Hello Mike,


On 15 nov, 22:54, "amdx" wrote:
"Richard Clark" wrote in message

...



On Mon, 15 Nov 2010 09:17:30 -0600, "amdx" wrote:

C shape laminated core
with a
small gap. The gap will be large enough that a small magnet will fit in
it.
The magnet
is connected to a lever and on the other end is a diaphragm.

This doesn't sound like a Crystal radio project at all. *You describe
nothing that comes close to even 1KOhm, much less 1MOhm in load. *Your
descriptions all use appeals to sensitivity, not impedance.

*Trying to maximum signal for contest situations want a longer antenna.

This confounds your desire for higher Z. *In the extreme (antenna of
several wavelengths and necessarily close to ground) will be less than
1KOhm. *In the mid-range, could be hi-Z IFF it is a halfwave long. *In
the conventional lengths, some may pose a moderately hi-Z (maybe
KOhms). *None will exhibit the Z you anticipate for your Tank.

As I said, start thinking backwards from the power delivered to your
ear. *Can you express that as a number? *Not much point in the rest of
this if you cannot.

73's
Richard Clark, KB7QHC

* Hi Richard,
*I have probably confused things, I have 4 or 5 threads running at this
time.

*The C core EI core thing is a starting attempt to build a speaker with a
high impedance
to eliminate the losses of a matching transformer. The whole excercise is to
build a crystal
radio that will eack out the most sensitivity.

*1 picowatt to the earphone is a good number.

* For sensitivity the starting point has got to be the tank circuit, you
want to build
an inductor with very high Q and then mate that to a good quality capacitor.
A Q of 1000 is possible over much of the AM BCB.
* Can we agree on that?

Now you need to couple in energy from an antenna. If this is adjusted for
maximum power transfer, we have reduced the Q by 1/2 or Q=500.
Assuming a 240uh inductor and frequency of 1 Mhz the XL is 1507 ohms,
multiply that by the antenna loaded tank Q of 500 and we have an Rp =
753,500 ohms.
*Does that work for you?

I think I found a good site for the antenna matching;http://www.crystal-radio.eu/enantunittest1.htm

Now we need to detect and tranfer the signal to a transducer

The transducer will be the difficult part (the antenna is quite simple
compared to this). As you may know, below 150mVRFpk across the
junction, rectified output voltage drops quadratically with RF input
voltage, hence detection efficiency.

So to get maximum voltage across the junction, you need a high
impedance rectifier (that means low "Is"). Disadvantage of this is
you need a transducer with same (very high) impedance (as I assume
you don't want to use electronic LF amplification). I did my
experiments with LF electronic amplification.

If you can't find / make one in the several hundred kOhms range, you
will probably need to use rectifiers with higher Is. If so, you also
need to transform the RF impedance to a lower value to get best RF
power transfer to the rectifier.

Regarding diodes, years ago I did experiments around 7 MHz with tuned
detectors where the diode capacitance is no longer small with respect
to the tuning capacitance.

When using hybrid schottky rectifiers (that are the ones with relative
high reverse blocking voltage), strange hysteresis effects occurred in
the DCout versus RFinput voltage curve. When using real schottky
rectifiers (like BAT15, 14, etc), this effect wasn't present. I didn't
document it (only some notes), so I can't share the full details with
you.


I'll stop here till I get some feedback, I don't know my question anymore? \
:-)
* * * * * * * * * * * * * * * * * * *Mike.


Good luck finding/designing the best transducer,


Wim
PA3DJS
www.tetech.nl
without abc, PM will reach me, very likely.

@amdx: thank you! Will peruse.

@Richard: praise!

maaaybe we could adjourn to alt.techno-shamanism

"FCC per Anna Scarpetta" wrote in message
...
@amdx: thank you! Will peruse.

@Richard: praise!

maaaybe we could adjourn to alt.techno-shamanism

Not yet,
I still want Richard to act like he understands that
the diode characteristics are important and the diode must be
selected to match the circuit and received station signal strength.
BTW, what is the name of the teaching method where the teacher
questions every statement made? Wasn't it named after some famous
teacher/philosopher?
MikeK

On Nov 23, 7:43*am, "amdx" wrote:
"FCC per Anna Scarpetta" wrote in ...

@amdx: thank you! Will peruse.

@Richard: praise!

maaaybe we could adjourn to alt.techno-shamanism

* Not yet,
I still want Richard to act like he understands that
the diode characteristics are important and the diode must be
selected to match the circuit and received station signal strength.
* BTW, what is the name of the teaching method where the teacher
questions every statement made? Wasn't it named after some famous
teacher/philosopher?
* * * * * * * * * * * * * * * * MikeK

But what is the practicality of getting this type of match when the
impedance of the circuit changes every time you change frequency or
any other parameter. Search for such an optimum match is truly a
"fools errand". Just one of the reason most people dont listen to the
ballgame on a crystal set anymore.


Jimmie

"JIMMIE" wrote in message
...
On Nov 23, 7:43 am, "amdx" wrote:
"FCC per Anna Scarpetta" wrote in
...

@amdx: thank you! Will peruse.

@Richard: praise!

maaaybe we could adjourn to alt.techno-shamanism

Not yet,
I still want Richard to act like he understands that
the diode characteristics are important and the diode must be
selected to match the circuit and received station signal strength.
BTW, what is the name of the teaching method where the teacher
questions every statement made? Wasn't it named after some famous
teacher/philosopher?
MikeK

But what is the practicality of getting this type of match when the
impedance of the circuit changes every time you change frequency or
any other parameter. Search for such an optimum match is truly a
"fools errand". Just one of the reason most people dont listen to the
ballgame on a crystal set anymore.
Jimmie

Just call this the equivalent of collecting beanie babies. Any help
you give is like saying, Hey there's one at the yard sale down the road.
Suum cuique.
MikeK

On Tue, 23 Nov 2010 06:43:22 -0600, "amdx" wrote:

I still want Richard to act like he understands that
the diode characteristics are important

Hi Mike,

This expectation is somewhat disconnected from your earlier acceptance
of my ordering of priorities through a figure of merit methodology.
This always works, or it reveals that the designer has a poor grasp on
what is valuable to him/her. There is absolutely nothing that anyone
can do about how assessed values shift in the mind of that designer.

and the diode must be
selected to match the circuit and received station signal strength.

That doesn't seem to be a solution for you. If you reread my posting
that ennumerated the priorities, one of which I incompletely quote
he
The detector is the variable of concern, it is defined by the current
necessary to drive the headset, everything surrounding the detector
has to conform to its choice.
then you will find it is the inverse statement you have just offered.

Focus on any other variable will present a greater dissappointment.

73's
Richard Clark, KB7QHC

On Nov 23, 2:45*pm, "amdx" wrote:
"JIMMIE" wrote in message

...
On Nov 23, 7:43 am, "amdx" wrote:









"FCC per Anna Scarpetta" wrote in
...

@amdx: thank you! Will peruse.

@Richard: praise!

maaaybe we could adjourn to alt.techno-shamanism

Not yet,
I still want Richard to act like he understands that
the diode characteristics are important and the diode must be
selected to match the circuit and received station signal strength.
BTW, what is the name of the teaching method where the teacher
questions every statement made? Wasn't it named after some famous
teacher/philosopher?
MikeK
But what is the practicality of getting this type of match when the
impedance of the *circuit changes every time you change frequency or
any other parameter. Search for such an optimum match is truly a
"fools errand". Just one of the reason most people dont listen to the
ballgame on a crystal set anymore.
Jimmie

* *Just call this the equivalent of collecting beanie babies. Any help
you give is like saying, Hey there's one at the yard sale down the road.
* Suum *cuique.
* * * * * * * *MikeK

Grin, I got a few radios that fits that.

Jimmie

On 11/24/2010 12:56 PM, JIMMIE wrote:

Grin, I got a few radios that fits that.

Jimmie


BTW, the Grundig G6 Buzz Aldrin 40th Anniversary edition is on closeout
at Radio Shack. It's smaller than the name.

I couldn't resist myself. So far the best half-a-pocketbook sized radio
I've owned. Good AM filter width.

Actually it's the smallest multiband radio I've ever owed by about a
factor of 2.

tom
K0TAR

On Nov 24, 9:01*pm, tom wrote:
On 11/24/2010 12:56 PM, JIMMIE wrote:



Grin, I got a few radios *that fits that.

Jimmie

BTW, the Grundig G6 Buzz Aldrin 40th Anniversary edition is on closeout
at Radio Shack. *It's smaller than the name.

I couldn't resist myself. *So far the best half-a-pocketbook sized radio
I've owned. *Good AM filter width.

Actually it's the smallest multiband radio I've ever owed by about a
factor of 2.

tom
K0TAR

Hi Tom, Did you ever try anything with that NVIS antenna. I think I am
going to put up one permanent in back yard, turn the RV into my ham
shack or dog house whichever description is appropriate at the time.

Jimmie

On 11/24/2010 11:49 PM, JIMMIE wrote:
Hi Tom, Did you ever try anything with that NVIS antenna. I think I am
going to put up one permanent in back yard, turn the RV into my ham
shack or dog house whichever description is appropriate at the time.

Jimmie

No, not yet. Not enough time. I do plan on it though, thanks.
Possibly this coming spring.

tom
K0TAR