Pacific Antenna 40m – 15m SOTA Tuner
Parts List
Inventory Component
Quantity Note
SWR Indicator Kit
1
SWR Bridge Kit
T50-6 toroid
1
Yellow toroid core
Polyvaricon
1
Variable Capacitor
Polyvaricon shaft screw
1
2.6 x 12mm Phillips pan head screw
Polyvaricon mounting screw
2
2.6 x 4mm screw
Polyvaricon shaft
1
3/8” white Nylon standoff
6-32 screw
2
3/4” Stainless phillips pan head screw
#6 lock washer
2
Stainless
#6 flat washer
2
Stainless
6-32 wingnut
2
Stainless
#6 nylon step washer
2
Nylon, white
#8 nylon flat washer
2
Nylon, white
#6 tinned solder lug
2
Solder Lug
6-32 nut
2
Stainless
4-40 screw
2
1/4” Undercut flat head
BNC
1
Female, chassis mount
1/4" shaft knob
1
Black plastic knob
#26 magnet wire
24”
Red or Green #26
Hook-up wire
18”
#22 or # 24 AWG, two colors, 9” each
SOTA chassis
1
Aluminum, unfinished
SOTA decal set
1
Waterslide decal sheet
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Inventory
First, familiarize yourself with the parts and check for all the components by using the above table to
inventory the kit.
Assemble the SWR Indicator Kit.
Complete assembly instructions are located on-line at http://www.qrpkits.com/swrindicator.html .
The last component to solder to the SWR board is the LED. Use the above dimensions to
locate the lip of the LED, and adjust the inside nut of the switch, for the correct fit to the chassis.
Set the SWR indicator aside, for now as the rest of the assembly is done inside the chassis.
Prepare the chassis
Thoroughly clean the surface of the panel to remove any oils or contamination.
TIP: We have found that moving the decals into position on a bare aluminum chassis is sometimes
difficult, due to the brushed surface, so we recommend either painting or pre-coating the chassis with
Krylon clear, or a similar clear coating, and allowing the coating to thoroughly dry before applying the
decals.
Decal Application
The supplied decals are known as water slide decals. An example video of how to apply these types
of decals can be found here: https://www.youtube.com/watch?v=Pr5R9VCNVHU
It is recommended to apply the decals before mounting anything to the chassis.
Use the above picture as a guide for the correct spacing of decals around the holes to prevent any
labels being covered by a knob or switch.
Cut out and trim around each group of text or symbols you wish to apply. Trimming doesn’t have to be
perfect as the background film is transparent.
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After trimming, place the decal in a bowl of lukewarm water with a small drop of dish soap to reduce
the surface tension for 10-15 seconds.
Using tweezers, and carefully handle decals to avoid tearing. Start to slide the decal off to the side of
the backing paper, and place the unsupported edge of the decal close to the final location.
Hold the edge of the decal against the panel, with your finger, and slide the paper out from under the
decal. You can slide the decal around to the right position, as it will float slightly on the film of water.
You may find it helpful to use a knife point or something sharp to do this.
When in position, hold the edge of the decal with your finger and gently squeegee excess water out
from under the decal with a tissue or paper towel.
Working from the center, remove any bubbles by blotting or wiping gently to the sides. Take your time
and do this for each decal.
Let the decals to dry overnight, and you can speed up this process by placing the chassis near a fan.
When completely dry, the decals should be sealed and protected by spraying at least two light coats of
a clear matte finish, such as Krylon, or other similar products to. It is important to apply only light
coats and to allow each coat to completely dry between applications
Once the final clear coat has dried thoroughly, continue as follows:
Assemble the two antenna connections and the bnc connector to the chassis cover.
NOTE: The nylon step washers are used to keep the antenna connections insulated from the chassis.
Position the solder tabs as shown below, and angled down slightly, so that the antenna lug does
not short against the PEM nut when the case is assembled.
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Check that there is no continuity between the solder tabs and the case at this point. This is to verify
that the insulating washers were installed correctly.
Wind L1
Using the T50-6 yellow toroid and the enclosed magnet wire.
When complete, L1 will have a total of 23 turns, with a tap at 3 turns from
the “START” end.
Remember, every time the wire passes through the center of the toroid,
counts as one turn.
Pre-wire the Poly-varicon
As shown with 2” pieces of the hook-up wire to put the two sections of the
poly-varicon in parallel.
At this time, adjust the small trimmers on the
back of the polyvaricon for half engagement.
Mount the shaft and center screw
provided on the polyvaricon
Put a small piece of double sided tape on the back of
the poly-varicon. This will act as a surface to secure
the toroid.
Wire only the two ends of the toroid winding to the
poly-varicon as shown, Leave the tap unsoldered for
now.
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2 SIDED
TAPE
Pre-wire the previously assembled SWR indicator as shown with 3”
long pieces of hook-up wire.
Install the pre-wired SWR indicator as shown, and secure it to the
chassis with the remaining toggle switch nut.
Final Assembly Steps
The above diagram and photo will assist with making the final connections to complete your SOTA
tuner:
Mount the poly-varicon/toroid assembly to the chassis cover with the two 2.6 x 4 mm screws.
Solder the wire from the center connection of the poly-varicon to the counterpoise lug.
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Solder the wire from the side connection of the poly-varicon to the antenna lug.
Solder the “ANT” wire from the swr indicator to the toroid tap.
Solder the “TX” wire from the swr indicator center connection of the BNC connector.
Solder the “GND” wire from the SWR indicator to the BNC ground lug.
TIP: Before proceeding test with the toggle switch in the “OPERATE” position to be sure there is no
continuity between the wingnuts and the case.
Solder a wire from the BNC ground lug to the counterpoise ground lug.
Fit the bottom half of the case to the top and secure it with the two flat head 4-40 screws.
Install the knob on the poly-varicon shaft using the knob set screw.
Congratulations this completes assembly of your SOTA Tuner!
Optional label for back of case
If you want to have this chart on your tuner, print out the above labels and scale when printing as
necessary to fit the bottom of the chassis.
Three sizes are provided to approximate the correct size to fit the case regardless of you printer
scaling.
We recommend protecting this label with a piece of clear packaging tape, or peel and stick laminate
film.
You can attach it to the back of the case with two-sided tape.
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Using your SOTA Tuner
Start with a light weight wire a few inches longer than the lengths suggested for the band you wish to
operate and test to see if a good match can be achieved as indicated by the LED completely
extinguishing as the tuning knob is turned over its range. If not, shorten the wire in one inch
increments and retest.
Note: The values provided in the table above are suggested starting points, not absolutes and your
wire lengths may vary due to many conditions.
Note: Some users use short counterpoises of approximately 0.1 wavelength successfully with endfed
half wave antennas.
The condition and nature of the ground as well as the angle of elements in respect to ground, can all
affect the overall length wire needed to achieve a good match.
We recommend that you test the SOTA tuner and note what works best for your conditions.
How the wire is deployed will depend on what is available for support such as trees and/or
structures.
The simplest configuration is an inverted “V”, where the active element runs from the antenna
connection of the tuner, up to a tree branch, and back down towards the ground.
An “L”configuration for the active element is somewhat better for DX, especially if you can get the part
of the wire from the tuner up as vertical as possible.
If the wire is run horizontally and fairly close to the ground, the signal will mostly be directed upward
and therefore will be better for close in contacts, especially on the lower frequency bands.
Try to keep the counterpoise 180 degrees from the active element.
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Schematic
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