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Chuck

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Everything posted by Chuck

  1. Sorry for the delayed response and thanks for the particulars.... I will be using a receiver that has more sensitivity than a TV. Also I will be using a 5 element Yagi which should get me some "front to back" without being too finiky on the pointing (for those who understand antennas, the front lobe is rather wide). Also, [as I recall] doubling the power is 3db of gain. I will be using 500mW for starters (the TX can do 4 watts and I have a brick amp that can do 25 watts), so that 500 mW represents a +6db gain and the Yagi gives me another +6db. But, hay, this is all theoritical math giberis
  2. I'm not familiar with that antenna... and a google search of "lazy 8 antenna" didn't turn up much usefull, probably because "lazy 8" is used a great deal for other things. Can you point me to a specific reference? Best Regards, Chuck
  3. How true... FM is much more efficient, and as long as the receiver can capture the signal the quality will hold up. AM needs more power, and as the signal degrades the picture will snow. Also, random signals (e.g., atmospheric) below a threshold will not show up in the picture (noise immunity) in FM as it will in AM. The frequencies that we are talking about are different as well; 70cm vs 12cm and 25cm. In the higher frequencies there is more bandwidth available and using FM it is possible to trade bandwidth (modulation index) for noise immunity (a good thing for sure). Also, low noise prea
  4. Thanks for the comments.... I wish you would tell me more about the first point; 70 cm band transmitters being less reliable when moving. I would like to understand this better. In your experience was this a reliability issue with the hardware not working, or a difficulty in signal reception as the plane moved? How much power were you using on the TX, what kind of RX were you using, and what kind of setup did you have for antennas? And yes... I havn't own a TV for over 20 years [2% of the US population doesn't own a TV by the way], and I don't intend to change that now... I'll be using a
  5. Electric. Yes, one of these should do the trick... Thanks! There is also a Real Flight model for the larger one that I could adapt.... http://www.knifeedge.com/forums/downloads....ile&id=1293 I'll play with it on the simulator and see how it files with the extra weght! Yes, the 2.5 ghz equipment is lighter and cheaper. However, the propagation is better on the 70-cm band (for equivalent power) and a ham can legally use more power. You just have to ID after 1W (call sign painted on the fuselage in view of the camera), and not "step on anyone". The TX and RX are synthesized so I c
  6. I've settled on a transmitter.... http://www.transmitvideo.com/pdf/VM-70X_Manual.pdf http://www.hamtv.com/pdffiles/VM-70XwHS.pdf I was going to use a B/W camera on this. They are less expensive (about $30US) and can see better in low light conditions. Later I'll experiment adding GPS data to the audio of the transmitter. For an antenna on the transmitter I was going to use a 1/4 wave (electrical; physically shortened stubby duck) vertical pointing down mounted on the belly. That is the ground plane will be above the radiating element, so the radiant energy will be omni directional and
  7. Are you talking about something like this?? http://www.hamtv.com/pdffiles/R-C.pdf http://www.hamtv.com/pdffiles/TXA5RCbinfo.pdf Charles
  8. Thomas, I appreciate your feedback. I'm going to hold off on the video decisions for awhile till I sort this out. I am going with VHF (6 meters) RC though. No problems here in the US... The only "probllem" seems to be that the equipment is not going to be available in the future. It seems that the major brands are selling off their remaining stock, and that's it. My guess is that some time ago when the US FCC "gutted" the ham exams that the RC manufacturers assumed that there would be people with Tech licenses coming out of the woodwork. But that didn't happen. Given the lack of used [ham R
  9. Thanks for the feedback.... Yes, I had thought of adding GPS... It occurred to me (from my experiences in a time long ago) that it would make sense to use a modem on the audio portion of the downlink of the video camera.... You could add the GPS data as well as other information there. Even at 1200 baud, it should be sufficient. I think that there are some folks doing that... Once you have the data link you could add a PIC that monitors the voltage on the plane battery and send down that information as well (it would be nice to know how much power you have left in the battery before goin
  10. From reading the boards, it appears that people are using and having success with the following packaged solution... Aerial Video System 900MHz 500mW KX171 http://rangevideo.com/index.php?main_page=...;products_id=98 If starting again from this system, are there any specific "lessons learned" tips that anyone would be willing to pass along? Thanks, Chuck
  11. Based on what I have been able to read [at least] the 9C Super Tx is modular, so when I decide what band I want to use I just get the Tx module, Xtal sets, and the appropriate Rxs. I'm going to set my old Drake R8 receiver scanning on the 6 meter RC frequencies, and just listen for what's happening. Given that 6 meters is less "line of sight" I don't believe that I have to worry that the antenna is on the ground or [as in a plane relatively] near the ground. Also, I'm thinking that the 9C has been around for a while and so is more likely to be found used. I decided to stick with Futaba since I
  12. Thanks for sticking with me on this... I've done some more reading on the boards. At this point I am looking to purchase an R/C radio system. Given the bandwidth requirements of video, it makes sense to stick with the high frequencies on this. I want to avoid interference, and being an extra class ham in the USA, it would seem that one of the 50MHz rigs would be a good option (Futaba 9C?). Also, with the 50 MHz system, I could more easily find a commercial Yagi to increase the directional gain and thus (if I am lucky e.g. source of interference is away from the plane) reduce possible causes
  13. Added my location to the profile... Thanks... Well.. Range should be no problem with the VHF radios, but what about intefrerence with others on the same frequency?! Or is this [in fact] an "oberblown" issue. If you are flying in an area where there is [likely] no other R/C activity you should be OK so long as the receiver doesn't get to high in the air. My experience with the ham VHF bands is that the signal can carry, especially near the peak of an 11 year sunspot cycle. Though with a VHF R/C and a UHF camera you will loose the picture before control of the airplane. However, if you can't
  14. PA USA. I'll need to read the boards more carefully. I got the impression from scanning several posts that the major interference was to the video signal, and not the Digital Spread Spectrum receiver. If that's the case, then that's good. I've been involved with a number of ham repeaters over the years. Given the weight restrictions on a plane and lack of space there would not be much that could be done on same band interference. However, vertical antenna separation (of verticals) is very effective, especially given the 2.4 GHz short wavelengths. Are you aware of anyone who has tried this w
  15. Please excuse me if my topic is trodden ground... However, as most on this forum, I am interested in controlling an R/C aircraft with a video down link. Most of the commercial solutions would appear to be problematic. The new spread spectrum R/C control tx/rx setups are great w.r.t. lack of iterferance (both directions), but the higher frequencies are mostly line of sight. They also tend (from my ham experience) to loose in the winter time when every twig on every tree ends up looking like a quarter wave vertical and thus eats the power. Couple that with the fact that the spread spectr
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