Info (as requested) re: Field Day GOTA quick-up 31-ft. 40m - 6m vertical

[KB1EHE]

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

[K1RCT]

Hi Eric, thanks for the post.
How's the noise floor with this vertical compared with a dipole? Can you advise?

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

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

[KB1EHE]

Hi Rob.

I haven't yet to do a substantial A / B test. But I was pleasantly surprised during the GOTA operations; the antenna seemed pretty quiet.

I plan to do legitimate testing this summer. I'll keep everyone apprised of the results.

Thanks for the question!

73,
Eric KB1EHE

Hi Eric, thanks for the post.
How's the noise floor with this vertical compared with a dipole? Can you advise?

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

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

[KB1EHE]

Hi Rob.

I just found a little more information regarding the noise characteristics of this antenna design. Below is a snippet from the linked-to article:

"Additionally, the unun will eliminate (virtually) all "common mode" currents on the feedline. This is important for eliminating the pickup of local electrical noise from homes and power distribution lines. The coax, being connected to ground through a DC path will eliminate all but the differential currents ... pretty cool, huh? Finally, since the antenna is connected directly to Earth ground through the secondary of the transformer, static buildup cannot occur - the antenna is a dead (DC) short to ground. This is important to sensitive, solid state radios. The 9:1 transformer provides: 1. a much flatter broadband impedance response, 2. a static elctricity-free antenna system (no buildup), 3. common mode noise immunity (if space wound as shown)."

Here's the full article: www.mobileers.com/main/wp-content/uploads/2013/01/9-to-1-Balun-for-End-Fed-Antenna.pdf