The front part of a new unit might fit in place of the one that was damaged, if the dimensions have not changed much. I could simply secure the feed line and use the back part as is, without a front.
The feed from the antenna enters at the bottom, connected to the two long machine screws. At the top end of each screw a gas tube protector and a 1 Mohm resistor connect to a ground lug. The resistor provides a path for static charge to bleed off. A capacitor at the top of each screw connects to the balanced output lugs for the portion of feedline that enters the house.
Here is an annotated close-up of the area that shows the visible damage. Click on the photo for a better view. The two resistors have normal readings. I plan to replace both gas discharge tubes. The two capacitors are not shorted, based on ohmmeter readings, and don't appear to be open, based on transceiver operation and SWR readings. They may have changed somewhat in capacitance and should probably be replaced, too.
At the transceiver end of the feedline, I inspected the balun and found no visible damage. Ohmmeter readings revealed no shorts or grounds.
Update: In February of 2017, when adjusting the lengths of the dipole legs, I found additional evidence of the lightning hit at the southwest end of the dipole. See the two photos at the end of this posting.
John
What is the ground lug tied to?
ReplyDeleteI have the same ladder line connector to be used in new configuration
The ground lug is connected to an 8-ft ground rod via #6 copper wire.
DeleteMr. John, I really appreciated your blog on the lightning strike. I know you must be busy, but if you find time to help someone very new to radio and electronics, I have a question for your expertise about grounding. I am planning on building my first antenna. It will be an Inverted "V" multiband doublet dipole antenna. Each leg is 65 feet long. The antenna will be matched by a Murch UT2000a transmatch. The dipole will be fed by 100 feet of 450 ohm ladder line. The ladder line will then attach to a 4:1 balun with a PL-259 coaxial output. The coax will go from the balun to the house.
ReplyDeleteDo you have any advice about how / where to place a lightning arrestor and what arrestor to use? The one you used above looks good.
Thank you kindly,
In reply to the above questions, my study of the topic has always found recommendations for installing surge protection on RF feedlines OUTSIDE the building, with as short as possible connection to a good earth ground. This ground should be bonded to the power system ground. This is not always possible with a reasonably short connection.
ReplyDeleteSince your balun is located outside, you can use a surge arrestor with coaxial connectors. This is the most compact and popular design, allowing for easier housing. Since my balun is located indoors, closer to the transceiver and tuner, I used an arrestor designed for balanced line.
My posting on another blog:
http://thebellringers.blogspot.com/2013/07/lightning-protection-grounding.html
has links to several good articles about lightning protection and reference to products from 2 companies.
Good luck!