Your country may not have the same RF safety rules that we have in the
US. For the US those rules are at this link
http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65b.pdf
The mag loop will be limited by the magnetic field strength along a line
perpendicular to the plane of the loop. In the US that limit for
general population is 2.19/f amps per meter, or for 1.8 MHz 1.21 amps
per meter.
An EZNEC simulation of a 10 ft diameter loop at 1.8 MHz made with 1 inch
diameter copper pipe, and with the bottom of the loop 5 ft above ground
and with 400 watts applied shows that the magnetic field exceeds USA
safety limits for general population at 11.5 ft from the loop. That's
for 100% duty cycle. Reduce the duty cycle to 50% and the safe distance
becomes 10 ft. If you improve the low efficiency of this loop (4.95%)
that safe distance increases.
I hope we don't have the discussion again of what is, and is not safe,
because I doubt that there is anyone on this forum qualified to make
that judgement. Regardless of what is safe, or is not, we in the US
have to abide by the rules in that document. I don't know what the
rules are in the UK.
Jerry, K4SAV
On 11/15/2015 9:29 AM, K4SAV wrote:
I forgot to mention. 10 ft diameter loop is about the smallest loop
that will tune with your 1000 pf cap. A 10 ft loop needs 843 pf. Use
2 inch diameter pipe and you need 982 pf. You can see that with
AA5TB's calculator.
Jerry, K4SAV
On 11/15/2015 9:18 AM, K4SAV wrote:
I like to use AA5TB's calculator to get a quick estimate for mag loops.
http://www.aa5tb.com/loop.html#cal
Also see
http://www.aa5tb.com/loop.html
Example: 10 ft diameter loop made from 1 inch diameter copper pipe,
0.05 ohms added resistance
1.8 MHz efficiency = 4.95%
Bandwidth = 1.5 kHz
Cap voltage = 10 kV peak with 400 watts applied
(That will get much higher if you improve the efficiency)
You would have to model it in NEC and calculate the near field to get
the safe operating distance.
Jerry, K4SAV
On 11/15/2015 6:59 AM, jonathan white wrote:
Hi I am in a bit of trouble I will be mooing to a flat/apartment ,so
can anyone give me details of a mag loop that will fit in a room and
also be able to be taken apart and resembled on a beach,will use big
vac cap 1000pf 40kv Russian type,any takers,and please dont laugh I
love topband.
73`s Jon g8ccl
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