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[ve8xj]

I blems but  important of all SOLUTIONS ?

[K1JJ]

When you mention "error signal" and "overheat alarm" this says there probably are solid state chips and circuitry in there.

You might make sure it is in a metal box and shielded well for RF. Also most likely the RF is getting in through external input and output leads. Get some ferrite cores (type 43) and wind each input and output lead separately 5-8 turns thru each core. The bypass caps are a good thing and well work in conjunction with the cores as overall RF filtering. 

If you have connectors on the leads making it diifcult to wind closed cores, use the split cores and wind some turns on them before snapping shut.

T

[KA2DZT]

Make sure all the fittings on the metal chimney are well connected together.  Not sure what the chimney looks like but if it's typical duck work used in heating and AC systems,  loosely fitting duck work can generate harmonics at the connection points, especially if the antenna is close to the chimney. The RF gets coupled to the chimney stack.  Is the chimney well grounded??  Maybe try grounding the chimney to your station ground system.

Another solution would be to only operate your station in the summer.

[Detroit47]

Get some ferrite cores (type 43) and wind each input and output lead separately 5-8 turns thru each core.

I would use type 73 materials. I spoke to the manufacturer about a RF problem on 75. He said that type 43 wouldn't do much of anything if I wanted results use type 73; I did and was happy with results. Check out link to chart Attenuation RF Noise (MHz)”  is the important figure for your application.http://www.bytemark.com/products/fermgprp.htm

73 John N8QPC

[WQ9E]

You may also find it useful to use a scope to try and identify RF hot spots in the control system wiring.  I would suggest either a 10X probe with an insulation piercing tip or if the individual wires are easily separated you can use a pickup loop next to the wire (also handy for seeing how much RF is on your ducting).  This is one of the cases where you will want to choose AC coupling.  Although triggering isn't really important for this work if your time base has a LF reject selection use that to reduce triggering from the heater controller internal data.

Have a couple of the ferrite clamps (I imagine this is something you can even get at Radio Shack) so you can quickly reduced the RF and find all of the hot spots.

[Detroit47]

Have a couple of the ferrite clamps (I imagine this is something you can even get at Radio Shack) so you can quickly reduced the RF and find all of the hot spots.

Most of the ferrite clamps are aimed at the CB market and are type 43 not much good for 75 and 40 meter use. I went through a bunch of different ferrite stuff until I found out what worked. I have about 30 of those clamp on things and they don't do squat on 75.

N8QPC

[WQ9E]

My problem was a couple of appliances radiating interference on 160 and 80 causing receive problems and the clamps worked fine for me there and they also took care of 75 meter RF tripping one GFI outlet.  I may have gotten lucky and picked up some that had the proper ferrite composition.  I got mine several years ago from either Alltronics or Allelectronics, I can't remember which one.

[K1JJ]

Hmmm... Type 43 is what we use for class E rigs on 160- 40M almost exclusively.   Maybe this is because of the requirements not to saturate under high power - whereas when used as a low level noise filter, the permability can be raised way up since saturation is not an issue ?  (Type 73)

T

[Detroit47]

Hmmm... Type 43 is what we use for class E rigs on 160- 40M almost exclusively.   Maybe this is because of the requirements not to saturate under high power - whereas when used as a low level noise filter, the permability can be raised way up since saturation is not an issue ?  (Type 73)

T

I agree with you on that matter. Since you are not trying to make a choke that is resistive to said frequency. But rather transfer power as a transformer. I spent a lot of time researching the matter so I could get out of our computers at home.
I spent a lot of money on the clamp on ferrites and they didn't work for me. So I explained my problem to the fellow at ByteMark and he recommended the 73 material to me. All I know is it worked for me.
73 N8QPC

[K1JJ]

Wish I was aware of that before myself.  I ordered (qty 55) type 43 cores and snap-ons to shotgun filter my whole station when I first built my class E rig. I had high power PDM pulses getting into the homebrew VFO and protection circuitry. The capacitor bypassing helped a lot, but the ferrite treatment using the type 43's was marginal. It helped a little bit, but required more turns around the cores than I wanted to do, as you'd expect. Anyway, in hindsight, yes, the higher permability would have been better for my low level problems and for VE8XJ's situation.

Thanks for the heads up!

T

[ve8xj]

blurp

[flintstone mop]

Your description sounds like RF pickup in the control wiring or power supply. Any wires into or out of the 'brain' will bring RF in and lock it up.
Check that all wires are used in any control wiring. Unused wires will be antennas for the control circuits and will kill them.
The .oo1 bypassing does not always work. The other replies about ferrite is the best way.

FRED

[K5WLF]

I'm going to try putting some ferrites on my WX station cables. Every time I key up on HF I 'make' 6" of rain.

ldb
K5WLF

[flintstone mop]

I'll have to do the same here. When I use my vertical legal limit AM or LSB on 160M the display blanks out,,,,,nothing but dashes. The antenna is 500 feet away from the house.
Fred