Electronics > RF, Microwave, Ham Radio

Hunting a 450mhz signal?

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rwgast_lowlevellogicdesin:
Last night I went out and got some wok's to make dishes for a long range wifi link. There is a STRONG signal I can recive all over my town for about 20 miles at 450.xxx Im not sure what the heck it is, very narrow ear piercing droney sound. Anyways I would like to investigate this signal more I figured maybe I could use a wok to build a dish to get HI directional and find the source. I know I wont get much gain on a 14 inch dish at UHF but it is a strong signal. What would you guys suggest I feed the wok with a biquad?

donmr:
This is why radios need band-pass filters! 
That can start with an antenna that is less sensitive to other frequencies.

Here in the US, there is a shared allocation for "Radiolocation" (Radars) and "amateur" from 420.0 to 450.0.
Are you near the coast or anything like a radar installation?

Above 450.0 is allocated to "Landmobile" which can include linking systems between sites that might always be on.

If you can narrow down the frequency you can lookup licenses (civilian only) at <http://wireless.fcc.gov/uls>

But its probably legitimate so you have to live with it.

retrolefty:
AT 450Mhz it's not hard to build and tune out a specific frequency using a high Q cavity filter to suck out the signal with little attenuation to other even near by frequencies. Hams have been doing so for decades on their longer range repeater sites.

rwgast_lowlevellogicdesin:
You huys have this all wrong, the signal is strong but narrow, it doesn't bother me or cause bad aliasing etc... I just want to know what in the heck it is on the commercial band. I am in southern california but im at least 150 miles from the coast so I dont think it would be raido location. Im just trying to figure out the easiest way of figuring out the orgin of the signal and then maybe figuring out what it is so I can run it through some DSP in GNU radio.

I have a commercial 450-470 9dbi 5 element yagi but the signal is so strong it seems to pierce right through the back reflector, so im trying to figure out how to build a very higly directional antenna for signal hunting. So a WOK and a bi quad tuned to 450? Maybe a quarter wave ground plane, Im not sure the best way to feed the reflector. Like I said gain is not terribly important here but I dont want to make a feed so bad I cant recive the signal or that wont have a tight beam width

I do live near 29 palms marine base which is the biggest base in the US but im about 20 miles away, looking up the license is a good idea I dont know why I didnt think of that, but if this were a military signal how would I determine that? Although I doubt it is it may be important for a future signal hunt. I know the FCC shows bands allocated for military use but im sure not all signals from the base are in those bands, they can use commercial HTs and things right?

donmr:
Try moving away from your house in different directions.  If you can find the edge of the "strong signal" region you will have an idea where it is coming from.  (You might find its very local too)

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