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Author Topic: Antenna Analyzer Question  (Read 2657 times)
W5XNA
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« on: September 27, 2017, 07:16:23 PM »

I just bought a MFJ 269C analyzer.  The manual cautions to protect the antenna connection port from electrostatic discharge (ESD).  My MFJ 269C 'Nifty Mini-Manual' cautions "To prevent static charges from damaging the analyzer, be sure to momentarily short the antenna/feedline leads together immediately before attachment to the analyzer."  Not wanting to fry my analyzer on the first try, how do I do this?  Thanks!
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W5XNA
N8EKT
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« Reply #1 on: September 27, 2017, 07:29:33 PM »

Analyzers can be damaged by static build up and high levels of rf

Simply bleed off any charge by momentarily using something conductive to short across the antenna connector

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K4JJL
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« Reply #2 on: September 28, 2017, 07:27:45 AM »

I store mine with a small 50-ohm load on the output, too.
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WB6BYU
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« Reply #3 on: September 28, 2017, 08:31:06 AM »

The danger is that there may be static build-up on the antenna lead, so it doesn't matter how
you store your analyzer.

Antennas can pick up pretty high static charges if they don't have a DC ground connection.
You need to drain that off to ground before attaching the cable to the analyzer.  Just shorting
across the coax connector with your finger may help (unless you have really dry skin), but
also being grounded when you do it is better.  (But that isn't always convenient, particularly
when working up on a roof.)

If you feel a tingle, then you certainly have a voltage issue:  the human body will feel a static
shock around 2000V, and solid state devices can be damaged at well below that level.


Multi-transmitter setups such as Field Day pose other problems:  if any of the other stations
are transmitting while you are trying to measure an antenna, there may be enough RF picked
up on your antenna to damage the analyzer.


And, to some extent, the manufacturer wants to be able to say they warned you, so it isn't
their fault when the analyzer gets damaged.
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W5DXP
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« Reply #4 on: September 28, 2017, 03:20:09 PM »

I use a ball of aluminum foil for such.
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KH6AQ
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« Reply #5 on: September 29, 2017, 08:53:33 AM »

I touch my finger between the coaxial cable connector center pin and shell for 1 second. I then touch the shell of the analyzer to coax shell to equalize the potentials.
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AA5MT
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« Reply #6 on: October 02, 2017, 10:25:05 AM »

I grabbed the pl259 during a snowstorm.  It about knocked me across the room.  Huge static buildup would fry the electonics like it did me.

Tom
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K0UA
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« Reply #7 on: October 02, 2017, 11:01:08 AM »

I grabbed the pl259 during a snowstorm.  It about knocked me across the room.  Huge static buildup would fry the electonics like it did me.

Tom

There can be some "interesting" voltages built up on voltages during certain conditions.  When I was a kid, with my 130 longwire, during snow/wind storms, sometimes it would build up some really high voltages.  I could take a 2 foot fluorescent tube I had laying around and hold it in my hand and touch the antenna lead in wire with the other end and it would light up fully. It was kind of eerie.   I usually grounded the lead when not using it to prevent it from "snapping" during the middle of the night and waking me up!
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W5DXP
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« Reply #8 on: October 02, 2017, 03:57:00 PM »

I grabbed the pl259 during a snowstorm.  It about knocked me across the room.

Welcome to precipitation static. The worst I ever saw was dust storms in AZ. The arcing at my PL-259 sounded like a machine gun in the middle of the night. I reduced the problem by replacing the bare wire on my G5RV with insulated wire with a voltage rating of 1000v.
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W6EM
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« Reply #9 on: October 02, 2017, 05:51:41 PM »

I grabbed the pl259 during a snowstorm.  It about knocked me across the room.

Welcome to precipitation static. The worst I ever saw was dust storms in AZ. The arcing at my PL-259 sounded like a machine gun in the middle of the night. I reduced the problem by replacing the bare wire on my G5RV with insulated wire with a voltage rating of 1000v.
With auto transformer connected baluns, one doesn't have such problems.........
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W6EM
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« Reply #10 on: October 02, 2017, 06:01:41 PM »

According to some specs I found, the polyethylene dielectric of RG-8 is good for about 4kV RMS.  Easily twice that for DC.
And, although only 3000pF in a hundred feet, still enough capacitance to hurt someone if charged up from wind or lightning influence....if you have no balun or a current balun.

Perhaps safest to make up a shorted SO-239 or a screwdriver blade to make an idle end safe...  Don't use your fingers or hands.  Your heart might be in the path of the discharge current...
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W5DXP
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« Reply #11 on: October 02, 2017, 08:07:19 PM »

With auto transformer connected baluns, one doesn't have such problems.

Unfortunately, the typical 1:1 choke-balun doesn't have a DC path between conductors. I once tried a choke between the feedpoint terminals and it worked on 80 but was self-resonant around 17m.  Sad
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AC9RN
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« Reply #12 on: October 06, 2017, 04:35:38 PM »

Just use your finger  - No biggie.
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Lenny, AC9RN (Formerly KB2NYA)
K8AXW
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« Reply #13 on: October 07, 2017, 09:45:24 AM »

Good suggestions, all. I had the arcing between the two leads of my 300 ohm twinlead wake me up out of a sound sleep at 3:00AM! 

People who short the connectors with their fingers are the same ones who test for a hot 120VAC line with their fingers!  LOL 
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