RF module hunting - Page 1
Forum section: electronics / rf-microwave

author: aaronhance
author_rank: Regular Contributor
timestamp: February 11, 2016, 12:47:01 pm
content: I've been spending hours looking at RF modules, but I can't seem to find anything that will suit my needs! I was wondering if anyone knows of any that will. I'm looking for something with 500kbps(preferably 1mbps) data rate with 5mile line of sight range.This is the closest I've found to what I need:http://www.digi.com/products/xbee-rf-solutions/modules/xtend-module#specificationsThe data rate would limit me to sending 1fps low quality encoded footage.

author: Muxr
author_rank: Super Contributor
timestamp: February 11, 2016, 01:02:11 pm
content: Never used it, but this advertises to be what you're looking for:https://www.cooking-hacks.com/documentation/tutorials/extreme-range-lora-sx1272-module-shield-arduino-raspberry-pi-intel-galileo/

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 11, 2016, 01:44:31 pm
content: Quote from: Muxr on February 11, 2016, 01:02:11 pmI doubt it:The low data-rate (down to few bytes per second)...

author: aaronhance
author_rank: Regular Contributor
timestamp: February 11, 2016, 02:19:23 pm
content: Could I use an amplifier to boost the signal strength from a module?

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: February 11, 2016, 02:45:01 pm
content: Quote from: aaronhance on February 11, 2016, 02:19:23 pmAnd what are you going to amplify to , what is the RF transmit rules in your location ??

author: tggzzz
author_rank: Super Contributor
timestamp: February 11, 2016, 02:49:58 pm
content: Quote from: aaronhance on February 11, 2016, 02:19:23 pmOnly if you are prepared to risk interfering with other radio users (especially those indifferentparts of the spectrum), to have a visit from The Authorities, and subsequentcriminalproceedings.If you have to ask why that might be the case, you should go and visit your local ham radio society.Hint: in general radio transmissions requireindividualsto have licences which are granted after they have passed exams. There are exceptions for certain classes of well-tested equipment, but a transmitter such as you are proposing woulddefinitelynot qualify for an exemption:it would be illegalfor very good reasons. BTW, it is prefectly legal to sell equipment that it is illegal to operate.

author: han
author_rank: Frequent Contributor
timestamp: February 11, 2016, 03:20:49 pm
content: You could use long range WIFI repeater, so no HAM license needed, and its already working..examplehttps://www.ubnt.com/products/

author: aaronhance
author_rank: Regular Contributor
timestamp: February 11, 2016, 03:30:15 pm
content: Quote from: han on February 11, 2016, 03:20:49 pmI should have mentioned this is for a UAV, so it needs to be lightweight. Could I have an amazing ground receiver to improve the range?

author: bookaboo
author_rank: Frequent Contributor
timestamp: February 11, 2016, 05:25:36 pm
content: You can do whatever you like on the receiver antenna (as long as you don't transmit on the same antenna).Might be an idea to send your requirement to LPRS and Radiometrix, both are very helpful technically and as long as you stick to recommended transmitter antennas you won't break any laws or annoy anyone else.

author: tggzzz
author_rank: Super Contributor
timestamp: February 11, 2016, 11:18:49 pm
content: Quote from: aaronhance on February 11, 2016, 03:30:15 pmThat wouldn't break any man-made laws, so you only have physics to limit you.

author: uncle_bob
author_rank: Unknown
timestamp: February 12, 2016, 12:23:43 am
content: Quote from: aaronhance on February 11, 2016, 03:30:15 pmHiOk, so now you have the opportunity to criminally interfere with communications over a large geographic are. Plus you have broken a number of aircraft specific (type acceptance) rules as well. The large area is pretty much guaranteed to attract the sort of attention you do not want .....Is this really worth going to jail for a few years?Why is this so? The RF spectrum is packed with users. There are an enormous number of people who would love to use the spectrum, waiting in the wings. The only way to prevent chaos is regulation. Since not everybody likes rules, there is also active enforcement. Some chunks of the spectrum are used by the military. Think in terms of *very* active enforcement if you hit the wrong channel.Yes, if you are off in a country nobody can find on a map, you can get away with this or that. If your country information is correct, you are in a country that *does* have rules and enforcement.Bob

author: hendorog
author_rank: Super Contributor
timestamp: February 12, 2016, 09:20:28 am
content: Quote from: aaronhance on February 11, 2016, 12:47:01 pmDo you need digital? The norm for FPV is analog which means its cheap and easy.If you need digital then wifi should work. It's used in that low cost Parrot drone.2.4GHz is pretty much the standard for RC model control. So you ain't going to jail for using that frequency as there are not enough jails to hold us allBy all means check the regs and don't be reckless.

author: tggzzz
author_rank: Super Contributor
timestamp: February 12, 2016, 09:30:17 am
content: Quote from: uncle_bob on February 12, 2016, 12:23:43 amBeing in the same country, I can confirm that.When I applied for a licence to transmit on a very low power within a building, the local detection/emforcement people came aroundbeforegranting the licence. We had a great time together, I applied a suggestion they made, and I got the licence.

author: tggzzz
author_rank: Super Contributor
timestamp: February 12, 2016, 09:41:24 am
content: Quote from: hendorog on February 12, 2016, 09:20:28 amYou are correct - providing that is theonlyfrequency used, plus provided it is within the legal power limits. If either of those is not the case then expect "A Visitor" to appear unexpectedly.Startingquestion: if you are using modulation type M on a carrier frequency F with power P through a component with an IP3 of XdBm and saturation at YdBm, what powers at what frequencies would youexpectto see being emitted at the antenna. If you think the frequencies will be limited to F+-deltaF, then "bzzzt, go to jail, do not pass go".I doubt the OP has sufficient knowledge to understand and/ormeasurelet aloneconstrainthe transmitted frequencies.The OP would be well advised to talk to their local radio hams.

author: hendorog
author_rank: Super Contributor
timestamp: February 12, 2016, 10:13:53 am
content: Quote from: tggzzz on February 12, 2016, 09:41:24 amHams generally know very little about FPV in my experience. It might be different in the UK, but that is certainly the case here. Asking RC clubs might be an option, although they can also be very traditional. No harm in asking but brace yourself for a lectureYeah I get your point. But if anyone turns up to question you, then you must have done something grossly wrong which is affecting another user. That would be reckless, so the point is don't do thatFor the OP, it appears the UK regs are here for RC vehicles, and they are limiting.http://stakeholders.ofcom.org.uk/spectrum/information/licence-exempt-radio-use/licence-exempt-devices/ofw311100mW eirp at 2.4GHz isn't much, but if you build or buy good antennas it should go a fair old way. 25mW on 5.8 GHz is even less, but that can still go several km's if you know your stuff - according to this old thread.http://fpvlab.com/forums/showthread.php?2261-5-8-GHz-ranges

author: tggzzz
author_rank: Super Contributor
timestamp: February 12, 2016, 10:55:41 am
content: Quote from: hendorog on February 12, 2016, 10:13:53 amThey know about radio transmissions, which is the issue here.QuoteThey came and talked to mebeforeI started transmitting.

author: Ian.M
author_rank: Super Contributor
timestamp: February 12, 2016, 11:41:45 am
content: See:https://www.caa.co.uk/Commercial-industry/Aircraft/Unmanned-aircraft/Small-unmanned-aircraft/which indicates the main regulatory restrictions that hobby FPV drones fly under in the UK.QuoteThat's within the range that a good licence free (IR2030/27/2) omnidirectional 2.4GHz 10mW UAV video sender, with a high gain directional antenna on the receiver is good for. Either operate as a two man team, one piloting and the other manually tracking the UAV with the receiving antennae (and possibly standing by with a buddybox as the required backup VFR pilot), or design a GPS tracker that calculates the relative bearing and elevation of the UAV from the base station and controls the antenna accordingly. You can modulate telemetry data e.g. UAV GPS position onto the video sender's audio link (if implemented) or onto a scanline at the top or bottom of the frame to enable this. To avoid the problems of high slew rate tracking close in, a second omnidirectional receiving antenna would be advisable, with auto-switching based ideally on RSSI, but if the modules used don't support that, on how clean the sync pulses (and audio channel if implemented) are.

author: GandalfDerGraue
author_rank: Contributor
timestamp: February 12, 2016, 01:03:56 pm
content: ...Quote from: han on February 11, 2016, 03:20:49 pm... and even this is illegal in some countries. Always be sure to check if there is a regulatory for the frequency range you're planning to use, if not or if in doubt better don't use. It has to be positively *allowed* to be used for more or less public usage, all other cases and frequencies are definitely prohibited.

author: tggzzz
author_rank: Super Contributor
timestamp: February 12, 2016, 03:51:10 pm
content: Quote from: han on February 11, 2016, 03:20:49 pmNot true. WiFi transmitters are legally limited by EIRP, not power.

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 12, 2016, 04:06:12 pm
content: Quote from: tggzzz on February 12, 2016, 03:51:10 pmSure, but good luck putting an antenna with some gain on a UAV.

author: janoc
author_rank: Super Contributor
timestamp: February 12, 2016, 04:43:44 pm
content: I think this debate about frequencies and power and licensing is pretty much a moot point. If the goal is to operate an UAV at (up to) 5 mile range then that certainly breaks the rules about flyingwithin visual range.Even a spotter buddy next to the pilot won't see squat at such distance unless the OP is intending to fly an UAV the size of a commercial jet. (And how many FPV flyersactually usespotters??)My advice would be - just don't and find something better to do. This is asking for serious problems, especially with all that "anti-drone" law enforcement attention today thanks to the reckless idiots flying UAVs close to airports, in the way of large manned traffic, over cities, etc.

author: LaserSteve
author_rank: Super Contributor
timestamp: February 12, 2016, 05:33:15 pm
content: Keep in mind that nearly all WIFI or " License Free" ISM frequencies of 420 Mhz and up are allocated on a PRIMARY basis to RADAR, both Military and Civilian. Wideband sources of such frequencies at any reasonable altitude start showing up when the receive antenna is a four meter wide cosecant squared radar antenna.5.6 Ghz Professional WIFI has became a real problem in some places for Doppler Weather Radar in the US. This generally happens when certain firmware settings get changed, but it is a problem. It is also very close to/overlaps a marine radar band in 90% of the world.A short duration, very low power, narrow pulse, which was the original intent of the "license free" frequencies world wide, was not going to interfere much. Especially with 2.4 Ghz which is strongly adsorbed by organics and trees leaves. However if you get said source airborne on a high gain antenna, your going to get noticed. The question is, how long will you be ignored if your close in to the Radar.1.2 Ghz in the United States is very, very, close in frequencies to the long range radars which protect our borders.. Granted they probably have a anti-jam "waveform" they can use, but if they have to switch to that mode, your going to get a visit.There are also some severe localized restrictions on where you can use 420-450 Mhz in the US and UK...Another big Sin would to be to fly in a "National Radio Quiet Zone" which exist in various places around the world. We have a huge one in the US.It's monitored for emissions, trust me. Even cellular and FM and AM radio is banned there with a few exceptions.So when the white or black SUV pulls up, which can happen, what are you going to say? Said vans usually have a slightly extended addition to the roof. These days they hunt you with TDOA or TOF systems, so the hunting antenna is very small and discrete.Steve

author: aaronhance
author_rank: Regular Contributor
timestamp: February 12, 2016, 05:42:00 pm
content: Thanks for the input guys! After reading lots, I'm going to be using 2.4Ghz 100mw transceiver(for video), I will also be looking into building an auto-tracking antenna.EDIT: Would I be able to use an amp from the receiver antenna?

author: Ian.M
author_rank: Super Contributor
timestamp: February 12, 2016, 05:56:40 pm
content: You may want to take a look at this blog:http://fpvuk.blogspot.co.uk/2012/12/uk-telemetry-fpv-frequencies.htmlwhich summarises the legal systems for FPV in the UK. 100mW @2.4GHz is only legal on a UAV if it uses digital modulation.

author: aaronhance
author_rank: Regular Contributor
timestamp: February 12, 2016, 07:14:12 pm
content: Thanks Ian!How accurate would you guys say this is?

author: Ian.M
author_rank: Super Contributor
timestamp: February 12, 2016, 07:31:56 pm
content: That looks like its a form for a calculation of the theoretical line of sight range. It takes no account of attenuation due to ambient atmospheric conditions, multi-path effects and 2.4GHz band background noise. The actual range achievable may be as low as 10% of that. To get anything close to the theoretical range you'd have to be operating in a remote valley with no line of sight to any habitation, communications masts etc.

author: hendorog
author_rank: Super Contributor
timestamp: February 12, 2016, 07:56:23 pm
content: Quote from: aaronhance on February 12, 2016, 07:14:12 pmTheir miles to km conversion is the wrong way around.For a real world datapoint - 100mW at 2.4GHz is the same power and frequency as a typical RC model transmitter, I have an oddball brand (WFLY) which has worked out to 3km or so with the rubber ducky antenna it came with. Others have issues at much shorter ranges though so YMMV.Pushing that out to over 21 kms with a high gain rx antenna seems highly optimistic for the reasons Ian said.

author: uncle_bob
author_rank: Unknown
timestamp: February 12, 2016, 11:36:15 pm
content: HiOk, there is no big need for a lot of calculations at 2.4 GHz. Everybody runs WiFi in that band. The antennas and power level are roughly what you will be running. We have empirical data !!!Fire up your router/ grab your computer run a test. Can you get a mile from your router and talk to it? Nope. So much for 10% of the calculated 12 miles. Can you get a few hundred feet? Yes, you probably can. That's maybe 1% of those apparently magic numbers.There is no magic in this. I have line of sight to the router all the way to the way back yard. That's as much line of sight as your drone would have. I have no confidence of being sure to hold the connection at 500'.Same band / same crowding / same problem. No 12 mile range with a simple antenna.Bob

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 12:40:01 am
content: This was based on a high gain antenna (24dBi) with 18dBd power before the antenna. So I assume it will get better range than a pcb antenna with 20mW~ of power.

author: uncle_bob
author_rank: Unknown
timestamp: February 13, 2016, 02:04:00 am
content: Quote from: aaronhance on February 13, 2016, 12:40:01 amHiStill not something that is going to be very practical with a drone (at least without a fancy auto tracking system on the antenna).Bob

author: tggzzz
author_rank: Super Contributor
timestamp: February 13, 2016, 10:09:12 am
content: Quote from: aaronhance on February 13, 2016, 12:40:01 amI don't know what you mean by "dBd"; I've never seen that before.Apart from that, if that antenna is at the transmitter, the range will stay exactly the same. (Exception: if you transmit illegally, are prepared to stomp over other radio users, and are therefore willing to accept a criminal conviction).Do you understand the significance of the "E" in EIRP, and the difference between EIRP and IRP?

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 13, 2016, 11:34:28 am
content: Quote from: tggzzz on February 13, 2016, 10:09:12 amdBd is gain over a dipole, same use as dBi, but I think he tried to type dBm.

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 01:54:39 pm
content: I did mean dBm yes, sorry. As for auto tracking, I've already said in this post I'm doing that. I've also said that I will be using the high gain antenna for rx not tx. Thanks!

author: uncle_bob
author_rank: Unknown
timestamp: February 13, 2016, 03:16:33 pm
content: Quote from: aaronhance on February 13, 2016, 01:54:39 pmHiThere is a slight difference between dBd and dBi but they are indeed the same ideaIf you are trying to fly the drone, and steer a high gain antenna at the same time, you overload quickly. To much to watch, to few hands, not enough time. If the telemetry or video matters, any miss-steer is likely to be an issue. If you put your control stuff on the same channel, a drop out could be quite exciting. (Indeed I've seen this done several times). The choice is to either have somebody who does nothing but point the antenna *and* another who controls the drone, *or* you use an auto tracker. Gain and directivity are directly related, high gain means good pointing accuracy. Either the person or the machine need to do a pretty good job.Bob

author: tggzzz
author_rank: Super Contributor
timestamp: February 13, 2016, 03:23:32 pm
content: Quote from: uncle_bob on February 13, 2016, 03:16:33 pmJust so.The OP shouldn't forget to add in the effects of turbulence, which - especially at low altitude - can be considerable. That will help determine the necessary control loop bandwidth and hence maximum latency.Failure to do that may result in something that works only in ideal conditions.

author: tggzzz
author_rank: Super Contributor
timestamp: February 13, 2016, 03:26:08 pm
content: Quote from: aaronhance on February 13, 2016, 01:54:39 pmOK. Your phraseologyQuote from: aaronhance on February 13, 2016, 12:40:01 ammade me think otherwise.

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 03:35:22 pm
content: Ah yes, 18dBm on the transmitter

author: Ian.M
author_rank: Super Contributor
timestamp: February 13, 2016, 04:04:20 pm
content: I don't think turbulence will be a significant issue other than to the UAV's attitude control system.Although theoretically one could put a tracker and high gain directional TX antennae on the UAV, the prime spot to do so (underside center) is usually reserved for a camera mounted in pan&tilt gimbals. If its mounted topside, it wont be able to get enough down-angle unless its on a fairly long boom which will cause aerodynamic issues. Also there is the all-up 7Kg upper weight limit for licence free operation to contend with, and the extra mass of a UAV mounted tracking antennae will directly cut into payload and flight time. Although this does not absolutely rule out a tracking antennae on the UAV, it makes it extremely difficult to do so unless its a neutrally buoyant blimp, which has the sheer volume to make non-interfering gimballed camera and antennae mounts possible.Therefore, when the only tracking antennae system is for RX at the base station, all one has to consider is if turbulence can take the UAV out of the antenna's primary lobe faster than the tracker can slew the antenna. I already pointed out that close-in tracking would be limited by the antenna slew rate, so suggested an additional receiver with an omnidirectional antenna so the tracker doesn't have to follow accurately while the UAV is moving rapidly close-in.A good quality semi-portable parabolic dish antenna (i.e under 1.2m diameter) may have a 3db beamwidth of as little as 6 degrees. At 50m range, that's a little over 5m. Assuming the tracker tries to keep the UAV in the center third of the beam, it can tolerate a rapid displacement of up to 1.75m before it reaches the 3db beam edge.Basically, if the turbulence is that bad, the craft wont be controllable anyway, its just too gusty to fly.The devil now will be in the details. I suspect it will need to be man-portable and its got to be reasonably easy to set up and anchor then align relative to true north. For that bit, probably the easiest method would be to put the UAV into a position holding hover at a range of a couple of hundred meters then manually control the tracker to acquire the UAV, and use the GPS bearing to auto-align to.

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 04:19:06 pm
content: This is a fixed wing(think airplane), but the idea of having a tracking antenna on the UAV, hmm, interesting! I'm defiantly going to look into the points you made! Thanks agian Ian!

author: Ian.M
author_rank: Super Contributor
timestamp: February 13, 2016, 04:39:08 pm
content: There is absolutely nothing to be gained by a tracking TX antenna unless the transmitter is licensed, due to the EIRP limits on license-free transmitters being so small that it is easily possible to reach them with an omni-directional antennae.

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 06:08:21 pm
content: Thanks! If I get an amateur license from ofcom, can I still use higher power transmissions from ground, even if I can't on the uav itself?

author: uncle_bob
author_rank: Unknown
timestamp: February 13, 2016, 06:23:35 pm
content: Quote from: aaronhance on February 13, 2016, 06:08:21 pmHiThat is a per country sort of thing. In general the answer is no. One reason is that by running high power in the middle of the WiFi band you pretty much wipe out all the other users.Bob

author: Ian.M
author_rank: Super Contributor
timestamp: February 13, 2016, 06:24:13 pm
content: No, as its a communications licence and all transmissions must be directed to another amateur, which your UAV certainly is not.

author: PA0PBZ
author_rank: Super Contributor
timestamp: February 13, 2016, 07:51:41 pm
content: Quote from: Ian.M on February 13, 2016, 06:24:13 pmI've never seen that restriction.My understanding is that it is a license to experiment with radio waves.

author: djacobow
author_rank: Super Contributor
timestamp: February 13, 2016, 08:06:36 pm
content: Quote from: PA0PBZ on February 13, 2016, 11:34:28 amIn fact, dBi = dBd + 2.15.That's because a dipole has 2.15dB gain over an isotropic radiator.

author: uncle_bob
author_rank: Unknown
timestamp: February 13, 2016, 08:12:25 pm
content: Quote from: PA0PBZ on February 13, 2016, 07:51:41 pmHiExactly how the regulation is worded and what frequencies are impacted in which ways varies from country to country.Bob

author: janoc
author_rank: Super Contributor
timestamp: February 13, 2016, 08:12:38 pm
content: Quote from: PA0PBZ on February 13, 2016, 07:51:41 pmDepends. In Slovakia where I am from it is still illegal for HAMs to use packet radio nodes that are connected to the internet, for example - even if it is only for a HAM to HAM connection. The reasoning goes that as it is going over non-HAM network, devices on that network will control the transmitter (indirectly by sending data packets) and as they (or rather their operators) are not licensed, it is illegal, period. So even stuff like Echolink is out.Our licensing authority is seriously backwards and hyper conservative, they were among the last countries in the world to drop the requirement for Morse if you wanted to have HF privileges. And even now the basic N class license is severely restricted on HF, basically allowing you to use only the Morse parts of the bands, sans anything remotely usable for DX-ing (aka - "you didn't want to learn Morse? OK, we cannot drag our feet anymore because CEPT, so here you are. But screw you, no SSB for you, buster!").Running video over a HAM band would be likely a no-no as well, because it isn't an approved mode, as would be operating an unattended station (a drone). Unattended operation (repeaters, packet nodes, etc) requires a special permit.My guess is that it is the heritage of the communism where owning a radio transmitter (even a CB station!) required that you (and all your relatives!) were considered "reliable" by the communist party, were vetted by the secret police and it was a privilege of a few, certainly not a right like today where you pass an exam and get your ticket automatically. Unfortunately a lot of the "cadres" of that era are still sitting in the same offices.In contrast to that, in Denmark where I lived before I have got an all-band/all-mode HF license up to 100W power with no questions asked, it was enough to show my Slovak ticket. In France where I am now it is likely similar.So to correct your understanding - it is a license to operate an amateur radio service station using approved frequencies, modes and power levels, not to experiment with radio waves. Or at least it isn't the universal understanding of it. The experimentation certainly can fit into it, but the legal frameworks could be very restrictive, depending on country.And anyway, HAM license doesn't cover operation of commercial equipment in the ISM bands. I didn't check how much overlap is there between normal 2.4GHz wifi band and HAM allocation there - there it could be potentially possible, but one has to carefully check the local rules about interference and modes allowed.

author: djacobow
author_rank: Super Contributor
timestamp: February 13, 2016, 08:14:59 pm
content: Quote from: Ian.M on February 13, 2016, 06:24:13 pmI think a lot of people see that (in the US) the amateur radio license forbids _broadcasting_, and they take that to mean that all ham activity has to be amateur to amateur.That's not a correct inference. For one, the FCC defines broadcasting quite clearly:Title 47 Subpart A 97.3(a)(10): Broadcasting. Transmissions intended for reception by the general public, either direct or relayed(http://www.ecfr.gov/cgi-bin/text-idx?SID=eb4ca1e28d7c18f69299fa1ca8a33a25&mc=true&node=pt47.5.97&rgn=div5#se47.5.97_13)It is the intention that makes it broadcasting, not the activity.Furthermore, amateurs are allowed to use their radios for RC activities. That's described here:"§97.215 Telecommand of model craft.An amateur station transmitting signals to control a model craft may be operated as follows:(a) The station identification procedure is not required for transmissions directed only to the model craft, provided that a label indicating the station call sign and the station licensee's name and address is affixed to the station transmitter.(b) The control signals are not considered codes or ciphers intended to obscure the meaning of the communication.(c) The transmitter power must not exceed 1 W."(http://www.ecfr.gov/cgi-bin/text-idx?SID=eb4ca1e28d7c18f69299fa1ca8a33a25&mc=true&node=pt47.5.97&rgn=div5#se47.5.97_1215)As another poster commented, experimentation is actually part of the very purpose of the amateur radio service and is expressly ALLOWED. 91.1(b):[a list of the purposes for the amateur service...] (b) Continuation and extension of the amateur's proven ability to contribute to the advancement of the radio art.However, one thing that is expressly forbidden is encryption. That limits the amateur band from being useful for most personal communications or control of things that are "important."-- dave jWE6EE

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 09:00:50 pm
content: Coming from ofcom "Amateur radio is a unique hobby in that it allows you to develop and experiment with radio equipment;"Looks like I might need an intermediate amateur license to send data packets in the uk, I'll need to do some more research.

author: uncle_bob
author_rank: Unknown
timestamp: February 13, 2016, 09:08:02 pm
content: Quote from: aaronhance on February 13, 2016, 09:00:50 pmHiUmmm .... errrrr .... That's the 24 GHz band not the 2.4Bob (the guy who makes posting errors about once every 4 minutes ...)

author: aaronhance
author_rank: Regular Contributor
timestamp: February 13, 2016, 09:22:33 pm
content: Woops, yeah good eye.

author: uncle_bob
author_rank: Unknown
timestamp: February 13, 2016, 09:50:00 pm
content: Quote from: aaronhance on February 13, 2016, 09:22:33 pmHiDo *not* ask how long I spent comparing those numbers to the WiFi frequencies before I figured that outBob

author: hendorog
author_rank: Super Contributor
timestamp: February 14, 2016, 05:41:20 am
content: Quote from: aaronhance on February 13, 2016, 01:54:39 pmIts pretty easy to manually track a high gain antenna when the target is a long way away - the angle the antenna needs to move for a distant target which moves 1000m is much smaller than the angle for a close target moving 1000m.Point the high gain antenna in the direction you are going to fly and just fine tune it if you need to.Use diversity and a more omni antenna to handle when the UAV is close. The diversity will switch back to the high gain antenna when you are far away enough to get a better signal.Use an autopilot to ease the workload.I used to attach the antennas on my FPV goggles and just moved my head to aim it. Prior to that I used a screen with antennas mounted on a tripod.This is all standard stuff in the FPV world from a couple of years ago when the regulations around the world were less restrictive about long range FPV.

author: aaronhance
author_rank: Regular Contributor
timestamp: February 14, 2016, 02:23:50 pm
content: Hey, I'm building the autopilot system myself, software and hardware, although I will be using GPS and rf modules. I might as well build an auto tracking antenna, not that hard to get two angles from gps cords and elevation. I have a second person helping me on this project, but he's still learning the basics of programming.

author: tggzzz
author_rank: Super Contributor
timestamp: February 14, 2016, 04:20:58 pm
content: Quote from: aaronhance on February 14, 2016, 02:23:50 pmSo you may be getting visits from both OFCOMandthe CAA? I wonder which will claim jurisdiction firstThe CAA have told thepolice(in Manchester) to stop illegally playing around with drones. The police did stop, pronto.The CAA have brought prosecutions for drones violating the Air Navigation Order, and the perps have ended up in prison.

author: hendorog
author_rank: Super Contributor
timestamp: February 14, 2016, 06:57:34 pm
content: Quote from: tggzzz on February 14, 2016, 04:20:58 pmSo what rule is he breaking by building it himself rather than importing it from China like everyone else does?https://www.caa.co.uk/Commercial-industry/Aircraft/Unmanned-aircraft/Small-unmanned-aircraft/

author: hendorog
author_rank: Super Contributor
timestamp: February 14, 2016, 07:03:21 pm
content: Quote from: aaronhance on February 14, 2016, 02:23:50 pmSounds like a plan. The general guidance on diy fpv has always been to introduce one thing at a time - i.e. get the thing flying before adding the autopilot, then add telemetry/OSD, then video, then antenna tracking, etc etc.I found that easier anyway as you get to have some fun at each stage.If you haven't found it yet, fpvlabs.com is a great resource - that site was created because at the time every FPV discussion on rcgroups degenerated into an argument about the rules... Sound familiar??

author: tggzzz
author_rank: Super Contributor
timestamp: February 14, 2016, 07:08:55 pm
content: Quote from: hendorog on February 14, 2016, 06:57:34 pmSince we have no idea how it behavesand misbehavesw.r.t. the ANO, we cannot answer that. Neither, I presume, can the OP.

author: hendorog
author_rank: Super Contributor
timestamp: February 14, 2016, 07:51:42 pm
content: Quote from: tggzzz on February 14, 2016, 07:08:55 pmYep he can - because he has to satisfy this clause:"The person in charge of a small unmanned aircraft may only fly the aircraft if reasonably satisfied that the flight can safely be made."He might do that by tethering after making changes, and/or by having a 'master' RC receiver which can switch out the autopilot for example.The UK rules state no aerial work without approval, which would have put the police on the wrong side of the law. Interestingly, over here they have taken a different approach, based on the actual risk instead of the use.

author: tggzzz
author_rank: Super Contributor
timestamp: February 14, 2016, 08:45:34 pm
content: Quote from: hendorog on February 14, 2016, 07:51:42 pm1) since he hasn't built the autopilot yet, he can't answer the question.2) after he's built it he might provide a response, but whether or not that is a correct answer w.r.t. the ANO is a different kettle of fishQuoteGiven that the OP is interested in a 5 mile range, it is reasonable to question how effective (or even safe!) any tether might be - always presuming a drone could lift it in the first place.QuoteThe UK rules statefarmore than that, and it it the other more basic rules that caught out the Mcr police.Why does someone displaying an antipodean flag think they know so much about the UK ANO?

author: hendorog
author_rank: Super Contributor
timestamp: February 14, 2016, 09:38:17 pm
content: Quote from: tggzzz on February 14, 2016, 08:45:34 pm1) Correct - I should have said 'He _will_ need to be able to satisfy this clause'2) I haven't seen any rules around development of UAV's in the UK. I gather you know better so please share your knowledge.2a) Do we know the size of craft the OP is developing?QuoteDid you really think I was suggesting a 5 mile tether...?Quote1) I agree they do have other rules. I never said otherwise. It was just an observation that the new NZ rules, which have recently been updated, now work differently.2) OK, thanks for the info.QuoteI haven't stated anywhere that I do. I'm just trying to help him complete his project which is about a subject which interests me and which I have experience in.On the other hand you have told the OP he is going to go to prison before he has even started.If you know something about small UAV development then by all means provide some _useful_ guidance.

author: tggzzz
author_rank: Super Contributor
timestamp: February 14, 2016, 10:26:16 pm
content: Quote from: hendorog on February 14, 2016, 09:38:17 pmAFAIK there are no rules/laws about developing (nor buying) UAVs in the UK - but that's irrelevant. There are laws aboutflying/operatingUAVs.I am definitely not going to summarise the law because I could accidentally write something that is wrong or misinterpreted.Understanding the law will not be trivial; I would recommend joining a local RC club since they will have a better idea. Similarly join a radio ham club to learn how to avoid violating the Wireless telegraphy Act.QuoteThe only way your comment could have been relevant and helpful would be if it was a 5 mile tether. In that light, how should we interpret your comment?QuoteYour memory is defective.Less than three hours ago you wrote "...because he has to satisfy this clause: 'The person in charge of a small unmanned aircraft may only fly the aircraft if reasonably satisfied that the flight can safely be made.'" and "The UK rules state no aerial work without approval".QuoteNo, I haven't. I have pointed out that other people have been jailed, and that if he does something illegal in the future he might get a criminal record.That is useful information that could save the OP a vast amount of wasted effort.

author: hendorog
author_rank: Super Contributor
timestamp: February 14, 2016, 11:59:41 pm
content: QuoteThere were two parts to my comment:He could use a short tether (say 2 metres) to avoid fly-aways so that he could test the autopilot in flight instead of on the bench - e.g. for tuning the PID loops.For longer flight tests he could use a master RC receiver to take over from the autopilot if it went haywire.Perhaps over a period of time that information could be used to build confidence that that autopilot was working and therefore can be used safely?Disclaimer: I am not an expert in autopilot development and the UK ANO.QuoteAh I see, I was simply sharing potentially useful information which I found using Google.Those are quoted/paraphrased from this link a couple of posts earlier.https://www.caa.co.uk/Commercial-industry/Aircraft/Unmanned-aircraft/Small-unmanned-aircraft/Ultimately the OP may discover for himself that a 5 mile flight is in the too hard basket legally. That's his call to make. It would require a special effort to do in NZ as well FWIW. Either approval from CAA NZ - which essentially requires $$$ and some process of ensuring safety - or a number of spotters distributed along the flight path.

author: tggzzz
author_rank: Super Contributor
timestamp: February 15, 2016, 01:52:27 am
content: Quote from: hendorog on February 14, 2016, 11:59:41 pmNor, it would seem in threat definition, system validation, system development nor system verification.Start by considering the effects of windspeed, turbulence and windshear near obstacles (ask parascenders and hang glider pilots), the Fresnel zone and other multipath effects (simple physics), GPS non-availability (which happens; there are usually NOTAMS about it), ISM band interference (guaranteed to happen), to name a few off the top of my head.Next consider how you won't be able to test those with a few tethered flights - except to demonstrate that you haven't got necessary reliability.If you really want to get into autopilots, I would suggest starting with RC cars or boats. There's less chance of knackering other people with those.QuoteAt last you understand. There's no point him wasting 1000 hours,say, of his time only to find out a proper solution (if any is possible) would take 100,000 hours.

author: hendorog
author_rank: Super Contributor
timestamp: February 15, 2016, 02:51:45 am
content: Quote from: tggzzz on February 15, 2016, 01:52:27 amAre these things you have experience in?Quote from: tggzzz on February 15, 2016, 01:52:27 amWell shucks, a compliment.

author: tggzzz
author_rank: Super Contributor
timestamp: February 15, 2016, 09:47:05 am
content: Quote from: hendorog on February 15, 2016, 02:51:45 amYes.Allof them, bar one: I haven't used RC aircraft/boats. Some as a professional engineer, some as a leisure activity, some both.Being sufficiently humble to know what Idon'tknow, I've kept my eyes open over the years, and asked people thatdoknow about RC flying. I try to avoid being an example of the Dunning-Kruger effect, usually succeeding.What'syourexperience in these things?

author: hendorog
author_rank: Super Contributor
timestamp: February 15, 2016, 12:32:39 pm
content: Quote from: tggzzz on February 15, 2016, 09:47:05 amNone of the development items (electronics hobbyist), some exposure to the aviation items (student pilot in the past and RC), and most of the RF items (RC/FPV/HAM). I'm certainly no expert and don't profess to be one.The reason I asked that question was that it sounded like you had developed professional UAV's and were therefore approaching the problem from that direction.My experience is with hobby level equipment which is not verified/validated. Therefore my expectation is that a DIY autopilot would not require that level of rigour either.

author: tggzzz
author_rank: Super Contributor
timestamp: February 15, 2016, 03:06:20 pm
content: Quote from: hendorog on February 15, 2016, 12:32:39 pmDefinitely not, but I certainly would try to have a professional approach with anything of mine that could kill/injure/affect other people. And UAVs, whether or not they have an autopilot, certainly fall into that category.The key point is to thoroughly define how things mightfail. Amateurs starting in a field usually consider how things mightwork; thebetteramateurs go on to develop an appreciation of failure modes. The OP leads me to believe they are an amateur starting in this field and the RF field.Today's news report, merely the latest of many:http://www.bbc.co.uk/news/business-35577124QuoteThe laws make no distinctions between professional and amateur control systems, for the obvious sound reasons.