K6ARK Antenna / G90 Back Yard Portable

 23 Feb 2022

With the temperature in the 50 degree F today, I decided to play radio in the yard to see if the K6ARK antenna kit I built as a 9:1 UnUn for an EFRW would tune up on the Xiegu G90 ATU.

AB1OP Minimal Portable Operation Bag

I am happy to report the Xiegu G90 was able to tune the K6ARK 9:1 UnUn EFRW to under 1.5 to 1 on the 80, 40 and 20 meter bands. I didn't do much else I played with the Xiegu G90 CW decoder on a couple transmissions running at 20-25 wpm at that speed my head can only tell that CQ was sent and a few scattered letters here and there.

AB1OP Portable Operations Equipment:

A) A medium capacity tactical style backpack ($40)

B) A 6Ah LiFePO4 battery ($30)

C) Old Android 4.4 KitKat 7" Tablet with VLS logger App ($50 back in 2014?)

D) 6000mAh USB power bank ($10) located between tablet and G90

E) DIY PVC Antenna winder (~$2)

F) Xiegu G90 20W Transceiver & Microphone ($450 new)

G) Earbuds ($1)

H) DIY CW paddles ($1.50 for stereo plug & PCB) on top of G90

I) DIY 9:1 UnUn in 80mm X 50mm plastic box. ($20 in materials)

J) DIY F connectors to Power pole connectors cable ($5)

K) Power Meter with Power pole connectors ($16 meter, $5 connectors)

L) DIY Fused power pole to white male connector cable with clamp on ferrite choke ($10)

M) K6ARK Kit as built to 9:1 UnUn modified for G90 ($20 kit, $5 mods)

Not Pictured:

N) Antenna wire 26awg 41 feet, Counterpoise wire 26awg 17 feet ($13 / 100 feet)

O) Two 7.2 meter (~21ft) telescoping Carbon Fiber fish poles. ($13 + $6 shipping each eBay - up to 4 weeks wait for delivery from China)

P) Strong and light cord 50-100 feet ($4-$7)

Q) Bungee cords to tie poles to stationary objects ($7)

Compare the size difference from the K6ARK and the M0UKD 9:1 UnUn

Here we can see the size difference of the two 9:1 UnUn(s) used for an EFRW antenna.

The K6ARK (attached to G90) extends only 1.25 inches beyond the UHF-BNC adapter.

The M0UKD (atop G90) extends almost 5 inches beyond the UHF-BNC Adapter.

Granted the M0UKD UnUn is built around a T130-2 toroid and a 80mm by 50mm project box. It has a lot of empty space in front of the toroid and the 4mm banana jacks protrude excessively out the front and the side. 

I will keep the M0UKD UnUn if I ever get a small (100W or less) linear amp for my rigs. 

The success of the K6ARK kit build is enough to order a 2nd K6ARK kit to be built as a 49:1 UnUn EFHW antenna to replace a project box built 49:1 UnUn based on a ft140-43 toroid. I already have the ft82-43 toroid, plenty 26 awg magnet wire and 1 inch diameter heat shrink tubing needed to modify the kit to the G90 power level. 

K6ARK Antenna Kit

 17 Feb 2022                                                                                        Ralph AB1OP 

K6ARK Adam is an active SOTA QRP operator. He has developed a small QRP Antenna (Matching) Kit currently sold on Amazon. The kit comes with your choice of either a Male or Female BNC connector as the feed point.

On his web site he has instructions of how to build the kit in one of three different configurations; 

1) 49:1 UnUn for EFHW End Fed Half Wave 

2) 9:1 UnUn for EFRW End Fed Random Wire 

3) 1:1 BalUn for a Dipole.

Website: https://k6ark.com/

My Build: A 9:1 UnUn for EFRW antenna

I decided to purchase a male BNC kit. I need to modify the kit
to handle the maximum power  my Xiegu G90 can produce (20W). I will build it as a 9:1 UnUn for a EFRW antenna to take advantage of the G90 built in ATU. 

K6ARK Kit (Male BNC Version)

 K6ARK Adam suggested for G90 use, adding an FT82-43 toroid to nest the FT50-43 toroid into. The combined toroids would increase the power handling to 30 Watts. 

Adam offered to send me additional 26 AWG magnet wire since the kit supplied 28.25 inches of wire. I had plenty on hand from other projects. I calculated I need at least 36 inches, I cut off 40 inches from my stock as insurance.

Replaced the 3/4 inch heat shrink tubing supplied in the kit with a 1 inch diameter piece of heat shrink tubing and added some additional small diameter pieces to tubing as needed. 

I also purchased some 2mm banana connectors to attach the radiating and counterpoise wire elements.

Additional pieces to modify kit for my G90
The female BNC was used as a heat sink when soldering the male BNC
Notice the 3.5X reading glasses 

 Following K6ARK instructions from his website I was able to complete the kit.

I did have to bring out the "helping hands" to hold on to the PCB while soldering.

a) Soldered the radiating and counterpoise leads to the PCB and pulled the leads thru the strain relief holes provided in the PCB.

b) Wind the 10 turns, twist a tap, wind 20 turns on the combined toroids.

c) Burned off the enamel on the three toroid leads. Arrange the leads to match the holes in the PCB and solder. 

d) Tilt the toroid windings and solder the male BNC to the PCB. 

e) Shrunk Tubing over the assembly to cover and protect the windings. 

f) soldered 2mm banana connectors on the short wires for antenna and counterpoise wires.

I also soldered 2mm banana connectors on a 41 foot 26 awg wire for the antenna and on a 17 foot 26 awg wire for the counterpoise. I shrunk red HS tubing on the antenna connectors and black HS tubing on the counterpoise connectors.

Complete EFRW antenna on a 1/2" PVC wire winder
The short PVC sections can be detached and used as insulators

Compare the new K6ARK EFHW portable antenna system with my portable HB EFHW system used during the 2020 ARRL Field Day.

HB EFHW compared to K6ARK EFRW
Green spool of support cord and UHF(PL-259) to BNC(female) adapter is common to both

HB EFHW consists of 

a) 49:1 UnUn based on a ft140-43 toroid in project box with a female BNC.

b) ~66 feet of 18 awg wire on a 9" spool.

c) 25 foot RG-8X coax with BNC male to male.

d) Large insulator to tie antenna wire to support cord.

e) UHF(PL-259) to BNC(female) adapter.

f) 100 foot spool of strong cord for support line.

K6ARK EFRW consists of:

a) 9:1 UnUn based on a combined ft50-43 & ft83-43 toroids on a male BNC kit.

b) 41 feet 26 awg wire.

c) 17 feet 26 awg wire.

d) 1/2" PVC wire winder, one of the short pieces can be detached and used as an insulator to tie the antenna wire to support cord. 

e) UHF(PL-259) to BNC(female) adapter.

f) 100 foot spool of strong cord for support line.

In Conclusion: With Adam K6ARK antenna matching kit you have the smallest, lightest feed point connector possible, you can leave the heavy coax cables and large gauge antenna wire in your shack. If portable QRP operation is your thing whether atop a mountain summit, sitting of a park bench or just hanging out in your backyard you will enjoy using this kit.