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Swr with new antenna?

Lil'Yeshua

.......
Nov 22, 2012
4,625
305
93
Pageland,S.C.
Did try to adjust in open field and have no rust issues. Im thinking defect in antenna. Did not come with scratch off card and looks like package was restapled. Bought it from H&Y.

The PL5000 has a wide band performance rating. Are you using it for just 11 meters? If used for just 11 meters it should be showing a nearly flat swr of hopefully 1:1.
On my mini SUV I had to trim almost 7 cm off my whip for the freqs I wanted to use. Check the swr on channels 1&40. I have the advantage of having a multi band radio, meaning I see a much more drastic change of swr from 25.515-30.315 MHz.

Maybe the big dogs might can pitch in and help you to solve this issue.
 

roadrage

Active Member
I have heard others have this problem. Many times I hear the response that increasing the power doesn't increase SWR readings. But I too have run into this problem. I agree with an earlier post, to your thread, that sometimes a problem exists and goes unnoticed with lower power system. That problem becomes more and more visible (via SWR meter) as power increases.

I have a 102" with 6" spring on a ball mount, right on the roof of my pick-up, which is bonded. I use a Galaxy 95t2 (with 35W DK and 140W PEP) SWR showed about 1.4:1 which is ok. If I crank the variable power down, the needle goes to 1:1 and crank it up to full power and its back to 1.4. Add my TNT600HD amp and the SWR goes up to a little over 2:1. I took some magnet wire to build a shunt coil at the feed point of the antenna, and it helped. It dropped me to 1.25:1 with no amp and 1.65:1 with it I added an RF Limited no ground tuner, and it didn't really do much to help. I haven't played around with it much lately. I removed the amp until I get it figured out. I do suspect that my RG8X, which is old, may be some of my problem.

That wouldn't be your problem because when you change out the antenna/loading coil, you are using the same coax and base and getting different results. So there is something else going on. I am going to guess that there is something with the capacitance. This is where an antenna analyzer would be beneficial. SWR meters tell very little. Sometimes they can show that there is a problem, but it doesn't help to solve it.
 

Lil'Yeshua

.......
Nov 22, 2012
4,625
305
93
Pageland,S.C.
The Sirio is longer with the loading coil up higher than the Wilson. I thought it might be his coax. I posted a Worldwide thread in which M42Duster and others mounted a Sirio on a Wilson base with no problems.
Maybe Sonic will get it figured out.
 

The DB

Sr. Member
Aug 14, 2011
1,996
1,490
193
St. Louis, MO
If you raise the power and your SWR reading changes one of a few things is happening.

1) You either have a problem with the antenna itself, or the added power is pushing one or more components near or beyond their limits, or the antenna is in the process of failing on you.

2) The amplifier being used is not putting out a clean signal, and thus is spewing out harmonics and/or spurious emissions. This could be an issue with poor amplifier design, or could be the just as common issue of the amplifier being pushed to hard in any number of ways (to much power driving it, running at a voltage beyond the design specification(1), ect.) An antenna system that is wide banded will have less of a change in the SWR readings in this case as it doesn't try as hard to reject out of band signals as a narrower banded antenna.

A note on the issue being with a magnet mount. A magnet mount is essentially a capacitor between the magnet and the metal of the vehicle body underneath. Increasing power does not affect the capacitors ability to pass AC current, to a point. This point is when there is enough voltage to arc across the capacitor plates. As the same setup and the same mount are not having this issue with another antenna it is definitely not the issue here.


The DB


(1) When I say design specifications here I am not referring to the amplifier but the transistors inside. It is common practice for companies such as X-Force and Dave Made to recommend you far exceed these specification. There is always a cost to exceeding the specifications on said transistors, even if you don't notice it.
 

roadrage

Active Member
The DB


(1) When I say design specifications here I am not referring to the amplifier but the transistors inside. It is common practice for companies such as X-Force and Dave Made to recommend you far exceed these specification. There is always a cost to exceeding the specifications on said transistors, even if you don't notice it.

Yes, my X-force 600HD claims up to 1000W output and it uses the same 4 2879s as a Texas Star DX500 who only claims 500W. And Toshiba spec sheet lists the 2879s as max output of 100W PEP per transistor.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,666
1,578
173
Yes, my X-force 600HD claims up to 1000W output and it uses the same 4 2879s as a Texas Star DX500 who only claims 500W. And Toshiba spec sheet lists the 2879s as max output of 100W PEP per transistor.

Sorry but your information is incorrect. The X-Force 600HD is a 6 pill amp, not 4. You could be thinking of their 400HD model.
 

9C1Driver

Sr. Member
Aug 13, 2008
3,666
1,578
173
It shouldn't have been restapled. Maybe H&Y can replace it with hopefully an unopened one.

Nothing new their, Copper and H&Y are famous for selling factory seconds, closeouts, refurbs, and returns as brand new. Read their return policy that's hidden away, they warranty and stand behind nothing. They will "assist" you with a manufacturer's phone number or address so you can send it to them for repair.
 

roadrage

Active Member
Sorry but your information is incorrect. The X-Force 600HD is a 6 pill amp, not 4. You could be thinking of their 400HD model.

I am sorry, I should have specified. I have the TNT 600HD by X-force which has 4 2sc2879s. Not the X-force 600HD which is the 6 pill, class C. Two different series of amps by the same manufacturer. My bad. :oops: Either way, I am unintentionally hijacking this thread so I am shutting up now.
 

Shockwave

Sr. Member
Sep 19, 2009
3,786
3,286
273
Any chance that the amp is a little unstable and the different ant is presenting a different load ( lc not swr)? Put a patch cable in line and see what happens.

Vkrules has nailed it for you. As much as you want to think it's the antenna and not the amplifier from the symptoms, experience will tell you 90% of these issues are related to poor amplifier design and it's just the differences in load (antenna) that can trigger an unstable condition. Things like adding different length jumper cables, a low pass filter or moving the antenna could force the amp back into a stable condition. This is not a reliable means of fixing the problem and should only be used to experiment with finding the problem by changing the load.

The end result is the amplifier is not built correctly as is the case with just about everything made for this band since tubes have become more obsolete. The typical low end tube amp rarely suffered from any of these self oscillation issues and believe me, it wasn't because they were built well or had good RF layout. It's just much harder to design a clean solid state amp that will run stable over a wide range of operating conditions.
 
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