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Old Oct 19, 2010, 04:17 AM
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FrSky V1 and V2

Dear all,
FrSky does not make change to output power for V1 and V2, and they have the same range.

Thank you all for your attention.
Best regards!
Eva
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Last edited by Chase Wu; Oct 19, 2010 at 04:31 AM.
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Old Oct 19, 2010, 04:31 AM
Martin - AKA mr.sneezy
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Adelaide, Australia
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Originally Posted by derek4610 View Post
Derek
Derek, feel free to PM me. I think we're both in the RF game so we can get technical better and not bore the cr@p out of everyone
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Old Oct 19, 2010, 04:36 AM
Martin - AKA mr.sneezy
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Originally Posted by derek4610 View Post
DAVX, the output power levels in range check mode did not change. Please perform a range test in normal TX power mode, you will see a difference.

Thanks,
Derek
Dereks dead right, don't draw any conclusions in comparison between ANY modules in range test mode. They all can use different power drops (typically from -20 to -40dBc), and they vary between firmware versions sometimes too.
For instance I've personally measured three different levels from various Spektrum modules over the time I've been testing them....
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Old Oct 19, 2010, 04:57 AM
Or just say Peer
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Quote:
Originally Posted by Daemon View Post
For whatever it's worth, there's an easy way to do a full power test at a relatively
short range. Place your Tx in a microwave oven (which is heavily shielded in the 2.4Ghz
band), and then walk away with your Rx until it jumps to failsafe. Compare the
range of the two versions the same way.

ian
Hi Ian,

good idea, but i performed this test a time ago, without antenna, and even a finger placed over the antenna connector, and it still works fine. May be, i don´t hope so, my microwaveoven is very leaky. Its made from stainless steel which should block microwaves very well i suppose, sadly i have no leak-tester so i have no idea. I leave my kitchen since then when heating somethig up in my mwo.
I was so impressed by this test, that until then i trust absolutely in FrSky´s transmission pattern.
FrSky in MW
Regards Peer
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Old Oct 19, 2010, 04:58 AM
Martin - AKA mr.sneezy
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Originally Posted by RENATOA View Post
Will try to redo the range test asap with two v1 and v2 setups, side by side.
Yep, good idea if you are worried about it.
The best way to compare the version will be to reflash the same module with both firmwares (as different one from the same batch can be +-2dB different IME).

To do a better job of range checking you need to accurately position and orient the antennas repeatably for both tests, you need as much non free space from the ground as possible, and with no metallic reflectors near the test path(wooden ladders etc).
To reduce RF power output to allow a reduced range to be used for testing, a microwave RF attenuator could be fitted between the TX modules RP-SMA connector and the TX antenna, say 20dB or 30dB.
Then find the limit of one version, then see if the other is longer or shorter. Then to make quite sure, change locations and repeat the test and see if it still matches. Even then be a bit cautious about the results, but the evidence will be OK.

One of the big unknowns with Spread Spectrum devices is the Process Gain (or Coding gain) component of the overall system gain figure, of which the RF power is another part. Only the designer will know this (AFAIK) as it's set by the chipping code ratio used in that device. The ratio is in some part set by the throughput data rate needed by the device and the bandwidth available.
This is why for us an actual range test is a good way to compare them I think.

(LOL, I just suggested we not get technical here

Martin
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Old Oct 19, 2010, 05:09 AM
Or just say Peer
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When performing a range test, it is absolute necessary to place the antennas in exact the same place, in german forums there is one RF guru who have measured the radiation pattern of a 2,4 System. The result will astonish the audience, see the pic attached (for example not for reference)
The long green "rock" is the position of the transmitter, and the rest of the pic shows the density of waves received. The ups and downs can be seen, like an egg-board, are in 12cm (4,7") distance, and the pic is inflated to make the difference better recognizable.

Enjoy

Regard Peer

EDIT: See here to get part of the story click
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Old Oct 19, 2010, 05:09 AM
Martin - AKA mr.sneezy
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Quote:
Originally Posted by JollyJoker View Post
Hi Ian,

good idea, but i performed this test a time ago, without antenna, and even a finger placed over the antenna connector, and it still works fine. May be, i don´t hope so, my microwaveoven is very leaky. Its made from stainless steel which should block microwaves very well i suppose, sadly i have no leak-tester so i have no idea. I leave my kitchen since then when heating somethig up in my mwo.
I was so impressed by this test, that until then i trust absolutely in FrSky´s transmission pattern.Regards Peer
That works OK as an adhoc test method to check a TX, the microwave unit output is in the same band as the RC modules, so the shielding works equally well. I think you could leave the antenna on though.
The hassle is the oven is usually in a house, which is full of reflecting surfaces, so it's hard to really be sure about the results if comparing two systems. What it is good enough for IMHO is checking a TX to see if it's still as good or close too as it was last time you did that test.
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Old Oct 19, 2010, 05:14 AM
Martin - AKA mr.sneezy
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Quote:
Originally Posted by JollyJoker View Post
When performing a range test, it is absolute necessary to place the antennas in exact the same place, in german forums there is one RF guru who have measured (on 80.000€ reference-equipment) the radiation pattern of a 2,4 System.
Great image Peer. Imagine what putting a metallic item like a drink can or square cake tin in the field, it would distort it even further.
In the past I had access to a proper RF shielded chamber at my work, it would have been great for these tests also. Maybe one day I'll have that sort of thing at hand again
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Old Oct 19, 2010, 05:54 AM
Or just say Peer
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Originally Posted by debianhot View Post
Sorry to tell you that WinXP will not run on an 386 .
You will need something of at least 700Mhz and 512Mb of ram.
The kwickest way would be tot find a friend (or work) with a computer with true rs232 and WinXP on it.
5 to 6 year old computers normaly would have both , should be plenty of them out there .
Hi dh,

sorry, didn´t got you?

I use, as wrote, an pc with win xp and physical com port (in fact two of them). A friend also has another pc which i used to test on, but result is still the same, getting of UID and nothing further.
Wrote that i will dig out my old 386 with win 3.11 to have another try with this. And i ordered an PIC with this FTDI device on it, just to be shure, meanwhile i go with V1 firmware.

Regards Peer
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Old Oct 19, 2010, 05:55 AM
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Range check w/ RP-SMA 50 ohm terminator.

If you want to do a range check in normal tx mode use a RP-SMA 50 ohm termination load in place of the antenna, there only a few bucks. You will still be radiating and any power level changes will be noticed by distance.

Great tool for range checking under full power and finding issues before you crash your aircraft.


Derek




Quote:
Originally Posted by PLMS View Post
Great image Peer. Imagine what putting a metallic item like a drink can or square cake tin in the field, it would distort it even further.
In the past I had access to a proper RF shielded chamber at my work, it would have been great for these tests also. Maybe one day I'll have that sort of thing at hand again
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Old Oct 19, 2010, 07:21 AM
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Not a bad Idea, but will not work.

A microwave oven is not a faraday cage for the type of test needed, the RF will refract. This is not a valid test and will not work. Not a bad idea though.


Derek


QUOTE=JollyJoker;16326340]Hi Ian,

good idea, but i performed this test a time ago, without antenna, and even a finger placed over the antenna connector, and it still works fine. May be, i don´t hope so, my microwaveoven is very leaky. Its made from stainless steel which should block microwaves very well i suppose, sadly i have no leak-tester so i have no idea. I leave my kitchen since then when heating somethig up in my mwo.
I was so impressed by this test, that until then i trust absolutely in FrSky´s transmission pattern.
FrSky in MW
Regards Peer[/QUOTE]
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Old Oct 19, 2010, 07:36 AM
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will do, after more tests are done.

FrSky is using a 2dbi antenna, this will add 2dbm, but now were talking about ERP. The output power should be >80 mw measured at the antenna connector. Remember: all these 2.4Ghz RC radio's seem to be following IEEE 802.15.4.

Derek

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Originally Posted by PLMS View Post
Derek, feel free to PM me. I think we're both in the RF game so we can get technical better and not bore the cr@p out of everyone
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Old Oct 19, 2010, 09:54 AM
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Quote:
Originally Posted by pmackenzie View Post
The PPM signal is fed into the FrSky tx module.
It is converted into digital data and sent to the receiver as a packet of information. It does not have to send it on a servo signal by servo signal basis.(I doubt it does, since others don't)
The receiver takes this packet and generates the output servo signals.
It could do this in order just like a shift register PPM decoder, but it does not have to. I know XPS for example does not, it starts them all at about the same time, slightly shifted to avoid jitter as the pulses end.

There is nothing new about this, PCM systems also put out the signals in non-sequential order.

If you look at cyborg's post here, it looks like FrSky starts 1,2and 3 at the same time, then when the last of that group goes low puts out 4,5,and 6. Then 7 starts after that.
Not sure what is going on with ch 8 in his output

So if you connect some sort of external device (gyro, governor,mixer, etc) to the servo signals and it expects there to be non-overlapping inputs then you might have problems.


Pat MacKenzie
Hi Pat,

You are correct. Channel 8 shows up like that, because I did not have a probe connected to it....just the battery...but if I did, it would follow the order you mention...

I was wondering if someone can confirm this from FrSky? If you look at my graph, you will see that it basically has overlapping channels...nothing per say wrong with that, but I am into flying Quads. many of the Quad boards on the forums require a PWM non-overlapping signal (Since they play tricks with acquiring the control signals of the remaining channels from the gaps between say odd numbered ones).

As such, if this TX/RX combo is going to be used, there arises the need for a PWM to PPM converter, which is not the cleanest way to go.....

I was wondering is anyone has confirmed this, or has any comments?

Better yet, any chance of having firmware, that changes this to sequential?? That would be AWESOME!
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Old Oct 19, 2010, 10:45 AM
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Quote:
Originally Posted by JollyJoker View Post
Hi dh,

sorry, didn´t got you?

I use, as wrote, an pc with win xp and physical com port (in fact two of them). A friend also has another pc which i used to test on, but result is still the same, getting of UID and nothing further.
Wrote that i will dig out my old 386 with win 3.11 to have another try with this. And i ordered an PIC with this FTDI device on it, just to be shure, meanwhile i go with V1 firmware.

Regards Peer
Understood wrong , my fault.
Still bad as "I think" the update program is only suitable for winxp , vista and seven . It will not work in win 3.11.
Realy bad luck to test with 2 suitable pcs and none did work .

Trying to help , I have a (silly?) list of things you can do while you wait for the FTDI cable.

1) Check if you have ADMINISTRATOR rights on the pc , if not then this is a problem .
2) Try to test the com port itself by using the suplied cable ,not to update your tx module but to monitor the telemetry data that comes OUT of it.The program comes allso in your CD and you will need allso to have switched on your telemetry rx (or there will be no telemetry data sent back to the tx module). If there is no comunication out then I think you have a hardware/configuration problem in the com port or cable.
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Old Oct 19, 2010, 11:01 AM
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Quote:
Originally Posted by Daemon View Post
For whatever it's worth, there's an easy way to do a full power test at a relatively
short range. Place your Tx in a microwave oven (which is heavily shielded in the 2.4Ghz
band), and then walk away with your Rx until it jumps to failsafe. Compare the
range of the two versions the same way.

ian
<JOKE MODE ON>

Wife : "Darling what did you put in the microwave that just exploded when I switched it on ? "

Remember not to forget the tx or video cammera inside the oven !!

<JOKE MODE OFF>
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