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-   -   Kenwood TM-281A (https://forums.radioreference.com/amateur-radio-equipment/220926-kenwood-tm-281a.html)

nickcarr 09-08-2011 5:27 PM

Kenwood TM-281A
 
I just placed my order at HRO as these just came in stock.

Kenwood TM-281A Mobile Transceiver TM281

There's no brochure or manual on the Kenwood site but I did manage to find the manual online:

http://images.kenwood.eu/files/prod/...M2_English.pdf

I'll post a mini-review when it arrives next week.

W9BU 09-08-2011 5:57 PM

While this radio may be "narrow-band capable", according to the manual, this radio does not have 7.5 kHz tuning steps. However, it does have 2.5 kHz steps, so you should be able to listen to narrow band VHF signals on the correct frequency.

nickcarr 09-08-2011 6:49 PM

I'm not sure I understand your comment. If the radio supports either 2.5 or 3.125 steps (or in this case 6.25) then it's narrowband compliant.

You do not "need" true 7.5 steps if you already have 2.5 steps.

W9BU 09-08-2011 10:43 PM

Narrowband and VFO step size are not necessarily the same thing. Narrowband, in the context of VHF land mobile radio, requires a receiver and transmitter designed for 11kHz bandwidth frequency modulated voice (emission designator 11K0F3E) instead of 16kHz (16K0F3E) or 20kHz (20K0F3E).
The narrowband channel spacing in the VHF land mobile band is 7.5kHz instead of 15kHz like we've had in the recent past.

So, your statement that 2.5 or 3.125kHz steps makes the radio narrowband compliant isn't exactly true since the step size does not define the bandwidth of the receiver or transmitter.

However, your statement that 7.5kHz steps are not required if you have 2.5kHz steps is true.

ST-Bob 09-09-2011 11:20 AM

According to the factory rep I talked to at HRO in Salem NH a couple weeks ago, the TM-281A is a replacement for the TM-271A and is nearly identical except for the following 2 or 3 notable differences:

1. The display backlight is amber to match the microphone backlight (271A is green)

2. The pads on the board for digital data connections have been removed (the TM-271 can have the packet data cable added)

3. The front panel buttons are more streamlined and the function button is different from the others now.

It's basically an updated, slightly cheaper to manufacture TM-271A - a really rugged high-powered (25/60W) 2m only radio. You might be better off to find closeout pricing on a TM-271 in my opinion. I love mine.

nickcarr 09-12-2011 7:44 PM

My first Kenwood...
 
Received the TM-281a today. So far so good. The audio is exceptional compared to my V8000. I thought the Icom had pretty good audio but the Kenwood radio wins out. The front-firing speaker is rated at 5w and puts out extremely loud but clear, crisp audio. The internal design looks to have changed somewhat compared to the TM-271a. The PA section looks to have been upgraded. Overall it's a very clean design. The entire base of the radio is the usual thick die-cast metal and acts as the radio's heat sink. There is no fan. Power output is either 25 or 65 watts.

I don't own a TM-271 but this model only uses 2 screws to remove the top cover -- and the top cover is a hard plastic. It snaps tightly over the mounting screw holes and feels quite solid. (I read that the TM-271 uses 8 screws to remove the cover.)

The microphone feels great in the hand. It's a little bulkier compared to the Icom microphone but it has a quality feel -- and the PTT switch is firm and has a solid "click" response. I've heard audio reports from other Kenwood mobile users and they sound amazing. So I'm hoping this model also has that great Kenwood audio output.

Probably the best feature is the simplicity of the radio menu system. It's 100x easier to use than the Icom V8000. It's very intuitive and doesn't require more than 15 minutes of learning.

I have received good audio reports so it's working just fine. Here's an internal photo of the TM-281a. (Send a PM if you'd like a full-size image.)

http://home.comcast.net/~cnick6/tm281a.jpg

KE4NYV 09-15-2011 11:23 AM

Quote:

Originally Posted by ST-Bob (Post 1608719)
2. The pads on the board for digital data connections have been removed (the TM-271 can have the packet data cable added)

Oh man, that's a really dissapointing thing to read! That is why I loved the 271 so much. It was so easy to add packet connection and it worked really well!

KV4BL 09-16-2011 12:31 AM

Kenwood TM-281A
 
Quote:

Originally Posted by ST-Bob (Post 1608719)
According to the factory rep I talked to at HRO in Salem NH a couple weeks ago, the TM-281A is a replacement for the TM-271A and is nearly identical except for the following 2 or 3 notable differences:

1. The display backlight is amber to match the microphone backlight (271A is green)

2. The pads on the board for digital data connections have been removed (the TM-271 can have the packet data cable added)

3. The front panel buttons are more streamlined and the function button is different from the others now.

It's basically an updated, slightly cheaper to manufacture TM-271A - a really rugged high-powered (25/60W) 2m only radio. You might be better off to find closeout pricing on a TM-271 in my opinion. I love mine.



Thank You for clearing that up, ST-Bob! I had been wondering what the difference was since I saw the ad on the back of this month's QST. It sounds like they could and should have just left well enough alone. I would have thought a newer version would have at least warranted a full 200 alpha-numeric channels, a five-watt option, and maybe a fan, at the very least. I wonder if the excellent WX Alert system is still intact.

73,

Ray

ST-Bob 09-16-2011 8:13 AM

Supposedly the weather alert is still there and may actually be improved a bit. One thing I don't like about the TM-271's weather alert is that you cannot hear the weather audio on the WX channel you've entered once you turn on the WX Alert function. It mutes the audio until the 1000 Hz tone is detected. However, all you have to do is program a weather frequency into another of your 100 (or 200) channels and set SKIP on for that channel so it won't automatically stop there when scanning.

mrweather 09-16-2011 7:54 PM

Quote:

Originally Posted by KV4BL (Post 1612632)
and maybe a fan, at the very least.

On the contrary I'm glad they didn't. One less thing to fail. None of my commercial Kenwood TK-690, 790 and 890 have a fan. They use the radio chassis as a heatsink.

KE4RWS 09-29-2011 5:51 PM

271 or 281
 
I was wondering what the difference was between the 271 and 281. I guess I'm surprised Kenwood would change out and entire model for the few small changes they made. But maybe there's more to it than what I think.

I packed my TM-271 away in the box along with all my other Kenwood & Motorola radio gear and completely abandoned amateur radio operation three months ago because of three or four idiots in my area who treat other people like garbage, lie/boast about how much money they claim to earn, and completely trash other amateur operators they don't "like". I doubt I will ever get back on the air again but even if I did I wouldn't have any reason to trade-up my 271 for an amber backlight and slightly different buttons :lol:

Prior to my TM-271a I owned three Yaesu FT-2600R 2-meter mobile's, which were nearly identical to the 271, and were used for packet and APRS stations. Although I really loved the 2600's, they tended to lose their memory occasionally under certain conditions, which was a known issue for that particular model. I liked the idea of the 271 having the ability to add a data cable interface in the event I wanted to use my radio for packet (which I never did because I was still using an old TM-241 for that purpose - but I *could* if desired).

Like the 271, the 281 does look like it will be good model though :o

matt25 10-07-2011 11:52 PM

just wondering if anyone knows how to cap/mod the tm-281 ?

nickcarr 10-09-2011 2:25 AM

I think it's R768 but I haven't tried it yet.

matt25 10-09-2011 9:13 AM

so maybe i need to try this then because without this mod its just sitting in my truck not being used lol!

matt25 10-09-2011 9:23 AM

so just clip out the chip thats r768?

spd640 10-09-2011 5:59 PM

I bought a 281 but did not realize until it arrived it was a cheap made in China product

nickcarr 10-09-2011 6:12 PM

Quote:

Originally Posted by spd640 (Post 1625571)
I bought a 281 but did not realize until it arrived it was a cheap made in China product

Feel free to donate it to me. I'll test the modification. :twisted:

matt25 10-09-2011 8:08 PM

the mod works i tried it today i took out r768

nickcarr 10-10-2011 2:00 PM

Quote:

Originally Posted by matt25 (Post 1625645)
the mod works i tried it today i took out r768

Yeah it's just a resistor.

Very cool to know Matt. Thanks for testing it. I just guessed by looking at the schematics. The resistor is using the same control line as the 271A.

bertedmund67 10-11-2011 8:58 PM

Quote:

Originally Posted by matt25 (Post 1625645)
the mod works i tried it today i took out r768

Hello matt25,
Is this mod really work on the kenwood tm-281a? Do I need to reset the radio or it does automatically? Thank you.

Bert

nickcarr 10-11-2011 9:22 PM

Bert, you probably need to perform a full reset of the radio.

matt25 10-11-2011 9:33 PM

it auto reset when i powered it back on

matt25 10-11-2011 9:42 PM

nickcarr ,thanks for the help on tge mod.

I need some advice which antenna would be the best for this radio ,as far as range,or what do i look for in buying a good antenna ? These are prob stupid questions but i have no clue on antennas.

matt25 10-11-2011 9:51 PM

nickcarr ,thanks for the help on tge mod.

I need some advice which antenna would be the best for this radio ,as far as range,or what do i look for in buying a good antenna ? These are prob stupid questions but i have no clue on antennas.

bertedmund67 10-11-2011 11:00 PM

Quote:

Originally Posted by matt25 (Post 1626725)
it auto reset when i powered it back on

Hello Matt25,
Thanks very much for your prompt response. I figure this will be just like the TM-271A that auto reset itself after the mod when powers back on.

perry211 10-11-2011 11:19 PM

Kenwod TM-281 Mod. Take out the r768, Turn it back on,you will see wait while it resets it's self and then you are ready to go. If you use a solder pen put a neddle or the tip of a sharp knife with a little pressure on the resistor,touch one end of that little baby for a split second and it will pop up. Be sure you don't leave it loose in the radio! Find it. Enjoy

bertedmund67 10-11-2011 11:33 PM

Hi perry211,
I appreciate the mod and directions. This looks like I will need the needle nose pincher to do the work. Thanks very much again.

Bert

bertedmund67 10-11-2011 11:49 PM

Quote:

Originally Posted by matt25 (Post 1626735)
nickcarr ,thanks for the help on tge mod.

I need some advice which antenna would be the best for this radio ,as far as range,or what do i look for in buying a good antenna ? These are prob stupid questions but i have no clue on antennas.

It all depends on what antenna application you need, base antenna or mobile antenna. For mobile antennas and base station antennas, there are a lot out there at places like R&L Electronics or Ebay for that matter. The TM-281A has much power on it (65 watts rf output) and it will work well with quarter wave atennas such as the KR2M WORKMAN MAG MOUNT ANTENNA or the QMAG WORKMAN NMO195 + MOTHM MAGNETIC MOUNT. It will perfectly work with 5/8 wave antennas such as the JTNMO150 JETSTREAM 5/8 WAVE 2M NMO STYLE ANTENNA with any nmo mounting avaiable.

I hope this helps.

Bert

mrbobcat 10-14-2011 3:48 PM

kenwood tm281 mod
 
1 Attachment(s)
yes it will work if you take out the R768 resister. have already done this and it will work. when you take out the resister and power it back up the display will read: WAIT and then it will reset and your ready to start programming again.......

bertedmund67 10-16-2011 6:15 PM

Quote:

Originally Posted by mrbobcat (Post 1628174)
yes it will work if you take out the R768 resister. have already done this and it will work. when you take out the resister and power it back up the display will read: WAIT and then it will reset and your ready to start programming again.......

Hello mrbobcat, you are full of blessing, thank you very much for the mod. I appreciate it.

Bert

Docs43 11-23-2011 12:06 PM

resistor stuck
 
Quote:

Originally Posted by perry211 (Post 1626802)
Kenwod TM-281 Mod. Take out the r768, Turn it back on,you will see wait while it resets it's self and then you are ready to go. If you use a solder pen put a neddle or the tip of a sharp knife with a little pressure on the resistor,touch one end of that little baby for a split second and it will pop up. Be sure you don't leave it loose in the radio! Find it. Enjoy

Hello perry211,

so I'm having a little problem getting the r768 resistor out of the radio - I used the tip of a sharp knife to press on the end (tried both actually) of it and nothing.
You guys made it sound so easy and I figured it would be a "snap" but I messed with it for about 10 min. without any success.

Help please anyone, I need to mod it so I can use it!!
Feel free to email me if anyone has a picture of how it's done... "exact1er@yahoo.com"

THANKS IN ADVANCE

nickcarr 11-23-2011 7:03 PM

You have to use a little bit of force. I wouldn't use a knife though as you could potentionally scratch another component or worse yet -- a tracing.

Use a small screwdriver (watch size is best) -- they're relatively sharp and will easily poke the resistor off.

A pair of *fine-tip* tweezers can do the trick too.

Docs43 11-23-2011 7:26 PM

Thanks NC - so I have some needle-tip tweezers and I'm guessing I will actually have to pry it up (as well with tiny screwdriver) then huh? Unless it will just pull up...
Sorry to keep beating a dead horse, I just want to clarify before going back in there ;)

Docs43 11-24-2011 12:59 PM

Quote:

Originally Posted by nickcarr (Post 1648629)
You have to use a little bit of force. I wouldn't use a knife though as you could potentionally scratch another component or worse yet -- a tracing.

Use a small screwdriver (watch size is best) -- they're relatively sharp and will easily poke the resistor off.

A pair of *fine-tip* tweezers can do the trick too.


Thanks nc,
I have some of those needle-tipped tweezers and will try that route.

However, as with the small screwdriver I'm assuming you have to actually "pry" it as opposed to "poke" it?
And do I want to try and get it off from the ends of the resistor or from its sides??

Sorry to beat a dead horse, but I just want to make sure I DON'T scratch or damage anything inside...

Thanks again, Scott

Docs43 11-25-2011 7:59 PM

Quote:

Originally Posted by nickcarr (Post 1648629)
You have to use a little bit of force. I wouldn't use a knife though as you could potentionally scratch another component or worse yet -- a tracing.

Use a small screwdriver (watch size is best) -- they're relatively sharp and will easily poke the resistor off.

A pair of *fine-tip* tweezers can do the trick too.


Thanks nickcarr - hopefully this isn't a double post, but I'm just trying to clarify so as not to scratch anything in the process.

I have those tweezers, so I'm guessing it is an actual "pry/pull" method as if using the small screwdriver??
And do I want to focus on the sides not the ends of the resistor?

Thanks again - only 1 week to an important desert race that I'm chasing at so I need to be in the 150-154 freq. range!

Scott

nickcarr 11-26-2011 6:32 PM

Yes I would just pry it forcefully -- but while in control -- if that makes any sense. You don't want to jab at it repeatedly, for example. :)

108milemike 12-03-2011 12:11 AM

is this the mod for expanding the tx range on this radio

perry211 12-03-2011 5:24 PM

TM-281a Mod
 
Yes taking out that resistor will open up the tx and receive. I belive to 170 mhz. I know I have marine band freqs in mine in the 160mhz.

nickcarr 12-03-2011 9:39 PM

Quote:

Originally Posted by perry211 (Post 1654144)
Yes taking out that resistor will open up the tx and receive. I belive to 170 mhz. I know I have marine band freqs in mine in the 160mhz.

No it doesn't open up receive. It's just enables TX across the full band of the radio. The USA model is already open from 136-174Mhz.

ST-Bob 12-03-2011 9:45 PM

The TM-271 and TM-281 already receive from 136 to 174 MHz. Cutting the resistor opens up transmit to the same limits. It does not expand those limits in any way.

mjmbcls 12-20-2011 1:24 AM

Freq Split Question
 
How far down does the TM-281A go in steps? We are looking at ranges of xxx.xxx5 and I need to know if this radio will support that before I buy it. I had a Yeasu FT-3000 that gave up the ghost and it is cheaper to replace than repair. Thanks.

nickcarr 12-20-2011 3:34 PM

Quote:

Originally Posted by mjmbcls (Post 1664498)
How far down does the TM-281A go in steps? We are looking at ranges of xxx.xxx5 and I need to know if this radio will support that before I buy it. I had a Yeasu FT-3000 that gave up the ghost and it is cheaper to replace than repair. Thanks.

So, your logic is that a newer radio won't support an older radio's steppings? :confused:


FT-3000:
Steps: 5/10/12.5/15/20/25/50 kHz

TM-281:
Steps: 2.5/5/6.25/10/12.5/15/20/25/30/50/100 kHz

PS. The TM-281 does not have a wideband receive function like your FT-3000. The TM-281 is 136-174 Mhz only.

108milemike 12-22-2011 12:04 AM

Just got the TM-281 very satisfied after doing the mod and opening up the tx frequency range

pjtnascar 12-22-2011 8:01 AM

I got one of these as an early Christmas present from my wife. It was a good deal at HRO over Thanksgiving week. So far, I am very satisfied with the quality and performance. Not too sure if I will "mod" it for the frequencies.

perry211 12-27-2011 12:46 AM

Kenwood TM-281 Mod Update
 
Happy New Year, The mod information that I posted b-4 must have been read too fast. I read someone having problems getting the resistor (R768) off of the board. I did say use a solder pen, thats like a small soldering gun or iron. With the tip of a knife put a little pressure under the edge and for A SPLIT SECOND touch one side and it will pop up. Like I said b-4 make sure you know where it ends up. You don't want it loose in the radio and short it out. The narrow band works great. Our local Fire&Rescue just went narrow band on VHF. I wish I knew how to turn down the high power. I use 25 all of the time and works well, but if I could turn down the high down to 50 watts, It would be great and the radio would last much longer.
Just for the info, I use a base loaded 5/8 wave nmo mount on the trunk and it does great. Have fun and let's be kind to each other. A dumb question is the one that you didn't ask. :)

KE4RWS 12-28-2011 3:20 AM

TM-281 Tuning Resolution as little as 2.5 KHz
 
Quote:

Originally Posted by mjmbcls (Post 1664498)
How far down does the TM-281A go in steps? We are looking at ranges of xxx.xxx5 and I need to know if this radio will support that before I buy it. I had a Yeasu FT-3000 that gave up the ghost and it is cheaper to replace than repair. Thanks.

It looks like you simply want to know if the TM-281 has frequency resolution down to at least 5 KHz, which it does. As listed by the former reply, it actually has slightly better resolution and can tune in as little as 2.5 KHz steps. But you can be assured most any amateur radio you buy that was made in the last 20 years has 5 KHz tuning resolution.

If I didn't already own the prior model (TM-271) I would definitely buy the 281, as it certainly appears to be a winner so far. If it's anything like the TM-271 (which it is) I know people will love it though :)

W9BU 12-28-2011 3:40 AM

Quote:

Originally Posted by KE4RWS (Post 1669726)
It looks like you simply want to know if the TM-281 has frequency resolution down to at least 5 KHz, which it does. As listed by the former reply, it actually has slightly better resolution and can tune in as little as 2.5 KHz steps.

No, he asked if it would tune in 0.5 kHz steps, which it doesn't do.

The frequency step sizes are listed on page 56 of the owner's manual: 2.5 kHz, 5 kHz, 6.25 kHz, 10 kHz, 12.5 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 50 kHz, 100 kHz.

While I'm taking up a message slot, let me remind readers of this thread that the TM-281 is manufactured and marketed for use in the amateur radio service. It is not FCC certified for transmitting in any other radio service.

KE4RWS 12-28-2011 4:04 AM

Good Point
 
Quote:

Originally Posted by W9RXR (Post 1669731)
No, he asked if it would tune in 0.5 kHz steps, which it doesn't do.

The frequency step sizes are listed on page 56 of the owner's manual: 2.5 kHz, 5 kHz, 6.25 kHz, 10 kHz, 12.5 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 50 kHz, 100 kHz.

While I'm taking up a message slot, let me remind readers of this thread that the TM-281 is manufactured and marketed for use in the amateur radio service. It is not FCC certified for transmitting in any other radio service.

Ahhh, I see. Not sure why you would require discrimination down to 0.5 KHz, even for narrow-band FM. But I admit I'm not as on top of things as I used to be. And yes, it's always good to point out the fact the Kenwood TM-281 was designed and is type-accepted for use as a 2-meter amateur radio. Although radio's of this kind seem to be favored by some for Fire, EMS, Business or Personal use, it is in fact illegal to use them for anything other than licensed amateur radio operation (I can feel some eyes rolling out there). Clearly there are those who will do what they want, regardless.

For those that don't know this, you can legally use most commercial radio's in the amateur bands but you cannot use an amateur radio in the commercial bands or for any commercial purpose - at least in the USA. There are a few exceptions though, such as life-threatening emergencies, etc.

Hope everyone had a great Christmas and good fortune in the upcoming new year :)

nickcarr 12-28-2011 12:47 PM

Quote:

Originally Posted by W9RXR (Post 1669731)
No, he asked if it would tune in 0.5 kHz steps, which it doesn't do.

I don't believe that .5khz steps was his question as the FT-3000 does not do that -- unless he modified it. I believe he was making sure it supported the 12.5khz steppings (see his frequency example.)

W9BU 12-28-2011 1:43 PM

Quote:

Originally Posted by nickcarr (Post 1669897)
I believe he was making sure it supported the 12.5khz steppings (see his frequency example.)

12.5 kHz tuning steps are not a complete solution for tuning narrowband signals on VHF public safety or industrial/business pools. The raster being used to assign these new channels is 7.5 kHz, not 12.5 kHz.

Let's take a range of channels from the public safety pool ( 47 CFR 90.20 (c)(3) ):

Code:

1--154.1000
2--154.1075
3--154.1150
4--154.1225
5--154.1300
6--154.1375
7--154.1450
8--154.1525
9--154.1600

If your radio tunes in 5 kHz steps (0.005 MHz), you will only hit on channels 1, 3, 5, 7, and 9 because your tuning steps are 154.1000, 154.1050, 154.1100, 154.1150, etc.

If your radio tunes in 12.5 kHz steps (0.0125 MHz), you will only hit channels 1 and 6 because your tuning steps are 154.1000, 154.1125, 154.1250, 154.1375, etc.

If your radio tunes in 7.5 kHz steps (0.0075 MHz), you will hit all the channels. Your tuning steps are 154.1000, 154.1075, 154.1150, etc.

But, the TM-281 tunes in 2.5 kHz steps (0.0025 MHz). You will hit all the narrowband channels, plus a lot more in between. Your tuning steps are 154.1000, 154.1025, 154.1050, 154.1075, 154.1100, etc.


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