CB Tuning

[Tay-Lo]

Well I finally got around to checking the SWR of my setup....and well.....it's not good. I can't be the only one with thats had this problem. My SWR will not go below 5 either I'm not using the meter right or there's a serious issue with my setup. My current setup is as follows:

Radio - Midland 75-822
Cable - Firestik 18 foot
Nut - Firestik
Antenna - Firestik Firefly
Location - where the factory antenna is.

When I put the washers on the nut is the recommened order I get an SWR of incredibly high (top to bottom mouning nut, lock washer, washer, plastic washer, mounting surface, threaded connector nut) but when I put the plastic washer on the bottom side of the mounting surface I can get an SWR of 5-10.

I know the antenna is grounded the 2nd way because of a light tester I have (I might end up using a really expensive Fluke from work to findout just how well) I have checked it with the cap on, hood closed and doors closed in an open area. The extra coax is wadded up under the dash, I know if its coiled up can affect the reading but I wouldn't think that much.

Any advice on what to do or check? I have tomorrow to play around with it then it'll probably be 2 more weeks till I can see my baby again.

 

[Tay-Lo]

Bump - because I would like to try and get this fixed today

 

[TJTJ]

Its not the electrical ground per se that impacts the SWR though...its the ground PLANE primarily.

Factors such as the way the excess cable is routed make more of a difference. Anything over ~ 3.5 or so is very bad and can start frying things when you key the mike.

Is the ant cable coiled to take up the excess length, etc? Describe how the cable is situated and routed.

Describe the procedure you use to measure the SWR (In detail).

Are you measuring in your driveway/near other rigs or buildings, or out in the open?


If the order of nuts, etc, changes the effective length of the antenna, that will change the SWR.

If you measure on channel 1 and then on 19, the difference can tell you if you are too long or too short...so post that info if you have it.

 

[Tay-Lo]

Its not the electrical ground per se that impacts the SWR though...its the ground PLANE primarily.

Factors such as the way the excess cable is routed make more of a difference. Anything over ~ 3.5 or so is very bad and can start frying things when you key the mike.

Is the ant cable coiled to take up the excess length, etc? Describe how the cable is situated and routed.

Describe the procedure you use to measure the SWR (In detail).

Are you measuring in your driveway/near other rigs or buildings, or out in the open?


If the order of nuts, etc, changes the effective length of the antenna, that will change the SWR.

If you measure on channel 1 and then on 19, the difference can tell you if you are too long or too short...so post that info if you have it.

Route - From the factory antenna location into the passenger door, under the dash to between the drivers seat and center console.

Excess length - was just bunched up kinda under the dash in the passenger floor board but is laid out now to check that. Seemed to help a bit.

Procedure - switch in FWD, Key the mic, set the dial, change to REF (this is how the instructions say)

Location - both, I've tried in the open but didn't get a different reading yesterday.

Channel SWR - The lower channels get a slightly lower reading more easily.


NOTE*****

I've been messing with it a bit this morning. Depending on how I hold the radio I can lower the SWR by about 3....but not in comfortable ways and can now get a common reading of 3 and often 2.5. I'll be in a parking lot later where I can get away from everything and check it out there.

What is really throwing me off is being able to drastically change it by holding it certain ways....

 

[Tay-Lo]

Update

After taking Nismos suggestion on how the cable was run and check an open area and was able to get it down to about 1.2- 1.3 depending on how I held it. But if I just held it like one normally would it was about 2.5.......Still weird how it changes depending on how I hold it. I'm thinking maybe a radio ground. I won't have time to run a new ground until I get back in a couple of weeks. If that doesn't work I'll run a ground from the mount to the battery......

 

[mudchet]

If your SWR meter is that sensitive to where you hold the CB it would make me think that the antenna is somehow not connected correctly to the CB. I would try swapping out pieces of your antenna setup and rechecking your SWR reading. For example, using an extra antenna cable, run it from your CB to your antenna by just looping it over the seats, etc. If you get the same reading, borrow a different antenna, and hook it up to your cable without the mounting bracket. Check again.

The extreme version of this is to pull the CB from the car, connect it to an antenna, and power and ground it with connections that you can guarantee are 100% solid.

HOpe this helps.

 

[Tay-Lo]

If your SWR meter is that sensitive to where you hold the CB it would make me think that the antenna is somehow not connected correctly to the CB. I would try swapping out pieces of your antenna setup and rechecking your SWR reading. For example, using an extra antenna cable, run it from your CB to your antenna by just looping it over the seats, etc. If you get the same reading, borrow a different antenna, and hook it up to your cable without the mounting bracket. Check again.

The extreme version of this is to pull the CB from the car, connect it to an antenna, and power and ground it with connections that you can guarantee are 100% solid.

HOpe this helps.

Thanks for the advice. I've actually gotten a better tuning now 1.5 - 1.7 holding it normally and dead on 1 against my chest. I could have parked in a better spot to tune it so the readings might be a bit lower even. Since its within an acceptable reading I'm not going to worry to much about it. Though I still have to put the splitter on to use the antenna with the am/fm radio and I'll have to tune that too, at least thats easier to do.

I've begun to think it has something to do with it being a Midland 75 and the fact it can have an antenna directly on the unit might change the SWR.....maybe. I haven't really tried to tune my magnet mount antenna to see if it does the same thing, I bet it does.

 

[TJTJ]

IIRC, there''s a jack connection, and if its loose or the wires inside are frayed or stretched, etc...it could cause trouble...on the CB end or the firewall end (If that's where you put it, etc..)

You DO need to be far from buildings, etc....and otherwise, your body may be blocking or "Planing" signal interfered with by close structures, other igs, etc.