SWR BETWEEN RADIO & DRIVER & AMP & HOW DO YOU S

[Watermelonman53]

OK I'M FAMILIAR WITH SETTING SWR ON MY ANTENNA HOWEVER YOU CAN HAVE A HIGH SWR BETWEEN YOUR RADIO AND DRIVERS AND OR AMP(S) . I'M READING THAT THESE ARE AS CRUCIAL AS YOUR ANTENNA. NOW GIVEN THE COMMON PROCEDURE FOR ANTENNA ADJUSTMENTS HOW DOES ONE COMPENSATE FOR TRIMMING BETWEEN THE RADIO AND AMP OR IN SOME CASES THE RADIO AND THE DRIVER AND THEN THE AMP?? TRIMMER/VARIABLE CAPS ON THE FINALS?? COAX LENGTH? I KNOW IT WAS DONE ON ONE OF MY OTHER TRUCKS SOME YEARS BACK BUT I CANT REMEMBER HOW THEY WENT ABOUT DOING IT. THANKS FOR THE ANY SHARED INFORMATION.

[Alabama Redneck]

Well I dont know about anyone else, but I always just set the swr on the antenna by adjusting the stinger or whip. As far as caps and what have you, dont know a thing about them. Coax length wont actually adjust or change your true swr, just give you a false reading, or a feel good reading.

[the_junkie]

Well I dont know about anyone else, but I always just set the swr on the antenna by adjusting the stinger or whip. As far as caps and what have you, dont know a thing about them. Coax length wont actually adjust or change your true swr, just give you a false reading, or a feel good reading.

ditto...

just set em, get em as good as you can, and run with it

[The Breeze]

I was told to set the swr and then turn the amp on and do it again by a very trusted source. This with the meter placed last in line between the amp and coax. I have also heard to just set it with amp off and let it run as that. I have new coax coming and will try the amp on method then and see what I can do. As it is, with amp on I am getting high swr's, with amp off I have a 1:1, or flat line on most channels. I don't know what it will do to the swr's if I set it with amp on, and then run the radio with the amp off. I don't always want to have it on. I too would like to see what others have to say.

[Midlander]

Well I dont know about anyone else, but I always just set the swr on the antenna by adjusting the stinger or whip. As far as caps and what have you, dont know a thing about them. Coax length wont actually adjust or change your true swr, just give you a false reading, or a feel good reading.

I agree with his post too.

[jessejamesdallas]

Yep...just set your SWR as low as you can get it by adjusting the antenna's stinger, and be done with it. With some Amps, when you turn them on, the SWR reading you see on your meter may go up some, but thats normal because of reflected harmonics from the Amp, back into your SWR Meter...You can add a Low Pass Filter right behind the amp, that may help your meter read lower if you are that concerned about it. A Low Pass Filter will help reduce the harmonics from the Amp, that is messing with the SWR Meter.

If you go with a Low Pass Filter, then get one of those L-Bow connectors, so you can just hook the filter right to the back of the Amp where the coax from the antenna would normally be connected. Then hook the coax to the other end of the filter going to the antenna (or meter)

[Watermelonman53]

OKAY .....THANKS TO ALL FOR THE INPUT HOWEVER PLEASE REFFER TO THIS SITE.....motormouthmaul.com ....I REMEMBERED AFTER I POSTED THIS THREAD WHERE I HAD SEEN IT. JOHN RUNS A ANTENNA TUNER BETWEEN HIS RADIO AND AMP TO MATCH IT UP. NOW THIS GUY (JOHN) HAS A MAJOR SETUP IN HIS MOBILE AND IS A HIGHLY RESPECTED AUTHORIIY BOTH ON THE SUPER BOWL AS WELL AS ANY CHANNEL HE KEYS ON. KNOWN AS THE VOICE OF THE CENTRAL COAST ON THE BOWL. TAKE A MOMENT AND TREAT YOURSELF TO A GENUNE CLASS BROADCAST STATION.. DONT TAKE ME WRONG YOUR METHODS ARE CORRECT ALSO. IM JUST TAKING IT TO THE NEXT LEVEL.. OH AND BTW IT WAS CLAYS RADIO SHOP THAT CHECKED AND SET SWR BETWEEN RADIO AND AMP BUT THAT WAS 16YRS AGO.

['Doc]

Think about just exactly what SWR is. It's a means of determining if the output impedance of the radio is the same as the input impedance of whatever is next in line, amplifier or antenna. The higher the SWR, the worse that impedance match is. Since the nominal output impedance of a radio is 50 ohms, that means that whatevers next usually doesn't have a 50 ohm input impedance. (That assumes that the cable connecting the two is also 50 ohms, naturally.) If that next thing in line is an amplifier, and if it's a typical CB amplifier, meaning that it doesn't have a variably tuned input, then it isn't built correctly. (There may be some adjustment 'inside' that box, but if you don't know what you're doing, leave it alone.)
Same for the SWR between the amplifier and the antenna. That assumes that the antenna's input is 50 ohms. If it isn't, then tune the antenna. Aftr tunning the antenna for a 50 ohm input, or the lowest SWR possible, and the SWR goes up when the amplifier is turned on, the the output of the amplifier is at fault. Since all CB amplifiers use a 'no-tune' output circuit, no loading controls, it's a very common thing and typically a fault in design.
Trying to tune anything by means of feed line length is silly. Coax was never designed to do that, just isn't very good at it. The example given of someone using a tuner between radio and amplifier is one 'right' way of doing it. Having that 'tuner' built into the back end of an amplifier was normal before people got too lazy to twiddle knobs to get things right. that knob twiddling also compensated for every setup not being exactly alike, but having typical differences which are entirely normal too.
If you want 'plug-n-play' then you'd better count on 'plug-n-praying' a lot. Or just learn how to twiddle knobs...
- 'Doc

[Four]

ok... with what i have gathered from these postings.. i can run my linears with a short 1 or 2 ft.. jumper... i would prefer to set my amp closer to my radios.. i have been told to run 6-9 ft. between teh radio and amp... sure would be nice to get it closer

[The Toolman]

My radio to amp jumper length is around 3' an the swr at 40 is 1.3 an 1.1 at channel 1

Ron
ol'**Censored**

[721HACKSAW]

Doc is correct on this one. I have a couple of old sweep tube amps that are 30+ years old, but they have trimmer pots for adjusting the impedence between the radio and amp.