Transmit power and range

[The Westmorland Flyer]

Yes, the ARF in PAW is using the "high power" (sic) bit of the band. What we need and what we can get are unfortunately likely to be poles apart once metalwork gets in the way. The problem with bolting on amps (transmitter or receiver) is the need for T/R switching so that both can use the single antenna. All is possible, of course but the technology isn't commonplace (i.e. cheap). The ARF already has a PA-cum-RF amplifier that includes the T/R switching fabric. (Edit - I see that Jerry has covered some of these points whilst I was doing my one fingered typist trick.)

I'm working up to an experiment. I shall place PAW #1 in the visual control room at my local airfield, then trundle off with PAW #2. In the aircraft I shall have a) the standard whip antenna lurking on the coaming, b) a dipole taped to the canopy, and c) a quarter wave ground plane antenna protruding through a convenient hole in the underside of my aircraft's all metal fuselage (don't ask...!). I'll then do some tests, flying from and to the airfield with the different antenna configurations. All I need is for it to stop raining... should be an interesting test.

[stephenmelody]

I did some highly scientific testing tonight... 

Tests
10ft apart
No aerials on either -                   IS 77          IM 70
1 stubby aerial horizontal –         IS 88          IM 57
2 stubby aerials horizontal –       IS 69          IM 41
2 stubby aerials 1 hoz 1 vert –    IS 65          IM 35
2 stubby aerials vertical –            IS 52          IM 23
1 stubby, 1 long both vertical –  IS 46          IM 23
2 stubby vertical + adptr -          IS 75          IM 47

I couldn't get two long aerials to work... not sure why, but does this mean that 2 right angle adapters (in my last example) would be pretty poor? Seems to be worse that 2 stubby aerials horizontally.

[The Westmorland Flyer]

Interesting test. If the antennas are cross-polarised (e.g. one horizontal, one vertical) then with everything else equal you will see a marked reduction in range. It doesn't greatly matter whether the antennas are horizontal or vertical but they both need to be the same. Usually vertical is preferred because that gives a 360 degree horizontal radiation pattern.

What is the "long" antenna? How long is it and is it just an end-fed whip or perhaps a dipole or something else? Perhaps you could post a picture. Longer isn't necessarily better - resonance is the name of the game. The adaptors shouldn't make any difference.

[stephenmelody]

Long: https://www.wirelessthings.net/868-915-mhz-rubber-duck-antenna

Short: https://www.wirelessthings.net/868-915-mhz-small-rubber-duck-antenna

Adapter: http://r.ebay.com/HPKFIv

I was surprised the adapter made a difference... I also think I've buggered one of my ARFs as it doesn't seem to be responding now...

[Admin]

I did some highly scientific testing tonight... 

Tests
10ft apart
No aerials on either -                   IS 77          IM 70
1 stubby aerial horizontal –         IS 88          IM 57
2 stubby aerials horizontal –       IS 69          IM 41
2 stubby aerials 1 hoz 1 vert –    IS 65          IM 35
2 stubby aerials vertical –            IS 52          IM 23
1 stubby, 1 long both vertical –  IS 46          IM 23
2 stubby vertical + adptr -          IS 75          IM 47

I couldn't get two long aerials to work... not sure why, but does this mean that 2 right angle adapters (in my last example) would be pretty poor? Seems to be worse that 2 stubby aerials horizontally.

Hi Stephen,

There is clearly a marked difference in the two units when all should be equal, in particular here
2 stubby aerials horizontal –       IS 69          IM 41
2 stubby aerials vertical –            IS 52          IM 23

just out of interest, I know it is hassle, are you able to unplug your ARF and swap, I would expect the two readings above to be the same for master and slave but they are wildly different!.

I have become so dissatified with the ARF :-(

Thx
Lee

[stephenmelody]

Working on it...

[stephenmelody]

Ah... when i say horizontal, I mean tip to tip, not broadside to broadside.

[The Westmorland Flyer]

Got it. The long one is the standard one supplied with the ARF and it should out-perform the stubby quite noticeably IF you can get it vertical. Both would work considerably better with a ground plane.

It's possible that the 90 deg adapter is U/S but I'd have thought it unlikely. Check that the coaxial centre pin is correctly locating with the centre socket on the adapter. If you have a test meter you might also check for centre pin continuity and that the centre pin is not shorting to the screened casing.

The ARF stops ackling if there isn't a usable GPS signal - that caught me out to begin with. Might that be the problem?

[JCurtis]

I did some highly scientific testing tonight... 

Tests
10ft apart
No aerials on either -                   IS 77          IM 70
1 stubby aerial horizontal –         IS 88          IM 57
2 stubby aerials horizontal –       IS 69          IM 41
2 stubby aerials 1 hoz 1 vert –    IS 65          IM 35
2 stubby aerials vertical –            IS 52          IM 23
1 stubby, 1 long both vertical –  IS 46          IM 23
2 stubby vertical + adptr -          IS 75          IM 47

I couldn't get two long aerials to work... not sure why, but does this mean that 2 right angle adapters (in my last example) would be pretty poor? Seems to be worse that 2 stubby aerials horizontally.

Hi Stephen,

There is clearly a marked difference in the two units when all should be equal, in particular here
2 stubby aerials horizontal –       IS 69          IM 41
2 stubby aerials vertical –            IS 52          IM 23

just out of interest, I know it is hassle, are you able to unplug your ARF and swap, I would expect the two readings above to be the same for master and slave but they are wildly different!.

I have become so dissatified with the ARF :-(

Thx
Lee

As the Master always seems lower than Slave, have you tried to swap Master and Slave settings over and see what the results are?

[stephenmelody]

JCurtis, I think you make the combined board with the thingy soldered onto the board direct with the baro thingy... that one is the master... I'm working on getting one back up and working.

[JCurtis]

I've not used this setting in PAW, are these RSSI values -ve?  In general RSSI numbers are better the closer to 0.  You would be better to have the units further apart when testing, or in different rooms so there is some attenuation between them, 10 feet isn't that far even at the power of the ARF.

[stephenmelody]

Yes negative, I was just making it easier to read...

Starting to lose the will to live with this... I can only get a reading off the long one (that comes standard) if I hold the tip with my fingers.

[Admin]

Jeremy is correct, I made my measurements 30ft apart.
I got numbers if -020 on each

Thx
Lee

[stephenmelody]

Went and put it one in another room, now just getting a dollar sign...

[Admin]

Went and put it one in another room, now just getting a dollar sign...

That sounds like the settings are wrong at one end a $ is the start of a standard p3i serial packet