reception problems

[cajun]

Originally Posted by kd5drx

That explains allot about it. Check your grounds real good and run more grounds then check the coax and make sure it is in good shape. Then of course you have already double checked your radio setting like the RF gain and stuff but double check and make sure it is all where it should be. Then from there i would have the radio receive sensitivity checked.

yea, mack explains a lot but when i had the older truck i had the same antenna on the mirror bracket because that truck had vent windows so i just ran the coax thru the vent window. i also had to ground the antenna bracket because the mirror brackets on these macks won't ground. when i got the new truck i checked the slider bar with my ohmmeter and it zeroed out so the slider bar is grounded, i may need to check that again though.
thanks guys

[Carolina Thunder]

#1.Try a different antenna. The Wilson transmites and receives off of the entire length of the antenna and with the amount of metal that is surrounding the antenna it may be messing up it's radiation pattern. I use a 5 and a half foot Wilson silver load antenna and talk 50 to 60 miles on a regular basis with only a Connex 3300hp. This antenna only works off of the tip of the antenna so there for as long as it is above the cab/trailer then you will not have any interference.

#2. Try another radio. If the problem is gone then there is something internally wrong with your radio. Could be a cold solder joint.

#3. Get rid of that coax that you have now and use WHATEVER LENGTH you need to make it from the antenna to the radio. Don't even worry about the old use only 18 feet of coax deal. That is only an urban legend. This is a little long but read on and see what i mean.


There is a misconception among CB operators that changing the length of your coax can "tune" your antenna system. This is absolutely untrue! This short discussion will detail why.
The coax cable is a means for transferring your RF signal to the radiating portion of the radio system. The cable, in theory, is meant to be a contained, non-radiating link. Because it does not radiate and serves only to transfer RF between two components of the transmitter system, it's performance in terms of efficiency is affected by length, but only in terms of overall resistance. In other words, using a long run of coax will reduce the total amount of signal at the antenna, but only because of loss due to resistance and NOT because of standing waves.
Ideally, you want to check the SWR of your antenna at the antenna feedpoint. In a perfect world, this is the best way. However, we all know that this is ludicrous to expect in a standard base antenna installation. Unless a remote SWR meter head is incorporated, we usually use the standard SWR meter located at the radio. The drawback is that resistance and slight impedance mismatch of the coax affects the overall SWR reading.
Because radio waves are tuned wavelengths of energy, we have to take into account the coax cable length. A typical 11-meter signal has a basic wavelength of 36 feet/wave. "Tuning" the coax for the exact full wavelength tends to throw off the SWR meter by not allowing any standing waves to return to the meter. Excess RF on the coax has been given an ideal medium by which to "hide" electrically from your SWR meter. That is not to say that the excess RF is not returning to the radio, you just can't see it on your meter.
What we want to do is create an environment where any excess RF (standing waves) are rendered as visible as possible to the meter. This is effectively done by using multiples of the 1/2-wavelength of the radiated signal. One half wave for the 11-meter band is 18 feet. However, this is not the length that you will cut your coax. There is another factor that affects the length. This is Velocity Factor. The velocity factor is basically a term for how fast the signal moves through the coax. This factor affects the overall electrical performance of the coax and thus needs to be accounted for when determining the true half wave length


Here are the velocity factors of the various Belden coaxial cables:
RG-59 .66

RG-59/U (foam) .79

RG-58 .66

RG-58/U (foam) .79

RG-8A/U .66

RG-8/U (foam) .80 9913 .84

RG-213/U .66
Here is how to figure out your true 1/2-wave:
492 x (Velocity Factor) / Frequency (MHz)
For example, I want to figure out the true half wave coax length for RG-59/U (foam) on my home channel (ch. 33 - 27.335):
492 x .79 / 27.335 = 14.219 feet
Now add 14.219 to itself to determine your 1/2 wave multiples. Remember to use every other number. See the example below:
14.219 feet 1/2-wave multiple, 28.438 feet 1-wave multiple, 42.657 feet 1/2-wave multiple, 56.876 feet 1-wave multiple, 71.095 feet 1/2-wave multiple, 85.314 feet 1-wave multiple
and so on . . . .
Use only the lengths that fall on the 1/2-wave multiples and you will be all set.


Now in order to get the true SWR of the system, you have to throw away that 3-foot jumper cable for now. The SWR meter has to fall on a 1/2-wave point on the coax run. Using the example above, you need a 14.219 foot jumper from the radio to the SWR meter, and a 1/2-wave multiple length from the SWR meter to the antenna. If my antenna is 65 feet away from my radio, I need a 14.219 foot jumper from the radio to the SWR meter, and a 71.095 foot length between the SWR meter and the antenna.


In laymans terms, the coax length fools your SWR meter into thinking that your SWR is different to what it actually is !
The ONLY way to know what your SWR actually is, is to use a correct length of coax for the operating frequency
-------------------------------------------------------------------------------So if you dont want to do the math you would want around 24 feet of coax and then you want to re tune your antenna with the now correct length of coax to get you SWR down to under a 2.0. Set your SWR with out the box on! If you see that when you turn the box on and the swr jump up dont sweat it. It's just excessive harmonics from the amp that is causing this, you wont hurt a thing!

The magic 1.1 is nothing but a wast of time as no one will be able to tell that by listening to you talk that your swr is 1.1 or 2.0.

[BobC]

Now why would I use RG59 to my base antenna?
It's 75 ohm cable.
My swr would be wrong before I even got started worrying about the lengths.

[Carolina Thunder]

.......as i said i got most of this from the net so take it for what it's worth. I did see that myself so it had me scratching my head as well but even if there are a few contradictions the majority of information is still helpful.

[thetez]

you know it doesnt make much sence to me why you need 59 for your base. but i use it {for my side band base station) and my SWR's are flat.... (ah ha no not just on the side band frequencies) its what you want for base.

[kd5drx]

Well allot of hams use short pieces of rg59 as a tuning stub it all depends on the impedance at the feed point of an antenna. In the CB world you use mostly 50 ohm antennas so it doesn't make much sense to use 59 unless your co phasing a set of antennas then its the best to make a co phase harness. But in the ham world where you run allot of wire antennas the impedance at the feed point is usually high around 300 or 400 ohms so a piece of 59 cut to a 1/2 wave figuring the velocity factor in makes a good tuning stub to bring the impedance down to a more reasonable match for the tuner to work with.

[BobC]

Under average base station & mobile station single antenna conditions, it probably doesn't much matter if you use RG59(75ohms) or RG58(52ohms).

Unless you buy the better cables, each of these cables mentioned can be off in their respective impedances by a bit & no one would ever know.

Sometimes you'll see a variation in cable impedances by more than just a few ohms either way if you have the equipment to actually check it. I do.

The bulk of swr concerns are overkill as well as the magnitudes of effort some expend in reporting ways of obtaining the illusory 1:1.1 match.

In the general case of a truck setup, you don't have enough metal around the antenna to provide even a fair groundplane to work from.

In this case, you end up tuning the antenna to disguise the fact of having a poor groundplane.

The end result is a suitable swr reading but....you've actually detuned the antenna from being resonant at the cb fequencies to introduce enough of the required opposite reactance to make the meter happy.

Better to invest the effort into making/finding the better groundplane for the antenna to work against than to worry about making the meter happy.

If you make a good groundplane around the antenna, the meter reading will fall into the proper place on it's own.....unless you really messed the antenna up by cutting it to much.

[cajun]

thanks for all the suggestions guys, yesterday i noticed when i was talking to a guy i had met going the opposite direction. i couldn't hear him talking very quickly. maybe a mile apart but i looked at the meter on the radio and he was still swinging the meter over halfway across but yet i could barely hear him. i've checked the rf gain and it's all the way to the right. doesn't make any sense to me.

[Carolina Thunder]

This may sound stupid but give the radio a hard tap and see if the ears come back. It sounds like a cold solder joint to me.

[thetez]

oh.... woops im wrong.... sorry no ... i got 59 and ru 8x confused.... 59 is only to be used with co phase .. its what i use and it works great... rg 58 doesnt work. 8u is whats used for base. its thick wide heavy stuff