I’m interested if any of you found a way to combine two (MIMO) radios into one (MIMO) antenna?
I really like the idea what Mimosa B5(c) do: have two radios, and they share single antenna.
Since the radios are sync’d together, they can work in nearby freqs too.
I know, its possible to have a board with 2 radios (like NetMetal or 912/922 boards) and one MIMO antenna on each to bonding or setting to “full duplex” with OSPF,
so one link work as TX and another in RX. But any possiblity to save antenna space (without huge RF loss) ?
If that would work, in dense areas would be much easier to find 2x20MHz channel then one 1x40MHz channel (not to talk about 80MHz), so would be nice
for 5G backhauls.
scampbell: your idea is not working because that is a low band (2.4G) and hi band (5G) filter inside.
Ndor: yes, i can be done with bandpass filter - but that would really limit the usage.
For example: radio port1 filtered to 5500-5650
radio port2 filtered to 5750-5900
Again: Mimosa connect 2 radios onto 1 antenna. Those radios can work in very near freqs, like
radio1: rx on 5500-5540
radio2: tx on 5550-5590
both radios can be tx or rx only, or both can be bidirectional.
Also, there is a multiplexer for Ubiquiti AirFiber: AF-4x4 or 8x8 (2 or 4 radios connected).
(2 radio - 4dB insertion loss, 4 radio - 8dB insertion loss)
Syncing of radios are a must for this i think - without that, you have to have big isolation between radios. But with proper sync - local radio will not transmit when other local radios receive - so will not interfering ownself.
With the effort that would be required to get this project operational and no guarantee of performance improvement, possible RF interference side effects to other wireless devices on site,
also remember reading ( can’t find the post now but may search again later..) that an issue could occur with return IP packets coming back being dropped, packet marks having to used on both sides of the link this results in higher CPU load… in short as a WISP I would if possible use frequencies outside 5Ghz band for backhaul.
Why?
Within few kilometers - p2p with two 1foot dishes are more than OK. Sometimes, i rather use 2foot dish in small distance for narrower beam.
If i can double the thruput on cost of adding one more radio to my device (like netmetal) (or have 2 radios integrated like mimosa b5c) than i would do.
If i have to use 3foot dish instead of 2foot - on a 10km link - that’s no problem for anyone, i think…
Interference is always possible in ISM…
A pair of netmetal costs ~250EUR.
A pair of Mimosa costs ~500EUR
A pair of Infinet 2x2 link costs ~1500EUR - that one changes channels without your interaction, without disruption (Like Cambium PTP600/650)
A pair of a 24GHz link costs like ~3000EUR
Sadly ISM @10GHz is not allowed here, and 11GHz is expensive on monthly freq fee…
While its possible to run a combiner and utilize a single antenna I have only ever seen it employed when people are backed into a corner (No available space on tower to add additional antennas etc).
Its generally expensive.
You lose a considerable amount of power with a combiner. Generally this means that the equipment is cranked up pretty high to compensate for losses encountered with the combiner.
You will sometimes see Analog FM transmitters and HD radio transmitters sharing an antenna if they did not want to spend the cash on a hybrid transmitter. But you don’t even want to know the costs involved in that…
Well, mounting two big dishes on each side (especially if it’s relay point) it’s not so easy in most situations.
What are really interesting in Infinet 2x2 (and Cambium PTP600/650) is they can scan the whole spectrum while communicating. If jumping to different freq is needed, they can
discuss it, and re-connect immediately without packet loss. For this, no sync is needed.
If Mikrotik would be able to do this, that would be a great jump.
What could be a really good idea is combining NStreme-Dual with MIMO and Sync, and connect the two radios to one antenna (with single polarity).
Both card do the TX in the same time, and RX in the same time - or even one card to TX only, another RX only.
This can be full-duplex (so better for TCP), also much easier to found 2x20MHz free channel, than 1x40MHz. especially find the same 40MHz on both sides…
I’m sure, if any vendor do that in the sub 1K value (per link) for 5GHz, they will have a huge sale on that. The future is freq reusing, i think.
From this I assumed available antenna mast space was an issue?
If you had -4dB and -8dB insertion loss between radio and antenna you wouldn’t be able to reduce radio RF power
“..It is a Full-Outdoor and Full-Duplex microwave link operating in the 17 and 24 GHz license-free band. The hybrid radio transmits/receives on one channel in the 17 GHz band and on the second channel in the 24 GHz band. This microwave solution with the bandwidth up to 160 MHz allows higher transmission speed over a much longer distance in the free band..”
Your post is very interesting. I would be pleased if you can share me some prices (mostly for 24GHz, not the hybrid). Sadly 17GHz is not allowed in Hungary, nor 12km is allowed to use with 24GHz with the needed EIRP. (i know, using 5GHz for 20km also not allowed
The bandpass filtre will not limit the spectrum in that case.
Take your example: radio 1 - 5500 - 5750 and radio 2 - 5550 - 5590.
That means you need a 150 Mhz bandpass filtre for each radio port . If we choose the channel set at 40 Mhz , it can be seen clearly that we have space insside for 3 (3.75) radio channels , every 40 Mhz ,and we can set the Rx or Tx ,without interference between them. The advantage of such setup, can be compatible with any equipment .
We can’t compare with equipments which has been designed from the beginning with filters insside them like Mimosa or AirFiber 5x.
The UBNT multiplexer NxN 4, is nothing more than a hybrid coupler and cannot operate with anything else than AirFiber 5 .
But, with a hybrid coupler and bandpass filters we can do the same thing with any other equipment .
And, -4 dB means nothing when it is known this thing from the beginning, and will take into account when calculate the link.
In fact ,I observe that Netmetal has 31 dBm in Tx and AirFiber 5x has only 26 dBm in Tx. Netmetal advantage, if you want to use them in such setup .
You can do full duplex link with one antenna and two wifi cards with that , without any problems.
Yes, that UBNT coupler is like ~20USD. Since you have to have same fw version, and configuration done before assembling the units, everything is done in the radio, firmware with GPS sync.
I’m pretty sure, it could be done within one Mikrotik device with 2 cards inside (even without GPS sync source) only with software.
It would be great if full duplex can be achieved with using a single antenna but as vendors don’t offer such a product for Mikrotik, it must not be as simple to achieve or is financially prohibitive.
Vendors do not offer? As I know, RF elements wanted to build a device together with Mikrotik to totally eliminate the need of RF cable, sadly that product did not born…
Since the TwistPort horn (or parabolic) antennas has no polarisation - I think - one device could have 4 antennas: horizontal+vertical and same with 45degree twist. (slant)
Mikrotik really needs to have a professional antenna manufacturer partner that could develop wireless products to a very high level !
(In other words this partnership would develop products for the WISP market and not general wireless)
As regards "TwistPort horn (or parabolic) antennas has no polarisation " that is correct until you insert/attach an radiating element(s) then it becomes polarised.
Yes. Do you know the twistport cage for RB922 board ? It has a “daughterboard” connected with MMCX cable.
What they wanted to have is a “twistport” version of SXT, what has radiating element(s) in the middle of the board what goes thru the horn - without any cables.
Sadly all manufacturer need to have an adapter - except UBNT who cloned the horn for themselves.
