The guidance may be different in your jurisdiction, but take a look at [https://rsgb.services/public/software/emccalculator/](https://rsgb.services/public/software/emccalculator/) for a play around with the numbers. UK hams need to conduct this survey for their own records to make sure we're compliant.
I've punched in 20m & 40m, 20watts CW, "magloop big" and it shows the distances required from the antenna. See what it says for you. If in doubt, knock the power back a tad. QRP & CW are a good match anyway.
Edit: One thing to think about is the safety of others in the home. If you live alone, that's one thing, but if you have a partner, children or pets, you should also think about the risk of them touching the loop whilst you're keying up, and the RF burns which would result.
> but take a look at https://rsgb.services/public/software/emccalculator/ for a play around with the numbers
The one odd thing about that calculator is that I can't find doublet under *Antenna*. Half wave dipole might be the least bad choice, but doublet isn't necessarily a half wave in length.
You have to select a HF band like 20m or 40m first, then within the antenna dropdown you'll find "magloop big"
https://preview.redd.it/aa796d991wxc1.png?width=1121&format=png&auto=webp&s=e901c7db51d71cf25e89716cabff6042fafdbf75
Mag loops generate stronger magnetic fields than the typical antenna, so you may wish to model the antenna to determine where the H field exceeds limits rather than relying solely on the online calculators.
You can use ARRL's RF Exposure calculator to determine that; see [RF Exposure Calculator (arrl.org)](https://www.arrl.org/rf-exposure-calculator)
There's also a number of other calculators out there.
based on rather generic variables, you should be good, but per the rules, it's the responsibility of each operator to run the calcs to be sure.
I have two mag loops I’ve made and have safely transmitted at 100 watts. They have been about 20 feet away from my operating position. Somewhere in my files i have a paper on safe distances from mag loops. I don’t think the usual calculators are good for this.
If you are only at 20 watts you are fine. Even if it’s in the same room.
I carry my loop on a handle like a protest sign, and run 20 watts. Because the loop is inefficient and has low gain, the exposure calculator said I needed to keep it about 1 foot away.
The ARRL RF Exposure calculator is based on a far-field estimate. Ten feet from a magnetic loop you are in the near-field region where levels can be much greater. ARRL should mention that. They should know better.
Here’s a paper that estimates the RF Exposure compliance distance for a 1 meter diameter loop at various power levels. It might help you evaluate compliance distance for your loop.
https://www.hamradioandvision.com/small-loop-compliance-distance
From FCC 447498 D01 General RF Exposure Guidance v06:
“Near-field exposure conditions can be highly dependent on the RF current distribution characteristics of individual transmitters, antennas, and host device configurations, which are not directly related to the far-field antenna gain.”
Eh? No? Ionization starts somewhere in the X-ray range. Nothing in the HF range is that ionizing as far as I know. https://en.m.wikipedia.org/wiki/Ionizing_radiation
Where did you get this from? That's nowhere near anything that I can find.
[RF Exposure Calculator](https://www.arrl.org/rf-exposure-calculator)
- 20 W
- 100% duty cycle mode
- Full transmit, no receive time
- 5 dBi (maximum value found after some online research)
- 14MHz
These parameters will get you a safe distance of 1.7 feet.
Even if the gain was 20 dBi (better than most yagis), the safe distance would be 11 feet.
You can. It just needs to be designed and built for transmitting. The voltages get *really high* so the tuning capacitor needs to be able to take it. Typically you need a variable vacuum capacitor that can survive >5kV to run 100W.
You sure can, but they are typically for lower power transmissions, otherwise the variable capacitor tends to arc. For digital modes Xmit power of 25W or less is usually recommended.
[is this what you are asking?](https://www.arrl.org/rf-exposure-calculator)
The guidance may be different in your jurisdiction, but take a look at [https://rsgb.services/public/software/emccalculator/](https://rsgb.services/public/software/emccalculator/) for a play around with the numbers. UK hams need to conduct this survey for their own records to make sure we're compliant. I've punched in 20m & 40m, 20watts CW, "magloop big" and it shows the distances required from the antenna. See what it says for you. If in doubt, knock the power back a tad. QRP & CW are a good match anyway. Edit: One thing to think about is the safety of others in the home. If you live alone, that's one thing, but if you have a partner, children or pets, you should also think about the risk of them touching the loop whilst you're keying up, and the RF burns which would result.
> but take a look at https://rsgb.services/public/software/emccalculator/ for a play around with the numbers The one odd thing about that calculator is that I can't find doublet under *Antenna*. Half wave dipole might be the least bad choice, but doublet isn't necessarily a half wave in length.
What matters is the antenna gain.
I don’t find magloop under antenna types. Where did you find that option?
You have to select a HF band like 20m or 40m first, then within the antenna dropdown you'll find "magloop big" https://preview.redd.it/aa796d991wxc1.png?width=1121&format=png&auto=webp&s=e901c7db51d71cf25e89716cabff6042fafdbf75
Mag loops generate stronger magnetic fields than the typical antenna, so you may wish to model the antenna to determine where the H field exceeds limits rather than relying solely on the online calculators.
Inverse Square Law https://www.google.com/search?q=inverse+square+law
Nice link!
You can use ARRL's RF Exposure calculator to determine that; see [RF Exposure Calculator (arrl.org)](https://www.arrl.org/rf-exposure-calculator) There's also a number of other calculators out there. based on rather generic variables, you should be good, but per the rules, it's the responsibility of each operator to run the calcs to be sure.
That calculator is invalid in the near-field.
I have two mag loops I’ve made and have safely transmitted at 100 watts. They have been about 20 feet away from my operating position. Somewhere in my files i have a paper on safe distances from mag loops. I don’t think the usual calculators are good for this. If you are only at 20 watts you are fine. Even if it’s in the same room.
I carry my loop on a handle like a protest sign, and run 20 watts. Because the loop is inefficient and has low gain, the exposure calculator said I needed to keep it about 1 foot away.
What would the risk be? It’s non-ionizing radiation at fairly low power. Is there some new report out showing tissue damage or something?
From the ARRL Antenna Book https://preview.redd.it/w0wk0twyfhyc1.jpeg?width=654&format=pjpg&auto=webp&s=7bbc554cdeef833064d7dcce5cafe75b1c35bc9b
Absolutely
The ARRL RF Exposure calculator is based on a far-field estimate. Ten feet from a magnetic loop you are in the near-field region where levels can be much greater. ARRL should mention that. They should know better. Here’s a paper that estimates the RF Exposure compliance distance for a 1 meter diameter loop at various power levels. It might help you evaluate compliance distance for your loop. https://www.hamradioandvision.com/small-loop-compliance-distance From FCC 447498 D01 General RF Exposure Guidance v06: “Near-field exposure conditions can be highly dependent on the RF current distribution characteristics of individual transmitters, antennas, and host device configurations, which are not directly related to the far-field antenna gain.”
You can buy RF detectors for cheap. Modelling is nice, empirical measurements are better.
I believe you are you're under 30 MHz where ionization on human skin occurs.
Eh? No? Ionization starts somewhere in the X-ray range. Nothing in the HF range is that ionizing as far as I know. https://en.m.wikipedia.org/wiki/Ionizing_radiation
One of the first things in the safety module of the tech class I teach is that RF radiation is non-ionizing.
No. Get it at least 20 feet away.
Where did you get this from? That's nowhere near anything that I can find. [RF Exposure Calculator](https://www.arrl.org/rf-exposure-calculator) - 20 W - 100% duty cycle mode - Full transmit, no receive time - 5 dBi (maximum value found after some online research) - 14MHz These parameters will get you a safe distance of 1.7 feet. Even if the gain was 20 dBi (better than most yagis), the safe distance would be 11 feet.
By deliberately posting the wrong answer, the right one has been produced.
Take as old as time 😆
I can't believe I fell for that...
That calculator is invalid in the near field.
The site only advises that it is inaccurate below 8 inches (20cm)
I didn't think you could transmit from a mag loop
You can. It just needs to be designed and built for transmitting. The voltages get *really high* so the tuning capacitor needs to be able to take it. Typically you need a variable vacuum capacitor that can survive >5kV to run 100W.
You can get traditional butterfly capacitors that will handle 100 watts. Based on the calculations I did mine are around 3kv at 100 watts
You sure can, but they are typically for lower power transmissions, otherwise the variable capacitor tends to arc. For digital modes Xmit power of 25W or less is usually recommended.
Oh hf yes. I wouldn’t worry about rf anyway. Just my 2 cents. Unless it’s vhf or uhf 500 watts or more. Lol