[RFI] Motor starting and UPS

k1ttt.dave at gmail.com k1ttt.dave at gmail.com
Sat Nov 21 13:05:14 EST 2020

It will depend on the ups and the amount of the dip.  I am surprised a circulation pump would draw enough to drop the voltage that much, usually they are relatively small.  Is the ups on the same circuit as the pump??  Assuming they are on the same circuit have you checked for loose or corroded connection from the breaker to the pump and outlet??

When you say the sdr is powered from the computer, is that via usb?  Or off one of the other power supply voltages internally??  Usually usb is pretty well regulated by itself so again it would surprise me that the line voltage would affect it that much.  If its off one of the other voltages then maybe a line drop would affect it, but that goes back to the paragraph above.

On the ups side.  Some ups's run full time and protect against voltage dips, others take some time to switch on and support voltage dips like that.  There may also be an adjustment in hardware or software for the switch over to battery point.  Some ups's also have a delay before they switch to battery so they may not pick up in time.

If you have an appropriate meter you might want to measure the dip to quantify it.  It could also be the pump is going bad and drawing way too much starting current.  Or another possibility is a faulty neutral between the house and pole, that can cause all sorts of nasty voltage swings and has been know to blow out equipment and cause fires.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: telnet://k1ttt.net:7373

-----Original Message-----
From: RFI <rfi-bounces+k1ttt=arrl.net at contesting.com> On Behalf Of Ron Hunsicker via RFI
Sent: Saturday, November 21, 2020 12:32
To: rfi at contesting.com
Subject: [RFI] Motor starting and UPS


The power to my computer is via a UPS.  My SDR is powered from the computer.

When one of the water circulation pumps for my heating systems starts (an old B&G), the voltage dips so much that it is apparent in the waterfall and a drop/loss of audio.

I've tried switching legs (red v black) but that didn't help. Let's ignore the idea that the service is too small.

I thought that UPS might "protect" against such dips in the voltage and am (obviously) surprised that it does not.

Whadaya think?


Ron Hunsicker
1238 Cleveland Avenue
Wyomissing, PA 19610-2102
ronhunsi at ptd dot net

*"Democracy dies in darkness"***
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