Negative Antenna Gain for Audio Limited A10 ? (and digital systems in general)

[LuisT]

Hello,

 

is anyone using negative gain on their LPDA antenna's while using Audio LTD A10 Systems?

 

What are your settings? And what distro are you using?

 

 

I am wondering if that could be beneficial for even better range cause they tend to RF overload easily.

 

I am occasionally getting noise issues on ssm's while the A10 are on and too close to the antenna's. (Shielded CINELA osix for booms)

 

The Antennas are Wisycom LFA and the distri BSRF AS122. 0db Gain.

 

Thanks for your real life feedbacks.

 

Cheers

[LuisT]

Anyone ?

[rich]

i dont use negative gain on my LPDAs, though often, i only have the gain set at 6dB whilst my antenna cables have about 10dB of loss.

its always a good idea to not have any transmitters close to your receivers, but you arent wrong that digital radios seem to be more sensitive to it.

if you are having noise issues with your SSMs, it may be a shielding issue you have rather than an antenna gain issues.

in what situation do you get the noise issues? and what specifically is the noise?
an increase in white noise could be digital rf. 

splats and pops could be frequency related, or de-sensing.

[LuisT]

increase in white noise when talking only. Probably digital RF

[rich]

if it's not constant, then it may not be digital rf.

are you able to test without the A10s?

or at least recreate the situation where you get your white noise whilst talking only?

[LuisT]

I did yesterday. The problem occurs only inside, never outside.

 

I am thinking that even with 0db Gain, frequency planning and scan, some multi path reflections inside can happen, causing the distro to RF overload on a super small and random amount.

 

And this gives the white noise whilst talking on the ssm's only WHEN the A10 is on. When the A10 is off, the problem goes away.

Interesting fact, if i space even more the A10 (they are B Band), the problem goes away.

 

I would like to try omni antenna inside when it happens. It's possible that the extra 7 dbi of gain of the LPDA when in Axis is boosting the overall RF.

 

Also, the white noise changes depending of RF power of the A10 (low/med/high).

 

Without the A10 no problem. The ssm's are rock solid since years.

 

I tried to recreate a RF overload inside by boosting the antenna a bit on purpose and this exact problem happens. Thats why i am thinking the A10 can perturbate the RF front end of the lectro SRC.

 

 

[Matthew Steel]

Have you tried changing frequencies to see if it makes any difference?  And of course, have you run an intermodulation calculation on your frequencies?

[LuisT]

Yes. When keeping the 518-542 mhz window it usually comes back. When setting the A10 beetween 580 and 600 Mhz the problem goes away. (discovered that yesterday)

 

But i mean even 20 Mhz separation should be plenty enough!

[MMS Inc]

Hi Luis!

 

I'm curious how your antennas are routed?  Are you going into the SRC and A10 RX through an SL2/6 or another rack mounted antenna distro?  

 

PM