Re: Remote Power Supply Connection

Trevor Wilson wrote:
> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
> news:g19ee6$20h3$1@[EMAIL PROTECTED]
>> Trevor Wilson wrote:
>>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>>> news:g16ked$1r7$1@[EMAIL PROTECTED]
>>>> Trevor Wilson wrote:
>>>>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>>>>> news:g13o17$10ph$1@[EMAIL PROTECTED]
>>>>>> Trevor Wilson wrote:
>>>>>>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>>>>>>> news:g0up1a$1ap1$1@[EMAIL PROTECTED]
>>>>>>>> Trevor Wilson wrote:
>>>>>>>>> "Ian Thompson-Bell" <ruffrecords@[EMAIL PROTECTED]
> wrote in message 
>>>>>>>>> news:g0rmo0$27co$1@[EMAIL PROTECTED]
>>>>>>>>>> I agree when the rectifiers are close to the transformer
supplying 
>>>>>>>>>> them but not when they are separated from it my a couple of
metres 
>>>>>>>>>> of cable.
>>>>>>>>> **And again, it is not difficult, nor expensive to deal with
such 
>>>>>>>>> issues. A handful of capacitors will effectively deal with any 
>>>>>>>>> problems.
>>>>>>>>>
>>>>>>>>>
>>>>>>>> Definitely not. The point is that the caps normally used to
suppress 
>>>>>>>> reverse spikes in semiconductor diodes do just that. The have no 
>>>>>>>> effect on the forward current spikes which are significant.
>>>>>>> **No.
>>>>>>>
>>>>>> Denial is not much of an argument.
>>>>> **How about: Not necessarily? Better?
>>>>>
>>>> Hardly.
>>>>
>>>>>>>  With remote ac
>>>>>>>> supplies these current spikes must pass through the cable and
they 
>>>>>>>> will cause serioes radiation. Any attempt to stop them happening 
>>>>>>>> will simply stop the rectifiers from rectifying. That is why is
is 
>>>>>>>> essential to have the rectifiers close to the transformer.
>>>>>>> **No.
>>>>>>>
>>>>>> Denial is not much of an argument.
>>>>> **OK. It is not necessary to have rectifiers close to the
transformer. 
>>>>> I set up a test last night, with 2 Metres of cable, connected to a 
>>>>> transformer, thence to a rectifier, thence to an amplifier. An AM
radio 
>>>>> place VERY CLOSE to the cable picked up some radiation. Covering the

>>>>> cable with an earthed sheild completely eliminated the noise.
>>>>>
>>>> And what current were you drawing from the rectified output?
>>> **4 Amps @[EMAIL PROTECTED]
 60 Volts.
>>>
>>>
>> That's a decent load. I am not completely convinced though. First an
a.m. 
>> radio covers only a limited bandwidth from about 500KHz to 1MHz and I 
>> would expect fast rectifier spikes to produce spectrum well beyond
that.
> 
> **So would I. However, most of the energy will be well down in the RF 
> spectrum. Fourier tells us that as frequency increases, that the amount
of 
> energy will decrease.
> 

Indeed he does tell us that, but radio propagation theory tells us that 
the degree of coupling to the 'ether' depends on the fractional length 
of the antenna. Your 2m cable is a very small fraction of the 
wavelengths of the am band so it will be a very poor radiator at 500KHz 
but represents about half a wavelength at 70MHz so I would still expect 
stronger radiation around the latter frequency than in the am band.

Cheers

Ian
>  Secondly, an earthed ****eld only eliminates the electric field.
>> The magnetic field will see that as transparent. Have you tried it with
an 
>> air band receiver?
> 
> **Nope.
>