I suggest that you grab an Ohmeter and check that the green wire on the
power cable is connected to the chassis. On all of the Astrons I've
checked, it was not -- it was soldered to the mounting lug of a terminal
strip, which was insulated from the chassis by paint. On one of the
units, the two sections of the chassis were also insulated from each
other by paint.
The simple fix is sandpaper.
73, Jim K9YC
On Wed,10/28/2015 8:50 AM, Art Snapper wrote:
I ran into a rather odd source of RFI, possibly common mode.
I had 2 transformer type Astron power supplies in the ham shack.
One was a 15 amp desktop type, the other a 35 amp rackmount unit.
My observation is that when both were on, a buzz was detectable on various
frequencies in the 160 band. If either was off, the buzz was gone.
Removing the 15 amp supply, and wiring everything to the 35 amp supply
corrected that problem.
I'm not sure if there was some interaction between the transformers, a
ground loop, or something else was going on.
Art NK8X
On Wed, Oct 28, 2015 at 11:34 AM, Guy Olinger K2AV <k2av.guy@gmail.com>
wrote:
The amount of MF radio garbage that is running around common mode on power
lines, phone lines, metallic pipes, etc, is pretty amazing. I've walked
around with my battery K2 listening next to power pole ground wires, buried
power lines where they enter the ground.
The garbage level goes down very quickly as you move away from the wire. A
lot of it can't be heard above atmospherics if the antenna listened on
doesn't hear anything from its own feed coax shield.
Think of it like a network of hoses with leaks all over the place, where
the leaks work in reverse and you don't want anything getting in.
Grounded, bonded together, common mode chokes plugs all the leaks INTO your
signal coax wiring and into your equipment via power and signal wiring.
Power line buzz does not always use regular propagation to your receiver.
It can come in common mode on power lines whose
entirely satisfactory-for-power-purposes entry ground happens not to be
particularly effective at RF.
You will never know your real noise floor until the shack, wiring, antennas
and feedlines are grounded, bonded and blocked as needed.
73, Guy K2AV
On Wednesday, October 28, 2015, Steve Ireland <vk6vz@arach.net.au> wrote:
Hi Jim (Murray)
Jim K9YC is absolutely right - I live in a similar situation to you and
the problems have been markedly improved by getting the grounding and
bonding to earth improved around the house - wish I had taken Jim's
advice
years ago. House earths are often very simple at best and whilst they may
be good enough to save your life, they are often not good enough in terms
of RF
Have a look at Jim's book (there are some great diagrams) and get an
professional electrician in to beef up/improve the house earth/improve
the
equipment bonding.
The likelihood is you win both ways - probably be safer and the RF noise
will be lower.
Vy 73
Steve, VK6VZ
On Sun,10/25/2015 8:59 PM, Jim Murray via Topband wrote:
Tomorrow I will walk the line and see if I can come up with anything.
Jim,
I STRONGLY suggest that you check out grounding and bonding in your home
before looking for noise sources. Poor or missing grounding and bonding
will bring noise into your home, so you need to get that right FIRST.
73, Jim K9YC
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