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Old Jan 01, 2012, 08:12 AM
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HiTec A-9 and Sailplanes

I've been out of the hobby for a while(longer than I care to say) but recently have reignited the flame. I've been playing with helicopters and having a great time but my first love has always been sailplanes. I have an Aurora 9 and am planning on putting one of the kits I never finished in the air. The question I have is about range. With the short BODA antenna it seems there would be limited range. I am used to the 72mhz system, long antenna and control as long as you could see the aircraft. So far I am a little hesitant about the 2.4 GHZ system. The short antenna gives me the creeps. Also having it inside the fuselage as with the 72mhz system, I worry about blocking the signal. Do I have to expose the BODA? How well does this work in a thermal plane at high altitude?
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Old Jan 01, 2012, 08:39 AM
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No need to worry. That Hitec kit will out-range almost anything out there, with the BODA buried inside the fuzz (that's assuming the fuzz is not pure carbon). I have some niggles about Hitec's software (when it comes to updating), but range is the one area where it is exceptional.

Chris
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Old Jan 01, 2012, 11:57 AM
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2.4GHz is an ENTIRELY DIFFERENT GAME from what you are used to on 72MHz.

Read Mike Lee's 2.4 Chronicles for a quick primer.

http://mysite.verizon.net/respri94/id16.html
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Old Jan 01, 2012, 08:15 PM
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Originally Posted by tkallev View Post
2.4GHz is an ENTIRELY DIFFERENT GAME from what you are used to on 72MHz.

Read Mike Lee's 2.4 Chronicles for a quick primer.

http://mysite.verizon.net/respri94/id16.html
Thanks for the replies, I do realize there are some differences but Im still new enough to need to ask. cvansch what problems have you had with firmware updates? I'd been lucky with no issues so far.
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Old Jan 01, 2012, 08:22 PM
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eatfire,
I am and have been using an A-9 in electric and pure sailplanes. Range has never been an issue even when spec'd out. On several I have put heatshrink over the antenna and I do have them poked outside the fuselage, not needed but it makes me feel better. There are a few things that I have found to make the system easier to work with:

1. If possible have the rx where you can see the LEDs and get to the link button and data port. The link button is needed to set the failsafe settings and the data port is needed if you update the firmware and it the rx is buried in the fuse it can be a pain.

2. As with any 2.4Ghz, use a 5 cell NiCad/NiMh or a 2 cell LiFe. I prefer the 2 cell LiFe and no regulator is needed if the servos are rated for 6V.

3. If you update the firmware on the A-9 check every bit of mixing or predone functions as I have seen where the mixing can get confused from the update. Somewhere there is a spreadsheet that was put together by Fredz69 to log all the settings for a model. The HiTec model save and reload seems to have the same issues with the update.

4. As with every system, do a range check. If it has any problems err on the side of safety and figure out what is going on before flying.

Alan
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Old Jan 02, 2012, 03:54 AM
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Originally Posted by eatfire View Post
. cvansch what problems have you had with firmware updates? I'd been lucky with no issues so far.
Hi, see: http://www.rcgroups.com/forums/showthread.php?t=1562289.

Are you aware also of this monster thread: http://www.rcgroups.com/forums/showthread.php?t=1141715
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Old Jan 02, 2012, 06:17 AM
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Originally Posted by jh2rc97 View Post
2. As with any 2.4Ghz, use a 5 cell NiCad/NiMh or a 2 cell LiFe. I prefer the 2 cell LiFe and no regulator is needed if the servos are rated for 6V.
Why?
The hitec rxs work down to a low voltage.
The rxs don't draw much current
The rxs have battery telemetry (except minima).

5 cells packs in fact will go flat quicker than a 4 cell (ohms law).
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Old Jan 02, 2012, 06:19 AM
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anyway,

in answer to the questions the range is fine and the tx is more than adequate for mixing.

There are people flying many different 2.4ghz systems with no problems. I use hitec - no problems. Never had a problem with other 2.4ghz systems or 35mhz range either though.
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Old Jan 02, 2012, 10:03 AM
Lou
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United States, VA, Waynesboro
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Quote:
Originally Posted by eatfire View Post
The question I have is about range. With the short BODA antenna it seems there would be limited range.
I have the A9 and have not had problems with range or integrity of signal. Thus far it has worked as advertise.

I second the comment by cvanscho about software having issues at times. The software for upgrades seems to be amatuerish and has been problematic for users. One example here and my solution:

http://www.rcgroups.com/forums/showthread.php?t=1494439

I do not know if that problem was fixed or not. As well, users seem to get caught on the procedure for doing updates on the various A9 family of gear. This due again to poor implemention of the software.

Still, the A9 is the best radio I have owned. I have even come to like it better than my EVO 12 and I bought the A9 to replace an Airtronics SD-10G ( which I did not care for ).
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Old Jan 02, 2012, 10:57 AM
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Originally Posted by satinet View Post
Why?
The hitec rxs work down to a low voltage.
The rxs don't draw much current
The rxs have battery telemetry (except minima).

5 cells packs in fact will go flat quicker than a 4 cell (ohms law).
The main reason, voltage headroom. Again I prefer the 2s LiFe over a 5 cell NiMh. If someone is going to use NiMh then I would recommend a 5 cell over a 4 cell. This way if a cell goes (as long as it does not fail open) you still have a 4 cell pack and a chance of getting down without tearing something up (using telemetry to know the voltage has dropped).

The rx does not draw much current but servos do.

Alan
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Old Jan 02, 2012, 11:29 AM
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Originally Posted by jh2rc97 View Post
The main reason, voltage headroom. Again I prefer the 2s LiFe over a 5 cell NiMh. If someone is going to use NiMh then I would recommend a 5 cell over a 4 cell. This way if a cell goes (as long as it does not fail open) you still have a 4 cell pack and a chance of getting down without tearing something up (using telemetry to know the voltage has dropped).

The rx does not draw much current but servos do.

Alan
This makes no sense. With a 5 cell battery you have 5 possible failure points (cells, plus their connections). With a 4 cell you have only 4.

As satinet pointed out, it's not only about voltage: this isn't a petrol engine where there is "no substitute for cubic inches". Bigger (voltage) isn't better. Bigger cells (form factor), yes.
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Old Jan 02, 2012, 01:34 PM
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I am guessing this 5cell thing is due to spektrum brown outs? Not had an issue with 4cell on my MPX setup, and I guess the same goes for its sister Hitec
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Old Jan 02, 2012, 03:18 PM
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Quote:
Originally Posted by jh2rc97 View Post
The main reason, voltage headroom. Again I prefer the 2s LiFe over a 5 cell NiMh. If someone is going to use NiMh then I would recommend a 5 cell over a 4 cell. This way if a cell goes (as long as it does not fail open) you still have a 4 cell pack and a chance of getting down without tearing something up (using telemetry to know the voltage has dropped).

The rx does not draw much current but servos do.

Alan
Even if that weren't debatable, it is not something to do with 'all 2.4 systems'. Servos draw the same current on 2.4GHz or 72mhz.
As the hitec system works down to similar voltages as 72 mhz gear, your comment makes no sense.
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Old Jan 02, 2012, 05:28 PM
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To the OP:

I've flown FPV with the A9 out to 4400ft without problems. Any normal plane would have long been out of sight by then. Don't let the short antennas bother you. Antenna length is inversely related to frequency: high frequency (like 2.4GHz) = short antenna. They're just as well-tuned to their frequency as your meter-long antenna is to 72MHz. The output power of the radio is often less but the digital protocols these things work on really work well for rejecting interference that would otherwise reduce range and cause glitches.

The A9 is a great radio for sailplanes. Fly at ease.

kendall
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Old Jan 02, 2012, 06:14 PM
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Originally Posted by satinet View Post
Even if that weren't debatable, it is not something to do with 'all 2.4 systems'. Servos draw the same current on 2.4GHz or 72mhz.
As the hitec system works down to similar voltages as 72 mhz gear, your comment makes no sense.
This is my advice from years of flying. All processor based rxs have a reset voltage and the Optimas are 3.5V. 72Mhz rxs will operate well below 3.5V. Power issues have been an issue for many people converting from 72Mhz to 2.4Ghz. Here is Mike Mayberry's post on the reset voltage:

http://www.rcgroups.com/forums/showp...&postcount=165

If the same servos are used in a 72Mhz or a 2.4Ghz system the current draw for the two different setups is the same or close. The difference is the point at which the rx stops communicating with the tx. Since all batteries will start to sag under load the idea would be to get either enough headroom to not have to worry about it (not the best idea) or get batteries that do not sag as much (LiFe batteries and A123s if they will fit). If the reset voltage is 3.5V and the nominal voltage of a 4 cell pack is ~4.8 volts there is not much room. With a 5 cell pack there will be more current draw per servo but there is still more headroom for the rx. I do not wish to get in a contest about this as it is well documenting in the groups here and elsewhere on the internet. With a simple lab power supply these voltage reset points can be tested. Good luck and I am only trying to help someone reduce the chances of a non-pilot related crash.

Alan
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