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RFI and household wiring

Discussion in 'Ham Radio Discussions' started by W5DPH, Dec 29, 2016.

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  1. W5DPH

    W5DPH Premium Subscriber QRZ Page

    Hey guys, I have a possibly unique situation and am looking for some direction/suggestions. I currently am running a 40m horizontal loop lengthened by about 20ft or so to tune easier on 80m. I realize it's not efficient on 80, but anything is better than nothing and it works fine for me. I also have an AL-811 amp that tunes to right around 700w on 40m. My issue is a point of use, tankless water heater in my master bathroom. The master is located a long way from the main gas water heater so I installed aeemax tankless water heater. I will say this. It works great, almost instant, endless hot water at my two master sinks. That's all we use it for, teeth brushing and hand washing. Enough of the boring stuff. So.... when i get the amp tuned up and begin transmitting on 40m only, the relay in the tankless water heater buzzes and shorts out in just a few minutes. I realize this is an RFI issue. It doesn't happen with 100watts , but only when the amp is on. The obvious solution is not to use the amp on 40m. But I want to, or I wouldn't have bought it. So aside of not using the amp on 40m, is there any suggestions that y'all might have? I've coiled/choked the power line to the water heater, realizing it's not coax.... that didn't do anything. I've purchased some clip on ferrite, realizing again this isn't coax, and I'm going to try that too. Any other suggestions??
     
  2. KY5U

    KY5U Subscriber QRZ Page

    Where is your antenna located?
     
  3. W5DPH

    W5DPH Premium Subscriber QRZ Page

    That's one piece of information I left out. The antenna is about 25ft AGL and is basically on top of my house.
     
  4. K1VSK

    K1VSK Ham Member QRZ Page

    absent further info on how proper the system is grounded, whether RF is on the coax, if the coax is in close proximity to any wiring, etc..., people are only guessing at diagnosing and fixing the problem
     
  5. KO2LA

    KO2LA Ham Member QRZ Page

    I don't understand this statement. Can you clairify?
     
  6. W5DPH

    W5DPH Premium Subscriber QRZ Page

    certainly good question. The shack has it's very own two 8ft ground rod driven just outside of the shack. Everything in the shack is grounded. the antenna is fed with 600ohm open line coming from a 4:1 balun right under the eve of the house. The balun is fed with approximately 8ft of rg213 that has an RFI isolator and a 8" air choke. Very little if any common mode coming into the shack via coax. No cables or coax are run anywhere near power lines or recepticals, not anything out of the normal.
     
  7. WR2E

    WR2E Ham Member QRZ Page

    Have you contacted the manufacturer of the water heater yet? If not, do.
     
  8. W5DPH

    W5DPH Premium Subscriber QRZ Page

    That's exactly what it does. The unit will be off, and when I key up the amp, the relay buzzes and shorts out. Literally. I've replaced it once, considered it defective. But it happened again today and sure enough, i had the boy key the radio on FM for a second and the relay buzzed and shorted out. It no longer works.
     
  9. N0TZU

    N0TZU Platinum Subscriber Platinum Subscriber QRZ Page

    If the ferrite doesn't work by itself, you might try adding a o.1 uF capacitor across the relay coil, after unplugging the unit of course. Use only an X type capacitor which is approved for use across the AC line. Any other type could be a fire hazard if it fails shorted.( Do not attempt this if you are not comfortable with working on electronics and line voltages).

    I'm assuming the water heater is a simple device and is using line voltage for the relay. If that is not the case, and there is some low voltage control circuitry in the water heater, then the solution might be more complicated.

    I'm also assuming that by "shorted" you mean the relay contacts have fused together.
     
    Last edited: Dec 29, 2016
    N3AB likes this.
  10. W5DPH

    W5DPH Premium Subscriber QRZ Page

    Yes. MFG has been contacted. One relay and now another will be replace under warranty. However, this clearly is an RFI issue caused by the higher wattage amplifier. I'm not sure what the MFG could possibly tell me other than not use Ham radio amplifier. They have been helpful to say the least and given me ZERO issue with replacing the relays.
     

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