FT-2900R vs. TM-281A

[Project25_MASTR]

Probably not really needed on the amateur bands, but I suspect as time goes on it'll be needed. As more modern analog commercial gear gets retired, we'll probably start seeing a few narrow band FM repeaters. Probably a ways off though.

If you plan on using it as a receiver outside the amateur bands, it might be something you'll want.

The FT-2900 will narrowband (mine would). Like any mobile radio these aren't built for more than about 25% duty at full power (most commercial rigs are only speced at 10-15% duty). Did I ever melt down my 2900? No but it did get hot enough on several occasions, according to the internal temperature probe, that it concerned me. Somewhere around 175 degrees F is as hot as I ever let mine get (once it was that hot just turning it on). I found that turning the defroster on (mounted on top of the dash) really helped with moving heat away from the radio.

I rarely took mine above the 35W setting, usually ran with a 1/4 wave antenna. Later upgraded to a much smaller Motorola PM400 before upgrading to my new radio...but I prefer commerical gear (even more for FM base as you rarely need to add new channels).

These were taken on the same day when I got into the vehicle.

The Motorola PM400:

The Motorola in it's new (temporary) home:

The replacement for the PM400:

 

[jk77]

I reread all the eham reviews on these two radios.

I like the TM-281A and I agree that it probably is the better radio. The problem is that it lacks a 5 or 10 watt low power setting and that might end up being the deal breaker for me. The Yaesu is more in line with my operating style. I can hit my county repeater and the repeaters in the surrounding counties with a 5 watt HT so the 5 and 10 watt settings on the Yaesu are good for me. It's nice to have 75 watts to see how far I can reach, but no one ever accused me of being long winded on the air so I don't think it would overheat in the short time that my QSOs usually last. Most of my use will be low power.

On the other hand, I worry about efficiency of the Yaesu. It's dumping a large amount of power as heat. I have read that the Kenwood (as all radios without fans) gets hot, but I have not read multiple reviews on eham where people said that the radio shuts down due to heat as I have read about the Yaesu.

Honestly, I am at the point of flipping a coin.

 

[Project25_MASTR]

The Yaesu is actually more efficient.


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[jk77]

I'm getting ready to pull the trigger on this tomorrow. I am most likely going with the Yaesu, but who knows, that could change overnight. I will update this thread once I've placed the order.

 

[WyoDuner]

I don't know why you are so worried about a low power setting. It's perfectly OK to hit a repeater with 25 watts when 5 watts is all that's needed. It's not going to hurt anything. The ONLY time I can think this would matter is if you were running some portable mode off of battery power.

Yes, I understand the FCC regs stating that minimum necessary power should be used to make a contact. I'm sure this wouldn't violate the spirit of that law. I think the TM-281 is a great radio with good audio and tough build. That's why I bought mine.

 

[jk77]

It's not just the 25 watt low power setting of the Kenwood that hangs me up. The Yaesu has a few more "bells and whistles" that I like than the Kenwood. It just seems to me like Yaesu provides more "bang for the buck" than other manufacturers. However, it seems to be the consensus in this thread that the Kenwood is the better choice and I cannot ignore that either.

 

[Project25_MASTR]

I don't know why you are so worried about a low power setting. It's perfectly OK to hit a repeater with 25 watts when 5 watts is all that's needed. It's not going to hurt anything. The ONLY time I can think this would matter is if you were running some portable mode off of battery power.

Yes, I understand the FCC regs stating that minimum necessary power should be used to make a contact. I'm sure this wouldn't violate the spirit of that law. I think the TM-281 is a great radio with good audio and tough build. That's why I bought mine.

That probably also depends on equipment. Kenwood has been manufacturing 50/25 and 25/10 radios for years. 25 is a good low power number.

My low power number on my truck radio is 50W.


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[cmdrwill]

One known problem with FT2 series radios is the transmitter is very inefficient a low power levels below 30 watts, They over heat and blow out the power module.

Reducing the transmitter output power below half power causes the transmitter to run out of Class C. The 'finals' get really HOT..

 

[Project25_MASTR]

One known problem with FT2 series radios is the transmitter is very inefficient a low power levels below 30 watts, They over heat and blow out the power module.

Reducing the transmitter output power below half power causes the transmitter to run out of Class C. The 'finals' get really HOT..

You can actually confirm that off of Yaesu's own specs for the radio. At full power it has an efficiency greater than the Kenwood (it's 4W of heat production difference between the two radios at full power). However, the effectually quickly drops as the power gets backed down.

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[jk77]

You can actually confirm that off of Yaesu's own specs for the radio. At full power it has an efficiency greater than the Kenwood (it's 4W of heat production difference between the two radios at full power). However, the effectually quickly drops as the power gets backed down.

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I did the math and I agree that the Yaesu becomes less efficient as the TX power goes down.

I have no idea about the Kenwood because they don't provide specs for their 25 watt setting.

 

[AK9R]

According to the ARRL test report on the TM-281A, the radio draws:

Receive: 420 mA (max vol, max lights, no signal), 203 mA (standby, no lights)
Transmit: 9.55 A (high, 63 watts output), 5.67 A (low, 24 watts) at 13.8 V dc.

I was unable to download the FT-2900R test report. Maybe I'll be more successful later.

 

[Project25_MASTR]

According to the ARRL test report on the TM-281A, the radio draws:

Receive: 420 mA (max vol, max lights, no signal), 203 mA (standby, no lights)
Transmit: 9.55 A (high, 63 watts output), 5.67 A (low, 24 watts) at 13.8 V dc.

I was unable to download the FT-2900R test report. Maybe I'll be more successful later.

That's a significant difference from what Kenwood states. Interesting.

I pulled up a 47% efficiency at high and a 30% at low on the Kenwood. Would be nice to see how it compares to their testing on the Yaesu.

 

[jk77]

Thanks for the info on the TM-281A. I have the measured data for the FT-2900R:

@ 13.8 V DC:

Transmit: 14 A, 8.9A, 5.5A, 4.3A, 3.8A at 71.4 W, 27.4 W, 7.7 W, 3.8 W respectively
Receive: 760 mA (max volume, max lights, no signal); 160 mA (standby)

The sensitivity of the FT-2900R was measured to be at 12 db SINAD 0.2 microvolts

Do you have the measured sensitivity of the TM-281A?

 

[Blackswan73]

I am running the 281a in a base configuration running into a ED Fong PVC antenna. I love it! I bought it because it is mil-spec, and based on their commercial radios. The front firing speaker is especially suited to a base environment. I have never used the 65 watt setting. I only use the 25 watt setting. All my reception reports are glowing. I can hit a repeater 20 miles away during a rainstorm with full quieting. A very impressive rig. I got mine new in the box from HRO for $142 shipped. Used one of the 50 amp strip light power supplies from eBay for $25, and $40 for Ed Fong's highly rated antenna. A complete 2m base station for just $207

 

[AK9R]

Do you have the measured sensitivity of the TM-281A?

From the ARRL test report, it's 0.14 μV for 12 dB SINAD in wide mode at 146 MHz.

In addition to sensitivity, I also believe that the adjacent channel rejection is important in an FM receiver. For the TM-281, it's 79 dB at 20 kHz offset.

 

[AK9R]

Based on the current draw vs. power output data that jk77 and myself have posted, I plotted the data in an Excel graph and had Excel draw in logarithmic trend lines for the plotted points.

See attached. Horizontal axis is power output, vertical axis is current draw. Based on this data, it would seem that the TM-281 is a more efficient transmitter...unless I am misinterpreting something. Of course, a curve fit is challenging with so few data points as evidenced from the Kenwood's curve indicating about 5 watts output with 0 current draw.

 

[jk77]

Thank you W9BU. That's the conclusion that I sketched out in my mind but thanks for actually plotting it out to confirm what I was thinking. Also, thanks for providing the sensitivity data.

Based on all this, it does indeed appear that the TM-281A is the better radio. I'm especially impressed with the sensitivity measurement which is important to me because I live in a rural area with a lot of weak signals, if I want to go simplex.

I'm not quite sure how to read the adjacent channel rejection data. For the Yaesu, it's 67 db at 20 Khz offset.

 

[jk77]

I have a question. Let's say the sensitivities of the FT-2900R and the TM-281A are 0.20 microvolts and 0.14 microvolts respectively as were measured by the ARRL. Does this really make a difference in practice? Would it be noticeable?

 

[one4gimp]

You get 10 more watts out of the 2900 it makes a little difference.
I've used the 2900 for many years now the menu is easy to use and it's a workhorse
My only regret is that I didn't spend a few more bucks and get the duel band.

 

[jk77]

I ordered the Kenwood TM-281A.

My heart was with the Yaesu FT-2900, but numbers don't lie. You've got to believe that Yaesu knew that their radio was inefficient and instead of redesigning the transceiver, they slapped a bigger heat sink on it. That's why it weighs nearly twice as much as the Kenwood. I noticed that Yaesu's dual band radios are more efficient. I also noticed that there are numerous reviews on eham that say the FT-2900 overheats and few, if any, said that the Kenwood overheats. It was also clear that few, if any, of the reviewers of the Kenwood stated that their radios broke or did not work but there were several such reviews about the Yaesu. So I am left to conclude that the Kenwood TM-281A is more efficient and seems to be more reliable. Of course, I am aware that usually very happy people or very disappointed people are motivated to write reviews.

Thanks to all you good folks for your advice and help. You really helped me make this decision.