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Old Nov 18, 2012, 05:16 PM
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Originally Posted by Flybynight2 View Post
My first try was a 5 amp. UBEC, but it didn't seem to work. Even though the load didn't seem to be that much.
I replaced with a 10 amp, and now everthing works.
Ok but how were you able to calculate how many amps you needed?
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Old Nov 18, 2012, 05:58 PM
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Originally Posted by Cid156 View Post
Today I did my first fly in fpv with my quad... It was a nightmare!!! I crashed badly...
Not because of a fpv equipement failures but because of my flying skill...

I expected that flying the quad in fpv was much more easy than the normal... bad mistake...

I need first to improve my skill in normal flying... or buy a better quad :b
sorry to hear but flying FPV is way harder than normal RCing..
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Old Nov 20, 2012, 03:24 PM
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Originally Posted by ror1 View Post
sorry to hear but flying FPV is way harder than normal RCing..
I think this is true in some respects but for the most part I find FPV easier, mainly because i never lose orientation. I'm flying multis and the takeoff and landings were a little scary at first, but now I prefer FPV and only fly LOS to check things out. here's my latest outting this weekend.

BTW: I'm wanting a new video Rx antenna. I'm currently running 1280 MHz with diversity with a SPW and a stock whip on the GS, CL on the Tx. I want a circularly polarized, directional antenna to replace the whip. Would you recommend a helical or a bi-quad or other?

New Park Adventures (3 min 30 sec)
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Old Nov 20, 2012, 03:52 PM
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Originally Posted by Cervanchez View Post
I think this is true in some respects but for the most part I find FPV easier, mainly because i never lose orientation. I'm flying multis and the takeoff and landings were a little scary at first, but now I prefer FPV and only fly LOS to check things out. here's my latest outting this weekend.

BTW: I'm wanting a new video Rx antenna. I'm currently running 1280 MHz with diversity with a SPW and a stock whip on the GS, CL on the Tx. I want a circularly polarized, directional antenna to replace the whip. Would you recommend a helical or a bi-quad or other?

https://www.youtube.com/watch?v=8iFw...e_gdata_player
Mixing linear and circular polarized antennas in a diversity setup does not make too much sense IMHO. At this frequency you may make good experiance with pure linear antennas, obviousely CP antennas have their advantages too. If I were you, I would decide for one of the two sides and further invest there. I'm not too much convinced that a diversity helps you much in the CP realm, except maybe to combine two directional antennas pointing such apart from eachother to extend the horizontal coverage. So, since you already have a diversity. i.e. combineing two 3 turn helicals could be a winner.

HTH

Markus
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Old Nov 20, 2012, 03:52 PM
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Originally Posted by williamjames View Post
Ok but how were you able to calculate how many amps you needed?
Just add up all the things that take 5 volts.
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Old Nov 20, 2012, 05:05 PM
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Originally Posted by markus123456 View Post
Mixing linear and circular polarized antennas in a diversity setup does not make too much sense IMHO. At this frequency you may make good experiance with pure linear antennas, obviousely CP antennas have their advantages too. If I were you, I would decide for one of the two sides and further invest there. I'm not too much convinced that a diversity helps you much in the CP realm, except maybe to combine two directional antennas pointing such apart from eachother to extend the horizontal coverage. So, since you already have a diversity. i.e. combineing two 3 turn helicals could be a winner.

HTH

Markus
I was only using the linear whip for lack of anything else. My plan was to go all cp since most of my flying is in urban areas, and I wanted the multipath rejection. So, I was trying to decide on which directional cp antenna to supplement the SPW. The plan was to have the directional pointed in the direction I want to go for any distance, and have the SPW omni coverage for around and behind me. I was leaning towards the 3 turn helical, so maybe I'll start with one of those, and maybe later try two opposing like you suggest.
Thanks
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Old Nov 20, 2012, 11:36 PM
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I'm sorry, earlier when I asked about bi-quad vs helical, I meant cross-hair vs helical, since I'm looking for cp. Sorry for the confusion. So, how do these antennas compare? It looks like the 5 turn helical and bi-quad have similar gains, so what are the advantages/disadvantages of one over the other? I still think I'm leaning towards the lower gain 3 turn helical, but I'm just curious. Thanks
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Old Nov 21, 2012, 07:16 AM
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Originally Posted by Cervanchez View Post
I'm sorry, earlier when I asked about bi-quad vs helical, I meant cross-hair vs helical, since I'm looking for cp. Sorry for the confusion. So, how do these antennas compare? It looks like the 5 turn helical and bi-quad have similar gains, so what are the advantages/disadvantages of one over the other? I still think I'm leaning towards the lower gain 3 turn helical, but I'm just curious. Thanks
Well, the crosshair is a co-developement of Alex and Hugo and a higher gain antenna (read narrower beam). The helical is very very prooven, well known design which is better scaleable in terms of gain and beamwidth than the crosshair. The crosshair is good if you are for maximum range and potentially intend to use a tracker.

I think for what you have in mind a lower turn helical is a better choice because it has a wider beam. I would NOT combind a helical with an SPW. You will have more "bad switching" of the diversity than you like this way. Either go for a single helical, but then disable the second receiver or use two identical ones right from start. The helical has enough sensitivity to land even behind you if used allone.

Markus
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Old Nov 21, 2012, 08:28 AM
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Originally Posted by markus123456 View Post
Well, the crosshair is a co-developement of Alex and Hugo and a higher gain antenna (read narrower beam). The helical is very very prooven, well known design which is better scaleable in terms of gain and beamwidth than the crosshair. The crosshair is good if you are for maximum range and potentially intend to use a tracker.

I think for what you have in mind a lower turn helical is a better choice because it has a wider beam. I would NOT combind a helical with an SPW. You will have more "bad switching" of the diversity than you like this way. Either go for a single helical, but then disable the second receiver or use two identical ones right from start. The helical has enough sensitivity to land even behind you if used allone.

Markus
Thanks for the advice, I will go that route then.
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Old Nov 21, 2012, 09:45 AM
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From what I understand, the Crosshair is generally superior to the Helical at <10dbic.

Helical
  • Broadband - works well across a large range of frequencies
  • Sidelobes allow for more distance behind and to the side of the main lobe (except for the deep nulls that you'll pass through)
  • Easily constructed, but bulky as you add turns
  • Good axial ratio, maintains decent rejection as you move out of the main lobe
  • <80% efficiency, depending on turns (71% for 5 turn 10dbic)

(I couldn't find a radiation pattern for the 5 turn IBCrazy helicals, so this is just a "generic helical" radiation pattern. Look at the pattern, not the dbic numbers)

Crosshair
  • Narrowband- works only for the frequency that it is tuned for
  • Smaller sidelobes behind the main lobe, but wider main lobe. Allows more deviation as long as you are in front of the crosshair
  • Excellent axial ratio (multipath rejection), although the sidelobes lose axial ratio faster than the Helical
  • Requires precise manufacturing, very compact
  • 98% efficiency



Sources:
http://fpvlab.com/forums/showthread....air-vs-Helical
http://fpvlab.com/forums/showthread....enna-tutorial!
http://fpvlab.com/forums/showthread....gains-lt-10dBi
http://fpvlab.com/forums/showthread....crosshair-5.8!
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Old Nov 21, 2012, 10:02 AM
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Quote:
Originally Posted by polyfractal View Post
From what I understand, the Crosshair is generally superior to the Helical at <10dbic.

Helical
  • Broadband - works well across a large range of frequencies
  • Sidelobes allow for more distance behind and to the side of the main lobe (except for the deep nulls that you'll pass through)
  • Easily constructed, but bulky as you add turns
  • Good axial ratio, maintains decent rejection as you move out of the main lobe
  • <80% efficiency, depending on turns (71% for 5 turn 10dbic)

(I couldn't find a radiation pattern for the 5 turn IBCrazy helicals, so this is just a "generic helical" radiation pattern. Look at the pattern, not the dbic numbers)

Crosshair
  • Narrowband- works only for the frequency that it is tuned for
  • Smaller sidelobes behind the main lobe, but wider main lobe. Allows more deviation as long as you are in front of the crosshair
  • Excellent axial ratio (multipath rejection), although the sidelobes lose axial ratio faster than the Helical
  • Requires precise manufacturing, very compact
  • 98% efficiency



Sources:
http://fpvlab.com/forums/showthread....air-vs-Helical
http://fpvlab.com/forums/showthread....enna-tutorial!
http://fpvlab.com/forums/showthread....gains-lt-10dBi
http://fpvlab.com/forums/showthread....crosshair-5.8!
That's all nice etc, but you should keep in mind that the helical is around for half a century with many research projects behind it etc. where as the Crosshair was developed by two individuals and all information is mostly from simulation software etc. and as such IMHO too idealized. I'm sure that in practize, i.e. when measured out in a real HF lab, above graphs would look a little different.

I do of course not generally doubth what you (or better said Alex and Hugo) tell us about this antenna, but again, the information base of the crosshair is very thin compared to the helical. So what I try to say is to keep this in mind when doing comparisons.

Just my 2 of course.

Markus
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Old Nov 21, 2012, 10:45 AM
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I think ill buy the helical, and also try making a crosshair since it looks relatively easy, then compare. Good info, thanks
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Old Nov 21, 2012, 10:55 AM
Never trust laughing dolphins
Joined Feb 2011
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Quote:
Originally Posted by ror1 View Post
sorry to hear but flying FPV is way harder than normal RCing..
I could not disagree less lol. It's far easier to fly FPV, the thing is that doing it right and comfortably requires a lot of knowledge and a very decent setup. Cut too much corners and it'll come right back to haunt you.

From a technical point of view it's not really that difficult if you are well prepared and listen to correct advise.
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Old Nov 21, 2012, 11:15 AM
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Originally Posted by IBCrazy View Post
^Twist your servo wires and the wires to your video system on the airplane. This shuold improve performance significantly.

I am guseeing that the problem lies in capacitive coupling causing the interference to couple through the servo wires and go right into the RX on the airplane. Another thing to do is put a ferrite choke on the VTX. If your VTX antenna is unbalanced or if your video case is resonating (it happens pretty easily) a ferrite ring around the wires feeding it and it should choke it out.

-Alex
Thanks Alex for advise made it out to 1 mile today with no problem, probably could have gone farther but one mile was my goal for today.
Hope you have a great Thanksgiving!!
Best
Michael
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Old Nov 21, 2012, 04:32 PM
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United States, VA, Virginia Beach
Joined Aug 2005
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Question for the FPV experts.

I'm flying a RMRC 800 mw 900mhz system with one of their Rx (including saw upgrade). I have a small LCD scree for viewing and am using the stock antennas. I had my Rx Velcroed to the back of my LCD and it seems to greatly reduce my range. I used my TV with a friends Rx setup and was able to fly almost a mile.

Does the TV interfere with the Rx?
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