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Re: LF: LF coil tuning

To: [email protected]
Subject: Re: LF: LF coil tuning
From: Brenda Hayes <[email protected]>
Date: Sun, 30 Jan 2011 13:26:48 +1300
In-reply-to: <[email protected]>
References: <DF8D483685124FFBA8436BD2C5850C8E@White> <[email protected]> <[email protected]>
Reply-to: [email protected]
Sender: [email protected]

At 12:10 p.m. 30/01/2011, you wrote:
The traditional method of tuning an LF loading coil is to use a variometer.

I have been investigating methods of tuning coils for mobile use and one method that appeared briefly in one of the ARRL Handbooks of the 50s was the shorted turn method of tuning.

I tried a home made coil of 136uH on a 5cm diameter former and using a shorted turn of 2mm insulated wire and obtained a tuning range of 32uH. (136 - 102uH).

Has anyone out there tried this?

Regards

Peter G3LDO

Hello Peter and the LF fraternity,

I use a large ex-NDB loading coil that can be tapped on any single turn. For fine tuning there is a single rotary shorted turn.To minimise losses the cross-section of the shorted turn is large [about 40mm X 10mm] and the whole thing is silver-plated on brass. Although I have never bothered to measure the inductance variation it works well for transmitting on 180 and 500 kHz. I intend to try it on 136 kHz over our coming southern hemisphere winter.

Cheers,

Kevin     ZL4MD




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