[Antennas] inverted L

[dtx]

RB wrote:

>I feel compelled to leap in here and demonstrate my ignorance.  
>  
>
had the same syndrome myself ;-)

>I've heard that the inverted L is essentially a form of top loaded vertical.  Is that true?
>  
>
Basically.  The "classic 1/4 wl" vertical has the highest current and 
therefore most radiation at the bottom.  So if you bend the top half 
over and run it horizontal, you do not lose much and you still have 
nearly the same Radiation Resistance.  Note nearly.  And if the total 
length is adjusted then you can get close to a 33+j0 feed point that 
connects fairly well to a 50 ohm coax.  This is mechanically very 
helpful on 160 and 80M.  I can think of no good reason to build an 
inverted-L for 20M.  8 ft up and 8 ft over?  Just put the full quarter 
wave straight up<G>.

>Assuming it is, will one designed for 160 also work on freqs above that band, with a tuner?
>
But when you get away from that "33+j0" point you may have trouble 
getting tuners to match/tune/cancel the reactance so your transmitter is 
happy.

>  
>
>Is the optimal configuration a tuner at the base of the inverted L?
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This is the optimal place for any tuner to be for any antenna.  
Mechanically it can be very impractical.

>Will it work if the inverted L is fed with with coax, with a tuner in the shack?
>  
>
Yes, for the band that it is resonant on as you will have a reasonably 
low SWR on the coax and the tuner will adjust the small difference 
fairly well.  Away from that and you MAY wind up with horrendous losses 
in the coax if it becomes long and the SWR is high.  The tuner may make 
the TX happy while having 50% power loss.  And if you double the power 
to make up for it, there is a good chance of overheating and damaging 
the tuner.  Restated, don't put a KW of 80M signal into a run of coax 
going to a 160M inverted L.  You could get so "transmission line 
transformer" action that will make life very exciting<G>  Even if it 
does appear to tune up and load ok at low power.

Gary WA6DTX