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Old Feb 17, 2011, 10:38 AM
Engineer for Christ
IBCrazy's Avatar
Amherst, VA
Joined Jun 2006
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Quote:
Originally Posted by MarcAntonio View Post
Thank you IBCrazy for your great tips. Today I built my first homebrew antenna.
A CL for 2.4ghz.

I installed it on my cheapo (free) 10mw airwave transmitter from my trimersion headsets.

With the regular whip I would get grainy video after 1km max 1.2km.

I tested this and the graining begins at 2km , that's out of a 10 - 12mw tx.

I am sure I didn't do it perfectly because I have a 4-5mm gap between the feedpoint and ground, and It's working so well. I am still using a stock whip antenna on the receiver. I should try and use one of these on the RX unit as well and see what happens.
do you advise against using expanding foam to make a small dome to encapsulate the antenna?

Here is a pic of my little antenna:
2km on 10mW!!! Wow! I wouldn't have expected that kind of distance. The airgap you have is fine. It won't affect performance much. Now you need to try one on the RX as well.

I wold recommend finding a small foam ball like Mictronics did. Craft stores usually have all sorts of sizes. Just hollow out the middle.

-Alex
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Old Feb 17, 2011, 10:41 AM
Engineer for Christ
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Amherst, VA
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Quote:
Originally Posted by jhoexp View Post
Hi Alex, very useful post as always....
Started building two of them, one for a small multirotor and one for the ground station bridge/repeater to my fatshark, using 5.8 ghz video tx.

Any suggestion for this frequency, should i be very precise with this?
It's ok to use steel/iron wire instead of copper?
Feeding it directly to the the sma connectors (like hugeone did in the photo) can cause problems?

What's the best match on the receiver side (fastshark googles) for one of this on the air/ground? (keep in mind it must be small and light not to bother when you wear the googles)

I use copper clad steel welding wire for my mig welder. It works great.

For 5.8GHz, the tolerances are very tight. However, the antenna is wideband so you don't need to be perfect. Just get it as close as you can.

-Alex
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Old Feb 17, 2011, 12:24 PM
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Joined Jan 2010
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Quote:
Originally Posted by IBCrazy View Post
2km on 10mW!!! Wow! I wouldn't have expected that kind of distance. The airgap you have is fine. It won't affect performance much. Now you need to try one on the RX as well.

I wold recommend finding a small foam ball like Mictronics did. Craft stores usually have all sorts of sizes. Just hollow out the middle.

-Alex
Yes, well all my distances are much higher than other people because of my location. Flying from mountain tops in south Italy with no interference really helps. I get over 3km with 1w tx and stock antennas... go figure, I bet that with these antennas I can venture out further with the more powerful tx.
We'll see.

P.S. that's also how Trappy got his record. Flying through a valley from a mountain top with mountains on left and right, reflects the signal, plus it's as if your RX were placed very very high.
If you try setting your receiver up 20 feet on a telescoping pole, you'd probably double your range as it is, I don't know if you have tried that.
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Old Feb 17, 2011, 02:01 PM
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Quote:
Originally Posted by MarcAntonio View Post
Yes, well all my distances are much higher than other people because of my location. Flying from mountain tops in south Italy with no interference really helps. I get over 3km with 1w tx and stock antennas... go figure, I bet that with these antennas I can venture out further with the more powerful tx.
We'll see.

P.S. that's also how Trappy got his record. Flying through a valley from a mountain top with mountains on left and right, reflects the signal, plus it's as if your RX were placed very very high.
If you try setting your receiver up 20 feet on a telescoping pole, you'd probably double your range as it is, I don't know if you have tried that.


Can't be too scientific but YES this idea worked for me Bog standard whips on cheapo tx/rx. Masking tapped the RX to a carbon extending carp fishing/flag pole, put the end of it in a large axle stand (for supporting a car when the wheels are off if you work in an office) and conducted some stange ground tests as my friend watched on my gopro's. Signal much clearer and glitches all but disappeared as I danced around the field 500 meters away moving the cam/lipo/Vtx around like a witch doctor!!

Paul

Alex... I think metric version of you mig size is what I use for general use (actually I have got pretty good at using in on car body sheet metal as I am too lazy to swap the reels out for .6mm). The big question is - what works best random or precision wound???

Paul
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Old Feb 17, 2011, 02:04 PM
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Oh and just in case any UK FPVers are reading this thread... I can bring along a few meters of mig wire to the secret location for you to practise antenna Origami...
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Old Feb 17, 2011, 03:55 PM
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SW England
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Paul, I'm watchin ya

0.6mm MIG wire is quite strong, but 0.8mm would be better.
Downside of MIG wire is that the copper coating is very thin and over time, the steel wire below will rust and percolate through the copper - ever left your welder in a damp garage for a few weeks and then wonder why your weld is like seagull pooh and you need a new liner for the gun feed?

The best wire is the gold plated 'Memory Wire' used for making neck and wrist bracelets - I got mine in my local 'beads n bangles' shop - it's the one full of ladies giving you strange looks

Ever used one of these?
http://www.nevadaradio.co.uk/antenna...ts/comet-mcb-3
Drive a wheel over the base plate and drop an extending mast over the pole, voila, sturdy mast at 20 foot.
Made my own for operating on Amateur Radio VHF field days.

Nigel.
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Old Feb 17, 2011, 08:47 PM
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Amherst, VA
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Performance video

Head to head against the Vee.

IBCrazy's FPV "New system" - Cloverleaf demo (4 min 42 sec)
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Old Feb 17, 2011, 08:57 PM
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USA, CO, Durango
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Nice! I really want to build one now. Should have used the ground plane on the rx for a fair vee test though, wouldn't that have done better than the stock whip?
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Old Feb 17, 2011, 09:13 PM
Engineer for Christ
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Amherst, VA
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Originally Posted by volto View Post
Nice! I really want to build one now. Should have used the ground plane on the rx for a fair vee test though, wouldn't that have done better than the stock whip?
Not in this case. Look what happened 2500 feet out. I was still getting multipathed hard. In fact, the closer I got, the worse the interference. Admittedly the stock antenna did much better than I expected. I was never able to get it out that far before.

The results with the linear antennas is not repeatable. I could fly back to back flights in the same direction and get different results each time. However the results with CP are consistent.

-Alex
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Old Feb 17, 2011, 09:36 PM
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I just built your vee and ground plane, and now they are obsolete
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Old Feb 17, 2011, 09:41 PM
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Amherst, VA
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Originally Posted by volto View Post
I just built your vee and ground plane, and now they are obsolete
Yep, second best. Yet still better than anything available 2 years ago. The Vee/ground plane has longer range if you are standing out in the middle of nowhere. Most model airfields I have been to fall into this category. The more remote the location is, the better linear polarization is. However in noisy environments with lots of objects which a signal can reflect, circular polarization becomes a better option. It also is more consistent.

-Alex
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Old Feb 17, 2011, 10:02 PM
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Alex great work. What is the cost for you to build.
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Old Feb 17, 2011, 10:17 PM
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$35 for one premade to your frequency and tested for SWR and circularity. $5 to ship as many as you want. I haven't officially launched the product yet. I will be on vacation until the end of February (going skiing) and cannot supply them until after I get back. I am sending stock to a certain FPV vendor right now

-Alex
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Old Feb 17, 2011, 10:22 PM
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Australia, QLD, Gold Coast
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Alex you are amazing, not only for your brilliant tutorials, I see you answer every one's question without vanity.
Many of us here never touch the keyboard but to prove ourselves.
We have byword in my language says "Musk is the one that fragrant not the one perfumer says"
God bless you
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Old Feb 17, 2011, 10:23 PM
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Huntsville, AL
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Any chance I can order a couple kits before you head out on vacation?
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