Hi everyone.
Just following up to everyone's requests for more information regarding the 31-ft. 40m - 6m vertical that we used for the GOTA station.
Key ingredients: A 9:1 unun feeding a 29.5-ft. wire that ran up the side of a 31-ft. windsock pole. No ground radials are needed. As long as you run at least 25 feet of coax from the antenna, as a counterpoise, it will perform like a charm. (To keep RF out of your radio gear, I suggest creating a super simple "8 x 8" RF choke -- 8 loops of coax with a diameter of 8" -- right before the coax enters the shack. Don't do it at the antenna -- or you'll lose the benefit of the coax shield as a counterpoise.)
Here's a great article with overall info, including how to wind the 9:1 unun toroid and SWR using various wire lengths:
http://w5bii.org/dokuwiki/doku.php?id=9to1_unun_antenna
UPDATE: Link no longer works. See below...
IMPORTANT UPDATE 7/1/16: Evidently, the Webmaster let the domain name expire on June 29th! I've been able to dig up the content via Google's cache at this link: http://bit.ly/29hEcwB (Not sure how long the content will remain in Google's cache. So visit and print it ASAP.) But the cache just contains the raw text. I've also been able to find another source for a diagram for winding the toroid: http://vk6ysf.com/unun_9-1_image02.png
Here's an example source for the T200-2 toroid: www.ebay.com/itm/T200-2-Toroid-Core-Micrometal-Powdered-Iron-/112014273920 (There are lots of sources on eBay.)
Here's a low-cost fully constructed 9:1 unun on eBay: http://www.ebay.com/itm/End-Fed-Dipole-80-6-meter-Portable-HF-Antenna-Matchbox-System-WATCH-VIDEO-/191226640113
Here's the same unun with stainless steel hardware: http://www.ebay.com/itm/-/191903715614
You can use just about any wire you'd like for the antenna wire.
Amazon and eBay are great sources for the telescoping fiberglass pole. Just search fiberglass "kite pole" or "windsock".
BTW, you can experiment with longer lengths of wire, with our without a pole. For instance, you can have inherently low SWR from 160m - 6m with a 53-ft. wire. Just toss the far end (with light rope or durable fishing line as an end insulator) over a tree branch, etc. It makes a great sloper, too. Lots and lots of possibilities!
If you have any questions, let me know. Enjoy!
73,
Eric KB1EHE
Just following up to everyone's requests for more information regarding the 31-ft. 40m - 6m vertical that we used for the GOTA station.
Key ingredients: A 9:1 unun feeding a 29.5-ft. wire that ran up the side of a 31-ft. windsock pole. No ground radials are needed. As long as you run at least 25 feet of coax from the antenna, as a counterpoise, it will perform like a charm. (To keep RF out of your radio gear, I suggest creating a super simple "8 x 8" RF choke -- 8 loops of coax with a diameter of 8" -- right before the coax enters the shack. Don't do it at the antenna -- or you'll lose the benefit of the coax shield as a counterpoise.)
Here's a great article with overall info, including how to wind the 9:1 unun toroid and SWR using various wire lengths:
http://w5bii.org/dokuwiki/doku.php?id=9to1_unun_antenna
UPDATE: Link no longer works. See below...
IMPORTANT UPDATE 7/1/16: Evidently, the Webmaster let the domain name expire on June 29th! I've been able to dig up the content via Google's cache at this link: http://bit.ly/29hEcwB (Not sure how long the content will remain in Google's cache. So visit and print it ASAP.) But the cache just contains the raw text. I've also been able to find another source for a diagram for winding the toroid: http://vk6ysf.com/unun_9-1_image02.png
Here's an example source for the T200-2 toroid: www.ebay.com/itm/T200-2-Toroid-Core-Micrometal-Powdered-Iron-/112014273920 (There are lots of sources on eBay.)
Here's a low-cost fully constructed 9:1 unun on eBay: http://www.ebay.com/itm/End-Fed-Dipole-80-6-meter-Portable-HF-Antenna-Matchbox-System-WATCH-VIDEO-/191226640113
Here's the same unun with stainless steel hardware: http://www.ebay.com/itm/-/191903715614
You can use just about any wire you'd like for the antenna wire.
Amazon and eBay are great sources for the telescoping fiberglass pole. Just search fiberglass "kite pole" or "windsock".
BTW, you can experiment with longer lengths of wire, with our without a pole. For instance, you can have inherently low SWR from 160m - 6m with a 53-ft. wire. Just toss the far end (with light rope or durable fishing line as an end insulator) over a tree branch, etc. It makes a great sloper, too. Lots and lots of possibilities!
If you have any questions, let me know. Enjoy!
73,
Eric KB1EHE
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