h field simulator antenna design help
h field simulator antenna design help
(OP)
Hello,
I am designing a Loran simulation tool that uses h-field propagation. I have not been able to find information on how to design the emitters I need. This is a three emitter system that need only transmit 18 to 24 inches. My available output is 1Vpp currently. Does anyone have suggestions on where to start? Thank you.
I am designing a Loran simulation tool that uses h-field propagation. I have not been able to find information on how to design the emitters I need. This is a three emitter system that need only transmit 18 to 24 inches. My available output is 1Vpp currently. Does anyone have suggestions on where to start? Thank you.





RE: h field simulator antenna design help
Over 18 to 24 inches?
RE: h field simulator antenna design help
Yes I am simulating Loran C. The transmission distance is small as I am attempting to radiate a Loran chain (inside a Faraday cage) in order to test a Loran receiver/antenna system.
RE: h field simulator antenna design help
If it is a whip, then you could just use a small value (pF) capacitor and clip it onto the antenna. Feed the signal(s) into the other side of the capacitor.
If it is a loop, then you could use a similar loop and essentially form a transformer.
It might be worth adding a variable attenuator inline so you could compare MDS.
This type of approach sort-of bypasses actually testing the antenna itself (as an antenna). But they could be qualified (once) outside using the actual Loran signals.
I was initially confused by the stated range ("18 to 24 inches"). I thought that maybe you wanted to move the UUT around and see an effect (you wouldn't). I'm now assuming that a direct connection (zero inches) is acceptable.
RE: h field simulator antenna design help
RE: h field simulator antenna design help
I thought that Loran was a time-of-arrival system (not depending on direction of arrival). I recall seeing Loran receivers with whip antennas (non-directional). So I'm wondering why the test set-up is arranged with the three directions spaced at 120 degrees.
Off I go to investigate...
RE: h field simulator antenna design help
http://www.si-tex.com/html/e-loran.html
RE: h field simulator antenna design help
RE: h field simulator antenna design help
A simpler approach to testing such a rig would be to have one source that runs around on a track circling the UUT.
Or just go outside.
RE: h field simulator antenna design help
RE: h field simulator antenna design help
RE: h field simulator antenna design help
So, assuming that you have a free hand to use whatever coil is required, and can place it closer if required, then my gut tells me that you've got a fair shot at it working.
But maybe you should do some quick and dirty experiments before investing too much.
There will be an optimum coil design. Too much inductance and you'll have reduced current. Too few turns and you'll not have enough amp-turns.
RE: h field simulator antenna design help
RE: h field simulator antenna design help
RE: h field simulator antenna design help
The optimization of the transmitting antenna is my only major hurdle to getting this bench to work. Trial and error is what I am inferring from your string. Do you have a suggestion on a starting point? I was thinking of taking the receiver antenna apart and using its coils. But I think the inductance will be too great to be effective as a transmitter.
RE: h field simulator antenna design help
For a ferrite core, maybe start with about 50 turns. For air core, maybe three-inch diameter and 50 turns. These are pure guesses.
If you're trying to qualify a new antenna design, then it'd be far easier to step outside. Otherwise you'd be heading in the direction of an RF goniometer (three dimensional coil arrangement). And then the available 1V will be the least of your worries.
RE: h field simulator antenna design help
Thank you again!!