Home > HF, Home Brew > Antenna for 80m DX

Antenna for 80m DX

For the last few weeks, I’ve been contemplating putting the 160m skywave loop back up here. I used it quite successfully for 80m QRP DX using WSPR, but for local contacts it  didn’t do any better than my ZS6BKW which just seems a fantastic antenna (except on 15m).  On 80m the  ZS6BKW is great locally (VK) but not too good on 80m DX. The radiation pattern is almost omni- a little squashed long side – but it has no deep null overhead. The 160m skywave being two wavelengths on 80m however has a deep null and a much lower takeoff angle. The problem at my QTH is the 160m is squashed into a sharp diamond rather than a nice open square, and I am not sure how that affects things. Given my success with the vertical moxon, I decided to see if a vertical loop would be a better option. Felix VK4FUQ and I had discussed vertical quad loops quite a bit and I have to agree that a corner fed quad loop looks ideal.  Getting sufficient height on 80 meters is always a challenge for any antenna, so a low takeoff angle by any other means must be attractive for DX work.

Last night I heard K6OY from Aptod California RS 47 on 80m here in VK4, and that was the inspiration to get a big delta loop up at last. My present license does not permit Tx above 3700 which is below the DX Window, but I am hoping for two things. 1. Modern internet communications will allow me to inform others of my DXing below 3700. 3640 to 3700 is where I will operate. 2. I hope to finish my Advanced call study by Christmas.

So while searching around the net for the experiences of others, and after mulling over previous discussions with Felix and others, I decided to try an apex up (bottom corner fed) triangular loop.

I have a very tall bloodwood tree (17 to 20m tall) in my front yard ideally placed near the boundary fence. The antenna design calls for an apex of 14m and a 40m base at about 1m elevation. With this tall tree I managed to get the base about 1.5 m above ground. I am now working on the feed arrangement which will be a 1/4 WL of 75 ohm coax (corrected for velocity factor). I have always preferred to feed my quad loops this way.

I hope to report here soon on the performance. The antenna is almost impossible to photograph but I’ll try.

 

80 Loop Feed Point

 

 

80m Loop Bottom Corner

 

 

Red wire is part of 80m Loop Antenna

 

I’ll do some modelling in NEC laterCocoa

73 David

VK4MDX

Advertisements
Categories: HF, Home Brew
  1. No comments yet.
  1. October 20, 2010 at 1:33 am

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: