|Aug 25, 2008, 03:44 AM|
you know this site:
see top connector, I belive it is your connector.
you are right pin 2 is PPM out
and pin 3 is PPM input, you have a scope ?
so you can check levels ? and check the repeat time is constant as required.
is not legal i europe, so I dont own such devices sorry (they also jamm GPS receivers)
so I can not reallife test it, but I can make you an offer, how about this:
if it fail for you, you can send it back and have full refund, is that ok ?
then you simply test it all, for all of us with legal 900Mhz used the way it is ment to be used for you,
as a radioamateur you know all about how to install transmitters and receivers on planes, it is always recommended to use as much distance as possible, I have seen many people use too small planes for FPV with too much delicate equipment on them, that is more likely they will have problems specially with some types of video cams and some types of GPS units.
it is explained the frequency range is 410 to 450Mhz you can use any frequencys pair
you like in this band, you live in the EU so you will find several channels free in the 433-434 and 444 MHz band where it is ok to transmit even 500mW with no licence,
how ever you always need a HAM licence to be able to use the 7W booster (legally)
|Aug 25, 2008, 07:10 AM|
thanks Thomas, do you know where I can find out exactly what frequency I can use ? to buy it or not to buy it depends all from that essentially...
I wrote to the Italian ministry of communications and they replied me this:
According to our National Plan for radio frequencies, such "control model" must use the airplanes for 35 MHz and 40 MHz for terrestrial models. Regarding brands and models, can 'consult our database to verify their compliance'.
On the use of radio for aeromodels, you must ensure that the devices conform to the standard EN 300 328 radio, and that 'the standard radio on 1 of 3 essential requirements of Directive 99/5/EC. So the user can use that frequency freely only in a private fund. For use on public fund use must be authorized by 'territorial Inspectorate responsible for the region using' Annex 19 to the Code of electronic communications. Regarding the maximum allowed power can 'call Mr. Forresu the number xxxxxxxxx.
Ministry of Economic Development
so after readinf this I'm more confused than before ahah..
|Aug 25, 2008, 08:37 AM|
I got the same kind of ansver the first time I asked,
you just where unlucky to find a person that knows nothing :-)
in EU you will find alocated channels in the 70cm band 430-450MHz band
that is allocated for ISM and other free of license usage, all you need to do is to call a person that knows much more about it, they have PDF files will all frequencies listed with detailed explainnations about what rules apply to each of them.
|Aug 25, 2008, 08:44 AM|
sorry the text is in Danish:
but you will see all the normal EU listed frequencies for models,
and wow aha 10 more in the 70 cm band with 500mW ERP, nice !
and again here:
you will have something like this also:
then you simply put in 420 to 450MHz in the search and find all rules and regulations
|Aug 25, 2008, 10:34 AM|
This website can be used for The Netherlands (website in English, use this website for dutch):
I am pretty sure for other countries something like this website does also exist.
Maybe Thomas can see what the possibilities are for using his system in The Netherlands.
|Aug 25, 2008, 04:42 PM|
Joined Jan 2007
Put it 10meter back away from video receiver, and height about 2meter up.
|Aug 25, 2008, 05:05 PM|
in any case we are not legal when flying that high right? I think max altitude above ground level for RC airplanes is 300 feet... we can cause a catastrophe if an airplane strike our airplanes... is there any kind of radar altimeter for the rc autopilots altimeters or gps altitude is safe enough when flying like 300 feet for example?
thanks, and thanks for the links about frequencies guys.
|Aug 25, 2008, 05:15 PM|
Hey Mr. Thomas, I did read your last post for me but today I just got an idea. Since I have a dual band 2m/70cm band mobile radio that will output 50 watts on 70cm can't I experiment to see which channels will or won't affect the 900mhz video while I transmit from the 70cm band near the 900 mhz patch whlie looking through the goggles? Won't this help determine exactly what frequencies will or won't interfere so you will know which frequency to put your kit on?
I've already done some very brief experimenting and yep there are certain frequencies that cause interference in 900mhz video and others that don't at all. If this method will work in finding frequencies that don't interfere I can make a list and compare with the band plan to come up with two for you to program into your kit.
I'm very close to ordering.
|Aug 25, 2008, 05:38 PM|
|Aug 26, 2008, 03:15 AM|
EXACTLY Carlyle, your findings can save us alot of time later,
also try to experiment with hi-mid-low power of your 70cm rig, and the distance from your video receiver to 70cm tx.
use a dummy load on your planes 900MHz tx and put it so far away you see a bit snow on the picture, now it is easy for you to prove jammed or not.
I have ordered a few of those round (odd pinned) connectors and have a "date" with another club member, in a few days I can inform if his Futaba type is compatible :-)
please read about the 1/10 rule of thumb mentioned a few times in this thread,
you need height to be able to fly far avay, else you loose line of sight
and radio range will decrease dramatically ! specially on the higher video bands like 900 and 2.4
thanks for the information, think about placing both antennas in a link using same polarisation, like if your wire antennas for the RC are both horizontal in the plane, your TX antenna should also be horizontal, the end of the tx antenna should point 90 deg to plane.
your video tx antenna in plane should point up or down, and your ground receiver beam should also point up/down, now you will gain 26dB on both links !!
and you have minimized the interferience (if any) from the two systems by a factor of 26db too !
|Aug 26, 2008, 09:20 AM|
Ok, I have done some testing and found that 437 through 450 mhz is clear on the 900mhz video even when transmitting on 50 watts of power. Of course, medium and low power are also clear. And when I say clear I mean clear with no noticeable static, wavy lines, interference of any kind. All of the channels between 437 and 450mhz was clear. Now below 437mhz starting at say 436.9mhz there was interference on 50watts which appeared as lines of static kind of like what a sewing machine or cheap kitchen mixer will do to a tv set. At some other very narrow ranges below 437 it was really bad even on low power, but there were other very narrow ranges below 437 that had no interference but only of a few kilohertz. However, nothing as convincing as the results I got over 437mhz. My radio has a 70cm range of 430 through 450 mhz so I was not able to test below 430mhz. The video transmitter is operating on 910mhz.
So here was the test conditions I used. 910mhz transmitter on 500mw with a 3db rubber duck inside the house. I went outside and setup the patch on the back of my truck and turned it just until the signal started to get in the null. The 70cm radio had a mag mount antenna on top of my truck which was probably a couple of meters from the patch. I will probably use this same mag mount with Thomas's system. Then while watching through the goggles I started transmitting from my 70cm radio.
Some other notes, high power was 50 watts, medium power was 25 watts, and low power was 5 watts. Low power didn't seem to cause that much intereference for a majority of the band, only at those channels where high power caused the most did it show up on low power. The results I got below 437 mhz didn't seem to be very repeatable with the same result. For example I had to pause testing to do something else and came back an hour later only to get a difference kind of static or more static at the same ranges below 437mhz. However as I said before anything above 437mhz was absolutely clear with repeatable results.
I will try to set the plane far away at 2000 feet or so and try this again to see if the results are repeatable. Then if that proved successful I will try it while flying around some if this storm will ever pass on through.
|Aug 26, 2008, 12:30 PM|
Joined Aug 2008
I have been looking everywhere for a solution like this. Are you still making this equipment? If so I would like to place an order. What video euipment are you using in conjunction?
|Aug 26, 2008, 12:58 PM|
thanks alot Carlyle, try to weaken the 910MHz video tx so you see alot of snow,
but constant snow, the way I do this if by using a dummi load, if you place the tx in your house and by that way weaken the signal you will get a variation in signal when cars pass by or people walk arround the house, it is very easy to see if strong RF will decrease the 910MHz receiver when the signal is with snow.
so even when using the 7W booster option you expect to see no problems even if mounted close to video receivers, specially if the frequency is over 437.
I think it might be different from brand to brand, like how well do they filter the input?
and how well are they shilded ?
yes Ian, still available, please read post #1 for all prices and delivery time and postage methodes, and if any tech questions just post here so we can all share it.
I am eger to support this system for many years !
|Aug 26, 2008, 08:52 PM|
I did some more testing this afternoon. I don't have a dummy load so I set the plane up on a stand in my front yard and went down to the field about 2200 feet away with line of sight and no obstructions. Same setup at the truck with patch on back of truck and mag mount antenna on top.
The image I had in the goggles was like a very weak uhf TV station with a moderate amount of snow but still a useable picture.
Below 437 mhz on 50 watts I got same kind of interference, it only added to the existing snow. I tried med (25 watts) and low (5 watts) power at various points below 437mhz and got less interference with med power and no interference on low power. But still a useable picture.
Now here's the kicker. Between 448.5 and 450mhz it completely whited the picture out on full power. Nothing left but a white screen. It wanted to do it at med power but not quite and on low power I could see some artifacts but still a useable picture. It immediately came back once I quit transmitting.
I found that below 448mhz on full power was the threshold for no interference and certainly none on med or low power.
So it appears now that the useable channels are between 437 and 448 mhz and with only a 7w booster it appears the 910mhz video will be safe here.
Thomas didn't I read where you could adjust the power on the booster simply by adjusting the input voltage or is there another way to do it?
And do you have the filter on the transmitter as well like you do on the receiver? The one that blocks 2.4ghz and also some on 900mhz?
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