Transmit power and range

[Admin]

There have been testing reports of only achieving 1-2 mile range over the 868mhz frequency.
during early trials I was achieving max 25km range, so decided to investigate

I compared my original prototypes versus the latest prototypes, and modified the software to run RSSI checks, this allows the receiver to indicate the signal strength in dBm.

Comparing my old prototypes to the new, I was seeing a difference of 8dBm, that is significant!
The main difference was the use of an end launch SMA on the original, and pigtail on the latest.

As an experiment I soldered an SMA onto one of my newer prototypes, and the power loss was recovered.

I need to get back in the air with the modified prototypes to see what range I now see.
I have modded 6 protos so that is a good selection to try out.

So this may be the cause of the shorter transmit range.

It would appear at first glance that the pigtails are quite lossy
Thx
Lee

[Bill Maxwell]

I guess the loss depends on the quality of the mini coax cable used to make the pigtail. All coax must have some loss, in theory but I have found profound differences at some frequencies between cables that look identical. Unfortunately, the losses tend to intensify as we go up in frequency and I would expect 868 MHz to be verging on the critical zone.

Bill
Jodel D18, 19-4446, X-Air Std 19-3229
VK7MX

[brinzlee]

So on the prototype you had the aerial soldered directly to the ARF board....or via an SMA connector on the board.

[Admin]

So on the prototype you had the aerial soldered directly to the ARF board....or via an SMA connector on the board.

Hi
With the v1.0 ARF, I had an end launch SMA, soldered onto the board.
I have now done the same with the ARF 2.0, and this has made the RSSI numbers much better.
Incidentally, one of the pigtails had worked loose on one of my PAW, so in retrospect I think the SMA is a much more robust solution.

I will post some pictures later
Thx
Lee

[brinzlee]

Not all is lost if thats the case...I guess these will solder in place of the pigtail connector......then a redesign of the ARF placement if using a slice or pod

http://www.aliexpress.com/store/product/SMA-Female-Jack-nut-RF-Coax-Connector-end-launch-PCB-Cable-Straight-Goldplated-NEW-wholesale/1861251_32329691707.html

[ianfallon]

Pics would be good - am not sure what you mean by SMA or what to do - been using the stock aerials etc. so far.

[brinzlee]

The link in the one I posted above is the connector which solders onto the end of the ARF where the pigtail connector currently is....this then plugs into the supplied antennae from the Ciesco....just means mouthing it so the end is in the plastic case.....so removing the pigtail wire connector completely

[trapdoor]

I really don't much like the u.LF connectors that they use on the ARF as they have a very limited reconnection life and are really only useable with things like laptop wifi cards. The one on my original ARF will fall of just by looking at it though the pigtail with the last one I bought was better.

My concern with end-fed SMA is the lack of room in the small RPi case to use it successfully. Need to fit one and try it out as it may require a mechanical redesign as I wouldn't want the ARF supported purely off the SMA, knowing the standard of some soldering!

[Wadoadi]

Would be good to get comment from Wireless Things re this as it should be "fit for Purpose" which if it is attenuating the single that much it is not!

[Admin]

Not all is lost if thats the case...I guess these will solder in place of the pigtail connector......then a redesign of the ARF placement if using a slice or pod

http://www.aliexpress.com/store/product/SMA-Female-Jack-nut-RF-Coax-Connector-end-launch-PCB-Cable-Straight-Goldplated-NEW-wholesale/1861251_32329691707.html

Hi
I used these
http://www.ebay.co.uk/itm/1-and-5pcs-SMA-female-jack-Panel-Mount-PCB-Solder-Connector-UK-SELLER-/271714107398?var=&hash=item3f436c4006
yours look better because I had to snip 2 legs off the connector

Thx
Lee

[Admin]

Would be good to get comment from Wireless Things re this as it should be "fit for Purpose" which if it is attenuating the single that much it is not!

Antenna design & setup is a black art, this guide does exist
http://openmicros.org/index.php/articles/84-xrf-basics/289

[brinzlee]

I've just ordered 20.....I'll let you know how it all works
Hopefully the mechanical strength coming from the fixing to the case....the dimension should allow it to sit on the underside of the slice of pod with a bit of jiggery pokery !!

[Admin]

I've just ordered 20

Sounds like you may get a few requests to help relieve you of the additional 19 

[Admin]

As promised here are a couple of images

The original ARF1.0, and the ARF2.0

[stephenmelody]

Excuse my blatant ignorance, but is the advice to lose the little tail and solder direct? I'll have a go with my groundstation that I'm building if that's the plan..