TM751 or RR501 Transceiver


Just curious, Is the only real difference between these two is that the appilance mod. on the RR501 2-way? Or do I need the 2-way transciever[RR501] for proper polling by HS.

I guess I will find out sometime this week, I am replacing my firecracker interface with the Smarthome USB interface and was wondering if I also need to replace my TM751 with the RR501.

Or will the Smarthome USB interface replace the transcievers all together? Meaning dose the usb interface send the x-10 commands directly thru the power lines, or does it sent it to either the TM751 or RR501 which then sends the x-10 signals? If the SH usb does indeed send the signals direct then I would guess it is capable of sending all codes and not limted to sending just one house code. Is my thinking correct?


Not sure if I understand your question, but the Smarthome USB interface will send and receive X-10 signals from and to your Homeseer PC (all available codes).

If you have any RF devices such as a palm pad remote, stick-a-switch, or wireless motion detectors, you will still need an RF receiver for them (the Homeseer PC and Smarthome USB interface have no way of receiving RF signals).

I would highly suggest that if you have a lot of RF devices, especially motion detectors (which are notorious for flooding your power line with X-10 signals) you obtain an MR-26A or W-800RF32A RF receiver. This will allow the RF signals to be received by Homeseer via the PC's serial port, thus the RF devices do not have to go through the power line. You will then not need any RF Receivers such as the RR501 plugged into your power line.

As always, go to Martin's site at for best pricing on these devices.

MR26A Link

W-800 Link


What the merryman said. Loose the RR501, and go for an MR-26 or one of those W-xxx variants. That is IF you actually need RF pickup. If all you are doing is lighting, then the Smarthome interface will replace the rr-501 or TM-751.

Re-reading your post, I believe you are trying to do the second scenario....therefore you can loose the RR-501.
I was wondering why the RR501 is listed as 2-way while the TM751 isn't. I believe the 2-way refers to the appliiance module on the RR501.

Re-reading your post, I believe you are trying to do the second scenario....therefore you can loose the RR-501.

Yes for now this is what I am doing. But it seems [according to BSR post I would need the transciiever, if I want remotes to work.]

Eventualy I will go with one of the other mention solutions. Is there reason to go with one over the other?

according to BSR post I would need the transciiever, if I want remotes to work.]

This is correct.

Eventualy I will go with one of the other mention solutions. Is there reason to go with one over the other

Well, people who purchased that W-800 device seem to like it and claim they get a lot better reception than the MR26A.

I personnaly use the MR26A with the antenna modification. You can find out how to do on this VERY fine board HERE! (I must say that author is simply brilliant). ;)

Anyway there are a TON of posts about both of these units over at the HS forums also. I have also been pondering if I should spend the extra money on that W-800 device, but the reception I have with my MR26A with that antenna mounted in the attic is good enough for my uses now.

If I had to do it all over again, I think I would have purchased a 9-Pin D to RJ-45 adapters and extended my serial port with Cat5e cable to my attic (and place the MR26A in the attic) and shorten the length of coax cable that goes between the antenna and the MR26A.

As I'm sure our friend Mr. Skiman can verify (gotta love those HAM Radio people in these cases) :( I'm getting a lot of loss through the coax, so my performance would probably increase if I shortened this distance. I think the RS-232 serial communication line (between the MR26A and the computer) can be extended to 100 feet or so (this is the part I'm not to sure of).


Gee... I dont know about 100 feet.... it sure is worth a try. I get a laugh out of some of the antenna mods with respect to loss...They are great designs, and functionally correct... until you account for loss.
1. The antenna as it comes on the MR-26 is a ground plane, the best antenna for all over reception. Adding some wire to the end of the existing wire will in most cases make matters worse, unless you add the correct length to makeup a 1/4 wave.. (there are exceptions)
2. The antenna as described, and so beautifully constructed here:
represents a near perfect 1/4 wave antenna for this frequency. The only thing better would be a solid ground reference plane, and the difference would be very small.
Understanding these 2 points, the only appreciable difference between the external antenna and the internal one, is a good ground plane, and cable/connector/balun losses. Adding th the pc connecting cable adds NO loss.
If you consider that on a good day your connector loss using the finest compression f connectors is about .2db per connector, with 4 connections, that is about a .8db loss, then add for the 50 feet of RG-6 lets say another 1.5db

What does this mean?

Well to me, that means that the best way to get better range from your MR-26 is to move it far far away from the PC. That alone has worked wonders for me. I did not need to fool with the radiators length.
I think I got off on a tangent....

DRB... If you do not use any stick a switches, palmpads, or the like, then all you need is the usb interface that you ordered.
To continue the tangent a little bit, my MR26A was always temperamental. I replaced it with a WGL800 and have been pleased. As has been stated, it's only for receiving RF signals.

The BIGGEST benefit, I think, is the ability to use X10 security devices. The door/window sensors have been showing up at prices like 3 for 20 (USD) or better. These will not work with the MR26A or any of the plug-in receivers. They work fine with the WGL800, HS, and the plugin.

As far as extending RS232, if you're going that far, I'd consider converting to RS485 first. You can build converters pretty cheap or buy them if you feel like it. You should have no problems with 100 foot runs using RS485.

This now concludes my contribution to the tangency of this thread.
I love tangents (sines and cosines also).

I did not need to fool with the radiators length.

But Ski, where is the fun if you don't hack and modify?!?!?!

HEHE, but seriously, this is an issue that I admit I don't understand as much as I would like.

Lets say you have your PC in a Den and where you want to place an antenna would be approximately 150 ft. in your attic (just for example, hehe).

If I read you right, you could run an RG6 coax (I'm assuming 75 ohm here, maybe 50 ohm would be better) that 150 feet to your MR26A and just use its existing cable to go to the computer's serial port and experience minimal signal loss between the MR26A and the antenna.

The reason you move the MR26A away from the computer is not because of cable loss (because you don't use any mods/antennas) but because of the computer interference that would reduce reception??, or is it just to get your MR26A high say to ceiling height?

I guess what I'm asking is should I extend the serial cable and move my MR26A just to get it away from the computer even though I'm running the antenna mod on it? Right now it is next to the computer.


Good point about being able to use those wireless security devices with the w-800, I completely forgot about that! I guess that would make it worth the extra money if you plan on using those.

I am trying to totally get rid of wireless devices in my home and just use the MR26A for remote palm pad operations.

As far as the RS-232 extension length goes, you make some very good points. I guess I would just try it and see if it works (without any communication errors). How expensive are those RS-485 converters?

As far as the RJ-45 to 9-Pin D adapters, HERE is where i got them.

Thanks for the info!

RS485 extension:

It's not unusual for find RS232<>RS485 adapters running $50 or more.

You can build one with the following parts (you'll need one for each end):

1 x ST202 RS232 transceiver (or equivalent), $1.51 or so
1 x SN75179 RS485 transceiver (or equivalent), $1.14 or so
5 x 0.1 uF capacitors (depends on RS232 transceiver used), <$1
1 x 100 ohm resisotr, 100 for $0.99
circuit boards and wire, a couple bucks worst case
DB9 M or F, depending on end, ~$0.50
connection for RS485, a cat5 jack or screw terminals, etc.
5v power supply, regulated

That's it.

The power supply can be on board or off. You could supply it with >5v and regulate on the board. This would add another $1 or $2.

This circuit assumes that you will use at least 5 wires to connect the two devices. This uses a pair of wires, each, for transmit and receive lines. This way you don't need to worry about handshaking. The fifth wire is ground.

You can run power along the cable as well, bringing it up to 6 wires. You'd probably send more then 5v to the far end and then convert it to 5 (if you run 5 from the beginning, it might be too low by the end).

Note: this will not provide power for something like the MR26A as described. However, you can easily connect one or two pins at the MR26A end to provide power from the same source used to power the transceivers. I haven't done this, but it should work. The MR26A normally pulls power from some of the other data lines in the RS232 connection (RTS? DTS?).

It might be tough to fit this into one of the small DB9 <-> RJ45 adapters using through-hole techniques. It would be relatively easy with surface mount - buth harder to make.

Great info.

BTW, you can loop the unused connectors out of the side of those adapters in cases where you may want to connect an external device (such as a power supply or other board) into the Cat5 cable.

I just wish that they made an adapter the size of the 25-pin ones but that used a 9-pin connector. The 25-pin ones should barely have enough room to put this stuff in (the RJ45 takes up a lot of space in there).

I usually end up using the 2-space surface mount boxes you can buy to put keystone jacks in (from HomeDepot, etc.). A cat5 keystone goes in one of the spaces and I cut a hole in the side for the DB9. It can still be a tight fit.

Sounds like you have some good stuff in the responses here.

To get back to some of your earlier questions, what does the 2-way mean in the RR501, I'm not sure but I think it only has to do with the appliance module that's in the bottom of the plug.

I would agree with the other comments here - lose the plug-in transceivers. They are great for someone starting out with home automation to learn about the technology and get a chance to work with it.

If you're on a tight budget, the MR26 is OK for a short range but gets decent range if you make an antenna like BSR descibes in his how to article. Please read his desciption of how to make this is you're interested. That's an impressive set up.

A lot of HomeSeer users really like the W800RF32 antenna. Not only does it extend the range a little more, but it also incorporates the security devices and takes all of the IR traffic off of your power line. Big benifits.

A lot of the HomeSeer users might cringe at this, but I auctually use the V572 antenna myself. It has the range of the W80032RF but does not connect directly to the PC. I can't use the security devices (I plan to do that with my ocelot and wired contacts) and it doesn't take traffic off of my powerline (I don't have what I consider too much traffic), but it does give me what I feel is an additional layer of reliability - if the PC goes down, my RF still works.

Pros and Cons with both solutions. I think it's a personal choice....