Modifying the antenna on a TM751 or RR501 is not something I recommend. It can have serious consequences, like DEATH from electrocution. You must galvanically isolate any external antenna used with these modules as their electronic "ground" is the hot side of the 120V mains. The CM15A electronics are isolated from line voltage so it's safe to replace its antenna.
The thread you cited at AccessX10 is too muddled to make much sense of. The MR26A antenna that one poster cited was based on my original antenna design for the BX24-AHT. I've since found the eggbeater to be a better design.
The CM15A antenna is fixed length and cannot rotate as freely as those on the TM751 or RR501. To have it horizontal, it would have to point out from the unit and wall.
Most X-10 receivers have 25-35 foot range. My CM15A range is much greater than it was with the OEM antenna.
I don't think much of X-10's software (or firmware) for the CM15A but the hardware is excellent. IMO, it's worth a (small) bit of effort to make use of it.
Do you think that's why they changed the design of the aerial with the CM15A? (BTW, what's the difference between "aerial" and "antenna" - or is there one?)
Was that a standard way of building cheap transceivers? It seems like a weird way to do things unless it saves a lot of money in assembly or part costs.
It's not hard to predict that some simpleton getting crappy reception would open that sucker up and try to attach a wire to the PCB where they assumed the antenna connection was. After all, we've seen some pretty frightening reports from the field here in CHA about what people do with lethal voltages. I'll bet more than one poor schlub's gotten a blast of 110VAC after trying a simpleton mod.
The modification photos made the CM15A changes look fairly easy, with enough room inside the case to mount a real "F" type connector. Damn it Dave, now I am going to have to go out and buy one of these suckers, if only to avenge the death of the TM751 I tried to modify! The pictures at:
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make it look *so* easy!
Such is the way with web-based forums. I am not very fond of them but sometimes that's all there is. It's sad that so much of the discussion of X-10 is taking place elsewhere.
Was that the twinlead turnstile design found here:
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They talk about 50 ohm cable on the drawing but 75 ohm cable in the specs. Which one is it, do you know? U
If I understand correctly, your unit had a built-in signal strength meter. I submit that's really the only way to lend some objectivity to claims of enhanced reception. A lot of the posts I've read have been lacking that real world quantifier: is the signal really stronger after an antenna change? Since you've got an iron-clad way to test for improvement, once again I have to defer to your knowledge. How much better is the eggbeater than the turnstile in practical terms? Is the BX24-AHT still available anywhere?
That certainly undercuts the usefulness of my prior advice! :-) (Note to self: Restrict commentary to devices actually owned!)
There were some interesting mods listed at that URL that talked about using model airplane RC antenna tubes to make it possible to position the aerial more freely. That looked like a pretty simple mod that I might be able to do without fouling up. It does look like there is enough room inside the unit for even a klutz like me to install an F-connector and putting in a standard connector seems to be the only way to "do it right."
I don't doubt that. You're also probably got more electronics skills than
99% of our posters. I don't want to insult anyone, but a number of posts on the subject indicate that at least a few others aren't as gifted. I think that skill has some effect on the outcome of antenna mods. That's why I'd recommend moving the unit around before anything else. It's a solution with far less destructive potential than adding a new antenna. You have convinced me that a well-executed CM15A antenna mod will seriously extend the reception range. I'm just not convinced it's within everyone's skill set. :-)
Hmmm. If they start selling them for $25 or so, I might take a look. I can see some distinct advantages from the marriage of all-housecode RF with both PLC and PC interfacing but I've been happy with my relocated TM751. I mounted it on top of a tall bookcase in the living room, which is about dead center for the house and oriented the antenna horizontally. I also ran a
110VAC line right from the transceiver to the breaker panel which really strengthened the X-10 powerline signal throughout the house. Before that the TM751 was located at the far end of branch that had a lot of appliances and electronic devices on it.
Thanks for your input Dave, appreciated as always!
OK - I'm sorry. I'm never quite sure what netiquette rules are in forces. In some places I would be branded a stinking top poster for answering like this! :-)
I've checked out the links. Thanks. And thanks for the answers, which stand without much comment. I think I'll wait until the CM15A's been around a little bit longer to let them get the kinks out
It gets too confusing for us geezers to try to respond inline so...
Follow the links on my CM15A page
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one of which will eventually lead to...
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which has much clearer pictures. As I note in the text on my page, I recommend using a 50-ohm BNC connector and 50-ohm coax (RG58/U). I buy it with preassembled BNC connectors.
The RSSI measurement of the receiver linear output made with the BX24-AHT wasn't really useful for making definitive comparisons between antennas because the RF receiver module had AGC which reduces the gain as the signal gets stronger. It was useful for fine tuning the receiver. Lacking expensive lab style equipment, the most reliable measurement is to compare range.
People who built the BX24-AHT found they got excellent range with either the turnstile or the eggbeater. My experience was that the eggbeater was a bit better. It's easier to construct and needs no balun but the 93-ohm coax for the phasing line is not easy to find. You can cheat and use 75-ohm without too much of a penalty. One person who built it with 12 gauge insulated solid copper wire, a 75-ohm phasing line and the TenTec preamp got 175+ feet through several walls in his condo complex. I've measured 200+ feet here.
The BX24-AHT plans, part lists, schematics, firmware and software can all be downloaded from my web page but there is no source right now for the boards. My health is too iffy so I don't have plans currently to make the boards available again.
All X-10 made mains modules, except for those with RS-232 or USB interfaces, use the hot side for electronic ground. I think it has to do with noise. The serial interface requires isolation by UL. That's why the design is different for the CM15A.
They also used third party RF components which was probably done for cost reasons. They are dirt cheap from China. (I paid under $2 each for SAW controlled RF transmitter modules in fairly modest quantities.) You can even get boards made there in very low quantity and shipped via FedEx with about a 10 day turn around.
Aerial and antenna mean the same. Aerial tends to be used >> can have serious consequences, like DEATH from electrocution.
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