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Romstar
Junior Member
Username: Romstar
Post Number: 41
Registered: 3-2007
| | Posted on Tuesday, March 27, 2007 - 8:42 pm: | 
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I know some people may disagree with me, but I think a little should be said about what makes a good tech.
A good technician will have an oscilloscope on his bench. Not under it. It is such an essential tool that it should be right there ready for him to use. You can sometimes get by without it, but it makes the job all that much harder. Now, with that said, some starting techs won't have all the tools, BUT they will know what they can do, and most importantly what they CAN'T do.
Even a starting tech should have two multimeters. An analogue, and a digital. This is important because bar graphs on an LCD aren't the same as a twitching needle on a good meter.
A good technician will have an audio tone generator, and a better technician will have an RF generator. Some may have a combined unit.
A good frequency counter is a must. Not the type you can plug into some radios, but a precision frequency counter. It should be at least 7 digit, or better.
Power supplies, dummy loads, stand alone watt and modulation meters, stand alone distortion meter and other various gear.
A SINAD meter. This piece of test gear will be on the bench of a really good tech. Older techs may have various tools that perform the same functions.
A truly serious, all out tech will have a spectrum analyzer. If you don't see one though, don't worry too much. If you thought 'scopes were expensive, you're never priced a spectrum analyzer.
There is one other tool that sets the great techs aside from the merely basic and mediocre techs though. That's brains. It's a knowledge not only of what is in a radio, but WHY it's in a radio. Most top of the line techs won't clip things unless it's the only way, or the best way. It's almost never the best way, so judge accordingly,
It's your gear, your time and your money. If you aren't sure about what is being done and why, ask questions. If you don't like the answers, pick up your gear and walk. A good tech is happy to explain things to you, and while we don't often like to have customer's hovering over our shoulders we are willing to tolerate it for a while if you really are that nervous.
A tech who won't show you what they have done isn't a tech you want in your radio.
When you find a good technician, make an effort to show your appreciation for him. You can do this in two ways.
#1: Bring coffee and good humour
#2: Learn all you can about your hobby.
Number 2 is important because it increases your skill both as an operator, and also as a technician. and also, the more you know about what your tech is doing, the less he has to explain, and the faster he can get your gear done. He's busy, appreciate his time.
I could write a book on this topic I suppose, but consider these basic guidelines. Other's will add more about what they think makes a good tech. Pay attention to it all, and decide for yourself.
Good luck,
Romstar |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1469
Registered: 6-2004
| | Posted on Wednesday, March 28, 2007 - 3:57 pm: |
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I agree with most of what you wrote, but I have a few comments/questions. I don't see the need for a modulation meter at all, and a deviation meter is only needed for adjusting FM deviation. Also, for what purpose would you need a distortion meter or spectrum analyzer?
Aack! - Bill the cat
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Romstar
Junior Member
Username: Romstar
Post Number: 44
Registered: 3-2007
| | Posted on Wednesday, March 28, 2007 - 6:13 pm: |
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Almost all of these export radios are now adding FM mode, so the deviation meter is a requirement to do a proper alignment of these rigs. Most techs are also going to work on HAM rigs as well, and this makes it a requirement.
The distortion meter is used in conjunction with the 'scope to measure overall harmonic distortion of the output signal. Even if you aren't over modulating, you can still cause a distorted signal if you make the wrong adjustments. The distortion meter is going to make this alignment much easier.
Additionally, for sideband you don't want to be another guy whose's a few kHz off, and the disortion meter is going to pick that up right away.
A 'scope is a great tool, but it isn't the end all be all of measurement equipment.
The spectrum analyzer is more and more important as you increase wattage output. Radio's are notorious for creating harmonics. Couple inadequate filtering with any attempted increase in power and you are likely to see harmonic transmissions. Scredriver jockeys are also very likely to cause spurious emmisions, and these are easy to see on a spectrum analyzer.
Move over to the amp category where filtering is either non-existant, or at best poorly designed or too broad banded, and you instantly see the advantage in having a spectrum analyzer.
Ah, the lowly modulation meter. No matter which way you slice it, this little meter is still one of your best friends when it comes to quickly, and easily getting an idea of how much modulation you are feeding a radio.
Ranger Communication Inc. lists the following equipment as necessary for properly completing an alignment on many of their units.
• DC Power Supply ( 13.8 Vdc, 20A )
• Oscilloscope (50 MHz), with X10 probe
• 50 W dummy load
• Frequency Counter - 100 MHz
• Digital voltmeter or Multimeter
• RF Signal Generator
• Audio Generator
• Automatic Distortion Meter
• SINAD Meter
• RF Wattmetter ( 25~60 MHz, 100W )
• Automatic Modulation Meter
Obviously some specifications would need to be increased if you are increasing the power, or re-tuning the radio for other frequencies. Knowing how to use these tools, and how to properly connect them to a radio under test is an important aspect of being able to properly align any tranceiver.
Romstar |
Bruce
Senior Member
Username: Bruce
Post Number: 4401
Registered: 9-2003
| | Posted on Wednesday, March 28, 2007 - 6:40 pm: |
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My home shop .....
• DC Power Supply ( 13.8 Vdc, 50A )
• Oscilloscope (50 MHz), with X10 probe 2 of them
• 50 W dummy load yes
• Frequency Counter - 1000 MHz (Y )
• Digital voltmeter or Multimeter ( Y )
• RF Signal Generator ( Y )
• Audio Generator ( Y )
• Automatic Distortion Meter ( NO ) WHY ?
• SINAD Meter ( NO ) I dont need it.
• RF Wattmetter ( 25~60 MHz, 100W ) 1.8 to 500 mhz 5 to 400 watts
• Automatic Modulation Meter ? NO
BUT I HAVE A DEVIATION METER and a simple spectrum analyzer so i can work on my own stuff .... |
Unit199
Intermediate Member
Username: Unit199
Post Number: 454
Registered: 8-2003
| | Posted on Wednesday, March 28, 2007 - 11:12 pm: |
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The equipment does not make a good tech. It is knowledge and understanding the way a radio or piece of equipment works. All the equipment in the world will not help if they do not know how or why the circuitry works the way it does.
Another thing, if they are a good tech, they will be too busy to show you what they done to your radio and that does not mean they are not a good tech. They may tell you what they did to fix it, but that is all they really have time for.
I do not care what equipment they have, the end result is what counts.
HARVE
UNIT199
CEF210
CVC18
KB0YVK
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Romstar
Junior Member
Username: Romstar
Post Number: 48
Registered: 3-2007
| | Posted on Thursday, March 29, 2007 - 7:49 am: |
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I've been in electronics and radios since I was a child. Had the benefit of my grand father's 50+ years in it, with all the stories, advice and guidance that came with that. There are some things that just don't change.
No matter how busy a tech is, if you ask him to take the time to show you what he did, he WILL take the time. He may make you wait so he can fit it into his schedule, but he WILL show you. If he refuses, he's a liar or an arrogent fool. You don't want either.
While the end result is what matters you can't get good results without the proper tools. Anything else is guesswork, and you definately don't want that with radios.
As stated, the most important tool is knowledge, and I said that in the very beginning, but it still takes the proper tools for the job. If you don't see the tools, they don't see the money.
Romstar |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1470
Registered: 6-2004
| | Posted on Thursday, March 29, 2007 - 4:32 pm: |
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I agree that the right tools are needed to do the job - but what job? I think it really depends on what you want a tech to do for you. If all you need is a microphone wired for your radio, all the test equipment they need is a DMM and a clip lead. If you want an alignment, then they need much more.
I honestly don't know anyone who uses FM on CB regularly, so if a CB tech doesn't have a SINAD or deviation meter I don't think you should rule them out.
The test equipment listed earlier looks more like what you would need for land mobile radio servicing, not CB. Of course if you are really into FM, then having a SINAD and deviation meter are necessary. I still don't understand why you would need a distortion meter if you already have a SINAD meter, and a spectrum analyzer is just overkill in my opinion. Harmonics are easy to calculate, and tuning to them on a scanner or other monitor receiver is a fairly simple way to determine if there is a problem.
One last thing - modulation meters and PEP watt meters are not test equipment - they are a swinging needle that is fun to watch when chatting on the radio. They tell give you no more useful information about what your radio is doing than a thermometer does.
Aack! - Bill the cat
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Romstar
Member
Username: Romstar
Post Number: 54
Registered: 3-2007
| | Posted on Thursday, March 29, 2007 - 8:31 pm: |
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I like the thermometer comment. That was choice!
Okay, harmonic distortion meter. This thing does both receiver and transmitter measurements. Is your receiver or audio amp causing distortion in your received signals? Are you putting out distorted signals? Good thing to know, but again it's not the end if it isn't on the bench.
A SINAD meter is a great thing to have because of everything it does. It's not a necessity of course, but if you are servicing ham rigs, or export radios it should be something you consider. For CB, no I wouldn't rule out that technician if he didn't have a SINAD meter.
The spectrum analyzer is a hard deal. The price alone makes it difficult for a lot of people to justify. However, you can't calculate spurious emmisions. I have seen people use a scanner or wide band receivr to check for harmonics, and the math isn't that hard.
Romstr |
Tech237
Moderator
Username: Tech237
Post Number: 732
Registered: 4-2004
| | Posted on Friday, March 30, 2007 - 9:07 am: |
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Modulation - the only true and accurate way to measure modulation is to observe the wave form on a CRO (oscilloscope).
Now me, I am a tech by trade and right now I have two of my own radios that need attention - one I am working on as it is only an intermittant switching problem and one, no output (suspected dead final IC), which I am about to farm out. Why? simply because I do not have any equipment to test it after replacing the final.
I used to have a nice piece of equipment that combined frequency counter, scope, signal generator (audio to around 1GHz) and several other functions but it was too big and heavy to bring over from Australia. One day I'll buy another one and get back into fixing radios again.
One thing I used to hate getting were radios that someone, with little experience and less equipment, had been playing with. Ask any tech these are our bane, because we have to spend time undoing what damage they have done BEFORE we have a chance of fixing the original fault.
Romstars list is not wrong as many added faults could have been avoided if the tech had had some of those items. Believe it or not but I have seen cases were changing a bad final has been enough to require the radio to be tweaked to remove spurious signals. Just remember although a final is a transistor it also contains capacitance, resistance and even a little inductance all of which may effect a radios tuning.
Simon
Tech237
KD7IEB
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Bruce
Senior Member
Username: Bruce
Post Number: 4405
Registered: 9-2003
| | Posted on Friday, March 30, 2007 - 10:35 am: |
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SINAD meter ....
After working on FM for decades you find BY EAR you can measure this ....
I HAVE a deviation meters that works just fine It's very old about 50 years but it also gets little use ....
My Generator is about 40 years old and goes from 100 khz to 800 mhz in 100 hz steps I have found it to be quite stable on 440 mhz and use it to adjust VHF/UHF preamps and i'm working on a way to try go get enough out of a 2nd ( marconi ) gen using it in sweep mode into a scope ( using a didoe detector ) to adjust cavity filters but as of now that has not worked well ....
Other stuff used in tests here are a GRID DIP METER and NOISE BRIDGE both are great for making that BALLPARK cut on a antenna .... |
Tech833
Moderator
Username: Tech833
Post Number: 1634
Registered: 8-2002
| | Posted on Friday, March 30, 2007 - 1:29 pm: |
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All good comments here. Interesting what Unit 199 said about techs needing brains more than gear, so true!
Although, I have had less experienced techs use my bench, and it is interesting to see how fast they catch on to all the fancy high $$$ test gear when it is available to them. A mediocre tech with good brains becomes a stellar tech with the right test gear. I can't even imagine how I would set up a wideband I.F. in a microwave receiver without the ability to sweep the I.F. and look at the results in real time on a display. I don't know how we ever got along without this stuff way back when. I never use the wattmeter for tuning transmitters! I use an IFR so I can see how much power is in the carrier and not being wasted in spurs or harmonics. Impossible to do without a selective spectrum analyzer. Modulation is so much easier to set up when you can view positive and negative peaks in real time. A modulation meter is the LAST thing I would think of using when adjusting an AM transmitter. Does this make me a bad tech? Maybe a lazy one, but certainly a more accurate one! At least, when equipment leaves my bench, I know EXACTLY how it is working and I can tell if it will keep working and be reliable. Broadcasters will not tolerate equipment that is not reliable and accurate, so my bench has to be also.
If anyone is interested in the basic gear on my home bench, here it is-
IFR 1500 AM/FM (0.01 to 1 GHz. rf gen, scope, sweep gen, spectrum analyzer, wattmeter, freq. counter, SINAD, audio gen, demod, deviation, etc.)
IFR 1200 Super S (0.01 to 1 GHz. POCSAG gen, sweep gen, rf gen, scope, spectrum analyzer, wattmeter, freq. counter, SINAD, audio gen, demod, deviation, etc.)
Miniscope MS-215 (portable scope)
Variac (variable A/C plus load meter)
Amber 3500 distortion analyzer (audio circuit troubleshooting)
Audio Amp w/speaker (high imp for tracing signals)
Fluke 187 and 189 multimeters (my right and left hands!)
Several Fluke scope/freq/cap/ohm/meters
Weller solder station (variable up to 900 degrees)
PSA305 adjustable 30A power supply (0-30 volts DC)
Bird wattmeter (lives in the drawer almost all the time, mostly use IFR's for watts)
Icom receiver (0.3 to 3000 MHz. AM,FM,WFM, SSB,CW,etc. for monitoring what I am working on)
Dell Laptop computer (various programs including full screen spectrum display, testing modes, radio programming, etc.)
That's all I can think of off the top of my head. |
Romstar
Member
Username: Romstar
Post Number: 57
Registered: 3-2007
| | Posted on Friday, March 30, 2007 - 1:46 pm: |
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Every piece of test equipment has a short coming somewhere. Sometimes ever the $80,000.00 units have compromises.
The original point I was trying to make was simply that a good tech WILL have a variety of test equipment at his immediate disposal.
If the guy you use is missing some of it, they may have other alternatives or methods.
Brains is the overwhelming issue in radio service. No amount of equipment can make up for a lack of understanding about what is going on inside of a radio.
However, while I *DO* stand behind my listed test equipment, it isn't the end all be all, make or break deciding factor. The tools are there to make our job easier and more accurate.
If you don't see any tools other than a combo test unit and a multimeter you may want to rethink who is in your radio.
For my money, I want to see a 50+ MHz 'scope at the bare minimum as well as some other common and necessary equipment.
I would love to have a spectrum analyzer, but I can't justify the cost to the wife right now. So, I will wait. It won't be as accurate as I would like, but it will be close.
Your milage may vary.
Romstar |
Tech237
Moderator
Username: Tech237
Post Number: 737
Registered: 4-2004
| | Posted on Tuesday, April 03, 2007 - 9:36 am: |
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Paul - it is the IFR that I miss, but only so much you can fit in two suitcases hihi.
Simon
Tech237
KD7IEB
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Tech833
Moderator
Username: Tech833
Post Number: 1643
Registered: 8-2002
| | Posted on Tuesday, April 03, 2007 - 2:36 pm: |
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I don't know how I could work without one! You can drop by and play with one of mine if you get 'homesick' for one. I'm not stuck up, I open my bench to people all the time. |
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