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Attention: RC-CAM.com will be closing down August 2021.

The RC-Cam.com forum was the very first online community dedicated to the advancement of wireless video cameras on radio controlled (R/C) models. This is now called "FPV" (First Person View). We are proud of the contributions that our members have made to the FPV hobby.

We've seen significant changes over the last twenty years. Initially there were a lot of eager R/C hobbyist that built their own video systems. Allowing these creative individuals to share their work was the purpose of this site. Now the FPV market is flooded with low cost systems; Sadly DiY FPV video projects are now rarely discussed.

RC-CAM.com (main site and forum) will be closing down August 2021. This is being announced now (March 2021) so that everyone has time to download any information that is important to them. After the site is shutdown the information will no longer be available here.

We appreciate every member's involvement with advancing the FPV hobby. It is indeed sad to say goodbye to all our online friends. Be safe and stay healthy.



Jlerch

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Everything posted by Jlerch

  1. Here's the beach video. The ground station is located at the large concrete building seen at the 1:35 second mark. Not the most desirable position, and it showed a few times. Apologies for how jerky this one turned out, I was out near the water flying direct, while the glasses and ground recorder were passed around the family. I look forward to getting out and trying again with a proper setup, should be fun
  2. Ok, Here is a follow up. In a nut shell, this setup is much better than I had before on the other airframe. If its because of the antenna or just the way it was installed, I don't know, but its working great. For the first time I was able to record a whole 10 minute flight with out my ground recorder giving the video input the finger after a loss of signal. I still don't trust the system yet, that will take a little time, and the only complaint I have is the little white foamy airframe is darn near impossible to find when transitioning from FPV to direct observation. Once I get
  3. That reminds me of a good friend that landed a job with "Harris Corp" back in the late 80s. It sounded so cool on paper, he was going to be building a military Tank warfare simulator. In practice, he sat behind a terminal typing numeric values into what he described as a three dimensional data base, describing each cell's details such as altitude, collision data, color, etc. I thought that sounded kind neat until he told me they only rendered the terrain every 2 weeks, then they spent the next week debugging the existing terrain, the week after that building new terrain, re-render, repeat.
  4. With a Homer Simpson Esque "DOH" I finally realized how sources were working in the simulator, which is NOT how I thought they worked.. After reading the Stinking instructions in the help file, I worked out the following simulations for a single RF source ant. In free space: 1 inch above normal soil 10 feet above normal soil 100 feet above normal soil 1000 feet above normal soil I still don't get why the sim says 3.24" = 1/4 wave, but clearly prefers the 1/4 wave Ant height to be 3.08" At this point, I'm going to stop playing with the sim and get ba
  5. The quarter wave monopole is depicted on an infinite ground plane. I have a finite ground plane, and that ground plane is only 1/4 wave in radius. I wonder how such a small diameter 'ground plane' will affect the situtaion.. Time to fire up the simulator again and increase the radius of my 'ground plane' by several wavelengths to see if I get your Infinite ground plane radiation pattern... BTW, if I wanted to use a simple half wave center fed dipole. Only the center conductor would be attached to the center antenna, what completes the circuit?
  6. I wish I knew what I was doing, because I'm doing something wrong as my ant models don't bear this rather obvious common sense solution. For instance, comparing the same two antennas in free space, one pointing down, the other pointing up Same thing, flipped over pointing up: Now same antennas, but modeled at an altitude of 120feet over "high accuracy" ground consisting of pastoral or heavy clay. Pointing down: Pointing Up: In free space the two orientations appear identical, over earth, the two antennas seem to have the largest deviation based on constructive /des
  7. This is one of those compromise results. The airframe may have to make a water landing, and I'm trying to keep everything above the water line. Also, the airframe doesn't have landing gear, so its a belly landing every time. I couldn't come up with an attractive solution to either problem. I finally gave up on the "point it down" approach when the modeling software clearly showed the free space radiation pattern as a big beach ball in either orientation. When modeled over ground, the pattern was essentially the same.. Of course, all this assumes I modeled it correctly, which is
  8. Ok, here's what I came up with, and I'm looking for a GO or NO-GO recomendation. (Plus, exactly who else could I show this to that might have any appreciation for the work involved The center vertical is 1/4 wave long at 910mhz or 3.24 inch, measured from the top of the 90 degree SMA -> Coax connector The 6 radials are also 1/4 wave long and a made from stainless steel spot welded to the outside of the sma connector. The hot glue is there for strain relief. As Installed on my Foamy glider: As modeled at an ALT of 120 feet over normal soil. If I get the wiring done,
  9. This is interesting. Anyone have the tools to make one and test it? http://www.edn.com/article/CA296495.html
  10. After asking a few questions, it appears that the turtled necked dipole and the one modeled on Mr.RcCam's link are not the same. The one on the link has the lower legs connected to the top radiating element. In esesence its just an odly shaped dipole The lower half of our turtle necks are not connected to the top radiator, right?
  11. Ok, Here is what I get for a center fed dipole in free space Now here is what I get for our Coax "dipole" in free space
  12. Peter, I screwed up and posted the wrong image, Try this one. Its "more right" With regards to your 4 points #1, I can only model 20 "segments", so I only get 10 segments per wire, and the resulting 5% discrepency. #2 The X/Y image of the ant is centered on the ant/ #3 tried both volt and current sources, the patterns were a touch different but not much. #4 Yes, there is a ground plane, its ~10 wavelength (3 meters) below the antenna. If I turn it off and use free space, I get this perfect looking double stacked donut. Oh NEAT!! Just played around with putting t
  13. So, I'm attempting to model our simple turtle necked dipole in a program called EZNEC ARRL No point really, other than to attempt at getting a grasp as to what's going on. So, my question is this, does this look right? I created two vertical wires, each 1/4 wave long, with a tiny space between the two. I've connected two sources, one to each of the two wires, on each side of the tiny space, and put them 180 degrees out of phase. I've played with a lot of optical design, so this feels kinda familiar, but I think I've done something odd. Here's what it looks like:
  14. Would an Oracle Video Diversity Controller help me any? IE, will it still drop Vsync as it switches sources?
  15. Thanks Gents, I was afraid of that, a splitter is actually a repeater. Garbage in, Garbage out.. So, is anyone using a DVR that works somewhat reliably? I think I'll do better once I get away from all the "Garbage" in my yard and get back out into the open country. The fades will happen less often, so the DVR should keep going. However, I want to be able to count on the DVR for the time when I put the airframe in. Not having a video to go look at and triangulate off of is going to really "Grind my gears"!
  16. Ok, so I did some searching and I did a No-No by y-ing a video cable from one source into two video devices. The 1st device is my Video Goggles (which work fine) and the second device is an AipTek A-HD camera that I normally love, but this is the first time I've tried using it as a DVR. The problem is the Aiptek Camera, doing duty as a DVR, will stop using an external signal if it loses sync or gets static on in the video feed. Instead of soldiering on, it says to heck with it and stops recording. It took me a few times to figure out WTF?? One minute it worked, the next minute it did
  17. So, After flying for a few days and being absolutely addicted, and having limited idea on how this RF stuff really works, I've come to the conclusion that most of my problems are multipathing interference. So, I started doing some google searches, and stumbled upon this antenna design, the choke ring antenna. http://www.trimble.com/infrastructure/gnss...x?dtID=overview http://www.javad.com/jns/index.html?/jns/t...oke%20Ring.html So, Has anyone tried one? It looks easy enough to fabricate. Well, easy if I had dimensions to start scaling one to my 910mhz stuff. BTW
  18. So, I was building the rc-cam4 system rc antenna (www.rc-cam.com/rc-cam4b.htm) using a piece of coax I found off an old 2.4ghz "Spektrum" RC radio transmitter antenna. I test fit everything before I went at it with the cutting instruments. After turtle necking the ground shield, I grabbed the ohm meter to check my work, and crud, the female threaded section doesn't have a male center post. So, I thought I had an SMA connector on the coax, but I guess they make more than one version? Is there a Wiki / Faq / or something detailing a simple way for a darn new guy like me to navigate the
  19. Thanks guys, I got some more time on the bird today, and boy is this addicting! Let me ask one more thing that I don't understand. It is with regards to a dipole antenna fabricated from coax cable. How does peeling back the ground shield work? IE if I have 3.2 inches of center conductor exposed, and 3.2 inches of the braided shield peeled back and pulled up tight against the existing cable, how is the exposed ground shield different than the actual ground shield it overlaps? I guess coax cable is one of those things that mystify me, which usually means I'm lacking an understanding
  20. 1st a big thank you for forum, I've been reading, building, flying, and encountering an amazing amount of success in the last 24 hours. Here's a link to my "shout out" thank you video for the GP Patch antenna: I recorded this video shortly after my first REAL FPV flight of nearly 16 minutes, and I might have been a little excited at the time of the recording. My first attempt at FPV with stock antennas resulted in a frustratingly terrible video signal. Yesterday morning I did some searching, found this site, found the instructions, realized how 'simple' they were, built it f
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