rvmills
Well Known Member
Pete, Sam, Allen and the VAF APRS Brain Trust:
Christmas letter to Santa has APRS gear on top (well, right behind a healthy family and the safety of our troops), and Tech License Exam Q&As are printed for study. Took 2 cold (pre-study) exams and scored 77 and 80 (like the site said, "Good, but not Great, you need to study more"). Some study planned, then off to take the exam. So I'm contemplating the install options, which have morphed slightly after doing some SARL racing, and I hoped to bounce a few questions off the gang. Apologies in advance for the length.
One racing mod I'm going to work on this winter is to make flat wingtips to play with during the races. The flat wingtip will not accomodate the APRS gear (and I want to track while racing), and if I need to disable smart beaconing for the races, accesibility is now a bigger issue than I origianlly thought. So rather than copy Pete's original wingtip install, I'm going to move the unit into the cockpit. This opens up some alternative GPS and antenna options, which generates some of my planning Q's.
My plan has been to go with the Byonics MT8000FA and a Byonics GPS2. First couple questions relate to that set up:
1. Does the MT8000FA now come with a case, or will I need to fab that (as Pete did in his original post)?
2. Does the MT8000FA have a DB-9 receptacle for the GPS2 cable (can't tell from the web pic). If not, does it come with instructions on how to install one?
3. Is that DB-9 connector also where I will connect the computer for configuration?
4. Do you think the same USB to Serial cable that I use to update my Dynons will work to connect my computer to the MT8000FA?
5. Do I need the MV-12 regulator to attach the MT8000FA to ship's power?
6. Is the 5V GPS2 plug and play with the MT8000FA on ship's 12V power (saw the warning about not plugging it directly into the Tiny Track3, and just want to make sure its OK with the MT8000FA).
On GPS selection...the GPS2 is inexpensive and easy to connect, but I want to make sure I'm not overcrowding my dash and might cause GPS interference. I have a 396 with antenna on the dash, along with the XM hockey puck and my SPOT (which after APRS will be for OK/Help/911 messages, and not tracking). Will adding the GPS2 to the dash cause interference?
I've considered just splitting the blue data out wire from the 396 to my Dynon to get the GPS feed, but the Byonics site description of the MT8000FA says "simple 2 wire GPS connection". What would that second wire be if I splice into the 396 data line...ground perhaps? To be honest, just using the GPS2 would be much simpler, as I wouldn't have to rummage around behind the panel to get to that data wire...so as long as the GPS2 won't interfere with the 396, that's the way I'll go...just wanted to ask just in case.
Lastly, a couple on the antenna. With the unit in the cockpit, I can now use the antenna that currently is connected to my COMM 2, which is a sheriff SAR radio (136-174 MHz). It is a Comant bent whip (CI-122) that has not been trimmed, but works as is with that radio. I'd prefer not to add a third antenna to the belly (racing and cable routing considerations), so I'm contemplating using a switch to switch that antenna between the SAR radio and the APRS (APRS on unless I'm on a SAR mission that requires that radio). I've seen some switch possibilities, and as I looked at it, I even thought that perhaps I could make it a three way switch, and add a short cable to plug a handheld VHF radio into, in the event that my SL-40 COMM 1 goes down.
Here's a 4 way switch from MFJ Enterprises I'm considering (can't find a 3 way, but this might work):
It has ISO-239 connectors, and I'd either have to build RG-400 cables that have ISO-239 on the switch end and BNC's on the radio/antenna end, or use ISO-239 to BNC adapters.
Questions that arise from this idea are:
7. Do you think the switch itself or the 239-BNC adapters would leak RF and impact other avionics? (MFJ says the switch's isolation is better than 50dB at 500 MHz and 60dB at 30 MHz).
8. Do you think the one antenna would work for the SAR radio at 136-174 MHz, the APRS at 144-148 MHz and the handheld at 118-135 MHz? It seems to work without trimming for the SAR radio, so I thought the same might be true for APRS? Whaddya think?
Might be trying to do too much with one antenna, and the handheld would be the first to drop from the list, expecially if I need to trim the antenna for the APRS. If that is the case, how much would I need to trim?
I know that's a lot of Q's, and thanks for your patience in reading through it all. Any thoughts or ideas are most welcome! Thanks again!
Cheers,
Bob
Christmas letter to Santa has APRS gear on top (well, right behind a healthy family and the safety of our troops), and Tech License Exam Q&As are printed for study. Took 2 cold (pre-study) exams and scored 77 and 80 (like the site said, "Good, but not Great, you need to study more"). Some study planned, then off to take the exam. So I'm contemplating the install options, which have morphed slightly after doing some SARL racing, and I hoped to bounce a few questions off the gang. Apologies in advance for the length.
One racing mod I'm going to work on this winter is to make flat wingtips to play with during the races. The flat wingtip will not accomodate the APRS gear (and I want to track while racing), and if I need to disable smart beaconing for the races, accesibility is now a bigger issue than I origianlly thought. So rather than copy Pete's original wingtip install, I'm going to move the unit into the cockpit. This opens up some alternative GPS and antenna options, which generates some of my planning Q's.
My plan has been to go with the Byonics MT8000FA and a Byonics GPS2. First couple questions relate to that set up:
1. Does the MT8000FA now come with a case, or will I need to fab that (as Pete did in his original post)?
2. Does the MT8000FA have a DB-9 receptacle for the GPS2 cable (can't tell from the web pic). If not, does it come with instructions on how to install one?
3. Is that DB-9 connector also where I will connect the computer for configuration?
4. Do you think the same USB to Serial cable that I use to update my Dynons will work to connect my computer to the MT8000FA?
5. Do I need the MV-12 regulator to attach the MT8000FA to ship's power?
6. Is the 5V GPS2 plug and play with the MT8000FA on ship's 12V power (saw the warning about not plugging it directly into the Tiny Track3, and just want to make sure its OK with the MT8000FA).
On GPS selection...the GPS2 is inexpensive and easy to connect, but I want to make sure I'm not overcrowding my dash and might cause GPS interference. I have a 396 with antenna on the dash, along with the XM hockey puck and my SPOT (which after APRS will be for OK/Help/911 messages, and not tracking). Will adding the GPS2 to the dash cause interference?
I've considered just splitting the blue data out wire from the 396 to my Dynon to get the GPS feed, but the Byonics site description of the MT8000FA says "simple 2 wire GPS connection". What would that second wire be if I splice into the 396 data line...ground perhaps? To be honest, just using the GPS2 would be much simpler, as I wouldn't have to rummage around behind the panel to get to that data wire...so as long as the GPS2 won't interfere with the 396, that's the way I'll go...just wanted to ask just in case.
Lastly, a couple on the antenna. With the unit in the cockpit, I can now use the antenna that currently is connected to my COMM 2, which is a sheriff SAR radio (136-174 MHz). It is a Comant bent whip (CI-122) that has not been trimmed, but works as is with that radio. I'd prefer not to add a third antenna to the belly (racing and cable routing considerations), so I'm contemplating using a switch to switch that antenna between the SAR radio and the APRS (APRS on unless I'm on a SAR mission that requires that radio). I've seen some switch possibilities, and as I looked at it, I even thought that perhaps I could make it a three way switch, and add a short cable to plug a handheld VHF radio into, in the event that my SL-40 COMM 1 goes down.
Here's a 4 way switch from MFJ Enterprises I'm considering (can't find a 3 way, but this might work):
It has ISO-239 connectors, and I'd either have to build RG-400 cables that have ISO-239 on the switch end and BNC's on the radio/antenna end, or use ISO-239 to BNC adapters.
Questions that arise from this idea are:
7. Do you think the switch itself or the 239-BNC adapters would leak RF and impact other avionics? (MFJ says the switch's isolation is better than 50dB at 500 MHz and 60dB at 30 MHz).
8. Do you think the one antenna would work for the SAR radio at 136-174 MHz, the APRS at 144-148 MHz and the handheld at 118-135 MHz? It seems to work without trimming for the SAR radio, so I thought the same might be true for APRS? Whaddya think?
Might be trying to do too much with one antenna, and the handheld would be the first to drop from the list, expecially if I need to trim the antenna for the APRS. If that is the case, how much would I need to trim?
I know that's a lot of Q's, and thanks for your patience in reading through it all. Any thoughts or ideas are most welcome! Thanks again!
Cheers,
Bob