Kenwood TM-281A

[EMA56]

TM281 Mod

Ok, so now I'm seeing that there are potential problems with the mod. Out of the 15-20 radios that I modded, I had one "un-modify" itself. While that makes absolutely no sense, this radio worked fine across all frequencies for months only to stop transmitting on the full range suddenly. It would receive just fine, and transmit in the original 144-147(?) range, but not the extended range. I reprogrammed it using the MCP1A software, and I have performed a full reset to no avail. I am not necessarily looking for help, (we are currently using this radio as a scanner), but after reading the last few posts, I am aware that this might not be an isolated incident. Why it would suddenly stop working is the oddity.

At any rate, before I attempt this TM281 mod, has anyone else heard of any issues?

 

[Dimigrey]

Kenwood TM 281A programming help

CTCSS questions for kenwood.. i know how to set it up to decode incoming signals into the radio..This is basicly
the same as adding QT/DQT Decodeing vaule to the SVO scanning mode. But i havnt figured out how to set up the QTDQT encoding vaule numbers. Is anybody familer with how to do this to this radio?

thanks

 

[ST-Bob]

If you're talking about DCS (Digital Coded Squelch) it's pretty easy. Set the tone type to DCS and then select the DCS code. Save it to a channel and you're done.

Page 48 of the manual tells you how:

To activate DCS, press [F], [CALL].
• As you press [F], [CALL], the selection cycles as follows:
“OFF” ➞ “TONE” ➞ “CTCSS” ➞ “DCS” ➞ “OFF”.
• “DCS” appears on the upper part of display, indicating that
the DCS function is activated.
When DCS is ON, you will hear calls only when the
selected DCS code is received. To answer the call, press
and hold Mic [PTT], then speak into the microphone.
Note: You cannot use the DCS function and CTCSS/ Tone functions
simultaneously. Switching the DCS function ON after having
activated the CTCSS/ Tone functions deactivates the CTCSS/ Tone
functions.
SELECTING A DCS CODE
1 Press [F], [MENU] and turn the Tuning control to
select Menu No. 4 (DCS).
• The current DCS code appears.
2 Press [MENU] and turn the Tuning control to select
your desired DCS code.
• The current DCS code appears and blinks.
3 Press [MENU] to store the new code or any other key
to cancel.
4 Press any key other than [MENU] to exit Menu Mode.

 

[KE4RWS]

Prying off components???

All this talk about "prying" R768 off the circuit board is making me cringe. I hope you guys are at least heating these components before wringing them off the board. If not you're bound to inflict damage that might not be apparent right away. But I've read a few posts where folks have referenced yanking, cutting, snipping and even ripping the SMT resistor right off the circuit board and I can only shake my head in response to such brutal madness :roll:

It really is well worth it to either use appropriate solder/de-solder gear, or just take it to someone who has the right equipment do it for you. But if you are trying to use an amateur radio for other than amateur radio purposes (transmitting that is), then you're better off buying a genuine commercial radio vs. run the risk of being caught using a TM-281 on the marine band, fire department, private business, etc. The fines are quite stiff for this kind of violation. But IF you're gonna do it anyway you might want to think about *not* reference it here

 

[VooVoo]

Sorry to reopen this but I just picked up a 281 that was already modded. I do search and rescue for the county and need a radio that was cheap (inexpensive) and was narrow band capable.
My question is some of the station I need to program use qt/dqt dec and qt/dqt/end. Some are the some but a few are different. I don't see in the MCP-1a program how to put both in.
An example is:
rx - 155.6400 tx - 154.7100 dec is 173.8 enc is 146.2

Any help would be appreciated

 

[mrweather]

It may not be possible. Ham-grade radios typically don't have split tone functionality.

 

[SCPD]

It may not be possible. Ham-grade radios typically don't have split tone functionality.

Yes very true. My Motorola XTS 5000 can do this but I don't think the TM-281A can. I'll have to check later tonight.

The TM-281A can be configured for any shift of the Tx Freq but I don't know about split tones.

 

[VooVoo]

I appreciate you guys looking into this. I only have a couple with split tones so I may have to live with it. If I can ask another question though. In MCP-1a, for those that have a rx/tx tone that is the same where do I program that? When I program a channel it gives me an option for tone, CTCSS and DCS. I can only check one of them. Most of my freq have a tx tone but how is that inputted wihtout an rx tone?

Thanks again for all the help.

 

[perry211]

Software

Sorry to reopen this but I just picked up a 281 that was already modded. I do search and rescue for the county and need a radio that was cheap (inexpensive) and was narrow band capable.
My question is some of the station I need to program use qt/dqt dec and qt/dqt/end. Some are the some but a few are different. I don't see in the MCP-1a program how to put both in.
An example is:
rx - 155.6400 tx - 154.7100 dec is 173.8 enc is 146.2

Any help would be appreciated

I use the Software from RT Systems. It has enc tx and dcode receive. You may have to buy this. Sorry it can't be copied. You have to use the one and only install CD that you get.
Good Luck, Perry KK4PWS

 

[VooVoo]

Thanks. I'll look them up and see what I can find.

I appreciate the help.

 

[VooVoo]

Thanks Perry. I took a look at the software. Not much of a description but do you happen to know of a source for just the program. I just bought a cable!!! They're not cheap. I'll also ask around to see if any of my SAR buddies may have it.

Thanks again for the info.

 

[SCPD]

Well I'm not sure how the RT systems software is doing it... but per the TM-281A manual on Page 24 you can only use TONE or CTCSS or DCS at one time. When TONE is chosen the CTCSS and DCS options are not available.

I checked on the latest MCP-1A software and it confirms what the manual describes.

However, this doesn't mean you cannot use the radio. With TONE enabled that means you'll receive ALL signals on the Rx frequency. So you can still Tx and Rx just fine.

This just means that you'll hear everything on the Rx channel. You won't get the benefits of CTCSS.

 

[VooVoo]

Thanks Nick. I didn't know if modding it changed any of that. In MCP-1a it has the same numbers in the tone section that it has in the tones and not being a ham guy didn't know if tone was rx and CTCSS was tx. Our unit has a few ham guys and are talking about putting on some classes to get those of us interested in the ham side of the house.

I really do appreciate all the help from you guys. I'm sorry if I sounded like a jerk at times. I'm not a very patient person when I have something I need to figure out.

You all take care

 

[mrweather]

Yes very true. My Motorola XTS 5000 can do this but I don't think the TM-281A can. I'll have to check later tonight.

It's unfortunate because many mobile ham radios come from commercial platforms. Really, it's just a firmware thing nowadays so why not enable the functionality? Heck, even my 25 year old Motorola Sabers can do it!

 

[SCPD]

It's unfortunate because many mobile ham radios come from commercial platforms. Really, it's just a firmware thing nowadays so why not enable the functionality? Heck, even my 25 year old Motorola Sabers can do it!

If you look at the service manuals between commercial and HAM radios they look the same but the CPU designs are different. Most commercial rigs will have multiple encoder lanes whereas the HAM rigs only have a single lane.

It all comes down to cost.

 

[VooVoo]

Sorry but I'm back again. I took a look at the RT software. Looks good but I think I'll still have the same issue.
I've read through the replies and am still unsure if I'm doing the right thing here.

If I have a channel that has the same freq on rx and tx but different tones I can't do both!! If the tone is on the rx side do I set it in the tone section of MCP? If it's on the tx side, do I set it in the CTCSS box or visa versa?

Most of the channels I have are simplex so no issue there. The listing I have for freqs show enc and dec. No mention of CTCSS. Is this the same thing just different terminology?

This is what I'm trying to do.

Channel Name RX Dec TX Enc
1 PC4X4 155.1750 155.1750
2 WASAR 155.1600 155.1600
3 OSCCR 156.1350 156.1350
4 WASAR2 155.2425 155.2425
5 WASAR3 155.3025 155.3025
6 TMRU 155.2050 155.2050
7 GSSD1 155.2200 155.2200
8 GSSD2 155.2650 155.2650
9 NWBH 155.2350 155.2350
10 DEM 156.2400 156.2400 162.2
11 LERN 153.3700 153.3700
12 DEMREP 151.3550 167.9 151.3350 167.9
13 AIRLIFT 155.2800 155.2800
14 PCSO E DISP 154.9500 159.0300 131.8
15 PCSO W DISP 155.6400 173.8 154.7100 146.2
16 GRN WTR 154.5400 100.0 154.5400 100.0
17 PCFIRE1 153.8900 131.8 153.8900 131.8
18 PCFIRE2 154.3550 154.3350 131.8
19 PCFIRE3 154.1600 154.1600 131.8
20 PCFIRE4 154.2650 154.2650 131.8
21 PCFIRE5 154.3850 154.3850 136.6
22 DNR1 151.4150 151.4150
23 DNR2 159.2550 151.2050 114.8
24 USFS 169.9000 169.9000 146.2
25 FSC2C 169.9000 164.1500 167.9
26 WSPTACW 155.5200 155.5200 151.4
27 WSPC2C 154.9050 154.9050 151.4
28 WSPTACE 154.7400 154.7400 151.4
29 WSP AIR 159.0750 159.0750

These are right from my Sheriff's radio programmed by the dept. A Kenwood Tk-290. It has more programmed into it but don't need those for my vehicle.

Thanks for being patient with me. I appreciate it!!!!

 

[SCPD]

I presume you'll be transmitting on these. If so, you just need the Tx tone. You can ignore the Rx tone. Yes, CTCCS is the full term for "Tone Encode" -- CTCSS usually refers to the receive side whereas "Tone" refers to the Tx side.

The only caveat to not having the Rx tone is that you may hear other users of that frequency. The Rx tone allows you to isolate traffic from specific users only. The 281A isn't capable of that.

BTW, your AirliftNW frequency is actually AMR (Ambulances) only. AirliftNW is a VHF P25 (155.295) frequency. You can't hear that channel with the 281A.

 

[SCPD]

I just looked up the RT Systems software. It looks like they do things differently. Gotta love 3rd party programs. The MCP-1A software is pretty easy.

They have a mode selection first and then your Tx Tone and then Rx Tone. See, even they're not consistent with their terminology. They have CTCSS and Rx CTCSS. Silly programmers.

Just select Tone for mode and put in the Tx Tone frequency. Done. You can try setting up the tone for Rx but I don't know if it'll work.

 

[hoppy1313]

TM-281A Modification Update

Problems with my brother's two Kenwood TM-281A radios after modification solved. Radios do not have much current draw in receive, hence, his was working perfectly after the modification. However, when you transmit you must ensure you have a large enough power supply to handle the transmitter's power output. My brother's appearance of a problem was because his power supply couldn't handle the current draw for a 65W transmitter. He brought his radios to my mom's house (both of us were there for her 80th birthday) and I took a look at them. No apparent damage or issue. He didn't bring a power supply, so, we connected the radios to the battery on my mom's car. Everything worked as it should.

As a technician two things come to mind... First, when doing any transmitting testing, use the lowest power setting. Second, make sure the power source being used can handle the load being places on it.

Thanks to all who gave ideas and assistance.


Hoppy
N8OX

 

[bertedmund67]

Well done!