# LF Antenna Design - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

pollypocket
 Post subject: LF Antenna design Posted: Wed Oct 25, 2006 2:56 pm
 Lieutenant

Joined: Wed Oct 25, 2006 1:49 pm
Posts: 2
Location: ON
Hi;

I am looking for some guidelines for LF 134Khz antennea. I install readers in some awkward places and don't always need an off the shelf antenna. I want to be able to construct a decent antenna using 20 gauge multistrand wire in a loop(s)...speaker wire or lamp cord. It is cheap and fast and should be able to get the job done. Any advice besides sticking to a commercial antenna?

thanks,

Paul

_________________
Ride Hard, Shoot Straight, and Tell the Truth

nubbage
 Post subject: Posted: Mon Oct 30, 2006 12:39 pm
 General

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi Paul

I found this site packed with ideas for LF antennas

http://members.fortunecity.com/xe1bef/loop.htm

nubbage
 Post subject: Posted: Tue Oct 31, 2006 4:32 am
 General

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi Paul
Further to my earlier posting I found this formula in an excel file I have built up over many years of formula hunting. It gives the antenna terminal voltage into an infinite load impedance for a linear solenoid wound antenna of the type you have in mind.

V = 7.89E-6*F*N*A*H0 volts

where
H0 = received field strength A/m
F = Freq in Hz
N = number of turns
A = area in sq m

The value of H0 you would have to estimate from known parameters for the transmitting source and detection range.

I am not sure, but someone else may know: if you tune the coil and the total Q value is Q then the voltage becomes V*Q at resonance (??)

pollypocket
 Post subject: Posted: Sun Nov 26, 2006 11:53 am
 Lieutenant

Joined: Wed Oct 25, 2006 1:49 pm
Posts: 2
Location: ON
 Hi Nubbage;Thanks for the advice and links. I will have a look.Regards, Paul _________________Ride Hard, Shoot Straight, and Tell the Truth

Posted  11/12/2012

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