Radio Jamming

[wb4bsd]

Okay, I need some techy help.

I does an agency combat against RF Jamming? I cant get into specifics do to INFOSEC.

[spareparts]

Okay, I need some techy help.

I does an agency combat against RF Jamming? I cant get into specifics do to INFOSEC.

4 Basic Methods:
Brute force - use more power then jammer
Change Frequencies (hopping)
Spread Spectrum
Find & eliminate source.

Without more detail, it's hard to figure out a solution. BTW, the ham radio community may be a resource in finding the jammer. Consider it a fox hunt where you get to jail the fox.

Martin

[wb4bsd]

okay, we use analog vhf. would switching to astro digital help any when it comes to jamming? what about using DES secure?

And lets assume that the person jamming is using something simple such as a white noise generator that covers a broad band.

What if the power level of the radio system was greater than the generator pwoer, would that help?

I am at a loss becuase i have never delt with anything like this before and the question was asked to me and i could not provide a good answer.

[wb4bsd]

Fox hunting isnt an option. This would have to be done in a matter of minutes vice days.

[spareparts]

Rusty,
Any form of encryption is not going to help if the jamming signal simply is stronger then yours. Strongest signal wins, so to speak.

If the signal is continous, it should be a quick job to track it.

Martin

[n9upc]

It depends on how your system is getting jammed as stated.

We had someone crosspatching and jamming in the twin cities some years ago.

Many agencies switched from PL to DPL and other things which helped for awhile.

It was not until it was found that there was a leak in the dept which caused the freq info to get out.

If it is s simple then you might luck out, however if it is someone just throwing out random noise with no PL then it can cause some issues that way also and changing freqs is not easy or really able to be done.

Good luck and hope you find your answer.

[alex]

If you have a voting reciever network - you might start there. There's software out there that can monitor a system and will highlight wich voted site is recieving a signal. You could then narrow it down that way.

I know that my county has a program which can do that - it's kinda neat to see a fire truck drive down the street and hop sites. I've only seen it once, but I was told that the tech's have dialin ability to monitor the system.

You coudl then use that to triangulate an area, then set up different times or look for patterns to figure out when would be a good time to have people around to hunt in that area.

Worth a try.

[willbartlett]

4 Basic Methods:
Brute force - use more power then jammer
Change Frequencies (hopping)
Spread Spectrum
Find & eliminate source.

Without more detail, it's hard to figure out a solution. BTW, the ham radio community may be a resource in finding the jammer. Consider it a fox hunt where you get to jail the fox.

Martin

You forgot adaptive nulling. With 2 fixed sources, it wouldn't be impossible to impliment, but it's still not easy. Brute force and using gear with LPI (hopping) are the 2 most viable options.

Really, echoing the above, lots of hams have pretty decent DF gear. Just be sure to weed out the hamsexy ones.

Will

[Station House Products]

Another consideration is whether it is a dead key, inter. key, talking or just white noise. Just because you are getting channel interference does not automaticly mean it is intentional. We recently had a company come to us and ask us to track down ansource of interference that has been intermitant for the last year or so, but that would go on all day when it did occour (Approx. twice a week.)

To make a long story short, it was a GPS transponder system being used by surveyors 3 - 4 air miles away generating the signal, and they were'nt even aware of it. We've had other situations where it was a new piece of equipment installed in a building that would interfere with a system, an alarm or security system, computers (NOTORIOUS!), etc.

The point is, before you make an assumption that this is malicious (Unless it is obvious) check the basics such as new equipment installs and things of that nature. You may find your problem closer to home.

[Jim202]

You need to be a little creative in trying to localize the source of your problem. You have not been very infomative if this was on a repaeter or a simplex frequency. You haven't exactly told us how long of a time the problem stay on for.

I would try taking a portable on the frequecny in question and do some looking around for signal strength. Maybe using a directional antenna to make the searching faster.

There are other things that can cause a problem than someone with a transmitter. I once had a person with a scanner that was radiating a signal strong enough to lock put a repeater. I happened to notice it showing up when a police frequecny was active. It was effecting a local government VHF repeater. Tracked it doewn to a house and knocked on the door with a police officer. Asked if they had a scanner. Answer was yes. Then asked if they would do a test for us and unplug it. They did and the problem went away. Asked if they would refrain from using it and take it back to where it was purchased for a replacement.

Fish tank heaters can cause a problem. Have seen them radiate for about half a mile in several cases. Don't forget that some of the older didgital auto clocks caused a problem. This becomes a moving target. Best to locate in the night when they don't move.

Last but don't forget that the mobile radios in a system can go bad. Have seen several over the years cause a problem on a frequency they are not working on.

Then there also is the GE Mastr II base station. If the PA output SWR filter is tuned wrong, they will become a comb generator. This will cause a problem over a huge area. Best to find this kind of a problem with a spectrum analyzer. Have seen some techs tume this filetr for max PA output. The corrct way is to tune it with a volt meter for minimum reflected power per the manual. There is a test point on the filter board.

Hope this gives you some thoughts.

Jim

[nypdcar1]

what about using DES secure

What me and my buddies do..... thay live very close to me and we all have 110 watts des spectras with roof AT. we just go to the channel that the jammer is on and just talk in DES mode and the jammer will get tired and leave thats all to it

[ExKa|iBuR]

We tracked a guy down here a while ago who was messing around on a local ham repeater (as well as on the police repeater and such)...basically we listened and found a pattern...in the AM, he was really weak to the west and strong to the east, and in the PM it was different. His signal always had alternator whine, so we knew he was mobile...anyway, we just set up a few guys in different parts towards the east, and sure enough, right on que, this jackass started messing around. Although we never caught him, we passed along our info to the police, and about a week later, he was never heard from again.

-M

[wa2zdy]

Another home gadget that used to account for a lot of RFI trouble was attic mounted TV amplifiers. Those things are not as common now in the day of cable, but that also means more of them are running forgotten for years and sooner or later will become problem makers.

They often would go into oscillation, causing all kinds of trouble with neighbourhood TV and FM receivers. Nothing saying they can't spew crap in the land mobile bands either.

The one thing about them is they wouldn't have a PL and thus could be jamming away with nobody knowing right away.

Something to consider in the case of a "jammer" without the correct PL tone.

[CTAMontrose]

Fox hunting isnt an option. This would have to be done in a matter of minutes vice days.

Get the CCARS boys to go find your interference!

[radiokid]

In Eastern Nebraska and Western Iowa, there have been some Wineguard , I think I spelled it right, TV Amplified Antennas that will put out a UHF Signal in the Ham Band. One signal was strong enough to get into the repeater from 20 miles I believe. They were on campers or RV's that only get out during summer, and get parked in winter. Good Day, Radio Kid

[ExKa|iBuR]

I'm not sure about those Winegard antennas, but a source of a LOT of noise are those old "Shotgun" TV antennas...they look like an overgrown baseball bat. I had one, but ditched it, because whenever it was pointed in the direction of my ham antennas, the noise floor would be insane.

-M

[wb0qqk]

In Eastern Nebraska and Western Iowa, there have been some Wineguard , I think I spelled it right, TV Amplified Antennas that will put out a UHF Signal in the Ham Band. One signal was strong enough to get into the repeater from 20 miles I believe. They were on campers or RV's that only get out during summer, and get parked in winter. Good Day, Radio Kid

Absolutely true. A defective Winegard amplifier was discovered to be
the cause of interference to an 800 mHz. trunking system operated
by an electric utility company last year here in Omaha. It was on the
roof of a residence and was located five miles from the main tower
site. These amps have a tendency to radiate anywhere from 100 to
900 mHz. and sound like a television sync signal.


From the Winegard website:

Dear Winegard Customer,
Winegard Company has received reports that some of our Sensar II television reception antennas may be emitting spurious signals. While these inquiries have been relatively few when compared to the number of Sensar II antennas in use today, Winegard Company takes this matter very seriously. Please note that this problem will not be apparent to you the consumer, as it typically does not affect the performance of the antenna. However, if this problem exists with your antenna it may cause interference to the two-way radio signals of other parties.

As part of our normal program of long-term quality assurance, Winegard has been surveying various RV campgrounds, dealers, and rallies throughout the United States. When a problem is identified with a Winegard Sensar II antenna, it is replaced with a new antenna free of charge and a renewed two-year warranty.

Winegard continues to search actively for and replace potentially affected antennas. Winegard is a responsible company and takes this matter very seriously. Customer satisfaction is extremely important to us.

If you have questions regarding this matter please call us at (800) 856-4350.

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