# LF Antenna design - RF Cafe Forums

 RF Cafe Forums closed its virtual doors in 2010 mainly due to other social media platforms dominating public commenting venues. RF Cafe Forums began sometime around August of 2003 and was quite well-attended for many years. By 2010, Facebook and Twitter were overwhelmingly dominating online personal interaction, and RF Cafe Forums activity dropped off precipitously. Regardless, there are still lots of great posts in the archive that ware worth looking at. Below are the old forum threads, including responses to the original posts. NOTICE: The original RF Cafe Forum is available again for reading, and the new RF Cafe Blog is an active board. -- Antennas -- Systems
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

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