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# Replacing coils (Plese)

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john1

Active Member
Hi,

you can't use a screw,
or anything conductive.

cannibalise a piece of ferrite from an old radio.

i would be interested to hear how you get on,
Regards, John :)
 

Someone Electro

New Member
I think i have one somvare but its not round

Its like two half cicles whith 1 cm betven it

And I think its diameter is biger than 8 mm

How cod i caculate how meany thurns?

I have a 15 year (its a transistor tipe) old radio but i listen to it wean i work.I scavegd some things from it but only the LED UV meter and the casete player, I had to let a eqolizer i pece becose it controles the volume. all rest is on one circuit bord(radio reciver,amplefier...),
 

Sebi

Active Member
For MW You need a coil on ferrite rod. What You actually have is a wawe-trap for cable mounting. (maybe from VGA, printer, or supply cable. This have very different permeability as ferrite rod, so unuseable for this purpose.
The air coil is phiscally too big for application, this is the reason of ferrite application.
Search the old MW pocket-radio and canibalize it, if cannot foud another source.
 

Russlk

New Member
What is the capacitor that will tune the coil? What frequency are you trying to recieve? I can calculate an air core coil for you with that information.
OH! never mind, I looked at your link. The coil can be wound on a quaker oats box or corn meal box (3.85 inches diameter). 135 turns of #22 enameled wire should do it. The turns should be neatly wound close together. If the wires are spaced, it will tune higher in frequency. The wire size is not critical.
 

Someone Electro

New Member
135 Thurns around what?

Ow:
The alomst whole MW band is free(3-5 weak stations)

The coil can have to much inductivi but not to litle (you can get to the right inducticity with stecing the inductir)
 

Someone Electro

New Member
IT WORKS !!!

Its i bit unstable but im going to fix that.

Whith a 110 pF cap and a inductor whith 66 thurns it transmits at 810 kHz
 

Someone Electro

New Member
oops :oops:

The contact of the tunung cap had some resistance and it gave the right freq.

Hey if i wod put in a potencimeter serial whith the tuning cap i cod change the freq.Right?
 

Someone Electro

New Member
Its stable now and i built in a potencimeter for tunung.

This thing isnt only a trasmiter its also a RF remudulator becose i get some stations and some data streams wean its on.

Anyway im hapy whith it
 
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