Topband: 160m Inverted L High SWR

[Grant Saviers]

In order of approximate decreasing importance:

1. the elevated radials should not be grounded anywhere.
2. With elevated radials, you must have a good feedline choke at the 
feedpoint, about 9 turns on a type 31 "big clamp-on", and that will 
require RG58 or TFE RG174 if you run 1500 watts.
3. My 160m T has about the same vertical dimensions but needed another 
80' total on the T top to resonate at 1835, or about 157' total wire.  
Keep all wires more than 18" from paralleling the tree trunk and large 
branches.  Remember there are very high voltages at the top load wire ends.
4. my feedpoint Z is 25 ohms (per EZNEC and VNWA measurements) and a 2:1 
balun brings the SWR to about 1.1 at 1835 with 6 x 125' radials at 10' 
elevation
5. I will add another 2 radials and probably a Hi Z choke for DC 
grounding.  I don't expect much change in the resonant F since radials 5 
& 6 had little effect. Check antennasbyn6lf.com for a lot of data about 
elevated radials.
6. series capacitors switched in series to the feedpoint with vacuum 
relays or a motorized vacuum variable is planned per W8JI's suggestion 
to be able to tune higher up the band.

Grant KZ1W
Redmond, WA


On 10/1/2013 2:08 PM, Bill Stewart wrote:
> Good afternoon all,
> I just finished installing a new Inverted L. The previous one was removed because
> a tree fell across a set of guys on my tower, which had to be taken down. The new
> Inverted L is strung up amongst a lot of tall (80 ft +) pine trees. The vert. section is
> abt 55 ft & the rest is nearly flat horizontal. Total length is 130 ft/6 in. I am using a
> 4 wire c-poise abt 9 ft high of which none are directly under the horiz. section.
> Each wire is abt 135 ft long. The min. SWR is abt 2.9:1 at 1833 khz. The SWR
> curve is broad which looks odd to me. I am feeding it direct with a random length of
> 50 ohm coax. For these tests, I am using a TS-440S, which reduces power at this
> value of SWR (the internal tuner does not operate on 160). Normally, I would run
> vintage xmtrs, which load up ok. I will try it tonight to see if it gets out of the yard.
>    
> Any suggestions how I can get the SWR down below 2:1 so the TS-440S will work at
> full power? I apologize if this subject has been discussed before. If so, please point
> me towards that info.
>    
> Many thanks for any comments....73 de Bil l K4JYS
>   
> _________________
> Topband Reflector