An Interesting, SECURE, Comm's Device, for your CN-AoO

70 cm is allowed for technician class licenses. It is pretty easy to get, even old dogs can learn enough and fast enough to git er dun. (After all, I did it.) If you form up a study group and go to work on it, you can take the test and all be in business. 70 cm is essentially line of sight, but will bounce around; you'll need to experiment some to see where it'll work for your group.

900mHz is in the 33 cm band, also line of sight, also tech ticket material. Again, you might get lucky on reflections.

Rather than depending on bounce among hills and rocks, using NVIS (Near vertical incidence) antennas might work a lot better and won't tie you to sitting on a particular log when you want to bounce a signal to your buddy who has to be standing on his head under a pine tree to receive. Secure, it ain't unless you get into the one pad messaging system that the monkeynet will use when things go all out of round.

There are some really inexpensive dual and tri band handhelds on the market these days. Just don't forget that to be legal to transmit before out of roundness strikes (as well as theoretically afterwards) you will need to get your tickets.

 

Correct, code is no longer required. NVIS will work portable, the antenna size is (of course) frequency dependent. No ground plane required, IIRC (and well I may not) and I believe mounting height is not too critical. I have some more research to do before I get serious about a rig for HF.

 

@ghrit, @Altoidfishfins, Ok, I have been considering this ISSUE (Range extension, and or Terrain, or Path Issues) for a while, and I think I have an answer for some of these, that would be SECURE and still get the Job done.... Build a Repeater out of two Motorola i355s.... They ALL have a Remote Audio Jack, for access to Rx audio, Tx Audio, and PTT... They are Spread Spectrum, so if one were to set them up with Vertical Separation of say 15 Ft, on a 30 Ft Pole, and programmed them on Different ChannelSetUps, Say Ch1/Code5 on one and Ch10/Code 5 on the other, and placed the Pole, a Solar Panel, Charge Controller, and a Battery, on the Hilltop between your two places. You would use the first Setup to TX, which would trigger the Second Unit to Tx on the Second Setup, which would be RX'ed by your Friend. Then he would replay on the second Setup and the second Unit would trigger the first Unit to Tx on the first Setup back to you on your Unit which is still on the First Setup.... I haven't tried this, but the theory is SOUND, and should work. The only thing that you would need to do, was to WAIT for the other Pole Unit to Lockup with your Friends Unit, before any audio could pass on the Link. This would be a couple of Seconds, I think... Double what it takes for a single Link, the way we use them NOW.... also NOTE, that these Units can be operated with Power Amps, to Ten Watts, and ANY Antennas one would like to use, under Part 97 (Ham License) as they use the 902-928 Mhz Ham Band which is a SHARED Band with ISM, and the Ham USE is a Secondary Use, where the ISM is an Unlicensed, and must accept interference from and can NOT interfere with a Primary or Secondary Use. I guess I will have to get a couple of more i355s, and try this out, this spring....

 

NVIS is for HF ONLY and doesn't really work for VHF or UHF... If it did, no Sat Based Comms would ever work, as the RF would be reflected off the F1 AND F2 LAYERS like HF signals do..... Passive Repeaters DO Work for VHF and UHF very well, IF they are constructed and installed properly....

 

@ghrit, @Altoidfishfins, Just thinking out loud here, But one "could" build a HUB Repeater on a Tall Pole, that had multiple (not just two) Units, all cross-connected, so that a RX on any One Unit would cause a Tx on ALL the other Units, and then each Camp, or Group, could just TX up on their Setup, and be received by ALL on their individual Setups. Another thought just came to mind, Why not just put a High Powdered WiFi Router up on the Pole as well, and do ALL the interGroup Comms via Digital Voice, (like Skype or Equivalent) You could use High Gain Panel Antennas, on each end, at the Camps, and a reasonable High Gain Omni Directional Antenna on the Pole, in the middle. Leave the Encryption to the computers, and send Encrypted GPG files, back and forth, across a completely closed Network. Costs would be cheap, and as SECURE of Comms, as the Encryption Scheme. GPG for normal Comms, and OnePad for REALLY SECURE Comms.....

 

But Security of Comms is ALWAYS an issue, especially when Comms can be DF'd and Scanned... That is why the DirecTalk Units are so valuable.... Not Scannable or DF-able...even WiFi would only be DF'able to the Mnt Top Node, as the others would be on very tight RF Paths to the Central Router on the Pole. And if the SSID was NOT Being broadcast, Scanning wouldn't get you much, and especially if encryption was used on the links, via VPN, or Secured Tunneling...

 

@Bear, Do you have a Pair of these? If not would you like a Pair to test out?

 

Radio Direction Finding depends on a Carrier Wave being stable on a Single Frequency, for long enough for the DF Receiver to determine a Bearing Line. Since these Units are Spread Spectrum, Frequency Hopping, they spend only Milliseconds on any ONE Frequency, before moving on to the next Frequency Hop, in a Calculated System that is Transmitted to the Receiving Unit, at the beginning of the Transmission, so the Receiving Unit is in Sync with the Transmitting Unit, and both Units Hop in Sync. Unless the DF Receiver is able to decode, the Sync, and Hop along with the Units in question, No Bearing Line is possible to glean from the Transmission. You are either LOCKED up with the Transmitter or you get NOTHING, and it takes a whole Truck Load of very specialized Equipment, to even get close to dealing with Spread Spectrum Comms. ..... YMMV....

 

True, However, at less than 10 Milliseconds per Hop, how long does it take to get a direction, and Strength, on a signal, that also has Mutlipath Fading, as well as other Emitters, transmitting in the same bandwidth? Like I stated, It CAN be done, but it takes a Truck Load of Equipment to actually derive a Bearing Line, from such an Emission, and a very experienced Operator, of said Equipment, to interpret the results, for a Tracking Group.

 

Yep, I have a pair sent gratis from BT as well and have tested them locally as well as when BT drove through my area.
Tested them with @VisuTrac at the Knob Creek shoot without any issues.