Long Marston Test 17 October

[The Westmorland Flyer]

I can't think of any way in which a TV tuner (PC based? Stand-alone TV?) or indeed any other receive-only kit could interfere with the ARF's operation.

[stephenmelody]

I mean the one used for picking up ads-b in the PAW system. Sorry, that wasn't too clear.

If I knew what this meant: aSSRSSIS-58 aMMRSSIM-54 it would help, I seem to get higher values without the dvb-t plugged in that when it is in...

I'll do further testing tomorrow with my two units in slave/master config to compare the outputs with and without the dvb-t tuner plugged in.

[Ian Melville]

2.4GHz is absorbed by water-based things such as foliage and people significantly more than is 800MHz, so I am not particularly surprised...

Thank you TWF, I was forgetting that they are quite different frequencies.

[The Westmorland Flyer]

I seem to get higher values without the dvb-t plugged in that when it is in...

That sounds like it might be a power supply problem. The DVB dongle is quite a greedy beast, which is why it gets so hot.

[Paul_Sengupta]

Just as a complete amateur, this may be a stupid question, but would the tv tuner interfere with the ARF at all?

It's been requested for the next set of tests that the DVB be removed for air-air testing to see if it makes a difference.

[Richard W]

If I knew what this meant: aSSRSSIS-58 aMMRSSIM-54 it would help

The -58 and -54 are the received signal strength at the slave and master respectively (I think that's the right way round). I believe that the figures should be in the low -twenties, for stations 30m apart, but  I could be mistaken.  Presumably your stations were separated by building structure at -58 db(i?) ?

[Richard W]

I seem to get higher values without the dvb-t plugged in that when it is in...

That sounds like it might be a power supply problem. The DVB dongle is quite a greedy beast, which is why it gets so hot.

The ARF is powered by the 3.3v regulator, which has a fair bit of headroom, so supply problems shouldn't be an issue.  I have never seen the 3.3v supply at anything less than 3.25

[stephenmelody]

If I knew what this meant: aSSRSSIS-58 aMMRSSIM-54 it would help

The -58 and -54 are the received signal strength at the slave and master respectively (I think that's the right way round). I believe that the figures should be in the low -twenties, for stations 30m apart, but  I could be mistaken.  Presumably your stations were separated by building structure at -58 db(i?) ?

So lower is better? They're separated by 1 floor in my house. I'll do some more testing then...

power supply isn't an issue, I'm using more than the recommended kit. 1x 4.2amp wall power supply with .5m juicybitz cable, the other is on a 2.4amp battery pack with the same cable.

[Richard W]

To avoid misunderstanding, more positive numbers are better.  So -20 is better than -58.  Lee, please could we have some advice as to which way round the master/slave figures are, and what to expect at a given distance, say 30 foot?

[Admin]

To avoid misunderstanding, more positive numbers are better.  So -20 is better than -58.  Lee, please could we have some advice as to which way round the master/slave figures are, and what to expect at a given distance, say 30 foot?

There is a description here ...
http://openmicros.org/index.php/articles/84-xrf-basics/146-rssimode

[Richard W]

That is very helpful, thanks.  Do the max range figures of 88 to 92 apply to the ARF? ISTR seeing that the ARF has a more sensitive RX than the XRF

[Admin]

my understanding is that once the figures get down to -90, the link becomes unreliable

[Bill Maxwell]

I seem to get higher values without the dvb-t plugged in that when it is in...

That sounds like it might be a power supply problem. The DVB dongle is quite a greedy beast, which is why it gets so hot.

The ARF is powered by the 3.3v regulator, which has a fair bit of headroom, so supply problems shouldn't be an issue.  I have never seen the 3.3v supply at anything less than 3.25

It won't be a question of voltage headroom but the ability to supply all the current your entire set-up requires.

[Richard W]

It won't be a question of voltage headroom but the ability to supply all the current your entire set-up requires.

If the current supply is insufficient the supply voltage will necessarily drop, or crowbar off entirely.  A 3.3v regulator will typically function until the supply voltage has dropped to 4.3v, but the Pi can be expected to fail before that, when the supply reaches the specified minimum of 4.75v.