[SADXA] RFI

[W7EXG (Bill)]

Hi Wes,

Good sleuthing!! 

I have 2 American Standards that are normally running intermittently at this
time. They were installed new about 2008. I have not experienced such noise.
I suspect there is some type of failure with the relay, or relay circuitry
when unit is in the off mode. 

I will look and see if, by chance, there is a schematic glued of tucked into
the back of the unit somewhere. 

However, it might be a mute point, if my model does not match your model?

Just a FYI in case any of this might help. 

Bill W7EXG


-----Original Message-----
From: sadxa-bounces at mailman.qth.net [mailto:sadxa-bounces at mailman.qth.net]
On Behalf Of Wes
Sent: Tuesday, July 07, 2020 4:56 PM
To: SADXA
Subject: [SADXA] RFI

I haven't been too active lately, so I can't pinpoint when this started but
I 
discovered it on Field Day when I was plagued with an intermittent noise
that 
made me give up.  Trico has been quite good about working these issues, but
the 
intermittent nature didn't bode well for it happening when they were
looking.  
So I did some sleuthing of my own.  My tribander is about 120 feet from the 
house and my power line is to the west of it.  The house is NE of the
tower.  
The noise actually went down when pointed west but peaked when pointed at
the 
house.  I could hear it everywhere from 160 to 6 meters on my Sony
ICF-SW7600, 
even inside the house when it was on.  The problem was it was off more than
on.

I had a previous issue with my Internet system causing a problem when the 
Ethernet cable hooked to the rooftop Wi-Max receiver wasn't plugged in 
completely by the service guy after an antenna change.  So I went up on the
roof 
(it was 106 deg) with the receiver to sniff around.  Of course the noise was

gone by then.

I have a 13-year old, rooftop packaged Trane heat pump model WCZ060F100BD
near 
the Wi-Max system and while I was on the roof, it turned off and the noise 
erupted.  The heat pump was the source, but not while running.  I could hear
an 
audible buzzing sound inside the box.  I pulled the fuses and all was
quiet.  
Plug them back in, noise, both audible and RF resumes.  Heat pump turns on
to 
cool and noise is gone.

Investigating inside I determined that the potential relay was chattering
when 
in standby.  When cooling it pulls in, disconnects the starting capacitor
and 
the unit runs normally.  No one but a ham would ever know there was a
problem.  
Looking at a generic schematic 
(https://www.achrnews.com/articles/93735-potential-starting-relays) I don't
see 
how this can happen.  Clearly, there is more to this.

Unfortunately, Trane (American Standard) guards their schematics like gold
in 
Ft. Knox and I've been unable to find one for further troubleshooting.  I'm
open 
to any and all ideas.  Links to a complete schematic would really be
appreciated.

Wes  N7WS

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