[RFI] RFI Digest, Vol 220, Issue 7
Joe Locascio
pvjoe at yahoo.com
Sun May 9 13:00:31 EDT 2021
WHAT is a 'strong arc'???
Joe
On Sunday, May 9, 2021, 09:00:37 AM PDT, rfi-request at contesting.com <rfi-request at contesting.com> wrote:
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Today's Topics:
1. Re: Next step visually sighting arc's (David Eckhardt)
2. Re: Next step visually sighting arc's (Charles Plunk)
3. Radar Engineers Model 251 Parabolic dimensions? (Charlie Delta)
4. Re: Radar Engineers Model 251 Parabolic dimensions?
(n0tt1 at juno.com)
5. Fwd: RE250 Sighting? (Charles Plunk)
----------------------------------------------------------------------
Message: 1
Date: Sat, 8 May 2021 16:48:19 +0000
From: David Eckhardt <davearea51a at gmail.com>
To: Charles Plunk <af4o at twc.com>
Cc: "rfi at contesting.com" <rfi at contesting.com>
Subject: Re: [RFI] Next step visually sighting arc's
Message-ID:
<CAODdWWE0tJP1pRHH_6-2KVuukKroZyQxM0adkB==asj045DfWg at mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
Instead of the 'rifle' scope, I'd suggest something a bit more capable with
a larger aperture. I have the Celestron Ultima 65 used for this purpose
and many others. The 65 mm objective is excellent, it can be either
hand-held or tripod mounted, and costs a bit less than twice your 'rifle'
scope (in the $100 to $150 range, store dependent).
Dave - W?LEV
On Sat, May 8, 2021 at 3:13 PM Charles Plunk <af4o at twc.com> wrote:
> As you may remember, I sighted my first strong arc with binoculars after
> triangulation, ultrasonic, etc. Its been fixed by the util for over a
> month and still gone gone :-)
>
> A not near as strong arc is on the same pole but on the opposite side.
> This pole is in the corner of my backyard so makes it convenient to
> experiment with. Playing with the success of the first, I tried
> binoculars and thought, with some imagination that I could see this arc
> too. Its tiny.
>
> So, I bought a stronger spotting scope, like you sight in rifles with.
> And mounted it on a tripod. Last night the source was active and still
> think I see it in the same spot. A crusty old ground lug wired to the
> bottom of a fused disconnect. Connects to the wire stapled to the pole.
>
> One has to be careful as reflections off the ceramics from distant
> street lights (~200' away) can look like arc's. But a crusty ground lug
> should not reflect. This area is also where I hear it with ultrasonic.
> Its a very narrow place to stand on the ground to hear it with
> ultrasonic. Another issue is its so dark its hard to make out the
> outlines of the pole in the dark to tell where you are seeing. But I
> could see enough. The bigger the lens on the front of the
> scope/binoculars the better to capture more light to see the pole I
> suppose.
>
> My experiments so far with digital cameras, one with the IR/UV filters
> removed, have resulted in failure. Cannot even see the pole in the dark.
> Nothing but a grainy picture. Even trying to capture a picture through
> the scope. The scope came with a phone mount for capture.
>
> I am going to look at the same spot when the source is inactive. If the
> suspected tiny arc is absent then going to request the util replace that
> connector unless anyone has any further suggestions.
>
> The spotting scope I bought was ~$60 so another low cost tool maybe for
> your rfi toolbox.
>
> Underneath this one, at night I am hearing a repetitive noise. One
> minute on ~0.5 - 4 seconds off. But thats another story, lol and does
> not sound like power line arc.
>
> Chuck
> W4NBO
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
--
*Dave - W?LEV*
*Just Let Darwin Work*
------------------------------
Message: 2
Date: Sat, 8 May 2021 12:46:48 -0500
From: Charles Plunk <af4o at twc.com>
To: David Eckhardt <davearea51a at gmail.com>
Cc: "rfi at contesting.com" <rfi at contesting.com>
Subject: Re: [RFI] Next step visually sighting arc's
Message-ID: <5beb9125-e7ac-7ce9-8ce2-d3503fd624a5 at twc.com>
Content-Type: text/plain; charset=utf-8; format=flowed
Thanks Dave. Its a spotting scope. Like the ones you look downrange at
the target to see where you hit and not the scope mounted on a rifle.
This is the one I have;
https://www.amazon.com/dp/B0728C4K7W?psc=1&ref=ppx_yo2_dt_b_product_details
Wish i had not sold my high dollar leupold rifle scope I had years ago.
It could almost see in the dark. I could see almost nothing in fields in
the dark but looking through that scope could easily see.
Chuck
W4NBO
On 5/8/21 11:48 AM, David Eckhardt wrote:
> Instead of the 'rifle' scope, I'd suggest something a bit more capable
> with a larger aperture.? I have the Celestron Ultima 65 used for this
> purpose and many others.? The 65 mm objective is excellent, it can be
> either hand-held or tripod mounted, and costs a bit less than twice
> your 'rifle' scope (in the $100 to $150 range, store dependent).
>
> Dave - W?LEV
>
> On Sat, May 8, 2021 at 3:13 PM Charles Plunk <af4o at twc.com
> <mailto:af4o at twc.com>> wrote:
>
> As you may remember, I sighted my first strong arc with binoculars
> after
> triangulation, ultrasonic, etc. Its been fixed by the util for over a
> month and still gone gone :-)
>
> A not near as strong arc is on the same pole but on the opposite
> side.
> This pole is in the corner of my backyard so makes it convenient to
> experiment with. Playing with the success of the first, I tried
> binoculars and thought, with some imagination that I could see
> this arc
> too. Its tiny.
>
> So, I bought a stronger spotting scope, like you sight in rifles
> with.
> And mounted it on a tripod. Last night the source was active and
> still
> think I see it in the same spot. A crusty old ground lug wired to the
> bottom of a fused disconnect. Connects to the wire stapled to the
> pole.
>
> One has to be careful as reflections off the ceramics from distant
> street lights (~200' away) can look like arc's. But a crusty
> ground lug
> should not reflect. This area is also where I hear it with
> ultrasonic.
> Its a very narrow place to stand on the ground to hear it with
> ultrasonic. Another issue is its so dark its hard to make out the
> outlines of the pole in the dark to tell where you are seeing. But I
> could see enough. The bigger the lens on the front of the
> scope/binoculars the better to capture more light to see the pole
> I suppose.
>
> My experiments so far with digital cameras, one with the IR/UV
> filters
> removed, have resulted in failure. Cannot even see the pole in the
> dark.
> Nothing but a grainy picture. Even trying to capture a picture
> through
> the scope. The scope came with a phone mount for capture.
>
> I am going to look at the same spot when the source is inactive.
> If the
> suspected tiny arc is absent then going to request the util
> replace that
> connector unless anyone has any further suggestions.
>
> The spotting scope I bought was ~$60 so another low cost tool
> maybe for
> your rfi toolbox.
>
> Underneath this one, at night I am hearing a repetitive noise. One
> minute on ~0.5 - 4 seconds off. But thats another story, lol and does
> not sound like power line arc.
>
> Chuck
> W4NBO
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com <mailto:RFI at contesting.com>
> http://lists.contesting.com/mailman/listinfo/rfi
>
>
>
> --
> *Dave - W?LEV*
> /*Just Let Darwin Work*/
>
------------------------------
Message: 3
Date: Sat, 8 May 2021 23:34:30 +0000 (UTC)
From: Charlie Delta <vk3od at yahoo.com>
To: "rfi at contesting.com" <rfi at contesting.com>
Subject: [RFI] Radar Engineers Model 251 Parabolic dimensions?
Message-ID: <521177757.304660.1620516870639 at mail.yahoo.com>
Content-Type: text/plain; charset=UTF-8
Thanks to all that replied.
1. Midnight sciences have closed down W0xi has retired and no longer sells kits or dishes.
2. I appreciate all the suggestions for a parabolic dish source. However I more interested in spending money on a true parabolic shape with the right F/D ratio. Its a fruitless exercise building good electronics on an imperfect dish? geometry platform
3. I have gone down the road of trying, wok lids, Skylight domes, Cake display stands, salad bowls, Sony parabolic dish, and all sorts of? odd objects that have a half decent parabolic shape. Sure it? works however range and sensitivity wont get near a Radar Engineers or even a MFJ5008. Even the ARRL review of the MFJ5008 mentioned that the Radar engineers had a detection range of in excess of 200 ft whereas the MFJ? units range was in the 100 to 150 ft range. Other professional? dishes by companies like SDT and Sonaphone in Germany have? stated specifications of 50 to 100ft for electrical airborne dischare detection.? Even the Super Fluke ii910? that costs 30,000 dollars has a range of 70 meters.
4. I used a weak signal Sparak source which was an iridium spark plug and my Associated Reseach 15KV Hypot to generate a test signal. If the signal is strong enough any scrap dish will hear it, even with a funnel as a dish! However when you want to hear a weak signal then the whole setup becomes important and the dish design becomes critical to the success of detection. Sounds a lot like ham radio and having the right antenna!
5. What is clear is that? anything parabolic in shape works however the sensitivity and directivity? varies a lot to the point of causing? frustration.
6. Symptoms? include weak? signal detection,?? washed out signal detection ability? and off axis? sidelobes which make the device usesless for pin pointing.
So with all of the above in mind I wanted a fresh start? by 1st building a proper dish. There are a number of parabolic dish sources availableI am more interested in experimenting by trying to building something that works. After shippings costs and paying the high prices in US dollars its really cheaper for me to get something molded locally by a plastic molding specialists who do this kind of thing everyday.
7. For those wanting? a really good dish thats optimum you can buy one from Wildtronics. There webpage has some excellent information on parabolic dish design which I used as a reference. http://www.wildtronics.com There is another company on Italy called Dodotronic that makes nice ultrasonic mic's and also sells optimum parabolic dishes.
8. I have 2 X Sony Parabolic mics 330 and 400 models which are 33 cm and 40cm's in diameter. These have a far from optimum FD? ratio and work no better than random junk dishes. Most parabolic mic's on the market ? have poor dish designs and only the specialist wildlife people have taken care with the design paramters(Telinga and Wildtronics)
9. If someone does have access to the Model 251 and if they could measure the dish depth and focal point since this would give us the optimum dimensions for the correct size dish for 40khz frequency and with the correct F/D ratio.
10. Every time that you drop the dish size by 10 cm in diamter the gain drops 6db according to the research. This suggests that the radar engineer size of 18 inches? or about 50cm is close to optimum.? A 60cm dish would be even better.11. The critical part is the illumination of the Mic or transducer and this is where building a proper parabolic dish with the right? FD ratio and focal point will reap rewards.
If all else fails I will sell the house and buy a Fluke ii910.
73CraigVK3OD
------------------------------
Message: 4
Date: Sun, 9 May 2021 02:02:00 +0000
From: <n0tt1 at juno.com>
To: vk3od at yahoo.com,RFI at contesting.com
Subject: Re: [RFI] Radar Engineers Model 251 Parabolic dimensions?
Message-ID: <AABSKQSZWAAZ8UJ2 at smtpout03.vgs.untd.com>
Content-Type: text/plain; charset=utf-8
The RE 250. I have one. The dish dia measures 18" and the depth is
4-3/8".
The transducer opening is just over 4-3/8". The opening of it's housing
is
level with the dish when viewed across the dish opening. Hope that
helps.
I'll repeat the gist of my previous post on the squirrel guard. It works
VERY well
as a US dish. It has pin point accuracy! It's easy to check the focus
of
any dish that has even a somewhat reflective surface. Clear plastic
dishes
are in that group. Set the dish up on a tripod in a darkened room. Set
up
a light source, such as a flashlight (AKA a "torch") say, 50 ft away and
aimed
toward the dish. View the concentrated light "falling" on your detector.
It
should fully illuminate it without blowing by the detector. It should
NOT be
a single point of light, but instead, illuminate the entire surface of
the detector.
Don't have a detector yet? Just use a piece of white paper and do
whatever physical measurements
you want. You can even do this at your local store to check the focal
length, etc.
I've done that. The dish, of course, must be pointed directly at a light
source.
Will this work outside, pointing at the sun? Yes, but it may set the
paper on fire!
Now a few words on the detector electronics. First off, don't bother
setting
up a dish to bench test. Whatever detector circuit you use should be
sensitive enough to hear (loudly!)
your fingers rubbing together at a distance of at least 10 feet. That's
with NO dish
attached. No kidding. You should hear virtually no "rushing" noise when
the
transducer/circuit is NOT receiving a US signal. IOW, the circuit should
have very good S/N ratio.
Do all of that and you'll have the most sensitive US detector you could
buy.
73,
Charlie, N0TT
On Sat, 8 May 2021 08:08:44 +0000 (UTC) Charlie Delta via RFI
<rfi at contesting.com> writes:
> Hi
> Can someone who owns a Radar Engineers model 250 or model 251
> Ultrasonic RFI receiver kindly tell me the dimensions of the dish?
> I am particularly interesting in the dish depth and the focal
> distance point. I understand that dish is 18 inches in diameter.
> The plan is to get a suitable parabolic dish molded by a local
> Dome skylight maker who thinks that he can mold a suitably
> accurate true parabolic dish.
> I am curious to know if the Radar engineers dish falls within the
> 0.5 to 0.6 F/D ratio? Since it works so well I thought I might as
> well start off with a set of dish dimensions that is proven to work
> around the 40khz Ultrasonic frequency.
> Since the beam-width is so sharp , I presume that the dish
> dimensions and the illumination from the dish of the ultrasonic mic
> will be critical. I have already played around with the W1TRC
> detector and various odd ball dishes and the results have not been
> that great since these dishes have a far from optimum F/D ratio.
> From playing around it seems that a deep dish with the focal point
> deep within the dish produces a very poor result and may even
> produce minor sidelobes that causes confusion. Depending on the
> strength of the signal, an ultrasonic signal can disappear because
> of the poor illumination of the microphone sensor. So it does
> appear that an optimum f/d ratio dish would produce a better result.
> Any input or comments would be welcome from anyone who has tried to
> build a similar project.
> (pick your mould VS mold spelling)
> 73CraigVK3OD
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>
------------------------------
Message: 5
Date: Sat, 8 May 2021 22:29:33 -0500
From: Charles Plunk <af4o at twc.com>
To: Rfi List <rfi at contesting.com>
Subject: [RFI] Fwd: RE250 Sighting?
Message-ID: <a07cb58f-19d1-8850-b7c3-3a123fd445e7 at twc.com>
Content-Type: text/plain; charset=utf-8; format=flowed
My dish, from the W1TRC QST article, is exactly those dimensions. Great
info on the electronics Charlie. I'm sure I have room for improvement
there. How does the RE250 sight with pinpoint? Crosshairs? rifle type
sights? The W1TRC you simply are looking through a hole in the back with
the transducer in the middle. Not much of a accurate sight.
Chuck
W4NBO
On 5/8/21 9:02 PM, n0tt1 at juno.com wrote:
> The RE 250. I have one. The dish dia measures 18" and the depth is
> 4-3/8".
> The transducer opening is just over 4-3/8". The opening of it's housing
> is
> level with the dish when viewed across the dish opening. Hope that
> helps.
>
------------------------------
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