CB with 3.75 SWR [Archive] - TheDieselPage.com Forums

TxDoc

10-05-2002, 01:08

I have FireStik Fire Ring 9 foot coax, FireStik FireFly 300 foot antenna, Uniden CB, and the antenna mounted in the corner of the body (just in front of windshield at the edge of the hood a'la SoMnDuramax desgign.) smile.gif

The part of the FireRing that should be grounded is, and the other side is not. The SWR reading on channel 1, 40 and 19 are all about 3.75 with the load screwed down and a little higher when screwed out.

I can hear at least 5 miles, but others cannot hear me so well.

I am guessing that without a good ground plane beneath the antenna and since it is not at the highest point, that may be a problem.

I maninly use it for monitoring and not shooting skip. Just wanted to see what theories may be out there on the sky high SWR results.

Paintdude

10-05-2002, 06:53

I know very little about CB tech stuff, but I have one in my truck...use one of those glue on through the glass antennas and it works for a mile or two vehicle to vehicle (My best guess). monitoring the truck smokie talk and communicating with truckers for lane changes at times..Works great for me...

Stage 1

10-05-2002, 07:52

Hi Paintdude,

Where did you purchase your window glue on antenna and do you know the brand? Previous truck had same type of CB antenna from Radio Shack, I was not real happy w/the recpetion/transmiting capability. Received incoming signal for about 1/2 to a mile, and could transmit for about 1/4 to 1/2 mile depending on how hilly it was. Because of this problem I would go back to using an old style temporary magnetic stick on antenna (placed it on the center of the roof)when traveling with a group on long trips where we needed to communicate a lot.
Not sure why my window stick-on work so poorely, I had it intalled on a side window and it did not extend above the top of the vehicle. This may be part of the problem since the cars and trucks w/professional installations seem to all have roof installed antennas at a high point. Just as a note, have the in front of windshield at the edge of the hood SoMnDuramax design on 87' 2500 and it works good.

Thanks for the information,

chevmeister

10-05-2002, 08:44

Txdoc, check to see if your bracket is grounded. if you have a multimeter check the ohms of resistance. You may have to scrape the paint off where its mounted. That is usually the only problem. I had one mounted on the bumper of my jeep. never effected swrs. i dont think is mounting height. but ive been wrong before. Ive installed 50 or so cbs in my short life. If you want a good antenna and arent afraid of drilling Wilson makes a great throught the roof mount. I had one on my 99 1500 (see pics). Ive never had to adjust a Wilson 1000 roof or magnetic mount 1:1 match every time

denverdale

10-05-2002, 08:46

TxDoc
A SWR of 3.75 is way too high. Besides not being able to transmit very far, you stand the risk of burning up your finals in the radio. Are you sure you are using a good SWR meter to take your readings? You should try to get the SWR down to 1.5 or less.
Denverdale

mdrag

10-05-2002, 13:21

TxDoc,

I agree with chevmeister - make sure you have a good ground on the bracket/bolts. You may need to run a heavy gauge wire from the bracket to a good ground.

[ 10-05-2002: Message edited by: mdrag ]</p>

Paintdude

10-05-2002, 18:12

Stage1, bought it on EBay...have seen them at truck stops before..have mine on the rear glass..works really good for me.. smile.gif

This looks just like it.. have had mine a few years..

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1384823871

[ 10-05-2002: Message edited by: Paintdude ]</p>

TxDoc

10-05-2002, 19:18

Checked the ground and what is supposed to be is 100%, and what isn't supposed to be isn't.

The trouble was this:
I would adjust the SWR and get channel 1 and 40 down to 1.8 or so and channel 19 down to 1.3-1.6. Then after I replaced the protective top vinyl cap, the SWR would be back to well over 3.

So, I started over and after each adjustment of the top load and before checking the SWR on channel 1, 40 and 19, I would replace the cap. That solved the problem. Now, I am at 1.3 on channel 19, 1.8 on channels 1 and 40. I guess that cap makes more difference than I would have ever expected. I talked to two base stations, one 15 miles away and one about 10. So, I am happy with that.

Thanks for the help. If you have a FireStik and are tuning the SWR, replace the cap while checking.

Stage 1

10-05-2002, 20:08

Paintdude,

Thanks for the link. Does yours have a buldge in it or is it all one piece of wire. Mine was one piece of wire w/height of about 12 to 14 inches. total length of wire could be 24 inches because part of it was coiled. Checked out your pics, it looks nice. I will likely put one on the back window also.

TBC

10-05-2002, 20:29

TXDoc
You did what I was going to recommend. Ran into the same situation when I had mine installed. The radio shop tech realized the cap made a difference.

I tried the glass mount antenna and I could not talk to anyone. It is going back to Radio Shack tomorrow. The CB shops I talked to said that occasionally one will work but not well and most of them never work. One shop got mad when I called to talk about it and said they should be trashed and prohibited from selling them.

Had a firestick mounted to the left front corner of the bed and it works better than any setup I have ever had. The litte Uniden is a great radio and it is mounted in the console slot where CD's are suppose to go. The speaker is on the dash in the driver side corner of windshield. It is a 2 1/2 inch square speaker I got at a truck stop.

Paintdude

10-05-2002, 20:38

The one on Ebay is just like the one I have..All i can say is it works for me..Good Luck.. smile.gif

Jomar

10-05-2002, 20:41

TXDOC, I had the same problem when I installed a Firestix antenna on my truck, so I just left the colored cap off. Do we really need it????

Jomar

chevmeister

10-05-2002, 21:15

About your cap...... you dont need it. One word of caution if it was humid when you did your check, its not gonna stay accurate. It cost me two radios to figure that one out. I have pc 76s or pc 78s with twin 3' wils in every truck, and the caps make good extentions for the volume and squelch knobs. :D

Maverick

10-06-2002, 00:50

I am running a Wilson 1000 also and like it. Your 9' of coax is 9' short. In an ideal setup you should have 18'. If you have excess cable you should route the cable so it is spread out. If you put it in a bundle and tuck it under the dash, it will hurt the performance of the radio. But if it works as good as you say, I would leave it alone.

3-Fan

10-07-2002, 09:25

I have my Antenna mounted just like TxDoc per SoMnDuramax and have ran into a little problem too. When I que the mic, it makes my SPA DG-211 gage (EGT side only) jump up to 1800 degrees. A little odd I think. Could this be a grounding issue too? I know hardly anything about using a Multimeter to check if it is properly grounded or not, how would I do that??

Thanks!!

TxDoc

10-07-2002, 10:16

Set it to Ohms to check resistance. A reading of 0.00 is zero resistance--a good ground. Some meters read 1 or show an infinity sign for high resistance and a bad ground.

chevmeister

10-10-2002, 20:20

3-fan
Is your radio off the shelf? You didnt modify it did you. May the coax be laying on the sending wire for your egt guage. I know my radio, when I installed it in my 1500 would talk over my subs and I had to run a better ground. But then my radio came across the bench before I got it. Yet to get it in my Dmax. Hope to soon. Anyone have a drawing of somnduramax's bracket? I might go that way.

TxDoc

10-10-2002, 21:12

Chevmeister, email me at TxDoc2@removethisAOL.com for the drawings. I emailed him and he okayed it.

3-Fan

10-11-2002, 06:00

chevmeister,

Ya, I'm sure my EGT sending cable is laying on my coax cable. They both come through the firewall at the same location. Guess I'll have to find a new place to bring one of them through. I think this might also be the reason my CB goes haywire when I turn on my XM Radio. It comes through the firewall at the same location too.

THanks for the help!!

hoot

10-11-2002, 06:34

I mounted a CB antenna on a 1989 Chevy Stepside, on the front bulkhead of the bed.

I could not get a good SWR. It turns out the mostly fiberglass bed was a poor ground plane. I added extra ground straps from the bulhead to the frame but it didn't help.

I have given up on bracket mounted antennas. Thebest setup is drilled through the roof. It's as high as you can get and has the best ground plane.

I used a Wilson K1000. It comes with a screw on weather protection cap if you unscrew the antenna.

It has no effect on resale whatsoever if that's anyones concern. Nobody will be deterred from buying a truck because of the antenna mount.

Here's my '97 with the Wilson....
http://onramp.uscom.com/~hoot/cars/97HD/97angle.JPG

Here's the '89, before I put the antenna on....
http://onramp.uscom.com/~hoot/cars/89ck1.JPG

Pizza Man

10-11-2002, 13:43

Truck stops on the highways usually have a good CB Tech. Thats where I take mine...they can even "tune" your CB so it works better.

[ 10-15-2002: Message edited by: Pizza Man ]</p>

GBurton

10-11-2002, 20:58

Some comments to share.

1)Contrary to popular folklore, the length of the coax cable between a properly designed antenna and your radio does NOT matter other than it has to reach between them. I know that some of you will want to argue with that statement but let me explain. Most radios that use coax cable are designed to use a 50-ohm (impedance) antenna. If the antenna is really a 50-ohm (impedance) antenna (don

Kennedy

10-14-2002, 22:10

This also applies to cell antennas. Hole mounted through the roof is the absolute best.

I have a Galaxy Mirage 88 (and a GII) that I should put in the truck, but needs a cold solder joint fixed. The Mirage is supposed to be good for 20+ watts on AM. I like the talkback/echo feature used in MODERATION as it adds a boisterous tone to the audio. Haven't actively used the CB in years, but i tell you, a good sounding radio gets any question answered if there are truckers in the area. Audio that sounds like you have your nose plugged is a different story...

Pizza Man

10-15-2002, 10:33

To help anwser the original question. I think that the 9' cable is to short. 18' cable is recommended for most radios, 3' increments is recommended. Swr should be 1:1. Adjustments in the whip in 1/8" increments is how you tune the radio coax and antenna. The ground is very important. A good truck stop cb technician can tune your radio and will make sure it is working properly. Usually for minimal money. And some will even offer to talk to you as you drive away to see how the radio sounds. So you can see how far (in miles or km) your radio is putting out or receiving.

I am not licensed with the fcc nor do I work for the fcc. I just drove 18 wheelers coast to coast and always used my cb.

Stage 1

10-15-2002, 15:17

George,
Thanks for all the information in your reply. Can you expand a little more on the new radio capabilities to block out noise from diesel injector system. Specifically which radios block this noise and/or what specification and values should you look for to do this?
Also, what is the effect of this noise? reception and/or transmitting quality.
thanks,