What happens if you have a card with TX Output power 1Watt configured on RB433AH as ANtenna Mode : tx-a/rx-b which means (Antenna A is connected on TX OutPut [MAIN CONNECTOR] & Antenna B is connected on RX Output [AUX CONNECTOR] SAME CARD ) .

The 2 sectorial panels are directed to the same area!

Does that mean we are using Full Duplex Mode and does that double the antenna gain as 16dBi x 2 ?

What if we wanted to install 4 sectors 90degrees 17dBi directed in parallel using the same source card ( Same Frequency , Same SSID ) ?

Hope I get an answer or at least someone would guide me or at least comment .

Thank you

I think I have made it!

If we installed 2 antennas in parallel , the load will be splitted into 2 as here we are gaining dB not loosing because they are in the same direction .

The doubling of the output power means an increase in the signal.

Note the dichotomy:

· If the antennas point in different directions, there is a loss at the combiner.

· If the antennas point in the same direction, there is a gain at the combiner.

Let us say we have 2 sectorial antennas 16dBi x 2. 16 dB of this is just the adding of the second antenna, but the other 16 dB is from the combiner becoming a much more effective device.

Hope this helps somebody if he was intending to ask for it.

Regards,
Ghassan

If you stack two identical antenas you get just 3dB gain.

They would need to be stacked at the correct distance from each other and also they would need to have their feed lines the correct length. This is all needed to keep correct phasing of the signals.

You are not gaining anything as you are transmitting on only one antenna and only receiving on one antenna. Therefore the total increase in gain is zero. All you have is the gain of the antenna, minus the loss in cables etc of course. I.e. you gain nothing from this setup. Except some redundancy if one antenna fails, you can then switch to the one remaining one that is still working.

You are not working in full duplex as the same card is plugging into both antennae. There is still only the one card. You are still working in Simplex mode, except the RF goes out of one connector and returns back down the other.

Where is this combiner you suggest using? The two ports on the Mini-PCI card are connected via a Tx/Rx switching transistor, not a combiner. Or do you mean an external box?

If you use an external power combiner/splitter, then that device will have losses too (how much loss depends on what device you use and how well it's constructed) and every doubling of the antennae (of equal gain figures) only increases the gain by 3dB (minus losses of roughly 0.5 -> 1dB within the combiner, plus losses for the extra connectors, factor in between 0.1 and 0.5dB per connector).

If you have 4 antennae, pointing in all the same direction and they are all combined (only using one connector on the mini-pci card), then yes, you can get some benefit (some gain). But good quality, low loss combiners are not cheap and what is the point in pushing 1W into 4 antennae at 17dbi + 6dB gain - 1dB loss = 22dBi when the other end, the client only has a much lower power and a lower gain antenna to reply with?

Feeding multiple antenna, all pointing in the same direction is a useful technique for increasing the total system gain and has been used since at least the 1940's perhaps longer but at much lower frequencies! So nothing new there.

Also, by feeding the antennae together, in the same direction, it is very important to get the phasing right. This is incredibly difficuly at microwave frequencies. It is not just a matter of cutting all the cables the right length. Each cable will be required to be specially cut to length so that at the frequency being used, the phase of the RF arrives at the same time at each antenna.

Finally, by combining all those antennae together and obtaining your increased 22dBi gain, you will get a much tighter beamwidth. As they say, "you cannot get something for nothing". What you have "created" is a colinear antenna.

So, considering you started with 17dBi antennae and ended up with an expensive and complicated setup to get yourself an extra few dB, I would instead concentrate all the effort and time ensuring the client was getting a better connection back into the AP. Clients are often in poor locations, obstructed, badly aligned and having to use lower gain antenna and lower RF output powers as the customer does not like great big dishes on their roof.

You are not gaining anything as you are transmitting on only one antenna and only receiving on one antenna. Therefore the total increase in gain is zero. All you have is the gain of the antenna, minus the loss in cables etc of course. I.e. you gain nothing from this setup. Except some redundancy if one antenna fails, you can then switch to the one remaining one that is still working.

You are not working in full duplex as the same card is plugging into both antennae. There is still only the one card. You are still working in Simplex mode, except the RF goes out of one connector and returns back down the other.

Where is this combiner you suggest using? The two ports on the Mini-PCI card are connected via a Tx/Rx switching transistor, not a combiner. Or do you mean an external box?

If you use an external power combiner/splitter, then that device will have losses too (how much loss depends on what device you use and how well it's constructed) and every doubling of the antennae (of equal gain figures) only increases the gain by 3dB (minus losses of roughly 0.5 -> 1dB within the combiner, plus losses for the extra connectors, factor in between 0.1 and 0.5dB per connector).

If you have 4 antennae, pointing in all the same direction and they are all combined (only using one connector on the mini-pci card), then yes, you can get some benefit (some gain). But good quality, low loss combiners are not cheap and what is the point in pushing 1W into 4 antennae at 17dbi + 6dB gain - 1dB loss = 22dBi when the other end, the client only has a much lower power and a lower gain antenna to reply with?

Feeding multiple antenna, all pointing in the same direction is a useful technique for increasing the total system gain and has been used since at least the 1940's perhaps longer but at much lower frequencies! So nothing new there.

Also, by feeding the antennae together, in the same direction, it is very important to get the phasing right. This is incredibly difficuly at microwave frequencies. It is not just a matter of cutting all the cables the right length. Each cable will be required to be specially cut to length so that at the frequency being used, the phase of the RF arrives at the same time at each antenna.

Finally, by combining all those antennae together and obtaining your increased 22dBi gain, you will get a much tighter beamwidth. As they say, "you cannot get something for nothing". What you have "created" is a colinear antenna.

So, considering you started with 17dBi antennae and ended up with an expensive and complicated setup to get yourself an extra few dB, I would instead concentrate all the effort and time ensuring the client was getting a better connection back into the AP. Clients are often in poor locations, obstructed, badly aligned and having to use lower gain antenna and lower RF output powers as the customer does not like great big dishes on their roof.

That's true but I was wondering howcome 2 antennas pointed at the same direction would have only few db Gain whether its 17dbi or 9dbi . I thought it would give a higher db gain since we have 17dbi Sectorial Antenna compared to small antennas and I knew it would be an expensive idea to avoid installing expensive devices at customer's side.

For example we have installed 5Watts TX Power Amplifier which does not allow Bi-Directional using the same antenna thats why I thought to install 2 antennas ( first sector connecting to the TX Amplifier & the second sectorial antenna is connected directly to the same source card) because the Amplifier was built to Boost only Transmit Signal from the station .

Whats the idea of connecting 2 sectorial antennas directly to the same source card as in RB software it has Antenna Mode as "tx-a/rx-b" ?

Our idea was to allow customers connect to us using a very cheap devices knowing that we are going to pay for expensive systems which makes us to reach at least 30% NLOS in our area since we are working on 2.3GHz band although we are going to boost the RX Sensitivity which grant us a total gain within 2km "60dB" .

Regarding the noise .. Im sure we are going to hit more noise and in this case I dont know if BPF would help here .

What would you recommend us in this case ?

Thanks for your information

Regards,
Ghassan

Biggest thing I could recommend is to throw away the Power Amplifiers.

You don't get more than 3dB gain when doubling up the antennae (of same gain) because that's how Logarithms work!

Ghassan, ti simply does not work that way.

If you use two antennas for separate RX and TX you must do so on both sides of a link and then you will use one channel for RS and other ofr RX. That will give you much higher link speed.

If you want higher gain in antenna then use antenna with higher gain: instead of 16dB sector use 24 db directional antenna. But, count on reducing radiation angle.

However, whole idea you are chasing is wrong. It is not point ot get higher gain as that would lead to line of other problems. If you want to allow clients to conenct with cheap equipment meaning devices with small factory antennas, you have to get closer to that clients. Use additional access nodes for that.

The main use I have seen for TX-A/RX-B is to flex some of the FCC (and possibly other governing bodies) regulations. FCC regulations only limit the output power of the transmitter, it does not cover the receiver.

To stay under the legal power, you might be limited to a 23dBi directional in a theoretical example. However, you could use a 23dBi grid on the TX, but a 36dBi on the RX. So by using asymmetrical TX/RX antennas on both sides, you can use smaller TX antennas to stay under transmit limitations, while having the increased receive sensitivity of the larger antennas.

That said, it's still probably not advisable to set up a link this way, but sometimes we do what we have to.

The main use I have seen for TX-A/RX-B is to flex some of the FCC (and possibly other governing bodies) regulations. FCC regulations only limit the output power of the transmitter, it does not cover the receiver.

To stay under the legal power, you might be limited to a 23dBi directional in a theoretical example. However, you could use a 23dBi grid on the TX, but a 36dBi on the RX. So by using asymmetrical TX/RX antennas on both sides, you can use smaller TX antennas to stay under transmit limitations, while having the increased receive sensitivity of the larger antennas.

That said, it's still probably not advisable to set up a link this way, but sometimes we do what we have to.

My main use of Sector antennas is to have PTMP . I dont want my clients to use bigger antennas as we are assuming our products might be using antennas from 4 dBi ~ 10dBi Omni Antennas connected directly using cheap products like DWL-2100AP as well as we have our main station transmitting higher power With a very low noise amplifier meeting the RX Sensitivity ( pushing the Noise from -80dBm to -99.7 dBm ).

We cant transmit our signal through GRID which is 25 degrees antenna 23dB thats why we are using Sector Antennas to cover the angel 90 degress knowing that 60 degrees is much better to avoid noise from others operating on channel 2.3GHz BAND .. To avoid the noise we had to apply Band Pass Filter for only one channel since no one is using this channel!!!.

At least we are expanding our coverage or extending the NLOS percentage.