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Author Topic: RFI sniffer for drone  (Read 475 times)

NO9E

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RFI sniffer for drone
« on: January 06, 2021, 08:20:57 AM »

Has anybody thought of using a drone from RFI sniffing? The drone would carry an airband sniffer, with sound retransmitted on 70cm. The sniffer can possibly use the board from MFJ-856 but I am not sure about the 70cm transmitter. Is there a kit of a 70cm FM transmitter? I think 10 mW is enough.
The goal is to use the drone in rural areas.

Ignacy NO9E
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K6AER

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Re: RFI sniffer for drone
« Reply #1 on: January 06, 2021, 10:13:22 AM »

I live in a rural area and have had issues with power line interference. The AC interference tends to be vertical in polarization and can radiate in a very broad area from the arcing source along the power lines. As you get closer to the source the intensity will increase exponentially. Any receiver will have to have the dynamic range and be able to transmit the intensity accurately back to your receiver flight control location.  Area flight issues aside, I don’t think a RFI drone will be much or an asset.
I have found a small AM receiver, with a S meter (HT) on the aircraft band and a 3 element beam the best way to find AC interference.

A rising star in the RF amplitude interference problem is Solar Panels and their charge controllers and AC inverters. Government Solar Subsidies have enabled huge solar farms to be built next to residential areas with the interference levels to HF communication to render the usage of this RF mode unusable. Most often finding the interference is not as a big a problem is what to do about it. Compliance with part 15 of the FCC code means the interference must be under approximately S9 at 100 feet from the interfering item.  This is for a single item. Every time you double the number of interfering items the noise level goes up 3 dB. A large solar field can put out a breath-taking level of broad band digital noise.

Finding some intermittent noise can take a long time. Enlisting the aid or some knowledgeable locals can reduce the frustration with this problem.
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NO9E

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Re: RFI sniffer for drone
« Reply #2 on: January 06, 2021, 11:17:24 AM »

This area is rural, heavily forested, with few roads. Nothing strong heard from poles next to public roads. The suspect power poles are inside fenced private areas. Hard to find the tenants, and dogs and guns sounds are plentiful. The power company can fix but not find the source.

Ignacy, NO9E
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KG4RUL

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Re: RFI sniffer for drone
« Reply #3 on: January 06, 2021, 01:14:49 PM »

This area is rural, heavily forested, with few roads. Nothing strong heard from poles next to public roads. The suspect power poles are inside fenced private areas. Hard to find the tenants, and dogs and guns sounds are plentiful. The power company can fix but not find the source.

Ignacy, NO9E

How many points do you score for shooting down a drone?
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W6QW

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Re: RFI sniffer for drone
« Reply #4 on: January 06, 2021, 01:26:33 PM »

A couple of thoughts to consider:
1.  Before trying to implement a close-in sniffer approach, it would be beneficial to triangulate the approximate location(s) of the noise source(s).  A simple link-coupled tunable loop and a portable HF receiver would be all that is needed.  An RF attenuator would be beneficial but not mandatory to triangulate the approximate location(s). Google 'Magnetic Loop' for ideas.
2. There are many ways to implement a drone-based VHF sniffer but the less the incursion over private property will avoid that drone becoming a target practice object.  Making contact with a land owner before flying the drone over their property is a prudent approach but if you have a triangulation of the location, you lessen the number of subsequent steps necessary to find the root problem.
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NO9E

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Re: RFI sniffer for drone
« Reply #5 on: January 07, 2021, 05:57:39 PM »

I have more loops and other devices than anyone can imagine. I even tried 10el 2m antenna in AM mode.

This is a rural heavily wooded area. The noise is strongest on 15m and seem to be carried on by many poles. The noise changes direction as I walk. Some areas are inaccessible due to thicket/private land/dogs/guns.

Since there is not really strong VHF noise by the main road (but strong 15m noise), I think that an offending pole must be deep inside a private property. I don't know which one. 

So  small drone could be handy. There are telemetry radios that weight next to nothing. But in this case one needs VHF sniffer plus a transmitter. All perhaps 4 oz max.

Ignacy NO9E
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NO9E

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Re: RFI sniffer for drone
« Reply #6 on: January 17, 2021, 06:49:52 PM »

I found the noise using MFJ-856 by walking quarter mile from the main road on a private dirt road. The noise was coming from a pole next to an abandoned industrial building. That pole is 3/4 mile from home.

No need for drone anymore.

From the main road the signal from  MFJ-856 varied greatly every 10 ft with directions changing +- 30 degrees. The magnetic loop on 15m was catching every pole as apparently 15m seems to be resonant with the power transmission lines. Readings from MFJ-856 became consistent and strong only about 300 ft from the pole.

So the only solution in such a case is to cover every square of 600 ft with MFJ-856 until strong consistent readings. 

Ignacy NO9E
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RADIOPHONE

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Re: RFI sniffer for drone
« Reply #7 on: January 17, 2021, 08:44:02 PM »

You best just stay in the city where you belong.

As already said, that drone will likely get shot down...

and country folk usually are not happy when they find trespassers on their land,
nor strangers that look suspicious, doing weird things in their community.
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K6AER

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Re: RFI sniffer for drone
« Reply #8 on: January 24, 2021, 02:59:14 PM »

You best just stay in the city where you belong.

As already said, that drone will likely get shot down...

and country folk usually are not happy when they find trespassers on their land,
nor strangers that look suspicious, doing weird things in their community.

What is your ham call????
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RADIOPHONE

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Re: RFI sniffer for drone
« Reply #9 on: January 26, 2021, 06:43:20 PM »

Why did you purchase a Californee vanity callsign and then move out of the state?

Why do you say your say your silly *** motorbike will go 180 m.p.h. ?

Why do you use maggy mount antennas ?

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K6BRN

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Re: RFI sniffer for drone
« Reply #10 on: January 26, 2021, 06:56:50 PM »

Hi Ignacy (NO9E):

Glad you found the noise source!  Has the utility company responded to your new info?  15M is very alive (I worked 10M-80M today, with a lot of contacts) as the sunspot cycle ramps up.  Seems like it would be important to fix.

Brian - K6BRN
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WA8NVW

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Re: RFI sniffer for drone
« Reply #11 on: January 26, 2021, 07:59:31 PM »

Has anybody thought of using a drone from RFI sniffing? The drone would carry an airband sniffer, with sound retransmitted on 70cm. The sniffer can possibly use the board from MFJ-856 but I am not sure about the 70cm transmitter. Is there a kit of a 70cm FM transmitter? I think 10 mW is enough.
The goal is to use the drone in rural areas.

Ignacy NO9E

Hi Ignacy (NO9E) -
I don't understand why you would want to use an aviation band 118-136 MHz AM receiver aboard the drone. And the FCC prohibbits rebroadcasting signals from the aviation channels into the UHF amateur band. But I am glad you safely identified the noise source. Let's hope the utility gets it fixed quickly.
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N5KO

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Re: RFI sniffer for drone
« Reply #12 on: January 27, 2021, 10:37:08 AM »

Congrats on identifying the source.

Another option is to take a look at the MFJ-5008 or similar ultrasonic setup.  The local power company uses ultrasonic gear from Radar Engineers for noise hunting.

Ultrasonic noise does not propagate down the power lines, so when find the buzz you know you are at the noise source rather than chasing shadows.  Of course there may be multiple noise sources as well.

Happy hunting!

I found the noise using MFJ-856 by walking quarter mile from the main road on a private dirt road. The noise was coming from a pole next to an abandoned industrial building. That pole is 3/4 mile from home.

No need for drone anymore.

From the main road the signal from  MFJ-856 varied greatly every 10 ft with directions changing +- 30 degrees. The magnetic loop on 15m was catching every pole as apparently 15m seems to be resonant with the power transmission lines. Readings from MFJ-856 became consistent and strong only about 300 ft from the pole.

So the only solution in such a case is to cover every square of 600 ft with MFJ-856 until strong consistent readings. 

Ignacy NO9E
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NO9E

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Re: RFI sniffer for drone
« Reply #13 on: March 20, 2021, 07:35:17 PM »

Once I called the power company in the morning, they disconnected the pole in the afternoon.
The dish MFJ-5008 is supposed to find the exact spot where it spark withing a  few inches. So once the pole is found with MFJ-856, MFJ-5008 can follow up. My MFJ-5008 must a Friday PM type, as it does not show a sharp peak.

Ignacy NO9E
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