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Author Topic: Project To Increase Range Of CM15A  (Read 243674 times)

nklght

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Re: Project To Increase Range Of CM15A
« Reply #30 on: November 25, 2006, 03:56:32 AM »

Thanks for pointing that out,
I never considered that some cable grades are not suitable for RF.  I know what is best to use at home for A/V, but have never considered what is best for RF.  My problem is that the prime location is a wall with no electric, I pulled the USB trick when my office was upstairs, and was able to move the CM15A closer to a central location by running a USB line, but we still had to move around the house inorder to get the unit recieve the remote signals.  I am wondering what type of antenna I should put in the wall and if I do the f-connector mod, can I connect the new antenna to the CM15A.  I want to run my CM15A with an antenna loctated 15-20 feet away.  Using f-connectors, the appropriate coax, and antenna, that should be possible.   
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Brian H

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Re: Project To Increase Range Of CM15A
« Reply #31 on: November 25, 2006, 06:35:17 AM »

As a test I used the antenna from a WGL V572AB and it worked well. I think in another thread someone indicated that they where able to get just the antenna as a replacement part form WGL.
I have also seen a few construction projects to make one. One I remember had 4 ground plane elements sticking out at 90 degrees from each other. That one maybe harder to use in a wall.
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Duck69

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Re: Project To Increase Range Of CM15A
« Reply #32 on: November 25, 2006, 06:00:15 PM »

That was yours truly back in May. Here is the info. :)

For those of you who do not want to build your own antenna you can purchase an antenna kit (antenna & mounting bracket) from WGL and associates.  8)

Web site & e-mail : http://www.wgldesigns.com  wgl@wgldesigns.com 
You can't order just the antenna kit from the web site.  ???

You can write to:
WGL & Associates
5418 Lancashire
San Antonio, TX 78230
or
Call: (210)342-2858
The cost is $8 plus $5 S&H

 ;D 8) ;D
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medvampire

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Re: Project To Increase Range Of CM15A
« Reply #33 on: December 07, 2006, 09:57:58 PM »

I did the mod for the f connector listed at this site.
http://www.accessha.com/howto_fconnector_page1.html
I don't have a great antenna on just a chunk of cable plugged in the f connector going up the wall and about 12 inches of the inner core stripped. I have about 150 ft range up from about 25 ft.
I have removed the repeater from the system witch removed some of the delay issues.
I was not too impressed with X10 until I done this mod but the WAF  ;D and my approval is on the upswing.
I did take note of another antenna in the box. Is the transmit antenna on a separate daughter card on the main board of the CM15? If this is the case the receive antenna may not be a crital design but the transmit would be a case where you will need to match the lenght of the areal to match the frequency and SWR of the sending circut.
Steve
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Puck

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Re: Project To Increase Range Of CM15A
« Reply #34 on: December 07, 2006, 11:11:28 PM »

I did take note of another antenna in the box. Is the transmit antenna on a separate daughter card on the main board of the CM15? If this is the case the receive antenna may not be a crital design but the transmit would be a case where you will need to match the lenght of the areal to match the frequency and SWR of the sending circut.

Yes, the Transmitter & the Receiver are on different daughter cards. The internal antenna is the Transmit one... and oddly enough, it has good range. I haven't had any problems with it and I can't recall any posts here complaining about it either. Maybe not enough people actually use this feature(?).

Since generally everyone does use the receiver, more range issues are mentioned here. Therefore, the length of the the receiver's antenna becomes a more important issue to achieve maximum efficiency.
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Puck

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Re: Project To Increase Range Of CM15A
« Reply #35 on: December 11, 2006, 12:21:47 PM »

I've been trying to find RG58 50 Ohn cable with Coax connectors to no avail.   :o

Standard F-Connectors are generally only found on 75-Ohm cables (RG-6, RG-59).
You most likely would have to build your own. (I do believe the standard F-connector will fit on RG-58 cable.)

Or you could get a pre-made Radio Shack BNC Cable and use an BNC Plug to "F" Jack Adapter. Or replace the Female F-Connector on your mod'ed CM15A to a BNC Chassis-Mount Jack.


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Brian H

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Re: Project To Increase Range Of CM15A
« Reply #36 on: December 11, 2006, 06:07:05 PM »

Just to confuse us more. My WGL V572A came with a 12' coax cable. F connectors on each end and it is RG6U. Yes 75 ohm.
Duck69 do you need 50 ohm with an F connector or did you use a different type on your mod?
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Puck

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Re: Project To Increase Range Of CM15A
« Reply #37 on: December 11, 2006, 06:40:31 PM »

Just to confuse us more. My WGL V572A came with a 12' coax cable. F connectors on each end and it is RG6U. Yes 75 ohm.

Most likely reason for this is economical; RG-6 is cheaper and more readily available to the user if 12' is not long enough. A mono-pole antenna (like the V572A) has an impedance of 37 Ohms when it's length is 1/4-wavelength of the intended frequency. This is why 50-Ohm cable is better to use than 75-Ohm. I would not be surprised if WGL loads their antenna & receiver to match a 75-Ohm transmission line.

That's the theory side of it anyways.  ;)
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Brian H

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Re: Project To Increase Range Of CM15A
« Reply #38 on: December 12, 2006, 06:51:33 AM »

Puck; Makes sense. My RF theory is getting rusty as I no longer do Two Way Radio Repair and my FCC Radio Telephone License gatehers dust.  ::)
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Puck

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Re: Project To Increase Range Of CM15A
« Reply #39 on: December 12, 2006, 02:50:07 PM »

I just did a calculation of the front end of the CM15A's receiver. They have an 82nH inductor (L4) in parallel with a 68-Ohm resistor (R4).

The inductive reactance of L4 at 310MHz is 160-Ohms.

160-Ohms in parallel with 68-Ohms give an impedance of 47.7-Ohms @ 310MHz.  ;)

Duck69: you said your setup has been working quite well; then you shouldn't see worse operation with 50-Ohm cable. :D

Hopefully you had some questionable areas to get a better idea if this made a difference.

Quote
BTW: The UM506 has problems responding when COLD. The one I have in the garage takes several tries. After that it works with the first try.

KDR is experiencing a similar problem (UM506 Universal Module Cold Weather), and I have an appliance module in my garage that stuck in the on position when the temperature dropped closed to -30C a couple weeks ago (it's working again in normal temperatures).

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Duck69

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Re: Project To Increase Range Of CM15A
« Reply #40 on: January 03, 2007, 03:10:57 PM »

I was finally able to check things out.

 ;D The RG58 does make a difference. Longer range, very reliable.  ;D

LOCATION is very important, so don't go putting holes in your house before thinking it out.

I put it in a closet, hung it on a curtain rod, fed it through a vent and hung it out a window.

Hanging it out the window and hanging it on an attic vent (Vinyl), worked best (FOR ME).  ;D

Everyones home is different, so what has worked out best for me won't necessarily work out for you.
So, I highly recommend testing it in several different locations.


Next I will be drilling a hole from the closet where the CM15A is plugged in to the outside and permanently mounting it.
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Puck

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Re: Project To Increase Range Of CM15A
« Reply #41 on: January 03, 2007, 03:19:30 PM »

That's good to hear it had an improvement Duck69  :)

Did it improve a previous issue with Abyssmal Range with Slimfires and Credit Card Remotes;)
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dave w

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Re: Project To Increase Range Of CM15A
« Reply #42 on: January 04, 2007, 12:31:32 PM »

Hey RF guys,  need some help here!

As Brian said earlier, my RF is rusty (heck my Ohms Law is rusty...but I digress). My simple antenna coupled to the modified CM15A is a coax with 18 inches of shield stripped back. The 18 inches of center conductor and foam covering is stuck up through the ceiling into the attic. It works pretty well, but I have a couple of dead spots and am wondering if a 1/4 wave would work better? Initially I went with the 1/2 wave because the "That was easy" antenna design I used, obviously has no ground plane.
If I went to a 1/4 wave, the best ground plane I could make, would be cookie sheet baking pan with a hole in the middle for the coax shield.

Any thoughts on how effective this might be?
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Puck

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Re: Project To Increase Range Of CM15A
« Reply #43 on: January 04, 2007, 01:00:23 PM »

If I went to a 1/4 wave, the best ground plane I could make, would be cookie sheet baking pan with a hole in the middle for the coax shield.

Dave: Since you are effectively making a mono-pole antenna, you should use a 1/4 wavelength. Even thought the cookie sheet would probably work as a ground plane, I can see it acting as a shield to anything that is below it in it's RF shadow. Since you will basically be cutting half of your current antenna off, just take that piece and solder it to the cable's shield and place it horizontally.
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dave w

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Re: Project To Increase Range Of CM15A
« Reply #44 on: January 04, 2007, 01:46:51 PM »


[ Even thought the cookie sheet would probably work as a ground plane, I can see it acting as a shield to anything that is below it in it's RF shadow.

oops I hadn't even considered that, although there aren't any motion detectors for at least 10 feet from antenna location, there could be a Palm Pad used in the shadow.

OK I'll make it a quarter wave this weekend and let you know if I eliminated the dead spots.

Thanks!

...now about those two parallel resistor that I can't figure I/R drop across   ;)
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