A Fishing-Pole vertical.            Lou Blasco.  June 2008.

 

The aerial I used was a vertical modelled on an original idea from Dallas - VK3DJ. He provided the loading coils and coil box for my evaluation and I'm very grateful for his input and assistance.

Enclosed are a couple of pictures showing the aerial deployed for 80m operation.

Came back from a short trip to the country and what I thought was a very successful 7th birthday party and radio expedition. Lot's of  firsts for me, 300km simplex contact on FM 5w with the FT817 no atmospherics involved (I don't believe so) as the far end had 4 x 13el vertical yagis at 75ft running 100W, sigs were 5x0 in both directions. Only a few HF contacts on 80m but again with just a few watts I was happy with the results as most contacts were over 500km and 5x8. Worst contact was to my neighbour who lives near a  sub-station and has constant S8 noise to contend with. Had a long chat with a bloke that takes his portable gear down to the end of a jetty and drops a stainless steel plate over the side using the sea as his ground plane and an 8m fishing pole to support a straight  piece of wire. Along with a little AMU and a 7AH gel cell he's fully operational in minutes and the only problem he has is onlookers asking what kind of fish he's after!!
The aerial I used was a vertical modelled on an original idea from Dallas - VK3DJ. He provided the loading coils and coil box for my evaluation and I'm very grateful for his input and assistance.
 
My vertical was a success as far as a portable system goes but I'm thinking about ways to reduce deployment time and making band switching a little simpler. You can read books " 'til the cows come home " but nothing beats practical experience when it comes to playing with aerials. I'm full of ideas and enthusiasm for QRP, portable and cheap operation now.
 
Enclosed are a couple of pictures from this morning showing the aerial deployed for 80m operation.

Click on thumbnail images for full sized photos.

The large black line running across the image is an irrigation hose and has nothing to do with the aerial.  The first image shows a 17uH loading coil most of the way up the  pole with a short section of wire running from the coil to the top of the pole. The second image shows a close up of the feed system and ground mat. The pole slips into a short steel pipe with a 200mm spike to hold it still on the ground. Three polyester cords guy the pole at around 6m from the ground. The guys are not needed if the wind is slight but I use them anyway because it does not add much to setup time. The die-cast box is a convenient way to connect the coax and earth mat together. The black box is only used for 80m and contains a small coil with multiple taps brought out to banana sockets. The box has an SO239 on the bottom and for expediency I've used a small wander lead to connect the center of the socket to the die-cast box. Without the box the aerial is resonant at 3730 and has a BW of 30KHz at the 1.5:1 points. With the box in place I can plug the bottom of the vertical into the appropriate tap and maintain a low SWR all the way down past 3500. Note that no tuner is required besides the black box. On 40m and 20m the aerial is well matched over the whole of the band without the need for a tuner.
 
The original idea for this aerial was to use the car chassis as a ground plane with capacitive coupling to earth for added effect. As I had plenty of wire I opted for a ground mat of 8 x 25m radials of 1.0mm insulated Cu. All my research leads me to believe that the best earth mat should have a radius at least equal to a quarter wavelength at the lowest frequency  of interest and the more radials the better. A figure I see quite often is 120 radials which is clearly out of the question for a portable installation. I chose 25m because I had two 100m rolls of wire and I didn't want to waste any wire. I could have cut them at 20m and had ten radials but that would mean more work during deployment. The radials are laid out in a rough circle and are not staked into the ground or connected together at the far ends.
 
Future development.
 
I intend to do away with both boxes and replace them with a section of PVC pipe that can slip over the pole instead of clipping/clamping  onto the side of the pole. There will be provision in the base of the pipe for an SO239 and earth lugs and the top of the pipe will hold taps for loading coil in a similar fashion to the black box. This should be less fiddly and be easier to install. The 40m and 80m versions use two different loading coils and top wire section. I want to make it one tapped coil and the same length top wire. This should be possible without too much compromise. Also thinking about the 20m section. Currently this is a plain 1/4 wave vertical. I think something akin to a base loaded 5/8 should also be possible.
 
The biggest problem is I have is deploying the ground mat. It can add another 20 minutes to the installation and it's not so easy to fit a 200m roll of wire into a back pack although this is not a problem if you have a vehicle at your disposal. There's a constant battle in my head between wishes and wants and the danger that the ease of installation or portability aspect of the arrangement will be lost. 
The biggest attraction of this system is that when you deploy from a vehicle as the designer intended, you can be on the air in five minutes and you don't need any trees, guys or earth mat. Trying to maintain that most important and practical attribute makes other modifications that much more difficult.
 
A very interesting project indeed.

73 Lou.