[How-to] Build an Antenna for Your X-10 Receiver


How to Make a One-Quarter Wave Ground Plane Antenna
by BraveSirRobbin

A typical X-10 310 Megahertz receiver such as the MR26a's reception can greatly be improved with a custom antenna rather than the stock pig-tail wire. This how-to will show you how to make a one-quarter wave ground plane antenna tailored for the MR26a's frequency of 310 Megahertz.

First step is to modify your MR26a or other receiver so it can accept an external coax connection. This is performed by installing a bulkhead "F" or other connector (such as "BNC") on the end of the pigtail connection. An elaborate tutorial is already in place for this task at this location (scroll down to the "Modify the MR26" line).

If you have another type of receiver you will need to modify it so it can accept an F or other means for connecting a coax cable to it.

To make this antenna you will need the following items (some are shown below):


Chassis Mount UHF SO-239 Coax Connector (Radio Shack item # 278-201)
F to SO-239 Adapter (Radio Shack item #278-258C)
1/16" thick Brass Rod (approximately five feet length)
#4 Ring Crimp Lugs
4-40 Screws, lock washer, and nuts (four sets)
Solder Iron and Solder
Hacksaw (What would be a HA project without one of these)


We will need to calculate the one-quarter wavelength for 310 megahertz. The formula WAVELENGTH EQUALLS THE SPEED OF LIGHT DIVIDED BY THE FREQUENCY is used to calculate the total Wavelength, this will then be divided by four to determine the "one-quarter' wavelength.
Speed of Light = 1.180 E10 inches/sec
Wavelength = 310 E6 hertz
So plugging these numbers into the above formula yields:
Wavelength = 1.180 E10 / 310 E6, which equals an overal wavelength of 38.07 inches. We must then divide this number by four to obtain the one quarter wavelength distance (38.07 / 4) of 9.5 inches.

Assembling the Antenna:

First take the brass rods and cut to five each 9.5 inch lengths. Sand one end (this will be the solder end).


Solder one rod into the center of the chassis mount connector as shown.


Then insert one end of the brass rod into the #4 ring crimp lug and solder in place as shown:


Do this for FOUR of the rods (one end only).

Attach the assembled crimp lug/rods to the chassis connector's holes using the 4-40 hardware. Insure a secure/tight fit onto the connector. Bend the lug/rods to a 45 degree angle "away" from the center top rod as shown.


Repeat this assembly for the other three rods.

The antenna is now ready for mounting. Mount "upside down" in a location such as an attic and insure the coax cable does not go "thru" the antenna as shown.


Use a coax cable such as RG6/U and F connectors, connect to the MR26a. I'm running approximately 50 feet of coax between my MR26a and antenna with no problems (in my new home, picture above was in my old home. Also note I said NOT to run the coax through the antenna, i.e not the way the above photo shows).

Test out your new increase coverage.

Well, thats it. You just completed this project that increased your x-10 receiver coverage for less than ten bucks in parts.
Can anyone tell me if this design will work in "Transmitting" as well as Receiving? I want to improve my CM19a range. Do the multiple "tines" help or hinder?
good question, BSR should be able to answer that one, he has been busy lately, but am sure he will chime in soon.

I'm not an RF expert, but here is what I think.

I believe the answer is "Yes, sort of". When transmitting impedance matching becomes a lot more of an issue. That is, you do not want to have any "mismatches". This includes the quality of your cable termination to your connectors as well as the "structure" dimensions of the antenna.

With that said I would still try this antenna as it HAS to be better than that silly wire sticking out of the CM19A. Just don't expect the same proportional gains in transmitting as you get in receiving.

Let me know if you need any more information. I work with an RF expert (he is the one who turned me on to this antenna design) who may be able to answer in more technical details if needed.

Oh, and by the way welcome to Cocoontech!!

BSR, thanks for your help.

I have already modified my CR19a, attached a booster and an additional antenna. I won't be completely happy until I squeeze every last inch of distance out of my devices. I have one ninja camera that is fighting to receive the signals. I have it working 80% of the time - so I know it's close.

I was interested to see if anyone knew the physics of antennas. I have read a number of articles on antennas but haven't seen anything that helped me determine whether this type of configuration would aid transmission. There's lots of info on receiving, but very little on transmission. One thought I had was whether the addional "tines" would hurt the transmission. Maybe your RF expert would have some thoughts - that would certainly help me out.

I have been reading cocoon for a while and was actually surprised when I tried to respond to a message and found that I hadn't yet posted. I guess there's a first for everything! :unsure:

There are different designs that you may want to consider. This is the simplest to build. For instance there are designs for directional only, not spherical.

I also have a CM19A that I would like to control some Ninja pan and tilt units with. I haven't had time to mod my CM19A but I have gotten a visual basic program to work with the Ninjas and the stock CM19A (in the same room, hehe).

I was thinking about having two antennas on each end of the house where the ninjas would be and seeing how that would work with tranmissions out of the CM19A (using an F type cable splitter). Ah, if I only had more time.

You would think someone would already have this figured out considering how many ham radio people we have interested in home automation.

Jeff, would you consider sharing your scripts/screens shots that you are using to control your Ninjas? :unsure:


I will certainly share what I have. I am running Webcam32 where I am using "pull" logic. I also have screens that allow me to switch cameras and control the ninjas. There's not a lot to it, but I'll post them when I'm home.

Interesting idea on the CM19a - having two lines coming from it - each going to different areas. There must be a way to use this idea and boost the signal if there is a loss during splitting. This is where I'm at a loss without the understanding of the physics I have to "try" all of these ideas. To make matters worse, my location is 100 miles away and is currently unheated and below freezing!
Hmm, now this is just an idea and maybe violating all sorts of laws of physics, but here 'gos:

1. Build 2 antennas, one for transmitting and one for receiving.

2. Connect the receiving antenna to an amp with the amplification occurring in the direction of the CM19A

3. Connect the transmitting antenna to an am with the amplification occurring in the direction of the antenna

4. Connect the two antenna/amp combos to a splitter and the splitter to the CM19A

This should give you amplification in both directions, and the circuitry in the amps should ensure that the signal is going only one way, that way only 1 antenna will be transmitting, and one will be receiving. Of course, all this will probably result in a loop, because the receiving antenna will see what the transmitting antenna is transmitting and when this signal hits the splitter, there's nothing preventing it from going to the tx amp, getting amplified, transmitted and so on and so forth. I guess this would be an issue with 2 antennas with or without an amp!

I'm not a Ham radio operator, but use radios a bit at work. All of our amplified antennas have "smart" amplifiers, that is, the antenna wire is not simply ran to the amp and amplified, but rather the amplifier is wired to the radio in a way that it knows exactly when the radio is transmitting or receiving, so that it is only active during transmission, and allows a clear signal path in receive mode.

So maybe this is a bridge to far for a CM19A, unless someone can make some sort of plugin that knows when the CM19A is in tx or rx mode, then the plugin would could switch one of those IR-controlled AB switches. the AB switch would take the place of the splitter in the sketch to avoid the loop problem. I don't think it would work fast enough to effectively receive X10 and transmit whatever the ninja needs. It would probably be better just to amplify the outgoing signal and use something else to receive X10 RF.


This is all just me theorizing, and judging by what BSR has said, amplifying the signal being transmitted may totally throw things out of wack and you may go from 80% reliability to 100% unreliability.
jrfuda, interesting theory, I don't know whether it would work or not! To my advantage, I am using the CM19a only for transmission to the ninjas. I use a W800 for receiving.

I have tested with/without a booster between the CM19a and the transmitting antenna. It definately made a positive difference - so in my case it increased distance.
Jeff, you're very polite. ;) I just went back and re-read my post... Sounds like the rantings of a mad man. :unsure:

You're still only getting 80% with the booster. What's the gain on it? I've seen 'em from 5 up to 20db, and some with a variale gain so you can dial it in.
Jfruda, my gain is 10 db. I have done a bunch of testing (non-scientific) and the booster certainly assists. My 80% number is the success rate of the one ninja receiving the command. It's about 60 feet away. Another unit that is about 70 feet works flawlessly....but of course it's RF and they are about 30 degrees in a different direction.
BSR, my apologies for not posting this earlier. I forgot about my promise until re-reading this posting.

For my ninja control I am using Case's plug-in for the CM19A here. ninja control plug-in

I am using Webcam32 for my camera software - using "pull" logic to get my live video. (I am using dialup service at the location).

For ninja control with the plug-in I use html code that triggers events on Homeseer. Here's an extract of the code I run to control the position of the ninja. The events in HS just utilize the plug-in commands. It's pretty simple and it works well.

<a href="stat">HomeSeer Status</a>
<title>Jeff's Live Webcam</title>

<form method="POST">

<p><input type="submit" Value="Goto Rotor Cam" name="run_event" style="background-color: #C0C0C0">
<input type="submit" Value="Goto Shed Cam" name="run_event">
<INPUT type="submit" value="Goto Satellite Cam" name=run_event>
<INPUT type="submit" value="Goto Driveway Cam" name=run_event>
<INPUT type="submit" value="Rotor Cycling Step" name=run_event style="background-color: #C0C0C0">
<INPUT type="submit" value="Goto Indoor Cam" name=run_event>
<INPUT type="submit" value="Goto Ninja" name=run_event style="color: yellow; background-color: #006600">
<INPUT type="submit" value="Stop Ninja" name=run_event></p>
<INPUT type="submit" value="Ninja - Pos 1" name=run_event style="color: yellow; background-color: #006600">
<INPUT type="submit" value="Ninja - Pos 2" name=run_event style="color: yellow; background-color: #006600">
<INPUT type="submit" value="Ninja - Pos 3" name=run_event style="color: yellow; background-color: #006600">
<INPUT type="submit" value="Ninja - Pos 4" name=run_event style="color: yellow; background-color: #006600">

I hope this helps!

Thanks Jeff:

I've been busy installing my security system and haven't had any time to dedicate to my Ninja pan and tilts, but I'll be sure to reference your code. Thanks again for posting. Examples of how someone does something helps me out a lot!