Forum Discussion

whizbang's avatar
whizbang
Explorer II
Oct 23, 2021

RF getting into Winnebago Furnace!!

I have a Hi-Q antenna mounted on the ladder of a 24 foot Winnebago Minnie. Keying up 17 meters at 100 watts momentarily starts the RV's furnace, even with the furnace in the off position. The other bands seem to be okay.

Obviously, I need some combination of ferrites, shielding or grounding. I took the outside cover off the furnace, but, I am stumped and have no idea where to begin.

(FYI -- This is my second RV installation. 13 years ago, we had a 38 foot diesel pusher with an aluminum framed body. I ran 400 watts on 80 thru 10 meters. Good matches and no RFI. Our Minnie Winnie has a wood frame. I have poor matches and RFI to the furnace. The installation on both is identical --- chokes and bypass capacitors at the screwdriver motor feeds and plenty of clip on chokes. The Minnie install initially had good matches on 40 and 80, but 20meters and up were 3:1 SWR or worse. I added a shunt coil. 20 Meters thru 12 meters are now 1.2:1, but 40 and 80 are useless (and I don't care. The antenna is too short for 40 and 80 anyway.)

Suggestions???
  • Skibane's avatar
    Skibane
    Explorer II
    Oct 24, 2021
    Don't overlook the wall-mounted thermostat wires. You might try temporarily disconnecting them from the furnace to see if the problem goes away.

    Chokes work OK sometimes, but ordinary bypass capacitors (0.1 uF) can also be effective. They're also much cheaper ( which means that you can install a lot more of them), and will fit in much tighter spaces, too.
  • OkieGene's avatar
    OkieGene
    Explorer
    Oct 24, 2021
    Go to QRZ.com and to the forums section, the Mobil subsection or others you'll figure out which one, and ask your question there.
  • Harvard's avatar
    Harvard
    Explorer
    Oct 24, 2021
    Your furnace and transmitter DC negatives are probably daisy chained. Tie the DC negative supply to the chassis and then run separate DC(-) wires individually from there. One wire to the furnace and one wire to the transmitter.
  • whizbang's avatar
    whizbang
    Explorer II
    Oct 24, 2021
    Sounds like I need to invest in a bunch of chokes.

    I bought some wire wound ones from DigiKey for the T stat wires. I will get assorted clip on for the rest.

    Bypass caps are a good idea too.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Oct 23, 2021
    and/or bypass caps on the furnace wires

    Chokes on the coax to the HI-Q and on the radio's power lead.
  • MT_BOB's avatar
    MT_BOB
    Explorer
    Oct 23, 2021
    Don't do HF on the road, but I would say ferrites and perhaps chokes on the furnace power wires, and on the t-stat wires. A wireless t-stat would be a no-no. You could consider adding metal to the roof for better propagation, like sheet,fencing or strands of cable.

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