Fox Delta is a group of people formed a few years ago by Dinesh VU2FD. It deals with the development of kits for amateur radio needs. The entire documentation is available on the website so everyone can be inspired or build a kit from their own parts. The prices are really affordable, the selection is interesting, and those who are not quite skilled in assembling kits can order a finished product for an additional fee.
LCD SWR Meter with PIC16F877A
One of the kits offered is also dual-channel LCD SWR Meter with PIC16F877A. They are the authors of the project Antonio I2TZK, Frank K7SFN, and Dinesh VU2FD. Allows measurement of power, reflected power and PSV in the range determined by the sensor (HF/144MHz, 1-100W, 10-2000W). The measured data is displayed on a two-line LCD display or on a computer connected via a serial port (SWM3 version via USB).
I ordered and paid for the kit over the internet, and in about a week, I already had the package at home. The price was approx. 83EUR: SWM2 + Dual scale bridge sensor + shipping. And it could be assembled...
First impressions of the SWM2 kit
The first impression of the kit is greatly affected by the mechanical design of the boxes. The sensor box has gaps along the edges of the cover, as well as the connectors, and the main box has relatively large holes for LEDs, buttons and connectors. Even white color suits kitchen appliances more than radio amateur equipment. I solved this with black spray and rubber grommets and the result looks better. The sensor can be placed out of sight or you can make your own box.
The dual-range KV sensor best suited my requirements. It is a classic PSV bridge with toroid and range-switched relays. Linearization is achieved by introducing diode bias. In principle, any design of a measuring sensor can be used.
Mounting the PCB is relatively simpleThe PCB pads are large enough, making soldering easy. The most laborious task is winding the toroid. However, the documentation lacks information about the number of windings! By examining sensor photos, I estimated the number of windings to be 25, which is a fairly realistic number. A piece of thin Teflon coaxial cable passes through the toroid. Although the manufacturer declares a range of up to 2kW, I am not sure if this is realistic.
Assembling the main PCB is also simple. Just follow the proven assembly procedure - from the smallest components to the largest, finally installing transistors and IO. Two smaller boards - display and control + LED - are connected to the main PCB via flat connecting cables with connectors.
The most interesting moment in devices assembled by hand is the first power-up. SWM2 started up, the display lit up after connecting the power supply. Adjusting the contrast on the main PCB with a trimmer was enough to prepare SWM2 for calibration. Calibration is described in the documentation and is similar to a standard PSV meter.
Screen remote station including power measurement and PSV software I2TZK
Connecting SWR Meter with PIC16F877A to PC
An interesting feature is the connection to a PCThis allows logging of measured data for further processing and, of course, displaying currently measured data on virtual measuring instruments (needle, dual-needle, or digital bargraph). You can watch a sample video at www.youtube.com
This function can also be used for a remote station, where the serial port is "extended" via LAN or the internet.
Calibration
Calibration is described in the document available on the FoxDelta website. There seem to be quite a few steps, but the setup is quick and takes only a few minutes. I did not verify the measurement accuracy, but it is likely determined mainly by the sensor (frequency dependency). When compared to the wattmeter built into the transceiver, I did not notice any deviation on any band.
Summary
The LCD SWR Meter FoxDelta is a useful addition to a ham shack for radio amateurs and, if one overlooks the construction, it offers features of meters that are several times more expensive. Even a not very technically skilled HAM can handle assembly from a kit.