Author Topic: CC1101/CC110L modules outdoors losing range over time  (Read 347 times)

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Offline JanErik

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CC1101/CC110L modules outdoors losing range over time
« on: December 04, 2017, 09:14:48 PM »
Hello,
New to the forum and have this problem;
I am using this kind of radio modules with an on-board RF stage, activated with a PAC pin;
https://www.aliexpress.com/item/CC1101-CC110L-wireless-module-medium-power-600-800-meters/1576224501.html
http://www.electrodragon.com/product/cc1101-433m-wireless-module-variable-designs/

Using one of them in my cold (corrugated sheet metal) garage to measure temp/humidity/groundtemp and controlling a block heater relay.

After around a year, they start losing range, first one lasted almost two years and now I had one last 1.5 years. Would not contact indoor unit with garage door closed. Replaced module and it works.

Module is in an enclosure but antenna sticking out, sealed as good as possible with Blu-tak and hot glue. For the new node I will 3D print an enclosure that fits both module and antenna, in clear PLA for best RF performance.

I sometimes suspected the SMA antenna connector, cleaned multiple times and sometimes that helped but on this latest module I had the antenna soldered so that is not a cause.

Could it be humidity creeping into caps/resistors and then cracking them in subzero temperature?

Sometimes I suspect the AS169 RF switches that direct the signal to/from RF stage.

Could it be salt depositing on the board? I live 500meters from the Gulf of Bothnia and 200meters from a salted motorway. Tried cleaning the modules with distilled water and propanole to no help.

And to add, it is controlled by an Atmega328, Arduino and PanStamp driver, https://github.com/raimue/arduino/blob/master/libraries/panstamp/cc1101.cpp .

I have a similar module indoors that lasted many years.
Also have a CC110x module without RF stage in my basement storage and that is able to send even if the garage node is acting up so it is not the indoor base station module having problems.
 

Offline Gribo

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #1 on: December 06, 2017, 01:39:06 AM »
Do you have access to the device schematics? What you describe can be attributed to crystals drifting apart. The CC1101 has a minimum RX bandwidth of 58KHz IIRC, so it is quite tolerant to such drift, however, if the design uses 40ppm or worse 26MHz crystal, then such problems occur.
I have used the CC1101 in very harsh environments (Salt, humidity, heat, cold etc) with proper crystals and calibration, the devices ran well for years.
 

Online coppice

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #2 on: December 06, 2017, 01:57:15 AM »
Could it be that the difference between your indoor module that lasts, and your exterior module that doesn't is the temperature of the crystal? If its not a very stable crystal, and had poor ageing characteristics, the additional effects of temperature might be pushing the transmission too far off channel.
 

Offline JanErik

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #3 on: December 07, 2017, 08:35:20 PM »
I have drawn schematics of the RF side but not of the digital. Will draw clean and post.
I tried setting the sending to adjacent "channels" (4 and 6, normally use 5), do not know the BW but receiver did not see them at all.

And I have now tested the modules without enabling the RF stage (PAC pin) and they seem to work fine with range of a non-amplified module.
More and more suspecting the transistor (or RF AS169 switches) actually is burnt. I thought it was a FET, SOT-89, but now I measure a diode (0.5V forward) from what could be emitter and base, and around 1.3V forward from what could be collector to base.
So it could actually be a PNP which is burnt from collector to base.

One issue in my software was that I turned PAC on 50ms before sending ("//let the rf stage stabilize"), and guess it does draw some amount of current (especially with NiMH AA batteries) as the transistor is connected (Vcc -> 0R22(wire-wound) -> drain (collector?) and source (emitter?) -> gnd.
Now I have lowered that to 1ms (0ms would not work) and it still works.

The bias of the transistor gate/base is around 1.3V on one broken module and around 2V on the other, with RF stage enabled.

I have two healthy modules on their way from China so I will investigate the transistor on them.
« Last Edit: December 07, 2017, 08:37:11 PM by JanErik »
 

Offline Gribo

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #4 on: December 08, 2017, 02:14:47 AM »
It is not a transistor, it can be either a power amplifier (Most likely) or an LNA.
50msec is a very long time for it to be active.
 

Offline JanErik

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #5 on: December 08, 2017, 06:30:21 AM »
In SOT-89, three-pin?
 

Offline Gribo

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Offline JanErik

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #7 on: December 10, 2017, 01:31:05 AM »
Alright then, just thinking now as I find nothing from the marking, "H3 2341". Is this some Chinese noname?

Adding some sketches of the RF and bias stage, where the FET may be an amplifier.
 

Offline JanErik

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Re: CC1101/CC110L modules outdoors losing range over time
« Reply #8 on: Yesterday at 06:28:41 PM »
Got the new module now and it also has the same diode test properties of the transistor/amplifier.
 


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