found cb shop....

[Aircargo]

found a cb shop about 26 miles away...they sounded very fimilarized with cb units. asked about tune and peak ect. $30....on 29 nw cobra
even said they would put rf gain switch to control watts like i read on a post. they said not good idea but sounded like they would do that.(not sure if included in $30)
then...later asked about putting LARGER finals on unit said he doesnt do that...

what are larger finals...he said makes unit hotter. isnt that if u keep it on for like 1 hr or more constantly?

txs all....

[rfradioconsult]

From your (CB User) perspective what does the "peak and tune" procedure gain and how does it impact over-all radio performance. Really I'm just curious from a technical standpoint.

[KOK5CY]

From my understanding being in CB for yr's i've found out a peak and tune is just a simple turn of a pod on the TX side . The tech hook's up a 50 ohm dummy load and dead key's the mic with no audio and set's the output power to the factory setting's and then check's the RX pod to make sure the RX is working .

Now for the final's i've found out from other cber's the bigger the final the more dead key power it has in other word's SWING power . It just depend's how big the radio is some tech's won't touch a small radio .

IMO some tech's just want you'r money for a 10 min tune up and when you go to use the radio it's not what you paid to have done .

[rfradioconsult]

Ok the tech "peaks the final TX stage for max output; what would you see as a nominal change in RF power output; before 3.6 W after 3.9 W. Any first person observations?

[N_Jay]

Originally Posted by rfradioconsult

Ok the tech "peaks the final TX stage for max output; what would you see as a nominal change in RF power output; before 3.6 W after 3.9 W. Any first person observations?

If you don't get 1.5 to 3 dB improvement, no one will ever notice.

If it is not 3 to 6 dB it is not worth the effort.

[rfradioconsult]

Originally Posted by N_Jay

If you don't get 1.5 to 3 dB improvement, no one will ever notice.

If it is not 3 to 6 dB it is not worth the effort.

Double darn N_JAY that was whatI was leading to! People paying money for something that yields neglible end results; but thats nothing new in business.

[gewecke]

Originally Posted by Aircargo

found a cb shop about 26 miles away...they sounded very fimilarized with cb units. asked about tune and peak ect. $30....on 29 nw cobra
even said they would put rf gain switch to control watts like i read on a post. they said not good idea but sounded like they would do that.(not sure if included in $30)
then...later asked about putting LARGER finals on unit said he doesnt do that...

what are larger finals...he said makes unit hotter. isnt that if u keep it on for like 1 hr or more constantly?

txs all....

You found a real live cb shop?
.....now for a full gas can and a flare! Sorry...had to go there!

[DDan]

Originally Posted by gewecke

You found a real live cb shop?
.....now for a full gas can and a flare! Sorry...had to go there!

Yeah, I've been biting my tongue on this subject. I worked in a shop that did commercial and CB work a long time ago. I was the shop gopher. I put CB radios on the bench and checked power and modulation levels. Most radios were never even opened. There is not that much to be gained by "peaking and tuning" the average radio right out of the box. Doubling the power output would only add 3dB to the signal and there is no way you're going to get close to that.

Hype abounds and some people believe it. Nomex shorts on.

[Highlander_821]

Most Cbs are not aligned with real test equipment from the factory. They come close, but they also keep them tamped down a little on the modulation and carrier power to make sure they comply with the rules.

Just about any CB can benefit from having a trained tech with the right test equipment (signal generator, oscilloscope, calibrated freq counter and calibrated wattmeter, pulse generator, maybe a service monitor) and knowledge of the correct alignment procedure go through it and set it for best RX, full 95-100 percent modulation, and have it be bang on frequency in all modes. A 4 watt carrier at 100 percent modualtion produces 16 watts peak envelope power in the side bands. From the factory, the thing might key 3 watts and only modulate to 7 or 8 watts.

But the biggest gain is usually to be had on the RX side. Most Cbers don't realize or undetstand this, and they'll pay old Jim-Bob at the truck stop to tweak the carrier power, set the modulation to 300 percent (not good), spread the output coils, and put the covers back on and charge him 50 bucks! Big difference!

[kb2vxa]

NOW we finally get down to the brass tacks, the average truck stop screwdriver jockey is NOT a qualified radio technician nor does he have PROPER test equipment. Bottom like here is when you let one monkey with it he'll do more damage than good. On the other hand a PROPER alignment may yield decent results but that depends on whether or not the tuned circuits happened to "fall in" to begin with.

Nothing is aligned as a complete unit, CBs included, the coils and transformers are resonated on a Q meter individually during their production (usually by their own manufacturer and shipped to the CB factory) and what happens in assembly is a hit or miss proposition, usually hit but not always. I know, I was the tech who set up the Q meter and often used it myself. Oh how some things have a habit of drifting off frequency between fresh off the line and after sitting around for a few weeks, winding stresses relax changing the inductance value. That got a few strange looks from the government contract inspectors sitting next to me when every unit had to be re tuned. After a while they settle down, hopefully yours did before being soldered into the board.

Being that once upon a time I worked at a service shop and CB was one of our services I repaired and aligned plenty of radios so I guess that qualifies me to tell you that most of the time little may be gained by a complete going over by a qualified tech besides assurance the radio complies with it's FCC certification. "Tweaking and peaking" is a popular myth used by unscrupulous "technicians" to lighten your wallet, there is only so much that can be done and any improvement is marginal at best.

[N_Jay]

Probably mostly right Warren, except a lot of radio electronics today are electronically tuned and tested as a complete unit, or at least a complete board.

There is getting to be a lot less to tweak and tune inside. The lower volume the equipment, the more likely it is to still have a few places to put a tuning tool.

[DDan]

Originally Posted by kb2vxa

Being that once upon a time I worked at a service shop and CB was one of our services I repaired and aligned plenty of radios so I guess that qualifies me to tell you that most of the time little may be gained by a complete going over by a qualified tech besides assurance the radio complies with it's FCC certification. "Tweaking and peaking" is a popular myth used by unscrupulous "technicians" to lighten your wallet, there is only so much that can be done and any improvement is marginal at best.

That is exactly what I was getting at. I used a Bird watt meter and a service monitor. If I could get 100% modulation with a reasonable voice and it was putting out 4 watts it was a done deal. Someone mentioned tuning the receive section. I don't remember testing that but it was a long time ago and I was just following direction.

[rfradioconsult]

My take on CB radios; they are a mass produced product, that employ perhaps a half dozen slightly different designs, that use parts specifically selected to provide the level of performance that the consumer will deem satisfactory. In most instances once the products reach final test they run an automated pass/fail and pass go out the door; rejects at most get a quick look see and if cannot be repaired in a few minutes they most likely go to the local Chinese dump

[n5ims]

Quite often the peak and tune shops are looking for folks like a trucker I heard on my CB several years ago. The conversation was about how cool his antenna was after he put a fluorescent lamp next to his antenna (about a week before) so it would glow when he transmitted. A few miles later he was complaining that "for the last week my radio just won't talk so good" and how he was going to have the shop "tune it up" for him.

I'll bet that there's no correlation between the "glow when he talks on the CB" and the limited talk range on his CB. :-)

[n9emz]

Originally Posted by N_Jay

If you don't get 1.5 to 3 dB improvement, no one will ever notice.

If it is not 3 to 6 dB it is not worth the effort.

Guess that's why 120w PEP RFX-75 equipped Cobra 29s are becoming so popular.

[kb2vxa]

Thanks for the giggles John, and reminding me of a few of my Frankenstein experiments. If he lit the lamp in proximity of the antenna he has a "leenyar", if not he'd have to touch the lamp to the radiator at the tip. Back in my CB daze somebody came out with the Firefly, simply a small neon lamp in a plastic enclosure that snapped onto the antenna. "Gee, this is cool" I thought and wrapped the leads of an NE-2 around the tip of my mobile whip. Somehow it looked nice but my signal went way down, the SWR was sky high. Thank goodness for tubes, transistors won't tolerate such abuse. That should give a clue why the trucker jus' ain't gittin aowt, dang, gotta git 'er tweaked an' mess it up REEEAL gooood. (;->)

Oh Dan, you too reminded me of something. Some years ago a friend and I had the venerable Bearcat BC101 and decided to run them through their paces on a Cushman service monitor. They were up to specs alright but having the factory service sheets and original blueprints, yes, blueprints we set about an alignment job. They came out the hottest receivers I'd ever seen, the sensitivity came up enormously. Of course being single conversion it was easy, I wouldn't attempt one of today's engineering nightmares.

N_Jay, I guarantee those receiver boards were never tested except maybe pass-fail. (;->)

"Guess that's why 120w PEP RFX-75 equipped Cobra 29s are becoming so popular."
Eh, maybe because a well designed and built 1500W AR amplifier REQUIRES that drive level? ('Scuse me while I pick myself up off the floor and catch my breath.)

[n9emz]

Originally Posted by kb2vxa

"Guess that's why 120w PEP RFX-75 equipped Cobra 29s are becoming so popular."
Eh, maybe because a well designed and built 1500W AR amplifier REQUIRES that drive level? ('Scuse me while I pick myself up off the floor and catch my breath.)

Shore 'nuff yore 'aight, Warren. That's about what I see out of mine.



However, I think it might be difficult to tune the amp with that Cobra 29. Perhaps it would require something like a single 2879 kicker volted at 14 to get that little detail taken care of. Possibilities are wonderous as well as endless.

[rfradioconsult]

Quite a number of CB operators practice their "southern drawl" by putting a handful of marbles in their mouth whilest talking on their radio and slowly spitting them out one-at-a-time, when they have lost all their marbles they are then a true CB radio operator!

[N_Jay]

Originally Posted by kb2vxa

. . .
N_Jay, I guarantee those receiver boards were never tested except maybe pass-fail. (;->)
. . .

Don't know, have not seen a CB assembly line, (have you?) but both LMR and cellular equipment runs through a test and tune station on the assembly line.

[gewecke]

WHY the hell would any one want a supposedly 120 watt p.e.p. a.m. cb radio to begin with? Much less want to spend hard earned cash for it??
Wouldn't it make more sense to simply buy a radio which is designed to produce that kind of rf output to begin with??
Not a cb radio! (ick!)
N9ZAS.