Making a Coax Dipole Antenna for a Wireless Microphone System

[@davidaliperti]

and of course being a dipole I can plug it to any 50 ohms extended cable. Anyway I attached 2 of these to my harness, this saved my job 1 week ago, was having drops with the whip antennas since we were squeezed in tiny room with audio bag, cameras following the tv host in a building. thank you.

[@lectrosonics]

David, that's great to hear! Thanks for letting us know. The coax cable antenna is a great solution for a variety of applications. We wish more people would use them!

[@davidaliperti]

I suppose that it would.be effective for radio ham / trasceiver also.

[@SupersSandor]

thanks for posting. love these little tips

[@davidaliperti]

Thanks for sharing this, I extended the sheath all along the shield and the core. Any problem with that?

[@lectrosonics]

That should be fine!

[@genekim2248]

Very helpful, thank you! What type of cable are you using?

[@lectrosonics]

We recently made some of these antennas again using Amphenol RG316 cable material with pre-terminated SMA connectors. We needed ones that were 4.5 ft. long so we purchased a 10 ft. SMA-SMA cable and cut it in half. RG174 also works well.

[@shugcelie]

Hi. Thanks for this video. Any reason this can't be deployed with your 822's? (I hear you mentioning in the video that this works with transmitters as well as receivers, but just triple checking since the video was made about 5 years before the 822's came out). Thanks.

[@lectrosonics]

Yes, absolutely! Passive antennas are reciprocal - they can be used for transmitters or receivers, and have the same directional properties (i.e. a dipole has a "donut-shaped" pickup OR transmission pattern. These coax antennas with an SMA connector would work well for the DCR822.

[@AboubakrA]

great technique, but I was wondering wouldn't there be mismatch between the cable (feed) and the antenna ... dipole 73 ohm and the cable having some other characteristic impedance

[@lectrosonics]

The cable should be 50 ohm, and this small an amount of mismatch would be difficult to detect in the field. Adding a balun would needlessly complicate the design.

[@khalidgul786]

hello sir, thanks for the video.loved it.one thing i need to know is that i have lectrosonic Quad diversity system with UDM6 AND UDM6S rf distribution.i have been using this for almost 4 years. now its cables coming from udm6/6s are broke.please let me know what model are these cables(white coax cable),its specs and where can i get them.thanks

[@lectrosonics]

Please contact our Parts & Repair Department at [e-mail] and they can advise you.

[@simonbellemare2289]

"make it any length you want" ; isn't it a dB loss with length, especially for a small cable like this one? Thanks for the video, very clear, very effective!

[@lectrosonics]

Yes, a longer cable will begin to exhibit RF loss, especially if it is RG174 (the thin stuff). But for the purposes of a portable antenna for bag use, this is not a factor. For longer cables, it may be better to have a short antenna cable, and then an RF amplifier.

[@michaelbobarev]

🔥🔥🔥

[@cvideos9641]

How wide of a frequency range would you recommend for this? I have some wide band SMDWB's. Could I make one antenna to use, or should I make several on different "center" frequencies?

[@lectrosonics]

This type of antenna has about 100 MHz of bandwidth (3dB down points) so the 75 MHz tuning band of the SMWB type transmitters is well within that range. We recommend tuning the antenna to the middle of the band, so, for band A1, you would want the antenna tuned to about 500 MHz. We supply one whip antenna with these transmitters, for the A1 band we include a block 19 antenna, which is likewise tuned to the center of block 19 at about 500 MHz.

[@cvideos9641]

@@lectrosonics I am putting mics on some football players. Depending on the type of pads, sometimes the best mount is lower, or antenna down or sideways (which I know is not best). Looking to make some of these and tape it higher on the pads. Thoughts and suggestions are welcome.

[@lectrosonics]

Yes, the higher the better, and vertical for the last few inches if possible. These cable antennas give you (literally) much more flexibility for placement. And, they can be simply taped in place as long as you are not using metallic tape. Up on the back of the shoulders is probably the best location if you can get that.

[@cvideos9641]

@@lectrosonics exactly what I was thinking. thank you for the confirmation.

[@davidaliperti]

if using it on a receiver, like a UCR 411, are you using 2 of them or just one togheter the stock antenna?

[@lectrosonics]

Usually, best practice would be to use two of these antennas into the receiver, or into a distro for the group of receivers.

[@davidaliperti]

unfortunately, I've used a common tv antenna cable 75 Ohm, I don't get any problem in the rx-tx range with a walking test, can I use it normally?

[@lectrosonics]

If it works, it works. This setup will not cause any damage. However, it is not optimized and will likely not perform as well as the same receiver with proper 50 ohm antennas.

[@davidaliperti]

is the cable thickness an improving factor?

[@lectrosonics]

At these lengths, there is probably not a big difference between RG174 and RG58 for instance. However, if you were going to run a longer length cable (more than a few feet) then yes, lower loss cable would be important.

[@Greenjah81]

Question. Would this trick work same way for any other Transmitter/ Receiver of other companies as well as with standard BNC connector instead? Thanks.

[@lectrosonics]

Greenjah81 Yes, it does work for any radio device given it is made with the correct termination and the correct frequency band.

[@Greenjah81]

lectrosonics great, thanks a lot! I'm gonna give a try to my Comtek transmitter to extend the antenna.

[@simonbellemare2289]

half wavelength of a 216 comtek is 2,25 feet... a little bulky!

[@ElsonA9]

thank you

[@lisbom2001]

What would be gained by stripping the dielectric? Exposing the copper.

[@lectrosonics]

The copper shield must be "rolled back" to expose the center conductor, which then acts as an antenna.

[@lisbom2001]

@@lectrosonics yes I do get that this is half of the antenna (it’s ground plane) and should be down for proper impedance. The questions regards the dielectric insulator on the upper element. It appears you left it surrounding the copper. Would there be benefit on exposing the copper on the element instead of leaving it inside the dielectric as shown?

[@lectrosonics]

OK, understood. No, there would be no benefit to removing the dielectric, as it is transparent to RF. Keeping it in place will help keep the "antenna element" straight, and avoid oxidizing or damaging the copper conductors.

[@lisbom2001]

@@lectrosonics Thanks!

[@RoadJournal]

Nice Thanks!!!

[@thomasvanderbrook6444]

Here's the link: www.lectrosonics.com/US/phocadownload/ammkit_td.pdf