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Old Jan 17, 2013, 11:53 AM
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This is an interesting conversation. If the power of the TX is known, along with the sensitivity of the RX, is it possible to calculate the rough range (assuming there is no outside noise, ect.)? I'd like to compare the Berg 7P (sensitivity 1.2uV) and the Corona synthesized RX (sensitivity 2uV). Maybe it's only practical to compare the range relative to one another (i.e. Corona will get approximately twice the range of the Berg).
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Old Jan 17, 2013, 12:12 PM
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Originally Posted by IBCrazy View Post
^You'd think so, but in reality the RX is far more important. Remember that in order to double your range you need 4X more power. Generally our radio systems are confined to a very small range of power outputs and therefore the difference in power has little effect on the ultimate range.

Just an example of what a good RX can do: I once made a 4000 foot flight on 125uW (yes 0.000125W) transmit power. Video was great the whole way. I even ducked behind a row of trees (video wasn't so great when I did that).

-Alex
Ah yes... The darn inverse square law...
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Old Jan 17, 2013, 02:19 PM
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Originally Posted by PiperCub49 View Post
This is an interesting conversation. If the power of the TX is known, along with the sensitivity of the RX, is it possible to calculate the rough range (assuming there is no outside noise, ect.)? I'd like to compare the Berg 7P (sensitivity 1.2uV) and the Corona synthesized RX (sensitivity 2uV). Maybe it's only practical to compare the range relative to one another (i.e. Corona will get approximately twice the range of the Berg).
There are environmental effects that will attenuate the signal such as humidity, but short and simple and relatively accurate answer is "yes".

-Alex
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Old Jan 17, 2013, 02:21 PM
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Originally Posted by williamjames View Post
Here's a question regarding the LC filter:

(a) Does it matter if I wrap my power wire and ground wire around the same toroid or two different ones? Will any yield better filtering?

(b) If I put two torroids together and wrap my wires around it as to treat it like it is one torroid, would that in any way help or hinder the the performance of the LC filter?

Thanks
a. Two toroids is better as there will be no mutual coupling between them. However, with enough wraps, it is really irrelevant.

b. Technically yes, but why bother?
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Old Jan 17, 2013, 04:37 PM
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Originally Posted by PiperCub49 View Post
This is an interesting conversation. If the power of the TX is known, along with the sensitivity of the RX, is it possible to calculate the rough range (assuming there is no outside noise, ect.)? I'd like to compare the Berg 7P (sensitivity 1.2uV) and the Corona synthesized RX (sensitivity 2uV). Maybe it's only practical to compare the range relative to one another (i.e. Corona will get approximately twice the range of the Berg).
You could have a look here, it gives you a theoretical upper bound:

http://en.wikipedia.org/wiki/Friis_t...ssion_equation

See also the online calculators at the bottom.

Martin
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Old Jan 17, 2013, 05:41 PM
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You could have a look here, it gives you a theoretical upper bound:

http://en.wikipedia.org/wiki/Friis_t...ssion_equation

See also the online calculators at the bottom.

Martin
Thanks. I wish I had the means of finding the quantities of these variables. I might be able to calculate the approximate gain of each antenna, but I can't find the power of my 9C.
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Old Jan 17, 2013, 07:33 PM
Firepower
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I have several flying wings and used to put the two antennas for my Futaba 9C (FrSky Module) on the bottom of the wings at right angles.

I am FPVing the wings and thought more range could be obtained if I put one antenna vertical and the other one near the winglet at right angles. I buy the longer antennas to get them near the winglet.

The antennas now come with a balun near the end so harder to mount in a tube. Someone has said the balun gives almost twice the range.

The vertical one in the photo is in the pink tube without the balun.

So not sure if the vertical antenna makes any difference but I think it would?
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Old Jan 18, 2013, 05:27 AM
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Hey guys, which push rod and clevis do you guys recommend from hobbyking? I'd like something sturdy with not too much flex in the push rod.
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Old Jan 18, 2013, 09:26 AM
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Originally Posted by Firepower View Post
I have several flying wings and used to put the two antennas for my Futaba 9C (FrSky Module) on the bottom of the wings at right angles.

I am FPVing the wings and thought more range could be obtained if I put one antenna vertical and the other one near the winglet at right angles. I buy the longer antennas to get them near the winglet.

The antennas now come with a balun near the end so harder to mount in a tube. Someone has said the balun gives almost twice the range.

The vertical one in the photo is in the pink tube without the balun.

So not sure if the vertical antenna makes any difference but I think it would?
Yes, keep it vertical.
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Old Jan 18, 2013, 09:28 AM
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Hey guys, which push rod and clevis do you guys recommend from hobbyking? I'd like something sturdy with not too much flex in the push rod.
I buy 2-56 fully threaded rod from Tower Hobbies and the Great Planes or Du-Bro clevises. These are stiff, cheap, and easy to make and adjust.

-Alex
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Old Jan 18, 2013, 09:48 AM
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I buy 2-56 fully threaded rod from Tower Hobbies and the Great Planes or Du-Bro clevises. These are stiff, cheap, and easy to make and adjust.

-Alex
Ditto on the Du-Bro. I use some of their stuff on a 100cc yak.
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Old Jan 18, 2013, 12:19 PM
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Joined Oct 2005
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fpv stuff

Hey just getting ready to pull the triger on fpv how does this line up look?
I would stay close till I got it down then go farther as I get better thinking if I has a kick ass set up I wouldn't have to upgrade I've been flying for 10 yrs so there's no problem there just learning to fly in a screen
Custom 1.3 FPV Starter Package: 1258/1280MHz US Version
Plane- penguin
Camera - None GOPRO
Video Transmitter - 1.3GHz 800mW
Video Receiver - 1.3GHz "Tan" Custom Ready Made RC Version with SAW Upgrade
TX Antenna - Cloverleaf Whip Circular Polarized OR SHOULD I USE THE MAD MUSHROOM ???
RX Antenna - Skew Planar Wheel Whip Circular Polarized
Video Goggles or Monitor - None I have a 19' tv was going to use but do more people like Goggles??
Batteries - None HAVE
OSD - ImmersionRC EZOSD

with above set up what sorta distance would I be looking at in wide open area?

I was thinking of a diversity box,what do you think do I really need one??
Oracle Video Diversity Controller

Extra Reciver

And this as my 2nd Antenna 1.3 GHz 10dBic RHCP Crosshair Antenna (IBCrazy) setting up on a ground Station (TRIPOD)

I'm some what new I have learned a lot frying my Brain LOL just tring to put it together. and oh yea the 433 dragonlink

I have a old Hitec Eclips 7 FM Radio I was going to Drangonlink with,but How far could I get with FM? Do you recommend the Dragonlink
or use FM for now?

or should I go with 2 RX antennas the same (1.3 GHz 10dBic RHCP Crosshair Antenna (IBCrazy) and have 180 degrees of flying I prob wont be flying to much behind myslef
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Old Jan 18, 2013, 02:12 PM
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Bussum, Netherlands
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Originally Posted by PiperCub49 View Post
Thanks. I wish I had the means of finding the quantities of these variables. I might be able to calculate the approximate gain of each antenna, but I can't find the power of my 9C.
The Friis equation gives you a too optimistic number. But comparing your receivers shouldn't be too hard. Let me try it:
Berg 7P: 1.2μV => power@50Ω input = 1.2E-6 * 1.2E-6 / 50 = 28.8fW = -105dBm
Corona: 2μV => power@50Ω input = 2E-6 * 2E-6 / 50 = 80fW = -101dBm

The Berg is 4dBs better so that's about 50% more range.

Martin
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Old Jan 18, 2013, 02:53 PM
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Well.. i will try a new aproach to my random glitches issue..

Until now i was using "3-switch mode" in IkarusOSD , that mode uses a 3-way switch , the center is the neutral position, you flip it and back to neutral in one way and it will switch between the 4 diferent HUDs, you flip it into the other position and will change destionation for the autopilot between HOME and HOLD (hold position will make the autopilot fly straight.. HOME will obviously return home, there is also the option of follow waypoints, wich i dont use yet). And you let the switch in any one of the 2 outter positions and will enable autopilot.

My problem is that randomly (well, seemed to be located in some points in space) i get my screens switched and autopilot modes switched too without input of my part.. it was at the same time as i could observ light jitter (sometimes heavy jitter) in the PAN servo..

as you can see here:

FPV Escuela test 4 Glitches y 950m Ikarus OSD (8 min 55 sec)



so it was something that affected all radio chanels, seemed something too quick wich wouldnt affect the controls much, but enought to make an input in the OSD... apart from the anoyment of having your HUD changed there was a small risk of waypoint selection and autopilot activation..

The option i will try is to use the "basic 3-switch mode" , it uses a 3-way switch too but diferently.. you can use only one screen and cant select the autopilot destination (it will allways return home or if you wish follow route IF there is one programmed) the 3 way switch only manages the autopilot, position 1 is manual (you have full control) , pos 2 is STAB mode, (OSD stabilizes the plane and you still have control, like an asisted mode) and pos 3 is full autopilot.

The advantage here is that the switch must be in the exact position to work.. to have the autopilot it must be constantly in position 3, to be in stab mode it must be in 2.. and so .. so quick glitches will never engage the autopilot... not more than half second anyway, since the radio is broadcasting, if it has link it will obey the radio , save for those glitches, and if it looses link it will go into FAILSAFE mode and enable RTH..


Will see how that works out
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Old Jan 18, 2013, 06:43 PM
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Originally Posted by Martin. View Post
The Friis equation gives you a too optimistic number. But comparing your receivers shouldn't be too hard. Let me try it:
Berg 7P: 1.2μV => power@50Ω input = 1.2E-6 * 1.2E-6 / 50 = 28.8fW = -105dBm
Corona: 2μV => power@50Ω input = 2E-6 * 2E-6 / 50 = 80fW = -101dBm

The Berg is 4dBs better so that's about 50% more range.

Martin
Thank you so much!
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