Brunobl
Veteran
Location: Pomerode, SC, Brazil - 26 40S 49 11W
| Wac,
Look into how an ADF (automatic direction finder) works. There should be lots of online info on this. It the oldest but still widely used form of radio navigation system, meant to find the direction of a radio station, from one's position.
You can get a good idea of the concept if you hold a cheap AM broadcast radio, tune in a station and rotate the radio (horizontally) through 360 degrees. You will see that there are two peaks and two nulls in reception, as the internal ferrite antenna passes through different orientations with respect to the transmitter direction (the internal antenna is bidirectional and cannot differentiate front/back). Some ground-based ADF receivers add a vertical whip antenna to resolve this ambiguity. All modern airborne ADF receivers do this automatically, and directly show the transmitter direction in the form of an arrow pointer against a compass-rose. I think some land-based ADF receivers still use the manual, rotating antenna scheme.
I suspect that what you'd want to do is , as you scan through each channel, electronically change the directional field of a phased antenna array (so you don't need a rotating antenna) and record where the peak signal strength came from. It wouldn't really matter if each found signal is FM, PCM, etc, as all you'd be really looking for would be a carrier signal at each channel.
The end result could be a series of LEDs, as you said, pointing to the approximate signal direction, briefly pausing at that position for each of the active channels found, and some indication of the channel number or frequency.
In all, this is quite a challenging project and frankly I don't think it is worth the trouble or expense of pursuing, given that most people are switching to the 2.4GHz band, turning the other, nearby radio signals a non-issue.
LONG EDIT: After I posted, I realized that you don't want to scan the RC frequency band, but your wireless video band to detect interference. I then presume that you wouldn't need frequency scanning (leave it fixed at your video TX frequency) and look for offending signals before turning on your video transmitter. Anyway the rest would still apply, and I do believe this would be an overwhelmingly complex project.
For such a specific application (detecting interfering signals), maybe a much simpler compromise could be using a receiver at your video link frequency with an S-meter and directional antenna, and phisically search all directions for other signals on your video frequency before turning on your video link.
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Best regards,
Bruno. |
