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Old Dec 24, 2012, 09:27 AM
C-c-c-custom!
United States, NM, Albuquerque
Joined Nov 2011
330 Posts
Antennas/Satellite RXs

Guys - there are a few rather serious misunderstandings I see here regarding the antenna stuff. I'm a sailplane guy with lots of carbon fuselages, and I like to fly FAR away in confidence if I need to for lift.

1. Whiskers: The whisker bit is NOT the only functional part of the antenna. That whisker needs a counterpoise in order to radiate/receive effectively. Consider a high-priced Spektrum receiver. The whisker is an approximation of a 1/4 wave whip, functioning against the ground plane on the bottom layer of the receiver board. For best performance, both the whisker and ground plane (at least partially) should be in sight. It should be noted that the size of the receiver modules within these devices is not sufficient to allow a proper 1/4 wave counterpoise to be realized.

2. Remotes: First bit of info, a remote is a redundant receiver with only one antenna. Any manufacturers inexpensive twin antenna receiver systems use an antenna switch to provide alternating means of reception - there are losses associated with this. Second bit of info, the remote with the twin whiskers is a functional 1/2 wave dipole...one of the leads is the active sense element, the other is a matched counterpoise connected to ground. Again, both the active sense element and the counterpoise should be in view of the TX. This is a superior antenna to the 1/4 wave whip approximations otherwise seen. So, a remote provides A) Redundant RF module [reliability, lower loss RF path], B) Superior antenna design when properly installed.

3. Truncated Coax Antennas: The truncated coax antenna is very popular with many manufacturers. It is basically a 1/4 wave whip yet again, but now the coax shield must serve as the counterpoise - this means 1/4 wave or more of the coax itself should be exposed. This is a huge compromise, as the current distribution on the coax shield is unpredictable. A step-around is the end-fed dipole, comprised of a true tubular counterpoise insulated from the coax except AT the feedpoint. Big difference in terms of VSWR and radiation pattern predictability.

In summary, the whisker is not the only part of the antenna that needs to be exposed or otherwise provided. Remotes provide better antenna performance combined with redundancy that I believe is indeed valuable.

Been lurking and watching the good work going on here guys. This is the first time I've had the opportunity to come forward and contribute.


-Matt
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Old Dec 28, 2012, 06:41 AM
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Russian Federation, Kemerovskaya oblast, Kemerovo
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my firmware for dsmX receiver from orange 6 ch receiver work. need more code rewrite, too many C overhead. and re-sync when signal lost. try to adding back telemetry, problem sync with 9-bit PPM channels out. need more free time.
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Old Dec 28, 2012, 06:49 AM
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added one idea: get 2 receivers, binded in pair, first for 1-6 chan, second for 7-12 chan =) code write, but unchecked.
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Old Dec 30, 2012, 12:31 AM
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found one interest thing: if i lost the signal and nothing to do to resync work more faster then resync procedure. confused.
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Old Dec 30, 2012, 06:36 AM
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Toronto (Don Mills), Canada
Joined Dec 2002
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A while back a guy reported that you could alternate model match numbers with the DX4e module and thus control 2 receivers.
I could never get it to work though so he might have been full of

Post is here:
http://www.rcgroups.com/forums/showt...3#post20316163

Had I got it to work I would have put it forward to be included in ER9X to get around the 6 channel limit.

When I tried it neither receiver worked, but I had genuine Spek, he said he was using Orange.
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Last edited by pmackenzie; Dec 30, 2012 at 06:53 AM.
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Old Dec 30, 2012, 06:48 AM
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Quote:
Originally Posted by RW9UAO View Post
found one interest thing: if i lost the signal and nothing to do to resync work more faster then resync procedure. confused.
This is what I'd expect actually. You know the signal will come around in < 23 hops (ignoring CRC) or <46 (using CRC) (assuming there is a signal)
If you search, you have no guarantee because you are very likely to miss the hop by changing your position. However, if you are in a noisy environment, someone else may be transmitting on the channel you are sitting on such that you never see the data if you don't scan. So you could sit there for 23 hops, move to the next channel and then repeat and probably get better results.
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Old Dec 30, 2012, 08:18 AM
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pmackenzie i do not use any Spektrum modules with original firmware, so can`t help you. i write my software for full 14 channel.

PhracturedBlue maybe. CRC checked after receive, no IRQ on timeout - this is a lost signal.
i need more experimental. variants: stay on one channel and wait, goto next-next-next channel forward and backward.
now i kill some bugs, one is a channel impulse jitter.
have one more bug - too small range. need a change receiver, have one. or some flag in CYRF registers check.

damn, i need english teacher.
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Old Dec 30, 2012, 08:19 AM
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Spektrum guys do not want to help us? =)
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Old Jan 01, 2013, 03:39 AM
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I'm hoping to eventually make, or better yet reprogram USB receiver stick for a wireless mouse a HID joystick receiver for the Spektrum radios. From my reading of this thread the binding and reception/decoding of DSM/2/x are all known? It seems the walkera telemetry module is the easiest way to get my hands on a wired up cypress chip for testing. Has anyone already done something like this? I'd always rather build off of the shoulders of giants rather than start from scratch if I can help it.
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Old Jan 01, 2013, 04:19 AM
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Quote:
Originally Posted by rszasz View Post
I'm hoping to eventually make, or better yet reprogram USB receiver stick for a wireless mouse a HID joystick receiver for the Spektrum radios. From my reading of this thread the binding and reception/decoding of DSM/2/x are all known? It seems the walkera telemetry module is the easiest way to get my hands on a wired up cypress chip for testing. Has anyone already done something like this? I'd always rather build off of the shoulders of giants rather than start from scratch if I can help it.
Why not use this Serial output, SpektrumSatRx Library nearly done...
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Old Jan 02, 2013, 05:10 AM
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My end goal is a small usb stick, and since there are a lot of RC controllers using the cypress usb LP chipset, finding a usb stick with one onboard already seemed the fastest way to get to something others can use and extend.

Thanks for the info on the spektrum satellite. If there is any interest (and if I manage to do it) I'll release the code I use to get a satellite receiver -> USB joystick using either a tinyavr or one of the stellaris launchpads I have.
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Old Jan 13, 2013, 08:41 AM
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some good, some not good news. here is dsmX receiver from orange 6 channel. source not full.
realised: dsmX bind, receive, auto resync, some telemetry (like RSSI and packets lost), true 9 bit PWM channels out (no sum-PPM, have not enouth CPU time), fail-safe.
working in a pair, one receiver for 1-6 channel, second for 7-12 channels.
not using satellite, not using digi channel info out UART.
and now, ta-dam. they all does not work correctly. distance at full 100 mWt - 5 meters, at low power - 2 meters. i don`t know what happen. i change receiver, it work parallel with AR8000, TM1000. Spektrum modules work fine, i lost the signal.
i write code for dsmX transmitter. it work correct, AR8000 and TM1000 get a good signal. my receiver lost. RSSI is strong - 21-31. i put off wifi router, not better.
need some thinks.
dsmx_rx
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Old Jan 13, 2013, 09:59 AM
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USA, KY, Louisville
Joined Oct 2002
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Orange versus Spectrum

Hi Guys,

After looking 'inside' these RX's, when everything is said and done, are they the 'same', as in do they end up doing the same job equally well?

Thanks
Gordy
I fly JR/Spectrum
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Old Jan 13, 2013, 10:05 AM
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Quote:
Originally Posted by RW9UAO View Post
and now, ta-dam. they all does not work correctly. distance at full 100 mWt - 5 meters, at low power - 2 meters. i don`t know what happen. i change receiver, it work parallel with AR8000, TM1000.
Maybe your receiver simply has a defective RF circuit?
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Old Jan 13, 2013, 11:39 AM
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Germany
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Quote:
Originally Posted by RW9UAO View Post
some good, some not good news. here is dsmX receiver from orange 6 channel. source not full.
realised: dsmX bind, receive, auto resync, some telemetry (like RSSI and packets lost), true 9 bit PWM channels out (no sum-PPM, have not enouth CPU time), fail-safe.
working in a pair, one receiver for 1-6 channel, second for 7-12 channels.
not using satellite, not using digi channel info out UART.
and now, ta-dam. they all does not work correctly. distance at full 100 mWt - 5 meters, at low power - 2 meters. i don`t know what happen. i change receiver, it work parallel with AR8000, TM1000. Spektrum modules work fine, i lost the signal.
i write code for dsmX transmitter. it work correct, AR8000 and TM1000 get a good signal. my receiver lost. RSSI is strong - 21-31. i put off wifi router, not better.
need some thinks.
Attachment 5444242
If I understand you correctly, you have hopping running stable as long as you are nearby ?
Strange thing, one of the few reasons I could think of would be: You are always one channel (or some fixed offset) away from tx ? Any chance of something like this ?
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