The Kenwood TR-7730 Transceiver
Time was, if you had a smal I tar 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 is 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 package. Surprisingly, this is not the case. Without further ado, let’s take a tour of what the TR-7730 has to offer.
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- or10-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 associated with the scanning circuitry. Pressing the “Scan” switch starts the 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 normal 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 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 bar-graph S/rf-meter similiar to that on the TR-7800, although the display on the TR-7730 seems to be less prone to flickering. Above this are three LEDs 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 hnal amplifier In a cluster on the left side are the antenna connector, power cable, speaker jack, and a three-prong jack 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 final stage. Specifications are virtually identical for the two rigs. Sensitivity is rated at better than ,5 uV for 30 dB S/N. Selectivity is spec’d at 12 kHz at 6 dB down and 25 kHz at the — 60-dB point. In the high-power mode, our unit exceeded its rated 25 Watts at all frequencies between 144 and 14« 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 rigs, 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 It worked perfectly the moment it came out of the box. Both transmit and receive audio have the usual Kenwood characteristics — high fidelity with no sacrifice of intelligibility. The squelch is extremely sensitive and seems to latch up resolutely, without the mushmess 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. The bar-graph S-meter, 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’Arsonval 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, I removed the AM radio from my 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 I 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 console instal lation can nevertheless be extremely satisfying I 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. If you decide to try an in-dash installation, just be sure that there is plenty of air circulation available. Inadequate cooling can kill a rig.
I 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 the ng On the negative side of the ledger, the mike is small! It took me a couple of days to learn how to han dies it without inadvertently pushing one of the buttons on the pad The hangup hook resembles those 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 carefully before buying, and it it seems too small to cope with, pick up a Kenwood MC-45. You’ll need to rewire the mike connector, but the 45 is a solid, full-sized microphone, sure to please the most ham-handed ham! The MC-46 has some nice features, though, and is probably well worth the effort required to get used to it Nothing is perfect, of course, and the TR-7730 is no exception I found three relatively minor things I would like to see improved, First, the main frequency display is anything but easy to read No doubt the location I chose for the rig doesn’t help matters much, but under most daylight conditions, the display is pretty hard to read The other two problems I encountered involve the scanning circuit.
There are an awful lot of 5-kHz split repeaters out there now, and it would be useful if the band-scanning circuitry stopped with the discriminator centered There are currently only two rigs available that offer this feature (that I am aware of)— the Azden and the KDK 2025. Finally, for some reason the rig scans much slower in the memory-scanning mode than in the band-scanning mode. It should be easy to speed up the scan rate; the first person to come up with a good mod is guaranteed an article in 73!
These last two points are purely personal opinion, and others may never complain The dim display is another matter and has plagued almost every two-meter rig I have used. It’s time for the industry to correct this problem I’d like to see a blue display like the one on the TS-830S, with a dim switch for nighttime driving. I realize that it would be expensive, but the ultimate solution might be a light-sensing circuit like the one found on the IC-701.
Simply stated, the Kenwood TR-7730 is one of the best two-meter FM rigs for mobile operation I have used. I have used rigs that offered more features, rigs with better receivers, and rigs with brighter displays, but I have yet to test anything that combines the features, performance, compact size, and reasonable price of the TR-7730, For home use I might prefer something with more memories, like the new KDK, the TR-7850, or the Azden. For installation in the small cars that Americans are wont to buy, the TR-7730 is sublime. – 73 Magazine 1981 KA1LR –