Hardware Choices?

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SpaceManMat
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Re: Hardware Choices?

Postby SpaceManMat » Tue May 16, 2017 7:52 pm

OverTheTop wrote:
I must stress this. Make sure you have the correct firmware loaded


It does not necessarily need to be the correct firmware. Even with the incorrect firmware loaded there would be no problems using the system if the frequency selected puts your system within our ISM band. The class licence states 915-928MHz for the ISM band. Any value between 916MHz and 927MHz (center frequency) will keep you within the LIPD class licence. These channel frequencies are 1MHz inside the band limits to ensure all emissions are kept within the band.

I have one of the earlier units that were not user programmable for frequency. I deliberately specified it to be 923MHz to make sure it was legal.

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True but you don't want to have to reprogram in the field because someone's on your frequency and have to try and figure out what the legal frequency is. Only reason to have another firmware is if your about to launch overseas.
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Re: Hardware Choices?

Postby OverTheTop » Tue May 16, 2017 8:35 pm

Don't need to have other firmware to launch overseas. Just need to make sure you are on the correct frequency in the country you are using it in. I was doing some ground testing on the TRS whilst in Singapore recently. I made sure I complied with their requirements whilst I was on their territory. No need to change firmware, just know what you are doing :D

It is not up to the firmware author to hold everyone's hand for their product in all the assorted countries around the world. It is tough enough making product without that. The author can take the dumb operators out of the problem to some degree, but it probably is not his responsibility. We are doing rocket science after all :D .

True but you don't want to have to reprogram in the field because someone's on your frequency and have to try and figure out what the legal frequency is.

Standard problem on the field. Could happen whatever unit/frequency you are using. That's why frequencies need to be noted at launches. The newer units have an ID number as well as the frequency, so they can share the frequency to some degree I believe, although having clear air would be a better situation. Again, it is the user's responsibility. If you don't know what is legal to use, keep it as is and wait till the channel is clear.
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Re: Hardware Choices?

Postby SpaceManMat » Wed May 17, 2017 9:37 am

On other tracking news it looks like there will be a new feather weight tracker, apparently Adrian has been working hard the last couple of months on this. No idea about an Au version or freq etc.

Also you should all probably be aware the Raven 3 has just had its last production run due to its components not being produced. So you should all consider your flight inventory now as there may be a while where no replacement altimiter is available. IMO every serious HPR rocketeer should have at least one of these units.
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Re: Hardware Choices?

Postby OverTheTop » Wed May 17, 2017 9:47 am

IMO every serious HPR rocketeer should have at least one of these units.


+1. I have seven of them :shock:
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Re: Hardware Choices?

Postby drew » Wed May 17, 2017 12:38 pm

SpaceManMat wrote:On other tracking news it looks like there will be a new feather weight tracker, apparently Adrian has been working hard the last couple of months on this. No idea about an Au version or freq etc.

Also you should all probably be aware the Raven 3 has just had its last production run due to its components not being produced. So you should all consider your flight inventory now as there may be a while where no replacement altimiter is available. IMO every serious HPR rocketeer should have at least one of these units.


Maybe a RavenPlus v2? As I mentioned on TRF I do believe the addition of a mag switch and the removal of the need for a common rail would be two improvements I'd love to see Adrian incorporate in a future product.

Edit: to eliminate confusion I'm referring to the replacement product Adrian produces when he decides to design a new FC. As for the tracker, my gut feeling is that it'll be a 70cm variant. At least I hope so.
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Re: Hardware Choices?

Postby CATO » Wed May 17, 2017 2:53 pm

Subject: Hardware Choices?

drew wrote:So unless you've independently confirm your frequency usage with something like an RF Explorer (http://rfexplorer.com/models/)


Just came across this from Hobby King https://hobbyking.com/en_us/catalog/product/view/id/63761/s/handheld-spectrum-analyzer
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Re: Hardware Choices?

Postby OverTheTop » Wed May 17, 2017 4:59 pm

Some basic test gear is coming out at amazing prices these days. Specialist items now are trending towards commodities.

I'll stick with the CXA. Not quite DC to daylight but 9kHz-13.6GHz is good enough, especially considering it is well optioned (I made sure of that :wink: ). Ours is used for international certification testing so is calibrated regularly. Luxury...
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Re: Hardware Choices?

Postby martymonsta » Wed May 17, 2017 7:56 pm

OverTheTop wrote:OK. Time to put some actual measurement data on the output of the EggFinder product.

ACTUAL MEASUREMENTS OF EGGFINDER TRS
The unit tested is a recently purchased Eggfinder TRS, using the Hope RF HM-TRP-915 RF module.
The EggFinder is targeted to fit within the LIPD class licence, in the 920MHz ISM band, as defined by the ACMA. The relevant legislation can be found here:
http://www.legislation.gov.au/Series/F2015L01438
The relevant section is Schedule 1, item 58, Digital modulation transmitters. The requirements are:
    Frequency: 915-928MHz
    EIRP Max: 1W
    Power Spectral Density: <= 25mW/3kHz
Note that the versions of the Eggfinder shipped to Australia have band limitations imposed by the firmware that keep it more than 1MHz away from the edge of the defined band. This is to ensure that the requirement of all the emission falling within the band and not spilling into adjacent services. Overseas units are permitted to be used in Australia providing the frequency is set to be within our ISM band and no spectrum spills over into adjacent services.

SETUP
The Eggfinder TRS was plugged directly into an Agilent CXA signal analyser. The device under test was set to "Flight Mode" to commence transmissions.
SetupResize.jpg

PEAK POWER
Peak power was measured as 18.04dBm which converts to 63.7mW.
PowerPeak.png

POWER SPECTRAL DENSITY
PSD was measured next. Max hold function is used to ensure any higher power pulses are caputred faithfully. It is going to read higher than a result with a shorter averaging time (approximately 13dBm/95kHz higher in this case) which would be more like the actual emission density. This is a result of averaging the FSK modulated waveform over many scans.
The result is 21.8dBm/95kHz, or 151mW/95kHz. Working back to 3kHz (151 x 3 / 95) = 4.77mW/3kHz
PSDMaxHold.png

CONCLUSIONS
Maximum power was measured as 63.7mW, which is well under the 1W EIRP requirement.
PSD was measured as 4.8mW/3kHz, which is well under the 25mW/3kHz PSD requirement.
The Eggfinder TRS tested meets the criteria for the LIPD class licence as per the amended Radiocommunications Act 1992 (LIPD Class license 2015, compilation date 4MAY2016)


I never used/owned an EggFinder, I hate soldering. However, I do have one question about this test and the operation of the EggFinder. My understanding of the LIPD license is that it has a EIRP Max: 1W and requires a frequency hopping transmitters must use a minimum of 20 hopping frequencies. Does the EggFinder do this, because other posts seem to indicate that the frequency is fixed?

SpaceManMat wrote:True but you don't want to have to reprogram in the field because someone's on your frequency and have to try and figure out what the legal frequency is...


So does it use a minimum of 20 hopping frequencies?
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Re: Hardware Choices?

Postby OverTheTop » Wed May 17, 2017 8:22 pm

So does it use a minimum of 20 hopping frequencies?


The EggFinder is not FHSS. If it were it would fit under item 56 in Schedule 1 of the LIPD, assuming it used more that 20 frequencies.

As stated, it fits in item 58 of Schedule 1. Does not need to hop. Refer to my earlier post for results. There is a link to the relevant legislation you can read there.
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