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GM0CSZ > TECHNI 04.06.06 22:58l 45 Lines 1713 Bytes #999 (0) @ WW
BID : E12276GM0CSZ
Read: DL1LCA GUEST
Subj: Re: Skin depth in copper
Path: DB0FHN<DB0FOR<DB0SIF<DB0FHK<DB0LJ<DB0RES<ON0AR<GB7FCR<GB7SAN<GB7INV<
GB7NOS
Sent: 060602/1149Z @:GB7NOS.#76.GBR.EU #:11030 [Golspie] FBB7.00i $:E12276GM0CS
From: GM0CSZ@GB7NOS.#76.GBR.EU
To : TECHNI@WW
DF3VI wrote:-
>
>> Bet you thought skin depth at 50 Hz was irrelevant, I did until I
>> did the sums.
>> Frequency Skin depth
>> 50 Hz 9.35 mm
>
> That IS irrelevant.
> Even for somewhat higher frequencies you rarely have a _massive_ > conductor
where skin depth
matters. A massive copper conductor of
> almost 20 mm diameter (300 mm^2) cannot be handled, that is why stranded
> conductors are used. Now it is the diameter of each strand that counts.
> So yes, skin effect does not start to matter until you are in the MHz,
> or in the high power/current transmission.
> 73, Patrick
==================================
Patrick , This subject intrigues me.
If you can provide a 'skin depth versus frequency table' that would be
quite useful.
I suppose I can also find that type of info by doing 'a Google'.
Some time ago I tried to convert an italian made (valve) CB amplifier for
operation on 70 MHz , to assist a fellow radio amateur ,having received
reports that others had been successful. After reducing the number of
turns of the output PI (tank) filter I checked output impedance with an
MFJ antenna analyser
However ,although I got a resistive 50 Ohms value on both in- and output
,the unit produced 'zilch' output power.
Upon reflection I think I should have changed the PI output filter
inductor ,by replacing the 1.5 mm OD wire by say 4 or 6 mm OD copper
tubing .
This because of the increased skin effect changing from 27 to 70 MHz.
Perhaps you can confirm this.
TIA
73 - Frank , GM0CSZ @ GB7NOS.#76.GBR.EU
Inver by Tain , IV20 1RX Scotland UK Loc: IO87AT
Message timed: 11:43 UTC on 02 Jun 2006
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