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Author Topic: Increase RF signal DS12As antenna modification  (Read 8749 times)

javiert30

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Increase RF signal DS12As antenna modification
« on: January 23, 2013, 05:22:45 AM »

I had low RF signal with all my DS12A sensors, none of them wanted to be recognized with AHP, so I made this modification and no more problems. AHP recognized them once I sink them. Here I leave you some pictures.

1.Wire (Used coaxial cable)




2.Here is the point to solder the antenna wire. Don't use the other point were the trace starts, the idea is to solder it in here to add like  half inch to the antenna plus the one that you are installing.




3.Bent wire so it can reach the antenna solder point inside and insert it from here.




4. Solder the antenna wire here.




5.Here is how it look from outside once installed.




6.Because I'm using the hole where you screw the sensor to the wall, I decided to use double side tape, yes I know if you use regular double side tape is going to fall with the time, this is not regular double side tape, you can find this tape in H....pot. I took a picture so you can see how it is called. I worked installing communication equipment for NAVY ships and this tape is what they use, this thing is strong, believe me.



*** After this modification all my DS12A sensors have been recognized with AHP with no problem.***    >!
« Last Edit: January 23, 2013, 05:25:03 AM by javiert30 »
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Brian H

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Re: Increase RF signal DS12As antenna modification
« Reply #1 on: January 23, 2013, 06:00:33 AM »

Easy project.
Thanks for sharing.
Helpful Post from me.
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dhouston

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Re: Increase RF signal DS12As antenna modification
« Reply #2 on: January 23, 2013, 07:58:23 AM »

I suggest caution. Adding solder to a PCB trace antenna can detune the transmitter (by changing the inductance) making it unable to communicate with the receiver.
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pseeker

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Re: Increase RF signal DS12As antenna modification
« Reply #3 on: January 23, 2013, 02:00:08 PM »

THanks, helpful.   I bought a three DS12As (since it uses a 310Mhz SAW) to do this exact thing and replace a few pesky DS10A  out range from my SC1200.  Some day I'll get to this project.
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dhouston

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Re: Increase RF signal DS12As antenna modification
« Reply #4 on: January 23, 2013, 02:33:27 PM »

Ahh! I wasn't aware or had forgotten that the DS12A uses a SAW resonator. This mod is likely to be safe in that case. I know from experience that it is not safe with the DS10A.
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Brian H

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Re: Increase RF signal DS12As antenna modification
« Reply #5 on: January 23, 2013, 02:47:02 PM »

I guess you could possibly detune the PCB Antenna.
The schematic is in the FCC Database.
They used the X10 for Radio Shack OEM Door Window Sensor as except for the case is the same as the DS12A
Grantee:B4S
Product Code:-DS11
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ronski1

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Re: Increase RF signal DS12As antenna modification
« Reply #6 on: February 16, 2013, 11:03:15 AM »

Does this wire have to be routed to the outside of the case? Could it just be bent so as it stays hidden inside the case, maybe in an upside down "U" shape?  Besides being able to fit in the case, does length matter? Longer?
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woodyl

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Re: Increase RF signal DS12As antenna modification
« Reply #7 on: July 15, 2015, 02:23:25 PM »

 I saw this old thread on modifying the DS12A antenna and decided to try it.  I added a DS12A to my mailbox, which was out of range.  The antenna mod seemed to do the trick.  Later, I had to replace the external switch and when I put the box back in place, it seems that the range had decreased and it was no longer working at that distance.

Has anybody else tried this mod?  Does anybody have any idea what the ideal antenna length would be?
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Brian H

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Re: Increase RF signal DS12As antenna modification
« Reply #8 on: July 15, 2015, 04:39:25 PM »

Is the DS12A; including the added antenna stub, inside a metal mail box?
If it is inside a metal mail box. The RF signal is being blocked by the metal.
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woodyl

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Re: Increase RF signal DS12As antenna modification
« Reply #9 on: July 15, 2015, 05:54:56 PM »

No, it's attached to the bottom of a plastic mailbox.  The thing is, that this thing was communicating regularly with my CM19a via a homemade ground plane antenna for a week or tw0.  I removed the mailbox and the DS12A to fix a problem with a bad connection with an external door switch.  After I put it back, it was no longer communicating with the CM19a when it was out in front of the house.

If I bring the whole contraption inside, it works ok.  I checked the connection where the antenna wire was soldered to the PCB and it looks fine.  Something seems to have happened after I moved it around that stopped it from getting the range it was originally getting.  I can't figure out what was different.
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Brian H

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Re: Increase RF signal DS12As antenna modification
« Reply #10 on: July 16, 2015, 03:45:54 PM »

You did the mod as shown in the photos?
I would double check it didn't pull free from the 'ANT' pad and that it is not touching any other PCB runs.

I took one out of its case and compared it to the FCC Database schematic. The 'ANT' pad is the primary side of a RF coupling loop to the isolated antenna loop on the back of the PCB.
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dhouston

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Re: Increase RF signal DS12As antenna modification
« Reply #11 on: July 16, 2015, 05:32:03 PM »

This, aside from FCC rules prohibiting such mods, is why I usually suggest this approach http://davehouston.org/X10_feng_shui.htm which usually works well without the need to open the enclosure.
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woodyl

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Re: Increase RF signal DS12As antenna modification
« Reply #12 on: July 16, 2015, 06:25:16 PM »

This, aside from FCC rules prohibiting such mods, is why I usually suggest this approach http://davehouston.org/X10_feng_shui.htm which usually works well without the need to open the enclosure.

Dave: I saw your "Feng Shui" method and tried that before I did the mod.  It didn't do the job for me.  I'm guessing that the gain using the external radiator is not as high as when lengthening the antenna.  BTW, unlike the antenna in the OP, I used a 9" length of small gauge insulated wire.  This is the 1/4 wave length of 310Mhz device.  I assume that that will work better than the shorter antenna shown in the OP.

You did the mod as shown in the photos?
I would double check it didn't pull free from the 'ANT' pad and that it is not touching any other PCB runs.

I took one out of its case and compared it to the FCC Database schematic. The 'ANT' pad is the primary side of a RF coupling loop to the isolated antenna loop on the back of the PCB.
Brian:
Yes, I did the mod exactly as shown in the photo. and it made a dramatic difference when I first tried it.  After I started having problems, I checked the solder join again and it looked good.  I do remember that I dropped the whole business once, while I was working on it, that is the mailbox with the DS12A attached to it.  It's possible that the fall did something to the sensor, but I can't see anything.  I guess I'll put an antenna on a new sensor and see if that one will work.
« Last Edit: July 16, 2015, 06:34:51 PM by woodyl »
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dhouston

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Re: Increase RF signal DS12As antenna modification
« Reply #13 on: July 16, 2015, 06:46:09 PM »

Dave: I saw your "Feng Shui" method and tried that before I did the mod.  It didn't do the job for me.  I'm guessing that the gain using the external radiator is not as high as when lengthening the antenna.  BTW, unlike the antenna in the OP, I used a 9" length of small gauge insulated wire.  This is the 1/4 wave length of 310Mhz device.  I assume that that will work better than the shorter antenna shown in the OP.

OK. An engineer acquaintance measured a 10dB increase and my own RSSI measurements showed large gains but, there are a lot of variables. Another engineer speculated that the feng shui method worked because of a lousy X10 design. It may well be that newer modules (e.g. those with SAW resonators) may not work so well.
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woodyl

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Re: Increase RF signal DS12As antenna modification
« Reply #14 on: July 16, 2015, 06:46:41 PM »

BTW, here's an interesting thing.  My application logs all of the communications from each of my sensors, motion detectors etc.  I can look at the log and see if a particular DS12A is transmitting its alerts and keep-alives (which it should do about once an hour).  The CM19A is only able to read the transmission from the sensor on the mailbox very sporadically because of the distance issue, maybe once a day or so.  However, when the mail truck pulls up close to the mailbox and the letter carrier opens the door to the rural-type mailbox, very often I get a successful alert transmission.  I'm assuming this is because the large metal body of the mail truck reflects the signal back toward the antenna attached to the CM19A.  The sensor is right at the edge of the distance limit, so that little bit of assistance is enough to make it work.
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