Variable capacitor question
 

What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.

"Warren" wrote in
:

What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.


It's not at all critical. Use whatever you have. All it will affect is the
tuning range.

donutbandit wrote:

"Warren" wrote in
:

What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.


It's not at all critical. Use whatever you have. All it will affect is the
tuning range.

This calculator http://www.mindspring.com/~loop_ante...loop_calc4.htm
needs the value of capacitance, so that I know how many turns I need to
wind up, as well as spacing, to cover AM band, tipically 530-1710kHz.

The tuning capacitor in standard AM broadcast radios is typically 365 PF.

Warren wrote:
donutbandit wrote:

"Warren" wrote in
:


What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.


It's not at all critical. Use whatever you have. All it will affect is the
tuning range.


This calculator http://www.mindspring.com/~loop_ante...loop_calc4.htm
needs the value of capacitance, so that I know how many turns I need to
wind up, as well as spacing, to cover AM band, tipically 530-1710kHz.

I am holding in my hot little hand, a air variable cap rated from 28pf to
468pf....I'd take $10 for it.

It's double ganged too....so it's like getting two air variable caps for the
price of one.

Let me know.


"Warren" wrote in message
...
What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.

"donutbandit" wrote in message
...
"Warren" wrote in
:

What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.


It's not at all critical. Use whatever you have. All it will affect is the
tuning range.

Great answer- since all it effects is the tuning range, why not leave it out
entirely?

As others have commented, the "standard" capacity in older AM radios is
365pF and will be fine. Antique Electronic Supply sells them also.

Dale W4OP

Warren,

Take a look at the Loop Antennas eGroup at YAHOO !
http://groups.yahoo.com/group/loopantennas/

Check-Out the LINKS Section
http://groups.yahoo.com/group/loopantennas/links

There you will find a Folder: "Variable Tuning Capacitors".
In this folder are several Links to Suppliers of Variable
Tuning Capacitors that work well with must Box Loop Antennas.


~ RHF
..
..
= = = "Warren"
= = = wrote in message ...
What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.

Look here for Variable capacitors . .

http://www.oselectronics.com/ose_p96.htm

14- -365 PF sitting midpage.. $10:95


Dan


In article , "Warren"
writes:


What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Thank you.

"Clifton T. Sharp Jr." ) writes:
Warren wrote:
What's the capacitance of variable capacitors found in clock-radios ?
I want to make a pizza-box antena and can't find 10-365pF.

Some are 10-365. Some (mostly in small transistor radios) are 10-140. Ya
picks yer radio and ya takes yer chances.

But a lot of times, the "10-365pf variable capacitor" is just a generic
term, meaning take one out of an existing radio. They are specified because
they are available. Now, in this particular case the full capacitance
may be desired because of the resulting runing range of the loop,
but plenty of times you'd see this type of variable listed because it
was available and it worked. Whenever I see one specified, I immediately
know that it's not being used for anything precision. They tend to
be built cheaply, and I wouldn't use it in a VFO that I wanted best
performance from. So I would start using what I had at hand, or
even suggest someone pay a dollar at a garage sale (or rummage sale,
or even something like the Salvation Army) for an old radio to take
the variable capacitor out of, rather than spending the ten dollars people
are suggesting for just a capacitor. Plus, the capacitor gained this
way is available locally, rather than having to send away for it.

Michael

"Dale Parfitt" wrote in
:

It's not at all critical. Use whatever you have. All it will affect
is the tuning range.

Great answer- since all it effects is the tuning range, why not leave
it out entirely?


That's a ridiculous response. Building a loop is not rocket science and is
largely done seat of pants. You wind some turns, put the capacitor
across it and see what it tunes. Then you add or subtract turns until you
get the result you want.

But since most people these days can't even check their own motor oil
without an instruction book, maybe I should take that into account.

BTW, the correct word is "affects."