External antenna for Clear CPE25150

[thuor]

Have been getting lot's of questions about using the 16dBi 2.5GHz directional panel antenna or the omnidirectional antenna for this CPE modem so wanted to post some clarifying comments here:

1. Unfortunately this modem as well as the CPEi150 modems DO NOT have an external antenna port as the Zyxel MAX-206M2 does. Instead it has a 7.17dBi internal slot antenna.
   
2. It does have external antenna posts on the PCB as shown on the image below:
   
   
   
   Not quite sure yet what the antenna type is that they are using.
   
3. While it is definitely doable it's not a trivial feat to solder on an external antenna. For one you cannot just simply solder the antenna wires but rather you could solder on an SMA adapter. The reason is that at high frequencies (and 2.6 GHz is kinda high) you absolutely have to match the output impedance of the connector (which is typically 50 Ohms) otherwise impedance mismatch will cause significant losses. More importantly a "wire" or trace in RF becomes a transmission line and with a transmission line you have to take care of the both forward gain, reverse gain (or reverse isolation). On the receive end this would severly distort the noise-figure of the input LNA (low-noise amplifier) which is tantamount to degrading the receiver sensitivity which would actually make the radio performance worse than before. In summary: VERY BAD things would happen ---- if you do succeed in cleanly doing this (remember this voids the warranty too) be sure to hook up a really high gain antenna to compensate for these loses.
   
4. Again we are not quite sure where these external antenna posts exist here and not on the package. In general there are several reasons for this;
   1. most typical reason is to make sure that the users do not add an external antenna that would cause the EIRP to go outside regulatory or network-design limits or the input power to go outside the input dynamic range. Both bad! This modem is spec'd for a 7dBi and the FCC test report show an output power of 27.4dBm at 2.6GHz and 10MHz channel bandwidth which gives an EIRP of about 34dBm.
   2. sometimes this is just a factory test port and as such might be enabled by a special testmode on the driver circuit
   3. sometimes this a design gone bad. When i was doing integrated circuit design we used to call these "features" when an intended function is broken but we still release the product with these functions conveniently removed.
   4. this could also be something that will be enabled in a new revision
   
   

At this point we haven't attached any antenna to this to figure out if we can boost the reception. We also don't yet have any conclusive results on the coupled-antenna adapter but we will update that post when we learn more.

If anyone has positive results on this please do share.

[25draker]

Good thanks thour for this info and thanks for clarifying about soldering to an antenna post as my friend was just about to do just this and a lot of people actually don't realize electronics works very differently at high frequency.

could they be using SSMA (miniature Sub-SMA) since from the FCC test reports they connect the EUT (equipment under test) directly to the Spectrum analyzer through a 10dB attenuator 50HF-010-SMA.

[thuor]

Not sure. These SA attenuators typically use standard SMA and this clearly not a standard SMA so they most likely have an adapter since the DUT is physically attached to the Agilent Spectrum Analyzer for these ACPR tests.


Update 10/9/2010: See https://forums.rfwel.com/node/1225 for update on Antenna connector switch for CPEi 25150 and CPEi 725 - Clear Series M.

[matt21252]

Possible solution to external antenna

If you were a former xohm user and forced into clearwire and still have your home modem, the zyxel modem... the internal antennas have the same connectors as the motorola clearwire modem. I'm kinda surprised it hasn't been brought up... so use the zyxel old intenal as an external or clip the connectors and build your own, or simply clip then add wire to them to extend them....

[KiltBoy]

External antenna for Clear CPE25150

Hi,

Have there been any reports related to the use of 'coupled antenna adapter' when used with the Clear CPE25150 Modem?

Steve

[Petro5]

Yes and unfortunately this doesn't work reliably. The only success has been with modifying the device to add an external antenna connector as matt21252 correctly pointed out - thanks matt.

By far the best success we have had is with the Clear 4G USB modem since this does have an external antenna port. Here is the antenna kit for that: http://www.rfwel.com/shop/?target=pr...roduct_id=1935 or if you want just the antenna pigtail: http://www.rfwel.com/shop/?target=pr...roduct_id=1934. If you need to share this modem with other computers on your LAN or WLAN you can always hook it up to a wimax 3g/4g router such as the Cradlepoint MBR900.

Here is an example drawing on how you could hook this up to a MBR1000 router:

http://www.rfwel.com/support/tech-drawings/Clear_4G_USB_Outdoor_Directional_MIMO.pdf

We do carry WiMax Outdoor CPE's or Indoor CPE's with external antenna ports but unfortunately Clearwire still doesn't allow activation of modems other than what it sells (as of 5/21/10) despite the fact that this are Wave2 Compliant certified devices. This is a bummer considering WiMax was touted to become an "Open-Access" network.

[Chris214]

has anyone had any real success with using an external antenna on the cpe25150. If so what where they specifically and what method was used. I will try a few things once my parts get in and will give an update in about a week.
-chris

[gapon]

any succes with CPE?

[chiti]

yes use this pigtail http://www.rfwel.com/shop/8-N-Female...e-Pigtail.html with this kit http://www.rfwel.com/shop/4G-USB-Mod...tenna-Kit.html


Update 10/9/2010: See https://forums.rfwel.com/node/1225 for update on Antenna connector switch for CPEi 25150 and CPEi 725 - Clear Series M. The U.FL pigtail is for the Gemtek WIXB-175 Series G modem.

[Gadzooks]

Chiti,

you reference that pigtail, but I wanted to know if I will need to have 2 of the pigtails and 2 antennas since the Gemtek CPE has 2 antenna connections on the pcb? Is there a pigtail that would have 2 u.fl connectors that connect to one N-male? I am not sure if I would be able to get away with just having one. I have been struggling to get better antennas on the motorola cpe 250 and have had horrible luck.

[bschoenbaechler]

has anyone had any real success with using an external antenna on the cpe25150. If so what where they specifically and what method was used. I will try a few things once my parts get in and will give an update in about a week.
-chris

Chris any luck getting this setup to work? I have mine installed and get a better signal with out the antenna than with it. I am using 100 feet of cable.

Does anyone think that I could be losing signal through the cable run?

[chiti]

You can use just one. Depends on how terrible your signal is. If you use one put it on the primary side and leave the auxiliary antenna connection connected. This has to do with MIMO (Multi Input, Multi Output) which uses multiple transmit antennas at the wimax basestation and multiple receive antennas at the radio modem. Because of this it really doesn't make sense to use a single cable with a splitter/combiner.

thuor in this forums gives a good explanation when MIMO works best and how to decide when you need it most. my opinion is to use trial and error - start with one antenna and if you still dont see results get a 2nd one.

but be realistic in ur expectations though. the antenna is passive (not an amplifier - no power input) so if your signal is very very weak no amount of antenna would help - would be below noise floor so adding antenna would not improve the signal-to-noise ratio.

good luck!

[gapon]

what i need to do to with pigtail, give me some instrucrion please, thanks

[Petro5]

Chris any luck getting this setup to work? I have mine installed and get a better signal with out the antenna than with it. I am using 100 feet of cable.

Does anyone think that I could be losing signal through the cable run?
Edit/Delete Message

Possibly. Depends on what your starting received signal strength and what type of cable & antenna you have. Be sure you are using the right cable for this frequency range. If you are using LMR400 cable then at 2.6GHz the cable loss is 6.9dB/100ft. Any less performance cable not recommended for this frequency band and distance - i have seen people try to use lmr200 or rg58 cable at this frequency and range and losses would be more than the antenna gain.

Assuming you have the correct cable and a powerful enough antenna > 12dBi this could have to do with loss of MIMO diversity gain. So for example if you are comparing one outdoor antenna vs taking modem outdoors then in the latter case you actually have two internal antennas picking up the stronger outdoor signals (so MIMO is helping) and in the former case you only have the outdoor antenna picking up the stronger signal but the 2nd integrated antenna that is not connected to an external antenna is hardly picking up anything indoors. To verify this what we have people try out is to put the modem outdoors but connect the primary antenna with the same 100ft cable. This should perform better than putting the modem outdoors without any antennas which tells us that MIMO diversity is helping in this case. Knowing this the solution then becomes to add a 2nd outdoor antenna and another 100ft cable.

2nd antenna should be oriented away from primary to ensure that the MIMO channels are as uncorrelated as possible which is where MIMO diversity coding works best. If location is surrounded by multiple towers and equally strong signals arriving from multiple directions you could use an omnidirectional auxiliary antenna such as in this setup: http://www.rfwel.com/support/tech-dr...l_Antennas.pdf This also gives you better redundancy when the primary path (dominant signal path) fails.

[chiti]

what i need to do to with pigtail, give me some instrucrion please, thanks

Open up the PCB. Disconnect cable going into jumper J2 and J3 (this cables lead to the printed pcb antennas). Replace with this pigtails. connect pigtails to low loss coaxial cable with an n-male end (since this pigrail is n-female). Connect an outdoor antenna to the end of the cable. so you need three things: pigtail, cable, antenna.