[ARC5] PS Hum in BC-453-B (solved!)

[Bill Cromwell]

Hi Dennis,

The space I used to set up the batteries, the radio, all of that placed 
everything withing a very few inches of the nearest power wiring. I have 
the Earth lead clipped to the chassis and that always makes a 
difference. In the past I have always used my end fed wire right into 
the shack to the matching circuit (L-network). That isn't working for me 
any more (new QTH) and I'll be running coax (moan and groan) at least 20 
feet out of the shack and add chokes and filters and strainers, and etc. 
Maybe put some squirrel bait in the sub station once in a while to get 
some radio peace and quiet <evil grin>.

73,

Bill  KU8H


On 01/29/2015 05:24 PM, Dennis Monticelli wrote:
> I'm going to take wild guess here, Bill.
>
> Unless you are very close to a source of 60Hz field, it takes a long 
> wire to pick this energy up.  I suspect your antenna (which is 
> probably a long wire with some degree of coupling to house mains 
> wiring) may be depending up the receiver's common to supply the return 
> path to earth and that may be an ill-defined path that passes through 
> sensitive circuitry.   If this is your situation you may with to 
> earth-return the antenna right at the case of the receiver.
>
> If that doesn't do it for you then you must have a source of 60Hz very 
> nearby giving you grief.  The BC-453 is well shielded for 
> capacitive coupling but the thin non-ferrous Al case is almost 
> worthless for stopping a nearby 60Hz magnetic field from inducing 
> currents within.  Maybe your receiver is sitting on top of another box 
> positioned right over its power transformer!  BTW, oscilloscopes have 
> this problem and resort to using a high mu metal shroud around the 
> CRT.  Maybe someone on the list can fashion an ARC-5 case out of 
> mu-metal :-)
>
> Dennis AE6C
>