# RF transformer

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#### ineedhelp

##### New Member
i finally found a tv transmitter source plus schematics & stuff.But i don't really understand what an RF transformer is.It states a 4.5Mhz transformer 1F-can-style.Can anyone tell me wat it means??And where i can find one of these plus an adjustable inductor with values of 0.14 to o.24mH , slug tuned coil.

#### panic mode

##### Well-Known Member
it is not 1F, it is IF (intermitent frequency).
Take a look at this page to see what do they look like
(top page) https://homepage.tinet.ie/~ei9gq/50conv.html

4.5MHz is IF frequency for video signal and it's found in TV sets.
If you cannot source new device from your electronic supplier,
just salvage components from broken TV. Note that it's not look
or size that count, it's the resonant frequency. This means you
cannot just use same thing from an AM/FM radio and expect your
transmitter to work correctly.

#### k7elp60

##### Active Member
4.5 Mhz IF transformer

The transformer is conventional in that it has two windings. If it is a IF transformer that means the primary and the secondary are tuned to 4.5 Mhz. If the coils are slug tuned then there is most likely a capacitor in parallel with each coil. Some times the capacitors are marked in value and sometimes they are not. The coils can be removed from the can with
care. If the capacitor is marked then if you use this formula you will get an idea of what the inductor is: LC=(25330/f x f). In other words divide 25330 by 4.5 squared. The result will be the LC ratio in uh and Pf. Divide the result of the initial calculation by the value of the capacitor, and the
result will be the inductance in uh. If you have a LC bridge you can measure the values directly.

#### Nigel Goodwin

##### Super Moderator
What is the purpose of a 4.5MHz transformer?, I'm presuming this is for USA NTSC - there's no such frequency used in either UK or European sets.

I'm presuming it's possibly the inter-carrier sound IF frequency, it's obviously much too low for vision IF. The UK uses 6MHz and the rest of Europe uses 5.5MHz for inter-carrier sound.

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