Thursday, September 23, 2010

QRP End Fed Tuner Kit

A few months ago KI6J mentioned he was going to do a kit of his end fed tuner that he designed for SOTA use and it came last week.  Here are his pix of the kit.  Mine went together this far with no problems and I am looking forward to getting it finished and tested with one of the QRP rigs here.

Parts included in kit

Top Side of board with 3 bridge resistors
My tuner build

Bottom of board with tapped inductor, switch and polyvaricon

KI6J SOTA Station Tuner in upper right of pack, rig is ATS-3

4/4/2011  Still have not actually field tested the tuner however I noticed that Stu said he still had a few of the kits left for $25 shipped.  Contact him at

9/2910  Added the 5100 ohm test resistor to the output and tried it with the MFJ 259B set to 40M.  A nice dip was obtained in both switch positions.  With the bridge 'in circuit' the Analyzer read about 1.5 and with it switched out it read about 1.2 to 1.  This was done holding some of the connections and it was somewhat sensitive to hand position.

Schmatic of End Fed Tuner de KI6J

Post taken from AT Sprint Yahoo Group

To all:  here's a link to three pictures related to KI6J's little, teeny, efficient and just down right cute end fed half wave antenna tuner:

One pic is a snap shot of the antenna analyzer's view for the original prototype version - Stu, KI6J, told me today that improving the parts layoout in Version 2 has reduced the reactive component to nearly zero, but I don't have a copy of that snap shot to share!
One picture shows Version 2 - the tuner and SWR bridge assembled and installed in a small project box - darn cute little thang!!
The last picture shows just the tuner board in the ugly style of construction.
Stu is commiting to produce 100 kits for the EFHW tuner with built in SWR bridge.  He has found a source for all of the components and is working on the PCB artwork now.  He expects to have the kits - tuner and SWR bridge - available by the first week of August 1, and expects the kit to sell at $30 plus shipping.  Note: the board is being designed to fit in the Radio Shack 2x3 inch project box ($3 at radio shack) but the builder will have to provide the enclosure and RF connector of choice.

He also has available, at this time, a few tuner-only boards, already built, like the one in the picture with the quarter for size reference.  Note: this board does not include a SWR indicator but is a ready-to-go end fed half wave tuner for 40 through 15 meters and is priced at $18 per board, plus shipping. You supply an enclosure, connectors and SWR indicator and you are good to go.
Thanks to all that have already contacted Stu and myself, and others interested in this end fed halfwave tuner - it works GREAT! I've got one and find it to be the easiest antenna system to set up, tune and get operate.
Stu's e-mail address is:  ki6mwn@... and you have mine.  Please let Stu and I know of your interest in purchasing one of these sweet 40-15 meter end fed half wave tuners; notifying him/I will make it easier for Stu to plan his off-work hours accordingly and have the tuners ready as close as possible by that first week in August - if that date slips more than a couple of days, Stu or I will notify you individually.  If you have technical questions, address those with Stu.
Please pass on, as appropriate, to other hams you interact with and think might be interested in this tuner and SWR bridge.
Best regards, Jim Rodenkirch, K9JWV
Disclaimer:  I have no financial interest in this endeavor - Stu and I are friends and I appreciate all he's done to get this end fed halfwave system up and running; I, simply, believe in this product, LOVE how it works for me and want to share it with other QRPers!  I, probably, will handle the shipping of the orders for Stu as there is no sales tax for out of state deliveries here in Utah; whatever my shipping costs are to your specific locale will be the cost to you.

Note added Sept 2, '11
Hendricks now has a very similar kit see Hendricks SOTO EFHW


VE3WDM said...

Very nice picks of the assembly and do post about how things work.

Jack Jones said...

Hi, great info Pls check my Tube QRP site, I'm sure you like it. Here’s the link:

John Leonardelli said...

Thanks for the great post and the schematic. Looks like a nice build for a pocket SOTA tuner.