High SWR's

[otter]

so today i just tried using a new mount on my truck. it was a piece of angle iron that ran from my bed rail in the center rite behind my cab up a little past the top on the cab.
i screwed my 102 on top of it and keyed up, the SWR's were in the red.
any ideas??

[Texas Mobil 219]

A few things to check. Make sure that you got a good grounds on you truck. Check you insulator on the mount to make sure it isn't broke or cracked. Check the coax connector. They can get messed up sometime when you unscrew the and put them back on.

Another thing. Reflection. The bottom part of the 102 is too close to the cab of the truck. And finally, add 6 in to you whip with an extention to make it 108'' to see it that helps.

If nothing gets better then go after the coax itself. You can check it with an Ohm's meter to see if its shorted.

Ping back in and let us know how it's going. Good luck.

[otter]

well i have the barrel spring that i bought from rat shack which really makes it a 106 not 108.
i had/ have it mounted on the inside of my bed rail rite behind my rear window now and the SWR's are flat at 1.1 1.2
so i'm sure its not the coax cause its also new, so it might be that its too close.
219 how far away from the cab is your whip?

[Texas Mobil 219]

The base it about a 2 '' for the roof line. Take a look.
<----------<<<<<<

As soon as the battery's charge on the camra i get ya some pics.

[otter]

thank you.
I'm going to try to play around with it some more today and try to get it working with low readings..
i'll keep you posted

[otter]

well today i got a stick of square metal and mounted it to the bed rail behind my window,
the bottom of the spring is 3"s above the roof, there is not paint on the mount and bed rail where they come together..
i tested it and the SWR's were still up at 2.0-3.0...
but on my mount inside my bed the SWR's ar around 1.1-1.2...
i need some help with this one, anyone have some answers for me?
i'd really appreciate the help

[watchdawg]

are you using a external meter or the one on the radio. If you are using the one on the radio then i suggest getting an external one as they are more accurate. You might ought to ground the angle iron to the frame. If that doesnt work then i suggest maybe changing out the coax again. Just because it is new doesnt mean it is working correctly.

[otter]

i am using an external meter, the 1's on the radio's aren't good for testing..
ya i went to 5 different stores today to look for braided ground straps and no one knew what they were for, so i need to find somewhere that sells them.
i'll try running a strap from the mount to the frame and hopefully that works.
i also read that if i add some more inches between the mount and the spring it should help bring down the swr's since i'm at 106"

[Texas Mobil 219]

Now that your above the cab. Check that Coax and connector. The will sometimes get loose and wil send a headache for days. Because even thou they look and test okay they still will run your swr's wacky. Even the plastic insulator will look good but will have cracks in it.

let us know.

[otter]

well tomorrow I'm going to get a threaded connector to make the antenna an actual 108 to see if that helps out a little..
then i'll try a new connector and coax if necessary.
is there a difference between using braided ground strap and just normal wire?

[Texas Mobil 219]

To me ground is a ground. I have a ground wire from my mount to the frame. Its 6ga welding wire. My radios and amps are ground to the frams by a 12 ga wire.

[Circuit Breaker]

well tomorrow I'm going to get a threaded connector to make the antenna an actual 108 to see if that helps out a little..
then i'll try a new connector and coax if necessary.
is there a difference between using braided ground strap and just normal wire?

There's debate on that. There's a phenomenon called "skin effect." Basically, RF travels only on the surface of a wire, so you want to give it as much surface area as possible. Braid will do that...but copper straps would be the absolute best...but I doubt you would notice much of a difference. Try regular wire for now, if it works, then go with it. If you have enough coax lying around, do what I did...I stripped back some of the black vinyl jacket on both ends, added lugs soldered to the braid and made my connections. It worked fine. My 102" whip is mounted to the center of the bed rail right behind the cab. I had a mount fabricated out of steel that puts the antenna about 6-7 inches behind the cab. This is on a 2007 Toyota Tacoma and they no longer have metal beds. They're all made out of a composite material that's lighter and stronger than the thin sheet metal they used to use for truck beds. It also says you the trouble of having to get a bed liner. But this also means you have no metal for a ground plane so you need to provide one. What's kind of weird is that I had to add three connections to get a good match. When I installed the antenna, I ran two pieces of coax. I drilled a hole in the two corners of the mount closest to the cab. Then I ran two pieces of coax...one to each side of the frame. My SWR was well over 2 pretty much across the band on my 2510...which goes from 26.000 to 29.700. I tried removing one connection and the match dropped but it was still too high. So, I tried adding a third connection...this time connecting it one of the bolts used to attach the mount to the bed and it brought my match down to 1.0 to 1 from 26.000 to 27.400 and then it starts to climb. I have a Firestick quick disconnect on my antenna which adds some length to it. I'm not interested in working down to 26.000 since I'm more of an SSB person, so I can either take the quick disconnect off or cut some length off the whip to shorten it so I can get better upper coverage. I like the quick disconnect in case I have to pull into a garage or covered parking lot so I'll probably cut it.

['Doc]

Did/have you tried retuning your antenna? Changing locations does affect how the thing is tuned, it won't necessarily stay the same when mounting locations are changed.
If the antenna was working reasonably well where it was, then I would expect the bed is grounded well enough. An extra ground strap seldom does much good considering the change in mounting locations (if that 'antenna stand' is grounded to the bed reasonably well, and it sounds like it is).
- 'Doc

[otter]

when i took of the spring the swr's came down to about 1.6 - 2.0 with the spring on its at 2.5 - 3.0
so i'm pretty lost at this point haha...
and i'd really like to have it up above my cab

[Texas Mobil 219]

Hang in there man we'll find the sweet spot for your rig. So you took the spring off and your swrs came down. Thats telling me that your antenna is too high in length. Not where you have it mounted tho. If you got the base of your antenna above the cab. Good job in getting it there. Thats were it needs to be.

How long is your coax?
How old is your coax?
Are you running a amp? if so what wattage?

I guessing that you got 18' with a whole bunch of it going everywhere. 18' is a good number but there is no use in all that coax if you don't need it. Just what it takes to get from you radio to your antenna. I took it an extra step in my last coax install. It would of only taken 11 foot to get my coax in but i added an extra foot to give it 12'. Staying in the 3 foot rule (3, 6, 9, 12, 15, 18, 21). With two 9' jumpers. And with the 108''. the swrs came in at 1.1 all the way thru the band. Actually it came in very very broad banded. When it was tested. The ol boy took it up to 28.000 and they were still 1.5

New mounting locations. Everything will change as you can see. Just going to have to start at the first step and work it till you find that sweet spot.
Let us know how it going. Drop me a pm if you need to or if you need to call i send ya my number.

[otter]

well the SWR's and not being able to use my radio was **Censored** me off so i took the mount off and just remounted it on the inside of the bed rail behind my rear window.
but i'm thinking of buying/making a mag mount to go on top of my roof.
anyone know where they sell them or how to make 1?
thanks for all the help guys. i was lost with that problem

[Texas Mobil 219]

Man. Sorry to see that. We could of got you right on the money. But as long as your happy with what you got. Swing mean man.

If you change your mind and want to try it again. Just say the word. WE CAN GET IT DONE.

['Doc]

otter,
Putting things back like they were. Can't say I haven't done that. Sometimes, that's probably the best thing to do till you feel differently about the whole thing.
From what you said about removing the spring and lowering the SWR, it sounds like the antenna is just too long. If you could shorten it some more without it completely being 'un-returnable' to what it was, then that's something I'd try. That's not always very practical, so it's up to you.
Getting an antenna 'above' stuff around it is a good idea. It isn't always the absolute bestest idea in the world. So if things generally work well where the thing was to start with, why not? Getting 'away' from it for a bit and having a beer always seems to help me. The beer doesn't do that much for antennas, but I like it, so it's good practice. Right?
- 'Doc

[Red Warrior]

I mounted a 102" on a stainless steel marine foldover mount on the side rail of my truck and upon initial tests the SWR was over 3:1. I went to a local Ham with an MFJ Antenna Analyzer and the analyzer showed the reactance of the antenna was very high. We attempted to tune the antenna with a sliding wire on the tip and noticed that the reactance would change depending on where we were standing in relation to the antenna. We took the marine mount off and mounted the antenna directly to the side rail of the truck. Reactance went to zero and by adding 4" to the length the SWR went down to 1.2:1. The reactance also would no longer change based on the proximity of objects in the near-field (within 1/2 wave length).

What we determined was that the marine mount was acting like a counterpoise for the antenna changing the reactance. Since the feed point of the antenna does not change, placing the antenna on a riser does not change the electrical length of the antenna. If the riser acts as a counterpoise, it will cause all sorts of problems and make tuning the antenna near impossible. We would never have discovered the real problem without the MFJ.

Just one poor souls experience.....

[otter]

if i decide to put it back up there and still have problems, i'll ask u guys for some more help.
thanks

[Red Warrior]

if i decide to put it back up there and still have problems, i'll ask u guys for some more help.
thanks

If you get up around Santa Maria country, give 818, Motormouth, Copperhead, Coyote, AK47, and Tinker a shout on channel 6.

[otter]

Red Warrior,
i'll do that if i head up there anytime..
you guys only on ch 6?