TPilaske

well... I went and ordered a new Firestik antenna and some new coax, connectors, mount & insulators... so now I'll basically have everything new, including a new CB... should have the stuff tomorrow... prolly won't mess w/ it until the weekend though... If this don't work... I guess I'll just listen to the traffic on there and never transmit anything...

Thanks for all the input!


Tony

Commatoze

It probably isn't. In theory, and as HiD stated earlier, a pure 1/4 wave vertical radiator over a perfect ground yields an input impedance of 35 ohms creating a built in VSWR of around 2:1. This is physics and it can't be altered. Note the word "pure". By that I mean no loading coils or capacitor hats; just a good ol' 1/4 wave whip. The antenna manufacturer "assumes" your installation will not have a perfect ground under the antenna. So, you'll have built-in ground losses which raise that 35 ohm figure up a bit. The closer you are to 50 ohms, the better the VSWR looks. But, that doesn't mean you're radiating effeciently. It just means your radio is "looking" into a 50 ohm load and is happy. It's quite possible a lot of your signal is going up in heat and little is being radiating. If your antenna is tuned correctly and you have a good return path, ie. "ground" under the antenna but still have a VSWR of, say, 2:1 your antenna is still around 89% efficient and most importantly, yielding good power transfer. In general, SWR tells you NOTHING about your antenna efficiency. Thse rules apply whether your antenna is on your house chimney, on a pipe in the back yard, or on the bumper of your truck.

TPilaske

Well... I don't know exactly what it was, but my SWR seems to be in check now!

I basically got a new Firestik Firefly Antenna, New FireFlex cable & I ended up moving the power for the CB over to the other battery where nothing is attached.

This is what I got w/ the SWR Meter after calibrating:

Channel 1: The meter went from 1 to 1.2
Channel 19: The meter went from 1 to 2
Channel 40: The meter went from 1 to 3 (???)

The antenna has a tuneable tip, so I'll prolly mess w/ it more this weekend to see if I can get 40 down... I pretty much only run on 19, so I'm really not too concerned. I may mess with it this weekend and see if I can fine tune it some more!!

I appreciate all the input!! Phox, the beers on me if I ever meet you! I really appreciate you taking the time to take the pic and illustrate it!


Tony

Mexstan

Haulin_in_Dixie and Commatize, both of you made sense to me.
One thing that is often missed with any coax, specially coax with connectors that the owner has installed himself, is as has been mentioned, the possibility of crud or a stray strand of the shielding poking into the connector. I have found that a quick and dirty method to check any coax is to disconnect it from both ends and then measure the resistance with the highest reading ohm meter you can find. ANY reading is cause to suspect a problem in the section of coax. It MUST read as a totally open circuit or else you can be guaranteed of problems such as high SWR. Another thing that can be done to check the coax and the ground is the connect ONE end of the coax and then at the open end measure the resistance of the shield to ground. That should show as a dead short. Then disconnect the cable and connect the other end and repeat the test. Unless both ends show as a dead short, you could have problems. This last test does not work with a dipole antenna, only antenna's with one side grounded to the vehicle.
Please note, the above are not accurate scientific tests, but only quick and dirty tests to give you a rough and easy guide for possible problems.

phox_mulder

No problem.

Just be glad you don't have duals.

It literally took me an hour to get my tips adjusted just right.
Then when I got them both down as good as I could,
I put the rubber caps back on and the SWR jumped back up again.

Take the caps off, adjust back down, put caps back on and check,
caps off, more adjustment, caps back on, good enough.
I'm sure I could get mine down even more,
but I really don't want to mess with it until I get my CB moved to the cup holder space.


phox

Haulin_in_Dixie

Actually the complete test is to put the SWR meter at the radio and put a 52 ohm resister at the antenna end of the coax. You should get 1 to 1 or very close. This eliminates the radio and coax from the list of possible problems.

The resistor comes out to five one watt resistors of the right combination for 52 ohm. They can be soldered to a pl259 connector.

Mexstan

Haulin', you are correct. The resistors you describe is what is known as a "dummy load". ( I have an oil filled dummy load can here for higher power.) However you can't do that unless the coax is known to be good and the rough test I described is the prelude to the dummy load test. If the coax is bad in any way, even with a proper 52 ohm load at the end of the coax, the SWR readings will be way off.
Tuning an antenna can be a pain and it is sometime surprising what little adjustment in length will do. I have found that a top hat will sometimes help in broadening the bandwidth for close to 1:1 ratio. There is less of a peak.

Haulin_in_Dixie

I have the Drake solid state dummey load here that will take about 2500 watts for the higher power stuff. I was trying to give him something that he could obtain and use for the cb.

Years ago I built the 5 watt load out of resisters for the cb checking. I have had it with some heat up to 25 watts or so.

Generally I would put the swr meter at the radio, load on the swr meter, that would check the radio for 52 ohm, then the coax on the swr and the load on the coax, which would check the coax, then you are only left with antenna tuning or problems depending on what kind of antenna.

I was cheap with five kids, used to take a plain cb wire whip, cut it for about 77 inches to start and cut it till I had about 1 1/2 to 1 for 2 meter, made a good 2 meter 3/4 wave that worked well.

Always tuned up the tuners off the air with the load than switched to the antenna, the Drake 2000 was great for that with the built in swr and output meter.

I ran a TR7, Dentron supertuner, Dentron SWR, and 42 foot of wire on a flat bed truck for years, random loaded. Worked great especially on 40 meters.

Mexstan

Haulin, you bring back memories. I still have my old Heath Cantenna and it is still filled with that 'bad' oil. I have built many antennas and it was fun. Learned a lot. The thing I learned the best was that when it comes to antennas, you can never know enough - or too much!
Off topic, a long, long time ago just for fun I tried for my DXCC, but doing it 100% mobile and that with only 100 watts PEP. Only got to 70 odd countries before I gave up.

Eskimo

Shorten the antenna till you get your best reading on 19.. or whatever channel you run on the most. Your antenna is a bit too long right now.

TPilaske

Yeah... I saw those instructions on the antenna package. I hadn't moved the screw at all and that's what I got! So I'm quite pleased from where I was at! I'll prolly mess with it later today or tomorrow! I mostly just run 19...


Tony