B&K Saves The Day
by Paul McGoldrick
As readers of analogZONE are well aware we write product reviews all the time - but they have always been about the components that OEMs design into their final products, and we try to add value to the manufacturers' viewpoints by offering our own insight. From my viewpoint I only write about parts that I think are going to make money, even if I have criticisms of the products - or the manufacturer - in some ways. I have covered the test & measurement beat in the past (most recently at EDTN when I started the T&M section and then was happy to turn it over to Alex Mendlesohn) but we have no such section (yet?) in analogZONE. So, I thought it appropriate to mention a small lifesaver of a test product in an Editorial.
I have been experiencing a number of intermittent conditions on some transmission equipment that it is my pleasure to maintain (on a pro bono basis for my local public radio station). One turned out to be (eventually) a sub-D plug for which someone has used a computer part that had screw pull-ups that were too long to make a snug connection into the industrial socket. Another was a little baffling and required a number of visits to isolate it to somewhere after the input to a PUD microwave chain that was going 75 miles North and then 65 miles East-Southeast to the final point. The problem could have been in my end, before the PUD's demarcation line, in either of the microwaves, at the reclocking mid-point, or at the receive end. How to find it?
It required 3 people to be at the 3 sites at the same time - rather difficult to set up. I injected a test tone at my end and waited for the responses: Nothing was even getting to the mid-point although I could see from the duplex side of the system that the return was operating fine.
Fortunately, the test tone I was using was not a usual studio source but a generator I had pleaded to be shipped overnight for the test: It was the tone generator from the B+K Precision Model 262 Tone Generator & Cable Tracer Kit. I was putting +3 dBm (600 ohms) of an audio signal between 1 kHz and 1.4 kHz into the line with a 14 Hz "warble" on it. While waiting for the other two engineers to arrive at the top of their respective hills (I was lucky and early, as a passing PUD truck gave me a ride just after I had started my climb) I took the other half of the 262 kit - the Cable Tracer - and followed the long and expensive multi-core feed cable from the injection point (with a convenient RJ-11 connector in addition to alligator clips) and was able to hear the tone in the cable with the very high-gain amplifier in the tracer.
It was very obvious when I came to the point where there was an open-circuit in one of the conductors. Despite the noisy ambience - in a transmitter building crammed with radio and TV broadcasting gear, microwave racks for two different systems, fiber termination equipment, and GSM basestation racks, as well as the local police department equipment and a paging company's rack - the received tone from the tracer was absolutely steady until the level started to reduce after the break in the cable. The repair is now just a cheap splice instead of an expensive cable replacement.
This type of equipment has always been in the "strange" department for me - and ranked perhaps with equipment such as those that advertisers claim disarm police radar equipment - but that is not the case with this very solid, straightforward product from B+K. Yes, I have grumbles - this is me for heavens sake - like the jumpers to change the tone frequency (two choices) and the warbling/switching frequency (another two choices) require that you remove the complete circuit board from each part of the product: Not onerous, but a bit of a pain.
This kit is most definitely the kind of thing that one day is going to save you - at a minimum - a wallboard repair job when you find where those speaker, or telephone, or TV cables were run, without breaking through the wall. The unit will also power talk current on a dead telephone line and check polarity. Even for power lines (with the usual safety precautions, after killing the circuit) you will be able to trace which one is the one you need. This is a very nice insurance to keep in your tool box, where my proven kit is definitely staying.
The B+K Precision Model 262 Tone Generator and Cable Tracer Kit is available from B+K distributors at a street price of between $56 and $59. The company is located at B+K Precision Corporation, 1031 Segovia Circle, Placentia, CA 92870. Tel: (714) 237-9220; Fax: (714) 237-9214.