[TowerTalk] newbie question on inverted-L's, tuners, and radials

Eugene Hertz ehertz at tcaf.org
Wed Jun 21 14:40:40 EDT 2006


Hello all,

I have spent the better part of the day reading through the posts on this list covering topics of radials and inverted-Ls (nearly 3,000 posts!).  Great wealth of information.  I have, I believe, a few questions that I could not directly find an answer for.

I am attempting to erect an inverted-L antenna for my shack mostly because of trees/mounting points (making a little difficult for a dipole or similar).  It will be the only antenna that I have (my first shack!).  The planned arrangement is as follows:

Feedline comes from my second floor shack down to the ground.  I will (hopefully) use a remote antenna coupler, a Harris RF-601A.  This tuner will be grounded using radials (see next paragraph).  From the tuner, a single wire will emanate up the side of the house to a mast on my chimney.  This should get the height of the vertical portion of the antenna about 40' up. The wire will then traverse across my front lawn to a tree about 140' away and still about 40' up.  I would love to be able to get some signal out on 10-160.

The Harris tuner is designed for shipboard and shore installations and can match 50 ohms to a whip of 15'-35' from 2-30Mhz.  Now, I am not sure what this implies as far as range of impedence matching capabilities.  But perhaps something can be derived from the height of the whip, probably using the ship itself as the ground plane? More information can be found here:
<http://www.columbiaelectronics.com/an_ura_38a_antenna_coupler.htm>
<http://www.torontosurplus.com/com/harris/harris_rf601a.htm>

Here come the questions:
1. Most of the discussion I read about radials had to do with "vertical" antennas.  I am wondering if all those discussions could be more generalized to pertain to all end-fed antennas such as the "L"? Is there anything different about the use of radials (sizes, locations, numbers) as applied to L's vs verticals?

2. I have an issue with the possible location of my radials. The vertical part of the antenna is very close to my house, therefore My radials can be 180deg _away_ from the direction of the horizontal wire, as the wire travels over the house (not exactly, but you get the idea).  In fact, I may only have some short radials 180 deg away from the antenna, but can do longer ones +/- 90 deg from the horizontal wire.  Question is, with a long horizontal component, is there any necessity to have the radials "beneath" the horizontal portion? For example, if I can get 30 radials in the ground but none of them are beneath the antenna is this terribly worse than 30 in the ground where some are beneath the antenna? 

3. With the heights and lengths described above, should I think about shortening/lengthening the wire (perhaps to get onto 160?) Or should I let the tuner do the work and just make the longest wire possible? Bands of interest are primarily 160,80,40,20,15,10 (until I get my urt-23 running then its all ham bands).

4. Connecting radials: I saw mention of one product for attaching the radials, namely the lance johnson radials buss. Certainly, I could mimic this and make my own, but does anyone have another product to suggest? Just trying to compile my options

I am new to this stuff, so please be gentle with me!

Thank you all in advance.
Eugene











More information about the TowerTalk mailing list