Driver to drive?

[Clifford Heath]

On 20/03/17 02:45, Tim Williams wrote:

"Clifford Heath" <no.spam@please.net> wrote in message
news:58cddfce$0$39518$b1db1813$7968482@news.astraweb.com...
On 18/03/17 20:08, Tim Williams wrote:
"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*

No. The resonators were micromachined aluminium bars, 52 in series,
tuned a third of a semitone apart, vacuum sealed inside a 1mm^3
chip, and had to be pinged and read at LN2 temperatures. At room
temp, the Q's exceeded 1000; at LN2, some would pass 5000. Fun stuff.


Wait, "dynamic impedance" == mechanical resonance? Oh...

Exactly. Rather than make an RFID chip that works at LN2 temperatures,
it's a mechanical resonator string with a small coil antenna, in a
strong magnetic field, pinged and sensed by a (not cold) sensing coil.
Some of the resonators are damped in production -> 52 bit code-word
containing ECC codes.

 

[amdx]

On 3/19/2017 6:42 PM, rickman wrote:

On 3/19/2017 7:31 PM, billbowden wrote:
"amdx" <nojunk@knology.net> wrote in message
newsam0ee$ch5$1@dont-email.me...
On 3/14/2017 11:18 PM, billbowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC pipe
with
numerous turns of wire that has an inductance of say 200uH. Now suppose
you
use the same (6 inch) piece of PVC with a ferrite rod in the core with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and produce the
greatest
signal output? Would it be more ferrite, or more wire?


I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8"
long x
0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement method.

To measure the signal I have a very high input impedance amp with a
gain
of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel
2 output from the back of the scope to drive a Boonton 92BD RF millivolt
meter. I use the scope to compare the visual to audio from a portable
radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual average.

Let me know what you want.
Mikek


Actually, I'm just interested in comparing the response of two identical
loopsticks, one using an air core and the other using a ferrite core. I
could do the experiment since there is a 50KW station about 7 miles
away and
I can see the signal from the antenna loop directly on a scope. I can get
about 1 volt peak using a loop antenna of about 15 inches square. I just
thought someone would know the answer without a lot of experimenting.
I have
a portable car radio with a air core loop antenna mounted on the chassis
that measures 6.5 inch by 3/4 diameter and about 300 turns of small wire.
Works fine and gets stations 130 miles away. But it's a power hog and
draws
100mA from a 12 volt battery. I suppose a good test would be to use a
shorter ferrite rod and fewer turns to compare the results. But I'm
lazy and
just want to know which idea is better.

Connecting a scope directly to a loop antenna may cause a loss of Q.

It does in my situation, high Q coil and very good cap. I have a high
input impedance amp with a gain of one. I drive ch 2 and get an
amplitude of 250mv pp. If I then connect a X10 scope probe to the LC
then retune for the added capacitance, I only get 70mv on ch 2. The
probe loads my LC heavily. Unloaded Q is 1200 plus or minus 200

I'm hoping not, as I am building a very high Q antenna that will depend on a
high impedance not sapping it, but it depends on the antenna. The point
is if your measurement saps the Q, then any impact on the Q by the
ferrite will not be noticed.

If your serious, I built the Kleijer amp, 2nd version from this page.
> http://www.crystal-radio.eu/fetamp/enfetamp.htm
It got a little flack from here, everyone could do better, but know
one did. Your High Q LC doesn't know it's connected.

The equations I used include Q in the formula for received signal
strength. So if the ferrite impacts the Q it won't work as well as
expected by the equations (unless you measure the Q and include that).

All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

You can see how the ferrite causes additional losses in the upper
frequencies. If this is not understandable, let me know I'll post the
whole experiment.
Also let me know if you do decide to build a Kleijer amp, I might
save you some hassle.
Mikek


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[amdx]

On 3/19/2017 7:49 PM, Phil Allison wrote:

amdx wrote:




All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

You can see how the ferrite causes additional losses in the upper
frequencies.


** Again you have built a frame antenna, not too different from what was fitted to many radios prior to the arrival of ferrite rods.

Having a ferrite rod sited in the middle is ineffectual, the reduction in turns is not offset by any benefit.

Is it that hard to do what the OP asked for?

It's not, If the OP had answer my questions about what size diameter
PVC he wanted I would have done it today.
Yes, when the OP said 6" length, I got diameter, probably because I
have five 6" diameter coils completed on the shelf.

With a 6 inch LONG tube that a 6 inch LONG ferrite rod can neatly fit inside.

A 3/8" diameter fit neatly inside my 1/2" OD styrene tubing, not so
neatly inside a 1/2" pvc pipe.

It's guaranteed the ferrite version will then win by a large margin.


..... Phil

Yes, I agree.

Mikek

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[rickman]

On 3/19/2017 8:20 PM, amdx wrote:

On 3/19/2017 6:42 PM, rickman wrote:
On 3/19/2017 7:31 PM, billbowden wrote:
"amdx" <nojunk@knology.net> wrote in message
newsam0ee$ch5$1@dont-email.me...
On 3/14/2017 11:18 PM, billbowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC pipe
with
numerous turns of wire that has an inductance of say 200uH. Now
suppose
you
use the same (6 inch) piece of PVC with a ferrite rod in the core with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and produce the
greatest
signal output? Would it be more ferrite, or more wire?


I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8"
long x
0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement method.

To measure the signal I have a very high input impedance amp with a
gain
of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel
2 output from the back of the scope to drive a Boonton 92BD RF
millivolt
meter. I use the scope to compare the visual to audio from a portable
radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual
average.

Let me know what you want.
Mikek


Actually, I'm just interested in comparing the response of two identical
loopsticks, one using an air core and the other using a ferrite core. I
could do the experiment since there is a 50KW station about 7 miles
away and
I can see the signal from the antenna loop directly on a scope. I can
get
about 1 volt peak using a loop antenna of about 15 inches square. I just
thought someone would know the answer without a lot of experimenting.
I have
a portable car radio with a air core loop antenna mounted on the chassis
that measures 6.5 inch by 3/4 diameter and about 300 turns of small
wire.
Works fine and gets stations 130 miles away. But it's a power hog and
draws
100mA from a 12 volt battery. I suppose a good test would be to use a
shorter ferrite rod and fewer turns to compare the results. But I'm
lazy and
just want to know which idea is better.

Connecting a scope directly to a loop antenna may cause a loss of Q.

It does in my situation, high Q coil and very good cap. I have a high
input impedance amp with a gain of one. I drive ch 2 and get an
amplitude of 250mv pp. If I then connect a X10 scope probe to the LC
then retune for the added capacitance, I only get 70mv on ch 2. The
probe loads my LC heavily. Unloaded Q is 1200 plus or minus 200


I'm hoping not, as I am building a very high Q antenna that will
depend on a
high impedance not sapping it, but it depends on the antenna. The point
is if your measurement saps the Q, then any impact on the Q by the
ferrite will not be noticed.

If your serious, I built the Kleijer amp, 2nd version from this page.
http://www.crystal-radio.eu/fetamp/enfetamp.htm
It got a little flack from here, everyone could do better, but know one
did. Your High Q LC doesn't know it's connected.



The equations I used include Q in the formula for received signal
strength. So if the ferrite impacts the Q it won't work as well as
expected by the equations (unless you measure the Q and include that).

All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

You can see how the ferrite causes additional losses in the upper
frequencies. If this is not understandable, let me know I'll post the
whole experiment.
Also let me know if you do decide to build a Kleijer amp, I might
save you some hassle.

It is hard to find any info on a Kleijer amp through google. I found a
thread where you were discussing building one with Fred Abse. One other
discussion by OErjan and kiwi_steve refered to usign a Kleijer amp with
links to Dick Kleijer's pages on his work.

http://www.crystal-radio.eu/fetamp/enfetamp.htm

I'm sure you've seen this. How does your amp vary much from this?

Interesting stuff. I might want to build one of these.

--

Rick C

 

[rickman]

On 3/19/2017 11:44 PM, Robert Baer wrote:

amdx wrote:
On 3/19/2017 7:49 PM, Phil Allison wrote:
amdx wrote:




All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv
* Err...something radically wrong.
You seem to be saying that adding ferrite (in the coil) does NOT
change the inductance.
There would be a major change (increase) of inductance if ferite was
added (inside) coil.

What is wrong is that the ferrite rod is only 3/8 inch diameter and the
coil is 6 inches. So overall the ferrite has little effect.

--

Rick C

 

[Tim Williams]

"Clifford Heath" <no.spam@please.net> wrote in message
news:58cf1dc1$0$32619$b1db1813$79461190@news.astraweb.com...

Exactly. Rather than make an RFID chip that works at LN2 temperatures,
it's a mechanical resonator string with a small coil antenna, in a
strong magnetic field, pinged and sensed by a (not cold) sensing coil.
Some of the resonators are damped in production -> 52 bit code-word
containing ECC codes.

Neat!

I wonder if that would be any easier by, say, punching a strip of
magnetostrictive material into various length fingers. Like this,
http://science.howstuffworks.com/anti-shoplifting-device5.htm
Maybe the coupling between fingers would be too much to achieve Q like that.

Tim

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

 

[Clifford Heath]

On 20/03/17 14:31, Tim Williams wrote:

"Clifford Heath" <no.spam@please.net> wrote in message
news:58cf1dc1$0$32619$b1db1813$79461190@news.astraweb.com...
Exactly. Rather than make an RFID chip that works at LN2 temperatures,
it's a mechanical resonator string with a small coil antenna, in a
strong magnetic field, pinged and sensed by a (not cold) sensing coil.
Some of the resonators are damped in production -> 52 bit code-word
containing ECC codes.
Neat!

As I like to say, the world's smallest electric guitar
It survives autoclaving and strong gamma radiation.
I wrote chunks of the decode software, amongst other things.
Developed and patented by <http://bluechiip.com>.

I wonder if that would be any easier by, say, punching a strip of
magnetostrictive material into various length fingers. Like this,
http://science.howstuffworks.com/anti-shoplifting-device5.htm
Maybe the coupling between fingers would be too much to achieve Q like
that.

Interesting, I don't know. I suspect someone would have thought of
that during the >10years of research that went into this. Would
radiation kill the bias magnet? (of course, for this purpose it
wouldn't need to be built-in).

 

[Michael A. Terrell]

Kevin Aylward wrote:

"Kevin Aylward" wrote in message
news:kfudnRgqWLyQIlDFnZ2dnUU7-XvNnZ2d@giganews.com...

"bitrex" wrote in message news:9DdzA.62942$mb5.42260@fx19.iad...


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

I don't see that there can be much more of a cold-bloodied, calculated
murder, than having 12 people calmly sit on seats debating the merits
of killing someone over several days, with a state sponsored judge
exposing all sorts of "rational" arguments as to how it is ethically
justifiable to execute said person being debated. Said person is then
dragged to a room with gawking onlookers watching the deliberate
injection of chemicals to terminate said life. This is no less
barbaric than at a Roman gladiator ring where the emperor points his
thumb up or down.

What is even more grotesque, is that large numbers of those barbarians
supporting state sponsored murder are alleged Christians, despite
their role model, Jesus, emphatically instructing them that "thou
shall not kill". More, stunningly the xtians claim that it is they
that there the morally righteous ones.

It was mistranslated from, 'Thou shall not murder'. Not that you
would care.


--
Never piss off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)

 

[Robert Baer]

amdx wrote:

On 3/19/2017 7:49 PM, Phil Allison wrote:
amdx wrote:




All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

* Err...something radically wrong.
You seem to be saying that adding ferrite (in the coil) does NOT
change the inductance.
There would be a major change (increase) of inductance if ferite was
added (inside) coil.

You can see how the ferrite causes additional losses in the upper
frequencies.


** Again you have built a frame antenna, not too different from what
was fitted to many radios prior to the arrival of ferrite rods.

Having a ferrite rod sited in the middle is ineffectual, the
reduction in turns is not offset by any benefit.

Is it that hard to do what the OP asked for?

It's not, If the OP had answer my questions about what size diameter
PVC he wanted I would have done it today.
Yes, when the OP said 6" length, I got diameter, probably because I
have five 6" diameter coils completed on the shelf.

With a 6 inch LONG tube that a 6 inch LONG ferrite rod can neatly fit
inside.

A 3/8" diameter fit neatly inside my 1/2" OD styrene tubing, not so
neatly inside a 1/2" pvc pipe.


It's guaranteed the ferrite version will then win by a large margin.


..... Phil

Yes, I agree.

Mikek

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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

It's 5 days now.


NT

 

Thank you. I didn't realize they used series Schottky strings.

Could the need be somewhat averted with back bias instead?

Not so easy in a ring topology--the diodes are in antiparallel, not as in a bridge rectifier.

The MOSFET approach was developed by the late great Ed Oxner at Siliconix in the late '70s, and published as an app note for the Si8901 monolithic quad FET. (It might have been 8601--iirc they re-used the p/n for a gate driver chip so the old one is hard to fin info on.)

The idea is to put the FETs in a ring, cross-connect the gates in two pairs and put the LO there via the usual transformer. The RF and IF ports are the corners of the ring (1 and 3 for one and 2 and 4 for the other).

Since the gates are high-Z, you can use a large LO swing, which is mainly what helps the IMD.

The Tayloe approach uses a mux, but is the same basic idea, and aiui it came along much later. So I think it should be called the Oxner mixer.

Cheers

Phil Hobbs

 

[Tauno Voipio]

On 19.3.17 15:20, amdx wrote:

On 3/14/2017 11:18 PM, billbowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC pipe
with
numerous turns of wire that has an inductance of say 200uH. Now
suppose you
use the same (6 inch) piece of PVC with a ferrite rod in the core with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and produce the greatest
signal output? Would it be more ferrite, or more wire?


I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8" long
x 0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement method.

To measure the signal I have a very high input impedance amp with a
gain of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel 2 output from the back of the scope to drive a Boonton 92BD RF
millivolt meter. I use the scope to compare the visual to audio from a
portable radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual average.

Let me know what you want.
Mikek


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

--

-TV

 

On Friday, March 17, 2017 at 10:35:40 PM UTC-4, Bill Bowden wrote:

dagmargoodboat@yahoo.com> wrote in message
news:b0c5a1f7-85e1-41ae-a716-b3c7f80910a1@googlegroups.com...
On Wednesday, March 15, 2017 at 12:18:38 AM UTC-4, Bill Bowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC pipe
with
numerous turns of wire that has an inductance of say 200uH. Now suppose
you
use the same (6 inch) piece of PVC with a ferrite rod in the core with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and poduce the greatest
signal output? Would it be more ferrite, or more wire?

The Antenna Ferrite Loopstick Verses
(an exercise in mixed metaphors)
--------------------------------

I raised an aerial into the air,
Pumped in some watts; they landed, but where?
For, so swiftly they flew, the sight
Could not follow the watts in their flight.

But now we all know
(thanks to Edward J. Snowden)
They were scooped from the ether
By one William ('Bill') Bowden.

Whose giant loop, all loaded with ferrite
Had grabbed all my flux (that ain't fair, right?)
To warm up his home, and light LEDS,
And listen to Rush whenever he pleased.

Actually, when I was overseas in the south pacific working at a telegraph
station, we put up a long wire antenna tuned to the local AM broadcast
station and managed to light a neon bulb (NE-51) or whatever. I probabaly
could have charged a battery with the thing by just stealing the RF power
from the air. I think it was a 10KW station about a mile away.

Aha! Caught 'ya!

Grins,
James Arthur

 

On Monday, March 20, 2017 at 9:36:51 AM UTC-4, amdx wrote:

On 3/19/2017 10:56 PM, rickman wrote:
On 3/19/2017 8:20 PM, amdx wrote:
On 3/19/2017 6:42 PM, rickman wrote:
On 3/19/2017 7:31 PM, billbowden wrote:
"amdx" <nojunk@knology.net> wrote in message
newsam0ee$ch5$1@dont-email.me...
On 3/14/2017 11:18 PM, billbowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC
pipe
with
numerous turns of wire that has an inductance of say 200uH. Now
suppose
you
use the same (6 inch) piece of PVC with a ferrite rod in the core
with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and produce the
greatest
signal output? Would it be more ferrite, or more wire?


I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8"
long x
0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement
method.

To measure the signal I have a very high input impedance amp with a
gain
of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel
2 output from the back of the scope to drive a Boonton 92BD RF
millivolt
meter. I use the scope to compare the visual to audio from a portable
radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual
average.

Let me know what you want.
Mikek


Actually, I'm just interested in comparing the response of two
identical
loopsticks, one using an air core and the other using a ferrite core. I
could do the experiment since there is a 50KW station about 7 miles
away and
I can see the signal from the antenna loop directly on a scope. I can
get
about 1 volt peak using a loop antenna of about 15 inches square. I
just
thought someone would know the answer without a lot of experimenting.
I have
a portable car radio with a air core loop antenna mounted on the
chassis
that measures 6.5 inch by 3/4 diameter and about 300 turns of small
wire.
Works fine and gets stations 130 miles away. But it's a power hog and
draws
100mA from a 12 volt battery. I suppose a good test would be to use a
shorter ferrite rod and fewer turns to compare the results. But I'm
lazy and
just want to know which idea is better.

Connecting a scope directly to a loop antenna may cause a loss of Q.

It does in my situation, high Q coil and very good cap. I have a high
input impedance amp with a gain of one. I drive ch 2 and get an
amplitude of 250mv pp. If I then connect a X10 scope probe to the LC
then retune for the added capacitance, I only get 70mv on ch 2. The
probe loads my LC heavily. Unloaded Q is 1200 plus or minus 200


I'm hoping not, as I am building a very high Q antenna that will
depend on a
high impedance not sapping it, but it depends on the antenna. The point
is if your measurement saps the Q, then any impact on the Q by the
ferrite will not be noticed.

If your serious, I built the Kleijer amp, 2nd version from this page.
http://www.crystal-radio.eu/fetamp/enfetamp.htm
It got a little flack from here, everyone could do better, but know one
did. Your High Q LC doesn't know it's connected.



The equations I used include Q in the formula for received signal
strength. So if the ferrite impacts the Q it won't work as well as
expected by the equations (unless you measure the Q and include that).

All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

You can see how the ferrite causes additional losses in the upper
frequencies. If this is not understandable, let me know I'll post the
whole experiment.
Also let me know if you do decide to build a Kleijer amp, I might
save you some hassle.

It is hard to find any info on a Kleijer amp through google. I found a
thread where you were discussing building one with Fred Abse. One other
discussion by OErjan and kiwi_steve refered to usign a Kleijer amp with
links to Dick Kleijer's pages on his work.

http://www.crystal-radio.eu/fetamp/enfetamp.htm

I'm sure you've seen this. How does your amp vary much from this?

Interesting stuff. I might want to build one of these.



I posted that link above. I built mine from his schematic, and
pictures. Mine is pretty much the same except I had a pcb made.

Interesting stuff. I might want to build one of these.

PM me if you want to buy a stuffed and tested pcb. I have two left.


http://s395.photobucket.com/user/Qmavam/media/TwoPCBs.jpg.html?o=165

Here's the inside of mine.

http://s395.photobucket.com/user/Qmavam/media/inside.jpg.html?o=163

Nice. You can improve the front-end with a trivial mod by returning the
cold-end of the 20 megohm input resistor to T1's source, instead of
ground. That bootstraps (cancels) the input resistor's capacitance.

Original:
Vdd
-+-
|
T1 |--'
BF256C | 100nF
>----+----->|--+--||---//
| |
[10M] |
| [470]
| |
[10M] |
| |
=== ===


Modified:
Vdd
-+-
|
T1 |--'
BF256C | 100nF
>----+----->|--+--||---//
| |
[10M] |
| .-----+
| | |
[10M] | [470]
| | |
'---' ===

It's a small improvement, but it's free. If you want to get fancier
and even lower input capacitance we can bootstrap the drain, too. A
bootstrapped shield for your pass-through (where you bring the input
through your metal box) would help, too.

I have found mine very useful.
I recently put a battery pack together so I can get out in the yard
away from noise sources in the house, while testing ferrite antennas.

btw here's Kleijers home page, page to the bottom to see links to some
of his well detailed tests and experiments. Good Stuff!
http://www.crystal-radio.eu/



Mikek

Thanks for the cool measurements Mike.

Cheers,
James Arthur

 

[amdx]

On 3/19/2017 10:56 PM, rickman wrote:

On 3/19/2017 8:20 PM, amdx wrote:
On 3/19/2017 6:42 PM, rickman wrote:
On 3/19/2017 7:31 PM, billbowden wrote:
"amdx" <nojunk@knology.net> wrote in message
newsam0ee$ch5$1@dont-email.me...
On 3/14/2017 11:18 PM, billbowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC
pipe
with
numerous turns of wire that has an inductance of say 200uH. Now
suppose
you
use the same (6 inch) piece of PVC with a ferrite rod in the core
with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and produce the
greatest
signal output? Would it be more ferrite, or more wire?


I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8"
long x
0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement
method.

To measure the signal I have a very high input impedance amp with a
gain
of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel
2 output from the back of the scope to drive a Boonton 92BD RF
millivolt
meter. I use the scope to compare the visual to audio from a portable
radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual
average.

Let me know what you want.
Mikek


Actually, I'm just interested in comparing the response of two
identical
loopsticks, one using an air core and the other using a ferrite core. I
could do the experiment since there is a 50KW station about 7 miles
away and
I can see the signal from the antenna loop directly on a scope. I can
get
about 1 volt peak using a loop antenna of about 15 inches square. I
just
thought someone would know the answer without a lot of experimenting.
I have
a portable car radio with a air core loop antenna mounted on the
chassis
that measures 6.5 inch by 3/4 diameter and about 300 turns of small
wire.
Works fine and gets stations 130 miles away. But it's a power hog and
draws
100mA from a 12 volt battery. I suppose a good test would be to use a
shorter ferrite rod and fewer turns to compare the results. But I'm
lazy and
just want to know which idea is better.

Connecting a scope directly to a loop antenna may cause a loss of Q.

It does in my situation, high Q coil and very good cap. I have a high
input impedance amp with a gain of one. I drive ch 2 and get an
amplitude of 250mv pp. If I then connect a X10 scope probe to the LC
then retune for the added capacitance, I only get 70mv on ch 2. The
probe loads my LC heavily. Unloaded Q is 1200 plus or minus 200


I'm hoping not, as I am building a very high Q antenna that will
depend on a
high impedance not sapping it, but it depends on the antenna. The point
is if your measurement saps the Q, then any impact on the Q by the
ferrite will not be noticed.

If your serious, I built the Kleijer amp, 2nd version from this page.
http://www.crystal-radio.eu/fetamp/enfetamp.htm
It got a little flack from here, everyone could do better, but know one
did. Your High Q LC doesn't know it's connected.



The equations I used include Q in the formula for received signal
strength. So if the ferrite impacts the Q it won't work as well as
expected by the equations (unless you measure the Q and include that).

All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

You can see how the ferrite causes additional losses in the upper
frequencies. If this is not understandable, let me know I'll post the
whole experiment.
Also let me know if you do decide to build a Kleijer amp, I might
save you some hassle.

It is hard to find any info on a Kleijer amp through google. I found a
thread where you were discussing building one with Fred Abse. One other
discussion by OErjan and kiwi_steve refered to usign a Kleijer amp with
links to Dick Kleijer's pages on his work.

http://www.crystal-radio.eu/fetamp/enfetamp.htm

I'm sure you've seen this. How does your amp vary much from this?

Interesting stuff. I might want to build one of these.

I posted that link above. I built mine from his schematic, and
pictures. Mine is pretty much the same except I had a pcb made.

> Interesting stuff. I might want to build one of these.

PM me if you want to buy a stuffed and tested pcb. I have two left.

http://s395.photobucket.com/user/Qmavam/media/TwoPCBs.jpg.html?o=165

Here's the inside of mine.

http://s395.photobucket.com/user/Qmavam/media/inside.jpg.html?o=163


I have found mine very useful.
I recently put a battery pack together so I can get out in the yard
away from noise sources in the house, while testing ferrite antennas.

btw here's Kleijers home page, page to the bottom to see links to some
of his well detailed tests and experiments. Good Stuff!

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

Mikek







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

 

On Monday, 20 March 2017 17:06:41 UTC, k...@notreal.com wrote:

On Sun, 19 Mar 2017 19:22:33 -0700 (PDT), tabbypurr wrote:
On Sunday, 19 March 2017 23:54:09 UTC, k...@notreal.com wrote:
On Sun, 19 Mar 2017 09:16:29 -0000, "Kevin Aylward"
kevinRemovAT@kevinaylward.co.uk> wrote:
"Kevin Aylward" wrote in message
news:kfudnRgqWLyQIlDFnZ2dnUU7-XvNnZ2d@giganews.com...

"bitrex" wrote in message news:9DdzA.62942$mb5.42260@fx19.iad...


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

I don't see that there can be much more of a cold-bloodied, calculated
murder, than having 12 people calmly sit on seats debating the merits of
killing someone over several days, with a state sponsored judge exposing
all sorts of "rational" arguments as to how it is ethically justifiable to
execute said person being debated. Said person is then dragged to a room
with gawking onlookers watching the deliberate injection of chemicals to
terminate said life. This is no less barbaric than at a Roman gladiator ring
where the emperor points his thump up or down.

What is even more grotesque, is that large numbers of those barbarians
supporting state sponsored murder are alleged Christians, despite their role
model, Jesus, emphatically instructing them that "thou shall not kill".
More, stunningly the xtians claim that it is they that there the morally
righteous ones.

The perp gave up his right to life by taking that of another. End of
story.

Now there's simplistic.

Yes, it really is so simple that even you should be able to
understand.

I understand it ok. You're seriously naive if you think it's that simple. Let's just agree to disagree.

 

On Monday, 20 March 2017 17:39:29 UTC, amdx wrote:

On 3/20/2017 5:45 AM, tabbypurr wrote:
On Wednesday, 15 March 2017 01:58:40 UTC, Jim Thompson wrote:
"Procedure" tomorrow (Wednesday) at 11:00AM:

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

...Jim Thompson

It's 5 days now.


NT

I have checked his website a couple times, no news there.

ditto

I hope he's just waiting to so how many people love him!
Mikek

Maybe we're just waiting to berate him?


NT

 

On Monday, March 20, 2017 at 2:16:22 PM UTC-4, amdx wrote:

On 3/20/2017 11:29 AM, dagmargoodboat@yahoo.com wrote:
On Monday, March 20, 2017 at 9:36:51 AM UTC-4, amdx wrote:
On 3/19/2017 10:56 PM, rickman wrote:
On 3/19/2017 8:20 PM, amdx wrote:
On 3/19/2017 6:42 PM, rickman wrote:
On 3/19/2017 7:31 PM, billbowden wrote:
"amdx" <nojunk@knology.net> wrote in message
newsam0ee$ch5$1@dont-email.me...
On 3/14/2017 11:18 PM, billbowden wrote:
Which is a better design. Suppose you have a 6 inch length of PVC
pipe
with
numerous turns of wire that has an inductance of say 200uH. Now
suppose
you
use the same (6 inch) piece of PVC with a ferrite rod in the core
with
considerably fewer turns of wire. Which one would capture the most
signal
at the AM Broadcast frequencies (500K to 2 Megs) and produce the
greatest
signal output? Would it be more ferrite, or more wire?


I'll run the experiment.

Do you want it tuned?

If not, I have no way to measure the signals of my local stations.
I need the resonance peaking to see the signal.

What diameter PVC?

I have 1/2" OD polystyrene that will allow a little closer coupling
between the ferrite and the wire. 400 turns #28 = 203uh air core.

I have 1/2" CPVC. actual OD. 0.615"
290 turns #28 = 200uh air core


I have 1/2 PVC, actual OD. 0.832. 175 turns #28 = 205uh air core.

Pick one.

I'll also wind one with less turns and use my best Q rod that is 8"
long x
0.375" diameter.

I will check three frequencies, 590Khz, 1290kHz and 1430Khz.

I made a post last night of the wrong experiment (6"dia not 6" long)
It has not shown up this morning, so I'll repeat my measurement
method.

To measure the signal I have a very high input impedance amp with a
gain
of 1.
I use the amp to drive a scope (ch 2) set at 50mV/div. I took the
channel
2 output from the back of the scope to drive a Boonton 92BD RF
millivolt
meter. I use the scope to compare the visual to audio from a portable
radio to know where I am tuned.
Modulation causes a bit of amplitude bounce, but I do a visual
average.

Let me know what you want.
Mikek


Actually, I'm just interested in comparing the response of two
identical
loopsticks, one using an air core and the other using a ferrite core. I
could do the experiment since there is a 50KW station about 7 miles
away and
I can see the signal from the antenna loop directly on a scope. I can
get
about 1 volt peak using a loop antenna of about 15 inches square. I
just
thought someone would know the answer without a lot of experimenting.
I have
a portable car radio with a air core loop antenna mounted on the
chassis
that measures 6.5 inch by 3/4 diameter and about 300 turns of small
wire.
Works fine and gets stations 130 miles away. But it's a power hog and
draws
100mA from a 12 volt battery. I suppose a good test would be to use a
shorter ferrite rod and fewer turns to compare the results. But I'm
lazy and
just want to know which idea is better.

Connecting a scope directly to a loop antenna may cause a loss of Q.

It does in my situation, high Q coil and very good cap. I have a high
input impedance amp with a gain of one. I drive ch 2 and get an
amplitude of 250mv pp. If I then connect a X10 scope probe to the LC
then retune for the added capacitance, I only get 70mv on ch 2. The
probe loads my LC heavily. Unloaded Q is 1200 plus or minus 200


I'm hoping not, as I am building a very high Q antenna that will
depend on a
high impedance not sapping it, but it depends on the antenna. The point
is if your measurement saps the Q, then any impact on the Q by the
ferrite will not be noticed.

If your serious, I built the Kleijer amp, 2nd version from this page.
http://www.crystal-radio.eu/fetamp/enfetamp.htm
It got a little flack from here, everyone could do better, but know one
did. Your High Q LC doesn't know it's connected.



The equations I used include Q in the formula for received signal
strength. So if the ferrite impacts the Q it won't work as well as
expected by the equations (unless you measure the Q and include that).

All ferrite has losses and usually the higher you go in frequency the
more lossy it becomes.
Here's a test I did yesterday, I put a rod in the center of a 6" dia.
coil. I reduced turns to get approx. the same inductance.

Best Ferrite Poorer ferrite
236uh 232uh 216uh
33 turn 30 turn 30 turn
Air core coil Ferrite Coil Ferrite Coil

590kHz 59 mv 43 mv 59 mv

1290kHz 15.5 mv 6.7 mv 7.1 mv

1430kHz 10.5 mv 4.2mv 3.2 mv

You can see how the ferrite causes additional losses in the upper
frequencies. If this is not understandable, let me know I'll post the
whole experiment.
Also let me know if you do decide to build a Kleijer amp, I might
save you some hassle.

It is hard to find any info on a Kleijer amp through google. I found a
thread where you were discussing building one with Fred Abse. One other
discussion by OErjan and kiwi_steve refered to usign a Kleijer amp with
links to Dick Kleijer's pages on his work.

http://www.crystal-radio.eu/fetamp/enfetamp.htm

I'm sure you've seen this. How does your amp vary much from this?

Interesting stuff. I might want to build one of these.



I posted that link above. I built mine from his schematic, and
pictures. Mine is pretty much the same except I had a pcb made.

Interesting stuff. I might want to build one of these.

PM me if you want to buy a stuffed and tested pcb. I have two left.


http://s395.photobucket.com/user/Qmavam/media/TwoPCBs.jpg.html?o=165

Here's the inside of mine.

http://s395.photobucket.com/user/Qmavam/media/inside.jpg.html?o=163

Nice. You can improve the front-end with a trivial mod by returning the
cold-end of the 20 megohm input resistor to T1's source, instead of
ground. That bootstraps (cancels) the input resistor's capacitance.

Original:
Vdd
-+-
|
T1 |--'
BF256C | 100nF
----+----->|--+--||---//
| |
[10M] |
| [470]
| |
[10M] |
| |
=== ===


Modified:
Vdd
-+-
|
T1 |--'
BF256C | 100nF
----+----->|--+--||---//
| |
[10M] |
| .-----+
| | |
[10M] | [470]
| | |
'---' ===

It's a small improvement, but it's free. If you want to get fancier
and even lower input capacitance we can bootstrap the drain, too. A
bootstrapped shield for your pass-through (where you bring the input
through your metal box) would help, too.

I have found mine very useful.
I recently put a battery pack together so I can get out in the yard
away from noise sources in the house, while testing ferrite antennas.

btw here's Kleijers home page, page to the bottom to see links to some
of his well detailed tests and experiments. Good Stuff!
http://www.crystal-radio.eu/



Mikek

Thanks for the cool measurements Mike.

Cheers,
James Arthur


If you will look at my picture,
http://s395.photobucket.com/user/Qmavam/media/inside.jpg.html?o=163
you will notice I put the 470 ohm (turquoise resistor) on the other side
of the shield, (I don't know why).
What affect would that have?

If you want to get fancier
and even lower input capacitance we can bootstrap the drain, too. A
bootstrapped shield for your pass-through (where you bring the input
through your metal box) would help, too.

OK, I'd like to get fancy, but I don't understand "A bootstrapped
shield" for my pass through.
I would like to understand physically what I need to do.

The idea is to shield your signal with coax, then to drive the coax's
shield to reduce the effect of the coax's capacitance.

In this case it was because I thought you were using a high-capacitance
(for the situation) signal feed-through, but it looks like you've
already done a very nice job providing low capacitance.

Here's another picture showing the input, there is 5/8" hole in the case
and I glued polystyrene sheet over it with the input wire coming out the
center.
http://i395.photobucket.com/albums/pp37/Qmavam/Input.jpg
Ah, here's a picture of a previous input cap, I don't use anymore, but
it shows the input better.
http://i395.photobucket.com/albums/pp37/Qmavam/1cmx1cmspaced5mm.jpg

The idea of bootstrapping is to provide a unity-gain buffer, then make
all the circuit nodes swing with the input voltage, so that the input
signal doesn't have to charge any of the nodes' capacitances.

This illustrates the ideas--

+12V +12V
-+- -+-
| |
| [22k] R4
\| |
Q1 |---+----------.
.<| | |
| [47k] R5 |
(shield) T1 |--' | |
------ BF256C | === |
>----------+----->|--+----------------|---//
---+-- | | Vdd |
| [10M] R1 | -+- |
| | | | |
| [10M] R2 | |/ Q2 |
| | .-----+---| |
| | | | |>. C1 |
| '---' R3[470] | 100n |
| | +---+--||--'
| === |R6 |
| [1K] '--||--.
| | 100n |
| === C2 |
'---------------------------------+
|
[22k] R7
|
===

Q1 forces the drain to move up and down *with* the input signal,
cancelling Cgd. T1's source already follows the input signal,
reducing the effective Cgs.

I've shown Q2 driving a shield. It's optional--you likely don't need that.

If our buffer (Q2) and T1 together manage a gain of 0.8, we'll cancel
roughly 80% of the input capacitance. (A more complicated buffer
getting closer to unity gain would provide even better input
capacitance cancellation.)

Your author says his 0.3pF input cap and FET buffer form a 1:17 divider,
implying T1's effective input capacitance is about 5pF. You should be
able to improve that by a factor of five without breaking a sweat, by a
factor of ten with a little more care.

Cheers,
James Arthur

 

On Sun, 19 Mar 2017 19:22:33 -0700 (PDT), tabbypurr@gmail.com wrote:

On Sunday, 19 March 2017 23:54:09 UTC, k...@notreal.com wrote:
On Sun, 19 Mar 2017 09:16:29 -0000, "Kevin Aylward"
kevinRemovAT@kevinaylward.co.uk> wrote:
"Kevin Aylward" wrote in message
news:kfudnRgqWLyQIlDFnZ2dnUU7-XvNnZ2d@giganews.com...

"bitrex" wrote in message news:9DdzA.62942$mb5.42260@fx19.iad...


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

I don't see that there can be much more of a cold-bloodied, calculated
murder, than having 12 people calmly sit on seats debating the merits of
killing someone over several days, with a state sponsored judge exposing
all sorts of "rational" arguments as to how it is ethically justifiable to
execute said person being debated. Said person is then dragged to a room
with gawking onlookers watching the deliberate injection of chemicals to
terminate said life. This is no less barbaric than at a Roman gladiator ring
where the emperor points his thump up or down.

What is even more grotesque, is that large numbers of those barbarians
supporting state sponsored murder are alleged Christians, despite their role
model, Jesus, emphatically instructing them that "thou shall not kill".
More, stunningly the xtians claim that it is they that there the morally
righteous ones.

The perp gave up his right to life by taking that of another. End of
story.

Now there's simplistic.

Yes, it really is so simple that even you should be able to
understand.

 

On Mon, 20 Mar 2017 01:41:14 -0400, "Michael A. Terrell"
<mike.terrell@earthlink.net> wrote:

Kevin Aylward wrote:
"Kevin Aylward" wrote in message
news:kfudnRgqWLyQIlDFnZ2dnUU7-XvNnZ2d@giganews.com...

"bitrex" wrote in message news:9DdzA.62942$mb5.42260@fx19.iad...


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

I don't see that there can be much more of a cold-bloodied, calculated
murder, than having 12 people calmly sit on seats debating the merits
of killing someone over several days, with a state sponsored judge
exposing all sorts of "rational" arguments as to how it is ethically
justifiable to execute said person being debated. Said person is then
dragged to a room with gawking onlookers watching the deliberate
injection of chemicals to terminate said life. This is no less
barbaric than at a Roman gladiator ring where the emperor points his
thumb up or down.

What is even more grotesque, is that large numbers of those barbarians
supporting state sponsored murder are alleged Christians, despite
their role model, Jesus, emphatically instructing them that "thou
shall not kill". More, stunningly the xtians claim that it is they
that there the morally righteous ones.


It was mistranslated from, 'Thou shall not murder'. Not that you
would care.

I really think it's funny when militant atheists lecture Christians on
Christianity.