Article on frequency hopping nets.

Discussion in 'Survival Communications' started by Ken_C, Feb 12, 2015.


  1. Ken_C

    Ken_C Monkey

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  2. kellory

    kellory An unemployed Jester, is nobody's fool. Banned

    Alright, question. If the hopping net needs one master (a base) and any number of slaves, and if the master broadcasts the hopping code, then what is to prevent a hopping slave unit from being used as a jammer? It is unclear when or how that cods is transmitted.
     
  3. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    It does not work like that..... I could tell you exactly how it does work.... but then....you know.... I would have to kill you ;)
    I was a master trainer for our base when we first fielded the Army's portable radio with Freq. Hoping technology.
    FM 6-02.53
    TACTICAL RADIO OPERATIONS
     
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  4. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Is this hopping similar to or the same as spread spectrum?
     
  5. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    It basically is all radios within + or - 7 seconds moving across the entire spectrum with a base hopset..... which tells it in what manner to move within the freq's. Your net will not be able to be jammed unless the entire spectrum is jammed.... which is not beneficial for the opfor's own comm's.
    There are means to get back in if you lose the timing or if you have blasted your devices 'sets" due to potential capture.... but you have to know the procedure and you also fall back to the code book for authentication..... prior to getting sucked back into the fold ;)
     
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  6. BTPost

    BTPost Old Fart Snow Monkey Moderator

    The REAL issue with such Modes, is if the Frequency hops are to far apart in Frequency, you tend to lose Propagation between the two stations.... If you are just Hopping around a single Band, it works Fair, but if you are hopping around on several HF Bands, and one of your Hops hits a Frequency where there is no propagation between the two stations, that Hops data is lost and must be repeated, on a subsequent Hop, where the Band is Open. This slows down the Comms and Bandwidth available considerably.... What most HF Hoppers do is use ALE to find what bands are OPEN between the two stations and the use that criteria, to determine what Frequencies to use, and how long each Hop needs to stay active, for best ThruPut.
     
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  7. ghrit

    ghrit Ambulatory anachronism Administrator Founding Member

    Works best with NVIS?
     
  8. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    On the military FM digital sets using frequency hopping technology, they are moving through the prescribed freq. sets, around a 100 frequencies per second, as I noted above. The lost data for that one freq that may be incurred due to whatever reason, is so minimal that it would not be noticed whatsoever. Same principle of data packets on a PC. I do not know how this tech is being used with the civilian radio's, but with the military sets, they work great and provide secure & basically jam proof communications. Once you load in your unit Key set which is the security codes, you load in your Hopset's with a separate device. These codes are universal for all unit radio's within that prescribed net.... assigned at a much higher level than unit level, within Corp comm group dictates. Any frequency issues that are known, will be addressed and deleted from the hopset's master key.
     
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  9. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    For the FM sets we used an OE-254 antenna for base camp operations. You can throw one of these up in 15 minutes or so with one or two guys.

    The NVIS we used was only with our AM man-pack radios. We were skipping all around the Hawaiian Islands no problem with a basic di-pole.
     
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  10. BTPost

    BTPost Old Fart Snow Monkey Moderator

    .MIL FM ManPak Radios are NOT HF Radios, but VHF Radio, that use the .MIL Frequencies between 55Mhz and 88Mhz... Frequency Hopping Radios that operate in this Band usually are NOT depending on E2 or F3 Layers in the Atmosphere, for Propagation, so Propagation Dropouts are not an issue for them, and these radios are designed for Comms in Units smaller that Battalion Size, usually, depending on terrain.
     
  11. Yard Dart

    Yard Dart Vigilant Monkey..... Moderator Site Supporter++

    As a former 31KP2 and 31UP3R... I know exactly what you are saying BT. I am a tactical communications specialist by training and experience. Yes, I may fall off at this time, when it comes to civi Ham operations....for now. But that is not what I was trained for at the time I served, nor specifically what is being discussed in this thread. My job was to provide command capability to bounce a signal to our troops in theater & worldwide... with the tools I was provided.... so I am just talking from that aspect, and that alone. I was a master trainer with the SINCGARS fielding to the 25th Infantry and could operate the unit blind if needed.... and pick up stragglers all day long.... that lost their "way".... it is what we did... not just a "job" it was an adventure ;)

    I was focusing more on the FM side/VHF when it comes to freq. hopping in relation to the article & the title of this thread.
    FM SINCGARS radios are used theater-wide in all levels of organizations....well beyond Battalion size. Think layered communications....
    In an infantry company we had short range FM squad radios, platoon/company level SINCGARS FM, as well as a man-portable AM and tac-sat's... at company level. At battalion level, take that times 3, plus the re-trans squad (which I ran for 6 months till promoted out of the coded position).

    In an infantry battalion you will have one re-trans unit that sits high up.... and re-trans the uplink from battalion down to each company.... depending on your site... you can cover a great tactical area. As you climb the tree to brigade, division and corps you have the same ladder... when it comes to FM. AM was always utilized as a back door link, unless you were beyond normal FM range. But when you needed to hit range... we always went tac sat for its stability and signal security.

    Not trying to debate anything here... just sharing.
    :)
    YD
     
  12. The way it was explained to me was that HF Spread-Spectrum is hard to do because the transmitter has to be able to use pretty much any antenna, be it a man-pack whip or a doublet or a vertical tape that's designed to survive breakaway shocks.

    That all means that the transmitter has to be able to retune itself for every channel in the spectrum set, quickly enough for receivers to keep synchronization, and that means that the bandwidth that can be allocated to any given set must be fairly small. Opponents can jam a small slice of spectrum fairly easily, so the "switch rate" has to be high enough to avoid "hearing" the jamming on any given channel, but not so high as to slow down the receiver's computer chips to the point where a voice signal would be delayed too much to be useful in combat. (I hope I wrote that clearly: it's second-hand info).

    I got this explanation from a guy who I know, and I also know that he was doing work on this subject for DOD. The point is, his explanation, as far as he was willing to go with it, makes sense.

    William Warren
     
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