Driver to drive?

[Cursitor Doom]

On Sun, 26 Mar 2017 02:03:24 -0400, Michael A. Terrell wrote:

Do you watch that garbage? It's intended for the low intelligence
liberals. Oh! Sorry, I forgot who I was asking that.

He probably hasn't moved on from Sesame Street yet.

 

[Cursitor Doom]

On Sun, 26 Mar 2017 08:03:56 +0100, Kevin Aylward wrote:

What part of "Please cite the exact law that says that a prosecutor must
demand the death penalty."

Do you not understand?

Which State does that question relate to, Kev? I don't recall you
specifying one.

 

[Cursitor Doom]

On Sun, 26 Mar 2017 02:14:11 -0400, Michael A. Terrell wrote:

> The KKK was full of those hate mongering Democrats.

Yes, funny how that's conveniently forgotten nowadays. Like the fact that
Democrats opposed ending slavery and that every single one of those slave
ships engaged in that vile trade was Jewish-owned.
We're dealing with people who have selective memory loss at best and
wilful ignorance at worst.

 

[Cursitor Doom]

On Sun, 26 Mar 2017 02:26:02 +0000, Jasen Betts wrote:

On 2017-03-25, Cursitor Doom <curd@notformail.com> wrote:
On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time?

Last I Heard it ws cheaper than death row.


We have an overcrowding crisis right now because the system is clogged
up by 'bed-
blockers' who could easily be removed at zero further cost to the
taxpayer.

Letting them out seems kind of recklesxs

Have you been drinking again?

 

On Sun, 26 Mar 2017 03:11:20 -0400, rickman <gnuarm@gmail.com> wrote:

On 3/26/2017 2:07 AM, Michael A. Terrell wrote:
rickman wrote:
On 3/24/2017 9:03 AM, Michael A. Terrell wrote:
krw@notreal.com wrote:
On Thu, 23 Mar 2017 14:58:23 -0400, "Michael A. Terrell"
mike.terrell@earthlink.net> wrote:

krw@notreal.com wrote:
On Sun, 19 Mar 2017 14:19:57 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Sat, 18 Mar 2017 20:03:50 -0400, krw wrote:

That's impossible, which is the whole "reasonable" thing.

Nothing whatsoever impossible about it!

Not at all. There is always doubt. It may be an unreasonable doubt
but there is _always_ doubt (what if the Earth was really flat?).
Hence, "beyond reasonable doubt".


What do you think of this sorry piece of work?

http://www.wftv.com/news/local/ayala-to-explain-why-she-wont-seek-death-penalty-against-murder-suspect-markeith-loyd/503151996




She should *immediately* be removed from office for violating her
oath of office to follow the constitution and laws of the state of
Florida.
That decision isn't hers to make.


The Governor has removed her from the case, but she want to sue
over it.

Disbar the jackass.

What did she do wrong? It is in the prosecutor's domain to decide how
to prosecute a case. I haven't looked up the law, but I seriously
doubt it says the death penalty is mandatory in all cases.


You are truly a Sloman. She refuses to do it for any case brought
before her. If you would actually look at links instead of firing from
the lip, you wouldn't look like someone with the IQ if ice water.

What did she do that was illegal? What rule did she break that should
get her fired?

Prosecutors don't make law, Ricky. Legislatures do. The executive's
job is to carry out the laws as the legislature writes them. If they
can't, or won't do it, they have no business in that job. I know
you're too stupid to see.

 

On Sun, 26 Mar 2017 10:33:51 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Sat, 25 Mar 2017 20:24:16 -0400, krw wrote:

That's *exactly* the point, moron. If the other person is lying, there
is no intention of having a conversation. It's the favorite tool of you
lefties.

No, the favourite tool of the Lefties is to scream 'racist!' at you
whenever you get the better of them in an argument (which inevitably is
every time).

Just an example of the big lie.

 

On Sun, 26 Mar 2017 02:18:31 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

rickman wrote:
On 3/24/2017 6:02 AM, Jeroen Belleman wrote:
On 2017-03-23 20:49, Michael A. Terrell wrote:


I would rather have a 'redneck' on my side in a fight, than an
'ineffectual' intellectual.


A redneck can help you win a fight, but you need the intellectuals
to have a chance to win the war.

How about redneck intellectual?


You would be surprised how smart some Rednecks are, if you weren't
so stupid. The original 'rednecks' were farmers, who worked out in the
hot sun from dawn till dark.

Intellectual <> smart or wise

 

On Sat, 25 Mar 2017 23:30:39 -0700, John Robertson <spam@flippers.com>
wrote:

On 2017/03/25 6:26 PM, Jasen Betts wrote:
On 2017-03-25, Cursitor Doom <curd@notformail.com> wrote:
On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time?

Last I Heard it ws cheaper than death row.


We have
an overcrowding crisis right now because the system is clogged up by 'bed-
blockers' who could easily be removed at zero further cost to the
taxpayer.

Letting them out seems kind of recklesxs


Part of the problem appears to be that the USA locks up more people per
capita than any other developed nation.

Why?

Because we have more criminals. Duh! The left has made a permanent
underclass of losers.

 

[amdx]

On 3/26/2017 4:36 AM, rickman wrote:

On 3/26/2017 5:00 AM, amdx wrote:
On 3/25/2017 11:00 PM, rickman wrote:
On 3/25/2017 11:42 PM, amdx wrote:
On 3/25/2017 8:32 PM, rickman wrote:
On 3/25/2017 9:10 PM, amdx wrote:
On 3/25/2017 5:25 PM, dagmargoodboat@yahoo.com wrote:
On Saturday, March 25, 2017 at 3:20:31 PM UTC-4, rickman wrote:
On 3/25/2017 2:33 PM, dagmargoodboat@yahoo.com wrote:

Summary:
o The FET-as-voltage follower has a gain of 0.98, which is quite
decent for our purposes.
o Input capacitance is 1.2pF.
o We've reduced the input capacitance by a factor of about 4
compared
to Kleijer, but it's still not as low as expected.

The shield driver + BNC isn't going to work, not until we get the
gain closer
to 1, rather than 0.25.

The gain of 0.25 is not because of the voltage follower, it's from
the
series cap.

The net gain's a result of the *divider* formed by the series
coupling
cap
and (the FET input capacitance + strays), multiplied by the follower
gain.
I asked Mike to measure the follower gain so we could then calculate
the
input capacitance.

Are you suggesting you can get the amp input capacitance
down to 10x less than the series cap?

Bootstrapping should reduce the FET input capacitance by a factor of
1/(1-G), where G = the gain of the bootstrap.

Another approach would be to put the series cap outside the box in
the
probe tip as is done in o'scopes. Then the gain of the amp
would be
sufficient to tie the coax shield to the output of the amp.

That's true. Mike could use a shielded connector and cable if he
didn't
mind putting his series cap at the probe.

The plan is to permanently wire the coax end to the tuning cap, and
then
swap different coils to it.
I was about to say that a series cap at the probe not a good plan,
but I
could put some type of permanent connection on my tuning cap to hold
the
0.4pf cap and the connect the coax to that. I suspect I'd be adding
capacitance with that though.

If you add the 0.4 pF cap with the coax on the amplifier side of the
cap, you will be adding 0.4 pF capacitance maximum. If you add the
coax
without the cap or put the cap on the amplifier end of the coax
without
the amplifier driving the shield, you will likely be adding a lot more
than 0.4 pF.

Why do you want to add the coax permanently?

I don't care if it is coax or a pair of wires. I want a battery
operated fixed testing setup. The 50 ohm output will after a peak
detector or demodulator and then a meter, may need a log amp. With it I
could compare the output of different ferrite antennas. I could
drive an
antenna with my sig/gen and measure Q using the 3 db method, etc.

Ok, I understand now. I wasn't getting that this is a test fixture. It
will never be operated without the amp. Where you put the captive coax
doesn't matter then.

Since your series cap can be made pretty consistently, I would suggest
adding it to the fixture before the coax. Then the entire coax and
amplifier capacitance impacts to the test fixture will be minimized
regardless of how well you can mitigate the capacitance through the
bootstrap circuit.

If you need another cap for another type of test, you can hole punch
another fairly easily and it should have pretty much the same
capacitance. One advantage of having a significantly larger capacitance
at the amp input is that it will have less impact on the end to end gain
if it varies.

How long a cable will you use? By that I mean how many pF?


I have no understanding of how putting the 0.4pf cap at the end of the
coax makes it easier to cancel. I probably need to go back and read
the thread.

What I meant was, the point of adding the 0.4 pF cap in line is to limit
the capacitance seen by the device being measured. If you leave off the
cap the device being tested sees the entire capacitance of the measuring
device. If you add the cap in front of all the added capacitance the
device being measured only sees the combination which will always be
less than the 0.4 pF cap (series capacitors combine like parallel
resistances, 1/Ctot = 1/C + 1/C2).

If you put the cap at the end of the coax right next to the unit you are
testing, then all capacitance after that point is isolated so the unit
doesn't "see" it. That's the advantage of putting it there.

Great, now I see the reasoning.

This does nothing about the impact of the added capacitance of the coax
and the input capacitance of the amp in terms of affecting the amplitude
of the signal. The larger this capacitance, the more the signal is
attenuated at the input of the amp. So it will help the gain of the
overall amp circuit to reduce the input capacitance of the amp.

That said... Since you can add gain after the input stage, why exactly
is it important to reduce the impact of the amplifier input capacitance
to nearly nothing?

The only importance would be, you would not need to retune after
adding the amp to an LC. Doesn't affect a fixed instrument, unless
you have calibrated tuning cap.
Also, if the amps input capacitance was lossy like having a cap with
poor bushing connection, this would lower Q.
And, it would be neat to have an instrument that when connected has no
measurable effect on the circuit under test.


The original amp had a voltage loss of 17:1 from the

capacitance voltage divider, if I am reading it all correctly. This is
now reduced to 4:1. When you add the capacitance of a coax to the
circuit the voltage divider ratio will go back up significantly.

I would try to minimize the length of the coax to minimize the
capacitance. If you can improve the bootstrapping of the circuit that
will be great. But when you reach the limit of what it will do, it will
be easy enough to set the gain of the following stages to make the
overall gain what you want, which is 1. I think it will be more
important to construct this so the gain is stable rather than trying to
get the gain of the first stage to be as close to 1 as possible.


Re, how many pf of coax, I was thinking maybe 6 inches of RG58, maybe
13pf. This a question of component layout to minimize losses. However,
it look to me like I could just set the tuning capacitor on top of the
amplifier housing, Probably even have physical contact between the
stator frame and the amp housing. That would only leave a 2-1/2" wire to
connect the amp input pin the the rotor tab on the capacitor.
Here is a picture of my first thought.
https://www.dropbox.com/s/ifgklgfxavb7ash/Cap%20and%20amp%20connections.jpg?dl=0


Ignore the added trim cap, it was needed for a test. Although I will
probably include the trim cap, but I will mount it forward about an inch.
The trim cap was too big and I had to remove six plates, I'll
probably remove at least one more, as it was still hard to peak
some of my coils.

I would say the mounting looks like a good idea. I'm not sure I would
bother with a coax. I'd use a stiffer wire so it is less likely to
bend, maybe 14 gauge. As it moves around it changes the capacitance
which changes the gain.

If I do mount the cap and amp like that, I would make an aluminum
plate similar to the one holding the trim cap, but reaching both screws
near the bottom of the cap. The plate would be large enough to cover
part of the amp so I could put a couple of screws into the amp enclosure.
For the fixed instrument, I see no problem putting the 0.4pf cap at
the end of the coax or wire, I would add a tie point on the tuning cap
and put my 0.4pf from the stator to the tie point and then the tie point
to the amp input.
For a portable amp it would be better inside the enclosure with about
6" of coax. I was think an isolated bnc, but I measured one and it has
2 pf of capacitance, so maybe just coax all the way into the enclosure
and the 0.4pf tacked on the center conductor.

A question for anyone, what are these connectors called?
> https://www.dropbox.com/s/iya29hus0tncexm/2001-12-31%2023.00.00.jpg?dl=0

Thanks, Mikek



If you do use coax, I would use a big, fat,

stiff coax with a low capacitance and low loss. I know it wouldn't be
much loss in a few inches of cable, but I was amazed at the small things
that would affect Kleijer's circuits including bushings on the variable
capacitors. So I can only imagine the coax materials will make a
difference.

---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus

 

[Joerg]

On 2017-03-25 18:39, rickman wrote:

On 3/25/2017 3:30 PM, Joerg wrote:
On 2017-03-25 10:49, rickman wrote:
On 3/24/2017 4:36 PM, Joerg wrote:
On 2017-03-24 10:59, rickman wrote:
On 3/24/2017 1:14 PM, Joerg wrote:
On 2017-03-20 02:06, Tauno Voipio wrote:

[...]

Please do not use PVC as RF insulation or support pieces.
It is lossy to extremely lossy at RF.


Plasticized PVC ain't stellar but not horrid.

http://g3ynh.info/zdocs/comps/part_6.html

Or do they add a lot of vispipuuro into the mix in Finland?

Are you reading the same page? It says PVC Tanδ is 0.04 - 0.14 at 1
MHz. That is in no way acceptable for the sort of high Q circuits
that
are being discussed. That's comparable to wood, 0.059.

This page even lists PVC in the "Lossy" group as defined by Tanδ ≥
0.01.


The losses in ferrite rods are nothing to sneeze at in comparison. I
have used both in ham radio a lot when I was young. I built kilowatt
level RF power amps, impedance matching boxes and similar gear. Ferrite
rods in transmitters sometimes became so hot that you could barely
touch
them while inductors wound on some random piece of PVC pipe remained
cool. I don't remember the PVC type other than that it was remnants
they
sold for pennies in the plumbing department so that was very likely
well
plasticized.

Maybe I don't recall the context of the ferrite, but the receiving
antennas in much of this thread and described in detail at Kleijer's web
site showed measurable losses with better plastics than PVC. Even
cardboard was a poor support relatively speaking. Seems he would use a
foam type plastic to get some rigidity with a minimum of loss. Foam PVC
was not bad, but his Q measurements increased significantly with foam
polypropylene. Obviously foam is better because there is less actual
material. Solid PVC would show more pronounced losses.

He does some amazingly detailed work. You might find it interesting.
The LC experiments were reported in a series of web pages. Page 10
doesn't have a link to page 11, but otherwise they are all chained.


Looks like there isn't a page 11.

That's what I was saying. There *is* a page 11, page 10 just doesn't
have a link to it. Go back to the index.

Indeed. I change the number in the URL by hand by starting with page 11
he change the URL structure. Well, I am not complaining, my web site
design skills aren't that great either.

http://www.crystal-radio.eu/enlctest.htm


He gets good Q with PVC. Worse with cardboard but who knows what kind of
stuff he used. It looks like carton material. That is often
post-consumer recycled and you never know what's in it. Water content is
another factor, got to bake it out and then lacquer it immediately
afterwards.

He gets good Q with FOAM PVC. Totally different from solid PVC, much
less of it and a lot more air. The point is foam anything else worked
even better.

Look at page 7. Very nice Q values except for the dirty pipe yet this is
all on regular PVC pipe.

The huge jump in Q in part 3 shows that he used the wrong measurement
setup until then. You can't do this sort of stuff with a 100:1 scope
probe, it has to be at least a high-end FET probe. However, hat off, he
achieved amazing Q values in his experiments.

Look at the Q values he gets in part 7. Those are all regular plumbing
PVC pipes. L16 has lower Q but that PVC tube isn't even particularly
clean. It is important to keep or make them pristine when building
high-Q stuff.


I found it very illuminating his tests with the variable capacitors.
Even parts like bushings were found to make a difference.


I remember that from my ham radio days. Dirty or oxidized rotor contacts
.... phssssst ... PHUT ... *BANG* and worst case that could take the
tubes into the abyss along with it. I also spent part of a Wenol
polishing paste tube keeping the final Pi-filter inductor shiny so it
wouldn't heat up too badly and unsolder a connection to it (which could
also result in a loud bang).

BTW, while such high Q isn't all that useful in practice if you ever
needed that there are simpler means to achieve it. An old method is the
"Q-multiplier". In essence the resonance circuit sits inside an
amplifier stage that is deliberately pulled very close to oscillation.
That shrinks the bandwidth big time.

How do you accomplish that without an amplifier? You did notice the
site is all about *crystal* radios, right?

You need an amplifier for that. If you want to you can make an
energy-harvesting one, sans battery. I mentioned this method purely as a
hint, in case anyone ever needs high Q without making fancy large coils
and babying them.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[John Devereux]

bill.sloman@ieee.org writes:

On Sunday, March 26, 2017 at 11:04:36 PM UTC+11, k...@notreal.com wrote:
On Sat, 25 Mar 2017 23:30:39 -0700, John Robertson <spam@flippers.com
wrote:

On 2017/03/25 6:26 PM, Jasen Betts wrote:
On 2017-03-25, Cursitor Doom <curd@notformail.com> wrote:
On Fri, 24 Mar 2017 15:31:03 +0000, Kevin Aylward wrote:

Of course, assuming the allegations are true, then the crimes are
horrendous, and would certainly warrant life in prison, with no
possibility of parole

A most costly decision. Do you have any idea how much it costs to
incarcerate a prisoner in that category for that length of time?

Last I Heard it was cheaper than death row.


We have
an overcrowding crisis right now because the system is clogged up by 'bed-
blockers' who could easily be removed at zero further cost to the
taxpayer.

Letting them out seems kind of recklesxs

Part of the problem appears to be that the USA locks up more people per
capita than any other developed nation.

Why?

Because we have more criminals. Duh! The left has made a permanent
underclass of losers.

Top 10 US states by incarceration rate:

Louisiana, Oklahoma, Mississippi, Alabama, Georgia, Texas, Arizona,
Arkansas, Florida.

Left wing liberals all..

Not actually true.

h ttps://en.wikipedia.org/wiki/United_States_incarceration_rate

suggests that the higher incarceration rate isn't due to a larger
number of criminals, but rather a sentencing system that puts them
into prison with longer sentences. The wikipedia article does provide
links to a more detailed discussion of this point, but since krw isn't
going to change what he thinks merely because the facts don't support
him, there's not a lot of point in providing more information.

There seem to be several reasons from what I have read about it, and
they reinforce each other to produce the current woeful result

Longer sentences as you say.

Privatisation of the prison and parole systems, such that there is a
strong incentive to maximise profits by churning out hardened
criminals. This industry also lobbies for laws designed to incarcerate
yet more.

Public arrest records such that pre-employment "background checks" are
easy and routine. Meaning that simply being arrested can blight your
prospects for life. And making it hard to avoid a life of crime or
dependency once touched by "the system".

"How to arrest-proof yourself" by Dale Carson is an entertaining read
about this, by an ex cop (and lawyer).

https://www.amazon.com/Arrest-Proof-Yourself-Ex-Cop-Reveals-Arrested/dp/1556526377

--

John Devereux

 

[amdx]

On 3/26/2017 9:34 AM, amdx wrote:

On 3/26/2017 4:36 AM, rickman wrote:
On 3/26/2017 5:00 AM, amdx wrote:
On 3/25/2017 11:00 PM, rickman wrote:
On 3/25/2017 11:42 PM, amdx wrote:
On 3/25/2017 8:32 PM, rickman wrote:
On 3/25/2017 9:10 PM, amdx wrote:
On 3/25/2017 5:25 PM, dagmargoodboat@yahoo.com wrote:
On Saturday, March 25, 2017 at 3:20:31 PM UTC-4, rickman wrote:
On 3/25/2017 2:33 PM, dagmargoodboat@yahoo.com wrote:

Summary:
o The FET-as-voltage follower has a gain of 0.98, which is quite
decent for our purposes.
o Input capacitance is 1.2pF.
o We've reduced the input capacitance by a factor of about 4
compared
to Kleijer, but it's still not as low as expected.

The shield driver + BNC isn't going to work, not until we get the
gain closer
to 1, rather than 0.25.

The gain of 0.25 is not because of the voltage follower, it's from
the
series cap.

The net gain's a result of the *divider* formed by the series
coupling
cap
and (the FET input capacitance + strays), multiplied by the
follower
gain.
I asked Mike to measure the follower gain so we could then
calculate
the
input capacitance.

Are you suggesting you can get the amp input capacitance
down to 10x less than the series cap?

Bootstrapping should reduce the FET input capacitance by a
factor of
1/(1-G), where G = the gain of the bootstrap.

Another approach would be to put the series cap outside the box in
the
probe tip as is done in o'scopes. Then the gain of the amp
would be
sufficient to tie the coax shield to the output of the amp.

That's true. Mike could use a shielded connector and cable if he
didn't
mind putting his series cap at the probe.

The plan is to permanently wire the coax end to the tuning cap, and
then
swap different coils to it.
I was about to say that a series cap at the probe not a good plan,
but I
could put some type of permanent connection on my tuning cap to hold
the
0.4pf cap and the connect the coax to that. I suspect I'd be adding
capacitance with that though.

If you add the 0.4 pF cap with the coax on the amplifier side of the
cap, you will be adding 0.4 pF capacitance maximum. If you add the
coax
without the cap or put the cap on the amplifier end of the coax
without
the amplifier driving the shield, you will likely be adding a lot
more
than 0.4 pF.

Why do you want to add the coax permanently?

I don't care if it is coax or a pair of wires. I want a battery
operated fixed testing setup. The 50 ohm output will after a peak
detector or demodulator and then a meter, may need a log amp. With
it I
could compare the output of different ferrite antennas. I could
drive an
antenna with my sig/gen and measure Q using the 3 db method, etc.

Ok, I understand now. I wasn't getting that this is a test
fixture. It
will never be operated without the amp. Where you put the captive coax
doesn't matter then.

Since your series cap can be made pretty consistently, I would suggest
adding it to the fixture before the coax. Then the entire coax and
amplifier capacitance impacts to the test fixture will be minimized
regardless of how well you can mitigate the capacitance through the
bootstrap circuit.

If you need another cap for another type of test, you can hole punch
another fairly easily and it should have pretty much the same
capacitance. One advantage of having a significantly larger
capacitance
at the amp input is that it will have less impact on the end to end
gain
if it varies.

How long a cable will you use? By that I mean how many pF?


I have no understanding of how putting the 0.4pf cap at the end of the
coax makes it easier to cancel. I probably need to go back and read
the thread.

What I meant was, the point of adding the 0.4 pF cap in line is to limit
the capacitance seen by the device being measured. If you leave off the
cap the device being tested sees the entire capacitance of the measuring
device. If you add the cap in front of all the added capacitance the
device being measured only sees the combination which will always be
less than the 0.4 pF cap (series capacitors combine like parallel
resistances, 1/Ctot = 1/C + 1/C2).

If you put the cap at the end of the coax right next to the unit you are
testing, then all capacitance after that point is isolated so the unit
doesn't "see" it. That's the advantage of putting it there.

Great, now I see the reasoning.


This does nothing about the impact of the added capacitance of the coax
and the input capacitance of the amp in terms of affecting the amplitude
of the signal. The larger this capacitance, the more the signal is
attenuated at the input of the amp. So it will help the gain of the
overall amp circuit to reduce the input capacitance of the amp.

That said... Since you can add gain after the input stage, why exactly
is it important to reduce the impact of the amplifier input capacitance
to nearly nothing?

The only importance would be, you would not need to retune after adding
the amp to an LC. Doesn't affect a fixed instrument, unless
you have calibrated tuning cap.
Also, if the amps input capacitance was lossy like having a cap with
poor bushing connection, this would lower Q.
And, it would be neat to have an instrument that when connected has no
measurable effect on the circuit under test.


The original amp had a voltage loss of 17:1 from the
capacitance voltage divider, if I am reading it all correctly. This is
now reduced to 4:1. When you add the capacitance of a coax to the
circuit the voltage divider ratio will go back up significantly.

I would try to minimize the length of the coax to minimize the
capacitance. If you can improve the bootstrapping of the circuit that
will be great. But when you reach the limit of what it will do, it will
be easy enough to set the gain of the following stages to make the
overall gain what you want, which is 1. I think it will be more
important to construct this so the gain is stable rather than trying to
get the gain of the first stage to be as close to 1 as possible.


Re, how many pf of coax, I was thinking maybe 6 inches of RG58, maybe
13pf. This a question of component layout to minimize losses. However,
it look to me like I could just set the tuning capacitor on top of the
amplifier housing, Probably even have physical contact between the
stator frame and the amp housing. That would only leave a 2-1/2" wire to
connect the amp input pin the the rotor tab on the capacitor.
Here is a picture of my first thought.
https://www.dropbox.com/s/ifgklgfxavb7ash/Cap%20and%20amp%20connections.jpg?dl=0



Ignore the added trim cap, it was needed for a test. Although I will
probably include the trim cap, but I will mount it forward about an
inch.
The trim cap was too big and I had to remove six plates, I'll
probably remove at least one more, as it was still hard to peak
some of my coils.

I would say the mounting looks like a good idea. I'm not sure I would
bother with a coax. I'd use a stiffer wire so it is less likely to
bend, maybe 14 gauge. As it moves around it changes the capacitance
which changes the gain.

If I do mount the cap and amp like that, I would make an aluminum
plate similar to the one holding the trim cap, but reaching both screws
near the bottom of the cap. The plate would be large enough to cover
part of the amp so I could put a couple of screws into the amp enclosure.
For the fixed instrument, I see no problem putting the 0.4pf cap at the
end of the coax or wire, I would add a tie point on the tuning cap and
put my 0.4pf from the stator to the tie point and then the tie point to
the amp input.
For a portable amp it would be better inside the enclosure with about
6" of coax. I was think an isolated bnc, but I measured one and it has
2 pf of capacitance, so maybe just coax all the way into the enclosure
and the 0.4pf tacked on the center conductor.

A question for anyone, what are these connectors called?
https://www.dropbox.com/s/iya29hus0tncexm/2001-12-31%2023.00.00.jpg?dl=0

Thanks, Mikek



If you do use coax, I would use a big, fat,
stiff coax with a low capacitance and low loss. I know it wouldn't be
much loss in a few inches of cable, but I was amazed at the small things
that would affect Kleijer's circuits including bushings on the variable
capacitors. So I can only imagine the coax materials will make a
difference.

I setup my existing amplifier with my Boonton 260 Q meter to measure
the input capacitance of the amp. The lead wires are about 1" long.
The Boonton has a fine trim capacitor marked it 1/10 pf divisions.
I peaked the Q reading, then added the amplifier. I had to decrease
the value of the fine trim capacitor by just slightly over 1pf (1.025pf).
After adding the amp and readjusting for peak Q the Q was reduced
from approximately 1300 to 1276.
The capacitance was lower than I expected and the loss of Q is more
than desirable.
Here's a picture of the amp on the Boonton with leads.
> https://www.dropbox.com/s/767k85740ijv93p/2001-12-31%2023.00.00-135.jpg?dl=0

Mikek





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[rickman]

On 3/26/2017 10:34 AM, amdx wrote:

On 3/26/2017 4:36 AM, rickman wrote:
On 3/26/2017 5:00 AM, amdx wrote:

I have no understanding of how putting the 0.4pf cap at the end of the
coax makes it easier to cancel. I probably need to go back and read
the thread.

What I meant was, the point of adding the 0.4 pF cap in line is to limit
the capacitance seen by the device being measured. If you leave off the
cap the device being tested sees the entire capacitance of the measuring
device. If you add the cap in front of all the added capacitance the
device being measured only sees the combination which will always be
less than the 0.4 pF cap (series capacitors combine like parallel
resistances, 1/Ctot = 1/C + 1/C2).

If you put the cap at the end of the coax right next to the unit you are
testing, then all capacitance after that point is isolated so the unit
doesn't "see" it. That's the advantage of putting it there.

Great, now I see the reasoning.


This does nothing about the impact of the added capacitance of the coax
and the input capacitance of the amp in terms of affecting the amplitude
of the signal. The larger this capacitance, the more the signal is
attenuated at the input of the amp. So it will help the gain of the
overall amp circuit to reduce the input capacitance of the amp.

That said... Since you can add gain after the input stage, why exactly
is it important to reduce the impact of the amplifier input capacitance
to nearly nothing?

The only importance would be, you would not need to retune after adding
the amp to an LC. Doesn't affect a fixed instrument, unless
you have calibrated tuning cap.
Also, if the amps input capacitance was lossy like having a cap with
poor bushing connection, this would lower Q.
And, it would be neat to have an instrument that when connected has no
measurable effect on the circuit under test.

Ok, please go back to the section above and consider what you are saying
here. The purpose of the input cap is to isolate the entire amplifier
from the circuit being measured. Because this cap reduces the current
to very low values there won't be much impact to the Q. Yes, there will
always be some and this can be minimized.

Ignore the added trim cap, it was needed for a test. Although I will
probably include the trim cap, but I will mount it forward about an
inch.
The trim cap was too big and I had to remove six plates, I'll
probably remove at least one more, as it was still hard to peak
some of my coils.

I would say the mounting looks like a good idea. I'm not sure I would
bother with a coax. I'd use a stiffer wire so it is less likely to
bend, maybe 14 gauge. As it moves around it changes the capacitance
which changes the gain.

If I do mount the cap and amp like that, I would make an aluminum
plate similar to the one holding the trim cap, but reaching both screws
near the bottom of the cap. The plate would be large enough to cover
part of the amp so I could put a couple of screws into the amp enclosure.
For the fixed instrument, I see no problem putting the 0.4pf cap at the
end of the coax or wire, I would add a tie point on the tuning cap and
put my 0.4pf from the stator to the tie point and then the tie point to
the amp input.
For a portable amp it would be better inside the enclosure with about
6" of coax. I was think an isolated bnc, but I measured one and it has
2 pf of capacitance, so maybe just coax all the way into the enclosure
and the 0.4pf tacked on the center conductor.

If you don't like 2 pF from the connector, you are going to hate the
capacitance from the coax. Driving it from the output of the first
stage amp will help minimize it, but even better is to isolate it with
the input cap at the probe end of the coax. Get the benefit of both
effects. Not to mention the losses in the coax.

Actually, I think it is the test fixture where the capacitance is not so
important. The variable cap is part of the test fixture, no? So the
capacitance added by the coax is just part of the capacitance of the
test fixture adding to the base capacitance of the variable cap. With
such a large range a couple of added pF won't impact the range
significantly will it? Since it is part of the test fixture the added
capacitance will be the same for all measurements and is adjusted out
when you tune.

A question for anyone, what are these connectors called?
https://www.dropbox.com/s/iya29hus0tncexm/2001-12-31%2023.00.00.jpg?dl=0

Try searching on "bakelite electronic soldering strips" or "bakelite
soldering lug strips". Actually I like your 3D soldering. Can't get
any lower capacitance.

--

Rick C

 

[rickman]

On 3/26/2017 10:35 AM, Joerg wrote:

On 2017-03-25 18:39, rickman wrote:
On 3/25/2017 3:30 PM, Joerg wrote:
On 2017-03-25 10:49, rickman wrote:
On 3/24/2017 4:36 PM, Joerg wrote:
On 2017-03-24 10:59, rickman wrote:
On 3/24/2017 1:14 PM, Joerg wrote:
On 2017-03-20 02:06, Tauno Voipio wrote:

[...]

Please do not use PVC as RF insulation or support pieces.
It is lossy to extremely lossy at RF.


Plasticized PVC ain't stellar but not horrid.

http://g3ynh.info/zdocs/comps/part_6.html

Or do they add a lot of vispipuuro into the mix in Finland?

Are you reading the same page? It says PVC Tanδ is 0.04 - 0.14 at 1
MHz. That is in no way acceptable for the sort of high Q circuits
that
are being discussed. That's comparable to wood, 0.059.

This page even lists PVC in the "Lossy" group as defined by Tanδ ≥
0.01.


The losses in ferrite rods are nothing to sneeze at in comparison. I
have used both in ham radio a lot when I was young. I built kilowatt
level RF power amps, impedance matching boxes and similar gear.
Ferrite
rods in transmitters sometimes became so hot that you could barely
touch
them while inductors wound on some random piece of PVC pipe remained
cool. I don't remember the PVC type other than that it was remnants
they
sold for pennies in the plumbing department so that was very likely
well
plasticized.

Maybe I don't recall the context of the ferrite, but the receiving
antennas in much of this thread and described in detail at Kleijer's
web
site showed measurable losses with better plastics than PVC. Even
cardboard was a poor support relatively speaking. Seems he would use a
foam type plastic to get some rigidity with a minimum of loss. Foam
PVC
was not bad, but his Q measurements increased significantly with foam
polypropylene. Obviously foam is better because there is less actual
material. Solid PVC would show more pronounced losses.

He does some amazingly detailed work. You might find it interesting.
The LC experiments were reported in a series of web pages. Page 10
doesn't have a link to page 11, but otherwise they are all chained.


Looks like there isn't a page 11.

That's what I was saying. There *is* a page 11, page 10 just doesn't
have a link to it. Go back to the index.


Indeed. I change the number in the URL by hand by starting with page 11
he change the URL structure. Well, I am not complaining, my web site
design skills aren't that great either.


http://www.crystal-radio.eu/enlctest.htm


He gets good Q with PVC. Worse with cardboard but who knows what kind of
stuff he used. It looks like carton material. That is often
post-consumer recycled and you never know what's in it. Water content is
another factor, got to bake it out and then lacquer it immediately
afterwards.

He gets good Q with FOAM PVC. Totally different from solid PVC, much
less of it and a lot more air. The point is foam anything else worked
even better.


Look at page 7. Very nice Q values except for the dirty pipe yet this is
all on regular PVC pipe.

Compared to what? He is comparing coil winding methods. What would the
Q be with other supports?

The huge jump in Q in part 3 shows that he used the wrong measurement
setup until then. You can't do this sort of stuff with a 100:1 scope
probe, it has to be at least a high-end FET probe. However, hat off, he
achieved amazing Q values in his experiments.

Look at the Q values he gets in part 7. Those are all regular plumbing
PVC pipes. L16 has lower Q but that PVC tube isn't even particularly
clean. It is important to keep or make them pristine when building
high-Q stuff.


I found it very illuminating his tests with the variable capacitors.
Even parts like bushings were found to make a difference.


I remember that from my ham radio days. Dirty or oxidized rotor contacts
.... phssssst ... PHUT ... *BANG* and worst case that could take the
tubes into the abyss along with it. I also spent part of a Wenol
polishing paste tube keeping the final Pi-filter inductor shiny so it
wouldn't heat up too badly and unsolder a connection to it (which could
also result in a loud bang).

BTW, while such high Q isn't all that useful in practice if you ever
needed that there are simpler means to achieve it. An old method is the
"Q-multiplier". In essence the resonance circuit sits inside an
amplifier stage that is deliberately pulled very close to oscillation.
That shrinks the bandwidth big time.

How do you accomplish that without an amplifier? You did notice the
site is all about *crystal* radios, right?


You need an amplifier for that. If you want to you can make an
energy-harvesting one, sans battery. I mentioned this method purely as a
hint, in case anyone ever needs high Q without making fancy large coils
and babying them.

What energy will be harvested?

--

Rick C

 

[Julian Barnes]

Juddge Janeine tells Paul ryan to "get the fuck outa da House!"

https://youtu.be/cChG52Zpedc

somethig we can _all_ agree on for once lol!

 

[Larry Sheldon]

On 3/26/2017 22:01, Sylvia Else wrote:

On 27/03/2017 12:39 PM, Larry Sheldon wrote:
On 3/25/2017 23:35, Sylvia Else wrote:
On 26/03/2017 3:34 PM, Sylvia Else wrote:
I'm using this circuit to provide 250V pulses to an ignition coil.


Oops - sorry - wrong group.
ACKKKK! That is cruel!

What is the right group? Interesting question.

sci.electronics.design is where I intended to post (and have now). No
explanation has been forthcoming. Which is a nuisance, since this is
intended to the electronic ignition system for a generator I'm trying to
restore to function for use during rolling blackouts that we seem at
increasing risk of getting in the summer, here in third world Sydney,
Australia.

If I can't understand the behaviour, then I can't trust it to work when
the day comes, and I'll have to redesign/rebuild it.

I have no for-sure-useful information, but it did pique my interest.

I filter as lot of stuff and my provider filters a lot of stuff, so I
went to Google Groups and into the swamp to see if I could find a link
to you and I did see that somebody HAD replied to comp.misc with
interesting (to me) questions.




--
quis custodiet ipsos custodes?
-- Juvenal

 

[Larry Sheldon]

On 3/26/2017 01:33, Sylvia Else wrote:

On 26/03/2017 4:33 PM, John Larkin wrote:
On Sun, 26 Mar 2017 15:36:06 +1100, Sylvia Else
sylvia@not.at.this.address> wrote:

I'm using this circuit to provide 250V pulses to an ignition coil.

https://www.dropbox.com/s/1w33uss3eedem05/ignition2.pdf?dl=0

The IC is a Linear Technology LT1243.

12V is provided on G$1 to the left. G$2 accepts a trigger pulse, and G$3
is ground.

LTSpice says that this works, and indeed the real implementation does.
Mostly.

The difference is that after the circuit has been triggered once, it
won't charge the capacitor again (above about 25 volts) for a varying
period that can be up to half a minute. It's as if the wrong level is
being used internally to compare with the feedback pin. In that regard,
I'll mention that Q3 is used to pull FB up so that the circuit stops
driving the FET, since otherwise the SCR never turns off. I've checked,
and the problem is not that Q3 remains on, nor is it that the SCR fails
to turn off. In any case, the 1.5uF capacitor C1 does get charged
somewhat, as I mentioned above.

When the issue resolves, it does so rapidly, within a fraction of a
second.

Connecting an oscilloscope probe to the RT/CT pin of the IC restores
function, but only if the scope is set to DC coupling - not AC coupling
- and functioning continues only as long as the probe remains connected
- until the aforesaid varying period has elapsed. Touching the pin with
a finger has a similar effect.

That is, connect probe; works. Disconnect; stops working. Reconnect;
works, etc. until eventually it starts working continuously.

This cannot be capacitive loading - there's already a significant
capacitance between RT/CT and ground.

The fact that the coupling has to be DC made me think that some small
current was flowing to ground through the scope, so I bridged C4 with a
100K resistor. It didn't make any difference.

I tried changing the IC (a pain, given that it's surface mounted), but
again it made no difference.

Any other ideas about what might be happening here.

Sylvia.

Just possibly the SCR is staying on, shorts the inverter, which
thermal limits, and recovers later? It's awfully complex.

I don't see any sign of that - the voltage across the coil is zero at
this point, whereas the capacitor C1 has about 25V across it, dropping
to zero each time the circuit is triggered, and then climbing back toe
25V. The scope shows a few steps, as it gets pumped to there, but it
doesn't continue upwards.



Back when it wasn't so lethal to ride motorcycles on the street (and I
wasn't too bright) I use to make my own CD ignitions.

I liked this topology

https://dl.dropboxusercontent.com/u/53724080/Circuits/Power/CDI.jpg

because it was easy to drive the SCR gate with a simple RC circuit
from the points. A low value resistor from gate to ground ensures
turnoff. You could elect to kill the boost converter during the gate
pulse, too.

To get a fat spark, you need a pretty wide SCR gate pulse, to let the
whole mess ring a few cycles. I usually ran around 80 to 100 mJ per
spark, which will fire a plug no matter how fouled. Barely needs
gasoline.

Looks like I'm using a bit under 50mJ, which seems to be working, albeit
with a plug in reasonable condition.


Actually, my HV supplies were open-loop 2-transistor DC/DC converters
with full bridge rectifiers. It sort of relaxed for a while after
being shorted, then started oscillating again, which was nice.



My application is the engine of a generator. It doesn't have points, but
has some magnet/coil arrangement that produces a pulse at the correct
point in the cycle.

I just sortakinda fell into this thread and I do not have the
credentials to be jumping in, but I do have to say that that that
"magnet/coil arrangement" is called a "magneto" on the backyard and
shade-tree mechanic circuits I used to hand on, and it puts out a
shocking pulse tall enough to fire a plug on a good day.

Certainly charging through the coil simplifies things, but I had/have no
idea what the inductance of the coil might be. Indeed, it turned out
that my coil had insulation failure in the HT side, and I had to source
a new one, so even if I'd tried to measure the old one, the new one
could have been different.

Finally got the engine running today, using this ignition circuit, and
LPG, after many hours spent cursing a PIC32MX that I was temporarily
using to generate the trigger pulse - got caught out by yet another PIC
errata - input capture doesn't work when the processor is in the idle
state.

Sylvia.

--
quis custodiet ipsos custodes?
-- Juvenal

 

[Sylvia Else]

On 27/03/2017 4:54 PM, Larry Sheldon wrote:

On 3/26/2017 01:33, Sylvia Else wrote:

My application is the engine of a generator. It doesn't have points, but
has some magnet/coil arrangement that produces a pulse at the correct
point in the cycle.

I just sortakinda fell into this thread and I do not have the
credentials to be jumping in, but I do have to say that that that
"magnet/coil arrangement" is called a "magneto" on the backyard and
shade-tree mechanic circuits I used to hand on, and it puts out a
shocking pulse tall enough to fire a plug on a good day.

There are such things, but this is not that. As originally supplied it
was an ordinary capacitive discharge ignition. There's a separate
winding that produces the power used to energise the capacitor, and then
this magnet and coil device is used to produce a pulse that triggers the
discharge into the coil.

Sylvia.

 

[Jasen Betts]

On 2017-03-26, amdx <nojunk@knology.net> wrote:

On 3/26/2017 4:36 AM, rickman wrote:

A question for anyone, what are these connectors called?
https://www.dropbox.com/s/iya29hus0tncexm/2001-12-31%2023.00.00.jpg?dl=0

tag strip

--
This email has not been checked by half-arsed antivirus software

 

On Sunday, March 26, 2017 at 2:33:13 AM UTC-4, Sylvia Else wrote:

Finally got the engine running today, using this ignition circuit, and
LPG, after many hours spent cursing a PIC32MX that I was temporarily
using to generate the trigger pulse - got caught out by yet another PIC
errata - input capture doesn't work when the processor is in the idle state.

Sylvia.

Was that PIC quirk the problem? Otherwise, I'd ask
o Whether C4 might be bad, open, or the wrong value?

Or, that not being the case, maybe the LT1243's upset about having its
FB pin pulled all the way to +5v (wind-up?)?

Is the LT1243's Vref getting glitched from your reset circuit, upsetting
the LT?

Just some wild ideas. From your description it really sounds like it's
RT/CT pin-related, and you've already put your finger on it (so to speak .

Cheers,
James Arthur