Circuit Mic Kenwood

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Paul Crupp KA1LR 73 Magazine Staff

The Kenwood TR-7730 Transceiver

Time was, if you had a small car and wanted to put a synthesized two-meter rig in it, you either cultivated a sadistic disregard for your passenger's knees or got yourself one of the two rigs on the market with a compact separate control head, The new Kenwood TR-7730 ;s part of a trend that will change all that. Measuring a mere 2" high, 5.75** wide, and 7 75" deep, it will fit in the smallest of cars without usurping precious legroom and is even compact enough to fit in the extra radio slot located in the console of many newer cars One might suppose that a great deal was sacrificed to cram everything into such a small pac kage. Surprisingly, this is not the case. Without further ado, let's take a tour of what the TR-7730 has to offer.

The Features

Starting in the upper left-hand corner of the front panel, we find the memory channel selector and two square push-buttons —one marked "M" and the other marked "MR". The "M" button loads the frequency shown on the digital display into one of the five memories This frequency can later be recalled by pressing the "MR" button and choosing the desired position on the rotary selector. On memories 1-4, the transmitter offset is set with the switch on the far right-hand side of the front panel. Memory 5 programs both transmit and receive frequencies, allowing access to repeaters using non-standard splits.

Beneath the memory controls are the combination power switch and volume control and the squelch. Directly to the right of these is the main tuning knob, which steps through the band in a similar manner to the knob on the TR-9000.

Just to the right of the main tuning knob is a switch which selects either 5- or 10-kHz steps with each click of the main tuning knob, a high/low power selector, and an on/off switch for a user-installed CTCSS encoder. Directly above these are three switches as-

sociated with the scanning circuitry. Pressing the "Scan" switch starts the j' ■ m ' 'Ji ' 1 " l.

7730 scanning up the band. It will stop on any signal that breaks the squelch and resume scanning when the signal drops If you hold down the scan button continuously, the rig scans at twice the normai rate. If you wish to remain on a frequency, press the PTT switch on the mike or the "Hold" button on the front panel. Pressing the "MS" switch scans the five frequencies programmed into

Kenwood 9000
rhe Kenwood TR-7730.

Top view of the Kenwood TR-7730.

Kenwood 7730

Bottom view of the Kenwood TR-7730,

Top view of the Kenwood TR-7730.

Bottom view of the Kenwood TR-7730, the memories. The scan and hold switches work in both the band- and memory scanning modes. The up/down switches on the microphone function only in the band-scanning mode.

All displays are of the LED variety There is a bargraph S/rf-meter simifiar to that on the TR-7800, although the dispfay on the TR-7730 seems to be less prone to flickering. Above this are three l_LDs. The one on the far right lights to indicate that a repeater offset has been selected, the middle when the unit is transmitting! and the left when a signal that breaks the squelch is present. To the left of this is the main frequency display.

Most of the rear panel is dedicated to a heat sink for the final amplifier In a cluster on the left side are the antenna connector power cable, speaker jackr and a three-prong iack for a memory backup power supply.

Big Rig Performance

Kenwood wisely avoided compromise in the rf stages in their down-sized rig. The transmitter and receiver stages are strikingly similar to those in the TR-7800, Space was saved by shrinking the control circuitry, replacing some discrete components in the audio chain with ICs, and simplifying the fmal stage Specifications are virtually identical for the two rigs. Sensitivity is rated at better than ,5 uV for 30 dB S/N. Selectivity ts spec'd at 12 kHz at 6 dB down and 25 kHz at the -60-dli point In the highpower mode, our unit exceeded its rated 25 Watts at all frequencies between 144 and 148 MHz. Output in the low-power position is continuously adjustable, making it easy to match the rig to amplifiers requiring only 10 Watts or so of drive As with most commercial ngs, the deviation level was set slightly high for the close-talking most hams use to improve signal to noise in a car, but was easily readjusted,

In actual use, the TR-7730 is a champ. II worked perfectly the moment it came out of the box. Both transmit and receive audio have the usual Kenwood characterise tics —high fidelity with no sacrifice of intelligibility The squeich is extremely sensitive and seems to latch up resolutely, without the mushiness encountered on many rigs. The controls are thoughtfully shaped and located—most of us should have no trouble putting the TR-7730 through its paces in a dark moving vehicle. I he bar-graph S-meterr which first struck me as being a gimmick of questionable utility, turned out to be extremely useful it's a lot easier to read at a glance than a D'Arsonvai movement.

The only thing more enjoyable than using this rig is deciding where to install it! it's so small that the possibilities are almost endless After considerable debate, 1 removed the AM radio from mv Dodge Colt's dashboard and cut away the plastic faceplate with a fine-toothed saw and a couple of files. I didn't know whether or not the rig would actually fit until the faceplate was completely cut away Behind the dash 1 found two metal braces, offering plenty of support. The fit is so tight that I didn't have to screw the rig down I connected the remote speaker jack to the in-dash speakers supplied with the car.

Not for the squeamish, an in-dash or consote installation can nevertheless be extremely satisfying. 1 used to enjoy having my car look like a mobile NASA control center with rigs hanging everywhere, but I get even more pleasure from the clean setup I now have. It you decide to try an in-dash installation, |ust be sure that there is plenty of air circulation available. Inadequate cooling can kill a rig.

f used the Kenwood MC-46 DTMF mike, and I must admit I have a love/ hate relationship with it. On the plus side, it has all 16

tones, which is useful, and the audio quality of the condensor mike element is unquestionably superior to the mike packed with ihe rig On the negative side of the ledger, the mike is small! It took me a coupie of days to learn how to handles it without inadvertent-K pushing one oi the buttons on the pad. The hangup hook resembles tho^e on other microphones I own, but it is slightly smaller, so it won't stay put in either of the mike holders in my car The small size no longer bothers me, but I am still looking for something to hang the mike on when I am not using it. My advice is to check out the mike careful ly before buying, and if it seems too small to cope with, pick up a Kenwood MC-45t You'll need to rewire the mike connector, but the 45 is a solid, full-si/ed microphone, sure to please the most ham-handed ham! The MC46 has some nice features, though, and is probably well worth the effort required to get used to it.

Nothing is perfect, oi course, and the TR-7730 is no exception I found three relatively minor things I would like to see improved, f irst, the main frequency display is anything but easy to read No doubt the location I chose for the rig

Continued on oaqe 196

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