CB SWR adjustment

[BigUgly]

Howdy to all those in TDR land;
I just picked up a Uniden PC68XL CB and a big ol' stainless whip antenna. Now before I can do any talking, the instructions for the CB tells me to adjust the Standing Wave Ratio... . they just don't tell me how! Can anyone out there please enlighten me? Is there some sorta tool or gizmo I need?
Thanks for any advice;
Josiah

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YP of SETDR
Y2K 2500, 4X4, Auto, Quad Cab, SWB, 4. 10, Black. Hot Power Edge, DTT TC and VB, Line-X, PE Roll top bed cover, Stainless add-ons. Jardine 4".

 

[The patriot]

I may be wrong, but doesnt that CB have a built in SWR meter?
Sounds like you went for the 102" whip? They are not adjustable. I'm not saying it's a "bad" antenna, just not adjustable. They are in fact VERY good, just mount it as high as you can. If you get a high SWR, you'll have to move it somewhere else and re try the SWR.
Also, if you roll up the coax, this will cause a bad SWR reading too.
It's pretty much trial and error.
Sorry I'm not familiar with that model.
Eric

[This message has been edited by The patriot (edited 02-02-2001). ]

 

[Pete Peterson]

Josiah, the 102" steel whip with a heavy duty 6 " spring is 108" long or exactly a quarter wave so there is no need to adjust it. Make sure your coax is in increments of 3 feet except 15feet. The best lentgh is 18 feet which is a half wave. Make sure the mount is bonded good to the truck and your ready to breaker, breaker!! Pete

 

[drives mopars]

hi from amateur radio land.
1st swr of 2/1 or less u will not be able to detect,i guarantee it, cb er are very swr
concerned, back in the 50's ham's did not know swr's even the space system comm

at time w/ swr over 4/1 , 2nd lenght
of coax is not a concern , only if you
are building something w/ 75 ohm as part of the antenna match, i run a antenna that covers 3. 5 mhz to 50 mhz's and can adj antenna to keep swr any where i want it to go. go to a ham store and buy a book called reflections or 50 years of hf mobiling
they r great, into detail abour swr,
to measure antenna lenght use 468/ freq
example 468/27. 095 = 17. 27 /2 8. 64 feet
this is for a qtr wave lenght. another item
on antenna gain, every 3 db gain is equil
of 2x power, power in rerf to isometric reference. like a 0 gain 0 loss system.
a 6 db gain antenna using 5 watts would take 20 watts into 0 gain ref antenna to transmit same . one more point try a field strenght meter, better than swr . finally
measure swr on a 50 ohm coax into a 50 ohm load swr will be same using any lenght of coax. one more item, there are many things that affect swr, height antenna is above ground. coax ohm,i do use 72 ohm hardline in stead of 50 ohm works great costs nothing.
ground plane size, shape, angle, metal objects, i run a elecrtic screwdriver motor
to raise and lower a coil inside my antenna
so no tuner is needed, a good swr keeps rig
cooler, but a signel of 3 db gain or loss
takes 2x power chg. u will not be able to hear this diff. a swr over 3/1 is about 10 pct
power loss, and a 10 loss is about 1 db, you
cant see thsi small of change. i can print more on this from my reading, this is a very rough draft of where swr can take you,
any questions pls contact me , good luck
bill

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1993 w350 ex cab, banks,nv 4500 in
open exaust, pw Injectors are in. Big rig flaps,tach in,. Its loud and goes ok, for a 93,Ham radio Call KK6dm
has ability to communicate any where in the world. Headliner shelf
5 antenna's

 

[drives mopars]

one more thing , dont trust the swr meter in a radio, they make swr meters that use 2 needle's called a cross needle swr meter
one measures fwd swr and the other needle measures reflected power , where they cross
is your swr. also some cb's have a swr dial
to adj meter, it sonly that, you adj meter
to far end that power out, then flip switch
to measure reflected power when meter does not move its called 0 reflected power or
flat 1/1 swr. that means 100 pct out o back
in real world coax losses prevent ever getting 100 pct out anyway. these swr meters
diawa cost about 100. 00 new many sizes.
ill have some to show in vegas , bill

 

[drives mopars]

me again, a 1/4 wave antenna cb is about 9 '
i agree mt high, but who can ? a shorter
say 50'' mounted in center of cab roof,will work better then 9' 1/4 wave mounted on bumper, a good antenna would be a 66'' chp
whip with a matching coil, i once took a
48'' whip anda cb antenna base coil and
cut coil to match w. / 48'' whip.
one other thing 2 antenna on mirrors will
never work that great, they need to be 1/4 wave apart, is your truck 9' wide. Larson
makes a nmo mount 3/4 hole unscrews
3 '' coil and 48 '' whip. that is cheap
and will work as good as anything you will find thats not a 1/4 wave.
bill

 

[drives mopars]

big ugly, if you need ill get you # for
harson antenna's or type in ameteur radio supply in web, call 1 store ask 4 a larson
nmo mount 3/4'' hole mount w/ coil and i think 48 '' whip. cost about 20$ usa,
stay away from 1/4 wave whips , to hard to mount high. my screw driver antenna is going to be mounted in 2 planes on headace rack.
other wise its 8. 5 feet high to high 4 me.
cb k 40's cost to much and dont work any better then larson, ie like B##ks turbo stuff

 

[Champane Flight]

I bought my SWR meter/rf at Radio shack for 22. 95.

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95 Dodge 2500 Luverne grill guard,headache rack,running boards and Amzoiled. Soon to be mildly bombed. 84 Dodge d-150, 318 Hooker headers,Edelbrok intake,mallory ignition,Carter Afb,Accel coil,and Custom dual exhaust. Boat,fifthwheel,motorcycles,and shop,job to support toys. Yuck...

 

[BigUgly]

Thanks for all the replys guys.
I'll hook up the CB this weekend, after I get through several other truck related chores #ad
. To answer some Q's, I have a 102" with a 6" spring with 18' of coax. The only gauge on the CB appears to be a combo RF and S signal strength gauge... is this the same thing?
Thanks again, Josiah

 

[Pete Peterson]

Josiah, If your mount is grounded good to the truck you have a perfect system. You don't need to measure your VSWR. That steel whip and spring are a quarter wave and no kind of math will ever change that fact. Pete

 

[drives mopars]

today had test, 2 cb ants on my mirrors
vrs 1/4 wave 8. 87 ' on headache rack
both received the same , but w/ 1 radio a 148 and the other a ham hf icom rig
since you cant detect less then a 3 db change , they sounded the same on recv, could
not xmit ham on cb freq.
big diff using 1/4 wave over cheap mag mount
cut for 10 meters , today i worked japan
texas ,florida, new zealand and direct
125 miles , my 1/4 wave is temp its to long
for me , if i was u ide go larson 48 to52''
for cb's bill

------------------
1993 w350 ex cab, banks,nv 4500 in
open exaust, pw Injectors are in. Big rig flaps,tach in,. Its loud and goes ok, for a 93,Ham radio Call KK6dm
has ability to communicate any where in the world. Headliner shelf
5 antenna's