razberry range problems

Discussions about RaZberry - Z-Wave board for Raspberry computer
jvandenbroek
Posts: 1
Joined: 05 May 2015 18:16

Re: razberry range problems

Post by jvandenbroek » 05 May 2015 18:33

@krambriw I think that's correct, you should place the antenna at the other side of the cap or (what I did) just remove it to disconnect the PCB antenna. It's a very small cap which probably does some noise filtering, but so far it has been working great with just a straight wire.

vvuu
Posts: 39
Joined: 30 Aug 2015 14:22

Re: razberry range problems

Post by vvuu » 11 Sep 2015 00:25

what kind of cable did you use ?
and it has to be exactly 86mm lenght ?

after years - how it works now? still ok ?

petergebruers
Posts: 231
Joined: 26 Jul 2015 17:29

Re: razberry range problems

Post by petergebruers » 11 Sep 2015 11:20

I did roughly the same thing. I used 15 cm of shielded wire (used for audio... you could use a small coax but I think it doesn't matter at that short length), and at the end about 8,5 cm of ordinary wire. It has at least doubled the range, but I think it's even closer to three times. I get almost the reach of my Fibaro HC2. Maybe a RG174 coax would be better, I have't tested it. The contacts are so small I preferred not to experiment too much... I also used hot melt glue to cover the cable and the contacts. If you don't do that, one pull at the cable and it's "game over"...

vvuu
Posts: 39
Joined: 30 Aug 2015 14:22

Re: razberry range problems

Post by vvuu » 11 Sep 2015 14:06

but after 15cm shielded cable You added 8,5cm wire - it has to be exactly 8,5cm ??

and length of this 15cm cable it doesn't matter because it is shielded ?? only I have to be careful with 8,5cm wire (antenna) ????

Maybe I could use antenna like this:
http://p.globalsources.com/IMAGES/PDT/B ... ntenna.jpg
from home AP 2.4GHz.. ?

petergebruers
Posts: 231
Joined: 26 Jul 2015 17:29

Re: razberry range problems

Post by petergebruers » 11 Sep 2015 14:40

Here are a few thoughts...

- If you are afraid to ruin it, then don't do it. You have to be prepared to ruin it.
- the 8,5 cm wire is the antenna. Just like the wires coming out the housing of a Fibaro relay. You can start by making it a bit longer then measure range and bend it until it seems optimal. I've done only minor adjustment, because it's rather time consuming.
- I think it works because you get the antenna away from noisy digital parts of the Raspberry. That's just a theory, I have no equipment to prove that.
- What do you mean by "you have to be careful"? All wires should be isolated. There should be no part of a blank wire visible. I use bits of heat shrink tubing.
- Z-Wave is 868,4 MHz in Europe, so a 2,4 GHz antenna is not the right thing. But antenna design is part mathematics and part plumbing, so feel free to try. With a high power (> several Watt) transmitter, you might end up destroying it. This is low power, but of course also miniaturized. A HF engineer once told me not to run a Z-Wave transmitter without antenna. He was afraid it might blow. I tried, and it didn't. But, like I said... be prepared to ruin it.

If there's anything you need to ask, please go ahead.

vvuu
Posts: 39
Joined: 30 Aug 2015 14:22

Re: razberry range problems

Post by vvuu » 11 Sep 2015 16:29

thanks for fast reply
tell me what with ground ? cause shield is the ground ?

for example I could take pigtail with SMA from home router/ap and make antenna SMA interface for SMA connector with 85mm wire ;)

but the pigtail has signal cable in the middle and ground/shield.. where did you connect it ?

petergebruers
Posts: 231
Joined: 26 Jul 2015 17:29

Re: razberry range problems

Post by petergebruers » 11 Sep 2015 19:12

If you look at the Razberry, you'll see the internal antenna attached to a capacitor (small block). The other side of the capacitor goes to some circuit (the radio) and a solder pad (tinned). That pad connects to the centre wire of your coax. Next to that pad, you'll see another, identical one. That one connects to the (common) ground (if in doubt, please measure it). So that one is for the shield of the coax. Please remove the capacitor, by desoldering it carefully, so the internal antenna no longer connects to the radio.

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