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$80 SA for EMI sniffing?




 
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Author Topic: $80 SA for EMI sniffing?  (Read 1363 times)
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K6JEK
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RF in the shack


« on: October 07, 2020, 05:22:01 PM »

I've noticed a couple of tiny spectrum analyzers for less than a $100 on Amazon. I thought one of these might be convenient for EMI searching. Anyone do that? Have a favorite?

The two I looked at are called TinySA.

https://www.amazon.com/gp/product/B08H11JDFN/ref=ox_sc_act_title_2?smid=ARRT83VWL9KVQ&psc=1
https://www.amazon.com/gp/product/B08FB5XT7B/ref=ox_sc_act_title_1?smid=A2IGB93YKR8R6H&psc=1
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W1ITT
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« Reply #1 on: October 07, 2020, 06:22:56 PM »

I got one a few days ago from R and L Electronics in Ohio, $50 plus shipping.  I think it was $56 total.  I've just used it on the included whip.  My plan is to build a terminated loop as well as an inductive probr to clamp over cables to chase RF nasties in the house and in the neighborhood.  Sensitivity seems more than adequate.
73 de Norm W1ITT
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K1JJ
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"Let's go hiking in the woods, Tommy!" - Yaz


« Reply #2 on: October 07, 2020, 07:33:39 PM »

Pretty slick looking device.

It's getting more like a Star Trek whirl all the time.   The cell phone is like a communicator,  i-pads look like their i-pads and now a mini spectrum analyzer is their tricorder.

I wanna order a warp drive for my truck -  from Amazon.

T
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed. 

Nothing like a new homebrew rig. Come into the shack, flip on the switches and everything works perfectly.

And, nothing like an old dog.
W1RKW
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« Reply #3 on: October 08, 2020, 08:59:19 AM »

I ordered one from R&L a couple of days ago.
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Bob
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His fear was when I turned it on for the first time life on earth would come to a stand still.
WA2SQQ
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« Reply #4 on: October 08, 2020, 06:58:26 PM »

You might want to know this before you order one

https://youtu.be/zGldCPqbjLA
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Opcom
Patrick J. / KD5OEI
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WWW
« Reply #5 on: October 08, 2020, 08:09:20 PM »

Amazing. The RF Explorer 3G Combo ran $289 and this one in the topic looks like it does the same basic things (less wifi channel analyzer) for 1/3 the cost. Progress seems to be made very quickly!
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Radio Candelstein - Flagship Station of the NRK Radio Network.
W2PFY
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« Reply #6 on: October 10, 2020, 03:33:13 PM »

.
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The secrecy of my job prevents me from knowing what I am doing.
W1RKW
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« Reply #7 on: October 12, 2020, 03:22:33 PM »

the TinySA arrived today.  Neat little instrument. got a little learning curve but I wandered around the house sniffing.  Nothing is affecting the radio but there a lot little nasties here and there.  And the screen isn't as bad as I thought.
 
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Bob
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Home of GORT. A buddy of mine named the 813 rig GORT.
His fear was when I turned it on for the first time life on earth would come to a stand still.
WA2SQQ
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« Reply #8 on: October 12, 2020, 11:21:13 PM »

I just might have to order one of these. Iíve got a few wandering birdies that Iíve been looking for
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W1RKW
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« Reply #9 on: October 14, 2020, 04:56:46 PM »

An ergonomic design improvement would be to put the connectors on top and controls and USB connector on either side.  Being a lefty (left handed) the antenna gets in the way.  
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Bob
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Home of GORT. A buddy of mine named the 813 rig GORT.
His fear was when I turned it on for the first time life on earth would come to a stand still.
W6TOM
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« Reply #10 on: October 14, 2020, 06:22:14 PM »

   Before I retired one of my jobs at the local power company was to handle RFI complaints, most were made by hams. I used a Radar Engineers Model 242 RFI Locator, this is a $8,000 piece of equipment, it came with a 300 MHZ to 1 GHZ log periodic antenna which I never used and a ferrite core "ball bat" antenna which was good from 300 KHZ to about 4 MHZ, that was VERY useful for locating once you were close to the source. The receiver covered from around 150 KHZ to 1 GHZ. Find that Wall Wart!!!

   It had a spectrum display with a sweep rate close to 60 HZ, filters for 60 HZ, a MANUAL GAIN CONTROL, an old fashioned ANALOG S METER and a speaker.

   The filters allowed me to determine if the RFI had a 60 HZ component, an indication of power line noise. The utility was responsible for its own RFI but NOT any other source and it was good policy to at least locate the non utility source.

   AGC is NOT your friend when looking for RFI, I could set the manual gain for an S meter reading, 20 on a scale of 0 to 100, the volume and then drive a power line. Some times the vehicle's own RFI was greater than what you were looking for but one could drive pole to pole and shut the engine off and see if the S meter reading had changed. In some cases you could just listen to the audio.

   I had 2 types of Outbacker Antennas I could mount on  ball mount at the rear of my company vehicle.

   One of my ham friends recently had a bad RFI issue of 40 meters, using an Icom handheld receiver and a loop antenna I could determine it was either the house on his left or right but the AGC action of the RX made further resolution impossible. He lived in a typical CA dense packed urban area, 50 X 100 foot lots. The area had underground utilities and I did not think the RFI was from that. He called in a RFI complaint to the local utility, when they responded the service man had a Model 242 but he didn't know how to use it. I came by and showed him how to use the equipment and it took me 5 minutes using the "ball bat" ferrite core antenna to determine it was the house on the right that was the source.

   My friend was on good terms with his neighbor and that night spoke to him, they had installed a CCTV system recently, the source was the Cheap S**t Wall Wart that powered the CCTV system.

   


* B2 Model 242.JPG (1338.95 KB, 2551x1427 - viewed 59 times.)

* B4 OutBacker1.jpg (603.59 KB, 1012x1777 - viewed 55 times.)
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WA2SQQ
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« Reply #11 on: October 14, 2020, 07:40:11 PM »

Whatís the deal with the ball batt antenna? Can it be built?
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W6TOM
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« Reply #12 on: October 14, 2020, 09:37:59 PM »

 The "ball bat" antenna comes with the Model 242 kit, it has a built in amp you can turn on or off. The Model 242 has been replaced by the Model 243, here is a link.

http://www.radarengineers.com/10-rfi-tvi-locators.aspx

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WA2SQQ
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« Reply #13 on: October 15, 2020, 04:51:45 AM »

I've located two noisy power transformers using am AM radio and a real "baseball" bat. When I located the suspected pole, I'd wack the pole with the bat and listen to the generated noise. You can hear the difference in the noise. On one occasion, a cop asked me what I was doing. When I explained he gave me a funny look and moved on.

I reported the noise to the local power company. They were skeptical until I mentioned that they could identify the pole by looking for a red light on the transformer. That got their attention and they explained that it indicated it was operating "over temp".

Later the engineering department called me to confirm how I found it. He never heard of the baseball bat trick!
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km6sn
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« Reply #14 on: October 15, 2020, 07:38:47 AM »

This is to describe a direction finding device is called a Villard Cage("CAGE" herein).

The CAGE is sharp enough you can find an offending power pole, and identify
which crossarm is the noise source, and even which side of the crossarm
is the noise source.

It was developed by Oswald Villard, probably while he was doing early
research on over-the-horizon radar.

Google Oswald_Garrison_Villard_Jr

I have tried in vain, but documentation on the CAGE is apparently lost to history.

WHAT IT IS

It is an electrostatically shielded dipole, with a VHF AM  receiver.

Imagine a section of rain-downspout, about 36 inches long. Now cap each end
with a pyramid of sheet metal. With that view in mind, image the CAGE being
built with wire-frame construction instead of a downspout-and-sheet-metal-pyramids,

SEE SOME PICTURES

See the attached pictures. Please be aware the four "box" shaped wire stiffeners
are for mechanical convenience only. You can place as many as you like in arbitrary
positions down the length of the CAGE.

A dipole is deployed down the center-line of the cage. At the center of the dipole
install a radio listening device where the red letter 'O' appears.

HOW I BUILT IT

I used #10 bare copper wire from Home Depot. I made the CAGE an arbitrary length, about
30 inches (limited by mechanical constraints). I made the cross section of the CAGE square,
but I am sure that is not critical. I suspended a dipole along the centerline
by using monofilament fishing line for end insulators. I used an old Radio Shack VHF AM
aircraft radio reciever, which I kind of jam-fitted inside the cage. Instead you could use
the $80 SA for EMI testing. The sensing receiver must be an AM receiver, or a device that
shows signal amplitude. IT IS IMPERATIVE THAT THE DIPOLE AND SENSING RECEIVER ARE
COMPLETELY INSIDE THE CAGE WITH NO CONDUCTORS EXITING THE CAGE!!

HOW TO USE IT

To use it, tune the VHF receiver to a frequency that sounds like the interference
you are getting at HF. Grasp the CAGE at the middle, at hold it at shoulder level,
pointing front-and-back, with the receiver near your ear so you can hear the
offending signal and see the direction the CAGE is pointing.

To find a noise source, rotate the CAGE both in azimuth and elevation until you find a deep null.
The CAGE has EXTREMELY deep and sharp nulls off each end. So,When the null is found, the CAGE end is pointing directly at the noise source.

In another post I will provide the 4nec2 file I used to create the geometric images. The 4nec2 file may not be
valid for modeling; I just used it as a convenient 3d visual model.

73, Rod KM6SN



* v1.png (17.41 KB, 1280x1000 - viewed 64 times.)

* v2.png (22.79 KB, 1280x1000 - viewed 50 times.)

* v3.png (28.21 KB, 1280x1024 - viewed 51 times.)
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km6sn
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« Reply #15 on: October 15, 2020, 07:44:45 AM »

The attached file named villard.txt should be changed to villard.NEC for use with 4nec2
Note that the file is provided as a visual aid only, and may not be a legitimate electrical model.

* villard.txt (1.33 KB - downloaded 23 times.)
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km6sn
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« Reply #16 on: October 15, 2020, 07:47:29 AM »

a fascinating read about early electronics, including HP:

https://ethw.org/Oral-History:Oswald_Garrison_Villard
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W1ITT
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« Reply #17 on: October 15, 2020, 08:49:42 AM »

Villard was a smart fellow, though his name is not well known among radio people.  While at Yale, he was the license trustee of the Yale amateur radio club.  The call sign was W1ITT.  It lapsed during the war years, as the term was five years back then and ham radio was shut down "for the duration".  I picked the call up almost twenty years ago as it seemed worth preserving.
73 de Norm W1ITT
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ka8gef
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« Reply #18 on: October 16, 2020, 07:35:35 AM »

How well would one of these Tiny SA's fit the bill and perform (vs. high end units) in viewing/aligning boat anchor receiver crystal based selectivity filters....i.e. Nationals, Hammarlund and the like?

Thanks.

ka8gef
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WA2SQQ
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« Reply #19 on: November 01, 2020, 10:42:37 AM »

Heres an interesting follow up video on some design limitations that pertain to AM  modulation. This guy has been doing many videos on the TinySA


https://youtu.be/uwXUZSdxNq4

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KA8WTK
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« Reply #20 on: November 01, 2020, 02:24:36 PM »

I purchased the one from R&L Electronics in Ohio. They are an authorized outlet for the tinySA and it was less than $60 with shipping from them.
Knowing this is a low cost unit I don't expect high end unit results. Reading the posts on tinysa@groups.io has been most helpful in understanding the units limitations and how to properly use it.
For finding interference, I built the unit mentioned in the ARRL article linked in this thread. http://amfone.net/Amforum/index.php?topic=46223.0
I substituted the tinySA for the transistor HF radio. I can actually null out the signal from the local FM broadcast stations when the whip antenna is pointed at their tower location. I also built a Faraday shield as mentioned in the article for over the antenna. The visual indication you get of the null makes it easy to work with.   
The next step is to find the source of the noise I have on 40 meters. I'll let you know how well it works.

Bill KA8WTK
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Bill KA8WTK
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