Swr At 1:3 And Cant Get It Any Better

[cjruger]

Ive taken about a year off from Dx'ing but got back in the swing of things recently, last year i was building a 5/8 ground plane antenna and I finally got it up and tuned the best i can. However i cant seem to get swr any better that 1:3 at full power ( around 250 dead key). With the radio at low power (3 swinging 15-20) the swr is near perfect, and less than 1:1 up to about 100 watts. its just on full power its up around 1:3. not sure that is ok for the texas star 350 hdv.

-as far as the antenna, its a home brew, aluminum solid lengths coupled together, on a aluminum base plate, with 109" 1/4 solid aluminum radials. the radials kinda sag down under their own weight, so they are not straight out or angeled down at 45 degrees, kinda arched down. Ill try to get pics up withing a few days. It is also mounted in a pine tree not totally clear above the tree, only the last 4' or so is above the tip of tree, so im sure there could be some affect from the tree, but swr is roughly same as it was when i tuned the antenna on the ground not in the tree yet

when i tuned it , I adjusted length until best swr was in the middle of the 11 meter band. then i adjusted the coil tap point until best swr i could get. Running 100' length of rg8x coupled to a 15" length, so roughly 115' total. 4 coils of coax under the feed point as a balun.
the only advice i got sofar is to get a antenna tuner, if so what is something affordable that would work?

Also about grounding, how small of wire can i run for saftey ground, and wont this become part of the antenna and affect performance?

 

[mrgumby]

nothing wrong with that swr your never gonna get a perfect match at least in the real world

 

[ponykilr]

Yep, difference between 1.3:1 and 1.2:1 is so slight as to never matter in the real world.

 

[222DBFL]

1.3 swr with amp on isn't bad, how is your tx and rx? If it's good then leave it, like said the difference is minor and won't be noticed by anyone but you. At 115ft you may experience a bit of loss with the rg8x. For that long of a run I would use lmr400. JMO. But if all is working well, then leave it.

 

[AudioShockwav]

If you are dead keying a dx 350 at 250 watts, the amp will be very short lived, it can not tolerate that kind of dead key for long.
Your 1.1 at 100 watts is fine, I would roll it back to a 75 or 80 watt carrier and leave it there.
Your SWR problem will go away and your amp that has expensive, hard to replace Toshiba transistors in it will thank you for it.

73
Jeff

 

[Beetle]

Ive taken about a year off from Dx'ing but got back in the swing of things recently, last year i was building a 5/8 ground plane antenna and I finally got it up and tuned the best i can. However i cant seem to get swr any better that 1:3 at full power ( around 250 dead key). With the radio at low power (3 swinging 15-20) the swr is near perfect, and less than 1:1 up to about 100 watts. its just on full power its up around 1:3. not sure that is ok for the texas star 350 hdv.

-as far as the antenna, its a home brew, aluminum solid lengths coupled together, on a aluminum base plate, with 109" 1/4 solid aluminum radials. the radials kinda sag down under their own weight, so they are not straight out or angeled down at 45 degrees, kinda arched down. Ill try to get pics up withing a few days. It is also mounted in a pine tree not totally clear above the tree, only the last 4' or so is above the tip of tree, so im sure there could be some affect from the tree, but swr is roughly same as it was when i tuned the antenna on the ground not in the tree yet

when i tuned it , I adjusted length until best swr was in the middle of the 11 meter band. then i adjusted the coil tap point until best swr i could get. Running 100' length of rg8x coupled to a 15" length, so roughly 115' total. 4 coils of coax under the feed point as a balun.
the only advice i got sofar is to get a antenna tuner, if so what is something affordable that would work?

Also about grounding, how small of wire can i run for saftey ground, and wont this become part of the antenna and affect performance?

Little confusion here -- a ratio is expressed as some number referenced to unity (1). 1:1 represents as good as it gets as far as SWRatio. 1:3 means nothing. Do you mean 3:1, 1.3:1 or what? Remember, the ":1" has to be at the right-hand end of the ratio.

As others have said, 1.3:1 is not bad. If you have a 1:1 SWR, don't lose sight of the fact that as you change frequency, the SWR is going to increase unless you have an unusually high loss in your antenna/feedline system. A dummy load will provide very low SWR readings but it makes a lousy antenna.

Don't try to squeeze every last watt out, as others have already said. The difference between 200 watts and 250 watts is unmeasurable on the other end of the QSO, but your amplifier will reward you by living longer.

 

[Tallman]

However i cant seem to get swr any better that 1:3 at full power ( around 250 dead key). With the radio at low power (3 swinging 15-20) the swr is near perfect, and less than 1:1 up to about 100 watts. its just on full power its up around 1:3. not sure that is ok for the texas star 350 hdv.

Linears will amplify everything including the harmonics. If your antenna is tuned dead on the channel then the antenna is NOT resonant at the harmonic frequency which will reflect back to your amp showing as increased SWR.
Put a low pass filter in line between the radio and the amp. The increase in the SWR you are seeing is the harmonics being reflected back to the radio. Add another one between the amp and the antenna if need be.
Linears work on the garbage in garbage out. If your radio was peaked and tweaked and the tech adjusted the wrong cans your filtering for harmonics might be messed up. The low pass will fix some of that.

 

[cjruger]

yes, sorry , i guess i meant 1.3:1 sometimes 1.4:1. sounds like this isnt that bad of a match, also the 250 dead key may be a bad watt metere reading, my meter is probably a little off. i cant turn the radio down any lower, it has about a 2 or 3 watt dead key on am. I get great reports of sound from locals and dx so I guess im going to leave things alone

 

[cjruger]

Here is what I'm working with. I did shorten the tap line up and come up with a better clamping system

 

[Tallman]

Did you do your own machine work on the base plate? Looks nice.

 

[AudioShockwav]

Yes, that looks great, can you post up pictures of the rest of the antenna?
What did you turn the insulator out of?
Question, are you clamping both tubes to the stub?
I looks that way in the photo.

73
Jeff

 

[hotrod]

everything sounds really good. only thing id change is the coax to lmr 400 or jefatech ll400. on the rf choke id use 1 coax .not a coupled jumper.lmo

 

[cjruger]

Yes, I machined everything myself, the insulator is just black delrin plastic
Not sure what you mean by "did i clamp both tubes to the stub"
I Plan on eventually getting 1 good length of coax, the 2 coupled together is just to get it 30 ft higher than it was, which I think the good outdid the bad on that.

The main radiator is just kinda pressed in to that black piece, the black piece is bolted from the bottom of the base plate, I pulled that base plate out of a scrap bin and machine a few more holes in it to make it.

 

[cjruger]

So now i need to ground this thing as discussed and highly recomended in another thread i have going. The ground cable will be 35-40' long and I'm not sure exactly the number yet. How will this negatively affect the counter poise of the antenna? Used on 11 meters the ground cable is close to 36' a full wave length.

 

[M0GVZ]

Ground cable is too long and will become part of the antenna system. Just what are you grounding for, RF or lightning?