February 2022 - Part of the experiment with receiving antennas on low bands, myself and Ahmed 3V1B built a couple of PA0RDT Mini Whip antennas for a later possible use as a receiving array..

The active antenna was powered via biasT. A pipe enclosure contained the circuit for outdoors installation.

More information on the MiniWhip design can be found here.

The tests that were carried out used the MiniWhip powered by 9V Battery through the BiasT. The feed voltage passes through 20m of RG-174 coax and reaches the antenna at about 7.5V.

A ground connection has been connected to the coax shield at receiver end.

Mounting of the antenna was at about 4m high.

I also used an MLA30+ powered via USB and beaming north (where most of the signals are coming from!). Almost the same height as for the MiniWhip.

The comparison waterfall screenshots can be found below with the MLA waterfall being the upper and the MiniWhip's one being the lower.

Back in July 2020, the YASME Foundation has allocated funds for a project to expand the Reverse Beacon Network nodes.

These new nodes are being added in regions where there is a need for reception reports to support amateur radio operation and where those reports will also have scientific value for geophysical research.

I did receive Tunisia's RedPitaya card that could be easily turned into an SDR. Redpitaya allows for 8 bands decoding simultaneouly - per receiver! It can operate two receivers in the same time!

A copy of Skimmer Server is needed to perform CW decoding on various bands at a time. There is a possibility to run two of them, one for each receiver.

The RedPitaya uploads huge amounts of digital data to the Skimmer PC (130 Mbps upload speed for typical for 15 -band 192 kHz skimming). A Gigabyte switch is needed.

One antenna port can be used for both receivers. I'm segregating them to be able to line up two antennas (for Low and High bands).

This design of the SO2R is an improvement to KF5EYY SO2R v2 (See below). The audio switching part now includes 1:1 transformers mounted on the PCB. Two new PCBs were added to control a 6x2 Antenna Switching system via OTRSP (Wintest, DXLog or any logging software that supports this protocol).

PCBs 3D design on Proteus

The PCBs are designed to be stacked on an Arduino Mega controller.

A 6x2 LCD is used to show the band of each transceiver and the status of the headset (Left and Right ears).

The design is based on Relays control. The schematics are provided here. Please note that only relays for the control of Radio 1 Antennas are shown. Similar relays set up should be considered for Radio 2. Different relays (G5V-2 and G5Q-1A) were used in PCBs 1 and 2 due to unavailability of components in local market. Simple contact relays (G5Q-1A) can be used for both.

OTRSP is used to control audio in the headset and to 'read' each radio band to switch the 6x2 to the appropriate antenna. OTRSP Properties (in Wintest) have to be configured for each band (AUX11, AUX12, etc.). It is recommended to use a port monitoring software (ie. Device Monitoring Studio) to make sure the device received the right command from the logging software.

In 3V8SS Station, all antennas have to be squeezed on the roof area. The station is equipped with a 7 Element CT-37HF Yagi for high bands installed at 7m high from the roof. Not far from it (around 8m away) a 5 bands Spider beam is installed at lower height. For low bands, the station is equipped with an inverted-V for 80 and a Ground Plane wire vertical for 40m.

With the sun entering low sunspot cycle, I was thinking how to improve my QSO count on low bands and more specifically on 40m. Being close to Europe is a big advantage.

Back in 2009, the 3V3S team from Germany have installed an 18m vertical for 80/160 using Spiderbeam poles. This fiberglass vertical was broken two times.

Fortunately, a 12m length of it is kept unharmed. I decided then to use it as a second element to the original 40m band - 12m length vertical antenna. I started reading in antenna books and websites about the best configuration. I then decided to make phased verticals using Christman method.

I shared the ideas with Ahmed 3V8CB and Ali 3V/F4HJD, both active members of ARAT. They were more than happy to come and give it a try.

Our objective was to have some gain towards Europe (at 0 deg Az) and NA/AS (respectively at 350 and 20 deg Az). Africa is behind us so there was no need to consider a direction switching relay.

Phased Verticals Schematics

We decided to move a little bit the original vertical and get some distance from the Yagi tower and Spiderbeam. Then we started making use of the old 80/160 poles as a second vertical. Both wire verticals were having two radials. Once up, we started cutting wire length till an SWR of 1.5:1 is obtained. Both verticals are electrically similar. We were a bit concerned about the electrical impact of the 5m mast holding up the new vertical.

I used VA7ST Christman Phasing calculator to calculate feedline lengths for an operating frequency of 7.050 MHz. A velocity factor of 0.66 was used for RG58 (50 Ohms). Both antennas were fed by 84-degree feedlines (about 6.5m) with additional 72-degree (about 5.5m) to the northern vertical (the front element). We didn’t have an antenna analyser to further adjust lengths, all had to be fixed by experimentation.

Phased Verticals installed at 3V8SS

The triple point (where both feedlines are connected to the main coax) was mechanically attached. Myself, Ali and Ahmed made RX and TX experiments by lining up one element then two elements and check the performance. We checked as well the F/B Ratio by manually switching the feedlines between the two verticals.

The SWR of the system was very acceptable (1.5:1 on almost the entire 40 band). Here below are audio recordings of how RX and TX were improved by the new system:

TX Audio recording: my signal as recorded by ARDAM WebSDR located in Andorra which uses a half wave dipole for 40m: 2016-05-08 10:14Z 7030.0kHz

The first 55 seconds is using the phased vertical. At 2:40, I used a single vertical (old configuration). The difference is clear!

RX Audio Recording: IK5OJB on 40m:

0 to 34s: use of phased verticals beaming EU

35s to 58s: use of single vertical

59s to end: use if phased vertical beaming south

Given the unavailability of ham radio equipment in Tunisia, I have decided to build my own SO2R Controller that should help me in the upcoming 2016 contest season.

I made a deep search on the net and found several designs; some are transistor based with front panel control switches and some are micro-controller based.

Arduino Uno mounted on KF5EYY SO2R board

I was very interested in K1XM Arduino based design. I bought an Arduino Uno device and started familiarizing with it. I was impressed with the ideas we can realize with it.

K1XM design (and code) appeared complex to me and uses features that I don't need, I inspired from it to make my own design and programming of the micro-controller ship. I have used "Serial Port Monitor" software to better understand how Wintest uses OTRSP (Open Two Radio Switching Protocol) to communicate with the device and update the program accordingly.

KF5EYY SO2R Controller

Few testing of Relays command on a breadboard were conclusive, so I purchased components and built the design on a perforated board.

The device is USB powered and enables audio control in the headphones (Radio 1 only, Radio 2 only, Radio 1 Left/Radio 2 Right, Radio 1 + Radio 2 on both ears with possibility to adjust audio level of Radio 2 for band opening monitoring).

The device enables also switching TX between the two radios. Dual CQ and other customized operating scenarios are possible through Wintest.

Relays and Status LEDs

Video of device testing in 3V8SS club station can be seen here.

KF5EYY SO2R 1.0 Schematics

I have then decided to replace the LEDs by an LCD and get the components implemented on a Printed Circuit Board.

I started testing the LCD on a breadboard. Be careful to the contrast adjust (pin 3) which should have a resistor connected to the ground. Direct connection is the silly mistake I made costing me 4 hours of investigating why the LCD does not show any message!

Further improvements have been brought to the schematics (thanks I4UFH). These include adding optocouplers to the CW connections to the radios. I also added capacitors for RF grounding on the audio outlet.

I made the PCB design using Proteus ARES 8. A lot of manual work was done to put the LCD on one side and the connection wires on the other side.

KF5EYY SO2R 2.0 PCB

The Arduino code was improved to inform user Wintest is properly connected to the device. This is shown by a flashing [WT].

Map it! is a tool that enables users to plot ADIF files (generated by Logger32) on a rectangular map with great circle lines display. It also provides information on the plotted stations such us distance, bearing and the bands in which the DXCC/location is worked. In this version 1.0, ADIF files shall have either Lon/Lat coordinates or GridSquare (Maiden).

The tool also enables the plotting of FT8 Log file (generated by WSJT-X). The purposes can be to compare performance of RX antennas since the tool displays the RXed Grids with S/N Ratio color coding (highest S/N for each grid).

Map it! is a joint effort between myself and Mohamed 7X3TL in an endeavor to make a good use of our spare lockdown time.

Depending on feedback from people, we are planning to embed more features.

Map it! can be downloaded here.

At first glance it is clear that 3V8BB QTH is excellent and these mountains only affect SA path. However, I wanted to do the exercise, come up with charts that support this, and why not, look for improvements.

Thanks to N6BV and VA7ST for their support during the elaboration of this work and to S56A, W1UE and K6TU for their comments and ideas

You can download the study here.