Emtech NW20 (formerly known as the NW8020) is a 20 meter CW transceiver
designed by the late Roy Gregson, W6EMT. The NW series of single band
transceivers were available for 80, 40 , 30 and 20 meters. Emtech
is still being operated by Roy's son, Scott KC7MAS, however it is
unclear if more NW transceiver kits are planned,
NW series transceivers use a single conversion receiver employing NE602 mixer and MC1350 IF amplifier chips. The IF frequency used by the 20 meter version is 9.6 MHz. The NW rigs are one of the few kits that use a conventional variable capacitor for the VFO tuning control. The tuning capacitor has a 4:1 reduction drive on the control shaft and a mechanical pointer with an analog dial scale is used for the frequency readout. The tuning range of the NW20 is 14.000 to 14.096 MHz. Emtech provides a dial calibration decal with the kit and the frequency readout accuracy is within about 2 KHz which is actually pretty good for a pre-calibrated mechanical tuning system.
One of the nice features of the NW series receivers is a variable bandwidth IF crystal filter circuit. A front panel control allows the operator to narrow the receiver bandwidth to about 200 Hz to effectively reduce QRM from adjacent stations. Also, an optional audio filter is available to really tighten up the receiver bandpass to make the NW receiver one of the best of the low cost QRP kits. The receiver audio output is sufficient to drive an external speaker.
The NW's transmitter is capable of producing 5 watts of output. An internal drive control can be adjusted to reduce the output if desired. There is not an internal electronic keyer. Keying is crisp and clean and the QSK circuit works very well. The sidetone is actually the transmitted signal as heard by the receiver. An internal control is used to set the sidetone level.
NW transceivers were available as board kits where the builder provides the case or an optional pre-drilled steel case was available from Emtech. The Emtech case used a SO239 antenna connector and has both speaker and headphone jacks.
The NW20 board shown to the left is installed in the custom Emtech cabinet. The main circuit board is not crowded and uses standard through hole components. The optional audio filter is on the the small circuit board mounted above the main board.
The cabinet kit includes the connectors, knobs and other small parts needed to finish and dress up the project. The enclosure has lots of spare room for future modifications, however the case configuration makes it difficult to work on the bottom of the board without disassembling most of the connectors and controls.
Emtech was perhaps one of the few QRP kit manufacturers that use a variable capacitor for the main tuning control. Follow the kit instructions carefully when installing the tuning capacitor and dial calibration decal to ensure dial calibration accuracy.
You can use a few tie wraps to bundle the off-board wiring into neat cables.
The instructions are pretty good, although this is a more complex kit than most single banders and a bit of prior building experience is helpful.
The NW20 in the photograph was kitted by W6EMT in 1996 and has a revision F circuit board and is shown in the Emtech case. I believe that revision G boards may have been the last version used in production kits. I am not aware of all of the board differences except for a revised transmitter chain layout on the newer boards. There is not a reverse polarity protection diode on the kit that I built and it would be wise to add one to the 12 Volt DC input circuit during construction.
Emtech NW Series Links: