Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Talked to my local cop about his sat phone comms

  1. Mar 25, 2016 #1
    Have always drooled over these awesome and mega priced babies until they started dissspearing. Cop says they are being replaced by sat phones which I thought were a nightmare to get a connection and crazy expensive. He would not discuss the performance.

    So awesome HF antenna versus sat phone, can someone explain the pros and cons excluding digital encryption.

    What they had that was pure awesome;

    http://www.codanradio.com/product/9350-vehicle-whip/
     
  2. jcsd
  3. Mar 25, 2016 #2

    davenn

    User Avatar
    Science Advisor
    Gold Member

    HF -- limited range, totally reliant on ionospheric propagation conditions
    bulky - both the transceiver and antenna
    power hungry
    limited bandwidth
    very prone to interference from other spectrum users
    to name a few things

    Sat phones -- none of the above


    Dave
     
  4. Mar 25, 2016 #3
    K, makes sense. I think one positive tho is the lack of dependence on complex external infrastructure.

    in a HF station you totally own it, that has to be an advantage for a rural cop.

    What you think of the whip in the link, hopefully if they are obsolete I can get one cheap. Look good on the front of my truck.

    a well engineered product IMO.
     
  5. Mar 25, 2016 #4

    davenn

    User Avatar
    Science Advisor
    Gold Member

    But its useless if it cant reach the base station, aye


    and you intend to make actual use of it ?
    Are you licenced for HF operations ?
     
  6. Mar 25, 2016 #5
    I would think it was cheaper for a city cop. A rural cop needs good coverage which sat phone provides. In a city the sat phone coverage might not be as good (inside buildings, whatever). A city can afford a good HF system with multiple transceivers. This would be cheaper than an army of sat phones. (Of course an army of cell phones might be cheaper still.)

    There are a limited number of sat phones available in the world due to bandwidth and coverage issues. Handing one to each of the 50,000 NYPD employees might not be the best use of resources. But giving one to each of the six officers in Podunk Montana is likely cheaper than a custom designed HF setup which would rival the New York setup in base station complexity due to terrain considerations.

    In addition the NYPD needs to be able to keep working in disasters in a way rural PDs might not. An orbital event (Solar Flare, etc. or something more sinister) might wipe out the sat phone connection. It would be hard to wipe out redundant, hardened HF base stations.

    Were I in charge of a large PD's communications system, I would try for an HF system backed by regular cell service with a contract specifying emergency priority over regular clients.

    Were I in charge of a small PD's communications system I would look at sat phones (or cell phones if the region had great coverage) with a base station kept in storage just in case.

    In between the two is where the creativity lies. If the department is too big for everyone to know each other, protocols might start arguing for more complexity than simple cell phones.
     
  7. Mar 25, 2016 #6
    Civilian sat phones is like $5 to connect, which is not fast, then a conversation like , " hi honey can you pi k up some milk and breed on your way home from work" is about $20.
     
  8. Mar 25, 2016 #7

    davenn

    User Avatar
    Science Advisor
    Gold Member

    VHF and UHF and the main freq's used by cops and other emergency services
    the cops here and in NZ used to mainly use VHF but that has largely been dropped in favour of UHF ( 400 MHz band)
     
  9. Mar 25, 2016 #8
    UHF would lack range in rural??

    HF users have had to step in for police and emergency services in natural disasters. In July my club gets a $500 donation for doing comms at a big motor bike race, the emergency services completely failed. The club was given a trial last year and it was perfect hence the financial gift and ask/beg for us to come back.
     
  10. Mar 26, 2016 #9

    davenn

    User Avatar
    Science Advisor
    Gold Member

    in extreme rural, eg outback Australia, yes.
    general rural, no.... you seem to have forgotten that there is a huge repeater network in most countries ( well western ones at least)
    that will pick up the signal from the vehicle up to at least 100 km. And with lots of repeaters in the network, it fills in the dead spots
    in system coverage



    Dave
     
  11. Mar 26, 2016 #10
    Good point re repeaters.



    My personal interest in radio is minimal infrastructure ie if everything went to crap what's left that will work.
     
  12. Mar 27, 2016 #11

    sophiecentaur

    User Avatar
    Science Advisor
    Gold Member

    The comparison is only worth making when you have defined the actual requirement. VHF is cheap and will work over a range of 20 miles easily, if your base station is well elevated and there's nothing much in the way. A sat phone will work all over the world. Which do you need and how much money do you have?
    I wouldn't have thought that HF would be very useful because, firstly, it isn't designated for mobile comms (afaiaa) and the possibility of frequent interference from distant stations is always there. VHF propagation is more 'line of sight' (well defined service area), most of the time and it's also legal if you use the appropriate channels.
    I do sympathise, if you are really lusting after a sat phone, though. :smile: Go into the shop, open your wallet and say "help yourself".
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Talked to my local cop about his sat phone comms
Loading...