Experimenting with Coils for Crystal Sets
 

Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.
Thanks David

Experimenting with Coils for Crystal Sets
 

David wrote:
Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.
Thanks David

I got beat up on my last reply offering comments....but, whatever.

The small slug tuned HF coils in cans really have no place in crystal
radio circuits. However, the long ferrite rod loopstick coils are quite
good and are popular.

I'll offer an invitation to http://theradioboard.com/rb/ if you
aren't familiar with the site. You should be able to scrounge up some
additonal suggestions there.

-Bill

Experimenting with Coils for Crystal Sets
 

David wrote:
Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.
Thanks David

They'll have very low Q, and therefore not really be suitable for a
crystal radio, where low-Q coils fight your ability to get good
selectivity without burning up all your signal before it gets to the
headphones.

There's a whole bunch of _other_ cool things you can do with them, just
not Xtal sets.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Experimenting with Coils for Crystal Sets
 

On Apr 25, 11:51*pm, Tim Wescott wrote:
David wrote:
Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.
Thanks David

They'll have very low Q, and therefore not really be suitable for a
crystal radio, where low-Q coils fight your ability to get good
selectivity without burning up all your signal before it gets to the
headphones.

There's a whole bunch of _other_ cool things you can do with them, just
not Xtal sets.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details athttp://www.wescottdesign.com/actfes/actfes.html

I tinkered around a lot with crystal radios back when I was a kid. It
seemed that the most important thing was matching the impedance of the
radio to the antenna. This is much more critical on crystal set than a
modern superhet The only ham in the county impressed me very much with
what a crystal set could do if properly matched to a good antenna
system. He had worked all the states and a lot of the countries using
a crystal radio as his rx. I do think he kind of cheated though by
finding the signal on his regular station rx and then listening for it
on the crystal set.

Jimmie

Experimenting with Coils for Crystal Sets
 

David wrote:

Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.

Unfortunately, the *Q* of those coils will be much too low for effective use
in crystal receivers. The best results I've had with "no power" receivers
involved the use of FET detectors and /very/ High-Q coils. The inductors
usually have to be large diameter air-cored, but you can get away with toroid
or ferrite rod types if you can accept poorer results. It's quite
illuminating to browse the offerings on the web.

Bob

Experimenting with Coils for Crystal Sets
 

Bob wrote:
David wrote:


Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.


Unfortunately, the *Q* of those coils will be much too low for effective use
in crystal receivers. The best results I've had with "no power" receivers
involved the use of FET detectors and /very/ High-Q coils. The inductors
usually have to be large diameter air-cored, but you can get away with toroid
or ferrite rod types if you can accept poorer results. It's quite
illuminating to browse the offerings on the web.

Bob
How about making an Air Core Toroid. That can be made using a wax core.
Then after winding it,
some QDope or something in strips to hold the windings and then melting
the wax. Or maybe a foam
plastic core.

Bill K7NOM

Experimenting with Coils for Crystal Sets
 

On Apr 25, 10:51*pm, Tim Wescott wrote:
David wrote:
Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.
Thanks David

They'll have very low Q, and therefore not really be suitable for a
crystal radio, where low-Q coils fight your ability to get good
selectivity without burning up all your signal before it gets to the
headphones.

There's a whole bunch of _other_ cool things you can do with them, just
not Xtal sets.

--

Tim Wescott
Wescott Design Serviceshttp://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details athttp://www.wescottdesign.com/actfes/actfes.html

What would be a good Q range for AM broadcast & Shortwave bands.
Another thing is that a lot of these coils have only one coil on a
form like an adjustable loopstick, maybe i'll never know unless i try
them. Holding them next to each other they look alike.

Experimenting with Coils for Crystal Sets
 

On Apr 26, 10:31*pm, Bill Janssen wrote:
Bob wrote:
David wrote:

Was just wandering if anyone has used or experimented with television
IF, Video and Detector coils, most are slug tuned coils that have a
few uh to several hundred uh, some are sheilded some are not, i have
about 500 that i bought years ago, a lot of them look very close too
the old loopstick type coils, looking for
ideas.

Unfortunately, the *Q* of those coils will be much too low for effective use
in crystal receivers. *The best results I've had with "no power" receivers
involved the use of FET detectors and /very/ High-Q coils. *The inductors
usually have to be large diameter air-cored, but you can get away with toroid
or ferrite rod types if you can accept poorer results. *It's quite
illuminating to browse the offerings on the web.

Bob

How about making an Air Core Toroid. That can be made using a wax core.
Then after winding it,
some QDope or something in strips to hold the windings and then melting
the wax. Or maybe a foam
plastic core.

Bill K7NOM- Hide quoted text -

- Show quoted text -

Have used glue from a hot glue gun before, the coils will never move
once the glue sets.

Experimenting with Coils for Crystal Sets
 

Bill Janssen wrote:

How about making an Air Core Toroid. That can be made using a wax core.
Then after winding it,
some QDope or something in strips to hold the windings and then melting
the wax. Or maybe a foam
plastic core.

Bill K7NOM


There was a manufacturer in the 20s that used a coil like that. Thorola
- they called them donut coils. Looks like they just wound them on a
small form, maybe 1 inch, and then slid it off and bent it around
afterwards into the form of a donut.

Never heard any comment yeah or nay about their efficacy.

-Bill M

Experimenting with Coils for Crystal Sets
 

On Apr 27, 9:22*am, Bill M wrote:
Bill Janssen wrote:
How about making an Air Core Toroid. That can be made using a wax core.
Then after winding it,
some QDope or something in strips to hold the windings and then melting
the wax. Or maybe a foam
plastic core.

Bill K7NOM

There was a manufacturer in the 20s that used a coil like that. *Thorola
- they called them donut coils. *Looks like they just wound them on a
small form, maybe 1 inch, and then slid it off and bent it around
afterwards into the form of a donut.

Never heard any comment yeah or nay about their efficacy.

-Bill M

I think the best one I ever made used an oatmeal box for a form. Big
air core coils seems to be the way to go. I built a kit that used a
pair of loopstick coils and the best I could ever do wiith it was a
couple of local stations. I think it was a Heathkit. A good RF ground
seemed to benifit the receiver more than the antenna. Back in the day
my father had a service station with about two acres of concrete out
front. I was able to connect into a ground point that hooked it up to
all the wire and rebar in the concrete.



Jimmie