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
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 

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:

--- 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

On Nov 2, 2006, at 1:10 PM, pentalab wrote:

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

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

RICH SEZ... Do you have a FCC callsign?

Z SEZ.... No, sir. Is that a requirement for inclusion in this

group?

RICH SEZ.... Definitely Not. So why do you hide your name?

Z SEZ...I don't hide my name. My given name is Z Sampson

Thompson, per my birth cert. No ham ticket, no callsign. Not a
famous author, nobody knows me anyway. Why does it matter. I've
gone by "Z" or "Zed" all my life.

Career was spent in comunications and related...HF/SW broadcasting,
ship-to-shore, etc. Climbed lots of towers, designed lots of
transmitters, had hams around me the whole time of course and even
have been heard on HF SSB from one or another ham's station, but

never got around to getting the ham ticket.

Any other personal questions on your mind?

Z

### Hey Rich.... u finished cleaning the EGG off ur face yet ???

### Here's a fellow who has seen it all, done it all, designed it
all, repaired it all.,

Tom Rauch has done that too.

probably dealt with every manufacturer of
every piece of Commercial + Broadcast gear ever made since day
1....... then gets kicked off the... 'amp reflector'.... cuz he
doesn't have a FCC callsign !

I got kicked off and I have a callsign.

What a load of crap. It's
fellow's like this who have a lifetime of experience.... who's vast
knowledge is a major asset to a group like this.

The fly in the ointment is Zed's 20mA of grid current with the grid several volts negative with respect to the cathode.

### Rich... u can laff at 11-m ops all u want to....

I don't because I have talked to some who are knowledgeable about QRO. I talked to one 11m builder who built smaller mobile amplifiers using the 4cx3000A.

but anybody
who can design and install 3 x 3CX3000F7's in a mobile setup...
and have the where with all to generate that much AC power... plus
an ant to go with it... obviously isn't stupid.

Agreed

They got it
over our local 2M FM ops here in town... who... "touch the coax
once in a while to make sure it's not getting hot... running 25
w "

### sounds to me like "Z".... just got vindicated.

You might be treading on quicksand, Jim. Amplifier experts are experts in knowing when to use their ears instead of their mouth.

... and I
doubt "Z" would semi-float the grids on a 3-500Z linear either.

Floating 3-500Z grids does nothing very exciting.

Heck... for all we know... the "Z" in 3-500Z was probably in
his honour.

chortle

later.... Jim VE7RF

Yahoo! Groups Links

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

No He's ZED from Men in Black

BOB DD

### sounds to me like "Z".... just got vindicated.... and I
doubt "Z" would semi-float the grids on a 3-500Z linear either.
Heck... for all we know... the "Z" in 3-500Z was probably in
his honour.

later.... Jim VE7RF

On Nov 2, 2006, at 6:58 AM, ad4hk2004 wrote:

Z is slick... The bench test with just the filament heated fills the
tube with an electron cloud... The electrons have velocity... Some
will impact the grid and be captured... The grid will become more
negative and the excess electrons will flow from the grid to any less
negative point...

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
-------------------------
With +3 to +5 volts on the cathode, "about 20mA" does not flow. Zero grid current flows because the grid potential looks negative with respect to the cathode. .

Consider, that although we view the
filament/cathode to be negative it has electrons departing under
thermal acceleration which makes the filament structure itself less
negative...
I don't have the time at the moment but I will do a bench check on
some 4CX1000's that just happen to be hanging around under the bench
at the moment... I suspect that each individual element in the tube
will show voltage/current under Z's conditions..

With 3 to 5 volts negative on the grid, there should be "about 20mA" of grid current if Z is correct in this matter.

cheers

denny / k8do





Yahoo! Groups Links

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

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

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

RICH SEZ... Do you have a FCC callsign?

Z SEZ.... No, sir. Is that a requirement for inclusion in this

group?

RICH SEZ.... Definitely Not. So why do you hide your name?

Z SEZ...I don't hide my name. My given name is Z Sampson

Thompson, per my birth cert. No ham ticket, no callsign. Not a
famous author, nobody knows me anyway. Why does it matter. I've
gone by "Z" or "Zed" all my life.

Career was spent in comunications and related...HF/SW broadcasting,
ship-to-shore, etc. Climbed lots of towers, designed lots of
transmitters, had hams around me the whole time of course and even
have been heard on HF SSB from one or another ham's station, but

never got around to getting the ham ticket.

Any other personal questions on your mind?

Z

### Hey Rich.... u finished cleaning the EGG off ur face yet ???

### Here's a fellow who has seen it all, done it all, designed it
all, repaired it all., probably dealt with every manufacturer of
every piece of Commercial + Broadcast gear ever made since day
1....... then gets kicked off the... 'amp reflector'.... cuz he
doesn't have a FCC callsign ! What a load of crap. It's
fellow's like this who have a lifetime of experience.... who's vast
knowledge is a major asset to a group like this.

### Rich... u can laff at 11-m ops all u want to.... but anybody
who can design and install 3 x 3CX3000F7's in a mobile setup...
and have the where with all to generate that much AC power... plus
an ant to go with it... obviously isn't stupid. They got it
over our local 2M FM ops here in town... who... "touch the coax
once in a while to make sure it's not getting hot... running 25
w "

### sounds to me like "Z".... just got vindicated.... and I
doubt "Z" would semi-float the grids on a 3-500Z linear either.
Heck... for all we know... the "Z" in 3-500Z was probably in
his honour.

later.... Jim VE7RF

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

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

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.

### say what ??? What diff does the spacing on a 2 tone test
have to do with challenging the HV supply bypassing... or any other
supply ? What am I missing here ?? The HV supply is just
pumping out DC current... nothing else. A 2 x tone test should
be in a steady state... ur not modulating it at an audio rate or
anything else ?

They all use the noise test these days... pump the xcvr with
bandwidth limited white noise.... that will drive the xcvr to

full pep output.... and simulate voice or many data tones. In
the commercial world, it's common to use 4 x multiplexed ssb

channels... or as many as 16 x mark/space combo's...

sometimes interleaved.

Z SEZ... Power Ratio puts band-limited white noise through the

rig, with a notch in the middle of it. IMD products will tend to
fill in the notch. Very harsh test.

### I tried it last night. Easy to do. The TX filters in my
xcvr are 6 khz wide. I notched out the portion from 2-4 kz.... and
passed 0-2 khz.... and 4-6 khz. You can hear the 2-4 notched
out portion.... being partially filled in.... on a 2nd Rx...3'
away. IMO... this just shows one INBAND IMD. Still... it
also shows OUT of band IMD.... a good test...and easy to do with a
Behringer DEQ-2496 master processor.

Here's a quote from "SSB systems and circuits"

"ANOTHER deficiency of the 2 x tone test is that the "3rd

order"

products observed on a spectrum analyzer are actually the sum

of

the 3rd and ALL higher ODD order components. Typ, the 5th

order

component is OUT of phase with the 3rd, which tends to PRODUCE
distortion CANCELLATION. This leaves the FALSE impression that

the

IMD is better than it really is."

Z SEZ...Sad It's in error. The 5th order component is at a

different frequency than the 3rd order component, therefore they
are completely distinguishable from each other.

Ex: 5MHz and 5.001MHz are the incident sigs. The 3rd ord will be
4.999 and 5.002 MHz. 5th order will be 4.998 and 5.003 MHz. They
don't sit on each other, and don't add to each other in any way.

### I don't think that's their point. Usual deal is to feed two
transmitter's, each with a dead cxr... into a combiner... then the
combined output feeds a Class A amp.. like a 4x5.... then into
linear amp under test. [both Eimac/Rauch and ARRL lab use the same
method] There is nothing to stop the PHASE of the IMD
products from being out of phase with each other... which could
easily skew the results.

BTW... when running white noise into the xcvr.... the plate

current on the linear is EXACTLY 1/2 the key down value.... so
u can use white noise to tweak the tune/load caps to max pep
output.

Z SEZ... You're driving it too hard. Peak to average ratio of BW-
limited white noise (the voltage distribution of BW-limited white
noise is closer to a Rayleigh distribution) is approx 16:1. The
word "approx" is important beause in truth, there is some
percentage probability of ANY power level being present at some
time. 16:1 is the diff between 50% probabiliy and 1%. Adequate
for communications-grade amps.

### I put some pure NON notched, full 0-20 khz white noise from
external audio rack gear directly into analog BM of xcvr. No ALC
showing... nothing over driven either. Then watched the RF on the
RF monitor scope... plus has 2 x PEP wattmeter's running... plus
2 x more wattmeter's.. switched to 'AVERAGE' Plate current on
linear is exactly one half the key down value. AVERAGE RF output
is only 1/5 the PEP output... or 14 db down from PEAK... or
7db down from PEP.

In U.S. dialects, a vocalized sibiliant contains both low and

high. E.G. "Z" or "J". However, the wide-spaced test is actually
one of those that does not stress the power supply much, therefore
you tend to get artificially good values.

Try as hard as you want... you can't find ANY combo of words or
phrases that will produce SIMULTANEOUS highs and lows.

Sure can...any vocalized sibilant. To be exact, "Z" is a "voiced
alveolar sibilant" and is often used as a "torture test" for

system BW commercially when test gear is unavailable.

### are u talking about "ZEE" or a "ZED" Not much of a torture
test at all. ZEE or ZED has not much low content in it at
all. Now words like Boom... Four... Ola... etc... will really
enhance low freq stuff... and the peak to average ratio really
drops. The point here is that ESSB doesn't splatter all over the
band.

Has anybody tried adjusting the Zsac on these big tubes from

one

extreme to the other.. and actually measured the imd ??

Kinda a

moot point... unless the xcvr is the same or better IMD wise,
nobody would ever hear any benefit.

The tendency is for IMD to vary in only a small amount. You can
improve it at low levels by sending the ZSAC very high, but that

does not change IMD at high levels. When you get ZSAC to a too-low
level, IMD shoots up quite a bit. That's why even in commercial
gear, fixed-voltage bias is common, it just doesn't matter much as
long as you've got some ZSAC.

### This is what I suspected. I also heard... if u bias a GG amp
like a SB-220 into zero zsac [class b] or into class C... on
CW, u will get key clicks ???

### I'm gonna try it anyway. I don't like this fixed bias idea..
never did. I see too many differences in zsac... between 4 x
diff tubes... all new... same maker... change maker's... diff
results. I have seen flat tubes with more zsac than a good
one.... [this is for a fixed bias V]

### On multiple tube GG amps... I used 2 x fil xfmrs [or 0ne
fil xfmr.. with 2 x sec] with 3 x separate plate curent
shunts.... one for tube 1 one for tube 2.. and 3rd for tubes
1+2. Plus independent adjustable bias for EACH tube.

## Now I just mess with one tube linears. Being able to vary the
bias from A-Z is a huge advantage. The constant current graphs
for most tubes... esp big ones... sorta are ballpark zsac
values... for say zero bias... and a fixed plate V..... could be
anywhere between 2 x extremes. A 3x 3... per the graphs could
idle at anywhere from 250-600 ma with zero bias at say 5 kv.
I want it to idle at 150 ma.... so just installed a sting of
6 A diodes... and a rotary switch... plus a huge lytic across the
entire string... works slick. Those zeners are a pain... and
failure prone... and none adjustable. Back in the mid-late
70's... 50 watt zener's were a dime a doz.. and cheap....but they
had to be heat sinked too... and insulated from chassis. Zener's
are ancient history now.

### This should be fun running the MK-V in Class A... then
tweaking the bias on the GG amp from Class A to AB.... then see
what happens. The amp will probably need it's tuned input
tweaked a tiny bit... diito with PI out put.... each time bias is
changed radically. Of course the anode diss will go UP...
since the eff in class A is going down. I'm guessing 25%
eff in Class A.

later... Jim VE7RF

Z

Z is slick... The bench test with just the filament heated fills the
tube with an electron cloud... The electrons have velocity... Some
will impact the grid and be captured... The grid will become more
negative and the excess electrons will flow from the grid to any less
negative point... Consider, that although we view the
filament/cathode to be negative it has electrons departing under
thermal acceleration which makes the filament structure itself less
negative...
I don't have the time at the moment but I will do a bench check on
some 4CX1000's that just happen to be hanging around under the bench
at the moment... I suspect that each individual element in the tube
will show voltage/current under Z's conditions..

denny / k8do