Espritmodel.com Telemetry Radio
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Old Nov 26, 2011, 01:00 AM
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Originally Posted by hartwig View Post
Pls specify the exact altitude level.
Of course the result you get also depends on the area. I am referring to a flat surface, no hills or valleys between launch site and aircraft. One of my tests got me out past >3.2km at <20m AGL with me standing on the ground. Video link was on 2.4GHz and the RC on 433MHz.
Since there was no Fresnel Clearance fpr the RC link, this was the link that got affected first.
At 10km I was able to fly at 12 meters altitude, this is over flat ground, according to google earth there is a 5 meter altitude difference so in theory if I was flying 2.4 ghz video I would be able to fly lower?

Mark
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Old Nov 26, 2011, 04:38 AM
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I'm switching from 900 Mhz to 5.8 Ghz and just finish installing my ground station that consists of 2 receivers, 1 diversity, 1 CL antenna, 1 9 turn helix antenna, 1 19" monitor and 1 video recorder.

Here are 2 photos of the station:





The CL antenna is a tad lower than the helix, will that affect video reception in any ways?

Thanks.
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Old Nov 26, 2011, 10:04 AM
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Originally Posted by lrrps View Post
I'm switching from 900 Mhz to 5.8 Ghz and just finish installing my ground station that consists of 2 receivers, 1 diversity, 1 CL antenna, 1 9 turn helix antenna, 1 19" monitor and 1 video recorder.

Here are 2 photos of the station:





The CL antenna is a tad lower than the helix, will that affect video reception in any ways?

Thanks.
Gaston,

Get a wooden stick of about 1m length, get another of about 50 cm. Make a T shape with them and place that on top of your tripod. That way you gain another meter in height above ground.

Then, mount the SPW on one side fo the T boom, the helix to the other. Please note, the helix is a directional antenna, so you have to mount it horizontally oriented, not vertical as it seems to be when looking at your picture (I could be wrong here but just in case).

You then point the helical into the direction you intend to fly out and by using diversity this is a great setup.

Markus
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Old Nov 26, 2011, 11:19 AM
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Markus,
The reason I mounted the helix antenna vertically is to cover the area when the plane flies overhead, as I don't intend to fly far there's no need to point the helix towards the plane, that's what I think.
I did a flight this afternoon with the same setup you see on the pics, well it was a nightmare because the video was crappy as hell, at times I can't see a thing, will post the video when I get it uploaded on Youtube.
I had a lot better video on 900Mhz with the RV Vee antenna on the plane, 2 receivers connected to the RV Oracle diversity, one stock antenna on a receiver and a patch antenna pointing at 90 on the otner receiver.
To be honest this is the first time I fly FPV with plenty of other planes in the air, could it be interferences from other radios?
Usually I fly around 20 mn but this time I cut it short to 10 mn, 'cuz other than the video problem it was hard to concentrate while people are talking around me, noise from gas helis and a turbine heli added to the fun so to speak.
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Old Nov 26, 2011, 11:22 AM
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Originally Posted by lrrps View Post
Markus,
The reason I mounted the helix antenna vertically is to cover the area when the plane flies overhead, as I don't intend to fly far there's no need to point the helix towards the plane, that's what I think.
I did a flight this afternoon with the same setup you see on the pics, well it was a nightmare because the video was crappy as hell, at times I can't see a thing, will post the video when I get it uploaded on Youtube.
I had a lot better video on 900Mhz with the RV Vee antenna on the plane, 2 receivers connected to the RV Oracle diversity, one stock antenna on a receiver and a patch antenna pointing at 90 on the otner receiver.
To be honest this is the first time I fly FPV with plenty of other planes in the air, could it be interferences from other radios?
Usually I fly around 20 mn but this time I cut it short to 10 mn, 'cuz other than the video problem it was hard to concentrate while people are talking around me, noise from gas helis and a turbine heli added to the fun so to speak.
Ok, I understand now better.

Still, move the antennas more apart, and also make sure to raise it above the metal plate of the tripod. The "T" thing still would be good, this time pointing the helical up though as this then means to point it towards your plane.

What exactly are you doing? Rockets? Maybe you don't even need the diversity then as the SPW is haveing a dead spot right on top of it.

Markus
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Old Nov 26, 2011, 11:35 AM
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Originally Posted by markus123456 View Post
Ok, I understand now better.

Still, move the antennas more apart, and also make sure to raise it above the metal plate of the tripod. The "T" thing still would be good, this time pointing the helical up though as this then means to point it towards your plane.

What exactly are you doing? Rockets? Maybe you don't even need the diversity then as the SPW is haveing a dead spot right on top of it.

Markus
No I'm not doing rockets, not yet, I fly a Skywalker.
Because of the dead spot right on top of the SPW, I need the diversity to switch to the 90 pointing helix to cover that dead spot, i'm I right?
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Old Nov 26, 2011, 04:26 PM
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I really haven't been able to find my Cloverleaf's dead spot yet. Here's a bit of speculation since I don't have a SPW nor have I flown REALLY high right over my CL. But: I fly right over myself all the time and haven't bean able to find that null. I've flown high enough that the plane was only a dot, and had solid reception. Just a thought.
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Old Nov 26, 2011, 08:24 PM
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Originally Posted by lrrps View Post
No I'm not doing rockets, not yet, I fly a Skywalker.
Because of the dead spot right on top of the SPW, I need the diversity to switch to the 90 pointing helix to cover that dead spot, i'm I right?
Aiming a helix straight up is good if you have a 3 turn. Aiming a 9 turn straight up is useless. By the time the diversity switches you will already be out of the beam. It is quite narrow.

-Alex
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Old Nov 26, 2011, 10:46 PM
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wrong thread, sorry




reposted here
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Last edited by m_beeson; Nov 26, 2011 at 10:51 PM.
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Old Nov 26, 2011, 11:56 PM
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Originally Posted by IBCrazy View Post
Aiming a helix straight up is good if you have a 3 turn. Aiming a 9 turn straight up is useless. By the time the diversity switches you will already be out of the beam. It is quite narrow.

-Alex
When I ground tested my setup by removing the RSSI cable from a receiver, the switching was instantanious, I didn't see any cut in the video, is that what you mean?
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Old Nov 27, 2011, 05:03 AM
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Originally Posted by lrrps View Post
No I'm not doing rockets, not yet, I fly a Skywalker.
Because of the dead spot right on top of the SPW, I need the diversity to switch to the 90 pointing helix to cover that dead spot, i'm I right?
When looking at the video I see two problems.

Number one is the noise in your power trail. You mentioned to use a DC/DC converter which seems to introduce a lot of noise. You have to add a very good low pass filter into your power train before the camera and transmitter or considering the space you have in your Skywalker, add a dedicated 3s battery for the cam and video tx.

The other problem is IMHO the way you mount your CL. If your target is truly to fly directly above you and as high as possible, your CL will operate in it's dead spot. One aproach for this very special application could be to mount it sideways. You would have to make some ground range tests though and eventually restrict yourself to fly in one circle around you so as the CL does not get covered by the fuselage etc.

I wonder if it would not be better for you to fly out and high instead of trying to fly as high as possible directly above you.

The -3dB spot of your helical is about 30 degrees. You can use the tangens function to calculate the beam with it is having in a certain height above you. I tested this very helix you are using here and I could not drive out further than 15km due to the landscape here but till 15km the picture was rock solid. I think your diversity aproach is ok as the CL/SPW could be used while you are close, and then the helical should kick in. Note though, you should have someone beside you to observe the diversity. The RV diversity you are using is pretty tricky to be adjusted to switch propperly. So I would start out with some experiemnts first and assure your diversity works as intened before you try to fly to the altitude you want.

Markus
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Old Nov 28, 2011, 01:38 AM
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Markus,
I forgot to mention that there was already an L filter (round core around which the wires are wrapped) on the previous VTX installation, when I fit the new 5.8Ghz VTX I added a second L filter, does this double filtering negate the benefit of the noise filtering and induce interferences to the video?
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Old Nov 28, 2011, 01:58 AM
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Originally Posted by lrrps View Post
Markus,
I forgot to mention that there was already an L filter (round core around which the wires are wrapped) on the previous VTX installation, when I fit the new 5.8Ghz VTX I added a second L filter, does this double filtering negate the benefit of the noise filtering and induce interferences to the video?
Provided I understand you correctly - no, but it seems like the filter(s) are then simply not good enough or they filter not low enough.

Filtering can be difficult at times. I had to go throuhg several design cycles with my 5.8Ghz video transmitter project to get it right, and based on my experience simple filters do not cut it. That's why I recommend you the battery aproach and if it's only to proof that part of the problem (the wide horizontal banding visible when the motor runs) has it's source there. If you see that this problem is gone, feel free to send me a mail and I will see if I can make a filter for you so as you only need one battery.

Markus
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Old Nov 28, 2011, 02:21 AM
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Originally Posted by markus123456 View Post
Provided I understand you correctly - no, but it seems like the filter(s) are then simply not good enough or they filter not low enough.

Filtering can be difficult at times. I had to go throuhg several design cycles with my 5.8Ghz video transmitter project to get it right, and based on my experience simple filters do not cut it. That's why I recommend you the battery aproach and if it's only to proof that part of the problem (the wide horizontal banding visible when the motor runs) has it's source there. If you see that this problem is gone, feel free to send me a mail and I will see if I can make a filter for you so as you only need one battery.

Markus
Markus,

Though the SW can handle big loads, the addition of a 3S lipo on top of the 4S pack will interfere with the UBEC mounted under the front cover.
What I will do to make sure the problem comes from the main pack is to temporarily relocate the UBEC and install a second lipo dedicated to the VTX, FPV cam and Range Video OSD.
If the problem disappears which I hope, your special filter is greatly appreciated.
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Old Nov 28, 2011, 04:15 AM
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Originally Posted by lrrps View Post
Markus,

Though the SW can handle big loads, the addition of a 3S lipo on top of the 4S pack will interfere with the UBEC mounted under the front cover.
What I will do to make sure the problem comes from the main pack is to temporarily relocate the UBEC and install a second lipo dedicated to the VTX, FPV cam and Range Video OSD.
If the problem disappears which I hope, your special filter is greatly appreciated.
Fine, just let me know how things are going.

Markus
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