On Nov 2, 2006, at 2:49 PM, zerobeat40 wrote:

My word, did I write that? At my age, I am often guilty of mis- types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction.

Not with several volts negative on the grid with respect to the cathode.

Did you measure it or are you still depending on the data sheet?

Both. but not with a uA meter.

As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

hardly

Did you measure that, or are you still consulting the road map which
may or may not agree with the roads?

What's my surname?

Please do not hesitate to point out errors and inconsistencies.

Never, ever.

Glad to hear it. I'm thankful for this new group, we need never
mention the old one and we'll likely be happier.

The AMPS group is doing today what it was originally designed to do: save Tom from the problems he caused to himself during the parasitics debate on rec.amateur-radio.homebrew - an uncensored Newsgroup. I got booted off of AMPS 4-times for questioning Tom's questionable statements. As I see it, a discussion group that allows any participant to get away with technical bologna and censors members who ask embarrassing questions is rotten.

There
are days when I am amazed that I remember which end of a fork to hold.

Forrest Gump was right, Zed, and it definitely happens to us codgers.

I qualified for my first senior citizen discount 45 years ago.

You got me beat.

Must
have become a codger about the same time. I think that phase ends,
like adolescence. I think I fall into that category known as a living
sarcophagus.

chortle -- or how about a virtual mummy?

cheerz

Whatever it's called today, I know I've always been a
curmudgeon.

Z





Yahoo! Groups Links

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

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

On Nov 2, 2006, at 2:49 PM, zerobeat40 wrote:

My word, did I write that? At my age, I am often guilty of mis-types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction.

Not with several volts negative on the grid with respect to the cathode.

Did you measure it or are you still depending on the data sheet?

As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

hardly

Did you measure that, or are you still consulting the road map which
may or may not agree with the roads?

Please do not hesitate to point out errors and inconsistencies.

Never, ever.

Glad to hear it. I'm thankful for this new group, we need never
mention the old one and we'll likely be happier.

There
are days when I am amazed that I remember which end of a fork to hold.

Forrest Gump was right, Zed, and it definitely happens to us codgers.

I qualified for my first senior citizen discount 45 years ago. Must
have become a codger about the same time. I think that phase ends,
like adolescence. I think I fall into that category known as a living
sarcophagus. Whatever it's called today, I know I've always been a
curmudgeon.

Z

On Nov 2, 2006, at 3:30 PM, Tony King - W4ZT wrote:

I would expect, at that plate voltage and 3-5 volts bias you'd have
significant ZSAC... but I'd think that grid current, if any, with no
drive would be measured in microamps. True?

Probably pico-A with 5v of reverse bias.

73, Tony W4ZT

zerobeat40 wrote:

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

True enough, Denny
Z. I did the same experiment when I was in college. Zeb's problem
is that he is the person who said:
#643
Re: SB-220 Questions

"With 3.5kV applied, a
good tube in one socket, and +3-5V on the cathode with no RF drive,
you should have about 20mA grid current in the normal direction."
- Z

My word, did I write that? At my age, I am often guilty of mis-types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction. As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

Please do not hesitate to point out errors and inconsistencies. There
are days when I am amazed that I remember which end of a fork to hold.


Z

Yahoo! Groups Links

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

On Nov 2, 2006, at 2:49 PM, zerobeat40 wrote:

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

True enough, Denny
Z. I did the same experiment when I was in college. Zeb's problem
is that he is the person who said:
#643
Re: SB-220 Questions

"With 3.5kV applied, a
good tube in one socket, and +3-5V on the cathode with no RF drive,
you should have about 20mA grid current in the normal direction."
- Z

My word, did I write that? At my age, I am often guilty of mis-types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction.

Not with several volts negative on the grid with respect to the cathode.

As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

hardly

Please do not hesitate to point out errors and inconsistencies.

Never, ever. This is what got me jackbooted off of AMPS, Zed. Examples of statements that I questioned: AC circuit analysis does not work with R/L VHF parasitic suppressors; Ni-Cr alloys (a.k.a. resistance-wire) has reverse skin effect as frequency decreases; VHF- resonant circuits can not ring when pulsed; dip=meters are unreliable, over-driving an SB-220 can produce 3x the normal pk-V in the anode circuitry, on and on in the world according to W8JI.

There
are days when I am amazed that I remember which end of a fork to hold.

Forrest Gump was right, Zed, and it definitely happens to us codgers.

cheers

Z






Yahoo! Groups Links

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

开云体育

That's too bad.. it's elitist...
I can remove any email (spammer) by just administering
the list. His excuse of stopping spammers is bogus...
There was a ALPHA list somewhere else too...maybe it went defunct.
I know I joined it about 10 years ago but left after a FEW YEARS..
no messages....NO ONE EVER HAD PROBELMS... :-)

Larry Anderson wrote:

Mark wrote:

> I just ran across this on yahoo groups
>
>
> <>
>
> 73
> Mark
> W0NCL
>
> __________________________________________________________
> Get your email and see which of your friends are online - Right on the
> New Yahoo.com
> ( <>)
>
>

And apparently you must have a call sign to join too.

-- 
Bob
Vmoa chat list -> 
Vmoa tech list home -> 


Middleburg Fl (South Jacksonville)
ICQ 13912841
Web Page 

Visit the FDXPG at  

Ham Radio Calls: KR4DA FG/KR4DA J79DA HK0/KR4DA

Motorcycles CBMMA #4
1977 XS750D 1J7008405
1997 Vmax12J VMOA #504 

开云体育

Message 863 is not there as you stated...
I have no clue where it went..
And there is NO censoreing on this list.

Just play nice.

pentalab wrote:

If u scroll through the messages... u will see that # 863 has been
blown out ! I responded to it last night... then it comes back
as "message 863 can't be retrieved" Did the fellow blow it out
himself... or was it censored... or what ?

-- 
Bob
Vmoa chat list -> 
Vmoa tech list home -> 


Middleburg Fl (South Jacksonville)
ICQ 13912841
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Ham Radio Calls: KR4DA FG/KR4DA J79DA HK0/KR4DA

Motorcycles CBMMA #4
1977 XS750D 1J7008405
1997 Vmax12J VMOA #504 

Microamps is still not zero...Rich is claiming zero.

I think I measured fractional milliamps - e.g. hundreds of microamps.
May have to re-run the exp.

The 3-500Z is not a tube I have a lot of experience with, certainly
later in my career power levels of that nature would be handled with
silicon.

Z


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

I would expect, at that plate voltage and 3-5 volts bias you'd have
significant ZSAC... but I'd think that grid current, if any, with no
drive would be measured in microamps. True?

73, Tony W4ZT

zerobeat40 wrote:

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

True enough, Denny
Z. I did the same experiment when I was in college. Zeb's problem
is that he is the person who said:
#643
Re: SB-220 Questions

"With 3.5kV applied, a
good tube in one socket, and +3-5V on the cathode with no RF drive,
you should have about 20mA grid current in the normal direction."
- Z

My word, did I write that? At my age, I am often guilty of mis-types
of all sorts. 20 mA is far more than I would expect, and I seem to
recall that I did the experiment shortly after writing about it here.
I probably posted the results as well. Certainly there is grid
current in the normal direction. As long as the tube is not cut-off,
it is a guarantee that some electrons will intercept the grid. Grid
current will not be zero unless the tube is cutoff.

Please do not hesitate to point out errors and inconsistencies. There
are days when I am amazed that I remember which end of a fork to hold.


Z

I would expect, at that plate voltage and 3-5 volts bias you'd have significant ZSAC... but I'd think that grid current, if any, with no drive would be measured in microamps. True?

73, Tony W4ZT

zerobeat40 wrote: