1. 7/9/2019
July 1, June 30, 2018

2. Field Day Antennas, June 2018
7/9/2019
Field Day Antennas, June 2018
80m CW
Phone
40m
Digital
10m
Dual
15m
20m
This is the array of wire antennas we used for field day.
Starting at the North, or lower end of the line we have the following antennas
40 Meter Phone Delta Loop
15 Meter All Use Delta Loop
80 Meter CW Quad Loop
20 Meter Phone Delta Loop
40 Meter Digital Quad Loop
20 Meter CW Quad Loop
10 Meter All Use Delta Loop (this one was not set up)
80 Meter Phone Quad Loop
20 Meter Digital Delta Loop
40 Meter CW Delta Loop
And from the 40m CW mast, a 160 Meter All Use Dipole
7/9/2019
July 1, June 30, 2018

3. Field Day Antenna Tuners, June 2018
7/9/2019
Field Day Antenna Tuners, June 2018
Since all loop antennas were to be fed with 450 ohm ladder line, it was determined that each antenna should have it’s own antenna tuner and it’s own bandpass filter.
However, the club owned only one 160 meter and one 10 meter bandpass filter. For 80m, 40m, 20m and 15m we had two for each band. The shortage is because all filters were purchased prior to the need for separate digital stations.
As a result, at the direction of the President, a single 40m bandpass filter was purchased and added to the club’s collection. This still left us short one 20m bandpass filter. We therefore opted to use the beam antenna for 20m CW as it was further from the other antennas and would need the filter the least.
Since all loop antennas were to be fed with 450 ohm ladder line, it was determined that each antenna should have it’s own antenna tuner and it’s own bandpass filter.
However, the club owned only one 160 meter and one 10 meter bandpass filter. For 80m, 40m, 20m and 15m we had two for each band. The shortage is because all filters were purchased prior to the need for separate digital stations.
As a result, at the direction of the President, a single 40m bandpass filter was purchased and added to the club’s collection. This still left us short one 20m bandpass filter. We therefore opted to use the beam antenna for 20m CW as it was further from the other antennas and would need the filter the least.
July 1, June 30, 2018

4. Commercial Tuner Designs
7/9/2019
Commercial Tuner Designs
In case you don’t know most antenna tuner’s currently in production for the Amateur Radio market are based on either the T Design, shown in the upper left, or the Pi Design shown in the upper right. These two tuners are unbalanced IN and umbalanced OUT, and unsuitable for use with 450 ohm ladder line.
Our tuners must provide a balance output. The cheapest and easiest way to get this balanced output is to slap a 1:1 Balun on the output of the tuner, creating the two tuners shown on the lower left, and lower right. Those tuners work. Usually.
There is only one problem. The impedance of the antenna must be handled by the Balun, as the voltage to current ratio is converted from 50 ohms at the transceiver to the needed impedance, at the end of the T or Pi network but before the Balun. That can mean high voltage low current at the Balun, and if that needed impedance is too high, the torroidal core in the Balun saturates, and the tuner stops working.
You can however fix that, by buying a more substantial toroidal core, at a more subtantial price.
The balanced tuners above can be subject to core saturation at high SWR resulting in tuner failure!
July 1, June 30, 2018

5. Link Coupled Tuner Designs
7/9/2019
Link Coupled Tuner Designs
Next I looked at Link Coupled Tuners. The one in the upper left came from the ARRL Handbook where it was published for many years. The Handbook recommended the replacement of the movable primary coil, making it more like the upper right design, which shows series capacitors in the primary circuit. These are used to adjust the coupling between primary and secondary.
Moving to the lower left, we see taps being used to adjust the output, and in the lower right link is the design I settled on. This is a true balanced tuner. If I had only paid more attention to the movable taps.
Years ago I built such a tuner. At that time I set up the antenna, and used alligator clips to determine the exact placement of the taps for each band. Thus my tuner was built custom for the antenna on which it was used. I had been told that loop antennas generally exhibited an impedance of around 110 ohms. So I used feed lines that were multiples of ½ wavelength adjusted for the velocity factor. I believed I would then see 110 ohms at the tuner, and the antenna tuners were tested and adjusted for use with a 110 ohm dummy load.
We pre-tested 3 of these before Field Day and the results were fairly good.
July 1, June 30, 2018

6. Fairly Good is Not Great!
7/9/2019
Fairly Good is Not Great!
So that was what we got for results at Field Day 2018, fairly good.
On some rigs the SWR went down to 1:1, on others 1.5:1 was closer to the best we could do. On other antennas it was 2:1.
And without being able to relocate the taps, we could not get all rigs down to 1:1 or operation.
Next I looked at Link Coupled Tuners. The one in the upper left came from the ARRL Handbook where it was published for many years. The Handbook recommended the replacement of the movable primary coil, making it more like the upper right design, which shows series capacitors in the primary circuit. These are used to adjust the coupling between primary and secondary.
Moving to the lower left, we see taps being used to adjust the output, and in the lower right link is the design I settled on. This is a true balanced tuner. If I had only paid more attention to the movable taps.
Years ago I built such a tuner. At that time I set up the antenna, and used alligator clips to determine the exact placement of the taps for each band. Thus my tuner was built custom for the antenna on which it was used. I had been told that loop antennas generally exhibited an impedance of around 110 ohms. So I used feed lines that were multiples of ½ wavelength adjusted for the velocity factor. I believed I would then see 110 ohms at the tuner, and the antenna tuners were tested and adjusted for use with a 110 ohm dummy load.
We pre-tested 3 of these before Field Day and the results were fairly good.
July 1, June 30, 2018

7. 7/9/2019
The Fix is Never Easy
Now if we could just add a rotary switch to each tuner, and allow it to select the various taps, our problem would be solved.
Because our secondary windings are inside our primary windings the coils would have to be completely rebuilt to accomplish this.
So it may be time to redesign the Field Day tuners.
It may be easier to redesign the tuners than to fix the current design.
But I’ve been doing some reading on another balanced tuner design…….
July 1, June 30, 2018

8. Z-Match Tuner Designs 7/9/2019
What you are looking at is a Z-Match Tuner in two variations. Like our 2018 tuners it requires no Balun.
In the upper diagram you will see there are two sets of outputs. One for 80 through 30 meters and one for 20 meters through 10 meters. It requires the same single input capacitor, and split stator output capacitors that the 2018 tuner had. It simply requires a coil redesign and some wiring changes…. and of course a re-design and re-build of the coils.
The lower design is even better. It covers all bands 80 meters through 10 meters with a single balance output. I may require a second short coil depending on the band’s to be used by the particular tuner, but that should not be difficult.
July 1, June 30, 2018

9. 7/9/2019
Z-Match Tuner Designs
According do DJ0IP, the advantages of the Z-Match are….
Relatively simple circuit
Low Cost components
Ease of tuning
And the disadvantages are….
Efficiency goes up with higher SWR’s
High SWR can mean high voltages, requiring feed line length modifications, or higher voltage rated capacitors
The is no commercial source for this design.
Assuming you can adjust feed line lengths to avoid very high SWR and very high voltages, this appears to be the tuner of choice.
July 1, June 30, 2018

10. 7/9/2019
Other Choices
Balanced L-Network – requires a pair of matched synchronized roller inductors. Very expensive.
Balanced T-Network – each tuner requires two sets of identical capacitors ganged together. Also somwwhat expensive. Can be misadjusted for high loss. (MFJ-974B)
Balanced Pi-Network – again requires a pair of matched synchronized roller inductors. Very expensive.
Link Coupling – will require rotary switch and new coils
S-Match – new design, uses two torriodal cores but has interesting possibilities
Best I can guess the S-Match is our only other possibility.
July 1, June 30, 2018

11. 7/9/2019
The S-Match
This design requires 2 toriodal cores for each tuner. Using two of the T200-2 its good for about 1000 watts. You can also use one T300-2 instead. FYI: The T200-2 made in US goes for $9.45 including shipping from Ebay. $6.50 from China. Amazon wants $8.
Unsure how this design will work with switchable rather than a continuously variable inductor.
Frequency coverage depends on the components used.
I some situations the antenna must be moved from the inductor side of the S-Match to the capacitor side.
Nobody including the ARRL or another 3rd party has verified the efficiency or losses of the S-Match.
In other words this is experimental stuff. But it could make a nice home project though.
July 1, June 30, 2018