Topband: Looking to improve TX antenna Efficiency

[Joe]

Steve, 

I have an inverted L with 32 feet vertical and then 96 feet horizontal
leg.  The horizontal leg runs southeast and slopes from 32 down to 10
feet at the last 15 feet of its run.  The antenna is resonant with SWR
of 1.3 at 1.810.  It is  fed directly with 50 ohm coax. No chokes, coils
or tuning of any sort.  I have 5 random length radials made of 14 gauge
solid wire. Due to property constraints none of the radials run in a
westerly direction.

This fall I improved the ground system by adding two more 8 foot ground
rods spaced about 19 feet. Those ground rods are all interconnected. I
also raised the horizontal leg up as far in a tree as I could.  When I
raised the horizontal leg the SWR dropped considerably. The antenna
plays better now.  It seems that the improved ground system helped.

I will continue to make ground improvements as this seems to help the
most.  I cant raise the antenna any higher.

Perhaps you can also benefit by improving your ground system?

73,

Joe KB3KJS


On Tue, 2012-11-20 at 00:23 -0500, Steven Raas wrote:
> Last 'Season' was my 1st real dive into 160m. Running a 'InvL' ( which
> I will describe lower in detail ) and 100w, I managed to pull 19 DXCC
> and 48 states cfmd. I am in looking into ways to improve my TX antenna
> efficiency, for this season w/o getting to crazy . (rx antennas are in
> the works and a different topic )
> 
> Current TX antenna is as follows: (Tuned in shack / not self reasonant )
> 
> Main Element: 32 feet vertical - 90 deg bend ( the 'L' ) which runs
> 43' horzontally pointing north. Then, another 90 deg bend, and
> ascending 26' in length ( from 30' up to about 11' above ground
> running from west to east. ), then..you guessed it.. another 90 deg
> bend that now runs to the south flat top for 27' ( @ 11' up )
> 
> Ground radials qty 24. Min length 22' - max length 62' ( from az 330
> deg - 70 deg with the longer radials pointed from 35-60 deg az)
> 
> The FCP idea is not practicle for me @ this point in time.
> 
> My Thought.. add a Coil @ the 30' point of the main vertical run made
> from perhaps 1/8th inch copper tubing ( refrigerant line ) in a fairly
> large diamater ( 16-20" ), perhaps 14-20 turns even spaced, using
> perhaps drilled lexan as spacers.. Try extending the vertical run
> another 8-10' or so.. and then the rest of the antenna as is. Going
> above 40' vertical is not an option @ this point in time either. ( yes
> i know the more vertical the better its just a no-can-do for now)
> 
> At the moment the antenna's best 'swr' is at roughtly 1818 khz @ 2:1
> there is no resonant point that I can find within the 160m band. ( no
> antenna anyalizer either - Mabey santa will provide ) My best guess is
> that in its current configuration... the antenna is probabally in the
> 8-12 ohm area.. I have nothing solid to back that up however.
> 
> At the feed point I have a coaxial choke, 21 turns on a 8" form, the
> cable is similar to RG213 , with the exception the center conductor is
> solid. ( its actually 50 ohm quad shielded cable i got form a place I
> used to work, HP node cluster inter connect cable. .405" & blue in
> color,  i cant remember the vf on it but i did spec it out a while
> back, and its ok for HF use. )
> 
> Or, tuning the antenna @ the base with a variable cap. of  sufficent
> size, or perhaps even both?
> 
> I know there is NO magic that can come..im just trying to improve on
> what I have and can do @ this point in time.
> 
> Suggestions, thoughts,  flames and raised brows are all welcome.
> 
> Steve Raas
> N2JDQ
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