I have a new K3S/100W with internal ATU (KAT3A) as well as KRX3A SubRX. My antennas are a 102ft G5RV at 40ft with LDG RC/RT-100 Remote ATU at base, and I’ll have a DXE-MBVE-5 43ft vertical with MFJ-927 Remote ATU at base after completing this weekend.
A few questions:
1. How to best use the K3S internal ATU in conjunction with the Remote ATUs? Both can be used in Bypass mode, the K3S by command and the Remote ATUs by removing Bias-T voltage. The LDG rATU on the G5RV is “latched” in the last LC configuration before removing Bias-T voltage – still learning about MFJ-927. It seems that I might first put the K3S in Bypass, remote tune, and then if >2:1 SWR, remove voltage from Bias-T to “latch” the remote ATU, and then engage the K3S internal ATU to try and lower SWR to <2:1. Added loss, but maybe better than K3S power fold-back. But that’s where I need advice.
2. I’ll set up for “Diversity RX” when I figure which antenna should be my TX antenna, which might change based on band and direction (G5RV is N-S, and even at 40ft, reaches E-W better than N-S). In this case, I wonder if I could tune my SubRX “Diversity RX Antenna” with remote ATU for better reception?
I have a K3 without the internal ATU and use a MFJ-927 remote tuner for my ZS6BKW inverted V. I also have a manual tuner in the shack which is usually in bypass, just monitoring power out and incoming SWR. There some parts of 40m where the MFJ-927 doesn't get a good match and I touch it up with the manual tuner to keep the K3 happy. I don't see why you couldn't take a similar approach with the KAT3A.
The MFJ-927 is a finicky beast but it has served me well for over 4 years. I don't think it uses latching relays so you have to keep it powered to use it. I could be wrong. GL!
With G5RV you can extend the flat line to the shack and use KAT3 directly via 1:1 or 4:1 balun. Probably as good as the current choice.
With 43 ft vertical a tuner at the base is critical to performance and KAT3 may in some cases be detrimental.
Check the signal reports with both antennas. At my QTH verticals nearly always are 10db down from dipoles even for DX, except when dipoles have nulls. In this case your better option is adding an extra G5RV perpendicular to the first G5RV, also fed by flat line.
I found diversity important for 160 and 80m but not much at higher frequency.
The tuner and G5RV are close to $400. For 10-20m, a $500 hexbeam will blow either G5RV or a vertical away although a mast and space are needed.
On Thu,8/4/2016 9:16 AM, Ignacy wrote:
> With 43 ft vertical a tuner at the base is critical to performance
It is FAR more complicated than that. Antenna tuners provide a match
between a transmitter and a feedline, or between an antenna and a
feedline. Like antennas like the G5RV, a 43 ft vertical is WILDLY
mismatched to 50 ohms on most bands, which makes serious matching at the
base important. HOWEVER -- it has been shown that if the feedline is of
high quality, like 1-2-in hard line; and 2) if it is fairly short (less
than about 50 ft); and 3) some matching is done at the feedpoint, a
tuner in the shack can match the antenna to the transmitter and feedline
loss will be sufficiently low that it's not an issue.
I've studied the 43-ft vertical, and reported on what I've learned in
this set of Power Point slides for a talk I did several years ago at
> and KAT3 may in some cases be detrimental.
I cannot imagine the logic behind this statement.
> Check the signal reports with both antennas. At my QTH verticals nearly
> always are 10db down from dipoles even for DX, except when dipoles have
The relative performance of horizontal and vertical antennas is STRONGLY
dependent on 1) soil conditions; 2) their height; and 3) for verticals,
their counterpoise/radial system if they need one. An HF vertical
mounted at roof level will outperform the same antenna mounted at ground
level, and the degree of outperformance will depend on soil conditions.
Some verticals are fundamentally dipoles, and do not need radial
systems, so they are easy to put on a roof. The R8 and AV640 are
examples. Other verticals that are designed as quarter wave antennas
with loading coils DO require radials, so if you put them on a roof, you
need at least one for each band where plan to transmit, and two per band
> In this case your better option is adding an extra G5RV
> perpendicular to the first G5RV, also fed by flat line.
I'm not at all a fan of antennas like the G5RV, primarily because they
cannot be choked to kill RX noise. Adding another one would be a bad
move. Far better are antennas like resonant fan dipoles fed with coax,
and yes, if you can, place two at right angles. Resonant, coax-fed
antennas CAN be effectively choked, so RX noise can be lower. You can't
work what you can't hear!