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  • Wireless Data Card Speed

    Curious about speed and throughput on the wireless cards. Is the reason that people see better speeds on the their laptops because there is usually software that is doing some sort of compression which fools the computer into thinking that it is getting 1.2Meg down and then when you switch to the Cell Router since it doesn't have the compression software when you do a speed test you get half the speed?

    We received our mb6800 yesterday and have been testing it with the verizon card we already have...the client will be installing AT&T Cingular with the Option 3.6 Max as you we will be curius to see what type of connection they get... we also will be putting a 3 watt amp (used to get the signal up 75ft of cable to the 4 ft Dual Band Digital Antenna. The antenna will actually be attached to a 8ft extension so the 4ft antenna will have 360 around the entire boat. Crossing fingers..... we are looking forward to seeing the MB9000..... I hope it does boat WiFi and Cell WAN bridging... and some way to easily configure which one when...

    Some interesting antenna's are out there to extend the connection to the hotspot..

    thank you for all your help

  • #2
    27dBm of fixed gain plus a 5dBi antenna! That?s a lot of radiated power. They show it with an omnidirectional dipole antenna ? I would recommend a directional antenna if using such a high power solutions. We have seen cases where too much transmit power actually kills the data rate due to multipath propagation/interference. Of course with 802.11n MIMO transceivers this would not be an issue.

    Good point on the compression thing although i doubt this is what you are seeing. What VZW aircard are you using? Are you in an EVDO Rev0, RevA market or 1xRTT? Do you have the latest firmware (I have seen sometimes people getting EVDO RevA speeds in laptop but not in mobile router until they update the firmware) .... Interestingly however, we have had many customers say the exact opposite: That having a cellular router actually improved their speed. We suspect this to do with spatial placement of the data card with the mobile router since theoretically the cellular router does steal some throughput albeit very little. Sprint is our number one choice for cellular data and Cingular is good too although the HSDPA nationwide footprint is much less than any of the EVDO providers.

    I trust that you have selected a really good low-loss coaxial cable since 75ft is pretty long and you can expect some severe signal attenuation.


    • #3
      Mobile router, cellular amplifier and antenna installation

      We installed all the equipment last week.... MB6800 -. Sierra AC860 -> adapter cable -> Digital Antenna Dualband PowerMax 3 Watt Amp -> 70ft LMR400 -> Digital Antenna 9dbi DualBand 4ft Antenna attached to a 8ft extension rod on the fly bridge. With the 8ft extension the 4ft did not have any obstruction in 360deg and it didn't start for about 3ft above the top of the boat. Because of our location I would have imagined that we would have been getting 5 bars with the AC860 card. But really I must say I do not feel we are getting any more out of the connection than without the external antenna connection.

      Something of note. We had a Verizon Card to test as well... and consistently we got 1.2Meg Down and 400-500 up... WITHOUT the antenna connection down under the helm of the boat (surprised me). The Cingular Sierra Card we never got anything over 500k up and 300 down... with and without the external antenna connection. There was next to no difference with with and without the MB6800.

      An easy way to test the whole antenna setup without having to spend $5,000on a TDR would be great!


      • #4
        Mobile cellular router & cellular amp installation issue

        Interesting. So no obvious overlooks like adding a single-band directional coupler on the path (this is actually quite common where people forget that the EDGE/HSDPA and 1xRTT/EVDO are in 2 different frequency bands and even after getting dual band amps & antennas insert some hardware in the signal path usually couplers that actually filter out one band).

        How does the RSS (Received Signal Strengh in dBm) look using the configuration software in the laptop. For Cingular: ?Cingular Communication Manager? ? ?Menu? ? ?Network? ? ?Signal Strength (dBm)? The RSSI (Received Signal Strength Indicator) circuits in these devices is not that accurate in absolute terms but is very good to check relative RSS i.e to compare the RSS with external antenna and without. Of course you will need to take the measurements several times and find average RSS due to the random nature of the propagation environment. If everything works well you expect some RSS improvement (NOTE however that the RSS is often not what you would intuitively expect. I.e it?s usually not tantamount to adding up the gains and substracting the insertion losses since these amplifiers do AGC, automatic gain control, to prevent receiver saturation).

        Lastly while measuring the RSS play with the antenna placement and orientation (well if you have an omnidirectional then that doesn?t matter). One thing to note is that some antennas require a ?infinite? ground plane for correct radiation characteristics e.g antennas designed for roof mounting. ?infinite? means the area of the ground plane must be much larger than the wavelength of the signal which in the worst case for 800MHz is ~ 37cm. Check the antenna datasheet.

        On the VZW i would bet they are using the 800MHz band at that location and probably the 1900MHz band for the Cingular ? just a conjecture. This would explain it since 800MHz has better propagation characteristics (larger wavelength hence much easily penetrates obstacles).


        • #5
          Single-band couple in dual band cellular amplier setup plus RF interference

          Single-band directional coupler on the path is something I was not I guess he answer would be no that could be a problem.

          The other issue that I just remembered is the fact that there is a TMobile Telex/PBX device in close proximity (within 4 ft of the amp under the helm)....and think it has an AMP and external Antenna connected to it which is probably about 10 ft from the Dual Band Antenna that we installed. (Could that be an issue?). I have asked the customer to provide some additional information to me. Because I believe I read where the PowerMax will backoff its power if it is too close to something else.

          We are using the name brand of "Digital Antenna" for both the AMP and the Antenna... their antenna's are supposed to understand ground plane and marine environments.

          Since the client has taken the boat up the coast...I can't see what the RSSI is any longer..but when they come back I will see.

          The biggest questions in my mind is the the directional coupler and TMobile interference.


          • #6
            power control of cellular amplifiers & interference rejection

            True power control is critical for cellular amplifier systems such that if the other amp is operating in the same band that might be a problem ? either it could drown out the other amp if its power is too much (through ACI adjacent-channel interference probably not co-channel interference) or it might cause the other amp to backoff too much. In general this would probably not a very serious issue and not very likely since Cingular and T-Mobile will most likely NOT be using the same channel/sub-channel. On the other hand however it depends on Digital Antennas output power control (since 4ft is very close) and I have seen reports where this output power control wasn?t that good (see 4.4.6 on ? caveat of course is that this is posted by their competitor and we too could be biased by the fact that we are a big Wilson dealer and only deal in low volume on the Digital Antenna stuff. All the same we realize that Digital Antenna would not allow this to be published if it was completely erroneous).

            On another note check out the MB9000. I just learnt from sales that we will be getting a shipment of these next week. Here?s the link: This is a really cool product since it can do multiple failovers (from multiple cellular data cards and Ethernet) and supports load balancing.


            • #7
              From this forums.... does his mean that the Sierra AC860 Card does not support EDGE connectivity on Cingular? Because I thought that HSDPA was only in Southern California right now.

              MB6800 Supported Aircards


              Supported PCMCIA Card List
              EVDO Rev. A:
              Sierra AC595; Novatel S720; Pantech PX-500r
              Sierra AC580, PC5220, Novatel V620, S620, XV620, Kyocera KPC650, Audiovox PC5740

              Sierra AC860, AC850, AC875, Novatel, U730, U740, XU870, Huawei E620, OPTION Trotter

              Novatel U530, U630, OPTION Fusion, GT Max, Vodafone Card

              Supported USB Modem
              Sierra Wireless AirCard 595U USB Modem
              Sprint PPC6700 phone


              • #8
                No it definitely supports EDGE. All HSDPA devices are backwards compatible to EDGE/GPRS. HSDPA to GPRS handoff takes place seamlessly (soft handoff) triggered by signal strength thresholds. I have seen however instances and discussions where a power cycling (or adapter disabling) is required to do the coverse i.e to switch from GPRS to HSdPA.

                Also this might be a bit outdated but you should have UMTS coverage in the following Florida cities (The AC860 supports UMTS and all UMTS markets have HSDPA but depending on RSS may revert to UMTS or simply EDGE)

                - Cape Canaveral
                - Clearwater
                - Coral Springs
                - Daytona
                - Ft. Lauderdale
                - Gainesville
                - Hialeah
                - Hollywood
                - Jacksonville
                - Lakeland
                - Melbourne
                - Miami
                - Miramar
                - Orlando
                - Pembroke Pines
                - St. Petersburg
                - Tallahassee
                - Tampa
                - West Palm Beach
                Attached Files
                Last edited by thuor; 09-03-2007, 06:55 PM.


                • #9
                  Answered my own question.... Digital said that their AMPs vary the connection based on the tower connection automatically.


                  • #10
                    Yes this is what i was alluding to in a previous post and actually is one area that Wilson beats Digital Antenna on i.e the handling of output power control.
                    See below:

                    Just an FYI related to this is the fact that looking at the datasheet you attached they claim the DA4000 Rx sensitivity is -125dBm yet the Sierra 860 aircard Rx sensitivity practically around -100dBm. An interesting note would be that without sufficient gain of an incoming signal the RSS is too small to be usable and the entire system is limited by the sensitivity of the EVDO data card.
                    Attached Files
                    Last edited by thuor; 09-03-2007, 08:03 PM.