Coil values for the Unelco Model 1914 Radio
 

The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...6b c0a6754a3f

Does anyone know what the coil values were?

Thanks for any info.

Coil values for the Unelco Model 1914 Radio
 

Too_Many_Tools wrote:
The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...6b c0a6754a3f

Does anyone know what the coil values were?

Thanks for any info.

X sub L = X sub C at resonance.

Coil values for the Unelco Model 1914 Radio
 

On Nov 22, 8:04*am, dave wrote:
Too_Many_Tools wrote:
The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...7824&sid=6924e...

Does anyone know what the coil values were?

Thanks for any info.

X sub L = X sub C at resonance.

Thanks for the formula but I want the ACTUAL values.

Anyone?

Coil values for the Unelco Model 1914 Radio
 

On Nov 22, 8:17*pm, Too_Many_Tools wrote:

Thanks for the formula but I want the ACTUAL values.

The odds of someone here having the same radio as you do are pretty
small. You're being told how to catch a fish rather than being given a
fish.

If you check back in the forum you linked to on antiqueradios.com,
there is a pretty good post giving the formula for calculating the
inductance of a coil. You can count turns and measure diameters and
calculate those figures for both coils.

Once you do that, you can then calculate the reactance of the coil at
both ends of the spectrum you know they tune. There's standard
formulas for doing this, too. I can't recall them offhand, but a quick
Google search should uncover them.

The vast majority of vintage radio sets tune by varying capacitance.
In an AC circuit (and radio frequency signals *are* AC), inductive
reactance opposes a change in current, making current lag voltage.
Capacitive reactance opposes a change in voltage, making voltage lag
current.

So if the capacitive reactance matches the inductive reactance, the
two reactances cancel each other out at a given frequency. Move away
from that frequency and they mismatch, causing the signal to be
attenuated, usually seriously so. The circuit is said to be resonant
at the frequency where the reactances match.

Now, to review: have a variable capacitor, and you can calculate the
inductive reactance at both 9.4 MHz and 17.8 MHz. Plug those values
into the capacitive reactance formula, solve for C, and you know the
capacitance range for the two circuits that the antenna and oscillator
coils are part of.

Now that you have that, you can calculate the capacitive reactance for
the endpoints of all the other bands. Then, go back to the coil
formula, keep the radius the same as that of your existing coils, and
you can calculate the number of turns on the missing coils. Find some
suitable stock for winding the replacement coils, and voíla!

(If you can't find any stock that exactly matches the radius of that
on the coils you do have, pick something as close as possible, and
plug that value into the coil formula to calculate turns.)

--
David Barts
Portland, OR

Coil values for the Unelco Model 1914 Radio
 

Too_Many_Tools wrote:
On Nov 22, 8:04 am, wrote:
Too_Many_Tools wrote:
The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...7824&sid=6924e...

Does anyone know what the coil values were?

Thanks for any info.

X sub L = X sub C at resonance.

Thanks for the formula but I want the ACTUAL values.

Anyone?

You may have to wind your own coils.

Coil values for the Unelco Model 1914 Radio
 

On Sunday, November 21, 2010 10:18:42 PM UTC-8, Too_Many_Tools wrote:
The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...6b c0a6754a3f

Does anyone know what the coil values were?

Thanks for any info.

I actually opened a couple of the coils up. It was easy as the bottom simply unscrews. Inside is a coil, a few caps, and what looks to be a trimmer of some sort. I doesn't seem like a simple coil with its litz wire and ferrite core. I'll see if I can't post a photo here somehow.

Coil values for the Unelco Model 1914 Radio
 

On 05/08/2013 12:58 AM, wrote:
On Sunday, November 21, 2010 10:18:42 PM UTC-8, Too_Many_Tools wrote:
The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...6b c0a6754a3f

Does anyone know what the coil values were?

Thanks for any info.

I actually opened a couple of the coils up. It was easy as the bottom simply unscrews. Inside is a coil, a few caps, and what looks to be a trimmer of some sort. I doesn't seem like a simple coil with its litz wire and ferrite core. I'll see if I can't post a photo here somehow.


X[sub]L = X[sub]C

Coil values for the Unelco Model 1914 Radio
 

On Monday, November 22, 2010 at 1:18:42 AM UTC-5, Too_Many_Tools wrote:
The Unelco Model 1914 Radio was a simple 60's-70's muliband radio that
used different coils to change bands.

http://images.craigslist.org/3k63o33...52cece1adf.jpg

http://www.antiqueradios.com/forums/...6b c0a6754a3f

Does anyone know what the coil values were?

Thanks for any info.

Can you draw a diagram of each of the coils you have showing the connections to the tube pins?

Thanks, Al, KB4RA