CB Radio Help

[Nole]

I know someone out there can help me with this problem I have heard some cb talk around here before.


I am trying to swr my cb radio and i am getting a really high reading on ch 40 (+3). On ch 1 it is about 3. i have a 48" whip with 18 foot of coax the cb is wired into the fuse box under the hood. please help I am out of ideas not that i had any in the first place.

[Shooter45]

Check for a good ground at your antenna mounting bracket. If that doesn't help, you may need to change the length of your coax.

For more help check out One Stop CB Forum.

[Nole]

thanks for the forward

[Hydra Shok]

Hey Nole, if your swr's are to high, you have to change the length of the antenna. An swr of 3 isn't too bad actually, but you can make it better. If you just have a metal whip you can either snip a little off of it at a time, checking the swr's after each snip of course, or you can get a shaft to make it a little longer. Make sure the doors are shut while checking, just like the vehicle will be while you are driving. Also make sure you have a good ground, it will squeal if you don't. Also make sure you have an inline fuse in the power line. 18 ft of coax is perfect, but don't loop the excess, it will cause an interference in the signal, just stuff it somewhere and let it fall where it may. Has the radio been tuned and peaked out? And do you have a linear amplifier? If you have a linear it is a good idea to run a wire from the case of the linear to the case of the radio, grounding them both to each other. Also if you have a linear, turn it off while you are checking the swr's. A goos site to check out is www.copper.com

I have the Voyage VR 9000 in my dumptruck and I highly recomend it. It's basically a generic Galaxy 88 at half the cost. If you have any questions ask away, been fooling with these things for many years now. Here is a pic of my office too :D . By the way, look in the pic of my truck at the antenna. It's a Wilson 2000, and the longer shaft I was talking about is right below the blue cover. You can get them in different lengths too.

[Marlin]

Back to what Shooter said, though, a good ground can go a long way toward settling the problem. I had a similar problem on the Toronado with the in-dash combination AM-FM-CB-CD-Tape. Once we made sure the ground was solid the SWR floated around .7-.9.

Same is true for Ham Radio in the vehicle.

[Nole]

where would be the best place for the ground. when i checked the swr i had the cb grounded to the alternator. the power coming from the fuse box under the hood. Where would be the best spot? The antenna is a groundless one, so would it help it i grounded it anyway? Thanks for the help so far.

Matt

[Txquadhunter]

Any clean metal area on your truck should place a good ground. wiether it is the alt like you did, motor, cab and frame. all the places on a truck are grounded together. depending on how old your truck is and if your in a area known for rust it can cause bad grounds to places. mainly the cab. But where you placed your ground on the Alt. if you look you'll see the Alt. bracket is the main ground point for the battery. besure your ground wire is shiney clean and point grounded is also shiney clean.

i'm not a big CB user but have hooked a few up. I usually hook stereo systems up. Where I draw main power for my Amp's is from the + side of the battery instead of the fuse box. The wiring and inline fuse rated at what it calls for to get the amps needed. this bypasses any interfence that can be picked up from other sorces at the fuse block.

[JohnK3]

Changing coax lengths does little to truly change the SWR of a transmitter/antenna combination. At best, it masks the problem.

The trick is to make the antenna resonant at the chosen frequency, with a feedpoint impedance that matches that of the transmitter output. Change the length of the antenna to improve the SWR, as Hydra Shok suggested.

First, you have to measure the SWR at various channels. Check to see if it gets better or worse as the channels get lower. If it gets better, then your antenna is too long. If it gets worse, then your antenna is too short. Remember, as your frequency goes up, the wavelength gets shorter.

Grounding is absolutely a requirement for good SWR and reception. An antenna requires the ground to provide the other half of the signal. Unless you're running an odd-wavelength antenna, such as a half-wave or 3/4 wave whip, you need a good groundplane. An antenna attached to your mirror bracket won't have a good groundplane. An antenna in the middle of a good metallic hood or roof of the vehicle has a good groundplane. Grounding needs to be solidly to a major chunk of the vehicle. Ground as close to the transmitter as possible, using the heaviest gauge wire you can. I like to ground using fairly wide (1" or more) tinned braid. You can get this by taking a piece of heavy coax apart and taking the braided piece out and flattening it. Tin the ends using solder to keep it from unravelling.

73 de W5NNH

[inplanotx]

where would be the best place for the ground. when i checked the swr i had the cb grounded to the alternator.

The grounds should be as close to the unit and antenna as possible. It should be grounded to the FRAME, not the alternator. Power should also be taken from a wire close to the radio where it has noise suppression. You can also go to Radio Shack and get a noise suppressor and put it on the power line to the CB unti. Power and ground as close as you can get it to the unit.

[JohnK3]

Actually, for least noise, run the power all the way to the battery, putting fuses as close to the battery as possible on both leads. Do NOT ground the negative power lead, run it to the negative terminal on the battery. Ground the transmitter from the frame of the transmitter to the frame/body of the vehicle with as short a lead as possible. IF the antenna has a spot to ground with (ie: non-magmount), then ground it to the frame with as short a lead as possible.

[inplanotx]

Actually, for least noise, run the power all the way to the battery

Actually, this is something you want to totally avoid. This wire has to run from the front of the vehicle past the ignition system and alternator and then into the passenger compartment. A wire is nothing more than an antenna which will pick up any RF signal it passes near. It is called "cross talk". The 30,000 volts or even 50,000 volts if a newer vehicle, creates RF (radio frequency) which can be picked up by an antenna (wire). A battery is charged by the alternator which puts full wave rectified DC into the battery, but still has a small AC component. The smaller the wire used for power (12 volts, actually 13.8 to 14.2 volts if the alternator and regulator are working correctly) and ground the less noise induced into the electronics.

[JohnK3]

Hate to correct you like this, IPT, but this goes against everything I've been taught as an Amateur radio operator, what professional installers for commercial radios taught me and basic radio theory.

By running both wires, IN PARALLEL, you actually avoid making one of them an antenna. For even better protection, give them a light (1 in 12") twist to help guard against the alternator noise.

Any imbalance in a pair of wires makes the longer one become an antenna. Specifically, we call that form of antenna an "End-fed Zepp" from the way they used to use them by dangling ladderline out of the bottom of a Zeppelin. One of the sides of the ladderline would be attached to a long wire that was anywhere from 1/4 wavelength or longer for the desired frequency. The ladderline section acted as a matching section to bring the feedpoint impedance close to a match with the transmitter.

Go do some research on the subject. I've done so. Even had to pass a test on it.


From the General Class Amateur Radio License Examination Question Pool:
http://www.arrl.org/arrlvec/El3-2000.txt

G4E03 @G4E03 (A)
Which of the following power connections would be the best for a 100-watt HF mobile installation?
A. A direct, fused connection to the battery using heavy gauge wire
B. A connection to the fuse-protected accessory terminal strip or
distribution panel
C. A connection to the cigarette lighter
D. A direct connection to the alternator or generator

[inplanotx]

Morning John, God I love a good exchange of information in the morning. Gets the ole brain cells moving. First off, lets start by talkin apples vs apples and thow away those dang oranges you are trying to compare that apple to.

To start, let's do this. Since you are a general class license holder, it should be easy for you. Going back to 1965 - 66, look up license number WN2MNA and WA2IXF. The former, belonged to me with the following address:

142 Fallwood Parkway, Farmindale, NY 11735

The latter belonged to a Brother Brendan ... I forget his last name
at the following:

LaSalle Military Academy, Oakdale, NY

That was a private high school I attended. The club used the WA2IXF call sign. It was an advanced station license.

Next, we need to go to the State University of NY for 1976 and again look up my name (from the license) to see that I earned a BS in electrical engineering which I have been using ever since as a careeer.

Okay, enough drivel. I understand about a high wattage ( 100 Watts as you pointed out) RF transmitter in a vehicle. Unfortunaltely this poor fella is trying to install an under 5 watt radio transmitter that in no way shape or form fits into the class of transceivers or transmitter/receivers that we play with. This is a dinky little play radio transceiver. Hardly worth the effort and both you and I know we would bypass in a heartbeat.

Since, by law (FCC regs), that little toy is required to be under 5 Watts total output, if he runs heavy guage wire from both ends of the battery, he is not going to twist the wires 1 in 12" and he is just going to lay them side by side all the way into the passenger compartment. Except now that we are discussing this, he may have reservations. So, we now need to figure out the current to fuse this and pick the correct wire guage to mount it.

P = IE 5w = I x 12 volts
I = ~500ma = 0.5 Amps

I would bet his in dash radio draws more current. So 16 guage wire should be more than enough. I have always worked by the KISS principle due to Murphy's law always showing up at the wrong time.

Going back to your 100 watt transceiver, using the above formula, you come up with about 8+ amps. Now, that does draw considerable problems into the equation and since it is a factor of 16 times greater, presents it's own set of rules. We do not need to go there for this. Does not apply, 'D' all of the above! So no need to go your way. Using the KISS priciple, (Keep It Simple Stupid), the theory, not referring to anyone, we use as short a piece of 16 guage wire with a 3/4 Amp fuse and we are done.

Go do some research on the subject. I've done so. Even had to pass a test on it.

Not only have I participated in the enjoyment of Amateur Radio with you and passed my novice test which led me into electrical engineering where I had to pass many tests including a professional engineering test over many years, but I practice my career every day.

I used to have both the 2 Mtr and 6 Mtr Heathkit lunchbox "put it together yourself" units, but the club has a Hammerlund HQ 110 receiver along with a Johnson Viking II transmitter along with a 24 watt 2 Mtr tranceiver. Had the longest QSL with the 2 mtr rig also. From NY to Virgina. We had a trap antenna on the roof and on a cloudy day I aimed at the water of the Great South Bay, where the school was and "skipped" the signal all the way down there! Pretty good feat in 1965-66!

Always remember,

Real Amplifiers























Glow In The Dark!!

Wanna send me a QSL card? Nice chattin with ya. Have a great day!

[Nole]

well thanks for all the usefull info. I am going to try and work on it some on monday and try a differant setup with the wiring. hopefully thatll work out for me. Just one more question. I have the antenna mounted on the driver side of my truck right behind the cab on the bed rail. Is that a good enough spot for the ground plane? If not where else would be a better spot? You guys said it the best spot is on top of the roof but I cant bring myself to put it there since i am not going to be talking on the cb that much. Thanks for the wiring help. Now I just got to get the time to work on it.

[inplanotx]

Nole, your antenna will radiate more to the opposite side and in the direction of the front of the vehicle. If it were placed in the middle of a car top, then it would give equal signal strength from front to rear and side to side. It is looking for the ground plane. Since you have very little to the drivers side and most to the opposite side and back, you will radiate that way. You are also killing yourself since the antenna is trying to radiate through the cab and hitting a ground plane. I think I'm beginning to understand why your SWR is so low. You are getting a reflected wave as the signal hits the cab.

[Nole]

maybe a taller antenna? would help that problem.

[inplanotx]

Nole, the whole antenna would have to be moved over the cab. Just adding a taller antenna would not solve the problem. You might want to try a smaller antenna (1/4 wave length?), magnetic mount on the roof of your cab as close to the center as possible.

Also, look on the back of your CB unit and see if therre is an antenna matching adjustment you can make. Way back when, (70's) they use to have them to better match the antenna to the amplifier output stage. Just a thought!

[JohnK3]

Well, even given the math you threw around concerning wattage, etc. the fact of the matter doesn't change:

You will get less noise running straight to the battery, EVEN USING NON-TWISTED WIRE, than if he attaches to the nearest power-point/fuse panel/etc.

Why?

Well, let's think about it for a second. If he runs to the nearest fuse panel, he's not going to take parallel wires to it, he's going to ground the negative right where he's at and run just the positive lead to the fuse panel.

"BUT," you say, "He should run parallel wires to the fuse panel!"

Okay, so he does. Does the manufacturer of the car run parallel wires from the panel to the battery? Nope. They ground at the fuse panel and carry the positive to the nearest buss-point in the vehicle. Voila! You have an antenna attached to his transceiver. Therefore, alternator whine and other noise WILL get in, despite the best efforts of noise suppressors, etc.

Running heavy gauge wire straight to the battery has nothing to do with current draw, which is the bananas you're trying to throw into this bushel of apples, it has to do with noise suppression. Admittedly, he won't need quite so heavy wire as a 100W HF amp would need, but it should still run straight to the battery. That way, the alternator isn't anywhere near the current source. A power panel has dubious sources of power. In some cases, you might very well be recieving your electricity straight from the alternator if you get it through the power panel.

Again, this isn't just a Ham radio "Best Practices" this is also a Commercial Two-Way best practice.

73 de W5NNH

BTW: Been on the air, lately? I noticed that the WN2MNA was a Novice-class that hasn't been used in some time. Maybe it's time you got active again? There's lots of new stuff for Hams out there these days. Heck, you only need 5wpm to go Extra class, these days! With your qualifications, you should be there in no time!

[JohnK3]

Oops! Forgot something else:

I'll send a QSL if you get on the air!

[grin]

[inplanotx]

Hydra Shok wrote:

And do you have a linear amplifier?

That is a big no no! As far as I know the FCC has not changed the power out limit of 5 watts MAX for a CB radio! I know a lot of people are using detuned 10 mtr band linears, but God help ya if the FCC catches you! Good luck!

[JohnK3]

Ford agrees with me:

http://www.fordemc.com/docs/download/Mobile_Radio_Guide.pdf

[Marlin]

Who the heck is Ford?

They produced the Edsel......

:D :D :D :D :D :D :D

[inplanotx]

Well John, you win. If you are installing a commercial or higher powered mobile transceiver then your way is the correct way to go. However, in installing a toy CB radio, I have installed three in my lifetime, I have never gone straight to the battery. I used what was available in the passenger compartment and soldered in a fuseholder and away I went. Never had one problem and absolutely no noise. I consider your way, overkill for no gain with a toy radio. JMHEO.

On the other point, I have been thinking about getting back into Ham. It was a lot of fun. You are correct. That licence (we use to call them tickets) is the old way. What bands do you operate on. I used to like 10 mtrs and 14 mtr SSB voice. Dang, 5 wpm for extra class? I had to do that for novice back then. Gonna have to look up getting my ticket again. Thank for the interesting chat.
Always willing to learn and help out.

I think his problem is more antenna placement than anything else though. That would be more to your department. I hated Smith Charts in school!

;) ;)

[JohnK3]

I'm sorry, IPT, but I was responding to your claim that running straight to the battery would induce noise. You're right, it may be overkill. However, the fact remains that the recommended method for reducing noise is to run straight to the battery. I simply find it easier to run straight to the battery rather than to do it your way then have to go back and do it over again if and when problems crop up. Also, I've never had to buy a noise-suppressor when I run it straight to the battery. Cheaper.

[jlmckinney]

I was under the impression that you could use a linear on your CB if you currently held a Ham or other type license!

http://www.reactintl.org/rules-cb.htm

Rule 11 {D}

Could be wrong though.....

JM

[inplanotx]

JM, you are correct. You need a Ham license to have one though. Sorry, I should have made myself more clear. Most Hams I know do not use the CB bands.

[Hydra Shok]

That is a big no no! As far as I know the FCC has not changed the power out limit of 5 watts MAX for a CB radio! I know a lot of people are using detuned 10 mtr band linears, but God help ya if the FCC catches you! Good luck!


Actually 4 watts max is legal. Anything over 4 is a no no, even 5 :) . But the FCC has bigger fish to fry than evil cb'ers with kickers on their radios. Not to say that it's not illegal, but your odds of winning the lottery, or being struck by lightning are better than being pulled over by a roving FCC officer to have your wattage checked. Most of the ones that get busted for too much wattage are the ones who have 20,000 watt base stations that talk over their neighbors tv's and radios, ask me how I know that one ;) . The FCC didn't come, but the neighbors sure asked me about it :D .

[inplanotx]

Most of the ones that get busted for too much wattage are the ones who have 20,000 watt base stations that talk over their neighbors tv's and radios, ask me how I know that one

Okay, 20,000 watts at 100 Volts (for simplicity sake) equals 200 amps, where the common household input is about 100 Amps, tell me, do they turn off all power to the house? Inquiring minds want to know! Thanks.

[Marlin]

I'm not technical but many of my neighbors back in the 60s in Montgomery ran small kickers on their side-band bases and adjusted them wide open where they would splash on everything in the house, especially TVs and Stereos.

I found if you tuned the kicker to about 50-60% output, no one would know and you could talk all over the US.

Just a comment on an old subject.....

[inplanotx]

Marlin, until the design of comb filters, most problems encountered on home TV's in the 60's and 70's were mainly on channel 2 (154 Mhz if I remember right). This was right on the edge of the Ham Radio 6 Meter band and a minimum of 5 watts from your neighbor could blot out your TV. This was not CB radio which was in the 27 MHz area. However, if the amplifier was detuned and spurious side bands emitted, there could be problems.

[CountryGunsmith]

So let me get this right....

If I use 1/4" rope between the cans instead of that kite twine I've had since 1960, will I get better clarity?

[inplanotx]

Nope, you need 1/16th inch rope with a digital comb filter.

[Hydra Shok]

Hey Plano, most of the base stations that I have seen and the one that I had was run off of a power supply. I only had a 20 amp power supply that powered a 1000 watt kicker. I probably should have used a larger power supply, but it did the job. The lady that does my radio work has one that has a dial that she can adjust the amps. I don't know how high the amps is on it, but she talks all over the country on it. I found a 60 amp power supply on copper.com, here is the link : http://www.copper.com/cgi-bin/checkitout/checkitout.cgi?catalogSTORE:CKIE:prodT70-00032+

There was a guy a few years ago in my area that had a huge radio, called him " Preacher Boy". He would get on channel 19 and blot everyone out for miles and read scripture from the Bible. He would just key up and talk, with big pauses, then more talk. Eventually some people found his house and...... pummled him. Then someone did call the FCC and they confiscated all of his equipment. I had all of my equipment taken out by a very precise lightning strike..... devine intervention maybe? Might have saved me a whippin :D



Hmmm, i see the link doesn't work.


Fixed your link for you. .. SoMo

[Marlin]

I had a little 100 watt kicker on a Cobra side-band base back in MonkeyTown in the 60s. I talked all over the northern half of the Western hemisphere on it with regular folks in Newfoundland and Alaska. Fortunately never bled over on anyone, though.

Used a home-made di-pole antennae for part of that time strung just under the eves of the house. Nothing fancy but it did the job and did it well.

BTW, 1/8" rope worked really well for me!

[Hydra Shok]

Fixed your link for you. .. SoMo



Thanks SoMo ;)

[JohnK3]

Try 220 volts, IPT. That way, you only have to draw 100 amps. ;)


20,000 watts, however, is probably BS. Somebody's selling somebody else a truckload of manure. The person selling the amp probably CLAIMED 20,000 watts, but very few people have the equipment to MEASURE it to verify. (If the person selling says he has the instruments to prove it's 20KW, then be very skeptical. That sort of equipment is EXPENSIVE and HUGE.) If you were running 20KW, your antenna would have to be very heavy-duty and you'd need hardline to feed it without overheating. VOA (Voice of America) had a station running in Bethany, Ohio at 250KW.

Its antenna farm was pretty big. Note the size of the cables.
http://hawkins.pair.com/voaohio/voab5.jpg


This was a 50KW SSB relay station
http://hawkins.pair.com/voaohio/voab3.jpg

Those transmitters are HUGE. A 20KW amplifier would be similarly large.

54MHz is the top of 6 meters and 54MHz is the beginning of Channel 2. HOWEVER, there's lots of harmonics at 27MHz. Think about it: First even harmonic of 27MHz is 54MHz...

An illegal amplifier on CB can wipe out TV reception for quite some distance, even if you have cable. A comb filter doesn't do any good if your front end is overloaded.

(All photos came from this (http://hawkins.pair.com/voaohio.html) site.)

[Hydra Shok]

Well, this has gotten a little over what i used to have, but the 20,000 watt radio i saw is powered by a series of kickers, not one large one. Lemme see if I can explain this so that it is understood. In a kicker is a "pill", I'm not even gonna try to explain how this pill increases wattage, cause I don't know. I have a 2 pill 300 watt kicker in my dumptruck, I could get a 1 pill kicker to drive my 2 pill creating more than the 300 watts the 2 pill does by itself. The guy that did the work on my kicker builds his own for his base station, and the ones that hauls around in a surburban for when he goes to "keydowns". Now this is how he gets so many watts... he has a 2 pill driving a 4 pill driving a 8 pill driving a 16 pill driving a 32 pill driving a 64 pill driving a 96 pill kicker. Now this 96 pill kicker is about 8 feet long, 3 feet wide, and about 3 feet tall. Don't know how much it weighs, didn't try to pick it up. The power cords are car battery terminal wires, he has 5 alternators in his surburban with many car batteries to run all this stuff. In these keydowns, I'm told that 2 vehicles square off by parking a quarter mile apart, and someone else travels several miles away, I have been told 20 miles. Then at a given signal, both competitors key down at the same time and say something that will distinguish them from the other. The "judge" parked at the other place however far away holds a tape recorder and records whatever is said. Whoever blots out the other or is heard more clearly is the winner. The guy that works on my kickers has won several of these keydowns. They give the winners belts that look like the ones wrestlers are always fighting over, and he has them displayed on the walls of his shop. He competes in the 20,000 watt class, the largest. That is his mobile radio, it was a Connex 3300 last time I looked. His base station has that many watts if not more, I can't say for sure because he won't say, but you can see all the gadgets hooked together, and the same sized kickers hooked up in a series. Oh and he has a Moonraker beam antenna up on the top of his barn about 200 feet from his shop.


Not sure what all the volts, amps, and MHz means that JohnK3 was talking about, kinda over my head, but all I can say is that I have seen this stuff work, when he keys down you can hear the kickers click, starting at he smallest and working up to the largest one and watch the needle on his meter go up. Wish I knew more, but thats about it :)

[inplanotx]

54MHz is the top of 6 meters and 54MHz is the beginning of Channel 2

Sorry, hit the preceeding '1' by mistake.

[JohnK3]

Originally posted by inplanotx
Sorry, hit the preceeding '1' by mistake.

I figured, IPT. Point I was trying to make is that CB is positioned perfectly to provide LOTS of interference on Channel 2. 6 meters was mostly a problem back when the regen receiver of your Benton Harbor lunchbox was the standard for 6m. A mobile-mounted HW-29 ("Sixer") or WRL TC6 ("Tomcat") could wipe out TVs all over the place as it drove around just listening.


Now, Hydra Shok, as far as that "20KW kicker" goes...

Sounds like your buddy really is running 20KW. Based on 4W input to the first stage, that's 39dB of gain. Wow.

However, I wouldn't want to be anywhere near those two trucks when they key down. If'n they ain't sterile, any children they have after doing that are BOUND to have some sort of mutation!

Your "pills" are likely the power transistors, rather than tubes. Since it's AM, they don't need to be running linearly, so they're probably run in Class C bias. (means more electrically efficient, but worse fidelity) Those pictures I posted? Each of those has multiple stages, one stage feeding another, just like your buddy's stacked kickers.

What amazes me is that these aren't contests of skill. They're contests of who has the biggest wallet. In ham radio, we'd call them "alligators." They're all mouth and no ears.

To each their own, I guess. Some people don't understand why I fly rockets, or why I shoot, or why I talk on ham radio. So I guess I don't have to understand why people do these 'gator contests.

[Nole]

Finally got the SWR done to 1.3

I wired it straight to the battery, then took the excess coax and ran it places so it would not coil, then took of a spring I had attached and it brought it right down then took off a little from the top a presto 1.3 from 1-40 thanks for all the Help


Matt

[Hydra Shok]

Good job Nole, glad you got it done!