CDM remote mount - main body front?

[g8tzl2004]

I have a CDM1550 remote mount head with an RJ45 socket in the back.

I also have a CDM body which used to have a head but this has been removed and all that is left is a floating flex cable.

I need a blank front for the CDM which has an RJ45 socket so I can connect it to the remote head via a straight thru RJ45 cable.

I have a simple question - can I use a blank front from any CDM version ie 750,1250,1550 etc OR do you need to match the blank head to the particular radio remote head?

Also I have seen some images of the remote mount kits and there appears to be "well populated" circuit boards both in the remote head and the blank front head. I had always assumed that the remote head kit basicaly just extended the "flex" cable from the main body to the remote head..so there was no need for any electronics...just a very long flex (RJ45) cable. But I don't think this is the case. What is the electronics for..is it acting as an amp to overcome control signal losses due to the long cable length??

Thanks

[SteveC0625]

I have a CDM1550 remote mount head with an RJ45 socket in the back.

I also have a CDM body which used to have a head but this has been removed and all that is left is a floating flex cable.

I need a blank front for the CDM which has an RJ45 socket so I can connect it to the remote head via a straight thru RJ45 cable.

I have a simple question - can I use a blank front from any CDM version ie 750,1250,1550 etc OR do you need to match the blank head to the particular radio remote head?

Also I have seen some images of the remote mount kits and there appears to be "well populated" circuit boards both in the remote head and the blank front head. I had always assumed that the remote head kit basicaly just extended the "flex" cable from the main body to the remote head..so there was no need for any electronics...just a very long flex (RJ45) cable. But I don't think this is the case. What is the electronics for..is it acting as an amp to overcome control signal losses due to the long cable length??

Thanks

The Remote Front Housing and Remote Mount PCB Front are the same in both remote kits. The Remote Front Housing is part number 1564270B01. The Remote Mount PCB Front is GMLN4086A. (These are the items you say you are missing.) My manuals indicate these are the same for both remote kits.

There is one single kit for the 1250/1550 radios. The Motorola part number is RLN4802 for the kit less the remote cable. RLN4801 is the part number for the 750 remote kit.

BTW, those are not RJ45's. They are RJ50's which have 10 pins instead of 8.

[Bill_G]

RJ50. So, that's what those are called. I got bit in the butt by that years ago when I went to put a cable stretcher on mics for a bunch of CDM's. Oh oops!

[g8tzl2004]

Thanks - good to know that the blank "Remote Front Housing and PCB are the same on all CDM version so there is no need to use the correct version.

OK on the RJ50. I have previously used a straight thru 8 pin RJ45 and that works OK - you only need the 10 pin if you are using a telephone type handset. Standard mics works OK with the 8 pin.

[SteveC0625]

OK on the RJ50. I have previously used a straight thru 8 pin RJ45 and that works OK - you only need the 10 pin if you are using a telephone type handset. Standard mics works OK with the 8 pin.

You are correct. A number of folks have reported good results using a standard CAT5 cable in place of Motorola's remote cable and for 8 pin mics as well. However, there is some concern that inserting an 8 conductor RJ45 into a 10 conductor RJ50 may damage the two outboard pins (#9 & #10). I found articles or posts here, on repeater-builder, and on RR on the matter. It's a debatable issue and there are fair arguments on both sides.

I took the cautious route and purchased a bag of RJ50's for the cable ends and the proper crimping die. I've been able to make up custom length remote cables for the CDM's and also to replace RJ45's on various mics like the HMN1038 and the HMN1056. It may (or may not) be overkill, but it gives me great peace of mind. It also gives me the ability to easily replace trashed connectors on many different mics as I also have a bag of RJ45's.

[Garyf629]

My experience has been, that if you use a CAT5e cable from the drawer to the head, you will not be able to use the speaker in the control head. The 2 missing pins carry the audio signal.

As Steve did, I purchased the RJ50's, a roll of flat 10 conductor telephone cable, and crimp die. All very easy to find. I have made cables upto 150' with no problems.

[g8tzl2004]

The speaker in my CDM1250 remote head works OK using an 8 pin RJ45 straight thru cable.

One thing I found was that not all 8 pin RJ45 cables are straight thru..some are crossed.

Do you have to glue the cable outer cover into the RJ50 after you have crimped the leads?

One thing I found with my RJ45 8 pin cable (which was not a cat5 lead but used a "flatter" type cable) was that if I TX'ed near the head with a handheld, the CDM rebooted!!! I guess RF was getting into the head via the unscreened RJ45 cable. I presume the real Motorola cables are all screened?

[SteveC0625]

The speaker in my CDM1250 remote head works OK using an 8 pin RJ45 straight thru cable.

One thing I found was that not all 8 pin RJ45 cables are straight thru..some are crossed.

That most likely accounts for the speaker not working in Gary's situation. I've not encountered that yet.

Do you have to glue the cable outer cover into the RJ50 after you have crimped the leads?

I bought the RJ50's in both flat cable and round cable versions. The flat cable RJ50 crimps down quite nicely on the cable jacket with no need for glue.

One thing I found with my RJ45 8 pin cable (which was not a cat5 lead but used a "flatter" type cable) was that if I TX'ed near the head with a handheld, the CDM rebooted!!! I guess RF was getting into the head via the unscreened RJ45 cable. I presume the real Motorola cables are all screened?

I have not seen screening or sheilding on the Motorola cables. I've cut a long one into shorter sections with no problems.

[sambo37]

Hi All,

Tried extending cable using CAT5 as suggested in this thread. Left off pins 1 & 10 also as suggested. Display is fine and rx functions; but, on PTT the display flashes on and off. Voltages stable, checked cabling, looks correct. Any suggestions much appreciated.

Thanks,
Sambo37

[sambo37]

OK on the RJ50. I have previously used a straight thru 8 pin RJ45 and that works OK - you only need the 10 pin if you are using a telephone type handset. Standard mics works OK with the 8 pin.

You are correct. A number of folks have reported good results using a standard CAT5 cable in place of Motorola's remote cable and for 8 pin mics as well. However, there is some concern that inserting an 8 conductor RJ45 into a 10 conductor RJ50 may damage the two outboard pins (#9 & #10). I found articles or posts here, on repeater-builder, and on RR on the matter. It's a debatable issue and there are fair arguments on both sides.

I took the cautious route and purchased a bag of RJ50's for the cable ends and the proper crimping die. I've been able to make up custom length remote cables for the CDM's and also to replace RJ45's on various mics like the HMN1038 and the HMN1056. It may (or may not) be overkill, but it gives me great peace of mind. It also gives me the ability to easily replace trashed connectors on many different mics as I also have a bag of RJ45's.

Hi Steve,

I've made-up a CAT5 extension cable for remote mounting a CDM1550 as suggested in this thread. The display works fine and Rx functions properly; however, when I key the mic the display flashes on and off and no OP. I've verified the wiring and am not seeing any voltage drops. Shouldn't the reference above to pins #9 & #10 actually be to pins #1 & #10, the two outside pins?

Thanks much,
sambo37

[SteveC0625]

I've made-up a CAT5 extension cable for remote mounting a CDM1550 as suggested in this thread. The display works fine and Rx functions properly; however, when I key the mic the display flashes on and off and no OP. I've verified the wiring and am not seeing any voltage drops. Shouldn't the reference above to pins #9 & #10 actually be to pins #1 & #10, the two outside pins?

I followed the pin numbering from the CDM manual for the RJ50. It's different than just numbering right to left as 1 through 10. The Motorola pin numbering allows some continuity from the 8 pin RJ45 that was so common on the MaxTracs, Radius, and others to the RJ50 on the CDM's. The left and right outboard pins are #9 and #10 in this situation. Using a standard CAT-5 cable works because it ignores the outside pins. If you are making your own cable, match it to a CAT-5.

[g8tzl2004]

Maybe RF is getting into the cable when you TX?

With my 8 pin RJ45 cable which is not actually a CAT5 type, if I TX'ed with a HT close to the CDM, it rebooted. There was no problem TXing using the CDM as my antenna is external and mounted well away from the CDM.