(US) Legality of Radar Experimentation in Amateur Bands

[0culus]

I've been looking into this recently, and it appears to be a lot of gray areas with no black and white answers. 

The only thing that seems to be definitive is that pulse modulation is not allowed in the amateur part of X band (10-10.5 GHz), in the US. Other than that I have found plenty of arguments about whether radar falls under the beacon umbrella or whether it falls under the telemetry umbrella. These both make sense to me, but it's just people talking on the internet (yes, I see the irony here).

Does anyone know of any specific rules that apply to a ham experimenting with radar? My current experiments fall into the ISM bands at a legal power level for those bands, but eventually I'd like to expand my horizon to more power and different frequencies that are available to me as a licensed ham, if possible.

[0culus]

Surely someone has an opinion on this...   

[radar_macgyver]

FMCW? The TX power levels needed for pulsed radar to be usefully sensitive will exceed ham limits anyway.

[0culus]

LOL, awesome username. 

Well, yeah, that kind of goes without saying that we won't (legally) be building a pulse radar that matches "real" systems. But you can still experiment at lower power, at much shorter ranges, which is all I'm interested in in. I'm not looking to burn up the sky with high power RF here.

[coppercone2]

look at the development of radar gun chronometers (whatever the thing that measures bullet velocity is) since the 90's to see legal issues with radar @ home/small business

[bob91343]

It would seem to me that if one stays within legal power limits and only uses legal transmit modes, it should be legal.  And of course not causing interference.

Soon they will make laser flashlights to antagonize cats, illegal.

[tautech]

Maybe a little research about frequencies and power used in marine radars can guide you.
Considering they are plastered all over private pleasure boats I'd doubt they are overly controlled by legislators.

[tggzzz]

Well, yeah, that kind of goes without saying that we won't (legally) be building a pulse radar that matches "real" systems. But you can still experiment at lower power, at much shorter ranges, which is all I'm interested in in. I'm not looking to burn up the sky with high power RF here.

25 years ago people were interested in using the 60GHz oxygen hole for short distance radar, but the RF devices were research items.

Now at least one company is producing complete subsystems, typically for automotive radars.

[0culus]

Maybe a little research about frequencies and power used in marine radars can guide you.
Considering they are plastered all over private pleasure boats I'd doubt they are overly controlled by legislators.

Unfortunately, at least in the US, marine radars are not legal to use on land. 

[tautech]

Maybe a little research about frequencies and power used in marine radars can guide you.
Considering they are plastered all over private pleasure boats I'd doubt they are overly controlled by legislators.

Unfortunately, at least in the US, marine radars are not legal to use on land. 

OK, how might one do service on them then ?   

[Lord of nothing]

  try to get a licence for a Aircraft Radar and or a Weather I guess the are good enough.

[LaserSteve]

Try to get a radar license in the US, unless you own a boat or plane, it is generally frowned upon by FCC.   I know, I once had a pretty good corporate reason to need a short range (5-10 nm) low resolution  air search radar. For lasers in airspace.  Boy did I get an angry email from FCC and an immediate response from another agency on my airspace use, which was NOTAMed to begin with..  I could not even find the clause in the rules that allows a TV station to own a weather radar, or how their frequencies get coordinated, but that was 10-12 years ago. 

What you can request, and the fee is low, is an experimental temporary allocation, in the form of an experimental license.  Emit what you want within reason..

BTW, please stay clear of 10.368 Ghz , lots of folks are using that for rain/snow  bounce SSB QSLs during the daytime and evening.   Not uncommon to get good scatter coverage across 2-3 state lines.
Way it works is using extremely narrow bandwidth, as well as very highly stabilized master oscillators, with high gain antennas.   

Some folks do use the same methodology for aircraft scatter communications on the coasts. They do not actively track or range  aircraft, just use them as a 737 sized reflector, and not surprisingly the angle of incidence in both azimuth and elevation is critical, seems most airliners have a very tightly shaped reflection curve.    Sadly with not much more then cargo flying today, such QSLs are rare.

I now know that TV Station / corporate radar is ULS  code RS, and is a "Land Mobile Radiolocation" license.

Keep in mind that pulsed emission is a no-no in some (if not all) of the microwave bands in the US, where we have secondary status.

I'm also well aware of the very rapid fine that occurred when some one used a marine radar on the "control tower" of a privately owned field.
That got shut down very quickly, and probably for good reason.

When you have solved the Friis Equation and the Modified Radar Equation and have an idea of what you want to do, please let us microwave hams know so we can help you deconflict your spectrum use.  I'm sure if I even mentioned this to the usual distribution list you would get a "NO" right off that bat. 

Steve

[babysitter]

It would be helpful if you describe your problem in a way that you can use the ITU radio regulations definition of ham radio for the answer.

So, are you using it as a radio amateur researching reflections and propagation, so more or less a single "ping" to proof your concept, experimentation in best compliance with the radio regulations?
I consider it okay to use a proper transmission (either self-generated or from third parties) and see if you can get useable results. Just look for e.g. doppler shifted signals from beacons for example, receive your own rainscatter etc. - lots of playground.

Or do you intend to run a permanent/temporary surveillance? Hard to press it into compliance with the radio regulations.

73

[radar_macgyver]

I'm also well aware of the very rapid fine that occurred when some one used a marine radar on the "control tower" of a privately owned field.
That got shut down very quickly, and probably for good reason.

Haha, that's quite the story!

The process for obtaining temporary licenses is not easy either, but then again the few times I've had to do that, I went through the regional frequency coordinator agency (in my case, NCAR, Boulder); the process took about a year. Dealing directly with the FCC (or worse, NTIA) is immensely harder. Pulsed radar, even in allocated bands, is subject to rather strict rules (see section 5.5 of the "Red Book") regarding harmonics and spurious content. When you're generating 87 dBm output power, it doesn't take much to stomp all over someone else's spectrum.

I believe TV stations/commercial entities go through the FCC, though there are very few TV stations these days that actually deploy their own radars (most syndicate Accuweather and the like).

FMCW is a lot more sensitive for a given TX power level, and since the waveforms don't occupy as much bandwidth as a pulsed waveform, it's a lot harder to interfere with your neighbors. When you do, though, the interference is much harder to suppress. If you have an 88D, TDWR, ASR or ARSR in ~20 miles of your location, please don't try even FMCW stuff outdoors. Unless you're working at 35 GHz or something

[0culus]

Ok ok, to clear up what seems to be a common misconception here: this is about experimentation in the amateur bands (as the title conveniently makes clear  ), which I am properly licensed for in the United States. This is not about setting up something permanent or burning up the sky with stupid EIRP.

I'm trying to figure out the finer points of the regs here, or rather the unspoken subtext, because the US amateur regs don't really speak to radar, other than banning pulse on 3cm.

[LaserSteve]

I can tell you that generally FCC wants to see the ability to have a conversation with another ham. Most other hams would tell you that if you found a clear frequency that is not a calling or weak signal channel, and paused periodically to listen, you might just be alright. Provided your not in some dense area like California where spectrum management is a pain.  What you will conflict with if your not careful is the rule about using the minimum power for a QSO.  The other rule is do not interfere with existing systems or repeaters.  There is no firm rule, but bands like 1296 do have other users, ie FAA long range search radars.  Three point five, which we just lost in an FCC vote, is Navy Surface Search Radar..    WISPs just got in a lot of trouble for interfering with WSR-88, and I mean a LOT of trouble.  440 is shared with space tracking radars of considerable importance.

So how long are you going to emit on a given day, what is your target,  and how close are you to the coasts?   Are you below the horizon of any Air Search Radars in your area?  What kind of peak power are we talking here?  Are you clear of the the government and commercial users in the band?
Will you transmit your ID in a way an offended user can find you?

   Have you looked at the FCC special rules for given areas, Ie no  repeaters near the three Pave Paws (they have a new name now) space search radars, or in my case, because I am north of line "A", I can't use 420 to 430 because it is commercial and government  land mobile in Canada.

BTW, It is difficult to find who is using what if they are Federal users. 

Generally unless your transmitting a beacon or RC , most hams are going to say no to blind one sided QSOs with no intent to answer.   I can guess what your regional, voluntary, frequency coordinator is going to say, which is NO.

Do you have a spectrum analyzer for the band you wish to use?   


This gets complex quickly.   Its one thing to rig a fixed directional antenna and do some pinging.  Its another to set a scanning antenna.

I think the rule that will get you is the bandwidth limitations. The shorter the pulse you radiate, the more your spectral width increases.   

Also keep in mind that if there is one group of RF users with the ability to rapidly hunt you down, it is your fellow Hams.  FCC has many, many, automated remote monitoring stations that they don't talk about. Last I checked there were around 30 regional automated systems that were publicly mentioned. 

Look, here is an example of a home made radar, if not the pinnacle of a simple home made radar..  He needs 150 Mhz of bandwidth to accomplish his goal of making a decent radar altimeter using FMCW at 400 mS per sweep.  He's actually using the designated aircraft band for this, and considering whom he is in his home country, probably knew whom to call to get permission.  He heads a RF research institute as a day job. 

http://s53mv.s56g.net/vnr/theory.htm

Looking at his numbers, and being locked out of X-band, I think you'll run out of bandwidth within the terms of your license if you want to go beyond backyard distances.


Steve

[0culus]

I can tell you that generally FCC wants to see the ability to have a conversation with another ham. Most other hams would tell you that if you found a clear frequency that is not a calling or weak signal channel, and paused periodically to listen, you might just be alright. Provided your not in some dense area like California where spectrum management is a pain. 

Generally, yes, but beacons and telemetry signals are exceptions as far as I can tell. Plus, radar isn't technically one sided...you are trying to receive your own echoes (or even echoes from someone else...) Then you can go down the rabbit hole about it technically being a propagation beacon I suppose. At the very short ranges and low power I care about, however, this really isn't an issue IMO.

What you will conflict with if your not careful is the rule about using the minimum power for a QSO.  The other rule is do not interfere with existing systems or repeaters.  There is no firm rule, but bands like 1296 do have other users, ie FAA long range search radars.  Three point five, which we just lost in an FCC vote, is Navy Surface Search Radar..    WISPs just got in a lot of trouble for interfering with WSR-88, and I mean a LOT of trouble.  440 is shared with space tracking radars of considerable importance.

As far as I can tell, the rule about minimum power is regularly ignored. I also have been getting into AMSAT work with a 5W HT and I regularly cannot get into FM voice satellites vs. people who are obviously blazing way too much power on uplink, full quieting and capturing the repeater. Really frustrating.

So how long are you going to emit on a given day, what is your target,  and how close are you to the coasts?   Are you below the horizon of any Air Search Radars in your area?  What kind of peak power are we talking here?  Are you clear of the the government and commercial users in the band?
Will you transmit your ID in a way an offended user can find you?

Emissions for only short periods, not scanned, at reasonable backyard distances, and no more than few milliwatts on 10 GHz+ is my plan. Of course I will transmit an ID...like duh?

   Have you looked at the FCC special rules for given areas, Ie no  repeaters near the three Pave Paws (they have a new name now) space search radars, or in my case, because I am north of line "A", I can't use 420 to 430 because it is commercial and government  land mobile in Canada.

I am nowhere near any of those. The only relatively close thing is a now-defunct receive station for the deactivated AN/FPS-133 radar system. In any case, I'm planning to be way above the bands used by space radar.

BTW, It is difficult to find who is using what if they are Federal users. 

No shit...I would NEVER have guessed... 

Generally unless your transmitting a beacon or RC , most hams are going to say no to blind one sided QSOs with no intent to answer.   I can guess what your regional, voluntary, frequency coordinator is going to say, which is NO.

Again, beacons and TM.

Do you have a spectrum analyzer for the band you wish to use?   

Yes.

This gets complex quickly.   Its one thing to rig a fixed directional antenna and do some pinging.  Its another to set a scanning antenna.

I think the rule that will get you is the bandwidth limitations. The shorter the pulse you radiate, the more your spectral width increases.   

Of course, this is why FMCW is better for this purpose.

Also keep in mind that if there is one group of RF users with the ability to rapidly hunt you down, it is your fellow Hams.  FCC has many, many, automated remote monitoring stations that they don't talk about. Last I checked there were around 30 regional automated systems that were publicly mentioned. 

Of course. Foxhunting is fun 

Look, here is an example of a home made radar, if not the pinnacle of a simple home made radar..  He needs 150 Mhz of bandwidth to accomplish his goal of making a decent radar altimeter using FMCW at 400 mS per sweep.  He's actually using the designated aircraft band for this, and considering whom he is in his home country, probably knew whom to call to get permission.  He heads a RF research institute as a day job. 

http://s53mv.s56g.net/vnr/theory.htm

Looking at his numbers, and being locked out of X-band, I think you'll run out of bandwidth within the terms of your license if you want to go beyond backyard distances.


Steve

404 on that link.

[LaserSteve]

try:

http://s53mv.s56g.net/

"Analog vertical navigation radar"

If your talking 10 dBm , maybe even 14 dBm, or some other arbitrary low number,   K band or higher,
and keeping your neighbor's exposure well below the 10 mW/Cm^2 limit, stop scanning once in a while, and ID as a frequency stable narrowband AM, I don't think anyone will notice, till you reach powers that annoy SATCOM / Microwave Backhaul  folks.
Especially if you stay in band, and mimic/mmic  a beacon... Pun intended.   Keep an eye on the Dish F/D ratio so your downstream field stays well spread, I know that is contradictory to what you want to do, but just your luck there is a commercial service out there somewhere...

A quick check showed Ka band spread spectrum speed radars at 15 mW input to the horn...

As for Legality, lawyers and auctioneers run the FCC now, to a large extent, and getting an opinion from their engineers is difficult. The rules are poorly defined, and if you don't blog about your results, you might be better off... This is one case where keeping your bandwidth up and using coherent detection helps you.  I sure as heck would not sell kits... Nor post videos of returns off anything not bolted to the ground, and no un-attended operation.   

Way before WIFI was common, I might have been looking long and hard as a college student at what a Magnetron would do for me, after seeing a paper published on a hard tube modulated, microwave  magnetron based  video transmitter designed by a fellow ham.  I too, puzzled over the rules.
I came to the conclusion that I could get away with it for a very short period of time.  Over time I also found publications by Japanese amateurs who injection locked magnetrons with circulators and Gunn diodes. The JA folks had very good results narrow banding the tube by regulating the anode voltage and using injection. The fact that they were graduate students might have let them get away with it, again, just long enough to demo it. But what I could do in the 1990s with no fear, is contrary to what I can do today with raw power.

PS, Long ago, my Ramsey "Cantenna" radar kit may have been a little hotter then the Ramsey engineers designed it to be.  Was quite a disappointment without some tuning and changes in bias current.  Was a cool Christmas present from Dad.

There is also an article in 73 some place about 10 Ghz nearly CW weather Radar using a Gunn diode. He claims to have good cloud returns.

I'm sympathetic, but it is very easy these days to cause interference to a service.

Good luck... 

Steve




 

[cncjerry]

I dont think one-way transmissions are legal in the amateur bands no matter what Glen Baxter says.  So I think radar would be not an acceptable use.

One-Way Transmissions
Q: What types of one-way communications are amateur stations authorized to transmit?
Section 97.111(b) provides for one-way communications. In summary, auxiliary, beacon, space and stations in distress are specifically authorized to make certain one-way transmissions. Additionally, an amateur station may transmit the following types of one-way communications:

Brief transmissions necessary to make adjustments to the station;
Brief transmissions necessary for establishing two-way communications with other stations;
Telecommand;
Transmissions necessary to providing emergency communications;
Transmissions necessary to assisting persons learning, or improving proficiency in, the international Morse code;
Transmissions necessary to disseminate an information bulletin; and
Telemetry.

[Sal Ammoniac]

Hams have made two-way contacts by bouncing their signals off aircraft. You might want to look into this. It's not traditional radar, but similar.

[coppercone2]

Hams have made two-way contacts by bouncing their signals off aircraft. You might want to look into this. It's not traditional radar, but similar.

I do not think a pilot will appreciate being aimed at with anything! I can see the FBI coming if you make some kind of motorized device that tracks planes, I think most people would think its some part of a SAM system lol. I guess FPV is becoming more common, but if someone notices you got some tripod tracking a air liner I do not expect good results.. at least the FPV system is usually obvious.

[tggzzz]

Hams have made two-way contacts by bouncing their signals off aircraft. You might want to look into this. It's not traditional radar, but similar.

I do not think a pilot will appreciate being aimed at with anything! I can see the FBI coming if you make some kind of motorized device that tracks planes, I think most people would think its some part of a SAM system lol. I guess FPV is becoming more common, but if someone notices you got some tripod tracking a air liner I do not expect good results.. at least the FPV system is usually obvious.

Is there any indication that such tracking is being used?

It would be worth doing a path analysis to see what power would actually impinge on the airframe. I would expect it to be trivial, far less that would be received from an airport's primary radar, and well within all EMI/EMC limits.

Highly collimated lasers and pilot's eyes are a different issue, of course.

The "non-traditional radar" probably refers to bistatic radar.

[0culus]

Aircraft scatter is a thing. Lots of ham website around discussing the finer points:  http://www.vk3hz.net/ is one example.

[radar_macgyver]

It would be worth doing a path analysis to see what power would actually impinge on the airframe. I would expect it to be trivial, far less that would be received from an airport's primary radar, and well within all EMI/EMC limits.

Older ATC PSRs have Klystrons with ~1 MW output power, 0.1% duty cycle, and a 34 dBi antenna. Newer ones have ~25 kW SSPAs, 10% duty cycle, so effectively the same average power. The ARSRs have a higher average power (3.5 kW) and similar antenna gain.

[tggzzz]

It would be worth doing a path analysis to see what power would actually impinge on the airframe. I would expect it to be trivial, far less that would be received from an airport's primary radar, and well within all EMI/EMC limits.

Older ATC PSRs have Klystrons with ~1 MW output power, 0.1% duty cycle, and a 34 dBi antenna. Newer ones have ~25 kW SSPAs, 10% duty cycle, so effectively the same average power. The ARSRs have a higher average power (3.5 kW) and similar antenna gain.

That "older" PSR matches my too-old recollection.

I would be amazed if the (previously) military technology for reducing the peak power hadn't found its way into civilian radars.

I would be surprised if hams could put that much energy into the æther, especially when safety is concerned.