Deploying a Moving Mobile Repeater Long Term


This is a guide and installation document for a permanent mobile repeater installation with tips on the gotchas involved and how to minimize falling off the IPSC network for the least frustrating experience.

Mobile repeater Manager   --  Repeater in a Box


There are a number of considerations to address in a networked mobile repeater as well as what the repeater owner wishes to accomplish after deploying the repeater.  No matter how simple or complex the needs, all installations will need a minimum of the following:

  • TRBO repeater (1-25 watt low power likely preferred with fan mod)

  • Cellular data service (hotspot, phone tether, router)

  • 12VDC in the vehicle (cigarette lighter, direct to battery)

From this simple list, one can add additional components to accomplish much more:

  • 0, 1 or 2 antennas (no antennas are actually "needed")

  • Duplexer (flat pack preferred, simple and cheap)

  • Battery back-up (other than primary start battery for vehicle)

  • Flexible 12 VDC power-pole distribution/ management with battery re-charging while in motion

  • 110 AC provisioning for long deployment cycles and quick recharging of the batteries

  • Laptop/tablet/phone use while in vehicle, stationary or in motion (for passengers not the driver)

What you choose to use will likely be driven by what your "needs" are as well as their associated costs to deploy a networked mobile repeater.  If all you need is to have a networked repeater while you are driving or stopped for a restaurant or other short periods out of the car with needs to provide HT access, then the short list above can work adequately.

At the other end of the scale are deployments that must run 7/24, higher RF levels for larger coverage areas, Internet access to multiple devices or to service public service events, EMCOMM, civil emergencies, search and rescue, ham conventions where you must get into the arena, shopping mall excursions or trailhead hiking.  Disclaimer:  We don't know it all, so don't trust us with your time and money and if you know more, how to do it better, please let us know so that we can incorporate it here so that it can benefit those who may come after us.

From this point on, all information provided will be from this installation perspective based on what we want from this repeater.  Some notes will be added to help in other common areas as well in order to help others who have somewhat different goals.  We have done this 3 times for over 7,000 miles and have consulted with another hardy soul who has deployed multiple times for several thousand miles.

OUR GOALS: 

  • Semi-permanent, full time repeater, low power RF output

  • Best RF cellular coverage, moving mobile network connected repeater

  • Reasonable stationary HT coverage and duration.

CONSIDERATIONS:

  • Easy movement to and use in another vehicle

  • Low consumption of data and 12 volt power

  • Use of data connection for other devices; computer, tablet, phone via Ethernet and/or WiFi

  • c-Bridge manager, ideally programmed for only 1 mobile repeater resident at any 1 time

  • Least amount of irritation  to passengers from repeater noise in the cab of the vehicle

OUR BASIC EQUIPMENT:

  • Low power 1-25 watt UHF XPR-8300 with Fan Mods (more on the mods later), flat-pack duplexer, UHF NMO spike on roof

  • Cradlepoint MBR95; 4G/3G/Cable/DSL, 4 port WiFi router with support USB Cellular Modem with failover support

  • Verizon USB Modem (Pantech UML295) dongle style, diversity antennas with 2 external antenna ports, 2 4G/3G NMO gainers on roof

  • 12 volt power, harnesses/cabling for repeater, router, and battery, with handy switches

 

So having set the stage for this project, let's move on to the nuts-n-bolts needed and the details to make it all happen.

IPSC Network Master:  This is important.  You should (must or ideally) deploy your repeater on an IPSC network that is running a physical master repeater with few to no other peer repeaters.  This is likely not going to happen with most IPSC networks. So...next best and much more likely...

If your network is using a c-Bridge or SmartPTT as a master, then your results may be less robust.  It appears that the 3rd party solutions are not as compatible to a mobile deployment as is a real TRBO Master repeater.   We feel this is due to both varying IP's and UDP ports that are constantly changing as data connection hands-off to different cell site groups or regions.  The physical MotoTRBO repeaters appears to handle these dynamic conditions in peer repeaters far better and faster which keeps your repeater on the network much more consistently than a 3rd party device.  If you repeater is not in motion, then we have found that there is little to no consideration to the type of device used (data service).  We also have learned that the c-Bridge is now handling the changing IP's of a peer repeater in motion better now, as quickly as 15 seconds seconds most of the time.

Antennas, Duplexer and Frequency separation:  Consider your use of zero, one or two antennas.  If you plan to use your repeater only while driving, no duplexer or antennas are needed and you can use your mobile radio or HT.  If you want better coverage while outside of your car, put a spike on the receiver.  If you want fair coverage but no duplexer, use a mag mount spike on the TX and stick it to the repeater chassis and put the receiver antenna on the roof mount.  If you are not using a duplexer at all, consider using a 15 meg split for better coverage as well as the lowest TX power setting possible.  We have used 1 watt out into the spike and a rooftop gainer on the receiver and with a 2 watt HT, have better than .5 mile coverage through a thick pine forest with -95 dBm RSSI on the HT and -59 dBm RSSI on the repeater when deployed on a 15 meg split.  If you need higher power and/or wider area of coverage, then you should use a duplexer and the 6 cavity flat packs are perfect for this purpose.

LTE, 3G, 2G, Antennas: Which is best to use and why?  This is a bit sketchy at this point and input would be appreciated.  When we used a Cradlepoint with a Verizon USB dongle for 5000 miles to Hamvention 2012 and back, we found that we had fewer issues with tower hand-offs if we ran at 2G connections.  Our recent experiences with MiFi tend to tell us LTE is OK to use.  At this point, if you are not needing LTE speeds for a laptop or tablet, it may be best if you lock down to EVDO or CDMA or 3G only.  If you are transmitting while your connection shifts between 3G/4G, then it creates typically a harsh burst of noice.  And this can happen fairly frequently, so stick with 3G if possible.  Tower hand-offs generally don't cause an IP change but it is a set of towers in a larger group or area that do, so you do not need to watch for towers on the freeway.

We are using external antennas (diversity) and suggest that they be considered for the very best, lowest frustration deployment.  If you deploy roof-top diversity antennas, then place them at least 20 inches apart for best results at 700 Mhz LTE.  Remember you do not need maximum data connection but the most robust connections.  Even in strong signal areas, multipath and other interference can cause issues that a diversity antenna system will minimize.

Power up with 12VDC:  Both the XPR-8300 low-power repeater and the Cradlepoint MBR95 router work fine on vehicular 12 volts (your mileage may vary if you are a DC purist).  Current draw (engine off) is 1.1 amps for the router, USB modem and the repeater, connected and idling.  TX'ing at 1 watt adds another 1.3 amps for a total of 2.4 amps.  Battery backup is worth considering if you have any plans to let the the repeater run for long periods of activity or overnight and wish to insure that your start battery will not leave you stranded.  Purists again may wish to keep all the transients out of the repeater and router as well, so some isolation from the starter motor (during start conditions) is of certain value.

All power can be tied to one point for ignition on operation or use an always on point.  The better approach is to run on back-up battery (ASM's, gell cells or possibly SLA's) and add in re-charge when engine is running (simple relay energized by "ignition on" to bridge battery to vehicle 12V system after the motor start cycle as has ended) and a few handy switches to control auto-manual charging and power to the repeater).

Another simple method is to use a solar power controller to isolateyour run battery from the start battery and protect from over-charge as well as deep discharges.  A super inexpensive 20 amp controller is on Amazon for about $11 delivered and there are many similar clones to this particular controller.  My 22AH SLA runs for 12-14 hours typically depending on the transmit time.  I just parallel up another for double the capacity.  No switches needed and use of Anderson Power Poles throughout make changing the lash-up very simple and that is handy for vehicle changes.

Secondary 110VAC:  Longer stationary times may be enabled by way of a handy 110VAC source.  Adding in a small switcher power supply to rapidly recharge your run battery as well as power to your repeater, is worth considering.  The combo power/battery revert jack on the repeater will only re-charge batteries at 500-600 mA which may be to slow to adequately recharge your dedicated run battery, so do not rely on that feature.  The 10 amp switcher I use presents a high impedance when not powered up, so it sits on the battery 7/24.  A motor home would be very simple for an installation as both 110 VAC and 12 VDC run battery connections are handy throughout most rigs.  I'd suggest having both sources if convienent.

HT or Mobile Radio Use:  An HT should be available even if you have a mobile radio in your vehicle.  You likely will want to be able to use the repeater while outside the vehicle.  A mobile radio is handier to use while driving but it is also more problematic with repeater riding along.  Mobiles are typically it is set up for high power and you don't want 40 watts just a few feet from your repeater antenna.  Consider a dummy load and or reducing your RF output, both a pain if that same mobile radio is to be used with stationary repeaters or other standard uses; analog, simplex, scan LE, etc.

HT's work fine with a repeater on zero, one or two antennas and for a temporary install in the YL car's trunk, no antennas or duplexer, are very simple.  Adding in the antenna, duplexer makes for a more complications and time but provides more and/or better coverage away from the vehicle.  So consider the trade-off's vs. benefits when making your overall deployment decisions.

Determining if you are on or off the IPSC network:  Unless you hear networked activity from your repeater in motion, you will not know with any certainty, that you are actually, connected to the IPSC network.  Use the Parrot talkgroup to quickly and simply determine if your repeater is working on your IPSC network.  The c-Bridge Net watch easily provides you that clue.  Many c-Bridge owners have graciously enabled guest accounts for use by the TRBO community.  Other possible solutions may be EchoLink or TRBOVUi, though not likely nor simple for a driver in motion to manager.

Typical data use:  It may surprise you how little data is needed for TRBO communications.  We have found that with a 5 repeater IPSC network connected into both DCI and DMR-MARC uses about 18 MB a day with typical activity day in and day out.  If you must keep to a minimum amount of daily data consumption you can either limit your TX time into your mobile repeater or have fewer peers on the IPSC network you are using.  The more peers and active timeslots on the network (only while you are transmitting into your mobile repeater) the more data is consumed.  Even on the stingy 250 MB Verizon pre-paid plan, this should never be an issue. 

Repeater in a box:  This is NO7RF's version of a permanently deployed (if not mounted) repeater.  The design was to enable reasonably easy moves between 2 primary vehicles as well as use in most any vehicle if needed.  The UHF duplexer/antenna is optional as I typically use a "leaky" resistor dummyload on the transmitter connector and spike on the receiver connector, good for about 1/4 mile through heavy trees and not line of site.  See the "repeater on a box" page for more details and pictures.

Other odds and ends, tips or hints...tis the catch-all bin

  • Use the handy Parrot talkgroup to confirm IPSC connectivity; great to have while driving

  • Place your MiFi/USB Modem/Router so you can watch it's connection status; know that you have service, it's strength and  have a better idea of your IPSC status while in motion.  This can help reduce frustrations when you can't take the time to look at netwatch.

  • Buffering delays; if you can hear audio from land based TRBO network, the delay experienced through Verizon is a function of signal strength; 2 seconds is good, 5-20 seconds is very poor.

  • Signal Strength; RSSI's less than about -95 dBm are subject to delays, audio drop-outs, poor comm quality.

  • EVDO or CDMA suggested; 1x is not useable, LTE is gaining in availability, locking to "EVDO or CDMA or 3G only" is likely to be the best overall setting to limit the number of service changes as you move between 3G, 4G and LTE areas.  If you are in a major urban area, use the automatic setting, especially if you are sharing your connection with laptops, tablet, smart phones, etc.

  • Signal changes/drops and tower region hand-offs; typically 15-20 seconds is needed before your repeater comes back on the IPSC network if Verizon service is dropped or has a poor tower or region hand-off.  Physical Master repeater networks are generally faster and more robust for automatic IPSC re-connections than a c-Bridge acting as the master repeater but the c-Bridge as mater is much more robust with the release of RVN8200.

  • Temporary WiFi Hotspots:  While smartphones, MiFi, FreedomPop and others do work, they are a poor choice for other than occasional use.  The soft switches, internal batteries or tethering of phones is far more problematic.  You would also need a client bridge to get that WiFi into an Ethernet cable for the repeater.

  • Permanent vehicular WiFi; The Cradlepoint MBR95 does not have external antenna jacks so it is not entirely appropriate for distance away from the vehicle (hotel, shopping, etc).  Consider a router that supports external antennas if you want longer hotspot range.

  • Repeater Fan Control; Mount a DPDT center off mini-toggle on the chassis above the PS fan; down is PS fan only, up is PS and TX fans enabled for normal operation.  The PS fan runs when powered by 12VDC and is noisy inside the vehicle as well as when the ambient air temp is high, the TX fan ramps up like a jet even though the TX is ambient cool.  Now, while running 1-5 watts on 12VDC, there is now a choice between no fan noise and save up to 1.5 amp/hours as well.  The repeater can still operate normal duty when returned to a stationary use.


Revised: 09/22/2014 15:58

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