The KK4TR Antenna & Radio Modification Webpage

The KK4TR/KN4LF ALL-BAND TRANSMIT/RECEIVE "L" ANTENNA

THE KK4TR/KN4LF ALL BAND 160-10 METER "L" ANTENNA & THE CLIPPERTON "L" AMPLIFIER MODIFICATION. SEE DETAILS BELOW.
WITH THIS ANTENNA AND 100-125 WATTS I HAVE WORKED 48 STATES AND 46 COUNTRIES INCLUDING AUSTRALIA, ON 160 METERS IN TWO DX SEASONS. ON 17 METERS I HAVE WORKED ALL 50 STATES AND 107 COUNTRIES, IN ONE DX SEASON. KK4TR HAS WORKED 32 COUNTRIES INCLUDING AUSTRALIA, IN 2 MONTHS ON 160 METERS. NOTE FOR SWL'S- THIS ANTENNA IN IT'S PRESENT FORM AND LENGTH, MAKES AN EXCELLENT RECEIVING ANTENNA ON THE LONGWAVE, MEDIUMWAVE AND SHORTWAVE BANDS. HOWEVER, IT'S LENGTH CAN BE SCALED DOWN WITHOUT COMPRIMISING RECEIVE PERFORMANCE. AVAILABLE IN NEAR FUTURE- Detailed Discussion & Plans For:

KN4LF 160 Meter Indoor Receiving Loop
KK4TR 2 Meter High Gain Beam
1.28 Wavelength Extended Double Zepp, 3 DBd Gain!
Half Square Antenna, Phased Verticals With 4 DBd Gain!
Broadband Coaxial L (Not Inverted) For 160 Meters, With Dimensions For 80-10 Meters

ALL-BAND "L" ANTENNA DISCUSSION & PLANS

 
  Let me start off by stating that KK4TR and I don't make 
a claim that we have invented a brand new concept in vertical
 antenna design, though some of the combined design aspects 
of the antenna may be unique! We have simply identified the 
basic inherent weaknesses of your average city lot 1/4 wave 
inverted L and have devised methods to overcome these 
weaknesses. This antenna design is not a rival to a 4 
square vertical array but will outperform your average 
backyard 1/4 wave inverted L or dipole by leaps and bounds.


  KK4TR and I are not Electrical Engineers, just two 
voracious readers of every book on antenna theory and 
design that we can get our hands on, some 50 years old. As 
avid antenna experimenters, we have put 2 years of field 
experimentation into this antenna design! Along the way we 
have come to the conclusion that antenna theory is just 
that theory, concepts not yet completely proven by 
controlled scientific experiment and not to be taken as 
gospel! We have also concluded that alot of sound basic 
antenna theory and design has been lost to time and/or 
watered down, to the point that many Amateur Radio 
Operators are grossly misinformed about the basics.


  To be certain, an Electrical Engineer may come along and 
try to poke holes in some of the following antenna theory 
and concepts but one thing that can't be disputed is that 
the antenna is a proven informer! The average city lot 
backyard 1/4 wave inverted L suffers from several inherent 
weaknesses, high vertically polarized local noise pickup, 
absorption and pattern distortion of radiated signal due 
to surrounding ground clutter, high capacitive coupling 
signal loss between the antenna and your average poorly 
conducting soil conditions and low radiation resistance, 
a measure of antenna efficiency, due to the typically short (25-50 ft) 
vertical radiating element section of a 1/4 wave inverted 
L. With much effort the near field transmitted signal 
losses can be reduced to a point that you improve antenna 
efficiency to around 50% but the average backyard location 
makes it impossible to overcome signal losses in the mid 
field (1000-2000 feet) on 160 meters and signal losses in 
the far field (around 52,000 feet)(fresnel zone) is out of 
reach for all Amateur Radio Operators.


  The 160 meter linear loaded 1/2 wave L antenna places the 
highest current point at the top of the support structure 
gaining the following advantages. The elevated highest 
current point of the antenna is above the majority of the 
local vertically polarized noise field. At my QTH my 1/4 
wave inverted L noise level was always S9 to +5 over. With 
my 258 foot 160 meter linear loaded halfwave L, the noise 
level has been reduced to S2-3. Of course the actual amount
 of noise reduction will vary from QTH to QTH. Another 
advantage of elevating the highest current point is, 
reduced to nearly eliminated radiated signal absorption 
and pattern distortion, away from omnidirectional. In a sense 
you can say that the highest current point is getting a 
better omidirectional look at the radio horizon.


  Another advantage of elevating the highest current point, 
is the reduction of capacitive coupling signal loss between 
antenna and ground and gaining the advantage of laying down l
ess ground radials. Logic dictates that placing distance 
between the highest current point of the antenna and 
ground, reduces the coupling losses. The agreed upon 
standard for number of ground radials for a vertical 
antenna is 120 1/4 waves but you see a rapidly diminishing 
point of return after 16-20 1/8 to 1/4 wave radials. An 
alternative to ground radials is an eleveated counterpoise,
which will be covered further into the text.


  Radiation resistance, which as stated earlier is a 
measure of transmitting antenna efficiency is obviously a 
very important variable, basically the higher value the 
better. A 1/4 wave inverted L with a vertical section of 
50 feet, will have a very low radiation resistance, around 15 
ohms (very inefficient), increasing to near a theoretical 
36 ohms as you approach a vertical length of 1/4 wave. Take 
this 36 ohms of radiation resistance and couple it with a 
poor ground radial system and you still have a very 
inefficient signal radiator.


  There are several methods that can be employed to 
increase radiation resistance and henceforth transmitting 
antenna efficiency, excluding the laying out of dozens of 
ground radials. One is to raise 4 ground radials into an 
above ground counterpoise system. Four 1/4 wave wires 
approximately 15 feet off the ground, can rival 120 1/4 
wave radials on the ground, as far as transmitted antenna 
efficiency goes but not necessarily concerning absolute 
lowest radiation angle. Another is to lengthen the 
transmitting antenna. As mentioned earlier, in theory the 
radiation resistance measured at the end feedpoint of a 50 
foot vertical section of an inverted L is around 15 0hms, 
a 1/4 wave linear loaded L is near 30 ohms, a 1/4 wave 36 
ohms, a 3/8 wave 300 ohms and a 1/2 wave 1000 ohms, a very 
efficient figure indeed! Basically as you lengthen the 
radiating element the radiation resistance increases and it 
decreases as you shorten it, it also varies with the 
diameter of the radiator. Antenna input impedance varies 
according to where you feed it.


  So that's it in a nutshell, the 160 meter 1/2 wave "L" 
overcomes all the inherent weaknesses of the average city 
lot backyard 1/4 wave inverted "L". Now let's discuss the 
benefits of using the 160 meter 1/2 wave "L" on 80 through 
10 meters, as a multiband antenna. As the length of a 
transmitting antenna exeeds a fullwave on the operating 
frequency interesting things begin to happen. Gain starts 
to increase and the radiation moves inward towards the axis 
of the transmitting wire, versus the 90 degree broadside 
you see on a halfwave dipole. As the transmitting antenna 
continues to become even longer in comparison to the 
operating frequency, multiple lobes of radiation form on 
the wire in response to the numerous highest current points 
that exist. The following table lists by band the number of 
highest current points on the wire (1/2's), the increase in 
gain and the radiation angle with respect to the antenna 
wire axis, with 90 degrees being broadside to the wire and 
0 degrees being off the ends.

 

258 Feet Long Sloping at a 45 degree Angle 

FREQ KC   #1/2 Waves   Gain(dbd)   Rad. Angl
1845      1.01         0.0 @        90
3888      2.14         0.5/1.9*     52
7225      3.99         1.3/3.0 &    35
10115     5.58         2.2          29
14263     7.86         3.0          24
18139     10.00        4.0          21
21338     11.83        4.8          20
24960     13.87        5.6          19
28400     15.73        6.3          18

  @- some slight increase in gain over a 1/4 wave.
  *- collinear antenna, 2 1/2 waves in phase.
  &- 4 1/2 waves in phase.


  Using this antenna on 17 meters I have discovered that it 
is very user friendly antenna and with minimal time and 
effort I have been able to work many DX countries.


  It is strongly recommended that a parallel network tuner 
be used to load up the L antenna, as in a sense the tuner 
is part of the antenna. Also as a tuner will see 
approximately 10,000 ohms of feedpoint impedance your 
average store bought T network tuner can't deal with such a 
high impedance. My tuner consists of one 250pf variable 
capacitor and a 28uh tapped inductor.





  It is also recommended that the parallel network tuner be 
placed at the antenna end feedpoint, with a high quality 
run of Belden 9913/RG-8U or Belden 9258/RG-8X coax back to 
the radio shack. For 80 Through 10 Meter operation, it is 
recommended that you use 450/600 ohm ladderline from the 
antenna end feedpoint, to the parallel network tuner in the 
shack or as KK4TR and I do, forget a feedline altogether 
and bring the end of the antenna into the shack to the 
parallel network tuner. We realize that the no feedline 
concept is taboo in Amateur radio but it's a zero loss, 
highly efficient method that works very well. Attaching one 
1/4 wave radial for 80 through 10 meters, to the ground 
side of the parallel network tuner and tuning the radials 
for maximum current with the MFJ-931 Artificial Ground 
removes 100% of any stray RFI in the shack to zero. I have 
found a minor amount of shack RFI on 30,12,10 meters using 
the 258 foot L but have gotten rid of it easily using the 
above mentioned method. 73 and GUD DX from KN4LF and KK4TR. 

L.B. CEBIK, W4RNL says:
"Joe, 
Tell the disbelievers that WWVH uses elevated-feed vertical 
dipoles--and has had a heck of a signal for many decades. As 
I noted, you antenna is a form of vertical dipole with horizontal 
extensions rather than true hats. Hence, it is as good as any 
other vertical--and against some based fed versions, possibly 
better. Your ground wires essentially ensure a good rf ground 
between your gear and the antenna--always a good thing, but 
not likely to intensify signals. 
Enjoy the bands. 
-73- 
LB, W4RNL"

Article written by KN4LF
THE CLIPPERTON "L" LINEAR AMPLIFIER MODIFICATION
     The Clipperton "L" Linear Amplifier modification is quite an easy and worthwhile task to undertake. For many years these amplifiers have been used very sucessflly by the amteur community on all ham bands 160 thru 10 meters. The most common complaint was that there was not alot of output on the 160 meter band or for that matter some of the other low frequency bands. There were several reasons for this:

The tuned input circuit wasn't very well planned out. It worked quit well with the tube type rigs with their pi-network output circuits. They match the output impedence of the exciter with the input of the amplifier.
With the introduction and popularity of the transistor final rigs all of this changed. Now the name of the game was 50 ohms or reduced output from the exciter. Simple solution was to put a small antenna tuner (MFJ 900, 901 series) or even have an exciter with an auto tuner placed between the exciter and the amplifier. This solved the mismatch problem but it becomes necessary to retuned when the frequency as changed. Power output from the amplifier increases to about 700 watts as opposed to the orginal 200-400 watts before placing the tuner inline.This should take care of the problem most would say but it still falls short of the design perameters 800-1000 watts output!

   After some investigation it appears that the tank circuit on the amplifier had been detuned at the factory by design. It was probably done so the unit could be type accepted by the FCC. When the amp was first designed and built the amateur community was sharing the 160 meter band with many other services. We had severe power limitations and operating restrictions. In some areas very low power other up to 500 watts depending on the time of day. It just wouldn't make good business sense to build a product that would put out 1KW and expect the FCC to say "ok go build it but don't use it on 160 meters at full output". That would be like putting a "fox in the chicken house". Simply put the circuit was detuned to conform wth the rules of the day.
   To fix the problem in the tank circuit I `tried many things but none of them seemed to work to my satisfaction. I finally tried the the simple approach and "It worked". I added a transmitting capacitor(door knob variety) in place of the original value at C-16 on switch S1B(which is at the bottom and left of the switch) and a transmitting cap at C-15( which is just above on the same side) on switch S1B. The first was for 160 meters and the second was for 80 meters. A smaller value will probably be just as good for the 160m value but that is all I had at the time. Both of these values cascade on 160m so instead of the original value you have increased the capacity of the circuit by a great deal.
With these capacitors installed the load control on both 80 and 160 meters worked to abot mid-scale. Before the modification the load control would be turned down to the extreme low end of the tuning range of the variable capacitor(Max Capacity). With these two modifications my output power went from 750 watts peak out to very near 1250 watts on the high voltage tap(SSB). This very close to the design parameters of four 572 B tubes in parallel. I hear "THE FELLAS IN THE BACKROOM" saying right now " It´s too simple, I don´t believe it, He went about it all wrong, You need to add inductance not capacity". Well all I can say to the disbelievers is that it works come down to 160 meters and listen to me work the DX with the Clipperton "L" amp and the TS 850sat. I´ve included some photos and a hand drawn schematic to show the positioning of the parts. Any other questions just send me an email. Otherwise just have fun operating this piece or resurrected old gear.

Schmatic and Top View Of Amplifier

For further information about anything I have mentioned here please contact me at: k4tr@bellsouth.net or
K4TR Antenna Mfg and Sales

Article Written by K4TR

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