Low Frequency Antenna
Low Frequency Antenna
(OP)
Would anybody be able to help me or point me in the right direction to design a 125 Khz antenna?
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RE: Low Frequency Antenna
Please, post any interesting information you get. I have freinds interested in 110 kHz for liightening detection, but it is for a teaching aid, not for industrial use.
RE: Low Frequency Antenna
If you want directionality, then you're looking at some sort of loop (perhaps ferrite core).
Note that I have assumed that your application is Receive Only. If you need to transmit then you've got a "whole 'nother ball of wax" where efficiency becomes The Main Issue. For receive application, efficiency isn't really an issue at these frequencies.
Google: LF antennas
RE: Low Frequency Antenna
If you have an old rail line near you, get 0.75 miles and a balun to make a dipole.
kch
PS: I apologize if the rail line comment seems offensive.
RE: Low Frequency Antenna
is by means of a 125 kHz signal (+/- 10%). The sensor is tested under pressure in a ferrite vessel whose inner diameter is approximately 4" in
diameter. Therefore size restrictions need to be considered as well. Connection to an external signal source is to be accomplished by an SMA
connector.
RE: Low Frequency Antenna
RE: Low Frequency Antenna
If yes, why not use that antenna.
kch
RE: Low Frequency Antenna
"...under pressure in a ferrite vessel..."
Ferrite never struck me
Hmmm, I'll be over there, crouching behind the filing cabinet...
RE: Low Frequency Antenna
When I was looking into buying ferrite loaded antennas on the web, they warned about cracking and they only sold the antennas with encapsulated ferrite cores placed in tough PVC pipe for protection.
kch
PS: After review, I wouldn't go with the 0.75 mile railroad dipole
RE: Low Frequency Antenna
This thread reminds me of the old joke about the bidders conference where, just as the industry people were getting up leave with their notebooks full of scribbles listing all the system requirements, the government procurement agent suddenly said, "Oh, by the way, one more thing... The entire system needs to fit through a tube with an inside diameter of 4.00-inches and with a 90-degree elbow half-way along".
RE: Low Frequency Antenna
RE: Low Frequency Antenna
If you try to capacively couple, then think of your pressure transmitter as one plate of a capacitor. What you need is a probe inside the pressure chamber to pick up the signal. Follow the probe with a amplifer with a resistor to set the output impedance for 50 Ohms (I am assuming you are trying to connect to test equipment).
If you try to inductively couple to the device-under-test, put a coil inside the pressure chamber to pick up the signal. Again, you can follow it with a amplifer. With a coil pickup, you can use a differential amplifer, or a single-ended amplifer.
In either case, the amplifer can be a op-amp with sufficient gain/bandwith well above the 125 kHz you are interested in.
RE: Low Frequency Antenna
You may not need much of an antenna.
I wish I knew more about inductive/capacitive coupling antennas, but once again, a beginner am I.
kch
RE: Low Frequency Antenna
If inductive coupling is used then it's a low Z drive and low Z receiver input. My bet would be with the inductive coupler.
RE: Low Frequency Antenna
Any tips on how to go about designing the appropriate inductive coupler?
Thanks!
Ken
RE: Low Frequency Antenna
http://www.amidoncorp.com/aai_ferriterods.htm
The TX antenna will be similar but you will play with the coupling tap point (which could alternatively be a seperate coil wound over the earthy end of the main inductor) for best results.
This is a non-critical design but do choose stable capacitors to resonate the inductors, silver mica are best such as Digikey 338-1055-ND.