Hi Alan
I have played around a lot with ultrasonic detection. I have access to a UE
systems Ultraprobe 15000 with its Dish the UWC. I also have number of homebrew
ultrasonic amplifiers and dishes. I also have access to a RE M331.Ultrasonic
sound has a limited propagation range that is dependent on temperature,
humidity and frequency.(the laws of physics) Buying an expensive equipment like
the Radar Engineers 251 or even borrowing one would not offer you much
advantage over a homebrew detector like the W1TRC design that was published in
QST. The MFJ5008 looks to be almost the identical circuit to the W1TRC design
that was published in QST. If you were using this equipment regularly it might
make a good investment.A good unit if you can find it is the old Techsonics
Sontector ultrasonic leak detectors. This is the Model with the square Midland
brand panel meter on the unit in the Bird like leather case. The newer models
have a different circuit and does not behave like a receiver in terms of
its response. Its very peaky like it has squelch on the detector. The older
model has a nice meter response much like a receiver and you can easly screw
any 40khz detector into its input. It also has good sensitivity. Email me if
you want a picture of one.Since ultrasonic is essentially short range, having
expensive overly sensitive equipment almost serves no purpose. In the ARRL
review of the MFJ5008 they quoted a range of 200 ft, which on a true 40khz
ultrasonic signal outdoors is almost impossible to achieve based in my testing
using a UE systems 40khz signal generator and the UWC 18inch dish. If I cant
hear it on the W1TRC, I cant hear it on any other dish size or amplifier. I
even doubt that the Radar Engineers would be able to hear a weak signal that
these dishes wont detect. I believe the Radar Engineers uses a 25khz(not sure)
sensor. The UE systems Ultraprobe can vary its received frequency from 22khz
to higher than 50khz with phased detectors.
The ARRL used a T model Ford arcing source which is loud as hell. I used both a
T model coil, Wimshurst spark generator, and a spark plug tester to try and
generator a weak signal source.(This is difficult, to try and emulate a weak
signal insulator leak) Everything generates ultrasonic noise these days. After
all my testing, range is subjective and depends on many variables. Ultrasonic
is essentially a very short range detection device(less than 30 metres or 100
feet) for reliability. A proper true parabolic dish shape is more important
than long range sensitivity.
When I have found Ultrasonic to be effective the dish is effective under 100 ft
and most of the time especially when you use a UHF receiver like the RE330
you will be within 1 or 2 poles distance of the interference. Its then a easy
job to point the ultrasonic dish to ID the pole or hardware. You would very
lucky if you could detect ultrasonic from long distance off, like across
several road lanes. Wind and obstructions severely affects ultrasonic sound
range.
In short dont waste too much effort on Ultrasonic devices. A homebrew W1TRC
design is good enough for telling the utility " I detected ultrasonic noise
near the pole" The MFJ5008 is probably good enough for this. If you going down
the homebrew path it may be worth playing around with MEM's ultrasonic mics. As
far parabolic dishes go. The more convenient of my receiver dishes are the old
Sony PBR330 and PBR400(30cm and 40cm) parabolic mic dishes and make good
dishes if you can find them at non auction site stupid prices. I also have a
Edmund scientific true parabolic dish which in VK was a dangerous thing
because of the sun. Its a very powerful reflector. I have had numerous
accidents setting things on fire with this dish until I painted it matt black
to stop it acting like a solar furnace. I also tried the squirrel baffle dish
which works ok, however you want to try and get a true sound parabolic shape
dish. I make these comments while using a UE systems Ultraprobe 15000 with a UW
C dish as a reference standard. Last time I checked this kit was about 15,000
US dollars(it belongs to the work QTH). Its far more sophisticated than the
RE251 and its supposed to be the most sensitive phased detector on the market.
I am not trying to promote the company I just want to tell you that a W1TRC is
good enough and has the about same detection range. Even with my 30cm parabolic
mic dish I can detect anything the UE system dish will detect under 100 ft. The
UE might out perform it out at 200ft but this not a 160 CW weak signal
detection competition! Is there ultrasonic noise yes or no, in my view thats
how ultrasonic should be used unless you are up on the pole in a cherry picker.
UHF is far useful. The RE 330 and 331 use the range of 330 to 340mhz for the
receiver. Anything from 200mhz to 440mhz works. The 330mhz range in my
experience seems to good frequency range for picking up a wide variety of
noise and seems to be upper limit of many noise sources. That is not say things
like arcing sources cant go higher. The RE331 has very good pulse detection
and a AGC that responds very well to sparking pulse like noise. In contrast
many receivers will smear or average this sparking noise out because of AGC or
peak detector response. The RE330 is a tool that does its job well. However
ordinary UHF AM receivers will get you there. I leave my receiver tuned to
406mhz which is the international 406 EPIRB satellite frequency, its reserved
globally and its close to performance in terms of detecting sparking noise
like the 330mhz range while not being too high like 440mhz where you may hear
nothing. It amazes me how much RFI you hear up on 330mhz that is being emitted
by modern trucks, buses, LED road signs, hazard flasher beacons, roadside LED
generator lighting sets etc etc. 144mhz pickups all this stuff from a long
distance away and the 330mhz will tell you if you are close by, which in
essence is the secret of RFI location, localising and getting as close to the
source as possible.
Getting any information on the Radar Engineering products is just about
impossible from my experience. Finding manuals is also just about impossible.
The other thing to be aware of is many of there HF receivers like the 242 and
243 tune in 12.5khz steps, so many sources of interference cant be tuned in
since the noise is on frequencies between the tuning steps. This comment also
applies to some VHF/UHF HT ham radios that dont have 1 khz tuning steps which
can be useful for tuning in switch-mode led power line birdies and hash peaks.
It does not matter for arcing sources since its broadband in nature.I have
wasted a lot of time hunting qrm and messing around with different types of
equipment to find an effective solution which is as cheap as possible. I was
just fortunate enough to have access to very good equipment to realise what is
possible. Results can be achieved with ham methods and ham budgets. Extremely
high price tags do not always mean best performance, thats life!73Craig""
"""*INTERESTING ASIDES*:
- Ultrasonic dish. I mentioned that a previous attempt with an
ultrasonic dish some years back had been disappointing. He said this was a
new version (Radar Engineers) dish.
- And, that the upgraded version had been recommended by a contractor
the utility had recently used to survey their powerline.
- The survey had been prompted by a series of "pole fires" they had
experienced.
- He described the survey as having been done from a vehicle driving
beneath 200 miles of their lines. (1/5 of the utility's total). And, that
the contractor had then used this latest model R.E. dish to zero in on the
source. Future surveying depends upon budget considerations.
*I'M CURIOUS*:
- Is there some new technology being used for surveying lines? I sort
of recall reading something like this. Drones? SDR recording?
- Or, maybe this is just some guy driving around with his AM radio on?
- Is there a new version of the ultrasonic dish that is better than the
previous Radar Engineers model?
- What is the difference between RE models and the MFJ-5008?
https://mfjenterprises.com/products/mfj-5008
I will further update when these tickets are closed out - and the defective
component is positively identified.
73, ~ Alan K0AV
Colorado Springs """
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