Thanks for the question, The 1.2k fx will put out 650 to 700 watts through the tuner tuned (1:1) to the dummy load. Depends upon how hard I drive it. When the output is low, as with the antenna system, additional drive does not improve the situation. My dummy load is a little light so I can't drive it too hard or to long.
73,
Rob

Good Day,
I am running a THP 1.2 Kfx The amplifier is fine into a dummy load. Here is the issue, I run tuned feeders, 18 ga ladder line ~~ 137 ft., via a Palstar AT2K and a DX Engineering 1:1 balun on the output. The balun is connected to the tuner by about 6" of RG-8 size cable. What I find is that even with the tuner showing a 1:1 match (also on my MFJ 259B) the amplifier output is reduced by 200 watts or so, it varies from band to band, as read on the tuner metering. If the antenna is resonant at that frequency the power output is higher. This condition is most noticeable on 80M and 40M. I have pruned the antennas and just gotten the resonant point in the 80M band at 3.540. The VSWR being above 8:1 at the top end of the band, I'd like to shift the resonant point to the center of the band or a bit below.

So, I have two issues, can I shorten the ladder line a bit to raise to resonant point rather than continue to trim, (shorten) the antenna? Why is the power reduced when the amplifier should be seeing 50 ohms (J0)?

Thanks es 73,
Rob WA9UAA

I switch my ladder line to ground when not in use for lightning protection. There are also two 100K Ohm wire wound resistors to ground to bleed charges off of the line. I have heard of power pole connectors being used to manually switch ladder line as well. HTH
73,
Rob WA9UAA

This may answer your question, the gain of the loop antenna is a function of the area inside the loop so a circle is best, followed by a square, delta shape etc. There are also loops with the plane in a vertical attitude which work best in two directions at the fundamental  frequency.  HTH
73,
Rob WA9UAA

Good Day,
I have never owned an FT-920 but they have been called sleepers, (good rigs). The FM board was extra, so check on that before buying. I believe the filters were extra, check on those as well. I want to try any used rig before I bought! 73,
Rob WA9UAA

Thanks to all that replied, the resulting discussion was worth the effort . I have about 140 ft of ladder line out now and will simply add the ZS6BKW dipole to my existing 160M dipole.
73,
Rob

Thanks to all that have replied, I don't see that there is a length where the original 5 frequencies will combine at any other ladder line length. I have been running R.J. Edwards Dipole 3 calculator. perhaps a newer calculator . . . .
73, Rob

Thanks Mike, I want to know where I can replicate the 50 Ohm impedance point further along the ladder line at greater than 40 feet in length. 73, Rob

Good Day,
Something I haven't seen covered with this antenna is being able to replicate the 50 Ohm impedance point on a longer piece of ladder line (If possible) while maintaining the ZS6BKW antenna length. I am already running one ladder line fed antenna and need this to be coax fed. I'd like to reduce the coax length to reach the ZS6BKW antenna by using a longer piece of ladder line ( construction issues too) and then transition to coax. For that matter,  I have 1:1, 4:1, and 9:1 baluns available TIA
73,
Rob

^^^^^^^^^^^^^^THIS!^^^^^^^^^^^^^^ and use the mulch!
73,
Rob

Duh, got me there 73, Rob

Hi Mike,
I am not sure I fully 'get' the question but will take a stab at it. If you are looking for the best place on the water fall for PSK 31 and are using a rig with a standard SSB filter then 1500 Hz is good in that if there are any 2nd harmonics at 3000 Hz the band pass filter in the radio will wipe that out. Lets say your rig has a RTTY filter position. With a correctly tuned in radio the RTTY tones are going to be in the neighborhood of 2210 Hz. In this case you will want to match this setting on the water fall. HTH
73,
Rob WA9UAA

Hi Greg,
Short answer is yes. The reason you were still getting zapped on 80 meters is that the 62 feet of wire is a 1/2 half wave on 80 meters which would be high impedance fed again. 31 feet of wire might have done the trick hihi but the dipole you have is a better solution. Let us know how it works now
73,
Rob WA9UAA

In a practical sense, if possible, run the ladder line all the way to the tuner. Coax, because of it's high capacitance/ ft. makes larger changes about the Smith Chart for almost any length compared to ladder line.
73,
Rob WA9UAA

Hi Greg,
The antenna is being voltage fed on those bands where the rig is biting you. The fix is a counterpoise of 1/4 wavelength ( 234/f  = length in feet) of wire attached to the ground lug of the tuner for each of the offending bands. These wires will move the high voltage point away from the rig and it will appear at the end of the counterpoise wires. These ends should be well taped (insulated) to protect from electric shock. The wires can be run outside or inside the radio shack but must be well insulated. Ideally they should be run away from the antenna as they will become part of the antenna system. If the angular difference is greater than 90 deg. no problem.

Alternatively, the W3EDP antenna with a radiator of 84 feet and a counterpoise of 17 feet for the low bands and one of 6 and 1/2 feet for the upper bands is a possible solution. These lengths are more easily matched and worth your time to try.

73,
Rob WA9UAA
http://www.mds975.co.uk/Images/amateur_radio/w3edp.gif