X10 Community Forum
🔌General Home Automation => Automating Your House => User Modified Devices => Topic started by: dbemowsk on February 02, 2010, 03:19:55 AM
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I have read some posts here about antenna mods to extend the range of the CM15A. The ones I looked at used 1/4 wavelength as their antenna length which is 9.058 inches. A 1/2 wavelength antenna arial would be 18.116 inches at 310MHz which would make a 3/4 wavelength 27.174 inches and a full wavelength 36.232 inches. I do realize that it would make the antenna a bit larger, but would you get a more useful increase in gain using a 1/2, 3/4, or even a full wavelength antenna?
Also, I am thinking of extending my antenna quite a distance from the CM15A. What type of cable would be better for the run, 50 ohm or 75 ohm? I have a fair amount of 50 ohm that I could throw some BNC connectors onto and use, but I also have access to some quad shield RG6U 75 ohm that I can crimp some F connectors onto if that will work better.
The next question is, do I extend both the internal and external antennas of the CM15A?
I thought of first trying a full wavelength of wire coming out of the unit as an initial test to see what that might get me since that will be easy. If that doesn't get me what I want, I may take one of the approaches above and build a nice antenna.
Dan B.
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The Gray internal antenna is the transmit boards antenna and I would leave it alone.
I believe the original modification on AccessHA said the PC Board was a ground plane and their F connector mod brought out the boards ground and the center wire to an F connector. Some used a BNC as a substitute.
The early CM15A had the extra receiver antenna wire balled up in a large random bundle [I have a few of them]. The later ones have the extra receiver antenna wire glued around the case. So technically the antenna from the factory is longer but X10 glued it inside the case ::)
I just took one of the early ones of mine apart. There was about 4.5" of antenna wire balled up in a random bundle between the plastic antenna base and the RF Receiver Boards Antenna connection. That almost doubled the total lenght of the wire from the board to the antenna tip.
Do you have the CM15A schematics? They are available on the FCC Grantee web site.
https://fjallfoss.fcc.gov/oetcf/eas/reports/ViewExhibitReport.cfm?mode=Exhibits&RequestTimeout=500&calledFromFrame=N&application_id=476706&fcc_id='B4SCM15A'
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Hi Brian,
Please forgive the stupid question about the ground wire ...
I've seen the pictures about the F connector mod. It shows that the ground wire goes to one of the ANT holes on the board shown here: http://www.shed.com/tutor/CM15mods/CM15%20mods-Pages/Image9.html
Looking at the photo of the underside of the board at the webpage below, the ANT holes appear to be soldered closed.
https://fjallfoss.fcc.gov/prod/oet/forms/blobs/retrieve.cgi?attachment_id=347602&native_or_pdf=pdf
So, since the ANT holes appear to be blocked from the underside, is the ground wire in the mod simply pushed in and "hanging" there? It doesn't appear to be soldered. Perhaps glued in place?
Would appreciate your help.
Thanks,
eagle
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It's been awhile since I did one of these, but don't you just heat up the hole (with the iron) and shove the wire in place to solder? Glue is not the answer, I wouldn't think.
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Thanks Jmac.
I actually found the answer.
It's on the archived page for accessX10. It says to solder it. :)
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http://web.archive.org/web/20050420014752/http://www.accessx10.com/howto_fconnector_page3.html
Insert the black wire into the VSS hole and turn the PCB over. You should now be viewing the green side of the circuit board.
CAUTION: Only add a small amount of solder to the ground wire and the PCB, just enough to secure the wire to the PCB. Be extremely careful when making this connection to ensure solder doesn’t get anywhere else on the PCB. Tug lightly on the black ground wire to ensure a solid connection. I went one step further by adding a little hot glue around the top side of the black wire for added safety.
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r,
eagle
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I believe the original CM15A was designed to have a different RF daughter card and the silk screen is confusing.
The white wire on the receiver daughter card is the Antenna and VSS is the common. The pad you are showing may actually be a VSS pad originally for the daughter card and the ANT hole may have been the original Receivers Antenna connection.
In the original AccessHA project. The VSS hole slightly closer to the edge was used and not the one with solder flow over it.
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You're absolutely right Brian.
I looked at the pictures of the two boards closer and they are different indeed.
Thanks.
r,
eagle
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The author in the Shed Article. Said they chose the ANT pad to isolate the whole system. Since the power transformer in the CM15A isolates most of the board from AC. Not sure if that was needed.
http://www.shed.com/tutor/CM15mods/CM15%20mods-Pages/Image2.html
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I have read some posts here about antenna mods to extend the range of the CM15A. The ones I looked at used 1/4 wavelength as their antenna length which is 9.058 inches. A 1/2 wavelength antenna arial would be 18.116 inches at 310MHz which would make a 3/4 wavelength 27.174 inches and a full wavelength 36.232 inches. I do realize that it would make the antenna a bit larger, but would you get a more useful increase in gain using a 1/2, 3/4, or even a full wavelength antenna?
Dan,
FWIW
Good RF transmission on a 1/4 wave relies on a ground plane at least the equivalent of the radiating element. Rule of thumb is:the more GP the better. However 1/2 wave does not rely on GP like the 1/4 wave.
When I did my CM15A mod I compared a 1/4 wave with ground plane to a 1/2 wave with no ground plane ( for the 1/2 wave I just stripped and cut 18 inch of coax shield away from RG6, leaving 18 inch of center conductor which I tied to the roof beam in the attic). Using a highly scientific and empirical method of judging effective reception distance ("uh, how many steps can I get from house before my Palm Pad don't turn front porch light no more") I found the 1/2 wave to have slightly better results. I never tried a 3/4 wave as the 1/2 wave satisfied my needs. Some RF guru out there correct me if I am wrong, but I thought a full wave antenna was lossy due to phase cancellation on the element(?). I know I am talking transmit, but receive should work the same.
As far as 50 ohm and BNC vs 75 ohm and F connector, with out knowing what the receiver input impedance is, it is a coin flip. I know Brian H has ferreted all sort of FCC information on the CM15A and the receiver board so he might be able to shed some light, but the general design of antenna and receiver board tells me it ain't that critical. I went for ultimate cheap, resulting in F connector and RG6, and with the wind to my back, standing on one foot and wildly waving the Palm Pad, I can get about 100 feet range
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First I have to say. X10 makes changes and doesn't give any details on what they did. My extra antenna wire found in the older date codes starting with 04 are long and wrapped in a random ball of wire. A date code with a 08 seems to have a shorter wire gently looped. I think I have some in between 04 and 08 that where long but hot glued to the case. Also the newer RF receiver board looks like it has different parts on it and the adjustable coil is now a preset one that looks like they bend to tune then glue in place.
Receiver schematic isn't too clear on its input impedance and my math is rusty.
The schematic says the antenna is 240 mm [9.45"]. Stretching the internal random ball of excess antenna with the plastic parts length. Does measure about 9.45" by my ruler. Also the receiver schematic shows R4 [from antenna to common] has a * next to it. Yes folks a * is a component deemed not needed and is missing.
A WGL V572A antenna is about 9.5" long on a chassis mount F connector. It mounts on a 2 7/8" X 2 7/8" L bracket and the shell of the antenna F connector is connected to the bracket. The cable is RG6 with a male F connector on each end.
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Here are photos of the CM15A mod that I used.
Found the photos but not the guide.
Maybe someone could add the instructions ?
Sorry ! I have to post 3 times so that the photos will load.
Here is photo 1
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Antenna mod photo 2
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Antenna mod photo 3
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As far as 50 ohm and BNC vs 75 ohm and F connector, with out knowing what the receiver input impedance is, it is a coin flip.
Re: Project To Increase Range Of CM15A (http://forums.x10.com/index.php?topic=9470.msg63912#msg63912)
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As far as 50 ohm and BNC vs 75 ohm and F connector, with out knowing what the receiver input impedance is, it is a coin flip.
Re: Project To Increase Range Of CM15A (http://forums.x10.com/index.php?topic=9470.msg63912#msg63912)
Forgot about that Puck, thanks!
I wonder if BNCs and RG58 would have a significant difference compared to "F" connectors and RG6 (other than cost).
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Is there a way to totally disable/disconnect the RF? I've tried setting the Transceived Housecodes to "None", but they're still being received from my Palm (and other) Remotes.
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Is there a way to totally disable/disconnect the RF? I've tried setting the Transceived Housecodes to "None", but they're still being received from my Palm (and other) Remotes.
That is normal operation. Even if no House Codes are tranceived, any RF commands are received for macro use and for logging. So no, not with out hacking the CM15A (i.e. disconnect the antenna wire from the receiver board in the CM15A).
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The receiver boards IC has a disable pin on it. It has to be pulled high if memory serves me.
There is no easy extra pad to the outside world on the receiver daughter card for the disable signal.
I will look and see if I can find my notes. I did test the disable function on one of my CM15A units and it stopped all RF reception.
OK I disabled the whole Receiver by pulling the Disable Pin High with a resistor.
One BIG point. The schematics on the FCC web site are 100% wrong for my Date Code 08B09 and 04J41 Receiver boards. Mine do not use the 20 pin RX3310A Chip. It has the 18 pin RX3310A that has a different pin out for the signals. Pin 9 is still disable but others are different. There is a small feed through hole for pin 9 so maybe a resistor could be hung on it and VCC to disable the receiver completely.
I kind of fuzzy memory remember someone cutting the received signal output or the five volt power from the daughter card to the main board.
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I kind of fuzzy memory remember someone cutting the received signal output or the five volt power from the daughter card to the main board.
I cut the +5V line and ran it to a toggle switch that I mounted to the bottom of the CM15A. This has worked well for me for disabling all RF input so that only my V572RF32 is receiving signals. The switch allows me to reactivate it for tests.
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I did try doing a full wavelength wire antenna to the antenna pad on the daughter card. In my test, this did not improve the signal at all. If anything, it degraded it a bit. I then went with the old reliable and did the F connector mod. I then made an antenna with a PL-258 chassis mount jack and 5 pieces of 14 gauge electrical wire cut to slightly over 9 inches. One as an aerial and the other 4 as the ground plane. That worked great. I will be trying a slight mod on the antenna changing the wires to just over 18 inches which is 1/2 wavelength to see if I get any improvement. I will post my findings.
Dan
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When you did the F connector. Did you use the VSS or Ant pad holes on the main PCB for the F connectors shell? I used VSS as in the AccessHA forums mod. In the Shed mod they used the ANT holes on the main PCB.
I did add a switch to my sacrifice CM15A to turn the whole RF receiver on and off. I choice to get brave and solder a resistor to a switch's common to the RF Receivers Disable Pad and then one leg to +5 the other to VSS. When the +5 is on the disable pad. NO RF signals are showing in the Activity Monitor. VSS on the pad and the RF Receiver again functions.
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Can someone answer me a question i hope. I have done the modification with the f-connector, have tried the "ant" hole and the "vss" hole.
My question is this- Both the location for the mounting seem to be isolated from the total circuit, the circuit traces are not connected to either hole ( vss, ant). I dont really understand all the principals of antennas, but i'm asking if the ground wire of the f-connector is even needed, and what purpose it has.
All it seems like i am doing is adding a 2inch piece of wire to the ground and sticking it in a hole that leads nowhere.
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Unless the new ones are different. VSS goes to the boards common and would be the better choice for the shell of the 'F' connector.
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the new ones must be different because it is isolated and doesnt go anywhere. I did however actually mae the wire long enough and cleared away some of the green coating on the traces so i could get it to connect to the common. Figured that is where it was supposed to go anyway.
So thank you for the answer.
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By chance does yours have any surface mounted ICs on it?
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Found some mods similar, but this one will not void your warranty. Maybe get rid of that clothes hanger...
What you need:
Radio shack part number: 270-1405 $5.29
Dremel or something to cut antenna.
Few kind words
First cut the bottom off the Radio Shack antenna with the dremel.
Remove the bottom section of the Radio Shack antenna.
Remove the top button off the CM15A antenna by pulling. Be careful and not pull the the whole antenna off of the CM15A.
Slide the Radio Shack antenna over the plastic antenna on the CM15A
Snap antenna into side holder.
May work further, test good from 60 feet and through one wall.
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Nice mod. Helpful from me
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Simple and elegant. #:)
What would really be interesting would be to try the RadioShack antenna after making Rabbit's mod http://forums.x10.com/index.php?topic=21000.0 with before/after range measurements.
If you need even more range see http://forums.x10.com/index.php?topic=25397.msg142651#new.