[Elecraft] spurious signals problem solved

[Brendan Minish]

On Fri, 2007-02-09 at 13:43 -0700, Terry Wilkinson wrote:
> Hi everyone:
> 
> Thanks for the replies to my post regarding spurious signals.
> 
> Just discovered the problem: I have an uninterruptible power supply, so 
> I tried plugging my K2's power supply directly into a wall plug, then 
> unplugged the UPS, and the hash went away. Looks like my UPS got 
> fried. Time for a new one.

It's probably not fried, Line interactive UPSes can produce a of of RF
Junk on the output (& input) all the time 
Off Line UPS es tend to be more benign since whilst AC is there they
simply pass though the AC. When AC fails they run an inverter to make
AC. 
On Line units are supplying inverted output all the time 

I have a couple of APC smartUPS units that are absolutely filthy and
took a lot of filtering (input and output) to tame to the point where
they don't totally trash HF. These are the smartUPS1000 units and are
good USP units for server grade IT Equipment 

I also had a Smart UPS 5000 (5KVA ) UPS that no matter what I did I
could not tame fully. Thankfully it's now in our Datacenter many miles
away..

To Summarise. 
If you are looking for Radio Friendly UPS look for an Off line UPS. It
probably will be noisy during a power failure but it should be fairly
quite when AC is present. 
With Off line UPS units the main source of noise during normal operation
is the Switch mode power supply that is used to charge the battery. Line
filtering should take care of that if it is an issue. Older (heaver!)
units used a proper linear power supply to charge the battery and are
clean. You can usually pick these up cheap second hand and the only
Maintenance they are likely to require is Gel cell replacement. Use good
Quality Gel cells sourced locally as these will be a fraction of the
price that the manufacturers charge for the same thing.  

73
Brendan EI6IZ