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Old Jun 04, 2011, 09:34 PM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
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Originally Posted by gmflyer View Post
Thanks, that's good advice and probably where i'll head if there's not another alternative - but I have ENJOYED the glitch free flying for the last 2 years on 2.4 in the city.

Greg
On 72mhz, the older FM receivers just pass whatever signal the got on to the servos. In the old days, they fixed this by using PCM which contains a checksum. Some modern FM receivers use a computer chip (DSP) to watch the signal. If they get a signal that doesn't make sense (missing a servo pulse, all servos moved at once, all servos going full clockwise, momentary and sudden drop in signal level, etc.) they skip that signal, hold everything where it is, and wait 1/50th second for the next set of servo positions to arrive.

A couple weeks ago I test flew a Futaba R127DF (FM) receiver against for instance some Futaba PCM's and the Corona RP8D1 with a reduced transmitter antenna. The R127DF was the only one that glitched at max range. The others went farther (There appears to have been interference present during my R127DF test flight. Flying that R127DF a different day gave a better result). The PCM's went a little farther (probably with humanly undetectable short lockouts) and then just locked out instead of glitching.

All 2.4g radios that I am aware of have receivers that have the same effect as PCM or DSP on 72mhz.

On the other hand, on 2.4g, you know you aren't going to be shot down by someone transmitting on your channel.

Cliff
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Old Jun 05, 2011, 01:50 AM
John
United States, WA, Mason
Joined Apr 2011
796 Posts
All right, you guys are talking me out of my Spektrum 2.4 and into 72mhz. I am negotiating on a "Futaba T7UAP Super" the Rx is FP-R127DF 7channel, crystal is channel 18. Does anyone know anything about that Radio?? -- thanks, JOHN
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Old Jun 05, 2011, 02:06 AM
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Originally Posted by digitalCAM View Post
All right, you guys are talking me out of my Spektrum 2.4 and into 72mhz. I am negotiating on a "Futaba T7UAP Super" the Rx is FP-R127DF 7channel, crystal is channel 18. Does anyone know anything about that Radio?? -- thanks, JOHN
If I may suggest, go with a 9CAP Super.
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Old Jun 05, 2011, 02:24 AM
John
United States, WA, Mason
Joined Apr 2011
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Originally Posted by AVIATION_RULZ View Post
If I may suggest, go with a 9CAP Super.
If the price on this one was only $50, would that make a difference for which one? or still try to find 9cap? - thanks, JOHN
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Old Jun 05, 2011, 02:59 AM
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Originally Posted by theothercliff View Post

There just is not that much difference between 900 and 1300.

Cliff
Thanks Cliff!
I might not made myself clear. I want to make dipole antenna, one for 1,3 and one for 900 FOX-800 and HK-200, cos I have both. The question is what exactly frequency to choose among channels, that is more efficient and not interfere with FRSky?

Frequency for 900MHz I have to choose: 0.9G 0.910G,0.980G,1.010G,1.040G?
For 1,3 more or less 1240 or 1280?

No legal restrictions!
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Old Jun 05, 2011, 09:58 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
3,135 Posts
Quote:
Originally Posted by AVIATION_RULZ View Post
Quote:
Originally Posted by digitalCAM View Post
All right, you guys are talking me out of my Spektrum 2.4 and into 72mhz. I am negotiating on a "Futaba T7UAP Super" the Rx is FP-R127DF 7channel, crystal is channel 18. Does anyone know anything about that Radio?? -- thanks, JOHN
If I may suggest, go with a 9CAP Super.
I have two 7UAPS systems with the R129DP PCM receiver and I can report that they are excellent for FPV. Bad things are that the long switches on the transmitter break off if mispacked for transportation (probably true of the T9CAPS too) and they only have 4 model memory.

Unfortunately, the R127DF receiver I tested with the same transmitter (T7UAPS) have half the effective range of the R129DP. Even the cheap Corona RP8D1 DSP receivers do better than the Futaba R127DF. Here is a post comparing range from last week. My wild guess is that you would get 1 mile with the R127DF before it started mild glitching (There appears to have been interference present during my R127DF test flight. Flying that R127DF a different day gave a better result) and 2 miles with the R129DP before mild lockouts. Doubling the receiver antenna length (not more) doubles the range.

I have watched eBay for a while and generally the 9CAPS systems cost twice as much as the 7UAPS systems (all used).

Cliff
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Old Jun 05, 2011, 11:10 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
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Originally Posted by RocketMouse View Post
Thanks Cliff!
I might not made myself clear. I want to make dipole antenna, one for 1,3 and one for 900 FOX-800 and HK-200, cos I have both. The question is what exactly frequency to choose among channels, that is more efficient and not interfere with FRSky?

Frequency for 900MHz I have to choose: 0.9G 0.910G,0.980G,1.010G,1.040G?
For 1,3 more or less 1240 or 1280?

No legal restrictions!
Good antennas make more difference than selecting a channel within a band.

You can do a range test to select your exact frequency, but the problem is that the antennas themselves may work better at one end of the band then the other. For most people it is easier, cheaper, and a good learning experience to spend a whole day making several antennas that only differ by 0.5mm to 1mm and another whole day range testing them.

Testing efficiency of transmitters is doable (mainly, power output into a resistive load). Testing efficiency of receivers is difficult and requires training and expensive equipment. Most testing shows that there is usually no more than 20% difference in distance between best frequency and worst frequency and often only 5% difference for the narrow ranges you listed.

Most people who test, only test the transmitter, but that is only half the testing. Most people do not test at all. They buy and use the frequency for their country.

All countries have laws about frequencies and generally require a license to run an FPV transmitter that has enough power to go more than 10 meters. I am not suggesting that you run an FPV transmitter without a license, but whether you get a license or not you should use only your country's (or your location's neighbour countries') correct frequencies. If you had to buy a car to drive without a license you would buy one that was legal to drive if you had a license, correct? Maybe you decide to get a license later...

You will avoid people interfering with your signal as well as you interfering with theirs if you get a legal frequency.

FRSky is 2.4g which is really anywhere from 2.4g to 2.5g frequency (about).

To use 2.4g RC, do not choose any FPV frequency that has harmonics (1, 2, 3, 4, 5, 6, 7) close to 2.4g to 2.5g or you can get a low pass filter (for FPV frequency below RC frequency) for the FPV antenna.

1.24 would not be good because 1.24 times 2 is 2.48. 1.200 and 1.280 are also too close. 0.910 is better because 2 times 0.910 is 1.820 and 3 times 0.910 is 2.730

Europe uses 900 (around there) for cell phones so 900, 910 is probably not good in Europe. In Europe, 980 may be best if it is legal. I recall that the area around 1010 and 1080 is internationally reserved for full sized airplane radio navigation. For 2.4g RC I probably wouldn't use 1240 and to use 1280 I would use a low pass filter on the FPV transmitter antenna.

Cliff
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Old Jun 05, 2011, 01:14 PM
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It's much more clear now!
Thanks a lot Cliff!
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Old Jun 05, 2011, 02:55 PM
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United States, OH, Columbus
Joined May 2009
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Quote:
Originally Posted by theothercliff View Post
On 72mhz, the older FM receivers (e.g. Futaba R127DF) just pass whatever signal the got on to the servos. In the old days, they fixed this by using PCM which contains a checksum. Some modern FM receivers use a computer chip (DSP) to watch the signal. ...

Cliff
Thanks, Cliff - that straightens out what to look for in 72mhz radios and PCM-DSP and why. I skipped over it in my life - having built and briefly flown RC with a gold faced Futaba on the old freqs outside of college - around 1986. Then nothing for 20 years, then luckily, at a local show here in Columbus about 3 years ago - someone enthusiastically steered me to the dx6i as a good first radio to get back into the hobby and it has more than met all my needs. But now I see that there are far better choices for this new animal (for me) FPV.

Greg
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Old Jun 06, 2011, 10:16 PM
Certified Crash Artist
United States, CA, Garden Grove
Joined Feb 2011
152 Posts
Hey guys
I have tried 2 1.3ghz and one 900mhz set ups with no luck in my area. I was getting 10ft max with 1.3 and no picture on 900mhz. I live 2 blocks from 2 cell towers and checked for amature lisences in my area and there is around 350.

Should I even attempt a Foxtech type of 5.8ghz set up or throw in the towel?

I live in orange county ca , does anyone have anything that works around here?
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Old Jun 06, 2011, 10:17 PM
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United States, WA, Enumclaw
Joined Nov 2001
752 Posts
Woohoo! I just finalized my orders of the *bestoffer* system, and the camera/connector that theothercliff recommends.

The Bixler looks really tempting... can any of you think of any negatives with that platform?

Oz
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Old Jun 06, 2011, 10:20 PM
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United States, WA, Enumclaw
Joined Nov 2001
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Great video! I stumbled on these great RC videos by Flite Test. This video did a fantastic job explaining the different antenna options and the pros/cons with each. They even gave a very nice compliment and thank you to IBCrazy! Much deserved.

I love their video's though... if you've got 10 minutes, it's worth the time.

Oz

Flite Test - FPV Antennas - FLITE TIP (9 min 42 sec)
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Old Jun 07, 2011, 12:12 AM
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United States, TN, Nashville
Joined Jun 2009
75 Posts
Best way to display your FPV?

I just recently got into FPV and have done a ton of research and reading to figure out what I need. I just wanted to know what you guy's preferences of displays are for a camera such as the DX201.

Is any display over a foot or so in length will not work?
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Old Jun 07, 2011, 05:47 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
3,135 Posts
Quote:
Originally Posted by Orcoz View Post
Woohoo! I just finalized my orders of the *bestoffer* system, and the camera/connector that theothercliff recommends.

The Bixler looks really tempting... can any of you think of any negatives with that platform?

Oz
The Sky Surfer / Bixler (brushless version, plus version #1) is the airplane I would recommend most for FPV. Read the Sky Surfer / Bixler thread for advice.

Personally, I would try to Y the rudder into the ailerons (if it is not backwards) and use the rudder channel for camera panning.

Cliff
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Old Jun 07, 2011, 06:02 AM
Specializing in RC since 1972
Temple, GA, USA
Joined Jun 2009
3,135 Posts
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Originally Posted by Lucasberg View Post
Hey guys
I have tried 2 1.3ghz and one 900mhz set ups with no luck in my area. I was getting 10ft max with 1.3 and no picture on 900mhz. I live 2 blocks from 2 cell towers and checked for amature lisences in my area and there is around 350.

Should I even attempt a Foxtech type of 5.8ghz set up or throw in the towel?

I live in orange county ca , does anyone have anything that works around here?
You need to run 1280mhz or 910mhz in the USA. These frequencies should only have video on them and amateurs don't usually send video. By the way, all FPV video frequencies are "line of sight" and get blocked by "everything" but air.

Where these all new systems? What power output where they? I cannot imagine 0 to 10 feet with 3 different systems of at least 50mw power level. If you don't know the power level, it is not enough. 700mw to 800mw will get you more than a mile on stock antennas if the stock antennas are correct for the frequency (that is a question with some sets).

If these were "complete system with transmitter built into the camera" like from eBay, then I can imagine it.

I recommend the BestOfferBuy system as it works for at least a mile on stock omni antennas. There are others that are as good, but rarely as cheap.

I routinely fly two blocks away (say 700 yards) from a cell tower and fly out past and around it on both 910 and 1280.

Cliff
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