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ANTENNA (BRAIN RACKING) ISSUES AND THEN SOME ? WHAT'S BEST ?

Switch Kit

Switch Kit

Well-Known Member
Apr 6, 2005
3,595
135
63
1.very small car
2.Wilson 5000 roof mount
3.Cobra XL 450 (4x454's)
4.Cobra 25 LTD Classic (2 to 35)

the amp is what got me started wanting to make a few changes on my system , when I first installed this antenna matching was a problem ,I could not get a match with 18 feet of Mini 8 coax (now from what I have read over the years coax should not be a factor with SWR ?) anyway ......I ended up cutting 7 feet off the coax and the match dropped down to 1.1 to 1.2 around the band from a 2.5 to 3 with the 18 ft. Hmmm ? .....OK then ,now IM using 11 feet of mini 8 in my car and all is well ..... match through the amp is 1.2 to 1.3 ....I can live with that . (been through many amps on this system so far without any problems) now comes the 450XL ...The relays would stick on the high side (max) of the amp ....I went through different lengths of coax jumpers and finally ended up with a 12 ft jumper that stopped the relays from sticking ....but what a differance in the power readings on the meter from say a 5 foot jumper to the 12 foot jumper from the radio to the amp ? ...weird ? .....the other day i decided to change the coax on the Wilson ...(IM still not to sure what I was thinking here?) but I put a new line of 18 feet mini 8 back on the Wilson ...Match ? 2.5 to 3 just like before )-: ...just for grinnies I put a 6 foot jumper with a barrel connector and added it to the new 18 footer that I put on the Wilson ....Match with a total of 24 feet of mini 8 and a barrel connector ? 1.1 to 1.2 and just about the same through the amp on the Max side (that's without the 12 foot jumper between the radio and amp ,IM using a 3 footer now) ??????????????? ....oh ...and no relay stick ......this stuff just racks my brain sometimes ? .....IM guessing now I should more then likely just put a stright piece of 24 foot coax from the antenna ? ......or if it would even make that much differance to begin with ? On a dummy load and a 2 watt drive on a calobrated PDC 600 amp on the max side does 100 to 400 pep ........off the antenna it reads 100 to maybe 325 or so /high side reads 60 to 275 /medium side /20 to 220 /low side 10 to 200 audio watts ......is that 6 foot jumper with the barrel connector really that big of a deal for me to go back and redo the line ? or am I totally missing something here ? Thanks Switch Kit
 

I tried my best to follow what you were saying. So instead of trying to figure it all out and possibly making a mistake, lets just go back to the basics...

Antenna:
If the antenna is mounted correctly to the roof (its NOT a MM, right?), the length of coax will not be a factor. IF there is a problem with the antenna, then the different lengths of coax will affect the READING (not necessarily the actual SWR). The Wilson is a good choice! If you have access to an antenna analyzer, set up the antenna to the frequency you want to operate at and leave it alone!

Amplifier:
Make sure you have large enough wires to feed it properly. GROUND IT TO THE CAR CHASSIS somehow! As far as the radio is concerned, the amplifier IS the antenna. Most inputs on CB amplifiers are close, but may need some tweaking. Decide where the radio and amplifier are going to be mounted, get a jumper long enough to hook between them, and then have a COMPETENT tech set them up TOGETHER!. Always take your amp and radio in together!

Radio:
You have a good radio. 35 seems a bit high into this amp, but at least your deadkey is set correctly. Ground it also.

Once this is all done correctly, and you are still having problems, then there may be some grounding issues with the vehicle. Some people need to run ground starps to their doors, hood, trunk lid, and even roof pillars!

If changing the length of coax changes the readings on your meter that is set up in an unknown location, then the problem exsists elsewhere.

To check the SWR for the radio, install the meter between the transmitter (radio) and the load (amp).

To check the SWR of the antenna, install the meter between the transmitter (amp) and the load (antenna).

What looks good with the meter installed may change once it is removed IF there is a problem in the system. Good luck!
 
I'm betting the Wilson 5000 IS a magmount. I have seen this problem before. I once had a Wilson 1000 that I tried to get to work on a little car. The car just didn't provide enough of a groundplane for the antenna. Wilson recommends using a longer stinger on their website for this problem. An antenna analyzer should tell the story.

It also sounds like the input impedence of the amp may be off a bit. Messing around with different lengths of coax for the antenna and amp is basically using the coax as a matching system (or antenna tuner). You can do it that way, but it's much easier and more efficient to just get the amp's input impedance fixed and to get the antenna adjusted properly.
 
thanks for info guys ,still really ain't help'in me much ,I've been do'in this stuff for years and there's a real good chance that I have been do'in it wrong all along ? ......as I said before , the 10 foot mini 8 from the Wilson 5000 ROOF mount droped the match down to basically 1.1 and only would rise 1 or 2 clicks on the meter on many amps I've used on this system ....but as you said ,there should really be no change in SWR in my car with any length of coax ? .....so my way of thinking pretty much sucks here ? )-: I have no analizers or any fancy meters over the years and no money to pay a professional .....so all's I can really do is what I've been doing I guess, for the time being ? .....10 feet of coax works from my antenna to the radio and amp .....or at least the few SWR meters I have say so .....OK then ......the 18 foot length from the antenna is not enough for the match (2.5 to 3.5) add six more feet to the 18 feet and now I have 24 feet and the match is 1.1 just like the 10 foot length and also good through the amp (and yes Mole I tried the 66 inch stinger and it didn't help a bit with the 18 foot length) .....the only differance here is that IM now running 24 feet with a barrel connector and I NO longer have my relays sticking on the amp on the max side with only a 3 foot jumper .....Hmmmm ? .......now remember what I said .....with the 10 feet of coax from the antenna and a 12 foot jumper from the radio to the amp it would also work from keeping the relays from sticking but there seemed to be a power lose for some reason or other unlike when using a shorter jumper? ..... ...the amps relays do not stick with 10 feet of coax from the antenna and say a 3 foot jumper or less on the other 3 settings on the amp ......and yes Mole ...I do know about jumper sizes in helping in these cases when it comes to sticky relays (thanks) .......even barrel connectors can help with RF problems .....I really appreciate the help here guys ........I just don't have any money for all these special things to find out the truth ? (I only know on this small car 18 feet just won't work as far as SWR goes) .......but I would guess to say that I was more wrong then right ........oh yeah .....I never even brought up the theroy of reflective power )-: .....I guess if I should have all these other problems with my equipment ? ....I would more then likely guess to say that I would be reflecting like a sive ? )-: .......I suppose when I tried to ask these questions here that maybe I was just looking for a easy solution )-: ........well ....even though it's more then likely wrong ....and maybe it has been for many many years for me with my radios/amps/antennas ? ......IM still get'in out , (lucky I guess) .....the best I could ever do over the years is look for those special little numbers on the SWR meters .....alls I really did was take a 12 foot jumper out of line and add a 3 footer and 6 foot to a 18er ......the power looks great I would guess to say (4 x 454s at 80 watts a piece ) my numbers are in my first post which I would guess to say was pretty good off the antenna ? 100 swing 325 or so ain't bad .....and 10 to 200 on low seems pretty cool .......but face it guys .......IM living on a prayer here ......I go by what a PDC and a Realistic SWR meter tells me and that's the way it has been for almost 20 years (JUST THE THOUGHT OF REFLECTIVE SCARES ME) .......maybe it's just like the old saying ........if the SOB works ? .....by all means ..DONT TRY TO FIX IT !! .... thanks guy's I really do appreciate the come backs here. Switch Kit ........PS ....everything is grounded ,IM surprised I don't wear a ground strap around my wrist and hook it to the frame of the car
 
no need to read it again (-: ......IM cheat'in !! and for now I suppose it's just the best I can do in my situation. My box is not chattering (-: ......but hey .....you didn't need to read it again. Thanks for the half wave mulitples , I'll keep that in mind along with the antenna analizer . Switch Kit
 
Switch Kit
With out going thru what everyone else said (which are correct) I think you should really invest in a MFJ SWR ANALYZER. It will make your radio life lots simpler. It's a very valuable tool!
------------------
DXman
(Oh, by the way, I just so happen to have a extra MFJ 259B)
 
thanks DX .....after all these years you would think I was ditacated enough to have one of those by now ? ......but then again ,the more I think about it over the years the more I think I must have been more close to being right with my SWR situations in the last 6 or so cars and trucks that I owed ? In all these years I've never burned up a amp or fried a radio since I got started in 1985, as I said ....I just can't afford one of those analizers ,I live in So.Cal ...I wonder what one of the shops would charge me to hook one of those things up to my system ? and then tell me what was wrong ? ....just figuring I would have to cough up some cash just to find out what was wrong and then try and figure out how to fix the situation ? I've honestly tried to explain myself here the best that I could and I truly appreciate the advise that has been given ......wish I lived around the corner from you DX Dude .....maybe you could put your your fancy machine on my stuff and either give be the bad news or the good ? thanks Switch Kit ......oh yeah ......it's sometimes hard to be humble when your doing the best that you can in a little ole GEO METRO (-:
 
Switch Kit said:
I live in So.Cal ...I wonder what one of the shops would charge me to hook one of those things up to my system ? and then tell me what was wrong ?
Click to expand...

FG Best Communications is right here in Southern CA. They are in Ontario at the 10 and 15 Fwys. Call them up on channel 29 and they can talk you in. They will TEST your antenna, radio, and amplifier for FREE! They use an AEA antenna analyzer which is way more sophisticated than the MFJ I own! It don't get better than FREE!

On top of that, if you need your radio set up right, one of the best techs in the country works there. Ask for Justin. If his name sounds familiar, it's because he frequents this board. Their prices are fair and they back up all their work!

If you are real nice, you can ask them to see the output of your system on their Bird Wattmeters. You may even be able to watch them work on your radio and amplifier. They just don't let anybody in the back room to watch.
 
Question for Master Chief

previous message :

Antenna:
If the antenna is mounted correctly to the roof (its NOT a MM, right?)

Why did you ask if it is a Monkey Made ? Is it a weight issue ?
 
Re: Question for Master Chief

smalltiredart said:
previous message :

Antenna:
If the antenna is mounted correctly to the roof (its NOT a MM, right?)

Why did you ask if it is a Monkey Made ? Is it a weight issue ?
Click to expand...

Magnet Mount, not Monkey Made
 

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