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LF Antenna design - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


 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

_________________
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 Post subject:
Posted: Mon Oct 30, 2006 12:39 pm 
 
General
User avatar

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


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

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 (??)


 
   
 
 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




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