Topband: Mag loop 400W if possible.

[K4SAV]

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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