End-Fed Half-Wave [Amateur Radio Wiki]

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====== End-Fed Half-Wave ======

This is the page on the End-Fed Half-Wave antenna with a 49:1 transformer. This is a multiband antenna without the need for any tuner (which is the best type of antenna). With the blessing of Steve Ellington and his [[https://youtu.be/BpdpkUEW39o|presentation of this antenna]] I am translating everything into text for easy searching and reference for others. Please feel free to contact me with errors or additions so this can be the master how-to for this antenna. I would like to be able to give instructions for every form as well. For all of the details, please watch the video presentation. I couldn't find a place with the notes on what to order, so I made this.

===== What is an EFHW? =====
1/2 wavelength long antenna, fed on the end.

  * Can be vertical or horizontal (or both).
  * Can be tuned and limited to a single band. Matching is done by a parallel LC network.
  * Can be fed with a 1/4 wave ladder line, but will be single banded. 
  * Can be fed with a broadband high-impedance transformer for multi-band use.

===== What bands does this cover? =====

The 80m-10m (134' wire) version covers: 80/40/30/20/17/15/12/10m

The 40m-10m (67' wire) version covers: 40/20/15/10m

===== The Transformer =====
The transformer is where the magic is. If you use 1 core, it'll handle 100 watts. If you use two, it will handle even more. If you use 3 cores, it'll handle even more power and is more efficient. Unless you are trying to save money or going QRP, go with the three cores. 

For the transformer, you need:

  * ~8 feet - 12 AWG enameled wire
  * 3 - 52-mix torrids for three torrids. 43-mix for 1 or 2 torrids.
  * 1 - 100 PF 5+kv capacitor

{{:antennas:73077069_10219371861472273_5924531381920071680_n.jpg?direct&400|}}

Cut 2 wires. The primary is about 13". The secondary is about 80" long. Twist the primary with the secondary. The primary should be 2 winds. The secondary is 14 total with number 8 going across and through the torrid. The primary connects to the center pin of the coax, the end of the twisted wire connects to the ground of the coax with a 100 pf capacitor between them. The other end of the secondary goes to the antenna.

Put the transformer in a junction box with a vent and some small holes on the bottom. This allows condensation to escape. 

You can put a 2450 ohm non-inductive carbon resistor across the ground and antenna and put your SWR meter on it to see how it looks. It won't be the same as when you connect your antenna, but you can get an idea if you wired it correctly.

===== The Antenna Wire =====

For 80m you need 134 feet of wire (not including the coil). For 40m you need 67' (not including the coil). For the coil, you need 6 turns on a 1" od PVC pipe. In both cases, you can use 12 or 14 AWG wire.

{{:antennas:screen_shot_2020-02-15_at_9.25.10_pm.png?direct&400|}}

===== 75m Modification =====

Cut the antenna wire in half and add a 250 pf to 500 pf capacitor 1 kv or higher. The value can be changed to tweak the resonant point.

{{:antennas:screen_shot_2020-02-15_at_9.26.42_pm.png?direct&400|}}

===== 160m Modification =====

In order to do this, you connect the center of your coax directly to the antenna and the ground of the coax directly to your ground. You need a good ground system to make this work well.

This will add 160, 60, and 6.

Here is how to set this up with a relay. 

{{:antennas:screen_shot_2020-02-15_at_9.27.38_pm.png?direct&400|}}

===== 160m EFHW Antenna =====

There are some changes if you want to do a 160m EFHW antenna. First, you need 260 feet of wire and no coil on the antenna. The transformer should be 3 - 43 mix cores with 3 primary and 21 secondary windings (up to 30 depending on SWR). Do not cross over the winding. Use a 200 pf capacitor instead of 100 pf. This is not as resonant on some of the other bands. 

{{:antennas:screen_shot_2020-02-15_at_9.28.15_pm.png?direct&400|}}

===== How do I put up this antenna? =====

This is a very flexible antenna and it doesn't even require a counterpoise. Just ground it and you're good.

Here are some examples:
  * FullyHorizontal 
  * Inverted L configuration - Have a part of the antenna vertical and the rest horizontal. Keep the vertical part away from the house as it can pick up a lot of noise. 
  * Inverted V - No less than a 120-degree angle
  * Fully vertical

I have heard stories of bends, weaves, and other not-so-common configurations and it works for them. It can be used for portable or permanent. It's a really good all-around antenna. 

===== Full list of Materials for 80-10 version =====

  * 3 - 52-mix torrids [[https://www.mouser.com/ProductDetail/Fair-Rite/5952003801?qs=jDkmxmCvr%252BQVSS7fXQNL%252BA%3D%3D|Mouser 623-5952003801]]
  * ~8' - 12 gauge enameled wire
  * 1- 100 pf 5kv capacitor - [[https://www.ebay.com/itm/10Pcs-30KV-100P-100PF-101-high-voltage-ceramic-capacitor-30KVHFFS/264494440736?hash=item3d9518e120:g:D4EAAOSwls1cU~cl|10Pcs 30KV 100P 100PF 101 high voltage ceramic capacitor 30KVHFFS]]
  * 134' + coil - 12-14 gauge insulated wire
  * 1 inch piece of 1" OD PVC pipe
  * Stainless Steel bolts, nuts, washers, and eye bolts.
  * Enclosure
  * Vent

{{:antennas:screen_shot_2020-02-16_at_12.00.25_am.png?direct&400|}}

===== Can't I just buy one? =====

Sure you can, check out [[https://myantennas.com/wp/product-category/antennas/efhw-multi-band/|MyAntennas]] that makes some good EFHW antennas.

===== Where can I learn more? =====
  * There is a [[https://www.facebook.com/groups/EndFedHalfWaveAntennas/|Facebook group]] where the topic is this antenna where I got some of this information. I would start there.

===== What does the patterns look like? =====

  * [[https://www.qsl.net/kk4obi/EFHW%20Straight.html]]

===== Where can I buy the parts? =====

==== Ferrites ====
Here are a few sites that are known to have good ferrites:

  * [[https://www.mouser.com/Passive-Components/EMI-Filters-EMI-Suppression/Ferrites/Ferrite-Toroids-Ferrite-Rings/_/N-bw7t9?P=1yxgw95Z1ymg4nr]]
  * [[http://www.amidoncorp.com/52-material-iron-powder-toroids/]]

==== Capacitors ====