thUndeadMod v3.4 - openLRS S**T just got real :)

[Coyote]

Ok, back in from test number 4

Thundead v3.5 code, 459 MHz, no hopping, 100mw

On first boot up the RSSI showed 0.04 to 0.10, after two more systems resets the RSSI stayed at a constant 3.2v RSSI so I began the test.

First check point at 2.4km no twitches coming up to the check point put doubts in my mind. I got the plane out, no rx link, tried a few different orientations and then it linked. Only for about 10 seconds. Then it lost link and I never got the link bavk, tried switching it off / on, nothing :(

[thundead]

so its not my hopping algorithm as its working great on 433 :). read post ^^^

Ok, back in from test number 4

Thundead v3.5 code, 459 MHz, no hopping, 100mw

On first boot up the RSSI showed 0.04 to 0.10, after two more systems resets the RSSI stayed at a constant 3.2v RSSI so I began the test.

First check point at 2.4km no twitches coming up to the check point put doubts in my mind. I got the plane out, no rx link, tried a few different orientations and then it linked. Only for about 10 seconds. Then it lost link and I never got the link bavk, tried switching it off / on, nothing :(

[Devonian]

Channel spacing on 459MHz is 25kHz.
We cannot get 25kHz multiples, so we must use multipes of 10kHz.

So from a startup frequency of 459.000 we can get, for example,  459.000, 459.050, 459.100, 459.150, 459.200 etc

and for a startup frequency of 459.025, we can get, for example, 459.025, 459.075, 459.125, 459.175, 459.225 etc

http://www.ukrcc.org/459mhz.html

Another code change Mihai?  :D

Nigel.

[Coyote]

Nope its not the hopping, even when sat on one channel full power, it still can't get a solid link :(

[Splashy]

Channel spacing on 459MHz is 25kHz.
We cannot get 25kHz multiples, so we must use multipes of 10kHz.

So from a startup frequency of 459.000 we can get, for example,  459.000, 459.050, 459.100, 459.150, 459.200 etc

and for a startup frequency of 459.025, we can get, for example, 459.025, 459.075, 459.125, 459.175, 459.225 etc

http://www.ukrcc.org/459mhz.html

Another code change Mihai?  :D

Nigel.

An interesting link especially the "For aircraft use, 434.025 to 434.775 is recommended."

That solves our problem !

[papa_lazerous]

An interesting link especially the "For aircraft use, 434.025 to 434.775 is recommended."

That solves our problem !

Where does it say 434.025 to 434.775 on that page?

[Splashy]

On this page http://www.ukrcc.org/35mhz.html

[papa_lazerous]

On this page http://www.ukrcc.org/35mhz.html

Correct me if I am wrong, but in that context in which it is written it is talking about telemetry

[Splashy]

You are probably right. A bit confusing .. shame I have already reflashed to those frequencies

[zitron]

So what other variables can we eliminate?

Things I can think of;

1. Use proper 459 antennas
2. Try somewhere with a lower noise floor
3. Find out what is causing the start up problem


Also I don't see the need to worry about channel spacing, unless you are flying with other people. It's not like anyone else is using the band. Every time you half frequency deviation you reduce signal-noise 4 times.

[papa_lazerous]

It is most definately for telemetry mate ;)

You need to be a little careful because if you pick the wrong frequency you can seriously pi$$ off some HAM geeks  this site shows allot of the frequency allocations http://www.wibble.co.uk/links/ukspectrum/spectrum.html#b400 you want to stay well away from UK repeaters :)

[Splashy]

It is most definately for telemetry mate ;)

You need to be a little careful because if you pick the wrong frequency you can seriously pi$$ off some HAM geeks  this site shows allot of the frequency allocations http://www.wibble.co.uk/links/ukspectrum/spectrum.html#b400 you want to stay well away from UK repeaters :)

I agree, this is how it is meant to be read.

I also agree about not picking the wrong frequency and was not really suggesting using them .. although .. IF one were to use a frequency other than 459 and yesterday Thundead suggested 435, what would be a good frequency to use. Surely one allocated for RC use, albeit for telemetry. If those frequencies are allowed for communicating between an aircraft and the ground, and vice versa, then would this not raise as many eyebrows or tempers since it is only a difference in the data that is being transferred .. and why would you want to send telemetry from the ground to the aircraft anyway.

Of course I want to use 459 but I have a friend who is asking about this specific issue so I thought I would ask for him.

[Splashy]

I just went outside in the dark and suspiciously walked around the neighbourhood with my RSSI measurement box and did some experiments.



Setup:

Antenna: 15.2mm cut for 459MHz
Board: my own DIY RFM22B running custom code, should perform the same as OLRS
Settings: single frequency (no hopping), 38400 Baud, 19.6kHz frequency deviation, 40-50Hz PPM from er9x radio

Procedure:

1. Set frequency to 459.5MHz, output 1dBm
2. Walk with gps to ~50m
3. Write down RSSI
4. Repeat for 20dBm
5. Repeat for 435.5MHz
6. RSSI is calculated: RSSI  = raw value/2 - 130

Results:

I have attached the results. I would say my measurement uncertainty is +/-5dBm, and +/-5m for distance.

Conclusions:

From Dennis Frie's previous results, I would expect a ~3dB difference. I did not see a measurable difference between 459.5 and 435.5 using my crude method. It is likely that if I used proper 435MHz antennas I will be able to see a bigger difference. I have used 433 antenna on 459 before, and saw 3-4dB difference, so this is in line with Dennis Frie's predictions.

I have to say that the RF22 module works just fine at 459MHz, maybe with a small penalty. No where near as dramatic as you guys seem to be seeing. Clearly something else must be the problem. Have you guys tried disabling frequency hopping? 459MHz is very clean where I live I simply don't see the need for FH.

Would it be possible for you to post which registry values you set please. Also, are there any glaring differences between the schematic for the OpenLRS and your design. Obviously if you are getting good results on 459 then we ought to be comparing code and hardware.

[Devonian]

if you pick the wrong frequency you can seriously pi$$ off some HAM geeks

Oi, watch who you're calling a Ham geek  ;D

I've been a licenced 'geek' for 30+ years.

Nigel

[zitron]

Would it be possible for you to post which registry values you set please. Also, are there any glaring differences between the schematic for the OpenLRS and your design. Obviously if you are getting good results on 459 then we ought to be comparing code and hardware.

Attached my current settings. If you need any other registry values let me know.

Also I wouldn't say that I'm having good results. I have not yet done a full range test, kind of difficult without a car! All I can say is that I did not see any dramatic differences in short range tests.

I don't think there are any functional differences between my setup and OLRS, the hard work is done by the RF22 module, which should perform identically. You can find details in my arduino forum thread posted earlier. Although the fact that you guys are having issues with the connection and RSSI when you turn on the receiver is really strange. I have never had anything like that...