Indoor CB-antenna - safe?

Hi friends,

I just installed my first TX-antenna in the window of my room (in an apartment). Far from optimal, I know, but it’s what’s possible at the moment.

It’s a magnet mount ”Sirio Hi Power 3000 N” which I put on a 1m long metal thing for now.

Anyway, I did some reading on RF-radiation and started to wonder how safe it would be to use at 12 watt SSB? My chair/table is about ~2m from the antenna.

Will I get fried? Some weird health issue? Will all the other tech in the room complain?

Thanks in advance,
Samuel

Here's a handy RF Density Power calculator to let you know if you're within FCC safe limits. Whilst we're not covered by the FCC it's OK to use for an indicator.

http://hintlink.com/power_density.htm

Putting in your figures and assuming 0dB gain and 6ft from the antenna the power density is 0.0286 mW/cm2, well under the "uncontrolled environment" (where you have no control over people going near it) maximum permissable exposure limit of 0.2519 mW/cm2

Power density drops extremely rapidly even just a couple of feet from an antenna, it's why all those claims about people being fried by mobile phone masts, especially 5G, are laughable at best.

It is possible the other tech in the room will complain but that might be from "common mode RFI" from the lack of a suitable ground plane rather than RF from the antenna.

Thanks for the info, and a good tip!

I googled the gain, and here they say that the antenna has a 5 dBi gain: http://www.4x4cb.com/public/item.cfm?itemID=693

Which brings the power density up to 0.2312 mW/cm2... Still OK, but I mustn’t sit closer!

Even if it was to exceed by a little, what would the effect be? Warm cheeks?

Wittfogel wrote:

Thanks for the info, and a good tip!

I googled the gain, and here they say that the antenna has a 5 dBi gain: http://www.4x4cb.com/public/item.cfm?itemID=693

No it doesn't, it really doesn't at all. That's a marketing bollocks claim that is as valid as the one that claims an Antron A99 has 9.9dBi of gain, or in other words can radiate a signal 10 times stronger than the one fed into it which even a full size 3 element beam can't manage to do.

Even full size verticals like the 24ft 5/8 wave antennas with a perfect RF ground only have gain of 3 to 4 dBi and even then that is only at one angle of take of from horizontal. You've a short antenna with a poor RF ground so 0dBi is probably being very generous.

Well, I bow to your superior wisdom - and am all the happier for it! No need to dwell further on the matter!

Thanks again for the help,
Samuel

You don't want to be touching it but you'll be safe at the power level you're using at the distance you are.

You asked what the risks are. Ultimately RF burns if it's serious enough. You don't feel you're getting burned though, it just feels like a tingling but you can get third degree burns. You don't want to be holding the whip when you transmit.

In regards to the gain, these are charts of gain from Steve G3TXQ who was a noted antenna designer of high repute who re-designed the Hexbeam two element beam to a more efficient wider bandwidth version. What he didn't know about antennas was not worth knowing. He released his designs for free and never manufactured them commercially so had no monetary benefit to drive him to make claims about the antenna. The gain of the re-designed one was only 5-6dBi and this was a full sized antenna, not one half of the size of a quarter wave so only about 25% of the efficiency of a quarter wave .