I can’t hear you! Sometimes a reception problem cannot be traced to RF, electronic or mechanical causes. What’s left? ‘Know your customer’ is good advice. Also, tips for making VSWR measurements with a wattmeter faster and more accurate.
The first of the month always comes with a groan, followed by a sigh of relief. The groan, I think, is because of our “billing party.” The shop staff gets together, closes the prior month’s books, then prepares and stuffs bills into envelopes. In one swoop, we are ready for another month, and the customer has a timely statement. I hear that many small shops share the work just like we do.
“My favorite part,” said Ruben, “is when all the envelopes are picked up by the mailman, and we can concentrate on the next job.”
“Not for me,” I said. “My favorite part is to see the whole staff working together on the billing. This really helps you all stay in touch with the customer; sort of the final step in customer service.”
“My favorite part,” said Jerry, “is that the boss buys lunch and coffee for the day–My favorite part!”
The next day, with all the billing statements in the mail, Ruben began the new month by reviewing the day’s job assignments. Privacy Plus, the private investigations company, scheduled a repair for 9 a.m. Ruben assigned that job to Jerry. At 9:11 a.m., the ambulance operator already had an installation job in the work bay on which Karen was starting. Karen also had another install scheduled for the water company. It looked like another good month for the company. It always looks like a good month when business is in the shop from the first day.
“Jerry, front and center,” requested Ruben, as Fred, an investigator with Privacy Plus arrived at the shop. “Your nine o’clock is here!”
“Hi, Fred!” welcomed Jerry. “What’s the trouble with your radio today?”
“I can’t hear the dispatcher, Jerry,” said Fred. “I guess I should rephrase that; I hear the radio call come in, but I can’t understand what they are saying. Know what I mean?”
“Sort of. You hear them, but you don’t,” Jerry recapped.
“Yeah, that’s it,” agreed Fred. “I’ll leave the car with you and be back around ten o’clock–Thanks!”
Jerry took the keys, wrote up a job ticket and drove the car into the service bay. The installation for Privacy Plus was unusual in that it was a trunk-mount radio with the control head hidden in the glove box and the speaker under the drivers seat. The mounting configuration had been specified by Fred to allow the vehicle to be used in undercover investigations. It had only been in service for about a month. Fred had a normal dash-mount radio in his previous car. Jerry went right to work, following shop procedure to pull the main radio unit from the trunk. Then he performed a bench test to be sure the radio met the sinad specs of the manufacturer. This checked out OK, and because the sinad measurement is a fair test of audio quality, that only left the speaker under the seat to be checked.
“Boy, these hidden installs are a bear to work on,” lamented Jerry as he worked under the seat. “You almost have to work by feel, ’cause there’s little room to see.”
“What are you finding?” called Karen from across the bay where she was struggling with the antenna install on the ambulance.
“Radio checks OK, so the problem must be in the speaker,” he replied, still under the seat. “I hear a little rattle sound from the speaker, so I’ll put in a new one.”
Using the existing mounting, Jerry replaced the speaker with a new one out of inventory.
Fred returned as Jerry finished, signed the job ticket and drove away immediately. Jerry was just putting the job ticket in the “finished” basket, when Fred returned.
“Jerry, come on back up front,” requested Ruben. “Fred says he ain’t fixed yet!”
“Hi again, Fred,” said Jerry. “I told you the unit checked OK, but I thought I heard a rattle in the speaker. I put a new speaker in it.”
“Sounds the same to me,” Fred said. “I was just telling Ruben the problem wasn’t so bad when I had the other radio, but with this one I can’t understand the office. Maybe I shouldn’t have switched to the trunk-mount undercover radio.”
“Fred,” Ruben advised, “This undercover radio is top-of-the-line. You can’t get better than that. Can you leave it for the morning and let us do a little more checking? Wes will let you take his pickup for the day if you need wheels.”
“OK, I’ll leave it, and I’ll see you about noon.”
All the while Jerry and Ruben were struggling with Fred’s problems, Karen was having problems of her own. She was now finishing the install on the ambulance. The last thing was the antenna, and she couldn’t get it to work. Karen had installed a self-ground-plane antenna on the fiberglass roof, but it had high VSWR, and the readings jumped around as she tried to measure and adjust the radio and antenna combination. Starting with 25W forward power and 15W reflected power, she would make an adjustment to the antenna, and the wattmeter would read 45W forward and 17W reflected. And so, over and over, adjusting and adjusting, she was getting nowhere. This really was confusing because it was a 40W UHF radio, so she didn’t see where the power would jump around from 25W to 45W as the antenna was adjusted.
“Have you all got time to interrupt Fred’s problem and give me a hand?” Karen asked, more to everyone within earshot than to anyone in particular.
“Sure,” I said.
“Me too,” said Jerry.
“I’m all hands,” added Ruben, “and just what kind of a hand do you need?”
“I’m dumbfounded with this darned antenna,” Karen admitted. “I can’t get a straight reading on the Bird wattmeter for love nor money. What bothers me is that as I adjust the antenna, the forward power coming out of the radio jumps around. I can’t get it to stay steady so I can finish the install.”
“Let’s look at your setup,” Ruben said. “How are you checking it?”
“I can see the trouble from here,” I added, “and it is easy to fix. You have the wrong length jumper cable on your wattmeter.”
“What difference does that make?” Karen asked.
“Yeah, what?” echoed Jerry.
“I can explain all about critical length cables,” chimed in Ruben. “If the VSWR wasn’t very high, you would not have noticed much difference, Karen. But when the VSWR is bad, you know, really high, the insertion of the wattmeter in the antenna line causes an additional mismatch, so to speak, and the readings don’t mean anything. It just shows that the VSWR is awful, that’s all.
“Get out the file copy of the Bird instruction book,” I added. “It’ll show you a chart of jumper cable lengths to use for each frequency to eliminate the problem.”
“I’m always looking for a jumper, too,” Jerry said. “When I’m doing site work, I need a jumper that has type N connectors on it. I put N-adapters on the wattmeter for site work and leave the UHF connectors alone for shop work.”
“I’ll tell you a trade secret, Jerry,” confided Ruben, “If you promise to share it with every tech you meet. If you put an N-connector on one side of the wattmeter, a UHF connector on the other side, and then construct two jumpers, you can make life real easy. Cut the jumpers from the Bird instruction chart; one for VHF highband and a second for UHF. On each jumper, put a UHF connector on one end and an N-connector on the other. That way you can match N to N or UHF to UHF or N to UHF. Think about it. Works great, and no more jumper trouble. For this morning though, Karen, use my meter and cable set and get that ambulance done, OK?”
“Sure sounds like a good solution to me,” said Karen.
“Now, Jerry,” I asked, “What’s the scoop on your job with Fred’s car?”
“Ruben and I were about to get back to it, Wes,” answered Jerry. “The problem is that Fred can’t hear his office, but I checked the radio and replaced the speaker. We don’t know where to go from here.”
“Did you know that Fred was mostly deaf in his right ear?” I asked.
“No, I didn’t know that,” echoed Jerry and Ruben together.
“It happened a few years back when he was wrestling a gun away from a bad guy,” I continued. “The bad guy’s gun went off right next to Fred’s ear. He hasn’t been able to hear very well ever since.”
“Say,” said Jerry, “Maybe that’s the reason he can’t hear the radio. The last radio he had was a dash-mount with the speaker sort of right in his face. This radio has the speaker buried under the seat out of sight and muffled, too.”
“I think you’re on to something, Jerry,” I said. “How can you fix it and still give him the concealed radio that he wants?”
“I have an idea,” beamed Jerry. “You probably didn’t know it, but Fred’s car doesn’t have a broadcast radio. I took it out and concealed a recorder in the dash for Fred. How about if I wire his radio to feed the old dash speaker for him. That’ll put quality audio right into his face, and maybe he’ll hear his office OK.”
“Jerry, you surprise me,” I said.
“You sure do,” added Ruben.
“Me too,” Karen butted in, “and because I’m done with the ambulance, I’ll give you a hand. My next job, that pickup truck, will be a piece of cake, and we’ll all be done by lunch.”
“Well Jerry,” I said after Fred came by and picked up his car, “you sure had a happy customer. Just what is it you credit for your success, if I may ask?”
“I remembered what I learned in radio school,” gloated Jerry, “The instructor used to tell me every day ‘Jerry, you won’t get anywhere if you fix the symptoms and not the problem.’ This was never more true than with Fred’s symptoms.”