Equipment to properly tune radios.

[Athecal]

First things first, I am not wanting to do illegal or irresponsible peaking and tuning to radios. Quite the opposite. My grandfather is a truck driver and has a large box or two of cb radios he has collected over the years that have issues of one kind or another. I am good with circuit boards and replacing components, I repair audio amplifiers for cars and home theater fairly often as a hobby and for some small profit. I would like to know what equipment would be needed to repair these old radios and bring them back to their peak legal performance. I assume from everything I have read that many will need modulation limiters soldered back into the pcb and some may need new finals if they have been burned out. Where can you buy quality components for cb radios, digikey/mouser?

My grandfather knows I am big on electronics and suggested that there may be some decent money to be made repairing radios if I learned to do it correctly. Being a highschool student in a small town I have more time than opportunities so I would like to make my own. Many people have units that they are sentimental about and have been hanging on to for years or decades. They either took them to someone who ruined them on the spot or did something that ended up burning out the radio due to overheating over time most likely, and they are convinced that radio was the best they ever owned.

I have many of the tools I assume will be necessary already:
lab grade benchtop power supply
Fluke 117
Hakko soldering station
Small silent benchtop air compressor
SWR Meter
Helping hands
Hand tools
capacitors/resistors/diodes and other pcb components scavenged from audio amplifiers and other electronics that I was either unable to repair or weren't worth the cost to repair.

I have read posts where many of you speak to your experience about repairing radios the proper way with the proper testing equipment. I would really appreciate your advice on the proper equipment to be able to at least revive my grandfather's radios and set them properly, even if I never have a paying customer.

 

[KB4MSZ]

I think the biggest hurdle (once you have the test equipment) will be the alignment information needed to return a given model of radio to it's proper state of tune. Many years ago I inherited a very large collection of the Sam's CB manuals but somehow over the years these have all vanished. I can't remember for the life of me what I did with them.

Another thing that could crop up is if there are radios in this collection you are working with which are not legal FCC type accepted. This will require working in bands of frequencies outside of the CB allocation, and could also require additional test equipment such as a deviation meter if any of these have FM capability. While you may not intend to use out of band Frequencies or modes such as FM, there would still be the need to realign the radio taking these into account.

As far as equipment goes, I would think the following would be good to have on hand:

-An oscilloscope capable of at least 30 MHz with decent probes (some may consider overkill but I had access to one and it made many things easier such as modulation levels, SSB settings etc.)
-A frequency counter good to at least 70 MHz (possibly more depending on the design of the IF stages you may encounter)
-A signal generator for both a audio and RF sinewave source
-A transistor checker (your Fluke has a capacitance feature, not sure if its range would be adequate)
-A dummy load at 50Ω at the expected transmitter power, a set at 25Ω and 100Ω as well to help balance internal SWR bridges if adjustment is available (these MUST be non-inductive, not wire wound)
-A external speaker (in case the internal one is not functional)
-The bench supply must be capable of at least 5-6 amps with a FCC type accepted radio, possibly more with "export" radios which might require full power output to fully tune. An improperly functioning radio may well draw beyond this before repairing, extra overhead in the supply won't hurt
-A set of alignment tools (plastic handled screwdrivers which won't influence a circuit during tuning)
-Possibly an assortment of crystals may come in handy.
-A RF volt meter

That's what I remember off the top of my head, it's been awhile. I think Regan was president the last time I did this. Not sure how far into this you plan to carry the repairs but there may be certain IC's, power transistors etc. which are just not available anymore. There are certain "classic" CB radios which I would think could bring a good return for your efforts in a business sense (such as the Cobra 2000, Browning models, the old Cobra 148 GTL to name a few) but in general I think this endeavor would be more a labor of love than anything else.

 

[mmckenna]

I'm not really involved in CB other than occasional usage.

I think someone who focused on repairing CB radios correctly, including retuning/restoring them to proper/legal operation, would be something good. Not sure how big the market is for that. CB isn't as popular as it was 20 years ago, although those that are into it are pretty serious.
We all know there are people that work out of their homes that have a watt meter and pretty much just focus on increasing modulation or power output. While that looks good on a meter, it doesn't always translate into a better signal. I think finding customers that understood the difference between meter 'swing' and actually putting out a good signal would be a challenge.

Maybe a good direction to focus would be acquiring old CB radios and fixing/retuning them, then reselling to enthusiasts. It's one thing to buy an old radio for your collection, it's another to have one that actually works well. I think if you could make your name known as someone that was good at restoring old radios, you'd be on to something.

As for equipment, I use a service monitor for my work, but what I do is focused around VHF, UHF and 800MHz radio systems. A service monitor, even used, and be very expensive. The one I purchased last year for work was $40,000. You can find used ones in the $1000 to $2000 range. Having a service monitor would probably put you ahead of 95% of the CB techs out there.

And I agree, finding the documentation to restore a radio may be difficult.

Good luck. Sounds like you have a promising career ahead of you. The industry needs fresh people.

 

[Athecal]

To be honest I never planned to make a career out of it. More or less just thought it would be a way to make some side money. I was unaware there was a collector's market on CBs, the only people I know or would initially know of me would be truck drivers like my grandfather who would be wanting radios repaired so they could use them again daily. The buy/repair/sell of them hadn't actually crossed my mind which is odd because that is what I do to make a profit on audio equipment. I actually built my entire home theater and my trucks sound system for a net $0.00 out of pocket thanks to this.

I figured an O-Scope would be a requirement and I've wanted to get one anyway for other purposes as well. A question regarding them and/or service monitors. Will a service monitor replace an oscilloscope or would I still have use for the o-scope even if I had the other, or do they roll dummy loads, swr meter, oscope, power supply ect all into one package. $1000 for a single tool that could accomplish all those tasks would be a bargain as decent used oscopes are by themselves $300 or so. I also really never planned to set the radios back to a specific factory specification. More or less derive the absolute best performance based on the limitations of the electronics inside and the legal limit, or where clipping/splatter whatever you want to call it began if this was below the legal cap then so be it. My power supply will do 30a @20vdc so no worries on there.

The actual issue is I am a highschool student who is not about to spend that much right this moment to fix some old radios. I will however move an o-scope farther up my list of tools to invest in and also keep an eye out for sales and such for the other items in the list. Perhaps one day I'll get into it as I collect the neccessary tools. Unless he can get enough people to pay upfront for diagnostic testing to cover the equipment costs(joking).

Thank you for taking the time to enlighten me.

 

[KB4MSZ]

I think finding customers that understood the difference between meter 'swing' and actually putting out a good signal would be a challenge.

Absolutely true. And this will actually be your biggest hurdle Athecal.

 

[jhooten]

A couple hours of labor and a few small parts puts you over the cost of a new CB. Never mind that added cost of having to source and buy a service manual, replace shop supplies, and keep the lights on. Do it as a hobby and you'll be okay. Try to make a living at it and you are going to be very disappointed.

 

[mmckenna]

A couple hours of labor and a few small parts puts you over the cost of a new CB. Never mind that added cost of having to source and buy a service manual, replace shop supplies, and keep the lights on. Do it as a hobby and you'll be okay. Try to make a living at it and you are going to be very disappointed.

Yeah, I agree 100% with this. I worked with a guy that used to own a TV/VCR repair shop. Made a lot of money until the big box electronics store showed up in town. Within a few months his business dropped to pretty much zero.

A good way to look at this would be the learning experience. Don't do it so much for the money, but more as a hobby. Work like this could lead to a well paying career in the industry. Finding younger people that have the interest and a bit of experience can be hard.
While you are at it, see if you can find some courses on IP networking. IP Networking + two way radio experience would land you a great job in many places.

 

[prcguy]

In the 1970s I worked for the largest CB mfr in the world and have had my hands in thousands of CBs. I agree with everything below but you can get away with a very cheap tube CRT oscilloscope and connect the vertical plates across your dummy load to see the RF carrier and modulation. That with a watt meter, dummy load and RF signal generator with internal 1KHz AM modulation and volt/ohm meter will cover most repairs and alignment. A freq counter is nice but many radios don't have a way to net them back on freq, so it becomes just a go/no go type of test equipment.

I think the biggest hurdle (once you have the test equipment) will be the alignment information needed to return a given model of radio to it's proper state of tune. Many years ago I inherited a very large collection of the Sam's CB manuals but somehow over the years these have all vanished. I can't remember for the life of me what I did with them.

Another thing that could crop up is if there are radios in this collection you are working with which are not legal FCC type accepted. This will require working in bands of frequencies outside of the CB allocation, and could also require additional test equipment such as a deviation meter if any of these have FM capability. While you may not intend to use out of band Frequencies or modes such as FM, there would still be the need to realign the radio taking these into account.

As far as equipment goes, I would think the following would be good to have on hand:

-An oscilloscope capable of at least 30 MHz with decent probes (some may consider overkill but I had access to one and it made many things easier such as modulation levels, SSB settings etc.)
-A frequency counter good to at least 70 MHz (possibly more depending on the design of the IF stages you may encounter)
-A signal generator for both a audio and RF sinewave source
-A transistor checker (your Fluke has a capacitance feature, not sure if its range would be adequate)
-A dummy load at 50Ω at the expected transmitter power, a set at 25Ω and 100Ω as well to help balance internal SWR bridges if adjustment is available (these MUST be non-inductive, not wire wound)
-A external speaker (in case the internal one is not functional)
-The bench supply must be capable of at least 5-6 amps with a FCC type accepted radio, possibly more with "export" radios which might require full power output to fully tune. An improperly functioning radio may well draw beyond this before repairing, extra overhead in the supply won't hurt
-A set of alignment tools (plastic handled screwdrivers which won't influence a circuit during tuning)
-Possibly an assortment of crystals may come in handy.
-A RF volt meter

That's what I remember off the top of my head, it's been awhile. I think Regan was president the last time I did this. Not sure how far into this you plan to carry the repairs but there may be certain IC's, power transistors etc. which are just not available anymore. There are certain "classic" CB radios which I would think could bring a good return for your efforts in a business sense (such as the Cobra 2000, Browning models, the old Cobra 148 GTL to name a few) but in general I think this endeavor would be more a labor of love than anything else.

 

[KB4MSZ]

I played with this stuff from age 10 in my dad's lab. It was chalk full of HP and Rohde & Schwarz. I had a blast.

 

[K4EET]

Back in the day, I thought you had to be licensed to repair CB radios. Since CB radios come under Part 95 of the FCC Rules and Regulations, are you required to be licensed by the FCC to repair CB radios today? It seems like you would. Just curious.

 

[prcguy]

At one point you did need to be licensed but not for the last 30yrs or more.

Back in the day, I thought you had to be licensed to repair CB radios. Since CB radios come under Part 95 of the FCC Rules and Regulations, are you required to be licensed by the FCC to repair CB radios today? It seems like you would. Just curious.

 

[mmckenna]

Back in the day, I thought you had to be licensed to repair CB radios. Since CB radios come under Part 95 of the FCC Rules and Regulations, are you required to be licensed by the FCC to repair CB radios today? It seems like you would. Just curious.

No, not anymore.

§95.919 CBRS replacement parts.
The operator of a CBRS transmitter may replace parts of the CBRS transmitter as stated in this section. All other internal maintenance and repairs must be carried out in accordance with §95.319.

And 95.319 says:

§95.319 Malfunctioning transmitting equipment.

(b) Internal repairs. Internal adjustments and repairs to Personal Radio Services transmitters must be performed by or under the supervision of an individual who is qualified to maintain and repair transmitters.

And in true FCC fashion, that's about as clear as a brick.

 

[RFI-EMI-GUY]

Back in the day, I thought you had to be licensed to repair CB radios. Since CB radios come under Part 95 of the FCC Rules and Regulations, are you required to be licensed by the FCC to repair CB radios today? It seems like you would. Just curious.

FROM FCC:

"You do NOT need a commercial radio operator license to operate, repair, or maintain any of the following types of stations:

• Two-way land mobile radio equipment, such as that used by police and fire departments, taxicabs and truckers, businesses and industries, ambulances and rescue squads, and local, state, and federal government agencies.
• Personal radio equipment used in the Citizens Band Radio Service (CBRS), Radio Control Radio Service (RCRS), and General Mobile Radio Services (GMRS).
• Auxiliary broadcast stations, such as remote pickup stations.
• Domestic public fixed and mobile radio systems, such as mobile telephone systems, cellular systems, rural radio systems, point-to-point microwave systems, multipoint distribution systems, etc.
• Stations that operate in the Cable Television Relay Service.
• Satellite stations, both uplink and downlink of all types.

NOTE: Possession of a commercial radio operator license or permit does not authorize an individual to operate amateur or GMRS radio stations. Only a person holding an amateur or GMRS radio operator license may operate an amateur or GMRS radio station.

Commercial Radio Operator License Program

Rule Part 47 C.F.R, Parts 13

www.fcc.gov

I think it is a mistake that Part 90, especially public safety, no longer requires it, however the 800LB gorilla /\/\ lobbied to eliminate that requirement.

 

[mmckenna]

I think it is a mistake that Part 90, especially public safety, no longer requires it, however the 800LB gorilla /\/\ lobbied to eliminate that requirement.

A GROL isn't difficult to get. For the most part, ~almost~ everyone I've run into in this line of work either has one, or has proven themselves pretty well.

A lot of agencies and large companies still require a GROL, however.

 

[RFI-EMI-GUY]

I think the biggest hurdle (once you have the test equipment) will be the alignment information needed to return a given model of radio to it's proper state of tune. Many years ago I inherited a very large collection of the Sam's CB manuals but somehow over the years these have all vanished. I can't remember for the life of me what I did with them.

Another thing that could crop up is if there are radios in this collection you are working with which are not legal FCC type accepted. This will require working in bands of frequencies outside of the CB allocation, and could also require additional test equipment such as a deviation meter if any of these have FM capability. While you may not intend to use out of band Frequencies or modes such as FM, there would still be the need to realign the radio taking these into account.

As far as equipment goes, I would think the following would be good to have on hand:

-An oscilloscope capable of at least 30 MHz with decent probes (some may consider overkill but I had access to one and it made many things easier such as modulation levels, SSB settings etc.)
-A frequency counter good to at least 70 MHz (possibly more depending on the design of the IF stages you may encounter)
-A signal generator for both a audio and RF sinewave source
-A transistor checker (your Fluke has a capacitance feature, not sure if its range would be adequate)
-A dummy load at 50Ω at the expected transmitter power, a set at 25Ω and 100Ω as well to help balance internal SWR bridges if adjustment is available (these MUST be non-inductive, not wire wound)
-A external speaker (in case the internal one is not functional)
-The bench supply must be capable of at least 5-6 amps with a FCC type accepted radio, possibly more with "export" radios which might require full power output to fully tune. An improperly functioning radio may well draw beyond this before repairing, extra overhead in the supply won't hurt
-A set of alignment tools (plastic handled screwdrivers which won't influence a circuit during tuning)
-Possibly an assortment of crystals may come in handy.
-A RF volt meter

That's what I remember off the top of my head, it's been awhile. I think Regan was president the last time I did this. Not sure how far into this you plan to carry the repairs but there may be certain IC's, power transistors etc. which are just not available anymore. There are certain "classic" CB radios which I would think could bring a good return for your efforts in a business sense (such as the Cobra 2000, Browning models, the old Cobra 148 GTL to name a few) but in general I think this endeavor would be more a labor of love than anything else.

^^^^ WHAT HE SAID^^^^^^

For less than $1K you can buy one of the surplus HP systems analyzers HP892X and similar, that will provide the functions shown bold underlined above and more, including spectrum analyzer and modulation analyzer.

Differences between the HP 8920A, 8920B, 8924C, E6380A, E8285A

That said, you can accumulate separate test equipment rather cheaply and with some study and practice you can test and tune radios with rudimentary equipment. Many of us did so early on.

The biggest problem is finding schematics and tuning information. This is less of a problem for older gear as they were intended to be serviced.

Avoid falling into the trap of tweaking equipment for more performance. The goal should be to repair and restore to factory performance.

 

[K4EET]

<snip>

§95.319 Malfunctioning transmitting equipment.

(b) Internal repairs. Internal adjustments and repairs to Personal Radio Services transmitters must be performed by or under the supervision of an individual who is qualified to maintain and repair transmitters.

And in true FCC fashion, that's about as clear as a brick. [my emphasis - K4EET]

That was where I was hung up but I did want to point that out. In the "old days" those that were "qualified to maintain and repair transmitters" were folks that were licensed. Your response answered my question and the loosening of standards is all part of a steady decline in everything.

 

[RFI-EMI-GUY]

A GROL isn't difficult to get. For the most part, ~almost~ everyone I've run into in this line of work either has one, or has proven themselves pretty well.

A lot of agencies and large companies still require a GROL, however.

Yeah, when I left /\/\, PS customers still wanted it and I found out quite by accident my name and GROL number was being included in various /\/\ service contracts though I was never asked to service those contracts, nor was I in the service department.

It would have been nice (and more ethical) to have been advised I was GROL responsible for the work being done by others for others.

 

[RFI-EMI-GUY]

I'm not really involved in CB other than occasional usage.
SNIP

Not sure how big the market is for that. CB isn't as popular as it was 20 years ago, although those that are into it are pretty serious.
SNIP

Good luck. Sounds like you have a promising career ahead of you. The industry needs fresh people.

Well the sunspot cycle is on its way back up. Also certain segments of the population are seeking alternative communications and it looks like interest in GMRS and CB are on their way up.

And it seems that certain vintage SSB CB radios still command a good price on the 'bay. Folks that are restoring a 70's muscle car, may want a working CB that reflects that era.

 

[prcguy]

"Qualified" does not mean they have to be licensed.

No, not anymore.

§95.919 CBRS replacement parts.
The operator of a CBRS transmitter may replace parts of the CBRS transmitter as stated in this section. All other internal maintenance and repairs must be carried out in accordance with §95.319.

And 95.319 says:

§95.319 Malfunctioning transmitting equipment.

(b) Internal repairs. Internal adjustments and repairs to Personal Radio Services transmitters must be performed by or under the supervision of an individual who is qualified to maintain and repair transmitters.

And in true FCC fashion, that's about as clear as a brick.

 

[mmckenna]

"Qualified" does not mean they have to be licensed.

Right, that was my loose interpretation.

Qualified may mean trained by the factory (where ever that may be). Or it might mean "owner of a golden screwdriver".

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