HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jun 17, 2013, 01:09 AM
Registered User
Canada, NL, Corner Brook
Joined May 2011
158 Posts
Discussion
Dragonlink & Video TX/RX Selection? Does dragonlink interfere 1.3ghz?

Hi there
I heard that 1.3 Video TX / RX is bad with dragonlink because of the harmonics or something like that where dragonlink runs 433mhz.

But I also heard that I could get a filter which makes sure dragonlink doesnt interfere with the 1.3 system.


Here is a quote from the dragonlink website:

"PUT A HIGH PASS FILTER ON YOUR VIDEO RECEIVER: If you are stuck with a poorly filtered, cheap receiver, you can install a low pass filter in the antenna line. This is expensive and may or may not solve your problem. The price of this filter will be almost what a good quality receiver cost, so I am hesitant to recommend this, because you should buy a new video receiver first. For someone that has tried everything, and is out of solutions, the high pass filter is a possibility. You can get these filters from www.minicircuits.com Get the SHP-800 filter if you are using 900 MHZ video, and get the SHP-900 filter if you are using 1.2 GHZ, 1.3 GHZ, or 2.4 GHZ video."



What if i use a good receiver like a 1.2 lawmate does that have a filter built in??

whats the best to use with the dragonlink, and can I choose any setup?

I also have a DJI phantom which runs 2.4 mhz, can I use a 2.4 video tx/rx with that or am I asking for trouble?
Can I use the 1.3 ghz or 1.2ghz lawmate system with the 2.4 DJI phantom?



Thank you for your help!
85miles is offline Find More Posts by 85miles
Reply With Quote
Sign up now
to remove ads between posts
Old Jun 17, 2013, 10:00 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,530 Posts
The truth is, it's a crap shoot. Some DragonLink units are clean and you can run a cheap RX and never have a problem. Others are dirty and the best RX in the World isn't going to help. The interference comes from the case, not the output stage so filtration will not help.

I have tested 4 DragonLink units now. All of them cause interference on 1.3GHz video no matter what RX you run. If you want to run DragonLink, use 2.4GHz for video. This works well.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
Reply With Quote
Old Jun 17, 2013, 07:58 PM
Registered User
Joined Mar 2009
1,112 Posts
It seems that not a lot of people are using the proposed filter : a google search on

rcgroups "SHP-800"

brings only 2 results : one of them being the current thread

So it's difficult to be sure it's a good solution. I'm surprized, because the underlying explanation is that the VRX would be perturbed by the 432 MHz.
I rather consider (and my spectrum analyzer agrees), that the VRX is perturbed by harmonics in the 1.3 GHz range. But so far I've only tested a DL V1, maybe the V2 is better.


You can also separate the VRX antenna with a few meters of coax, or (what I did), separate the RC TX with a a few meters of coax.
flipflap is offline Find More Posts by flipflap
Reply With Quote
Old Jun 17, 2013, 09:13 PM
Stay airborne my friends
rc-mike's Avatar
USA, TN, Dickson
Joined Nov 2004
998 Posts
I am far from an expert and don't know 1/10th of what IBCrazy does but mine has worked fine for what I do on 1.3. I have gone over 10 miles before with it. Now if I hold my DL transmitter within a foot or two of the VRX the video will get a lot of interference in it but I normally sit my ground station out 10 feet or so from myself.
rc-mike is offline Find More Posts by rc-mike
Reply With Quote
Old Jun 17, 2013, 11:17 PM
Crashaffinity on youtube
CrashAffinity's Avatar
Joined Nov 2012
2,960 Posts
Quote:
Originally Posted by 85miles View Post
Hi there
I heard that 1.3 Video TX / RX is bad with dragonlink because of the harmonics or something like that where dragonlink runs 433mhz.

But I also heard that I could get a filter which makes sure dragonlink doesnt interfere with the 1.3 system.


Here is a quote from the dragonlink website:

"PUT A HIGH PASS FILTER ON YOUR VIDEO RECEIVER: If you are stuck with a poorly filtered, cheap receiver, you can install a low pass filter in the antenna line. This is expensive and may or may not solve your problem. The price of this filter will be almost what a good quality receiver cost, so I am hesitant to recommend this, because you should buy a new video receiver first. For someone that has tried everything, and is out of solutions, the high pass filter is a possibility. You can get these filters from www.minicircuits.com Get the SHP-800 filter if you are using 900 MHZ video, and get the SHP-900 filter if you are using 1.2 GHZ, 1.3 GHZ, or 2.4 GHZ video."


What if i use a good receiver like a 1.2 lawmate does that have a filter built in??

whats the best to use with the dragonlink, and can I choose any setup?

I also have a DJI phantom which runs 2.4 mhz, can I use a 2.4 video tx/rx with that or am I asking for trouble?
Can I use the 1.3 ghz or 1.2ghz lawmate system with the 2.4 DJI phantom?



Thank you for your help!
for the questions of yours that haven't been answered...

if you're using 2.4ghz control don't use 2.4 video, it's a recipe for disaster, they'll fight each other.

regarding control, consensus seems to be to always use rc control at a lower frequency then your video. In your case, you're flying a phantom, it's not really a long range flyer anyways, 5.8ghz video would likely serve you well (it won't interfere with pretty much any control system from what i've seen), but if you're already invested in 1.3, well, can't help you there.

lastly, if you're using UHF (433 ish) and it's interfering with your 1.3 video, filters will likely not do much, since the video is likely very close to the 3rd harmonic of the UHF. better receivers (with SAW filters) help greatly, channel selection as well (dependent on available channels in your country too). Using UHF with 1.3 video tends to be more of an advanced FPV thing.

Since you haven't stated your FPV goals it's hard to give you rock solid advice.
CrashAffinity is offline Find More Posts by CrashAffinity
RCG Plus Member
Old Jun 17, 2013, 11:47 PM
fly by night
BCSaltchucker's Avatar
Joined Sep 2011
5,751 Posts
tell you the truth if I was starting over, I would just get the EZUHF or Scherrer instead of Dragonlink. In fact now I may soon own both DL and TS, but never had UHF interfere with my 1280 video (I think).

multicopters can't go too far, always see them as: 5.8 good enough, 5.8+2.4RC solves all your problems. But then have GPSRTH on it just in case.
BCSaltchucker is offline Find More Posts by BCSaltchucker
Last edited by BCSaltchucker; Jun 18, 2013 at 12:54 PM.
Reply With Quote
Old Jun 18, 2013, 09:57 PM
Registered User
Canada, NL, Corner Brook
Joined May 2011
158 Posts
Quote:
Originally Posted by CrashAffinity View Post
for the questions of yours that haven't been answered...

if you're using 2.4ghz control don't use 2.4 video, it's a recipe for disaster, they'll fight each other.

regarding control, consensus seems to be to always use rc control at a lower frequency then your video. In your case, you're flying a phantom, it's not really a long range flyer anyways, 5.8ghz video would likely serve you well (it won't interfere with pretty much any control system from what i've seen), but if you're already invested in 1.3, well, can't help you there.

lastly, if you're using UHF (433 ish) and it's interfering with your 1.3 video, filters will likely not do much, since the video is likely very close to the 3rd harmonic of the UHF. better receivers (with SAW filters) help greatly, channel selection as well (dependent on available channels in your country too). Using UHF with 1.3 video tends to be more of an advanced FPV thing.

Since you haven't stated your FPV goals it's hard to give you rock solid advice.

Thanks for the help guys you answered a lot of my questions.

I have the dragonlink v2 with a 1.3 800mw (as well a 200mw) TX/RX setup from BEVRC, I usually get interference and cant seem to fly that far, although one day I was able to go 1.5 kms on the 200mw vtx click here for that video (crash at end).

I ordered a 5.8 600mw Immersion TX & RX, as well I ordered a Lawmate 1.3 500mw for my friend to use with his bixler which I may try with my plane as well..
I have a skywalker and I just ordered a skysurfer 1400 because I am so impressed with my friends bixler, want something smaller and simpler yet able to carry my gopro and video gear with at least 20 minute flight would be good for me.

I have a skywalker but that is a tank, and I have crashed it a few times, this video being one of which, I have it fixed but want to save it until im more used to flying FPV, Like i said before the furthest i have gotten is 1.5 km and only turned around because I was nervous. I also have a Cyclops OSD with RTH, the RTH part im still trying to figure out, seems some times it works, some times it doesnt come all that close to me on its way back, and one time it just lost all altitude and nearly hit the ground if it wasnt for me manually interfering.

Anyways rambling on here,

I have the 5.8 Immersion 600mw ordered from RMRC so I cant wait to get that, also got the spironet antennas with that so I hope to go about 2km or so and I will be happy for now, as well I can just throw this on the phantom and its small and EASY... I like that word EASY.

Oh my friend wants to know if that 1.3 lawmate setup is fine for now with his 2.4 ghz radio (he plans to upgrade later)
85miles is offline Find More Posts by 85miles
Reply With Quote
Old Jun 18, 2013, 10:15 PM
Registered User
benderfly's Avatar
Joined Sep 2007
776 Posts
It seems very strange to me that it is not mentioned up front in all of these posts that this interference, consistent across production units or not, is easily mitigated by separation of the control TX and video RX, which should be practiced anyway.
benderfly is online now Find More Posts by benderfly
Reply With Quote
Old Jun 18, 2013, 10:21 PM
Registered User
benderfly's Avatar
Joined Sep 2007
776 Posts
Quote:
Originally Posted by IBCrazy View Post
The truth is, it's a crap shoot. Some DragonLink units are clean and you can run a cheap RX and never have a problem. Others are dirty and the best RX in the World isn't going to help. The interference comes from the case, not the output stage so filtration will not help.

I have tested 4 DragonLink units now. All of them cause interference on 1.3GHz video no matter what RX you run. If you want to run DragonLink, use 2.4GHz for video. This works well.

-Alex
I do not understand this post. I offered my DL up for testing to make sure the pool was big enough. You tested 4 all with interference but it is a crapshoot?

And still not mention just to put some distance between tx and rx. Do you not do this anyway? What am I missing here in this equation?

How come I have no problem flying DL and 1280/1258mhz video? With either of my two DL units?

respectfully,
Bender
benderfly is online now Find More Posts by benderfly
Reply With Quote
Old Jun 18, 2013, 10:50 PM
Crashaffinity on youtube
CrashAffinity's Avatar
Joined Nov 2012
2,960 Posts
Quote:
Originally Posted by benderfly View Post
It seems very strange to me that it is not mentioned up front in all of these posts that this interference, consistent across production units or not, is easily mitigated by separation of the control TX and video RX, which should be practiced anyway.
that's a good point actually!
CrashAffinity is offline Find More Posts by CrashAffinity
RCG Plus Member
Old Jul 29, 2013, 11:20 AM
Registered User
Joined Apr 2011
39 Posts
I Use 900mhz 800mw combo from hobbyking and have interference. So, what's the solution? Receiver with saw filter?
unixoid26 is offline Find More Posts by unixoid26
Reply With Quote
Old Jul 29, 2013, 01:14 PM
Registered User
casualsunday's Avatar
United States, CA, Lancaster
Joined Jan 2013
274 Posts
Uhm, pretty sure that has nothing to do with Dragonlink. There's something else in your system causing interference.

For everyone else having interference on 1280, let Mike (Jettpilot) know and he'll send out a board that works well with 1280. They've fixed the issue.
casualsunday is offline Find More Posts by casualsunday
Reply With Quote
Old Jul 29, 2013, 04:05 PM
Registered User
Joined Apr 2011
39 Posts
When I fly with 2.4Ghz, all good. Only with Dragonlink.
unixoid26 is offline Find More Posts by unixoid26
Reply With Quote
Old Jul 29, 2013, 04:36 PM
Registered User
Joined Oct 2012
2,164 Posts
noise is noise, but there are no known issues with DL and 900mhz, only on 1.3mhz. Though I suppose 900 might be close to the 2nd harmonic...

In any case, it could be as simple as the power of the dragon link being greater than that of your 2.4ghz radio.

Try adding physical separation between the dragon tx and the video rx.

I have the 2 on separate tripods each extended 6 feet in opposite directions from my ground station. I figure it cant hurt anything...
bauerbach is offline Find More Posts by bauerbach
Reply With Quote
Old Jul 29, 2013, 06:55 PM
Registered User
Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
28,866 Posts
The cheap digital display VRXs (0.9-1.3Ghz) pick up noise from UHF systems regardless
of what channel is chosen. It's a problem with the VRx, and it can't be cured with
external filtering. They seem to pick up the primary UHF Tx frequency directly.
RMRC's "V3" version of the digital display Rx is better, but still
not as noise resistant as a Racewood Rx.

Just don't confuse this with the fact that some DL Tx's produce 3rd order harmonic noise
on/near 1280Mhz, regardless of VRX used. They're two different problems.
Daemon is online now Find More Posts by Daemon
RCG Plus Member
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Question What Are Some Of The Best Video Tx/Rx in 1.3ghz To Use For Long Range FPV? superjon FPV Talk 26 May 16, 2013 10:45 PM
Wanted I am looking for Rangevideo 1.3GHz 800mW tx and Bevrc 1.3GHz rx Sethe FPV Equipment (FS/W) 0 Apr 25, 2013 06:00 PM
Wanted 1.2 / 1.3ghz TX / RX Doodie FPV Equipment (FS/W) 2 Mar 08, 2013 07:17 AM
Wanted 1.3Ghz Video TX and RX johnorama Aircraft - General - Miscellaneous (FS/W) 2 Apr 13, 2010 01:50 AM
Found 1.3Ghz Video TX and RX johnorama Aircraft - General - Miscellaneous (FS/W) 2 Apr 06, 2010 02:46 PM