I have had quite a number of people ask me about building versions of my APRS transmitters on the CAP Packet frequency. There are a few problems: One, I have to build 1000 at at time to have the RF parts built overseas, two: Not NTIA approved, Three, We will almost certainly lose the packet frequency when the new frequencies arrive, and four, We don't have a stinkin' packet network anymore to use it on.
The ham band APRS network ( automatic position reporting system) would be perfect for us! It covers just about the whole planet, works perfectly, is ported over to the internet ( Allowing you to see all the people, cars, airplanes, etc you are tracking superimposied on a map via the web) has low-cost, easily obtainable hardware, and there are no fees or costs of operation. Perfect in all respects but one: We can't use the ham band as the AF AUX.......Doooh!
We can use APRS over our VHF repeaters. This is done by marrying a TinyTrak (www.byonics.com) or similar inexpensive module to a GPS receiver, and plugging it into the microphone input of your handheld or mobile radio ( or base station for that matter) When you let go of your PTT button, a short burst of data ( about 1/3 of a second) sends your position, altitude, call sign, etc. I have done a little experimenting with the data on the Northern California Diablo Mountain repeater and it seems to have some real potential ( Important note to ground teams: You can unplug the GPS receiver and keep the IC from knowing where you really are....) With Diablo, it would be possible for an IC to monitor the position of every asset in near real time in a 200 mile circle around Mt. Diablo ( and even more for aircraft at altitude) Airborne didgipeaters ( digital repeaters) could make the system cover the whole country.
I am happy to make any CAP member a deal on my APRS transmitters, but they are only available on ham frequencies (144.390 Mhz) . It would be perfectly permissable to have one on a mission and activate it in an emergency, since you can transmit on anything and any frequency in an emergency (sort of a ham personal ELT)
If any one out there in the ES world has actually implemented an APRS system for CAP, I would love to hear about it.
Capt. Lord
How about using 900Mhz spread-spectrum radios?
900 Mhz radios are not cheap, and are effectively only line of sight. There are 1 watt license free radios that we could use, ground-to-air-to ground, with a highbird. Some Comm purists might argue that we can't use license free radios on AFAMS. ( This of course would rule out cellular phones and pagers if interpreted literally) The Garmin RHINO radios with GPS position exchange would be awesome for our purposes if someone built the functions into a commercial radio, but FRS is not kosher either. I would like to see how well APRS would work if we get to keep our "CB" Frequency (OPSEC keeps me from saying what that is-Hah! Haji will never monitor us!) I could do a very cheap 11 meter 300 baud APRS transmitter. (We would have to load up a cadet with a 102 inch whip.. not ideal for lightning storms...)
Capt. Lord
Hi Y'all,
Several Wings have deployed APRS systems, tho all will "go dark" whenever the transition occurs. AZ Wing, for example, has APRS in every Aircraft, and monitors at every Mission Base. using a statewide system of nodes/digipeaters that was installed in the early 90's to support Packet Radio. None of this system will survive the transition, tho the aircraft radios are compliant (T2020s) and may get used for other things.
AZ Wing never considered using APRS for GTs because the system was already overloaded when more than 5 or 6 aircraft were up (lots of digipeaters and fairly short intervals).
It does, however, constitute a significant OPSEC liability, and has also been an FAA problem at times, since the equipment is hardly TSO'd.
73 DE Hartley
Quote from: Hartley on April 12, 2007, 10:40:15 PM
Hi Y'all,
Several Wings have deployed APRS systems, tho all will "go dark" whenever the transition occurs. AZ Wing, for example, has APRS in every Aircraft, and monitors at every Mission Base. using a statewide system of nodes/digipeaters that was installed in the early 90's to support Packet Radio. None of this system will survive the transition, tho the aircraft radios are compliant (T2020s) and may get used for other things.
AZ Wing never considered using APRS for GTs because the system was already overloaded when more than 5 or 6 aircraft were up (lots of digipeaters and fairly short intervals).
It does, however, constitute a significant OPSEC liability, and has also been an FAA problem at times, since the equipment is hardly TSO'd.
73 DE Hartley
Hartley, Thanks for the good info! The OPSEC problem could be solved by either creating a proprietary coding, or using actual encryption of the data. No one seems to know if we will get a dedicated digital channel, which is why I would suggest we use our voice channels ( We don't know what it is, but we are pretty sure we will have one...) I don't think it would be wise to use the Aircraft AM radio though- the FCC might not want us peeing in that pool!
73
Capt. Lord
KG6HXO
Y222
Quote from: CaptLord on April 12, 2007, 05:50:34 PM
900 Mhz radios are not cheap, and are effectively only line of sight. There are 1 watt license free radios that we could use, ground-to-air-to ground, with a highbird. Some Comm purists might argue that we can't use license free radios on AFAMS. ( This of course would rule out cellular phones and pagers if interpreted literally) The Garmin RHINO radios with GPS position exchange would be awesome for our purposes if someone built the functions into a commercial radio, but FRS is not kosher either. I would like to see how well APRS would work if we get to keep our "CB" Frequency (OPSEC keeps me from saying what that is-Hah! Haji will never monitor us!) I could do a very cheap 11 meter 300 baud APRS transmitter. (We would have to load up a cadet with a 102 inch whip.. not ideal for lightning storms...)
Capt. Lord
That was just the suggestion from one of the National Comm gurus who spoke at last year's Wing Conference. I also wonder if digital would work over NBFM and if so, would we be allowed to use it?
Hi Gents,
The 900 mHz radios that you may have heard discussed were really intended to support large-volume data requirements -i.e., images/video in an air-to-ground scenario, though they could be used for APRS as well. There are a number of issues with airborne 900 mHz, multipath and interference being just two of them.
It is explicitly illegal for CAP, whether acting as the AF Auxiliary or as a civilian Corporation to use GMRS radios. In fact, GMRS radios require a license, so they are NOT "license free" as you describe (check the fine print on the package). The ONLY "license free" service CAP has access to outside of the Federal spectrum is FRS, and we are explicitly prohibited from using it for "mission comms".
In case you were referring to MURS, these radios are also prohibited to us as Federal users. (and no, we couldn't use our current radios for MURS anyway).
Yes, I am aware that these legal requirements are widely ignored - but NOT by nationwide corporate entities who have requested (and received!) funding from their Federal "parent" to support their comm program.
Cell phones, pagers and similar "common carrier" equipment ARE permitted to Federal spectrum users, with no special restrictions I know of (other than security issues and who is gonna pay for 'em.. :)). No, you still can't use your cellphone while airborne legally.
Hartley
Did I miss a post? I did not see anyone suggesting using MURS or GMRS for CAP.
Capt. Lord
Hi Capt Lord,
I was referring to your post of 4/12 at 12:50 in which you stated: "There are 1 watt license free radios that we could use,.." - if you weren't talking about GMRS or MURS, what were you talking about?
I confess to being a bit "twichy" on the subject, as we regularly get mail asking why units can't use those "handy, cheap blister-pack radios with 12-mile range" for CAP...we even had to make a formal response to the question once when an AF Officer made an official suggestion that CAP move off to GMRS so the AF wouldn't have to fund their comm system.. .. so if I made an improper assumption about your message, please forgive me!
73 DE Hartley
Ah, I see your line of thinking! No, the one watt license free radios I refer to are 900 Mhz spread-spectrum. Path losses and other problems are enormous at 900 MHZ, and I think that trying to use them except for possibly limited ground to air ops would be pointless. The other radio services are obviously out of bounds.
Capt. Lord
Example of license free 900 Mhz data radio: http://www.maxstream.net/products/xtend/rf-modem-rs232.php
Capt. Lord