Last Post: February 15, 2012:
In case of using radiating cables, the max Tx power of the AP in Europe is always 20dBm? I'm wondeering if I could configure 23 dBm as tx power since the coupling loss is too high...
Thanks and regards,
I had written a fairly long reponse to this question, but somehow my Login credentials were lost between my starting and ending it, so my reply was lost.
In a nutshell:
1. I doubt you will have that much loss if you have good connections.
2. Ask the cable manufacturer for their Application notes.
3. Get trained on installing this kind of cable. I have heard it is not very forgiving - minimum cable bend
radius, etc is VERY important. And improper bends in well shielded cables can cause big losses, due to reduced shield effectiveness and increased impedance.
Yep 20dBm at the eirp. I always thought it was 17dBm in etsi.
Ok thanks both!
As far as I know the losses are very huge with radiating cables. In fact, considering the 2.4Ghz band, besides a longitudinal loss of around 16dB/100m, you should take into account around 70dB of an immediate coupling loss.
So for example roughly at 100m away you get 20dBm (Tx pwr) - (70 + 16) losses = -66dBm received signal strength.
For such a reason I was wondering if it was allowed a tx power higher than the standard eirp limit for europe (+20dBm).
Again, talk to the manufacturer and a professional installation company, and see what they do.
I'm sure that post installation site surveys will be different too.
Yes, I'd like to speak with the manufacturer but unfortunately I don't have his contacts.
Basically I need to perform a post installation audit (wireless site survey and check of the configuration). In such installation there are a couple of APs installed with radiating cables and the tx power of the AP has been set up at 23dBm. Without knowing the manufacturer, I believe that if there is a tx power or eirp limit on the AP equals to 20dBm (as standard wifi installations in Europe), this should be the same whatever radiating cable model you're using...that's the reason why I've raised this question.
I think you may be confusing the various factors involved. Coupling loss is the field strength leaking out of the cable.
Leaky coax would not work at all if the losses were as bad as those you calculate.
The numbers you quote for loss per 100m also seem high. Times Microwave have cables that do much better.
I suggest you get a copy of a related test standard, such as IEC 61196-4, to get the definitions clarified, and then re-do your estimates.
Thanks for your suggestion but I know exactly what's the coupling and longitudinal loss. If you can't help me don't worry, there will be someone else in the forum that probably can give me a better advice.
Of course there are other manufactures with slightly different longitudinal and coupling loss but at the 2400 Mhz the calculation listed above to compute the total loss should not be wrong.
Let's wait for the opinions of the other members of the forum.