Topband: Half or Quarter Wave??

[Richard Cariello]

Paul,
I would stay with a 1/4 wave setup. By extending the horizontal wire so that the total antenna length is a 1/2 wave sounds like a good idea BUT at a height of 45 feet above ground on 160 meters. I would think more of your power will be getting dumped into the ground then what you are dumping now.

I use to put up a half wave wire vertical with a 5 foot balloon. Played great BUT only good for a quick weekend and the tuner parts running 1500 Watts were massive because of the very very high voltages. 

You should see some improvement in your current setup  if you move the vertical wire away from your tree. There is allot of water in that tree even frozen which a am sure sucking the RF right out of the antenna.

If you want to do anything to the ANTENNA TYPE change the "L" to a "T" by attaching another horizontal wire at the "L" junction point or moving your vertical section (away from the tree) to the center of the horizontal wire you have up now. Just make sure the horizontal wire is the same length from the vertical tie point to both ends. 

Why?
The setup you have now is giving you mostly high angle radiation which is good for local contacts. An inverted-L for 160 meters should have around a 70 foot vertical section to compete for DX operation. Again your current "L" setup will work but not as well as a "T" same vertical height for DX operations.

The feed point impedance with the "T" will still be very low, as it is still being feed around the 1/4 wave current point so you won't have to deal with very high voltages. You might need a loading coil depending on how long you can make the horizontal wires. The amount of power radiating off the "L" or "T" should be about the same BUT remember you will be getting allot more at low angles with the "T".

The next area of improvement I would work on is the radial system. Elevated radials are nice but to be really effective need to be tuned. To isolate the antenna from the ground losses takes allot of radials. If you have the room place as many radials as you can on the ground. Slit the soil to cover the wire and hope for the best. If your limited to how much wire you have allot of short radials around the antenna base is better then one, two or three  long ones.

Best of Luck,
Rich AA2MF
rlcariello at verizon.net

 
On Jan 6, 2012, at 12:30 AM, PaulKB8N at aol.com wrote:

> Before doing anything else, consider a more robust tuner at the base, that  
> is a high-current area whether the antenna is 1/2 or 3/8 WL.  A simple L  
> network tuner with a #12 or #14 air-wound inductor and a variable capacitor 
> with  at least 1000V spacing will provide much better performance IMHO.  You 
> can  very easily compare performance with the LDG with a simple RF Ammeter 
> at the  tuner output.  I have the Z-11 Pro and even a fairly modest home  
> brew manual tuner produces stronger currents at the base of my inverted  L.
> 
> I assume your deer fence is elevated, perhaps 6' or so, I'd consider  
> installing some insulators along the span of the top wire around your lot at  
> about the 50' point and add a couple more wires diagonally across the lot for a 
> total of 4 50' elevated radials, even if they are asymmetric around  the  
> base of the vertical.  Many have reported much better performance with  
> length that approximates the vertical height of the L.  Be open to other  ideas 
> from the group on the overall length adjustment, it has been discussed at  
> length, no pun intended.
> 
> Paul, K5AF
> 
> In a message dated 1/5/2012 10:38:43 P.M. Central Standard Time,  
> eckerpw at yahoo.com writes:
> 
> New to  the list and new to 160M. I have a 1/4 wave Inverted L that I have 
> finally got  the bugs out of and it seems to be working fine. Vertical leg 
> is 45' and  horizontal run is 86' for a total length of 131'. Have a LDG 
> Z11Pro  auto tuner at base of pine tree that vertical leg runs up. 4:1 balun at 
> base  of vertical feeding RG-213 coax to shack. I have a 250', three strand 
> Deer  fence around the lot that I am using all three strands  as my radial  
> system.
> 
> 
> --- Question is should I leave well enough alone or would I  get better 
> results on 160M by extending the horizontal leg, to  1/2 wavelength length??
> 
> 73 and  Tnx
> Paul
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