osa Posted May 8, 2016 Report Share Posted May 8, 2016 I have a new bag rig with sna dipoles mounted as compact as possible which is working out quite well. On a job today in tight spaces and running into my camera op from time to time. I dont fully understand the mechanics of these dipoles so this is probably a question for lectro but thought i would check here first. Looking down at them, has anyone modified these adjustable aluminum atenna rods to be removable sma antennas top and bottom? It looks simple enough but prob more than meets the eye. I realize the adjustable-ness of these curret aluminum versions would be lost but i would just use Block appropriate whips if I could pull it off. Anyone have any input on this idea? -Ken Quote Link to comment Share on other sites More sharing options...
Glen Trew Posted May 8, 2016 Report Share Posted May 8, 2016 Good idea. This should be easy to do with the same material as used on the Miracle Whip 216mHz extensions (http://www.trewaudio.com/product/remote-audio-miracle-whip-mw216-kit/). I'll try to make that happen and post the info. GT Quote Link to comment Share on other sites More sharing options...
rich Posted May 8, 2016 Report Share Posted May 8, 2016 ive made antenna extensions for a few people, where i have put a female SMA at the end of the cable, attached an appropriate length of the coaxial shield to the shell of the female SMA which is then covered in adhesive lined heatshrink, then you can screw in an whip antenna to make a dipole. I believe its the same idea as lectrosonics use for their coaxial dipole, but a bit sturdier. Quote Link to comment Share on other sites More sharing options...
osa Posted May 8, 2016 Author Report Share Posted May 8, 2016 54 minutes ago, rich said: ive made antenna extensions for a few people, where i have put a female SMA at the end of the cable, attached an appropriate length of the coaxial shield to the shell of the female SMA which is then covered in adhesive lined heatshrink, then you can screw in an whip antenna to make a dipole. I believe its the same idea as lectrosonics use for their coaxial dipole, but a bit sturdier. I too have made a few dipoles That work great but when comparing side-by-side with these Lectro dipoles there seems to be some extra magic happening in the lectros. I thought somewhere back in previous threads larry explained the science happening but I can't seem to find it at the moment. Glenn – you were definitely on the right track, ideally what I was envisioning is some sort of SMA right angle replacing the base of the aluminum antennas both up and down and whips screwing onto those. Just thinking this through on paper. It might be overkill if I can custom make a dipole whippy rig that would emulate the exact same thing. These sna's just seem to give me range for days over my home made dipoles and certainly way beyond standard whips -Ken Quote Link to comment Share on other sites More sharing options...
rich Posted May 8, 2016 Report Share Posted May 8, 2016 the SNA600 will most likely have a balun in there, though I wont try to badly explain what one is or does. wikipedia etc is your friend if you want to know about them. Quote Link to comment Share on other sites More sharing options...
LarryF Posted May 9, 2016 Report Share Posted May 9, 2016 There is a stripline balun (BAL anced to UN balanced) and a stripline matching network to go from the dipoles approx balanced 70 Ohms to the unbalanced 50 Ohm input. The reason for the wide arms is to broadband the antenna as much as possible. A subtly sophisticated design though simple in appearance. Replacing the fat arms with thin wire will change the loading (unimportant) and narrow the operating bandwidth (more important). The frequency markings will also be incorrect. Best Regards, Larry Fisher Quote Link to comment Share on other sites More sharing options...
osa Posted May 9, 2016 Author Report Share Posted May 9, 2016 18 minutes ago, LarryF said: There is a stripline balun (BAL anced to UN balanced) and a stripline matching network to go from the dipoles approx balanced 70 Ohms to the unbalanced 50 Ohm input. The reason for the wide arms is to broadband the antenna as much as possible. A subtly sophisticated design though simple in appearance. Replacing the fat arms with thin wire will change the loading (unimportant) and narrow the operating bandwidth (more important). The frequency markings will also be incorrect. Best Regards, Larry Fisher Great info! This is more of a luxury idea. Not like I am drawing blood with sharp edges. Would block specific whips cut to appropriate length work? I think this sounds like no dice. dont want to ruin an already good thing -Ken Quote Link to comment Share on other sites More sharing options...
LarryF Posted May 9, 2016 Report Share Posted May 9, 2016 Hi Ken, Yes, but they should be trimmed using a network analyzer or SWR bridge since just cutting them to the "right" length doesn't work that well in practice because of finite connector lengths and interaction with the striplines. The fat arms on the antenna are different in length to a thin wire for the same frequency. Best Regards, Larry F Quote Link to comment Share on other sites More sharing options...
Ken Wilkinson Posted May 24, 2016 Report Share Posted May 24, 2016 Would it be possible to run one of these SNA with 72mhz antennas? Quote Link to comment Share on other sites More sharing options...
Shastapete Posted May 24, 2016 Report Share Posted May 24, 2016 1 hour ago, Ken Wilkinson said: Would it be possible to run one of these SNA with 72mhz antennas? The quarter wavelength of 72mhz is 39 inches, so you'll have a 6.5ft wide dipole Quote Link to comment Share on other sites More sharing options...
Ken Wilkinson Posted May 24, 2016 Report Share Posted May 24, 2016 Was hoping for a helicopter type thing. Quote Link to comment Share on other sites More sharing options...
mikewest Posted June 9, 2016 Report Share Posted June 9, 2016 Good for drying Rycote WindJammers on then! mike Quote Link to comment Share on other sites More sharing options...
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