View Full Version : Tripping the GFI

Richard Stouffer
11-30-2007, 01:48 PM
WA8yxm and I were OSOing on another thread and I mention that I have tripped my GFI in the motorhome a couple of times. He said he has done the same thing. I'h sensing that it's a grounding problem. Anyone here got any better ideas? And even if I am right, what's the best way to ground DC and RF?


11-30-2007, 03:34 PM
I am no expert but since a GFI senses current flow on the ground connection I am thinking that your antenna might actually couple into the skin? One of many possibliities, unfortunately.

11-30-2007, 03:48 PM
I also notice that you might have a long ground wire back to the inverter. I think the ground is supposed to be as short as possible. I wound up using a window frame thinking that it was grounded through the skin. It seems to work anyway.

11-30-2007, 07:01 PM
WA8yxm and I were OSOing on another thread and I mention that I have tripped my GFI in the motorhome a couple of times. He said he has done the same thing. I'h sensing that it's a grounding problem. Anyone here got any better ideas? And even if I am right, what's the best way to ground DC and RF?


Hi Richard, I test GFI's all the time with a tester and find a lot will fail because they are to sensitive and they you will get a lot of nuisance trips so might want to try a new one plus it is good to have one on hand. I had a RF feed back in my coax and tried some clamp on ferrites but found by coiling about 10 feet of coax worked better and got rid of all my feed back. It can be a pain dealing with RF in suck close quarters, my plan is to get the antenna farther form the trailer by using a tripod and push up mast. Good luck on finding a cure and keep us posted.

Richard Stouffer
12-01-2007, 06:38 AM

This is the kind of subject that exposes the value of this net. Many of the problems that each of us encounter with tranceivers in fiberglass and aluminum trailers and motor homes are unique to us. This may be one of the few places that we can find other hams who have experience with and solved those kind of problems.

Back to the origanal point, has anybodhy tried an artificial RF ground. MFJ has one for $109? It's the MFJ-931 and it zeros out the reactance on the RF ground.

I've got a shack full of MFJ gadgets- some have been worth every penny, others aren't worth the frieght it took to get them there. So before I spend $109 to gamble on one of those Starksville black boxes I'd like to hear form an experienced user.

Richard, WU5K

12-01-2007, 12:07 PM
Richard, originally I had a stray RF problem in the coach running my HF gear on direct DC voltage. I was getting into my TV amplifier when watching what I call local TV on batwing antenna, and I was periodically bothering my slides. They would try to activate and come in. Not good. It was suggested by a friend that I use a power supply plugged into my coach AC plug. I did this and all of my stray RF stopped and I have not had a problem since. My antenna mount is a mirror type mount on top of my ladder with a quick disconnect for my hamsticks, hustlers or my long wire.

I know of some people that use the artifical ground from MFJ, but i is in their stick house, not RV. It has solved all of their problems in their homes. Hope I have been of some help to you and good luck. Stray RF is the pits - I know. Take care and travel safe.................Jim

12-01-2007, 12:31 PM
To keep the house DC clean, what about a plain ol' 12 v battery just for the radio? Last time I was on Ocracoke Island I made 525 contacts in a week, about 4 hrs a day without having to recharge a plain old car battery.

The rig was a Kenwood TS-570D


Richard Stouffer
12-01-2007, 01:02 PM
Thanks both. I am running a small power suppply off of the house current to power the rig. I don't think the XYL is going to like the idea of an automotive type battery in HER rv.

12-01-2007, 03:19 PM
I have 2 series 31 batteries mounted on the front of my trailer and run power straight from the battery to the radio and don't have any problems. I mostly dry camp and even though I have a generator, most campgrounds don't let you run one after dark. I too have been curious how well one of the MFJ artificial grounds work.

12-01-2007, 03:40 PM
With my TS-2000 I've not had any problems with RF getting back into the house via the power line, of course I'm tapped at the main junction (80 amp sustained capacity) with a rig fused at, IIRC 25 amps, Those U-220's make a good filter even if they are around 30 feet away (perhaps more)

I have, however, tripped the GFCI (120 volt) when using VHF or UHF and an indoor antenna, no problem if the antenna is outdoor (Indoors the antenna is ... Well I can touch both the antenna and the GFCI at the same time) No problem with the 50 watt V/U-HF rig using the mirror mount in the front of the rig though

But when I'm using the TS-2000 in the middle of the rig, only about 10 watts on 440 and CLICK the GFCI trips.

Richard Stouffer
12-01-2007, 04:17 PM
I'm getting the impression that this might be a fairly common problem. Anyway, I just sent an email to W1ZR, the "Doctor" at ARRL, asking if he had any ideas. He usually responds within a day or two even to weekend inquiries. If I do get a response I'll post it.

Richard, WU5K

Richard Stouffer
12-05-2007, 06:27 AM
Here's the response I recieved from the Doctor at ARRL. It's a bit on the general side, but it does provide some other possibilities to pursue.
By the way, I've been very impressed at the responsiveness of the Doctor. I've gotten a response to every inquiry and often within a day of asking, even on weekends.


I am not familiar with GFCI in a motor home but assume they are the same as a conventional home. If so, one solution to your RFI problem might be to replace your GFCI outlets with a different brand. We've had favorable reports with Leviton GFCI outlets, which are available in both 15 and 20 amp versions for 117 VAC. They are readily available at Home Depot and Lowes home centers, and probably most others. Bryant Ground Fault receptacles also features a published 0.5 volt immunity from 150 kHz to 230 MHz. We have received good reports concerning their imunity effectivness from other amateurs. Online Information is available from Bryant at: http://www.hubbell-bryant.com/pdfs/BSS100.pdf.

Another possible cure might be a filter between the GFCI and power cable. There are commercially available "brute-force" AC line filters, but installing one is another matter. If the maximum load at the GFCI outlet is less than 300 watts (about 2.5 A), a Radio Shack catalog #15-1111 might work. (Note: This is unlikely if you use a toaster at this outlet) If not, some of the filters sold by Industrial Communications Engineers, http://www.arrl.org/cgi-bin/tisfind?patt=Industrial+Comm should do the trick.

It may not be possible to add such a filter due to space limitations in the GFCI area. One possible cure in this case is a ferrite bead on each lead right at the GFCI. The bead need only be just big enough for the wire. Be sure to select a ferrite mix that is suitable for the frequency of interest. Several beads might provide increased immunity, especially in the case of HF.

A common mode choke on the cable leading up to the GFCI is another similar but possible cure. While the ARRL RFI Book contains a detailed explanation of the common-mode choke, you'll find making one is a pretty simple matter. Wrap several turns (as many as you can get) of the power cable onto an FT-240-73 ferrite core.) The common-mode choke should be installed right at (or near) the affected GFCI. In addition, you could try several chokes along the cable leading up to the GFCI. This will hopefully break up any resonant lengths along the cable, something which may cause one GFCI to trip while the others remain unaffected.

The ARRL "RFI Web Site" contains a list of EMI/RFI materials suppliers for ferrite chokes. You can also refer to the advertisements in QST -- there are a few advertisers offering ferrite materials and chokes.


Mike Gruber, W1MG

12-06-2007, 09:02 AM
N7OQ beat me to it.....a lot of GFCI's trip due to being faulty. I would change it out and see. Many of the great old American mfg's, Leviton for example, are now made in china...quality? NOT