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TM-221A Review by KT2B | Radioaficion Ham Radio

TM-221A Review by KT2B

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Kenwood TM-221A 2 Meter FM Transceiver

Manufactured: 1987 (Discontinued)

Kenwood TM-221A 2 Meter FM Transceiver

As user-friendly as the TR-7400A— with more power out in a smaller box!

I had so much fun using the TM-221A in the car that it was hard to take time to write it up! This is one of the more user-friendly two meter transceivers on the market today the beauty of its design is the overall simplicity. This is very welcome in this day of bells, whistles, foghorns, CRTs, readouts and 5,000 plus knobs and whatever else one finds on "full-featured" rigs.

Worthy Replacement

For many years, my tried and tested two meter radio was also a Kenwood of 1978 vintage. Many readers

will recall the legendary TR-7400A that set the two meter crowd abuzz with full 800 channel synthesis, a super-selective receiver, and more than 25 watts output. In that time of rock-bound ngs, the design was truly state-of-the-art and user-friendly—controls were kept to a minimum, reflecting the demands of mobile operation. Since then, numerous two meter mobile transceivers appeared on the market, flourished briefly, and disappeared. All sorts of crazy options such as remote control heads, continuously adjustable output power and umpteen-million scanning speeds had their day. Meanwhile, the 7400A performed yeoman service in four different cars without one day of downtime.

And yet.. J found myself thinking how nice it would be to have something smaller under the dash that didn't use power-hungry TTL technology. . that didn't have its display wash out in bright sunlight . and thai would allow storage of a few memories, say just 10. About that time, the ads for the TM-221 caught my eye. Ten years to the month that I bought my 7400A. I departed a hamfest with a brand new TM-221 under my arm.

The photo of the TM-221 A shows the simple control layout. But, at over 40 watts, there's plenty of punch in that box. . .more than enough for 90% of all mobile FM needs-Front panel switches and knobs adjust volume, squelch, power on, HI/LO power, and dial tuning. Additional pushbuttons select either memories or the VFQ, input memory data, and allow high-speed tuning with the main knob in MHz steps

Five more pushbuttons are located under the frequency display, tucked out of the way until needed. They are (in order): shift (for repeater offsets), rev (to listen on repeater inputs), scan, ctcss (selects receiver subtone frequency), and tone (selects transmitted subtone frequency). That's it! No other buttons to push, dials to turn, switches to set. .. a piece of cake.

One handy feature of the TM-221 A is automatic repeater offset selection, based on the current ARRL two meter band plan. As you tune up from 144 MHz. the "correct" repeater offset automatically kicks in. depending on your position in the band. For example, simplex operation is selected from 144 to 145.10 MHz. From 145.10 to 145.5, the transmitted signal will offset -600 kHz from the receiver frequency. Above 145.50, simplex operation is again selected to 146.00, where an offset of +600 kHz kicks in. The procedure is repeated for all segments through 147.99 MHz.

In everyday use, you'll probably select favorite repeater or simplex frequencies that are stored in memory positions 0-9. Each channel stores not only the frequency, but offset, subtone and tone squelch information as well. In virtually all cases. 10 memories are more than adequate for normal operation. The TM-221 A. however, also has 4 additional positions that are special function memory channels. Labeled A-D, these store upper and lower band limits for scan functions as well as non-conventional repeater offsets.

Kenwood kept the scanning functions simple as well. There are only two modes, (all that are usually necessary): Programmable Band Scan, where the upper and lower limits of the scan are entered into memories A and B, and Memory Channel Scan. One scan feature gaining popularity is channel lock out in a memory channel scan. Kenwood includes it here.

The supplied microphone is the M048 TouchTone microphone, that looks like a bfack version of the MC-46. One nice variation from the older MC-46 is that the PTT line must be keyed in order to transmit tones. On older microphones, the keypad was always active, and merely squeezing the microphone tightly often resulted in very interesting transmissions.

review Kenwood TM-221A 2 Meter FM Transceiver

Performance

I spent almost three hours installing the radio in a 1987 Toyota Corolla LE in an attempt to create a low-profile and safe installation. The final resting place is inside a

detachable change tray just behind the shift lever. Bear in mind my performance evaluation is based on user observations, not on bench tests.

In every case, the TM-221A's receiver was as sensitive as the older TR-7400A. Selectivity was at least on a par with the '7400, The RF amplifier is a 3SK184 GaAsFET, with a bandpass filter in front and a 3-sectton Hi-Q bandpass filter following (essentially a helical resonator circuit). The output drives another 3SK184 acting as a mixer. Two stages of crystal filtering are used at the first IF (10.695 MHz), and another monolithic filter is used at 455 kHz.

What makes it all work is the Hi-Q filter and bandpass filter around the first RF stage, since most of the "garbage," such as IMD products, issues from there. Suppressing out-of-band signals to limit compression of the front end goes a long way towards helping you hear that distant repeater! This is a lesson learned the hard way by Kenwood and other manufacturers based in Asia, where RF pollution in heavily-populated areas can be nothing short of astonishing.

The transmitter lineup is fairly conventional It uses an M57726 hybrid power module with four poles of bandpass and low-pass filtering. Full ALC protection is offered and the low-power output is continuously adjustable from 0-30 watts. High power out claim is 45 watts; I found it at closer to 40. This is largely a function of (1) How long the DC leads to the battery and (2) How heavy a cable is used. The DC leads supplied with the TM-221 A are a bit light for nearly 90 watts of DC input, so you may wish to use heavier wire for long runs

In mobile use. the TM-221A is a piece of cake. The amber backlit LCD display should be mandated for EVERY piece of electronic gear installed in a car. It is equally readable at night or in bright sunlight, unlike the conventional green displays. The display indicates the frequency (or memory channel) in use. selected offset, tone/CTCSS enabled, scan mode, signal strength and power output. Simple enough!

QSY is fast, and even easier when selecting memory channels. One obvious drawback of such a small package is the size of the control buttons! You must be careful not to brush keys when reaching over to make a channel change. An example is the position of the hi/lo power switch adjacent to the power on switch. I invariably punch up low power when turning the radio on.

Conclusion

I highly recommend the TM-221 A for both first-time buyers and seasoned 2 meter FM veterans. It is easy to use, offers just the right amount of features and fits nicely inside today's automobiles with limited dash space Receiver performance is superior in high RF environments (a selling point I cannot stress enough) and the output power is just right for all kinds of mobile work, Besides. . .it looks great under the dashboard!

Pete Putman KT2B - 73 Amateur Radio -

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