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Author Topic: SWR meter rises as i tune my antenna  (Read 5608 times)
KC3BBI
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Posts: 38




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« on: December 14, 2015, 03:30:13 AM »

Is this an issue of RF in the shack? I have seen my swr rise while in am tuning the antenna. I have my antenna ontop the RV where it hangs 15 ft from the radio and the radials are on the ground and on top the RV. Is there an issue with insufficient ground? Do i need an RF isolator?
I have to learn how to deal with ground issues or RF. I will be getting an amplifier soon.  I am grounded to the AC ground pin on the power outlet. I have the tuner and radio grounded to the same place.
I have a FLEX 5000a and 5BTV on the ladder rack behind my kitchen back wall.
« Last Edit: December 14, 2015, 03:32:38 AM by KC3BBI » Logged
KF7CG
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Posts: 1076




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« Reply #1 on: December 15, 2015, 01:29:25 PM »

Can you lower the SWR back with your tuning? Remember, tuning the antenna the wrong way will raise the SWR and you tune for the lowest SWR. Also, if you are starting with high initial SWRs the change in temperature of the meter components can effect the reading on less expensive meters.

KF7CG
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WB4SPT
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Posts: 306




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« Reply #2 on: December 17, 2015, 05:34:36 AM »

Is the RV roof and walls aluminum or fiberglass?   If not metal, and if this proposed amp is something upwards of 500W, then you will have the entire station exposed to upwards of 20V/m field strength, maybe more.  So, yes, fix any common mode coax issue, but that won't necessarily prevent the linear from messing with things inside the RV;  laptop for the flex, etc.  I'm sure other RV/ers have a similar set up and stories to go with?
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KC3BBI
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Posts: 38




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« Reply #3 on: December 21, 2015, 12:15:31 AM »

Can you lower the SWR back with your tuning? Remember, tuning the antenna the wrong way will raise the SWR and you tune for the lowest SWR. Also, if you are starting with high initial SWRs the change in temperature of the meter components can effect the reading on less expensive meters.

KF7CG

The tuner changes the swr but it rises again while tuning.
I am aware that the tuner will tune it out of match also.
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W1VT
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Posts: 1837




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« Reply #4 on: December 21, 2015, 04:36:25 AM »

SWR drift can be a sign of ferrite in a balun, transfomer, or line isolator about the burn up.  The rising temperature should be easy to detect if you know what to look for.

Zack W1VT
« Last Edit: December 21, 2015, 04:38:40 AM by W1VT » Logged
KC3BBI
Member

Posts: 38




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« Reply #5 on: December 21, 2015, 06:45:23 PM »

Can you lower the SWR back with your tuning? Remember, tuning the antenna the wrong way will raise the SWR and you tune for the lowest SWR. Also, if you are starting with high initial SWRs the change in temperature of the meter components can effect the reading on less expensive meters.

KF7CG
The RV is fiberglass and the delta loop antenna is right overhead. The Vertical is on the back wall about 15 ft away. Some radials are on the roof. 
The tuner changes the swr but it rises again while tuning.
I am aware that the tuner will tune it out of match also.

I dont have a balun inline. I have used only a coil of six turns of cable for a line isolator.
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WB4SPT
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« Reply #6 on: December 22, 2015, 06:43:53 AM »

An rf invisible QTH may present a challenge to the laptop; but likely only with power >100watts.  I operated a plastic boat with the rig maybe 10' from the base of a 23' vertical/antenna tuner.  150watts didn't mess with that radio, but I didn't have a laptop running at the same time. 
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KC3BBI
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Posts: 38




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« Reply #7 on: December 22, 2015, 02:51:08 PM »

The flex 5000 uses a firewire connection to the desktop. My laptop does not have a means to connect to firewire. There may be a method, but I am using my desktop. The antenna is fed around 15 feet from my station. I will try to move it and see if it works.
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KC3BBI
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Posts: 38




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« Reply #8 on: January 03, 2016, 01:30:40 AM »

I Have noticed an improvement.
My antenna if fed with separated RG8x and coiled 5 turns, then it connects to a barrel connector to change over into RG213 cable.  I have just now applied a choke to the RG213 cable. My radio sees less RF according to the meters now. It is still there but the antenna is very close physically.  I think I can work with this and have been able to use the amplifier now. When the swr raises from RF then I usually will drop the power back rather than try to retune the swr. But to answer the question, I have not been able to defeat the RF when i tried it in the past. 
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