Saw this at survival blog...

Discussion in 'Survival Communications' started by Gunny Highway, Apr 11, 2013.


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  1. Gunny Highway

    Gunny Highway Hard Work and Sacrifice blessed by God's Grace Site Supporter

    Letter Re: Ham Radio Standardization for Survivalbloggers?

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    Dear JWR,
    I read the Ham Radio Standardization Article with great interest. Most preppers are integrating some type of VHF/UHF communications into their plans. These communications could be MURS, FRS, GMRS, or Amateur (Ham) radio. In a March 2, 2013 CNET article by Declan McCullagh, I read some rather unsettling information. In detailing some of DHS's specifications for their version of the Predator Drone, the author states:
    "CBP's specifications say that signals interception and direction-finding technology must work from 30MHz to 3GHz in the radio spectrum. That sweeps in the GSM and CDMA frequencies used by mobile phones, which are in the 300MHz to 2.7GHz range, as well as many two-way radios."
    The specifications say: "The system shall provide automatic and manual DF of multiple signals simultaneously. Automatic DF should be able to separate out individual communication links." Automated direction-finding for cell phones has become an off-the-shelf technology: one company sells a unit that its literature says is "capable of taking the bearing of every mobile phone active in a channel."​
    The 30 mHz through 3 GHz range covers ALL VHF and UHF frequencies for ham, FRS, GMRS, MURS, Business, Public Safety, Military, and Marine. Technician Class ham radio operators only have one phone (voice) band below 30 mHz and that is the 28 MHz 10 Meter band. The 10 Meter band is not well suited for close-in communications and while it certainly is capable of providing long distance communications, the propagation is highly unreliable and depends on a pretty high sunspot number to raise the MUF (maximum usable frequency) high enough to enable those communications.

    I would recommend that preppers consider obtaining the FCC's General Class license. With the General Class license, the prepper will have access to ALL ham bands below 30 MHz. Many of these are well suited to close-in communications as well as long distance communications, day or night.

    One disadvantage to these HF communications is the size of the antenna. A simple [half-wave] wire dipole antenna on the 10m band (28 MHz) is around 16.5 feet long. At the bottom of the HF (below 30 mHz) spectrum, the 160m wire dipole would be 246 feet long. Portability would be an issue, however the antennas are simple, light weight, cheap and easy to make yourself. There are many battery powered HF radios. The Yaesu FT-817, Yaesu FT-897, and the MFJ 9410, 9417, 9420, 9475 series are just a few examples of voice-capable portable HF radios. If you get into Morse code, there are more options for portable HF radios as there are countless kits available that allow you to build a working radio for as little as $40 up to $1,400.

    In conclusion I would like to say that I have heard many preppers say they don't need to obtain an amateur (ham) license that when TSHTF, they will just use whatever communication gear they need to. I say to this, you will need to know how to build an antenna, need to know what frequencies are suitable for certain distances and certain times of day, and operating procedures. The amateur radio license is a license to learn and I highly recommend that you start learning now, before disaster strikes. - K. in OK


    so BT doesn't this bugger up the Motorola phone communications ?
     
  2. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Nope, as with ALL Spread Spectrum type Radio's the RF Emmissions from them, jump around in the 902-928 MHz ISM Band, never staying on ANY one Frequency for more that 10 Miliseconds. This precludes many of the typical DF (Direction Findings) Techneques, that could be used from a Remote Platform. The sudo-random nature of said jumping, makes Doppler DFing not practicle, and the Multiple Bearing Line Techneque requires a Stable Carrier, for considerably longer than 10 Ms, as well.... To get a reasonable DF Fix, on a Spread Spectrum Emmission, one would need to be able to lock in on the Spreading, and follow it Exactly, for multiple Seconds and one could then derive a Bearing Line, but this would REQUIRE much more sophisticated Receivers and Computational Power than could be Flown in a Drone. Something that only a MILSTAR Plane might Possibly be able to do. .....
     
    franks71vw and kellory like this.
  3. KAS

    KAS Monkey++

    u never let me down BT
     
  4. Gunny Highway

    Gunny Highway Hard Work and Sacrifice blessed by God's Grace Site Supporter

    NICE ! MY Big Shitty Grin - You are the bomb BT
     
  5. BigZ

    BigZ Monkey+

    An automated system would definitely have a struggle with DFing a spreads spectrum signal however with a simple analog receiver its not so difficult.
     
  6. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Explain your theory, Please.....
     
    franks71vw likes this.
  7. BigZ

    BigZ Monkey+

    an analog receiver tuned to the center freq of the transmisions say 915 MHZ using a swept frequency IF with a 20 meg spread would intercept all said signals and generate a bearing line to all transmitters within range. Been there done that many times.
     
  8. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Were you using Phased Antennas? How are you distinguishing between multiple Emitters, using the different Spreading Codes, all emitting simultaneously. What type of Display gives you the Bearing Line, to each emitter? How do you account for MultiPath Reflections, which are very prevalent at these Frequencies in Urban Areas?
     
  9. BigZ

    BigZ Monkey+

    250 rpm dipole array feeding. Recvr with > 100db sensitivity a polar df display And a swept trace of the IF strip
     
  10. BigZ

    BigZ Monkey+

    Bearing lines on polar display length of line was proportional to signal strength.
    May not be too effective in an urban area however in a SHTF scenario I wouldn't be in one the good news this kind of equip was replaced by ones that don't cover this range
     
  11. BTPost

    BTPost Old Fart Snow Monkey Moderator

    Ok, I can see that application, but it doesn't deal, with MultiPath Reflections, at all, or Multiple Emitters in the same Bandwidth. Just gives multiple false Bearing Lines, considering, that on each Exchange between any Units, using Squad Comms Mode, each Receiving Unit responds with a LockUp Emission back to the originating Unit. All these would show up, along with any Reflections, due to MutliPath, all showing up as Vector Lines on the Display, with no differentiation's, for Delays in Emission arrivals, at the DF Antenna Array. Would take a very savvy Operator will a lot of experience, to pick out the REAL Bearing Lines, from all the Possible False Lines, where an unknown number of Units, were operating, in a local AoO, in an Urban Area. . I have considerable experience with such AutoDF Receivers in High Density Comms. Up in Bristol Bay, Alaska, back in the day. We used this type of device, to get Bearings on Marine Vhf Units, broadcasting on non-Marine Frequencies, for Private Comms, during the Togiak Herring Fishery,that takes place each spring. The country is very flat, and mostly over water, for 180 Degrees, with mountains 15 miles or more, inland off the beaches. Not a lot of MultiPath, to deal with. Still during the hight of the Fishery the Bearing Display was just about useless, due to Multiple Emissions being received, along 40+ degree sectors, simultaneously, and displayed without regard to the Specific Frequency of the Emission. We used a Spectrum Analyzer in conjunction with the Vector Display, but found we had much better luck, listening to, and Identifying, specific Voices, and then doing Digital Matches, to Identified Voices on the Regular MARINE Channels. This was accomplished with VAN FULL of RACKED GEAR, specifically setup for that project. Mostly it turned out to be a frustrating experience. As I recall only three Violation Notices were issued, and two of those were to Fixed Locations, for UnLicensed Operations, after a Local Inspection of the Stations. Not real productive....
     
  12. BigZ

    BigZ Monkey+

    I agree that takes a very good operator however stopping the antenna at a specific bearing line helped differentiate whether it was a source or reflection granted I was doing this looking primarily at radars but with maintaining good radio discipline and keeping transmissions short and necessary would make DFing of comm's very difficult but not impossible and yes this to required multiple racks. Of equipment
     
  13. franks71vw

    franks71vw Monkey+++

    great convo...
     
    KAS likes this.
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