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Old May 13th, 2008, 09:47 PM   #1
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Aux antenna for wireless

To start thank you all for the terrific education I have gotten here. My equipment is not up to professional standards by a long shot, but I know the difference. In fact using a SD MixPre, and Sennheiser G2's and an AT 4073 has been an illuminating experience..... but those are not mine.

My question relates to adding an aux antenna to a VHF set of AT Pro88W's. These little wireless mics are (in my ignorant and humble opinion) a pretty good bang for the buck....

I see that the high end UHF wireless mics offer aux antennas. I also noted a tip on another website that adding a BNC in place of the antenna and then connecting "a high antenna system, such as a dipole or Yagi, to attach to the BNC."

I'm pretty handy and internet savvy but I cannot come up with something matching that notion... anyone seen something or can offer any ideas ? DIY or buy? Thanks!
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Old May 14th, 2008, 04:26 AM   #2
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Quote:
Originally Posted by Chris Swanberg View Post
To start thank you all for the terrific education I have gotten here. My equipment is not up to professional standards by a long shot, but I know the difference. In fact using a SD MixPre, and Sennheiser G2's and an AT 4073 has been an illuminating experience..... but those are not mine.

My question relates to adding an aux antenna to a VHF set of AT Pro88W's. These little wireless mics are (in my ignorant and humble opinion) a pretty good bang for the buck....

I see that the high end UHF wireless mics offer aux antennas. I also noted a tip on another website that adding a BNC in place of the antenna and then connecting "a high antenna system, such as a dipole or Yagi, to attach to the BNC."

I'm pretty handy and internet savvy but I cannot come up with something matching that notion... anyone seen something or can offer any ideas ? DIY or buy? Thanks!
What part - how to add the BNC to the receiver or what a "dipole" or "yagi" are?

Perhaps someone else knows about external antenna available for VHF but there's a good chance there just aren't any on the market since most pros are using UHF these days. But they're not that hard to DIY out of aluminum rods and plastic barstock. The ARRL (Amateur Radio Relay League) has a number of publications that would have all the details and equations you'd need.
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Old May 14th, 2008, 09:36 AM   #3
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I think you probably mean "high gain" rather than just "high" but height can be a benefit too. If you pick up 6 dB of antenna gain (at either end) you should be able to double the range of the set. 6 dB at each end would allow 4 times the range ceteris paribus (by which I mean line of sight in all cases i.e. you can't go behind a metal barn, on the other side of a thicket of trees etc.). 6 dB is a reasonable amount of gain for a VHF antenna of reaasonable size (and that means fairly large as the wavelengths are long: 2-6 meters with antennas about half that size in the VHF band). Thus they are much more practical at the base (recorder) end than the talent end where they are totally impractical. As the VHF (and UHF) frequencies used fall within television channels it stands to reason that a TV antenna is probably the cheapest and quickest route to an antenna in this frequency range if you can still buy the things. Several problems remain. You need to connect the antenna to the radio equipment. If the radio equipment has BNC's then you are most of the way there but you will still require a balun. TV antennas are, or were, 300 ohms balanced while the sets were 70 ohms unballanced and most receivers are probably 70 ohms unballanced (as that's the impedance of a quarter wave whip) but could be 50. Adapters between the connector on the balun and the connector on the radio equipment may be required.

Other alternatives to TV antennas can be found in radio supply company catalogues (Yagi's) and, to a lesser extent, ham radio catalogues (log periodics). It is possible to build either but it's non trivial and takes special equipment (vswr meter) to tune them. Yagis have higher gain but are narrow band. Log periodics are broad band and larger but have somewhat lower gain for a given size. Both are directional - they get their gain by receiving from a smaller area and this must be kept in mind. They must be pointed in the general direction of the transmitter (though not that precisely). TV antennas are the same.

Dipoles are not directional but have unappreciable gain relative to the simple whips with which these units ship and are thus not worthy of consideration

Last edited by A. J. deLange; May 14th, 2008 at 09:38 AM. Reason: Fat fingers
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Old May 15th, 2008, 12:35 AM   #4
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Thanks for the replies. What I had kind of settled on in my attempts to understand was that I could hook up an inexpensive mast mount tv antenna and get better reception..... but something that size seems to defeat the purpose in the first place....

In my PollyAnnish little world I imagined some oddball off the shelf little antenna that was a magic thing when used in this fashion.

I also figured that a set top dipole was pretty much what I already had....

No harm in asking I suppose.
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