Kenwood TS-711A 144-MHz Multimode Transceiver
Manufactured: Japan, 1984 (Discontinued)
For those readers who've been wondering if they perhaps missed a product review of the Kenwood TS-711A 2-meter multimode transceiver in some past issue of 73 relax You didn't miss it. The TS-711A has been on the market for a few years, but somehow got overlooked in the accumulation of items that are selected for review each year by the 73 staff. Why. we even managed to take a look at the companion 70-cm unit, the TS-811 A, last June' Finally, at long last, a TS-711A showed up at the offices of WGE a few weeks ago, courtesy of Kenwood, so I seized the opportunity to put it through its paces.
The TS-711A comes in a package about the size of Kenwood's popular TS-430/440 series HF transceivers, ostensibly to create a matched iayout along with the TS-611A for a complete HFA/HF/UHF station. The final is rated at 25 Watts output (adjustable), and band coverage is from 142-148 MHz to allow MARS and CAP operations. The usual bells and whistles are included, such as programmable memories and scanning, as well as some useful controls such as i-f shift and RIT.
If you read the TS-811A write-up, you'll notice a close resemblance to the TS-711A in layout, performance, and size. Both radios are equipped with Kenwood's Digital Code Squelch (DCS) system, which I did not get a chance to tinker with. This system will not permit the squelch to open on any signal unless the proper code" is present, functioning in the same manner as Private Line™ (PL), but
on a more sophisticated level. In addition, the system can be set up to locate an unused channel and then send another TS-711A equipped with the correct code to that channel automatically.
The modes of operation included are CW, USB, LSB, and FM( which are switch-selectable from the front paneL An audible CW character signals when the desired mode is selected- Also present is a button marked auto, which preselects the mode according to a band plan. You may recall that I found this control somewhat useless on the TS-811A due to the different 70-cm band plan employed in Japan. However, the Japanese 2m band plan is very similiar to that of the U.S., with CW switched in from 144 000-144.099 MHzT USB from 144.100-144,499 MHz, FM from 144.500-145.799 MHz, USB from 145.800-145,999 MHz, and FM again for the remainder of the band.
The rest of the left side controls are al for priority channel function; scan, m in for loading memories; lock and rev, which lock the main dial and select reverse of any offset present, respectively: and chs, which scans memory channels. Tone frequencies for PL can be selected from a switch and the front tuning dial. A 20-dB attenuator is provided tor strong signals, and a speech processor (nonadjustable) can also be switched in. In addition to the i-f shift and RIT functions, the right side includes controls for squelch, microphone gain, rf power out, af/rf gain, 1-MHz up/downr and noise blanker (nonadjustable).
The TS-711A is equipped with two vfo's and a memory bank that can hold up to 40 memories with offsets, subtones. and mode for each channel. Main dial tuning occurs in a range of steps, depending on mode. For example, in FM mode you can either select 10Hz or 5-kHz steps, while in SSB or CW the choice is—surprise!—10 Hz or 5 kHz. The difference is the button marked ch q. When it is engaged, you'll hear a loud "kerchunk" as a solenoid kicks in and the tuning knob "click-steps" in 5-kHz increments, very useful on FM. When it isn't engaged, the tuning is silky smooth. And if 10 Hz isn't fast enough, engage the step button and cruise along at 100 kHz per revolution.
As noted before, microphone gam Is adjustable from the front panel. Following past Kenwood practice, this applies only in SSB mode, Mike gain is preset on FM and is adjustable only by removing the cover. On other multimode transceivers, such as the IC-275A reviewed last month, the mike gain works in every mode, which I find handy when accessing repeaters with different audio frequency response curves. You know the types—everyone says your audio is too hot, or too lowT etc.
The proc (processor) control is of questionable value on 144 MHz. and I could do without it, especially since the level of compression is not adjustable On the other hand, RIT is very useful as I have pointed out in the past, especially when you're trying to copy weak CW signals through the noise. And the i-f shift pulls its weight during contests! Its function is very similar to a passband tuning control, shifting the passband of the M filter to either side of the desired signal.
Let's now take a look at the schematic. The front end employs a 3SK129 GaAsFET driving a 3SK122 MOSFET mixert and the combination works reasonably well, as the performance data in Table 1 shows. Selectivity is accomplished by the use of two helical preselectors—a two-pole unit ahead of the GaAsFET and a three-pole unit following. This scheme does improve selectivity as shown in the performance data and is the right way to go at VHF and UHF frequencies, especially with broadbanded rf receive amplifier stages On transmit, an M57727 power module is employed with both temperature and swr protection. ALC control is also afforded, and the ALC level can be displayed via the front-panel meter.
The TS-711A has its own seff-contained power supply, and it gets fairly warm with use but never hot. A cooling fan will engage after lengthy transmissions—usually on FM—and disengage when the temperature drops below a certain point. Provision has been made to connect an external supply if you wish to go portable. Other connections can be made for your CW key. headphones, external speaker, and an external standby switch—presumably for a footswitch when in CW mode. There is no front-panel TX/RX switch; I find this a bit of a nuisance, especially when doing performance tests or tuning up amplifiers.
Kenwood has provided one accessory jack for interfacing with RTTY for AFSK operation
(ACC1), and the connections are quite clearly spelled out in the manual. Kenwood also identifies an ACC2 jack in the owner's manual which is intended for a computer interlace. However, the knockout on my unit where ACC2 would go was filled by a plastic insert leading me to conclude that you must buy the optional interface to obtain and use this connection. Either that, or the interface isn't available yel in the U.S. (A third possibility is thai this particular unit just didn't have the jack installed!)
In actual use, the TS-711A is quite easy to figure out after you remove it from the box. The human engineering is quite good, although some of the less frequently used bells and whistles could have been pushed off to the side. As in all Kenwood transceivers, provision has been made for dial torque adjustment, but the factory setting was comfortable from the start.
I used the TS-711A with my Microwave Modules MML-220S power amplifier and a Cushcraft 32-19 Boomer, and right away noticed one BIG problem; no external amplifier keying jack. ICOM has been offering these for years on their 2-meter multimodes—so. how about it, Kenwood? I personally can't abide by rf VOX keying and prefer a hard-switched setup. It was no problem switching the Kenwood into transmit through its standby terminal, but I had to use an external sequencer to key both devices.
Receiver sensitivity is adequate, although not on par with many state-of-the-art transvert-
ers and the aforementioned IC-275A. On more than one occasion, I had to switch in an external GaAsFET preamp to pull out a weak SSB signal, especially during rapid fading. An outboard preamp would probably be a good idea for very-weak-signal work, but I couldn't recommend anything with more than about 1012 dB of gain. A preamp exceeding that number will cause the 711 A's front end to crunch up on strong signals (as will be shown in the test results).
Selectivity is very good, and I can't imagine too many situations on SSB/CW where you won't be able to pull out some signal from the QRM by using the RIT and i-f shift controls, Incidentally, there are no filter options for the TS-711 A—what you buy is what you get. It would have been nice to have some sort of CW filter option at least.
Received audio reports were good, although I noticed a similarity with the TS-430S series HF radios, and that was that most operators preferred the audio of the MC-42 handheld microphone over the MC-507MC-60 base-station mikes. Reports ranged from "too much bass" to "mushy sounding." The MC-42 was clearly the winner here.
I really wish Kenwood would supply a microphone with their transceivers. Can you imagine how someone feels when they hp into the box. pull out a brand new TS-711A. and discover there's no microphone included? For Pete's sake, mark up the price a few dollars if you have to, but at least include the hand-held microphone!
Now take a look at Table 1. The receiver in the TS-711A got a pretty thorough going-over, as I was looking for dynamic range, compression data, and MDS. The transmitter was checked for power output, output adjustment, and displayed frequency versus measured frequency. The figures are about what I expected, and the 1 -dB compression point of -1 dBm is about average for a GaAsFET.
Using an external preamp with the TS-711A might result in IMD products and spurious signals when strong local signals are present, making it very difficult to work weaker signals on nearby frequencies. The dynamic range is acceptable, again considering the use of a GaAsFET in the front end Selectivity is fairly good. The output power level is sufficient to drive all of the 2-meter amplifiers currently on the market, and the low-power setting is handy for those amateurs using tetrode-type grid-driven power tubes, such as the 4CX250B. I should also mention that operation of the power output control is fairly linear.
If you would like to add 2 meters to your present station with an all-in-one transceiver, you should consider the TS-711 A, In general, it performs as well as any other 2-meter multi-mode on the market (with few exceptions), is easy to set up and use, and does offer some nice features in addition to the usual complement of bells and whistles
- 1987 Peter H. Putman KT2B - 73 Amateur Radio