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Chuck

Ham Radio; R/C aircraft control; Video downlink

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Please excuse me if my topic is trodden ground...

However, as most on this forum, I am interested in controlling an R/C aircraft with a video down link.

Most of the commercial solutions would appear to be problematic. The new spread spectrum R/C control tx/rx setups are great w.r.t. lack of iterferance (both directions), but the higher frequencies are mostly line of sight. They also tend (from my ham experience) to loose in the winter time when every twig on every tree ends up looking like a quarter wave vertical and thus eats the power. Couple that with the fact that the spread spectrum solutions use the same frequency range (or harmonics of) the off the shelf video cameras, and you have a bit of a mess.

I was wondering if anyone has modified any of the commercial equipment to work on the ham frequencies available for R/C, and if so your success.

I was also wondering if anyone has had any luck with the Futaba FAAST systems. They "claim" to "jump around on more frequencies", this would (in theory) spread the interferance on the video over a greater space and (in theory) make it less noticable.

Comments, pointers, and even rebukes for my niavety...

Best,

Chuck

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Just stick with gear operating in the "good old" R/C bands, and you'll be fine enough.

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I was wondering if anyone has modified any of the commercial equipment to work on the ham frequencies available for R/C, and if so your success.
You didn't state your country, but if you are in the USA, then keep in mind that some of the major R/C mfgs still offer 6-meter RF modules and Rx's (but their choices are slowly drying up). For that reason, there has not been much need to discuss hacking the 72Mhz decks.

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You didn't state your country, but if you are in the USA, then keep in mind that some of the major R/C mfgs still offer 6-meter RF modules and Rx's (but their choices are slowly drying up). For that reason, there has not been much need to discuss hacking the 72Mhz decks.

PA USA.

I'll need to read the boards more carefully. I got the impression from scanning several posts that the major interference was to the video signal, and not the Digital Spread Spectrum receiver. If that's the case, then that's good. I've been involved with a number of ham repeaters over the years. Given the weight restrictions on a plane and lack of space there would not be much that could be done on same band interference. However, vertical antenna separation (of verticals) is very effective, especially given the 2.4 GHz short wavelengths. Are you aware of anyone who has tried this with the x10 cams and a DSS radio?

Best Regards,

Charles

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Are you aware of anyone who has tried this with the x10 cams and a DSS radio?

The X10 cams are under 1mW (you can thank FCC Part 15 for that), so they are not a big threat to the spread spectrum R/C Rx if you provide sufficient separation. However, modern R/C video users employ much higher power (500mW to 1W) and the interference issues (with spread spectrum R/C) has been problematic.

Sure, there have been some reported success stories (but they are few). So, there is evidence that under the right circumstances it can be done. However, it appears that most folks that try this combo soon lose confidence. Sadly, a couple of "success" stories later became bad experiences when lockups (and crashes) were reported in subsequent flights. As with all things RF, YMMV.

Even in absence of a wireless A/V installation, if you read the R/C forums about all the DSSS and FHSS R/C system problems, they are not the holy grail that everyone was expecting. My take is that the new technology has just moved the problems from here to there. The serious video R/C'ers are still on the traditional VHF R/C freqs.

I believe the 2.4Ghz systems could be improved to allow reasonable compatibility with the typical wireless A/V system. But, there is little incentive for the R/C makers to do that at this point. So, we get what they give us.

PA USA.

It would help out the forum members if you add your country to your profile's location field. Not many folks take the time to do this, but life would be much grander if they did. :)

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The X10 cams are under 1mW (you can thank FCC Part 15 for that), so they are not a big threat to the spread spectrum R/C Rx if you provide sufficient separation. However, modern R/C video users employ much higher power (500mW to 1W) and the interference issues (with spread spectrum R/C) has been problematic.

Sure, there have been some reported success stories (but they are few). So, there is evidence that under the right circumstances it can be done. However, it appears that most folks that try this combo soon lose confidence. Sadly, a couple of "success" stories later became bad experiences when lockups (and crashes) were reported in subsequent flights. As with all things RF, YMMV.

Even in absence of a wireless A/V installation, if you read the R/C forums about all the DSSS and FHSS R/C system problems, they are not the holy grail that everyone was expecting. My take is that the new technology has just moved the problems from here to there. The serious video R/C'ers are still on the traditional VHF R/C freqs.

I believe the 2.4Ghz systems could be improved to allow reasonable compatibility with the typical wireless A/V system. But, there is little incentive for the R/C makers to do that at this point. So, we get what they give us.

It would help out the forum members if you add your country to your profile's location field. Not many folks take the time to do this, but life would be much grander if they did. :)

Added my location to the profile... Thanks...

Well.. Range should be no problem with the VHF radios, but what about intefrerence with others on the same frequency?! Or is this [in fact] an "oberblown" issue. If you are flying in an area where there is [likely] no other R/C activity you should be OK so long as the receiver doesn't get to high in the air. My experience with the ham VHF bands is that the signal can carry, especially near the peak of an 11 year sunspot cycle. Though with a VHF R/C and a UHF camera you will loose the picture before control of the airplane. However, if you can't see what you are doing that's not much help.

So, from what you are telling me, and from my knowledge that UHF tends to be "line of sight", if I keep the plane "in sight", the x10 camera should work just fine, especially if I add some vertical separation between the DSS transmitter, and the x10 receiver??

Again thanks,

Chuck

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So, from what you are telling me, and from my knowledge that UHF tends to be "line of sight", if I keep the plane "in sight", the x10 camera should work just fine

There is more to it than just keeping it Line-of-sight. Antenna polarization, multipathing, RF power, and other gotcha's are involved too.

The X10 camera system is fun to hack and play with. But honestly, it does not have enough Tx power and Rx sensitivity for the sort of practical distances that are expected nowadays. Some of the distance issues could be overcome with very high gain antennas and fixed LOS installations.

If you look through this forum and other R/C video sites, you will see that the X10 solution has long been abandoned for the compact ready-to-use stuff that has come on the market in recent years. These newer systems have RF power that ranges from 10mW to 1W (500mW is typical), and have decently sensitive receivers. I'm not saying that the X10 projects aren't fun, so if you have your heart set on hacking one, then go for it. If you do that then I would recommend boosting its native ~1mW RF power to at least 50mW (for example, http://www.rc-cam.com/forum/index.php?show...695&hl=linx).

It's been years since anyone has mentioned the X10 projects on this forum. At one time we were really having a blast with them. In retrospect, it was sort of stone age compared to what we are using now. But, fun is fun. :)

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Are you aware of anyone who has tried this with the x10 cams and a DSS radio?

I've crashed a plane that was controlled by an XPS 2.4GHz R/C system, because of total loss of control at only 200m distance. The video transmitter was 10mW, located about 15cm away from the R/C RX. There are many more similar stories, which by the way makes me wonder why people start mentioning the lines on the video as the main problem these days. This one is annoying, but rarely strong enough to make you lose a plane, as opposed to the other one...

Edited by Kilrah

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I've crashed a plane that was controlled by an XPS 2.4GHz R/C system, because of total loss of control at only 200m distance. The video transmitter was 10mW, located about 15cm away from the R/C RX. There are many more similar stories, which by the way makes me wonder why people start mentioning the lines on the video as the main problem these days. This one is annoying, but rarely strong enough to make you lose a plane, as opposed to the other one...

Nooo you actually crashed a plane Andre? :o I don't believe it! Your buddy was flying was he?! :lol:

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You didn't state your country, but if you are in the USA, then keep in mind that some of the major R/C mfgs still offer 6-meter RF modules and Rx's (but their choices are slowly drying up). For that reason, there has not been much need to discuss hacking the 72Mhz decks.

Thanks for sticking with me on this... I've done some more reading on the boards.

At this point I am looking to purchase an R/C radio system. Given the bandwidth requirements of video, it makes sense to stick with the high frequencies on this. I want to avoid interference, and being an extra class ham in the USA, it would seem that one of the 50MHz rigs would be a good option (Futaba 9C?). Also, with the 50 MHz system, I could more easily find a commercial Yagi to increase the directional gain and thus (if I am lucky e.g. source of interference is away from the plane) reduce possible causes of interference. At this point I would like to make a decision on an R/C radio system that would "minimally hinder" experiments with video systems on a plane. Specific suggestions as to manufacturers and models would be welcome.

Charles

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At this point I would like to make a decision on an R/C radio system that would "minimally hinder" experiments with video systems on a plane. Specific suggestions as to manufacturers and models would be welcome.

You're now entering the Ford vs. General Motors debate area. Frankly, I suggest you pick the R/C Tx that has all the features you will ever require and go from there. It will need to be one that uses a user-installable RF module; order it with the 6-meter RF deck.

I don't have any strong recommendations. But I suggest you choose a name brand Tx (Futaba, JR, etc.) that has more features than you ever think you will need. Eventually, you will need them, and sooner than you think.

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Eventually, you will need them, and sooner than you think.

After 5 different transmitters everytime more "packed" than the previous one, I can only back that statement...

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Too bad Heathkit isn't still on the market. I have one and it works great on 53 mc. Only problem is it's AM. But might be available on eBay or the QRZ website.

Ron

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Too bad Heathkit isn't still on the market. I have one and it works great on 53 mc. Only problem is it's AM. But might be available on eBay or the QRZ website.

Ron

Based on what I have been able to read [at least] the 9C Super Tx is modular, so when I decide what band I want to use I just get the Tx module, Xtal sets, and the appropriate Rxs. I'm going to set my old Drake R8 receiver scanning on the 6 meter RC frequencies, and just listen for what's happening. Given that 6 meters is less "line of sight" I don't believe that I have to worry that the antenna is on the ground or [as in a plane relatively] near the ground. Also, I'm thinking that the 9C has been around for a while and so is more likely to be found used. I decided to stick with Futaba since I have been using RealFlight for the past year or so. I build a BLT with a larger brushless outrunner motor for the excess weight I hope it to carry. I want to change the stock BLT simulator definitions to include changes for this motor and the extra drag and weight associated with a camera etc, and play with it before I try to wreck the real plane! :) I decided on the BLT because there's not much there but wings, and I can attach things without worrying about destroying a fuselage.

Don't really know if this makes any sense, cause I havn't done it before... Any feedback from you who have would be welcome.

73,

N3BEZ

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Too bad Heathkit isn't still on the market. I have one and it works great on 53 mc. Only problem is it's AM. But might be available on eBay or the QRZ website.

Ron

From reading the boards, it appears that people are using and having success with the following packaged solution...

Aerial Video System 900MHz 500mW KX171

http://rangevideo.com/index.php?main_page=...;products_id=98

If starting again from this system, are there any specific "lessons learned" tips that anyone would be willing to

pass along?

Thanks,

Chuck

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ya, you will get good range and good video stuff from range video :-)

most of my stuff is from him.

but you must select the frequency carefully,

use critias as: what is legal in your area, and what do you expect to add in the future ?

maybe you like to add GPS to your plane, 900 and 1300MHz video links jam GPS receivers much more than 2.4Ghz video tx.

or maybe you like to use 2.4Ghz for RC later ? then you can not use 2.4 for video.

and what ranges do you need ?

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ya, you will get good range and good video stuff from range video :-)

most of my stuff is from him.

but you must select the frequency carefully,

use critias as: what is legal in your area, and what do you expect to add in the future ?

maybe you like to add GPS to your plane, 900 and 1300MHz video links jam GPS receivers much more than 2.4Ghz video tx.

or maybe you like to use 2.4Ghz for RC later ? then you can not use 2.4 for video.

and what ranges do you need ?

Thanks for the feedback.... Yes, I had thought of adding GPS... It occurred to me

(from my experiences in a time long ago) that it would make sense to use a modem on the audio

portion of the downlink of the video camera.... You could add the GPS data as well as other information

there. Even at 1200 baud, it should be sufficient. I think that there are some folks doing that...

Once you have the data link you could add a PIC that monitors the voltage on the plane battery

and send down that information as well (it would be nice to know how much power you have left

in the battery before going ever on...). Likely this is being done as well.

But you are talking about interference from the 900MHz Tx and the 1200-1500 Rx on the GPS.

Interesting, just considering the harmonics it would seem that the 2.4GHz would be more of a problem,

but I haven't actually done it... Thanks for the information/observation. Is this a complete "no go?"

My thoughts are that the 900MHz would have a better range, and so don't want to abandon it lightly.

Chuckle... I started out this thread completely sold on the concept that a 2.4GHz spread spectrum rc control system

is what I should use... After much discussion (here) and throught, I've decided to use the regular old fixed

frequencies, on the Ham 6 meter bands. In theory, the range on VHF should be better in my world (the

rolling hills of SW PA, in fact the VHF repeaters that I have used in the past had a better range than the UHF ones),

and my monitoring of the frequencies associated with those rc channels (at my home) shows some of them to be quite dead.

But again it only takes one problem to crash the plane...

I don't believe that there are any [specific] legal frequency prohibitions in my area. I'm far enough away

from Greenbank WVA. Possibly I didn't understand the point about "legal in my area", can you explain further?

Again, thanks for the thoughts and feedback.

Charles

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I know many GPS units dont have ANY filters in their front end,

I have even seen GPS units with no hi pass filter,

I have even killed a GPS module while powered off, placed in my car, running hi power 14MHz DX in the back yard, LNA fried !!

GPS L1 is at 1.57542 GHz

900MHz video transmitters have no real good anti harmonics filter, so they will be expected to radiate at 1800MHz also

even the fundamental 900MHz will be able to block most GPS units,

you need one with a SAW front end.

Your luck, we at IF have been aware of this issue for a long time, and now we have found a module with filters,

we have made deals with them, and mark is actually shipping right now :-)

I have also experiance with 1300MHz video equipment, it is also jamming GPS modules

like EB85 and EM406

You know harmonics only go up ! they can not go down :-)

so a 2.4GHz video tx have no harmonics below 2.4, but only at 4.8 and so on up,

also the fundamental is far away from GPS frequency and is jamming if mounted too close,

but most planes are big enough to solve this.

local in your area, I mean some frequencies are not open to all people to be used for video BW andthe power we need,

it is different to HAM's we have special wideband ATF channels we can use legally,

in europe 900MHz is not alowed, it is a GSM band.

also if your requrement is LONG range ??

I will stick to VHF RC controll, with large TX antenna and variable PA

Edited by ThomasScherrer

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Thomas,

I appreciate your feedback. I'm going to hold off on the video decisions for awhile till I sort this out. I am going with VHF (6 meters) RC though. No problems here in the US... The only "probllem" seems to be that the equipment is not going to be available in the future. It seems that the major brands are selling off their remaining stock, and that's it. My guess is that some time ago when the US FCC "gutted" the ham exams that the RC manufacturers assumed that there would be people with Tech licenses coming out of the woodwork. But that didn't happen. Given the lack of used [ham RC] equipment that I see on EBAY and the small sales fugures at retail, it's no wonder that the manufacturers are getting out of that band. There's no market for it.

For VHF RC I found an interesting article, and plan on "voiding my warranty" just as soon as I'm sure that the TX works... :)

http://mysite.verizon.net/res7yvp2/w4dh22/id3.html

I would think though that the gain on the UHF video antennas would need to be much higher to be effective, and therefore have a narrower focus (as you are aware I'm sure in antenna design there is no "free lunch"). This being the case it would make more sense to mount the RC antenna with the Video antenna and move them as a unit.

Strangely enough I hadn't considered the ham UHF frequencies for video. It makes sense. I believe that having a GPS is important if for no other reason than getting an idea as to where to start looking for any remaining pieces. :)

Thank you for the food for thought... I'll keep building my plane, flying the simulator (with the camera perspective in the cockpit), reading the boards, and will post here before picking a direction.

Best Regards Old Man,

Chuck

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local in your area, I mean some frequencies are not open to all people to be used for video BW andthe power we need,

it is different to HAM's we have special wideband ATF channels we can use legally,

in europe 900MHz is not alowed, it is a GSM band.

Are you talking about something like this??

http://www.hamtv.com/pdffiles/R-C.pdf

http://www.hamtv.com/pdffiles/TXA5RCbinfo.pdf

Charles

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I've settled on a transmitter....

http://www.transmitvideo.com/pdf/VM-70X_Manual.pdf

http://www.hamtv.com/pdffiles/VM-70XwHS.pdf

I was going to use a B/W camera on this. They are less expensive (about $30US) and can see better in low light conditions. Later I'll experiment adding GPS data to the audio of the transmitter.

For an antenna on the transmitter I was going to use a 1/4 wave (electrical; physically shortened stubby duck) vertical pointing down mounted on the belly. That is the ground plane will be above the radiating element, so the radiant energy will be omni directional and pointing down. This will let me see when the plane is turning, it will also help decrease interference with the on board 50 MHz receiver since it's antenna will be horizontal. I'll start out with 1/2 watt on the transmitter, and test to see if I need to shield the receiver.

RealFlight simulations have shown that the plane that I have now (BLT) wont' hold the projected weight (it doesn't climb much and is not stable like it is without the weight). I'm going to play around with shifting the weight and center of mass on the simulation, but just in case can anyone please suggest a kit plane (balsa frame, high wing, stable flier) that is known to hold 6-8 ounces?

Thanks in advance!

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One of the Telemaster line of planes should do just fine Chuck. You going nitro or electric power??

http://www.hobby-lobby.com/telemaster.htm

BTW, I'd recommend 2.5ghz rather than 435. Equipment is probably cheaper and definitly lighter and you shouldn't have to worry about front end overload with your 6m rcvr..

Edited by W3FJW-Ron

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One of the Telemaster line of planes should do just fine Chuck. You going nitro or electric power??

http://www.hobby-lobby.com/telemaster.htm

BTW, I'd recommend 2.5ghz rather than 435. Equipment is probably cheaper and definitly lighter.

Electric.

Yes, one of these should do the trick... Thanks!

There is also a Real Flight model for the larger one that I could adapt....

http://www.knifeedge.com/forums/downloads....ile&id=1293

I'll play with it on the simulator and see how it files with the extra weght!

Yes, the 2.5 ghz equipment is lighter and cheaper. However, the propagation is better on the 70-cm band (for equivalent power) and a ham can legally use more power. You just have to ID after 1W (call sign painted on the fuselage in view of the camera), and not "step on anyone". The TX and RX are synthesized so I can change frequencies if necessary. Also, since I'm going to use a low light level B/W camera, I almost need to have auto iris, so there will be "a few extra ounces to reckon with" anyway.

Again Thank You.

Best Wishes Old Man,

Chuck

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Good luck with your project Chuck. Come back and let us know how it goes.

Ron

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I wouldn't use TV band transmitters. My experience with those showed that it's good for fixed links, but as soon as they move the transmission is much less reliable. It would be a good idea to find a better receiver than the ones you can find in TV's as well, their sensitivity is usually pretty poor.

Edited by Kilrah

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