project from Steve
The project / schematic can be found here:
HENDRICKS QRP KITS
Steve 'Melt Solder' site: KD1JV
Please see all the projects on this great site.
You may purchase the Tenna Dipper kit from QRP KITS,
or homebrew it as I did, with some modifications.
It is used to
1) what frequency is at 50 OHMS on your antenna
2) assist in trimming the length your antenna for a given frequency.
It is a Wheatstone bridge where the antenna is one leg. No current will
flow past the bridge when the antenna leg is 50 OHMs. This 'dips' the
My modifications include:
1) building in my own homebrew 5 digit frequency counter instead
of the one designed on
2) including a 10 mA meter to watch the needle dip along with the LED
From the Hendricks QRP KITS WEBSITE:
tuning range: ~3 MHz to ~30 MHz in two ranges
Four digit digital display with
display shift down to 100Hz
Eliminates the need for a
transmitter and SWR bridge when:
Trimming length of resonate
dipole, and portable vertical antennas
QRM free adjusting of antenna
tuners and antennas
Quickly adjust short, portable
vertical antennas, eg. PAC-12 &
Screwdriver antennas, etc.
Current draw is approximately 50mA
My Completed Dipper
A) The schematic and
boards were layed out using EAGLE CAD
patterns were then laser printed onto acetate.
B) The PCB patterns on the acetate
were heat transfered to the copper boards,
boards were then etched with ferric
C) The same acetate / heat process transfers the silkscreen to the top
of the boards after drilling
D) The led / meter cutouts on
the metal case were done with a homebrew
CNC milling machine.
another story, for another page, for another day.....)