Unregulated frequencies

There are some principles of US law that may apply here. One is that you can really use any frequency you want if it does not radiate past your property line. Another is that infringements are mostly based on interference with 'other services'.

If you are making something for sale, of course, its a whole different picture. You need to jump thru lots of hoops.

Making 'one off' projects seldom gets you in trouble unless you really piss off somebody. I have personally 'witnessed' several over the years.

Note: this is not legal advice; I am not an attorny.

Luhan

Hi, Luhan -

Can you please cite a reference regarding radiation within the confines of one's property line? In many passes through Title 47 of the Code of Federal Regulations, I have never seen any such property line statement. Most of the regulations of which I am aware concern not exceeding specified volts/meter at a specified distance (3 meters, 30 meters, etc). One exception is the

If I am wrong, I would appreciate the correction.

Thanks. John

This is not taken from FCC regs, it has more to do with property law. I do not remember the reference. It may not in fact exist.

Much of my comments are simply common sense. What is legal is one matter, what is practially enforcable is another. I've seen many projects on the internet using 'illegal' transmiiting devices, including the guy who use the innerds of his microwave oven to light up flourescent lamps accross his basement.

I try to be pragmatic in my designs for clients. Many of 'one of a kind' industrial production and test devices have no certification with regard to spurious radiation, or meet with UL approval. This is true for companies I've worked for accross the country.

As far as I know, the FCC does not much snoop around looking for problems, they simply process compaints from 'other services'. Maybe you can tell me if this is not so.

Thanks for your unusually polite comments.

Luhan

Run it at the horizontal scanning frequency of local TV's (would be around 15.75 KHz in the US).

Then the only interference you might have to worry about would be TV-tax vans

(which in the unlikely even they have actual receivers are probably looking for the colorburst clock ot the receiver LO, not the horizontal output)

Mental Note: Use 15,750 Khz for clandestine transmissions.

Luhan (Spooky) Monat

Mental Note:

Cover spy as sprinkler piping installer for golf course. You're going to need a big antenna to get much range (miles and miles and miles if the Navy's ELF submarine links are any hint)

For RF transmission, yes. Not for induction coupling.

Luhan

Like you, I suspect that the FCC does not actively look for low-power unlicensed emissions unless they receive a complaint. However, I cannot tell you if that is their policy.

Cheers, John

Yes, but your proposed "clandestine transmission" isn't going to go very far inductively coupled. Perhaps it's a digital dead drop that you simply bicycle over each day?

Why? The horizontal sweep rate is 15.734.34 hz. Do you really think you can pick up a clean signal less than 16 Hz away from all the TV sets radiating noise for miles?

Hello,

You might also consider detection of an "overhead" continuous 40khz ultra-sonic blast from a tweeter speaker or two.

Then have the listening device on each bicycle for detection and tripping your micro-controller.

If you can make home brewed circuit boards for the receivers, assembly would be quick for each unit required.

• * * Christopher

Temecula CA.USA

It's a nice idea, but my circuit is cheaper and more energy efficient. It will run for over a hundred days on a CR2032 battery and has a quiescent power consumption that will let it stay in standby for several years. It has 11 components overall and fits 35x50mm.

I didn't know you had tv tax vans in the US. Actually that's a concern because I don't have a TV and the UK TV tax people are scary.

I think I managed to answer my own question in the end. OFCOM classes inductively coupled equipment as 'class 1' and you don't need a license, or approval, or anything. There are just some power restrictions that one mustn't exceed.

I buy all your comments about 'if it doesn't cause interference don't worry' but I'm spending other people's time, effort and money on this system and I want to get it right. If OFCOM stopped me from using it my name would be mud and I don't want to risk this happening.

The other concern is stopping pacemakers. Whilst unlikely, this doesn't bear thinking about which is why I wanted to do my due diligence.

Thanks for all your help

If you're low powered enough to not be "heard" beyond a few meters, at any frequency, who's to complain?

- YD.

No, we don't have TV tax, and even you probably would not get their attention with a horizontal output inductive transmitter.

But not having a TV - I hear that does confuse them.

Yes of course. I was refering back to the original post where you would ride over it with a bicycle.

Luhan