On Mon, 27 Apr 2009 05:32:07 -0700 (PDT), David
wrote:

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.

If your _loaded_ Q is 100, the -3 dB bandwidth at 1 MHz would be 10
kHz (i.e. +/- 5 kHz from the carrier). The question is, what should
the _un_loaded Q be ?

If you have a full sized antenna, the signal strength would be
sufficient even with an unloaded Q of just 100-200.

At the middle of the HF band (10 MHz) a loaded Q of 1000 would be
required for a single station bandwidth and quite large helical
resonators would be required to get a usable unloaded Q without
damping the resonant circuit Q too much.

Paul OH3LWR