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Old Oct 16, 2012, 09:29 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
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Quote:
Originally Posted by TheNiceGuy View Post
How exactly is this UHF system better than PCM1024 72mhz? I understand the claims of better range and stability, but no idea the science behind it. Why is the PCM system inferior within 2km for a multirotor?
You get 2km with a 72Mhz antenna on a multi-rotor? Not if you don't dangle
it straight below, risking catching it on vegetation or in the props.

ian
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Old Oct 16, 2012, 09:32 PM
Just FPV'n
Orange County Ca.
Joined Feb 2009
567 Posts
Quote:
Originally Posted by caall99 View Post
what type of deal is that?
Oh sorry... I should have said "Featured Product" http://www.rangepiloting.com/rangeli...rxs-p-186.html

Sorry for the confusion..
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Old Oct 17, 2012, 01:21 AM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,316 Posts
Quote:
Originally Posted by Daemon View Post
Move things around until you get the results you want.
Sometimes repositioning the antenna is enough. Sometimes it's not.
Always *start* by doing a baseline micro-power range test with just the Tx and Rx powered
by a battery (like 4cell NiMh).
Then start introducing other components and repeat the test. If the range is reduced
then move things around until it isn't. If moving it around doesn't work, then you may
have to eliminate that component. Some cameras, switching regulators, current
sensors, etc are Rf noisy in the 433Mhz band. Some aren't. Some are *very* noisy.
and some only a little. The only person who can make it work optimally on your
plane, is you.

ian
Thanks Ian, I suspect it's my FPV camera, but I need to make an extension cable for the antenna, but I don't want to go through the effort (and possible db loss) if it turns out I need to move the whole thing.
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Old Oct 17, 2012, 05:54 AM
Expat
Japan
Joined Apr 2010
3,010 Posts
Quote:
Originally Posted by Daemon View Post
You get 2km with a 72Mhz antenna on a multi-rotor? Not if you don't dangle
it straight below, risking catching it on vegetation or in the props.

ian
I would be happy with 1km stable range on my tri with 72mhz. I had my old corona 72mhz synth tri setup out almost that far once during testing.
I came up with a 72mhz antenna solution I was very happy with. A chloroplast 3 section spring loaded antenna holder, very quick to break down and allows full 3' length during flight. Almost no flex and most of the weight in the base. 15g with all the mounting hardware.
I'm still not certain what caused the crash, and am sure pcm1024 is better than a corona synth.
I just want to know if 72mhz is truly a lost cause for a 1km range tricopter.
To be honest I don't understand the science behind wether its a fail or win for this aplication.
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Old Oct 17, 2012, 06:07 AM
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snelan's Avatar
Joined Jul 2012
413 Posts
Quote:
Originally Posted by Daemon View Post
Tx antenna problem (any antenna problem) would result in failsafes, not random rudder glitches.
I assume your saved failsafe position is not set to left rudder.
As you say, sounds like a servo issue.

ian
Failsafe is set to 50% throttle and RTH. It's just weird that this started with the 433MHz. No problems at all with 72MHz.

Also, to confirm your theory, I still have full control of the rest of the plane, and if I put the rudder stick all the way to the right it still moves the rudder closer to center, but is still sideways a bit. So it's not like it's just locked up off to the side.
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Old Oct 17, 2012, 07:52 AM
Crash=start of next project
CN I Dawg's Avatar
United States, CA, Los Angeles
Joined Nov 2010
659 Posts
Quote:
Originally Posted by snelan View Post
Failsafe is set to 50% throttle and RTH. It's just weird that this started with the 433MHz. No problems at all with 72MHz.

Also, to confirm your theory, I still have full control of the rest of the plane, and if I put the rudder stick all the way to the right it still moves the rudder closer to center, but is still sideways a bit. So it's not like it's just locked up off to the side.
It's easy to check if it's the servo. Assuming you have easy access to the Rx, unplug the rudder servo and plug a known good one in its place. If the operation is normal, it's the servo. If not, check the "soft trims" on your Tx. You may have inadvertently adjusted the rudder servo trims.
Best,
Steven
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Old Oct 17, 2012, 12:27 PM
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Joined Jul 2012
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Quote:
Originally Posted by CN I Dawg View Post
It's easy to check if it's the servo. Assuming you have easy access to the Rx, unplug the rudder servo and plug a known good one in its place. If the operation is normal, it's the servo. If not, check the "soft trims" on your Tx. You may have inadvertently adjusted the rudder servo trims.
Best,
Steven
Well it only happens intermittently, maybe once every three flights, so it would take a very long time to test if it was the servo, and I could never be certain.
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Old Oct 18, 2012, 07:41 AM
Crash=start of next project
CN I Dawg's Avatar
United States, CA, Los Angeles
Joined Nov 2010
659 Posts
Sorry I misread, "Still getting my rudder locking to the left mid flight, whether I am far away or close by, high or low power." and the post above, where you said the servo was "off center". In that case, it's the servo and for sure not the RL.

Quote:
Originally Posted by snelan View Post
Well it only happens intermittently, maybe once every three flights, so it would take a very long time to test if it was the servo, and I could never be certain.
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Old Oct 18, 2012, 12:28 PM
Registered User
Joined May 2012
1 Posts
hi,

I have this video system: vtx 1.2 sunsky 800mw and vrx lawmate standard.. both with SWP by sircana

now.. on my rangelink tx I put this filter:
http://www.bevrc.com/band-pass-filte...tter_p275.html

it's ok ?

thanks a lot
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Old Oct 18, 2012, 03:35 PM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,316 Posts
How do I know which part of the rx antenna is ground (dangling bit) and which is live (straight bit)?

Or should I just do a V like some do particularly on the X8?
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Old Oct 18, 2012, 03:38 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
28,219 Posts
Active bit is heading out the end.
Ground is soldered to the coax shield headed the other way.

ian
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Old Oct 18, 2012, 03:41 PM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,316 Posts
Quote:
Originally Posted by Daemon View Post
Active bit is heading out the end.
Ground is soldered to the coax shield headed the other way.

ian
Thanks Ian, what would rcgroups be without you
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Old Oct 18, 2012, 03:46 PM
Power-line attraction pilot
United States, MA, Natick
Joined Jun 2011
517 Posts
i read something about dipole antennas like this functioning best if the feed (shield and active) is perpendicular to the two legs of the dipole. Forming a T, vs Rangelink's J.
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Old Oct 18, 2012, 04:54 PM
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Daemon's Avatar
Lakewood, Colorado
Joined Aug 2002
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While that is true to a certain degree, a lot of UHF Rx antennas are made this way
to provide an adequate level of durability and ease of installation (easier to run through
a small hole). It's pretty easy to break off the elements
soldered onto a coax cable if they're coming off at right angles unless you mount
everything to something like a bit of circuit board (see IBCrazy's own Vees).
Generally though what you want to avoid is running the ground element against the
coax or even parallel to it for any significant fraction of its length. What that means is I
usually try to put the active and ground elements in line with each other (usually
oriented vertically) and then curve the coax cable away from the ground element fairly quickly.
This is the orientation I've used on my 30+ mile ground range tests with both RL And DL.

ian
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Old Oct 19, 2012, 11:31 AM
Foam Snow
South Africa, WC, Cape Town
Joined Aug 2011
1,316 Posts
Ignore...RTFM
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Last edited by heinduplessis; Oct 19, 2012 at 01:17 PM.
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