Help for F70 EMI/RFI chatter - try this...

[kascinoh]

Hi all - thought I'd post a note here to F70 owners who are having difficulty with EMI/RFI chatter with their units. In the urban environment that I hunt in, this was a big problem for me - until now.

I took a RFI choke off of one of the audio lines to some of my shortwave radio gear, and snapped it on to the coil lead-in just before the control housing on my F70.

Did this solve my chatter problem with EMI/RFI? No, but the chatter was greatly reduced.

In my backyard, with powerlines 50' away and the ugly gray-cylinder transformer on the power/phone pole, I could only run 40 sens and -5 thres. before I got chatter - making the machine virtually useless. Now, I can run the F70 at it's default settings, 65 sens and -3 thres. with no chatter - a huge difference in my yard, anyway.

With the rain stopping today, I took the '70 with choke out to my favorite park. Before, I could run here at 70-75 sens with -2 thresh., but that was max before chatter was overpowering. With the choke, I can run it wide open - 99 sens and +1 thresh. before I get chatter.

If you are sick of the chatter from EMI/RFI in your area - give this a try - I feel it's worth the $5.99 these ferrite chokes go for at Radio Shack.

Oh, and no, it doesn't affect GB, depth, or target ID at all, as far as I can tell.

Let me know your results !!

 

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[Lowbatts]

Thanks! Excellent idea.

I can normally run my rig pretty hot, close to wide open but today I was working just such a spot at an old RR depot. Not just cinder and coal but noisy wires overhead and by the time I got the rig quiet it was running pretty low on sense, pretty high on thresh, and still talking back a little.

 

[Jeff In North Georgia]

Where can you buy these?
How much are they?

Thanks!
Jeff

 

[mikewaz]

Thanks for the tip!

I tried it last night in my yard and it seemed to make a difference. Even with a 5" coil I could only run my sens at around 40 - 45 but I had it up to 65 last night. Too bad there's nothing left in my yard .

I plan to try it again this weekend near some high tension lines that have been giving me big problems with EMI. If it works it's gonna open up some new territory for me.

Mike

 

[Sandman]

http://www.fisherlab.com/hobby/davejohnson/Electrical Interference.htm

 

[Lowbatts]

I'm just wondering if they've tried a VM or vapor deposition process. Used on cell phones for both SAR and EMI purposes, it's a quick process that does not reduce real estate or add any significant mass or weight.

 

[George (MN)]

Thanks for an excellent idea. Another thing to try, if you want to detect a nearby place repeatedly, but there is extreme electrical interference on the detector every time, bring along a pocket radio to confirm the noise is bad. Check the noise at the highest frequency you can hear it, start walking different directions & hear if it goes away or gets stronger. Or drive & use vehicle radio.

Once you determine the area where it is the worst, call your power company & ask for the radio interference expert. They really will come out & fix it, as valuable electricity is often escaping. Noise got so bad here I couldn't stand trying to listen to much on the radio. Turns out the insulator on the power pole in the corner of our yard had a big hole in it, so they replaced it. Now I can listen to the radio & use a backyard test garden. HH, George (MN)

 

[X-Terra70_TreasureHunter]

You can get those chokes from Radio Shack

http://www.radioshack.com/search/index.jsp?kwCatId=&kw=rfi choke&origkw=RFI choke&sr=1

Dave

 

[N2CU]

Radio Shack is the easiest source of split clamp ferrite cores. Old computer VGA cables have solid encapsulated ferrite cores at each end. Remove the covering and cut the cable to remove them. Of course, you then have to remove your searchcoil connector to slip the core on and then reattach it. You can usually find all the cores you could ever need at Ham Radio Flea Markets (Hamfests). I bought a package of five for $1. The ferrite cores work by creating a high impedance to any noise coming into the detector on the outside of the searchcoil cable. Therefore, it works best when placed as close to the detector circuit board(s) as possible.