CB PLL Chip - Ranger-Forums - The Ultimate Ford Ranger Resource


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  #1  
Old 12-14-2005
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CB PLL Chip

What exactly does a PLL chip do?
Some people say it gives clearer reception and others say it increses the range.
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  #2  
Old 12-14-2005
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A PLL chip stands for "phase locked loop". It's a type of oscillator and theres no reason to put one in unless you have a bad one, or your rig is totally crystal controlled. The "local" oscillator in a rig controls what frequency you receive and transmit on.

Older rigs with multiple crystals (a pair for each channel sometimes) had a problem in that the crystals themselves had tolerance problems. Some people found the resulting distortion and what not objectionable I would imagine. Also, if you're not right on, the circuits in the radio would operate less effectively.

So, an older rig might have BOTH the benefits you cited from being retrofitted with a PLL oscillator.

All new rigs are PLL controlled, and another way that's described is that they are "synthesized" or "frequency synthesized" -- short hand for the "phase locked loop frequency synthesizer". Basically meaning having a circuit using a single "master reference" crystal, and that can "synthesize" any frequency you need -- without the need for multiple crystals for each channel. This is cheaper (nowadays) and allows more consistent operation of rigs that are "mass produced" and not "hand tuned". The master crystal can be a better unit and/or only a single adjustment is needed to put all channels "on frequency".

Last edited by n3elz; 12-14-2005 at 08:48 PM.
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  #3  
Old 12-14-2005
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so if I'm buying a brand new cobra, there's no need to worry.
Is there something that I can do to the rig itself to increase the range? I'm going to put a 4 foot antenna on my roof with one of those cell phone boosters on the tip (some say it works for them, got 50 from ebay a while back)
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  #4  
Old 12-14-2005
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That thing will do NOTHING, lol. Do yourself a favor, Chris, and don't listen to MOST of what CB people tell you. Technically, most of it falls into the realm of "old wives tales", lol.

Range is increased by better antenna MOSTLY. A full 8 foot (what's known as a "quarter wave") antenna is the best thing you could do -- though they can be a pain to tune and are very tall.

You can add an amplifier, BUT -- without a better receiver (and CB receivers generally aren't optimum), you'll be all mouth and no "ears"...

Part of the problem with CB is that the frequencies are so active. Even when you can't hear any signals, there is a constant "white noise" of all the signal residue from so many transmitters in use all over (including far away). It's interesting to tune through the CB band on a shortwave or ham receiver: it's like a cloud of increased white noise through that area with a few signals sticking up out of it!

Speech processing -- good processing -- maximizes your modulation without distortion and is almost as good as having more power. Actually you DO have more power since good speech processing increases the average power of your signal, while keeping the peak below the legal limit. A type of RF mod called "RF clipping" also can do that with even greater effectiveness but it takes a GOOD shop to do that right.

Probably you should either: A) Do what you feel you need to with regard to an amp and so forth. B) Get mods done by GOOD shop C) Bite the bullet and use the big antenna or D) drop CB and get a ham license so you can use some REAL radios, lol...
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Old 12-14-2005
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wow, an 8 ft is insanely huge
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  #6  
Old 12-15-2005
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It also works insanely well, ha ha. It typically doubles (or nearly does) your power over virtually all the other "shorty" designs.

How does it do this? Well, all antenna "gain" works the same way.

Take a light bulb and hang it out in free space and turn it on. Ignoring the base for a minute, it basically radiates in ALL directions equally -- it's a so-called "isotropic" radiator.

The problem with this is you're probably not talking to people in a 3-dimensional space that wide. So the people you're talking to are only getting a miniscule amount of the radiated light (in our example, but obviously radio waves here) and the rest is being wasted.

A typical "omni-directional" antenna is NOT isotropic. In fact, it's quite hard to build a true isotropic antenna. Most have a pattern that is more or less "donut shaped" with little to no radiation straight up or straight down, and varying amounts of energy at angles between that. Straight out, parallel to the ground, is the area of strongest radiation in a "perfect" vertical antenna.

But the point here, is that all the energy that was being wasted going up and down is now concentrated going OUT to the sides -- making a stronger signal.

In REAL vertical antennas, imperfect ground planes under the antenna typically cause the angle of maximum radiation to tilt upward some. This is sometimes called "take off angle".

For local communications with maximum range, you want a take off angle of zero degrees -- parallel to the ground. You also want as much of the energy channeled into the angle as possible, and as little at other angles as possible.

For "skip" or long distance communications of the GREATEST distance, you pretty much need the same thing. However, depending on conditions, the optimum angle for skip for "attainable" distances might be higher than that. For instance, perhaps to communicate 200 miles or so away by skip, you might want a 45 degree angle (I'm making the angle up -- I don't know what it would actually be).

For the longest distance example, the signal would go straight out, and because the earth is curved, it would end up heading out into space, but it would eventually hit the ionosphere and hopefully be refracted/reflected back down towards the earth the farthest theoretical distance it can go from where it started.

By the way, "beam" antennas use reflector and "director" elements to concentrate most of the energy in a single direction. Reflector elements work like the reflector behind a flashlight bulb, and directors act more or less like a "lens". Between them they can concentrate the energy marvelously and give you 10, 20, or 30 DB of gain. For reference, having 10 db of gain is like having a signal 10 times stronger, 20 db is like having a signal 100 times stronger, etc. (approximately). The catch? You have to point the antenna at who you want to talk to.

Finally, lets compare electrically "short" antenna's like K40's, Firestik's, etc. They have higher angled patterns than a "full length" antenna and so they do not provide the maximum distance. The full length (8 foot) antenna provides the lowest take off angle, and so provides the maximum distance of communication with the same power.

No matter how much rhetoric the "shorty" manufacturers give you -- they CANNOT perform as well as a full sized antenna. Period.

If they cite gain, watch out for the "dbi" indicator. It means it has gain over a non-existent, theoretical "isotropic" antenna. If they cited "dbd" (gain over a dipole) -- they would all have NEGATIVE numbers, lol.

A properly installed vertical, full length, has about the same gain as a dipole (reference antenna that actually exists, lol).

The problem on a truck, is that typically you have to mount them down low, and the trucks "ground plane" is asymmetrical and the pattern is not symmetrical EITHER. However, it's still typically better than any of the of shorty's in all directions, in my experience.

Okay, that was my half-arsed antenna tutorial. If it helped -- great. If not, sorry to waste your time!

I guess to summarize:

Shorty antennas: the longer the better, but always a compromise between mounting convenience vs. performance.

Full length antennas: best you can do without mounting a beam. Typically, at lower frequencies (like CB) they can be impractical for some applications because of the size.
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  #7  
Old 12-15-2005
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N3ELZ, do you have AIM, i have some CB questions...

Thanks
Rocky
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  #8  
Old 12-15-2005
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I'm sure a 4ft on the roof will be good enough for now, I'm only going to use it for road trips, or messing around out in the country
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  #9  
Old 12-15-2005
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What CB are you going to buy?
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  #10  
Old 12-15-2005
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Quote:
Originally Posted by RockysFord
N3ELZ, do you have AIM, i have some CB questions...

Thanks
Rocky
Negative. I do not do instant messaging. I do have a phone, however, if you'd like to call sometime: 302-897-5221
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  #11  
Old 12-15-2005
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My buddy's got one of those really old ones (good ol smokey and the bandit type) that is just sitting in his shop right now, so he was going to give me that one for free, but if it's no good I'm going to probably buy one of those cobras you can find at canadian tire on ebay if it's a bit cheaper with with the shipping
I'm not sure what kind my friend's are
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