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Author Topic: 43' Vertical, DX Engineering Un Un, Palstar AT2K and Palomar BA8 choke  (Read 1450 times)
AF4RK
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Posts: 39




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« on: March 26, 2013, 06:07:46 AM »

For some reason, using the Palomar Ferrite on DX Engineering 400MAX low loss coax causes intermittent high swr. When transmitting the tuning for 1:1 changes on the Palstar. Using plain coax and no problem. I have put the ferrite at the output of the linear as well as mid way between the antenna and tuner. Same problem. Anyone understand why this is happening? The S9V 43' vertical is fed by the DX Engineering UN 43. I have also used the Balun Designs similar model. I made two of the "Line Isolator" coax jumpers about 10' with the ferrite on one end. Same problem with both and I used a piece of coax with a PL 259 assembled by DX Engineering. I have the DX Engineering aluminum coax tools, so I am very sure my PL 259 is assembled and soldered correctly.
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W1VT
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« Reply #1 on: March 26, 2013, 07:25:26 AM »

Ferrite baluns will often overheat and change the tuning.

Zack Lau W1VT
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AF4RK
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Posts: 39




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« Reply #2 on: March 26, 2013, 08:36:16 AM »

I'm sure heat can be a factor, but 50 watts? I'm thinking more along the lines of saturation. The ferrite beads were cool to the touch.
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W1VT
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« Reply #3 on: March 26, 2013, 09:50:23 AM »

I'm sure heat can be a factor, but 50 watts? I'm thinking more along the lines of saturation. The ferrite beads were cool to the touch.

I thought you were running more than 50 watts out of your linear.  

Typically what happens is that you have excessive shield currents and try to choke it off with the choke, but the choke impedance isn't high enough to do a good job, so the current flows through the balun anyway, and burns it up.  This is a common problem with ferrites because the balun impedance is only 1000 to 2000 ohms--we really want 10 times that.  Coiled choke bauns work better on one band--but the impedance on adjacent bands is even worse than ferrite baluns.  A better solution than choke baluns is to install lots of radials--not only does this decouple the feedline, but also improves signals.

Zack Lau W1VT

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K1ZJH
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« Reply #4 on: March 26, 2013, 10:15:55 AM »

I've seen my Dentron tuner detune when running 800 watts into a low Z load, enough to distort the Dentron inductor!

Pete
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AF4RK
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Posts: 39




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« Reply #5 on: March 26, 2013, 10:29:00 AM »

I have 23 radials of various lengths totaling 500' of wire.  Maybe I don't need a choke. Not using one because of the tuning issue and works fine.
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AF4RK
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« Reply #6 on: March 26, 2013, 01:23:35 PM »

I don't use the Alpha on PSK  Wink
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W1VT
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« Reply #7 on: March 26, 2013, 02:40:32 PM »

Bad connections such as loose hardware and cold solder joints can also cause the SWR to vary intermittently. 

Zack W1VT
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AF4RK
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« Reply #8 on: March 28, 2013, 08:36:03 AM »

Only happens with coax that has the Palomar. Never happens with the plain coax. I have 2 palomar ba 80 choke assemblies. I am thinking that the added inductance is causing the flex radio to oscillate. Flex is not the most stable of radios.
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AF4RK
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Posts: 39




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« Reply #9 on: March 30, 2013, 02:57:27 PM »

I put the ferrite choke section of coax at the base of the vertical and no problems, so no bad solder connections. I have a 6 inch SO 239 barrel running through the wall of the house. That seems to be where the problem is. Putting the choke at the base of the vertical makes sense and that piece of coax works without hi swr
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