Loran Antenna

[orcus]

Hi
I am trying to receive Loran (100 KHz) signal using H field and E field antenna.

The E field antenna has o/p impedance 50 ohms and a gain of 20 dB. I pass this signal through a LNA (30 dB gain) and then BPF and I get a very clean loran signal.
The H field antenna has o/p impedance 50 ohms and a gain of 20 dB. I pass this signal through the same circuit and then I pass it through another 30 dB gain amplifier (as H field recieved signals are weaker than E field received ). I dont get a clean loran signal.. It is pretty messed up.

I know that my second amplifier works good as I have tested it with the E field antenna.

What is the problem. Is H field antenna highly sensitive and hence it picks up a lot of noise, reflections.
I thought impedance matching could be a problem... but then the E field works with the same circuit.

Please guide me on this problem.

 

[VEBill]

Can you provide links to the exact antennas that you're using? This seems to be the logical starting point...

 

[orcus]

Hi
Thanks for the reply. The antennas are working now and I am still not sure what was the initial problem.
I still have one problem. I am known that H field antenna works good inside the building. But my H field antenna dosent...
It works very good outside .. but inside it cannot pick up anything.
The building is a modern day steel structure... could that be a reason.. I am in a faraday cage.

 

[VEBill]

"...modern day steel structure... faraday cage."

Well, 100kHz is 3km (~1.9 miles). Size the openings appropriately.

 

[orcus]

Hi
Thanks for the reply. I cannot understand the effect of wavelength over the reception.
Can you please give me a clear explanation.
Sorry if this causes you any inconvenience.

 

[VEBill]

When you're in a metal building, radio reception suffers. The lower the frequency the worse the reception. 100kHz is pretty low...

By way of providing another example: visible light, at the other end of the EM spectrum, goes right through small apertures (windows) since its wavelength is so small.

Back to your E and H antennas: Are you using some lab 'EMI'-type antennas (probes) to try to receive Loran? Why? You'd probably do better with a wire tossed out the window (but YMMV).

BrainR had a very good suggestion to use an 'Active Antenna' (whip into FET gate) - they work great at low frequencies. I have a Sony AN-1 Active Antenna on my shortwave radio and it works great right down to very low frequencies.

I'd add the suggestion of installing the antenna OUTSIDE the building. It's normal practice (for good reasons).

 

[orcus]

hi
thanks
By keeping the antennas outside reception is very good.
I am will look more into active antennas now
thanks

 

[Higgler]

Most buildings with concrete and reinforced re-bar have 100-400 Mhz cutoff regions, hence cell phone frequency choice of 900 Mhz.
Concrete is dielectric 5 to 7 range in the cell phone frequencies.

kch

 

[VEBill]

According to some of the history of cell phones that I've read (AMPS project, Chicago, 1970s [from memory]), the testing revealed that the 400 MHz range had the best ability to penetrate structures, but those frequencies were already taken. The '800 MHz' range was second choice, but was available. Now of course, there are a couple of higher bands closer to 2 GHz for the newer 'cell' phone systems.

Maybe the delta is some overall average versus specifically concrete with rebar.

 

[rabih123]

hi I want a full eude of qfh antenna

 

[VEBill]

You should start a new thread.

Anyway, your 'eude':

http://www.w2du.com/R2ch22.pdf

By the way, I believe that the author (Walt Maxwell, W2DU) invented the QFH antenna.