Wireless WIRELESS system with off brand antenna

[jtvd]

I have 16 Audio Technica 4000 series units, 8 in "C" band and 8 in "D" band with distros, sharing two of the Audio Technica unpowered fins without amplification (using 25 foot antenna cables). They are currently living in our sound booth, which is 50 feet from the front of the stage, and 75 feet from the back of the stage. the reason we set it up here, for now at least, was because we like having a quick view at battery levels and mic statuses.

We have been noticing some drops in the RF signal, it gets quite low sometimes - but we have not had any actual drop outs. Obviously the distance from the stage is not ideal, and i was thinking about mounting the wireless receivers side-stage, and mounting the antennas above the stage (about 20 feet above floor). in order to do this, we would have to run a 50' and a 100' antenna cable to the near/far side of the stage to mount the antennas to get a decent spread for diversity purposes (the stage is about 40 feet wide, but by the time the cable runs up, over, and down again those are approximate lengths) if mounting above the stage, would i want to use the directional fins? or will they be too directional at this shorter distance?

the only powered audio technica antennas i can find are filtered, so we would have to get two sets and mount 4 antennas and run two sets of cables. i was hoping to not spend $1500 on antenna mounting.

The audio technica in-line antenna amplifiers are also filtered, so again $1000+ for antenna mounting

Here is the real question - is RF, RF? or is Audio technica RF different than say Shure RF? Could we get two active Shure Antennas and use them with our current setup?

Does anyone have any other suggestions?

 

[Chris15]

RF is brand agnostic.
Only use preamplified antennas when you absolutely have to and have exhausted other options. They often cause more problems than they fix.

In your situation I'd be going for the 2 paddles a metre or two apart on the side of stage you intend to put the gear on. If say you go upstage and point from the corner across the stage you should stay reasonably within the lobe of the LPDA.

Remember too that an antenna is not blind to signals outside it's directional lobe, just less sensitive. If you increase the received power by being closer then it all evens out in varying proportions.

 

[waynehoskins]

RF is RF is RF. Antennas, feedlines, etc. aren't bound to any particular mode or encoding.

I agree that you shouldn't need to split your paddles to opposite sides of the stage in most cases; just get them far enough apart that there's some chance for diversity. My first thought would be upstage and downstage corners on the same side of stage, so that if there's multipath or an obstruction to one receiving antenna, you stand a decent chance of the other path not having the same problem.

If feedline loss is an issue, low-loss lines to consider are Times Microwave LMR-400 and Belden 9913 -- but for short runs with strong signals, even a line as lossy as RG-58 is often good enough.

 

[jtvd]

Awesome, thanks so much for your input! I will try putting the rack backstage and keeping the antennas on the same side of the stage as the rack.

 

[mbenonis]

Sounds like a plan to me. As Chris and other said, avoid active at all costs. All it will do is add to the noise floor and cause trouble.

If your runs get much longer than 25', go for something beefier for coax, like LMR 240 or LMR 400 or similar to reduce attenuation in the coax. RF is different than audio line, you lose a lot with even a bit of cable.

 

[jtvd]

Sounds like a plan to me. As Chris and other said, avoid active at all costs. All it will do is add to the noise floor and cause trouble.

If your runs get much longer than 25', go for something beefier for coax, like LMR 240 or LMR 400 or similar to reduce attenuation in the coax. RF is different than audio line, you lose a lot with even a bit of cable.

If the active antennas are so bad, why do they seem to be so popular? It seems most manufacturers produce them, even higher end companies like lectrosonic. is it a matter of most people not being able to use them correctly? or do even the high end ones have such problems?

 

[waynehoskins]

If the active antennas are so bad, why do they seem to be so popular? It seems most manufacturers produce them, even higher end companies like lectrosonic. is it a matter of most people not being able to use them correctly? or do even the high end ones have such problems?

If you have clear channels (and sufficient guard channels), there may be a theoretical advantage. The mast-mounted preamp will compensate for some line loss and path loss and make signals stronger (and in these cases, S/N is very high because the noise floor is very low, the noise floor of the first RF amp).

If there are interfering signals from outside -- co-channel weak TV station, in-band strong station, etc. -- which is pretty typical for most installations, the preamp won't help S/N ratio, and may even significantly increase the noise floor with interfering signals. Rather than maximum gain for maximum signal, you want lowest "noise". Moving the unamplified receiving antenna close to the transmitter significantly increases desired signal without increasing undesired signal (noise). Better S/N ratio this way and less chance for front-end overload from a strong in-band signal.

 

[Chris15]

Active antennas are good. But they are a tool and every tool has its correct and incorrect usages... All of the top tier manufacturers make them and in general the old you get what you pay for is going to be applicable.

IF you actually need amplification, then at the antenna is the best place for it, because the signal is at it's strongest it provides the best input to the sensitive front end of an active stage.

There *is* a reason why RF is (rightly) considered a dark art by many...