Espritmodel.com Telemetry Radio
Reply
Thread Tools
This thread is privately moderated by IBCrazy, who may elect to delete unwanted replies.
Old Aug 22, 2011, 08:21 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,301 Posts
Quote:
Originally Posted by jasmine2501 View Post
Yeah I was just meaning the 1280MHz vs 2.4GHz setup - which is what I use. The video transmitter I used reduced the range with the AR6100 receiver, but I don't see any difference with the R921. So, it is doing something to it, but it's not the harmonic interference, it's more likely just plain old swamping because the higher quality receiver eliminated the problem.
You are likely correct here. The filters within an RX do not have perfectly sharp cut off points, but are actually curved. Chances are they are Chebyshev types (as opposed to Butterworth or Sallen-key) and thus there are going to be some oscillations in the filtration scheme over the cut off band frequencies. The strength (also known as order) of this filter determines how much out of band noise it can filter out. Thus you can knock out a 2.4 GHz system with a 72 MHz system if the 72MHz is close and powerful enough despite having incredible separation.

I have found that Spektrum systems have poor filtration and that's probably why most people have issues with them for FPV.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Sign up now
to remove ads between posts
Old Aug 22, 2011, 09:01 AM
Nakelp
nakelp86's Avatar
United States, NJ, Union
Joined Sep 2004
6,780 Posts
Thx Alex , but I dont see anything about 2.4
nakelp86 is offline Find More Posts by nakelp86
RCG Plus Member
Latest blog entry: New (old) Disco gimbal
Reply With Quote
Old Aug 22, 2011, 01:40 PM
KJ6RCJ
gent96's Avatar
United States, CA, Elk Grove
Joined May 2010
406 Posts
To Alex (IBCrazy),

Hi!. Noob here. I have a Skywalker with with an AR7000 RX. I bought a 500mw 900mhz FPV system from ReadymadeRC and mounted the video RX on the flat section on the Sw's tail. I also bought one of your Vee antennas from RMC and installed it on a flat stick protruding from the SW's tail just behind the RX. I also have a low pass filter between the Video TX and the Antenna. I mounted the video camera on the top section of the SW with a servo for panning. When I tested the the system, I could only make some 500 to 700 yds range estimate on the FPV before the signal becomes scratchy then I have to turn back. It is to note that I fly with an 8dBi patch antenna oriented about 35-45 deg, 6 inches from the ground. I fly on an open farm land with a cell tower about a mile away. My questions:

1. Does my placement of the vid TX affecting its range? I placed my RC receiver inside the fuselage. I also wound up the servo wires, even the video/ audio cables, with ferrite rings. Is it better to mount the video tx and antenna on a wing rather than the tail?

2. Does the cell site tower also affect the transmission of 900mhz signal of the FPV system? I fly away from the tower on my sorties.

3. Lastly, when I flew yesterday, I lost all my control outputs, including throttle. Good thing the Skywalker is a floater and it glided gently to the ground. I inspected the receiver and the leds were not blinking so there was no brownout. Strange but can the 900mhz system cause this phenomenon?

Thanks a lot!

Gent
gent96 is offline Find More Posts by gent96
Reply With Quote
Old Aug 22, 2011, 02:44 PM
Rocket Programmer
jasmine2501's Avatar
United States, AZ, Mesa
Joined Jul 2007
25,354 Posts
Quote:
Originally Posted by IBCrazy View Post
You are likely correct here. The filters within an RX do not have perfectly sharp cut off points, but are actually curved. Chances are they are Chebyshev types (as opposed to Butterworth or Sallen-key) and thus there are going to be some oscillations in the filtration scheme over the cut off band frequencies. The strength (also known as order) of this filter determines how much out of band noise it can filter out. Thus you can knock out a 2.4 GHz system with a 72 MHz system if the 72MHz is close and powerful enough despite having incredible separation.

I have found that Spektrum systems have poor filtration and that's probably why most people have issues with them for FPV.

-Alex
Heck yeah they do - it's easy to swamp the park flyer receivers. The high-end receivers are a lot better though. So, you think it's the components? It makes sense that they would use cheaper components in the cheaper receivers.

Engineers never try to make a product perfect - they try to find a good balance of functional reliability and cost. The park receivers could be more reliable, but if they cost $100, would anybody use them?
jasmine2501 is offline Find More Posts by jasmine2501
Reply With Quote
Old Aug 22, 2011, 02:53 PM
Village Idiot!
ScooterInVegas's Avatar
United States, NV, Las Vegas
Joined Apr 2011
1,932 Posts
What kind of camera and how close is it to the Rx. 900mhz 1/4 1/2 waves is not close to 2.4, so I would guess thats not the problem.

My one guess would be a noisy camera too close to the Rx, but that is just a guess.
ScooterInVegas is offline Find More Posts by ScooterInVegas
Reply With Quote
Old Aug 22, 2011, 05:51 PM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
10,301 Posts
Quote:
Originally Posted by gent96 View Post
To Alex (IBCrazy),

Hi!. Noob here. I have a Skywalker with with an AR7000 RX. I bought a 500mw 900mhz FPV system from ReadymadeRC and mounted the video RX on the flat section on the Sw's tail. I also bought one of your Vee antennas from RMC and installed it on a flat stick protruding from the SW's tail just behind the RX. I also have a low pass filter between the Video TX and the Antenna. I mounted the video camera on the top section of the SW with a servo for panning. When I tested the the system, I could only make some 500 to 700 yds range estimate on the FPV before the signal becomes scratchy then I have to turn back. It is to note that I fly with an 8dBi patch antenna oriented about 35-45 deg, 6 inches from the ground. I fly on an open farm land with a cell tower about a mile away. My questions:

1. Does my placement of the vid TX affecting its range? I placed my RC receiver inside the fuselage. I also wound up the servo wires, even the video/ audio cables, with ferrite rings. Is it better to mount the video tx and antenna on a wing rather than the tail?

2. Does the cell site tower also affect the transmission of 900mhz signal of the FPV system? I fly away from the tower on my sorties.

3. Lastly, when I flew yesterday, I lost all my control outputs, including throttle. Good thing the Skywalker is a floater and it glided gently to the ground. I inspected the receiver and the leds were not blinking so there was no brownout. Strange but can the 900mhz system cause this phenomenon?

Thanks a lot!

Gent
Answers:

1. Mounting on the wing would help. so would mounting it on the BOTTOM of the tail as close to the ground as possible. The wing would be better, though.

2. Absolutely. Chances are that's your biggest problem.

3. Just because the RX didn't specify a brown out doesn't mean it didn't happen. If you lost all control, you lost signal. Any VTX can have that effect if it is close to the RX.

-Alex
IBCrazy is offline Find More Posts by IBCrazy
RCG Plus Member
Old Aug 22, 2011, 06:02 PM
Rocket Programmer
jasmine2501's Avatar
United States, AZ, Mesa
Joined Jul 2007
25,354 Posts
Signal loss and brown-out are not the same thing. The "blinking indication" of the Spek receivers indicates a brown-out, NOT a signal loss. To detect signal losses, you need the data log reader, and a high-end RX which logs the data. Many people confuse these situations and that is part of the reason why "on the internet" Spek brown-outs look like a much bigger problem than they are - because almost any problem anybody ever has with the system, they call it a brown-out. It's a fairly specific term, meaning a significant loss of power, but not total loss of power. One of my friends recently flew his plane up to the LVC, and had to land because the motor wouldn't run any more - when he posted the video, he put "Spektrum Brown-out" in the video title. So, this situation is very commonly misunderstood.
jasmine2501 is offline Find More Posts by jasmine2501
Last edited by jasmine2501; Aug 22, 2011 at 06:08 PM.
Reply With Quote
Old Aug 22, 2011, 06:11 PM
OSUFPV - KF7VFT
Corvallis, OR
Joined Apr 2010
1,741 Posts
Quote:
Originally Posted by jasmine2501 View Post
... they call it a brown-out. It's a fairly specific term, meaning a significant loss of power, but not total loss of power.
Well people may be referring to the other phenomenon where their pants turn brown. Hence "brown out".....
Blueshy is offline Find More Posts by Blueshy
Reply With Quote
Old Aug 22, 2011, 07:18 PM
QiW
Registered User
south east asia
Joined Mar 2009
956 Posts
i was once a dsm2/spektrum user with ar7000 ar6250 and ar6100 receivers
now i am a fasst/futaba user .. guess why
i have done 3.5km with stock futaba 2.4 fasst (seems like thats as far as it will go in stock form with 500mW 1.2 vtx on board)
QiW is offline Find More Posts by QiW
Reply With Quote
Old Aug 22, 2011, 07:19 PM
3DHS Trunk-monkey
FireFighterFSF's Avatar
Joined Oct 2007
407 Posts
ok guys well I am thinking of getting a fpv set up and was wondering what the best bundle package was these days. I really dont want to have the cheapest thing out there where you cant tell what your looking at and the signal goes in and out all the time but something that has a nice clear picture, good range, and a great set up to have for a long time that can be upgraded. I live up on a hill over looking the farm I grew up on and can see my dads cows and such out there and thought it would be neat to have a good set up to sit out on the deck and "go for a flight" any suggestions?
FireFighterFSF is offline Find More Posts by FireFighterFSF
Site Sponsor
Reply With Quote
Old Aug 22, 2011, 07:49 PM
Village Idiot!
ScooterInVegas's Avatar
United States, NV, Las Vegas
Joined Apr 2011
1,932 Posts
There is no "best" set-up. Thats like asking what is the best truck to buy or the best Football team.

It would depend on what country you live in and the type of radio you plan to use for starters.
ScooterInVegas is offline Find More Posts by ScooterInVegas
Last edited by ScooterInVegas; Aug 22, 2011 at 08:19 PM.
Reply With Quote
Old Aug 22, 2011, 08:05 PM
Rocket Programmer
jasmine2501's Avatar
United States, AZ, Mesa
Joined Jul 2007
25,354 Posts
Quote:
Originally Posted by QiW View Post
now i am a fasst/futaba user .. guess why
Either... because you want to spam the entire band with impunity... or, you bought into the myth that Futaba receivers will run fine without power...
jasmine2501 is offline Find More Posts by jasmine2501
Reply With Quote
Old Aug 22, 2011, 08:06 PM
Village Idiot!
ScooterInVegas's Avatar
United States, NV, Las Vegas
Joined Apr 2011
1,932 Posts
Quote:
Originally Posted by jasmine2501 View Post
Either... because you want to spam the entire band with impunity... or, you bought into the myth that Futaba receivers will run fine without power...
I think Futaba Rx's are solar powered.
ScooterInVegas is offline Find More Posts by ScooterInVegas
Reply With Quote
Old Aug 22, 2011, 08:09 PM
Team Basement-RC
Tracks's Avatar
Canada, ON, Toronto
Joined Jan 2011
1,951 Posts
Quote:
Originally Posted by ScooterInVegas View Post
I think Futaba Rx's are solar powered.
They can also be recharged with orphan tears.
Tracks is offline Find More Posts by Tracks
Reply With Quote
Old Aug 22, 2011, 08:19 PM
Village Idiot!
ScooterInVegas's Avatar
United States, NV, Las Vegas
Joined Apr 2011
1,932 Posts
Quote:
Originally Posted by Tracks View Post
They can also be recharged with orphan tears.
That makes since, there are lots of those around if you own Futaba gear.
ScooterInVegas is offline Find More Posts by ScooterInVegas
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Discussion How to calculate flight time - guide ikorman Multirotor Talk 11 Dec 30, 2011 07:22 PM
Discussion How many FPV pilots in the world? rbmaze FPV Talk 10 Aug 03, 2011 06:16 AM
Poll Would you be interested in buying Ready to Fly FPV airplanes from a new FPV store? FPVNOW FPV Aircraft 36 Oct 06, 2010 08:56 PM
Discussion Can this cam be used for FPV ? SpookiePower FPV Talk 8 Sep 12, 2010 07:12 AM
Cool How cool would this be for FPV Kai_Shiden FPV Talk 2 May 11, 2009 07:41 PM