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Qandswitching Pi-Net Inductor 1KW #B50A

WAS $71.18 NOW $49,95 Bandswitciiing Pi-Net Inductor 5QQW #851

WAS 530.00 NOW $29.95 Bandswitching Pi-Net Inductor 1KW #852

WAS $62,25 NOW $49.95 Model m Plate Choke 2500 V @ 500 Ma. WAS $6.30 MOW $5.49

See your dealer or write: Barker & Williamson, Inc. v<

Canal Street, Bristol, Pa, 19007

waverneter would be used. If you are working with a high-power stage, start with the counter loop far away, and only gradually bring it closer until you just get a reading, A very useful coil to use as the pickup loop is a coil from a grid-dipper ( GDO).

Incidentally, we have found that the counter makes the GDO into an extremely useful device. The problem with most GDOs

(and signal generators as well) is that their frequency calibration is terrible. But the counter solves all that - just take the next higher frequency GDO coil, connect to the counter, and use as the pickup loop, an inch or so from the GDO coil. By measuring the actual frequency your GDO is putting out7

you can align a tuned circuit right on. To find out the frequency of an unknown received signal, just beat the GDO against it and read the frequency. If the GDO doesn't go that high, use a harmonic. For example, we wanted to find out the frequency of a signal in the 160 MHz public service band.

We tuned in the signal on a cheap VHF

monitor radio, beat the tenth harmonic of a

16 MHz signal from the GDO against the unknown, and read the 16 MHz frequency on the counter. Multiply by ten, and you have the right value, and you don't even need the VHF scaler.

Another application along the same line comes when you have a real low-level stage, where there just isn't enough signal to count the frequency directly with the counter, or where there are several frequencies at the same time, as in a reflex amplifier. We solved that by plugging an earphone into the GDO, zero-beating it against the unknown, and reading the GDO frequency with the counter.

Finally, Fig. 1C shows how to measure the frequency of a transmitter — just connect the counter to another antenna near the transmitting antenna. We've used this approach at 2 meters, with a 1 9-inch piece o^ wire connected to the counter. We've been able to measure the frequency of a 1W handie-talkie about five feet away, which shows that the sensitivity is quite good.

To end the overall description of the counter, the parts list provides a complete list of everything you need to build the counter, The parts list is divided into 5 parts.

LEJD readou ts.

Part A has all the basic counter parts except

for the readouts, the VHF scaler and the power supply. All of these parts fit on the main 7 x 10 in. printed circuit board, except for the Hz-kHz switch which mounts on the front panel.

Part B describes the power supply, which provides a regulated +5V ±5% at about 1.5 amperes and +25V unregulated at about 10 mA, There's quite a bit of room for experimentation here, but make sure that the +5V supply voltage is well regulated, The diodes and filter capacitor for the +25V supply mount on the main px. board, but the +5V supply mounts separately- We did not design our own px. board for the +5V supply, since a number of commercial supplies and kits are available.

Part C describes the optional VHF scaler.

Except for the 50input pot and the HI-LO switch, all of these parts also fit on the main px. board, and can be added at any time.

Part D lists the parts for the readouts, with a choice of either Numitron, Minitron, or LED readout. (You could substitute NIXIE® tubes, but then you'll have to redesign the px. board since different IC decoder/drivers are needed.) The Numitron

Numitron readouts.

Solid state modules for VHF and FM Construction, All modules are completely wired and tested for twelve volt negative ground operation. They are constructed on G-10 glass boards using the latest in solid state and IC design. Average size of board is V/z X 4 inches.

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