For those who have never encountered an autodialing microphone before, it is a device designed to store several phone numbers and feed them into an FM transceiver at a predetermined speed at the press of a button. This is the basic function it must perform—but manufacturers and users alike soon discover that an autodiaier must have several other features to perform adequately in the real world.
Like the Heathkit ^Matic memory keyer (to be revrewed in June), the CES Microdialer is a second general ion microprocessor-controlled device designed to make life a tittle easier for the amateur radio operator. Also like the Heathkit, the Micro-dialer has solved many of the problems experienced with the generation of deuces that preceded it.
One of the most striking improvements incorporated into the Microdialer is found In its layout. It makes sense to have the buttons and the mike element on the same side of the microphone. Several microphones have the touchtoneTW buttons on one side and the mike element on the other. These must be hung up carefully, to avoid pressing one of the buttons by accident. This is a small point, however, compared lo some of the other problems the Micro-dialer solves.
Some owners of earlier autodialing microphones were quite chagrined lo discover that their mikes occasionally suffered a glitch which locked their rig in the transmit mode. Hard luck If It happened when the rig was unattended! It was clearly injurious to the microphone, transceiver, and the blood pressure levels of others trying to use the frequency, CES cured the disease by removing the regulator chip (a source of heat) from the mike, putting in the radio instead. and tying the microprocessor's reset pin to the hangup hook. As long as the mike hang* er on the vehicle's dashboard is grounded (and you use it!), there is no chance of an accidental transmission. Grounding the reset pin also lowers the mike's current drain from 120 mA offhook to 60 mA on*hook. The dashboard in my car is plastic, so i simply ran a wire from a bolt in the firewall to one of the screws on the mfke hanger, PL™ users should note that there is an extra conductor in the mike cable which can be used to enable a PL decoder when the mike is hung up and disable it when it is removed from its hanger. Nice touch!
The Microdialer really shines in the ease-of-use department. For example, when you dial a number in the automatic mode, the mike keys up the rig for ,3 seconds before sending a tone—sort of a "look out equipment, here come some tones!" This feature alone allows me to use the Microdialer on several repeaters that wonTt accept my other dialer, which keys the PTT line at the same instant it sends the first tone.
Another welcome feature is the programmable pause. This allows you to program the autopatch access code (up to three digits) and a phone number into the same memory. The mike dials the access code, switches back to receive for two or three seconds so you can make sure that the dial tone is there, and then keys the transmitter and dials the number. If your repeater has some perverse speed requirements, you can program the mike to send the access code at one speed and the phone number itself at another And to make all this happen, all you have to do is push and one of the numeric keys. The looks of envy you'H get from other hams when you set all this in motion are worth every penny you pay for the mike! if you are motivated by more practical considerations, consider that you can easily call home, the police, or whatever with the Microdialer, while your vehicle is in motion, without taking your eyes off the road for a second.
Entering numbers into memory is no easier or harder than with other autodialers we have tried. Memories 1 through 5 hold up to eieven digits, and 6 through 0 hold up to seven. Dialing speeds from one to eight digits per second can be programmed, and I am happy to report that there are several touch-tone decoders in common use which can cope with the highest speed.
One repeater J use is plagued by a childish individual who frequently transmits tones while a user is trying to dial a number. With the Microdialer, I could bring up the patch and dial the number before our "friend' could find his or her mike.
If the Microdialer has any weakness, ft lies in the simple fad that it involves some installation, Let's face it: There are a lot of guys who are too lazy to use a soldering iron. If a microphone doesn't come with the righi plug for their rig attached, they aren't interested. To them I say, turn the page and read another article.Those of you who aren't afraid of a little work, read on!
The first thing you have to deal with is the regulator. OES solved a major problem by removing it from the mike case, but they created a minor one while doing it. You have to find a spot inside the rig for the tiny board which holds a 7805 regulator and a couple of filter caps. You also have to supply it with an unswitched source of 12 V dc, If you are using a rig over a year old, this doesn't present any probiem, as there is usually lots of room for additions. I chose to use the Microdialer with my Kenwood TR-7730, one of the smallest rigs available. Getting the 12 V dc was easy—
finding a spot big enough for the regulator board was not. There is a nice opening at the rear of the rig that Kenwood suggests is good for a CTCSS encoder. It may be OK for the encoder, but the rf from the adjacent final amplifier added an unhealthy dose of hum to our audio when the regulator board was put there. 1 finally ended up removing the internal speaker, which 1 never used anyway. This yielded plenty of room for the microphone's regulator and a Communications Specialists programmable CTCSS encoder/ decoder board. I stored the speaker and its mounting hardware in a safe place, in case i wanted to restore it to its original condition. If there's a will, there s a way, and if it'll fit in a 7730, it'll fit anywhere!
I found the Microdialer an extremely helpful addition to my mobile VHF installation. Compared to the microphone supplied with the TR-7730, the microphone element itself has a wider frequency response, with a noticeable improvement in lower mtdrange response. On the negative side of the ledger, it also has considerably less output, requiring the mike gain control inside the TR-7730 to be set much higher than previously required. This means that I cannot easily switch back and forth between the CES and Kenwood microphones.
I also found that the transmitter goes into the transmit mode for a brief moment when my sample is hung up on the grounded hanger. When I say brief, I really mean brief; it has never been long enough to bring up a repeater. I did not try the microphone with other radios, so I cannot say if this is only a problem with my particular installation or could be expected in others as well. In any case, it is not a serious problem, but you should be aware that it is there.
I am particularly fond of the microphone s shape and size. Many microphones must be held carefully, or your hand will cover the element, yielding muffled audio. You have to really work at it to make this happen with the Microdialer. It may be of little consequence to southern ers. but dwellers in the land of snow and ice will ibe happy to hear that the microphone cabie is made of a material which stays flexible at a far lower temperature than other cables we have encountered.
Another point worth noting is that when used in the manual mode, the Microdialer behaves like a normal, run-of-the-mill touchtone pad Certain other autodialers become rather churlish in the manual mode, beeping irritably and locking up for a second or two if you try to make it do something it thinks it shouldn't be doing. Rest assured that the Microdialer is too wefI mannered to engage in such loutish behavior!
If you use an autopatch a lot, or frequently access your repeater's control functions, an autodiaHng microphone can uncomplicate your life. The CES Microdialer incorporates some much-needed improvements over previous units and is priced at $59,95 for a 500-Q model The only feature that is missed is the ability to permanently store a series of numbers on a ROM chip. Maybe next year.,.
For more information, contact CES. 260 W, New England Ave., Winter Park FL 32789. Reader Service number 494.
Paul Grupp KA1LR/4 Casselberry FL
It s easy to say that a tuner's a tuner, but if that's so why can you build one for next to nothing or spend over six hundred dollars for a motorized autotuning marvel? The answer boils down to power handling capability and convenience. Heath-kit's model SA-2060 antenna tuner represents a good compromise between the extremes of tuner design. Selling for $254.95, it's rated to handle the full legal power limit, contains a built-in wattmeter and antenna switch, and uses a roller inductor rather than the tapped coil used in many tuners, making it a lot easier to use than that coil-and-jumper-clips device you built as a Novice.
The SA-2060 uses the now standard T-network matching scheme and with its roller inductor can provide a match to some loads that tuners using tapped coils simply can't cope with. It
The Heath SA-2060 tuner features two meters. (Photo by N8RK)
Two variable capacitors and a roller inductor form a T+network in Heath's SA-2060 tuner (Photo by N8RK}
The Heath SA-2060 tuner features two meters. (Photo by N8RK)
covers frequencies from 160 to 10 meters and can handie random wire or balanced feed antennas. A built-in 4:1 balun helps tame the wild impedances that are sometimes found when using tuned feeders.
When this hit arrived, my first thought was that there couldn't be much involved In building an antenna tuner since at the minimum only two or three components are required, Wet), when Heath tells you that you build this tuner, they mean It. It's up to you to assemble the two variable capacitors out of metal plates, ceramic Insulators, and threaded rods. The roller inductor also needs assembly, although thankfully the coil itself is prewound.
Heath says that this kit is a three-evening project That isn't far from the mark, although I spent considerably more time because of a modification I wanted to make (more on that later).
Although the instructions put the capacitor and coif assembly about halfway through the project, Td suggest putting them together at the beginning so that all the little parts they use are out of your way. Assembly of the capacitors is for the most part very easy and great therapy after a hard day at work. Just keep slipping those little metal plates onto the assembly. HTs a lot like threading popcorn onto a thread at Christmastime.
The rf sensing assembly for the wattmeter and the antenna switching circuitry are preas-sembled in a box which mounts on the back of the tuner chassis. Providing the critical wattmeter circuits already assembled and calibrated was a great move on the part of Heath. Not only did it speed up construction, but it's nice to be able to rely on their calibration (my tests show the SA-2060hs meter to read within 5% of other meters used at W2NSD/1), The wattmeter actually uses two meters, one to show forward power on scales of 0-200 or 0-2000 Watts, and the second to read either reflected power (on scales of 0-50 or 0-500 Watts) or swr.
\ found the reflected power mode to be easier to use than the swr mode when adjusting the tuner All that's really necessary is to adjust for 0 Watts reflected power, so there's no need to know actual swr. Having dual meters is very convenient, since some tuning combinations can produce misleading reflected power or swr readings. By keeping an eye on both forward and reflected power, its easy to spot these conditions and to tune for optimum settings.
The SA-2060 antenna switch provides three positions. One routes the signal through the wattmeter but bypasses the tuner, while the other two select coax-fed antennas which go through both the meter and the tuner circuitry. There's no way, however, to switch the tuner in or out of tine on a specific antenna—If you want to run the antenna through the tuner, you must do so all the time. This Isn't really such a bad thing, since the tuner does act as a low-pass filter and helps prevent TV!, but it is inconvenient to have to adjust the tuner before using that antenna even if the swr in the part of the band being used is low enough such that the tuner isn't really needed.
There is a serious problem with this antenna-switching scheme if you want to use both coaxial and wire-fed antennas The random wirefbalanced feed terminals are connected to the tuner before the antenna switch, with the result that any antenna hooked up to these terminals is always in line and will be paralleled with a coax antenna se lected by the antenna switch. This renders the switching system almost useless, since before switching to a coax antenna you have to go behind the tuner to disconnect the wire one. Fortunately, the fix for this problem is rather simple if you're willing to drill! a hole in the chassis and change around some wiring (see box and photo).
With the antenna switching changed as described, the tuner is a joy to use. It handles a full kilowatt with ease (although the tuner should be adjusted before running at the power level—no tuner is designed to handle the voltages that may appear when feeding a kW into 15:1 swrl)f and it survived the toughest test 1 can think of. While driving a vee beam with full power on 80 meters, the open feeder arced through a supporting board. The feeder was burned in two and the board caught fire, but the tuner survived this rather severe mismatch with no more than a brief arc between capacitor plates. Never let it be said that we baby equipment at W2NSD/1!
In more normal use at my home station, the SA-2060 has easily matched every so-called radiator I've connected to it, including a very badly mismatched vertical, a more-than* random random wire, and a coax-fed collinear dipole that
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