|
|
|
Hello, gang.
I'm getting ready to build my first one of these antennas for my 900mhz VTX. I can only find .030" welding wire, and am currently looking for the RG-316 coaxial cable with the male SMA connector. Can anyone give me a link to a source for the coax? I've searched this thread and haven't found any references to this. BTW, will .030 be ok for 900 mhz? Thanks, Bob |
|
|
|
|
|
|
|
|
|
|
||
|
Quote:
|
|
|
||
|
|
|
|
|
|
|
||
|
Quote:
I'll do the CL and SP. |
|
|
||
|
||
|
Quote:
That should be enough cable to do pretty much whatever you want, but make sure that the connectors are correct for your VTX/VRX. I had to buy an F to SMA adapter for my VRx in order to use that extension, but it's whatever. http://videoaerialsystems.com/products/accessories/ Good luck, take your time, and ask questions if you have them |
|
|
||
|
||
|
Quote:
That would most likely help alot of people out with construction. |
|
|
||
|
||
|
Quote:
Alex was very kind to provide me with some build materials and a sample lobe. Initially (this is how my CL was made) I bent some wire along the template lobe, and later made a photocopy of the lobe, but this proved to be difficult. For example, the mig wire comes coiled with a slight bend. So I used read backwards on this thread, then later used the search function to get exact sizes for 2.4ghz, and couldn't find them. So I started reading from the beginning of this thread. As of yesterday I have made it to page 19. Its going to take me a while to get up to page 122+. I deducted the approximate measured sizes from this post. I haven't confirmed this, but I think "1/4 wavelength" is each side of the lobe, and 1/2 wavelength is the arc (as a straight wire). So: Quarter wavelength in mm = 76755/f in MHz So for: 910MHz = 3.32"/84mm 1280MHz = 2.36"/60mm 2.4GHz = 1.23"/31mm 5.8GHz = .52"/13mm So for me, 31mm sides and 62mm arc. Total wire length is 124mm, 1 wavelength. Again IIUC, this is the MIG wire measurement from solder point to solder point: where it leaves the coaxial cable sheath at 90degrees, to where it meets the coaxial wire center in the middle. Thus you need teh actual MIG wire to be a bit longer on each end, say 3mm and 10mm, to accommodate solder. For you on 5.8mhz, 13mm sides, and 26mm arc. 52mm total length, etc., etc.,... I was concerned with distortion or length loss/gain due to bends, but Alex mentioned that the length is not important. For the SPW antenna, I cut 4 lengths of wire to 137mm, lay them as flat as possible on a ruler, and marked them off all together with a marker at the bend sites mentioned above. Then pliers, and then by hand bend the arcs to approximates lobes. Then the unbalanced business of soldering. I have broken the solder points 3 times trying to bend to different geometries. I'll only get away with that a few more times I think, then I'll have to order more wire and cables to make new antennas. My antenna are still giving very poor video, so I'll have to try more bending of lobes. As a side, I have seen a new type of video distortion. doubled images, and when I twist the VRX antenna, color saturation changes. Is this "multi-pathing"? Also, what happened to the jig videos? If I can get these antenna working, and if there is any interest, I can make a "Super Simple antenna making guide" for new people. EDIT: My bench tests are surrounded by houses and wifi networks. Is this a special problem for 2.4 CL/SPW combos over my traditional 2.4 whip/patch? |
|
|
Last edited by TheNiceGuy; Dec 04, 2011 at 04:19 PM.
|
|
|
|||
|
Quote:
Quote:
Bob |
||
|
|||
|
|
|
you can get copper wire that is thick(1-1.5mm) and simply stretch it. this will shrink the diameter and yield a perfectly straight wire
|
|
|
|
||
|
Quote:
Can you tell me if my above mentioned ideal side/arc measurements (31mm/62mm) are correct? I took more precise measurements of the current actual antennas I made, each lobe. CL: bottom sides 28mm; top sides 32mm; arcs 65mm. SPW: all sides are 32mm; three arcs are 65mm; one arc is 62mm. Are these values critical, or am I overthinking this? |
|
|
||
|
||
|
Quote:
-Alex |
|
|
||
|
|
|
Thanks, but the bench tests are horrible. Any idea whats going on?
|
|
|
|
|
|
WiFi if I had to guess. I have occasionally done bench tests placing the VTx in another send of the house expecting it to penetrate walls and overcome my wireless internet. It never seems to do well, so I go unplug my wireless router
For some reason bench tests are very difficult with antennas. The best test is to thorw them on the plane and fly standard point of view and record the video, then review the video and see how it does. -Alex |
|
|
Thread Tools | |
Similar Threads | |||||
Category | Thread | Thread Starter | Forum | Replies | Last Post |
Mini-HowTo | Circularly Polarized Helical antenna 7.5 -13 dbi - New: Wave Trap match! | IBCrazy | FPV Equipment | 2503 | Apr 17, 2022 11:39 PM |
Mini-HowTo | IBCrazy's DIY antenna tracker!!! | IBCrazy | FPV Equipment | 473 | May 20, 2021 09:27 PM |
Mini-HowTo | Fast Patch - IBCrazy's easy DIY patch antenna | IBCrazy | FPV Talk | 365 | Oct 04, 2020 04:10 PM |
Build Log | IBCrazy's Minion - The ultimate FPV plane | IBCrazy | FPV Aircraft | 151 | Apr 19, 2013 11:04 PM |
Build Log | IBCrazy's homebrew antenna tracker | IBCrazy | FPV Talk | 48 | Oct 25, 2012 06:07 PM |