[RFI] MFJ 5008 ultrasonic receiver
Hare, Ed W1RFI
w1rfi at arrl.org
Mon May 23 08:06:38 EDT 2016
I agree, Mike. Ultrasonics give false positives on corona, and false negatives if something on the structure is blocking ultrasonic sound. I don't think that most hams need to use ultrasonic dishes. Once a ham identifies a pole, the utility must take it from there, and if a ham misidentifies something with the dish, and misidentifications are easy, and tells the utility to fix it, if it's the wrong component on the pole, the ham has made his problem worse because now the utility thinks they fixed it, did what the customer asked them to do and they will be reluctant to have to work on that pole more, now that the ham says that it's something else.
To hams: Find the pole if you can, but only by using signature analysis, comparing the time-domain signature of the noise at your station with the suspect noise you find in the field. If you do it any other way and send the utility to the wrong pole, they will not be cooperative when you have to change your mind. Once you find the pole, the utility can take it from there.
Ed Hare, W1RFI/6
From: RFI [rfi-bounces at contesting.com] on behalf of Michael C Martin [mike at rfiservices.com]
Sent: Sunday, May 22, 2016 4:42 PM
To: Hisashi T Fujinaka; HankP
Cc: rfi at contesting.com
Subject: Re: [RFI] MFJ 5008 ultrasonic receiver
As long as you aren't trying to locate a specific light bulb on a pole
you'll be OK!
There are two things to find concerning RFI sources on a pole, that's
sparking and corona. The biggest obstacle is to be able to differentiate
between the two and focus on the sparks. That's not too difficult. The
biggest mistake is not utilizing RF receivers to confirm the correct source
pole before using the ultrasound.
Sent with AquaMail for Android
On May 22, 2016 12:16:08 AM Hisashi T Fujinaka <htodd at twofifty.com> wrote:
> I haven't actually confirmed this completely, but I think my MFJ
> detector picks up a lot of RF that is above ultrasonic. Pointing it at a
> fluourescent fixture picks up a lot of buzz.
> I bought it as an experiment, figuring I have plenty of $200 toys that
> are less than useful. I wish you were closer (I'm in Portland, OR)
> because I'd just let you try mine out.
> On Thu, 19 May 2016, HankP wrote:
>> Bob -- I built the ULAD that was in QST some years ago and bought a
>> parabolic reflector from Edmunds --I can hear birds - crickets my steps
>> walking down the alley - two finger rubbed together at 200 feet - the wind
>> blowing if any wind - in all the time I have had it I have been able to
>> identify 1 piece of hardware on a pole . BTW I fiddled with a couple other
>> 40KHZ rx approaches - but essentially same results.
>> The APS RFI guys have the RADAR ENGINEERING ultrasonic receivers and they
>> are very marginally better than my homebrew.
>> They have a receiver now that is very effective - They can record the
>> waveform of the noise you hear - (they prefer to record from your antenna )
>> then go in search of that matching waveform. If I was going to spend any
>> serious dollars on finding powerline arcing - I would do someting that
>> duplicates that ability .
>> I have tuned loops - and an ICOM R10 rx which is pretty effective but
>> nowhere near as good as the APS receiver . Have you looked at W0IVJ's VDSL
>> recording with a SDR -- that plus some way to record the waveform would be
>> great .
>> 73 Hank K7HP
>> ----- Original Message -----
>> June QST has a review of the MFJ 5008 ultrasonic receiver. I am
>> thinking about getting one for locating sources of power line noise.
>> What do you think of this unit ?
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>> RFI at contesting.com
> Hisashi T Fujinaka - htodd at twofifty.com
> BSEE + BSChem + BAEnglish + MSCS + $2.50 = coffee
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