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0 NeutralAbout dalbert02
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Rank
RC-Cam Regular
- Birthday 03/31/1971
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Website URL
http://www.miamidade.gov/mdfr
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Location
miami, fl
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Interests
saltwater flyfishing, uavs, biking, urban exploring
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I started a little post on the history of FPV over at RCG. May you guys that don't frequent that site check it out and offer any corrections or additions or point out any errors. I won't be offended. Thank you. -dave http://www.rcgroups.com/forums/showthread.php?t=1585073
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telemetry radio, a maxstream alternative
dalbert02 replied to dalbert02's topic in R/C Telemetry, FPV, RPV, and UAV Projects
I'd like to send my GPS coordinates from my airplane. I currently use APRS via the audio channel and a TinyTrak but I would like an alternative to get the GPS sentences into my computer/ground station. Thanks, -dave -
dalbert02 started following telemetry radio, a maxstream alternative
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Anyone ever hear of friendcom? http://www.friendcom.com/En/pro02.htm I could only find one distributor in the US, perhaps in Europe they are more available? https://www.argentdata.com/catalog/product_info.php?products_id=107 Do you think they may be worth a gamble as a cheaper alternative to Maxstream Xtend? -Dave
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Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
Any opinions on gray PVC used here and white PVC and effects on velocity factor? -dave -
Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
Finally, sorry for the low quality graphic. I changed to grayscale and made it as large as I could to fit within the 250k file limitation on this board. -dave -
Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
Finally, T3 is a narrow band sweep of the modified antenna. If anyone is interested, I can post the original data files and you can download the free Anritsu software so you can play with the position of the markers, plot Smith charts, or create a return loss plot. -dave -
Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
T2 is a narrow band sweep of the original. -
Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
Attached are the SWR plots of before and after. T1 was a wideband sweep of the original antenna. -
Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
Sorry for the long delay. Sometimes there is not much activity here so I forget to check often enough. Regardless, here are some pics of IBCrazy's helix antenna. Both before and after compressing the coils. I used a sharpie to trace the original wire path and to use as a guide while compressing the coil. -dave -
Antenna Projects
dalbert02 replied to Mr.RC-Cam's topic in Wireless Video Antenna Problems and Solutions
One more I am curious about, what are your thoughts on this (if you do not mind)? http://www.trivec.com/landbased_av2055.html Obviously this would be a recieve only antenna and need to be built for your frequency. I like the idea of portability, circular polarization, and light weight. I'd love to build one for 2.5Ghz if I could find some plans on it. Thanks, -dave -
dish or yagi
dalbert02 replied to dalbert02's topic in Wireless Video Antenna Problems and Solutions
Thank you very much for the idea of using an attenuator. I just won a bid on a really expensive Pasternack stepped attenuator on eBay (won for only $60!) but I don't think it is rated up to 2.5Ghz. The fixed attenuators are not that expensive so I will look at those. I know Meca and MiniCircuits mentioned make descent ones. Are there any other recommended brands or brands to stay away from? Thanks, -dave -
dish or yagi
dalbert02 replied to dalbert02's topic in Wireless Video Antenna Problems and Solutions
Nigel, That link is awesome! Thanks! Thomas, Your link is not working. I tried searching the site but did not come up with anything. Perhaps I am over thinking this. I want a wide margin of error (+6db) for an upcoming mission. I need to fly several kilometers over ocean and can not have a video failure. Given: Rx sensitivity -80db for an acceptable picture Rx antenna +10dbi Tx +27 dbm Tx antenna 0db gain Cable loss 3db (1.5 on each side) 2510Mhz 10km Then I'll have 120db of path loss and an RSSI of -86.4dbm. http://www.distributed-wireless.com/calculators/pathl -
dish or yagi
dalbert02 replied to dalbert02's topic in Wireless Video Antenna Problems and Solutions
Thank you very much for your insight. Now on to my next question. Assuming I go with a dish antenna, I would like to calculate the expected gain for a dish of d diameter. From Wikipedia (http://en.wikipedia.org/wiki/Parabolic_antenna) I learned that the Gain G of a dish can be expressed as G = ((4 π A) / λ2) eA or G = ((π2d2) / λ2) eA Where G = Gain A = Area λ = wavelength d = diameter eA = is a "dimensionless parameter called the aperture efficiency. The aperture efficiency of typical parabolic antennas is 0.55 to 0.60." So for an example, if I look at a dish from Hyperl -
Here is a link straight to the tutorials. Complex to Real Tutorials -dave
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If I had: a dish that claims 24db of gain a yagi that claims 24db of gain a patch that claims 24db of gain and they are all tuned to the same frequency, would you expect equal range out of each? Is one type of antenna any better than the other for any reason? Thank you, -dave