Van's Air Force
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0.3 Watt or 8 watts?
- Thread starter Ron Lee
- Start date
rvator51
Well Known Member
Hi Ron,
I am in the same boat. I just ordered the microtrak 8000 8-watt transmitter but plan on adjusting the output initially down to around 1 to 2 watts and see how that works. I can always increase the output if needed.
Ron Lee
Well Known Member
Thanks Tom
I just read the manual on that unit and see that it can be adjusted. Do you know if the ~$20 antenna being sold by a kid works at higher RF power and did you get the power supply that seems to be suggested for this unit?
Despite the fact that I passed my first practice test, and am an all around awesome pilot, I am not well-versed in this stuff but do have enough smarts to ask questions.
I just read the manual on that unit and see that it can be adjusted. Do you know if the ~$20 antenna being sold by a kid works at higher RF power and did you get the power supply that seems to be suggested for this unit?
Despite the fact that I passed my first practice test, and am an all around awesome pilot, I am not well-versed in this stuff but do have enough smarts to ask questions.
Noah
Well Known Member
Tragedy of the Commons
Anybody interested in a serious discussion about this needs to read APRS designer Bob Bruninga's site about the "Tragedy of the Commons" http://www.ew.usna.edu/~bruninga/aprs/fix14439.html
<snip>Tragedy of the Commons: APRS suffers the classic fate of all limited resources (as well documented since the 1830's See Tragedy). Whenever there is a balance between individual interests and the common good, human nature guarantees the overloading and ultimate demise of the common resource. In this case, APRS throughput. This is easy to understand since the benefit of adding one more packet to the network always immediately benefits the SENDER, but the negative "cost" is spread over everyone else, and NOT the sender. There is no natural solution, other than the establishment of "Golden Rules" to live by for all concerned. <end snip>
Since the explosion in popularity of APRS several years ago, there has been a move afoot to reduce power transmission, number of packets sent, and to reduce the number of bounces allowed from one digipeater to another, as well as to increase the number of digipeaters available (similar to what has happened to cellular telephone networks 10 yrs ago to increase bandwidth). We need to be very careful, since as APRS users in aircraft we hit digipeaters and Igates for hundreds of miles, and have a much greater impact on the APRS system than ground-bound users.
Ron, could you design for the power supply but not install it? That way, you could try the low power installation in the area you fly and see whether coverage is sufficient. Although these are low power transmitters, they are very well tuned to the frequency (with a crystal IIRC) so ALL of the power gets tramsitted on exactly the frequency you want it on, and its not spread over a "band" of frequencies - thus they can transmit greater distances than higher power transmitters which are not tuned as well (according to a long discussion I once had with Byon Garabrant - somebody smarter than me please correct this if I'm wrong - heck I'm just an ME). And being that you have line of sight a long, long way from an aircraft, even at low altitude (in line with Sam Buchanan and Pete Howells' recent posts), I believe that you will have pretty darn good coverage with the lower power transmitter.
I understand the desire to have coverage in the mountains if you're in a SAR situation, but if you have a trail of breadcrumbs from higher altitude and then lose signal when you get below ridgeline, wouldn't that still be pretty good? In addition, even with a higher power transmitter I don't think it will help much being below ridgeline and out of line of sight of a digipeater or IGATE.
I have often thought that the ideal is a switch set up for "normal" and "emergency" modes - NORMAL mode consisting of smart beaconing at low power, and EMERGENCY mode being continuous transmission at high power with a mayday message encoded. If Byon and Allen were to design such a product, they would have a real winner for the airborne APRS tranmistter market. (I think that Sam B is considering something like this??)
There are a lot of people a lot smarter than me on APRS, this is just my $0.02 from having casually lurked on various APRS sites for the last 10 years or so and used APRS for some flying I've done in the 182
Anybody interested in a serious discussion about this needs to read APRS designer Bob Bruninga's site about the "Tragedy of the Commons" http://www.ew.usna.edu/~bruninga/aprs/fix14439.html
<snip>Tragedy of the Commons: APRS suffers the classic fate of all limited resources (as well documented since the 1830's See Tragedy). Whenever there is a balance between individual interests and the common good, human nature guarantees the overloading and ultimate demise of the common resource. In this case, APRS throughput. This is easy to understand since the benefit of adding one more packet to the network always immediately benefits the SENDER, but the negative "cost" is spread over everyone else, and NOT the sender. There is no natural solution, other than the establishment of "Golden Rules" to live by for all concerned. <end snip>
Since the explosion in popularity of APRS several years ago, there has been a move afoot to reduce power transmission, number of packets sent, and to reduce the number of bounces allowed from one digipeater to another, as well as to increase the number of digipeaters available (similar to what has happened to cellular telephone networks 10 yrs ago to increase bandwidth). We need to be very careful, since as APRS users in aircraft we hit digipeaters and Igates for hundreds of miles, and have a much greater impact on the APRS system than ground-bound users.
Ron, could you design for the power supply but not install it? That way, you could try the low power installation in the area you fly and see whether coverage is sufficient. Although these are low power transmitters, they are very well tuned to the frequency (with a crystal IIRC) so ALL of the power gets tramsitted on exactly the frequency you want it on, and its not spread over a "band" of frequencies - thus they can transmit greater distances than higher power transmitters which are not tuned as well (according to a long discussion I once had with Byon Garabrant - somebody smarter than me please correct this if I'm wrong - heck I'm just an ME). And being that you have line of sight a long, long way from an aircraft, even at low altitude (in line with Sam Buchanan and Pete Howells' recent posts), I believe that you will have pretty darn good coverage with the lower power transmitter.
I understand the desire to have coverage in the mountains if you're in a SAR situation, but if you have a trail of breadcrumbs from higher altitude and then lose signal when you get below ridgeline, wouldn't that still be pretty good? In addition, even with a higher power transmitter I don't think it will help much being below ridgeline and out of line of sight of a digipeater or IGATE.
I have often thought that the ideal is a switch set up for "normal" and "emergency" modes - NORMAL mode consisting of smart beaconing at low power, and EMERGENCY mode being continuous transmission at high power with a mayday message encoded. If Byon and Allen were to design such a product, they would have a real winner for the airborne APRS tranmistter market. (I think that Sam B is considering something like this??)
There are a lot of people a lot smarter than me on APRS, this is just my $0.02 from having casually lurked on various APRS sites for the last 10 years or so and used APRS for some flying I've done in the 182
rvator51
Well Known Member
Hi Ron,
I have the ant on order but dont know yet if it will work or not. I didnt get the power supply because my Vertical Power VP-100 has a regulated 12 v power out line I can use. I also am not well-versed in this stuff. Noah makes a good point about using the minimum power needed.
Sam Buchanan
been here awhile
Ron, I suggest you get the Micro-Trak 8000 so you will have the option of cranking in more power if you need it. However, I think you are going to get far more range with low power than you realize. But the MT-8000 will cover all bases for you.
Do order the Micro-Volt so you can supply your tracker with regulated voltage.
We are really looking forward to seeing how your tracker will perform in the high country especially in concert with your awesome piloting prowess.
By the way, any antenna you mount will be able to handle max power from the Micro-Trak. Our COM radios are outputting more power than the trackers. Pete is now using a MT-8000 with the Ry-pole antenna and it works great. Check out his flight from today to see the really solid performance he is getting on four watts.
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kevinh
Well Known Member
I'll be installing my little 300mw APRS in my RV tomorrow and flying across the rockies next week. I'll post my tracklogs.
I do have to say I was impressed with the little 300mw output - my house is on a hill in the SF bay area, but even so I was surprised to see that it was hitting digipeters 30 and 100 miles distant from my deck. I suspect that in the plane it should do even better.
I do have to say I was impressed with the little 300mw output - my house is on a hill in the SF bay area, but even so I was surprised to see that it was hitting digipeters 30 and 100 miles distant from my deck. I suspect that in the plane it should do even better.
Sam Buchanan
been here awhile
From the reading I've done, much of this concern can be alleviated by the strict use of the WIDEn-N packet protocol. It isn't necessaryto understand all the details of this because it is the default setup in the Micro-Trak configuration file. WIDEn-N limits the number of "bounces" a beacon causes and greatly reduces frequency congestion over the old TRACE and RELAY protocols of just a few years ago.
Yes, we definitely need to be good stewards of the APRS frequency so we don't have a repeat of the flaming of RVers that occurred recently on the AOPA forum. We don't want hams to regard us as the pariahs of the air. But I don't think that will happen.
300 mW's
At altitude, 300 mW's is plenty of power! In fact, a balloon project called SABEL launched an edge-of-space project with a Micro-Trak 300 on board, and had reported hits on a digipeater 500 km away. I think Pete Howell described digipeater hits at several hundred miles at considerbly less altitude.....
It would not be hard to turn the secondary cofiguration power down. It would take one transistor and a couple of resistors, but I think it is an engenius solution to a non-existant problem. Power is good...especially on the ground, so my suggestion is that you use it when you can. Just transmit with a considerate rate and digipath.
If any of you bought a Micro-Trak 300, and found it just does not have enough oomph for your area, just add our Micro-Amp. You can have between 1 and 12 Watts output, depending on your operating voltage. If thats not enough, power is probably not the problem. VHF requires mostly line of sight to work.
Allen
VHS
At altitude, 300 mW's is plenty of power! In fact, a balloon project called SABEL launched an edge-of-space project with a Micro-Trak 300 on board, and had reported hits on a digipeater 500 km away. I think Pete Howell described digipeater hits at several hundred miles at considerbly less altitude.....
It would not be hard to turn the secondary cofiguration power down. It would take one transistor and a couple of resistors, but I think it is an engenius solution to a non-existant problem. Power is good...especially on the ground, so my suggestion is that you use it when you can. Just transmit with a considerate rate and digipath.
If any of you bought a Micro-Trak 300, and found it just does not have enough oomph for your area, just add our Micro-Amp. You can have between 1 and 12 Watts output, depending on your operating voltage. If thats not enough, power is probably not the problem. VHF requires mostly line of sight to work.
Allen
VHS
kevinh
Well Known Member
A cool article adding more details on Allen's 300 mw tracker from (near) space:
http://www.sbszoo.com/bear/sable/sable3.htm
http://www.sbszoo.com/bear/sable/sable3.htm
Sam Buchanan
been here awhile
Speaking of the Micro-Amp, here is the one I'll be putting in the plane tomorrow:
The Micro-Volt regulated power supply has been piggy-backed on the amp:
This little combo will be stashed up behind the panel with the Micro-Trak. I'll start out running 3-4 watts, just want to see if I can get reliable hits close to the ground.
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higher power
The $20 antenna should work equally well with the 8W, but it will be much more sensitive to bad VSWR. Since I doubt many of us are even checking the VSWR of the antennas we're using, we don't know how much power is reflecting off that bad match at the antenna and flowing back to the transmitter. At 300 mW, that is no big deal, but with 8W peak power, that could blow the final amplifier stage. Allen, any idea about the limit VSWR for our hacked antennas and how much is too much for a 8W transmitter?
Rick Grenwis
RV-6A 190 hours
1st flight with tracker today. See separate report.
The $20 antenna should work equally well with the 8W, but it will be much more sensitive to bad VSWR. Since I doubt many of us are even checking the VSWR of the antennas we're using, we don't know how much power is reflecting off that bad match at the antenna and flowing back to the transmitter. At 300 mW, that is no big deal, but with 8W peak power, that could blow the final amplifier stage. Allen, any idea about the limit VSWR for our hacked antennas and how much is too much for a 8W transmitter?
Rick Grenwis
RV-6A 190 hours
1st flight with tracker today. See separate report.
