Driver to drive?

[George Herold]

On Friday, March 17, 2017 at 8:47:09 PM UTC-4, John Larkin wrote:

On Fri, 17 Mar 2017 17:31:46 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Friday, March 17, 2017 at 11:38:44 AM UTC-4, Phil Hobbs wrote:
On 03/17/2017 11:28 AM, George Herold wrote:
On Friday, March 17, 2017 at 10:30:32 AM UTC-4, John Larkin wrote:
On Thu, 16 Mar 2017 18:46:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, March 16, 2017 at 8:36:16 PM UTC-4, Phil Allison wrote:
George Herold wrote:



I've got an AM radio that came with an air core antenna.
(1990's vintage)
~4" (10 cm) squarish loop. Not sure how many turns.
Works fine.


** So it's an external loop for a main powered receiver ?

Right, It's a JVC "ultra compact component system"
FS-1000


** So why didn't you post that info before?

'cos I'm now at home and not at work.
It's a fucking frame antenna, already discussed here in this thread and been around since the dawn of radio.



Knowing almost nothing about AM, (and assuming I don't care about price.)
I figure I want the highest Q possible on the front end..


** Nope.

You need at least 10kHz of bandwidth at the antenna so the Q must not exceed 50 to 100 across the AM band. You will find that antenna has a fairly low Q in practice.
OK I was thinking of best signal to noise, and figuring that ~1-2 kHz would
be enough.. Everyones "best/ optimal" is a bit different.

An AM antenna doesn't need to be tuned at all. An untuned coil will
snoop the ambient h-field.
I guess that's right. As long as most of the noise is "in the air" it doesn't
really matter where the band pass filter is. (Except for dynamic range issues.)

As you say, dynamic range. An untuned input needs a stronger mixer. A
Q of 10 or 20 would help a lot.

On the other hand, one could just use a Mini Circuits mixer with a +17
dBm LO, or a nice analogue mux with square wave drive. It takes a lot
to screw one of those up.
Hah, I made an AM radio just that way. Not with a loop, but just
a length of wire. (It's probably the worlds's worst AM radio.)
I had to add series L's (selected for range) to make it work.
Circuit from Terman's radio electronics book.

So a loop (with parallel C) into a TIA? ... (I'd rather use an opamp.)
or will that wig out at the C side of the resonance?


A short wire antenna gets a voltage equal to the local e-field. All
you need to do is drive an amp with reasonably low input capacitance,
like a jfet or something.
Oh no my mistake, I was thinking of how to couple in from a loop.

George H.

I could patent that, but it's been done for 100 years or so.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[George Herold]

On Friday, March 17, 2017 at 9:09:26 PM UTC-4, dagmarg...@yahoo.com wrote:

On Friday, March 17, 2017 at 8:36:33 PM UTC-4, George Herold wrote:
On Friday, March 17, 2017 at 8:13:13 PM UTC-4, dagmarg...@yahoo.com wrote:
On Friday, March 17, 2017 at 7:33:04 PM UTC-4, Clifford Heath wrote:
On 18/03/17 06:21, John Larkin wrote:
Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

A perfect application for Y5V / Z5U / X5R ceramic caps. 2uF varicap? Can do!


Oh boy! Can't wait... how do you feed the drive in?
I've always pictured two caps driven in the middle.

That's typical. Varicaps are usually used back-to-back, or with a d.c.
blocking cap.

Cheers,
James Arthur

Right, I'm only a tadpole, circuit-wise.
George H.

 

[Clifford Heath]

On 18/03/17 06:21, John Larkin wrote:

Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

 

[Clifford Heath]

On 18/03/17 02:38, Phil Hobbs wrote:

On 03/17/2017 11:28 AM, George Herold wrote:
On Friday, March 17, 2017 at 10:30:32 AM UTC-4, John Larkin wrote:
An AM antenna doesn't need to be tuned at all. An untuned coil will
snoop the ambient h-field.
I guess that's right. As long as most of the noise is "in the air" it doesn't
really matter where the band pass filter is. (Except for dynamic range issues.)
As you say, dynamic range. An untuned input needs a stronger mixer. A
Q of 10 or 20 would help a lot.

On the other hand, one could just use a Mini Circuits mixer with a +17
dBm LO, or a nice analogue mux with square wave drive. It takes a lot
to screw one of those up.

The SA612 gives you oscillator and 14dB gain mixer in an 8-pin package,
for a buck. Good to 200MHz LO.

 

[John Larkin]

On Sat, 18 Mar 2017 10:32:58 +1100, Clifford Heath
<no.spam@please.net> wrote:

On 18/03/17 06:21, John Larkin wrote:
Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

You can get varicaps up to about 100 pF. To resonate in the AM band,
having a ferrite core would help get enough inductance.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Fri, 17 Mar 2017 17:13:05 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Friday, March 17, 2017 at 7:33:04 PM UTC-4, Clifford Heath wrote:
On 18/03/17 06:21, John Larkin wrote:
Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

A perfect application for Y5V / Z5U / X5R ceramic caps. 2uF varicap? Can do!

Cheers,
James Arthur

Good point.

Somebody makes a thing like a varicap, for tuning, but it's actually a
ceramic dielectric thing.

I was always impressed by the tapered curvey variable multi-plate caps
in old radios, how they got the antenna tuning and LO to track. They
did that without computers!

My 600 MHz oscillator needs +-125 fF pF capacitance range to tune. I'm
using a Skyworks dual back-to-back varicap, one side grounded, the
other on the resonator, the tune voltage in the middle.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Fri, 17 Mar 2017 17:31:46 -0700 (PDT), George Herold
<gherold@teachspin.com> wrote:

On Friday, March 17, 2017 at 11:38:44 AM UTC-4, Phil Hobbs wrote:
On 03/17/2017 11:28 AM, George Herold wrote:
On Friday, March 17, 2017 at 10:30:32 AM UTC-4, John Larkin wrote:
On Thu, 16 Mar 2017 18:46:06 -0700 (PDT), George Herold
gherold@teachspin.com> wrote:

On Thursday, March 16, 2017 at 8:36:16 PM UTC-4, Phil Allison wrote:
George Herold wrote:



I've got an AM radio that came with an air core antenna.
(1990's vintage)
~4" (10 cm) squarish loop. Not sure how many turns.
Works fine.


** So it's an external loop for a main powered receiver ?

Right, It's a JVC "ultra compact component system"
FS-1000


** So why didn't you post that info before?

'cos I'm now at home and not at work.
It's a fucking frame antenna, already discussed here in this thread and been around since the dawn of radio.



Knowing almost nothing about AM, (and assuming I don't care about price.)
I figure I want the highest Q possible on the front end..


** Nope.

You need at least 10kHz of bandwidth at the antenna so the Q must not exceed 50 to 100 across the AM band. You will find that antenna has a fairly low Q in practice.
OK I was thinking of best signal to noise, and figuring that ~1-2 kHz would
be enough.. Everyones "best/ optimal" is a bit different.

An AM antenna doesn't need to be tuned at all. An untuned coil will
snoop the ambient h-field.
I guess that's right. As long as most of the noise is "in the air" it doesn't
really matter where the band pass filter is. (Except for dynamic range issues.)

As you say, dynamic range. An untuned input needs a stronger mixer. A
Q of 10 or 20 would help a lot.

On the other hand, one could just use a Mini Circuits mixer with a +17
dBm LO, or a nice analogue mux with square wave drive. It takes a lot
to screw one of those up.
Hah, I made an AM radio just that way. Not with a loop, but just
a length of wire. (It's probably the worlds's worst AM radio.)
I had to add series L's (selected for range) to make it work.
Circuit from Terman's radio electronics book.

So a loop (with parallel C) into a TIA? ... (I'd rather use an opamp.)
or will that wig out at the C side of the resonance?

A short wire antenna gets a voltage equal to the local e-field. All
you need to do is drive an amp with reasonably low input capacitance,
like a jfet or something.

I could patent that, but it's been done for 100 years or so.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Cursitor Doom]

On Fri, 17 Mar 2017 22:47:12 -0400, krw wrote:

I don't recall anything like that, either. Perhaps because I came out
of it more slowly? I've also had a few quicky anasthesias for
cardioversions (basically a defib with the paddles glued to the chest
and back) and woke uf form those not even realizing that I'd been out
and it was already done, though the burns on my chest did let me know
that something happened (300J does that).

As this Darwin Award nominee found out:

http://www.bbc.co.uk/news/uk-39307418

 

On Sat, 18 Mar 2017 10:32:58 +1100, Clifford Heath
<no.spam@please.net> wrote:

On 18/03/17 06:21, John Larkin wrote:
Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

The 1-5 MHz tuning range with a single inductor would need a 25:1
_total_ capacitive range. Since there are stray capacitances, the
actual tuning range for the varactor itself would be even greater.

Thus, you might have to switch the inductance even once in that 1-5
MHz range.

One problem with varactors is that the maximum capacitance occurs at
very low reverse voltages, in some cases in the same order of
magnitude as the RF, causing detuning. Two varactors connected against
each other helps with this.

 

[Tim Williams]

"Clifford Heath" <no.spam@please.net> wrote in message
news:58cc722c$0$51765$c3e8da3$f6268168@news.astraweb.com...

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

Sounds like a horrible case of poorly matched transformer design.
(Unusually badly matched: Q's in the thousands imply impedance off by at
least as much!)

Impossible to say for sure without a winding stackup, though. *shrug*

Tim

--
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Contract Design
Website: http://seventransistorlabs.com

 

On Wednesday, 15 March 2017 01:58:40 UTC, Jim Thompson wrote:

"Procedure" tomorrow (Wednesday) at 11:00AM:

Down the throat with a scope, check out the stomach, then into the
small intestine, use side-looking ultrasound on the end of the probe
(didn't know such a thing existed) to examine the common pancreas/bile
duct, go up it with a wire, then thread a balloon up that wire,
inflate and decimate the stones, then go on up and examine the gall
bladder.

Possible later procedure, after the nauseous, tiredness, yellowness
abates, go in thru an incision and remove the gall bladder.

Such fun >:-}

If I don't show up in a day or too...

...Jim Thompson

Where/how is Jim?


NT

 

[Cursitor Doom]

On Sat, 18 Mar 2017 09:49:00 -0400, bitrex wrote:

I had it once for a complex third molar extraction - I remember being
hooked up to the IV and they gave me some oxygen and then just sitting
there awake waiting and waiting.

Dentist walks in and asks me how I'm doing.

"Fine I guess, is anything wrong? Are we going to do the surgery?"

She laughs - it's already all done, you're in recovery, silly.

Oh, okay! Alright then.

Now *that's* the way to go! :-D
Wonder how Jim got on?

 

[Tauno Voipio]

On 18.3.17 02:28, John Larkin wrote:

On Fri, 17 Mar 2017 17:13:05 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Friday, March 17, 2017 at 7:33:04 PM UTC-4, Clifford Heath wrote:
On 18/03/17 06:21, John Larkin wrote:
Resonating an AM antenna needs a giant variable cap, or a varicap and
some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had
to tune 1-5MHz, and used 480(!) small varicaps. It was measuring
micro-ohms of dynamic impedance using transformer coupling
(about 8mm square) across a small air gap. The DUT had dozens
of resonances with Q of 1000-5000 across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

A perfect application for Y5V / Z5U / X5R ceramic caps. 2uF varicap? Can do!

Cheers,
James Arthur

Good point.

Somebody makes a thing like a varicap, for tuning, but it's actually a
ceramic dielectric thing.

I was always impressed by the tapered curvey variable multi-plate caps
in old radios, how they got the antenna tuning and LO to track. They
did that without computers!

My 600 MHz oscillator needs +-125 fF pF capacitance range to tune. I'm
using a Skyworks dual back-to-back varicap, one side grounded, the
other on the resonator, the tune voltage in the middle.

The outer rotor plates of the ganged variable caps were slotted, so
it was possible to fine-tune the tracking, but it was pretty tedious.

--

-TV

 

On Friday, March 17, 2017 at 10:47:17 PM UTC-4, k...@notreal.com wrote:

On Sat, 18 Mar 2017 00:46:33 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Thu, 16 Mar 2017 22:22:33 -0400, krw wrote:

Nothing like that. I knew the surgery would be bad but it wasn't nearly
as bad as they said.

I find coming round after the op is the worst part. It's not like normal
waking up. I panic like hell! "Where am I? What the fuck happened? What
are all these fucking tubes for?" That kind of thing. Nasty!

I don't recall anything like that, either. Perhaps because I came out
of it more slowly? I've also had a few quicky anasthesias for
cardioversions (basically a defib with the paddles glued to the chest
and back) and woke uf form those not even realizing that I'd been out
and it was already done, though the burns on my chest did let me know
that something happened (300J does that).

What a waste of electricity!

 

[Cursitor Doom]

On Sat, 18 Mar 2017 10:50:10 -0400, krw wrote:

http://www.roadsideamerica.com/story/7814

In your case, I'd pay gladly for the electricity.

Always struck me as a bit OTT and perhaps unnecessarily so. It only takes
a fraction of the energy 'Old Sparky' dished out to kill someone. Atrial
Fibrillation can be induced with just a few tens of milliamps. OK, I'll
grant you it's far less spectacular than this:

https://www.youtube.com/watch?v=WCJUEvFYaGc

But there you go. That's entertainment!

 

[Allan Herriman]

On Fri, 17 Mar 2017 17:28:21 -0700, John Larkin wrote:

On Fri, 17 Mar 2017 17:13:05 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Friday, March 17, 2017 at 7:33:04 PM UTC-4, Clifford Heath wrote:
On 18/03/17 06:21, John Larkin wrote:
Resonating an AM antenna needs a giant variable cap, or a varicap
and some sort of tracking voltage source for that.

They don't make big enough varicaps for that, but those Superjunction
FETs discussed here recently would work.

A friend designed a specialised hand-held pickup head that had to tune
1-5MHz, and used 480(!) small varicaps. It was measuring micro-ohms of
dynamic impedance using transformer coupling (about 8mm square) across
a small air gap. The DUT had dozens of resonances with Q of 1000-5000
across the band.

I suggested using the Superjunction FETs, but the device is finished.

Clifford Heath.

A perfect application for Y5V / Z5U / X5R ceramic caps. 2uF varicap? Can
do!

Cheers,
James Arthur

Good point.

Somebody makes a thing like a varicap, for tuning, but it's actually a
ceramic dielectric thing.

I was always impressed by the tapered curvey variable multi-plate caps
in old radios, how they got the antenna tuning and LO to track. They did
that without computers!

I used to have a Yamaha CT-7000 FM tuner, perhaps one of the best FM
tuners from the 1970s.

From http://www.fmtunerinfo.com/yamaha.html :

"The CT-7000 has a 7-gang tuning capacitor (two gangs in front of the
first MOSFET RF amp, two in front of the second MOSFET RF amp, two in
front of the MOSFET mixer and one for the bipolar local oscillator)."

Alignment must have been fun.

Allan

 

On Saturday, 18 March 2017 16:58:37 UTC, Taxed and Spent wrote:

On 3/18/2017 9:54 AM, bitrex wrote:
On 03/18/2017 12:04 PM, Cursitor Doom wrote:
On Sat, 18 Mar 2017 10:50:10 -0400, krw wrote:

http://www.roadsideamerica.com/story/7814

In your case, I'd pay gladly for the electricity.

Always struck me as a bit OTT and perhaps unnecessarily so. It only takes
a fraction of the energy 'Old Sparky' dished out to kill someone. Atrial
Fibrillation can be induced with just a few tens of milliamps. OK, I'll
grant you it's far less spectacular than this:

https://www.youtube.com/watch?v=WCJUEvFYaGc

But there you go. That's entertainment!


I'm a liberal and yet, in some circumstances I do support the death penalty.

But IMO the goal should be to show the condemned the mercy they did not
show their victim(s) in life.

As civilized people it's the least we could do.


I believe it is more merciful to put someone deserving to death, than to
lock them up for the rest of their life.

the problem of course is wrong convictions.


NT

 

On Saturday, March 18, 2017 at 10:50:15 AM UTC-4, k...@notreal.com wrote:

On Sat, 18 Mar 2017 07:35:18 -0700 (PDT),
bloggs.fredbloggs.fred@gmail.com wrote:

On Friday, March 17, 2017 at 10:47:17 PM UTC-4, k...@notreal.com wrote:
On Sat, 18 Mar 2017 00:46:33 -0000 (UTC), Cursitor Doom
curd@notformail.com> wrote:

On Thu, 16 Mar 2017 22:22:33 -0400, krw wrote:

Nothing like that. I knew the surgery would be bad but it wasn't nearly
as bad as they said.

I find coming round after the op is the worst part. It's not like normal
waking up. I panic like hell! "Where am I? What the fuck happened? What
are all these fucking tubes for?" That kind of thing. Nasty!

I don't recall anything like that, either. Perhaps because I came out
of it more slowly? I've also had a few quicky anasthesias for
cardioversions (basically a defib with the paddles glued to the chest
and back) and woke uf form those not even realizing that I'd been out
and it was already done, though the burns on my chest did let me know
that something happened (300J does that).

What a waste of electricity!

http://www.roadsideamerica.com/story/7814

In your case, I'd pay gladly for the electricity.

In your case, a reusable rope is best.

 

[Carl Ijames]

"rickman" wrote in message newsai9hq$ifc$2@dont-email.me...

On 3/14/2017 9:58 PM, Jim Thompson wrote:

"Procedure" tomorrow (Wednesday) at 11:00AM:

Down the throat with a scope, check out the stomach, then into the
small intestine, use side-looking ultrasound on the end of the probe
(didn't know such a thing existed) to examine the common pancreas/bile
duct, go up it with a wire, then thread a balloon up that wire,
inflate and decimate the stones, then go on up and examine the gall
bladder.

Possible later procedure, after the nauseous, tiredness, yellowness
abates, go in thru an incision and remove the gall bladder.

Such fun >:-}

If I don't show up in a day or too...

Three days and no word. Hope everything went ok.

I wonder how a balloon is supposed to decimate stones? For kidney
stones they use shocks of high intensity ultrasound.

Rick C
==========================================================

With kidney stones, one option is lithotripsy where they sit you in a
stainless steel bathtub and blast with high intensity sound created by
firing a submerged spark gap. Thousands of hits later the stone is usually
in pieces small enough to pass. Problem is part of the kidneys are shadowed
by the pelvic bones so if the stone is in the wrong place this doesn't work.
Mine were shadowed so twice now they have gone in with an endoscope through
the bladder and up to the kidney, put the end against the stone, and blasted
away with a pulsed laser to break up the stone. Then they used a mesh
basket (butterfly net?) on the end of the scope to catch the bigger pieces
and pull them out, leaving any fine sand to be passed. I don't have any
idea how just a balloon would break up a stone but maybe he meant the basket
to catch the pieces? They also can use an ultrasonic probe to examine the
walls in a colonoscopy, sigh .

-----
Regards,
Carl Ijames

 

On Sat, 18 Mar 2017 11:34:05 -0000 (UTC), Cursitor Doom
<curd@notformail.com> wrote:

On Fri, 17 Mar 2017 22:47:12 -0400, krw wrote:

I don't recall anything like that, either. Perhaps because I came out
of it more slowly? I've also had a few quicky anasthesias for
cardioversions (basically a defib with the paddles glued to the chest
and back) and woke uf form those not even realizing that I'd been out
and it was already done, though the burns on my chest did let me know
that something happened (300J does that).

As this Darwin Award nominee found out:

http://www.bbc.co.uk/news/uk-39307418

The fool didn't have an amy of doctors and nurses standing around in
case something went wrong with his iPhone.