AF - CQ Zone 33

ITU Zone 37











QSOs with 3V8SF Station on Topband

You may notice that I sometimes repeatedly ask for callsign or report and this is for me to assess reception difference between RX antennas and TX antenna.



Building a 4 Square Receiving Antenna


After trying Beverages and BOGs, I wanted to build a receiving antenna with relatively limited real estate requirement while ensuring 4 directions coverage. The 4 Square seemed to be a good alternative.

4 Square Receiving at 3V8SF

I did my own design on 4NEC2 of the targeted 4 Square Array which was based on W8JI elements. The elements spacing is 21m.

Array Elements arrangement

Each elements is made up using a 6.5m fishing rod and four 8m long top hat loading. Two on-the-ground 20m radials are attached to each element.

Expected array pattern

A lot of effort was made to bring each element to resonate at 1830kHz targeting 75 Ohms +/- j8 using a coil and a set of resistors. This was unfortunately not achieved yet and I stayed within +/- 5 Ohms from the required 75 Ohms.

SWR measurement on the 4 elements

Electrical quarter wave feedlines were thoroughly VNA measured and used for each element.

Delay lines for the cross-fire arrangement were cut as follows; 30 deg for the side elements and 60 deg for the rear element. The front element had 0 deg phase shift.

Using a signal source placed at 2 WL from the center of the array, I managed to measure the F/B of this array to be 21 db and and F/S of 19 db (North direction). Although the targeted performance goes beyond that, more effort is to be made to make the elements matching very close to 75 Ohms.

Front/Back Signal Comparision

Photos of the array can be found here.

Thanks to Ahmad 3V1B and Majdi 3V1M for helping in the set up of the elements. Also to K7TJR, W3LPL and W0FLS for the valuable technical support.


Update: On the air F/B Testing (Switching manually, takes 3 seconds)

(K1KI) Beaming East then changes to West at 00:18, K1KI is at 45 deg from the East position of the 4SQ

(F5IN) Beaming North, South at 00:22, North at 00:57, South at 01:13


Measuring Ground conductivity at 3V8SF


In order to better assess antenna performance, ground conductivity measurement had to be conducted. To do so, two 1m steel probes were pushed in parallel into soil. An antenna analyzer measured the complex impedance which was found to be 56.5+j17. I have used DL1GLH's calculation on his website to convert that to conductivity which is found to be 21.7 mS/m. Of course this is not very representative of all the soil around the antenna neither the entire earth depth but should give some indication.

Radiation patters: Blue for City QTH, Red for current 3V8SF QTH

I here above compare antenna radiation pattern of my TX antenna between city location and current 3V8SF location. The take-off angle goes from 35 down to 19.9 deg.


160m Top-loaded Vertical in 3V8SF


Preparing for the new season, I designed and built a top loaded vertical antenna for 160m in 3V8SF location. The antenna is 17m high with two top loading wires 12m each. For instance, the antenna has 8 radials, 19m each. A shunt match coil is added at feedpoint.

First testing night QSOs - 21/09/2018

First measurements showed that the wire interacts with the metallic hanging mast so I had to put it 1.5m away then adjust the hairpin match again.

The map above shows the stations I could QSO during the night of September 21st. The antenna performed really well with 100W only. Unfortunately, the beverage antenna was disconnected.

3V8SF as RXed by VY2ZM 00:43z

3V8SF QSO with FR4NT 01:32z


260m Beverage Antenna beaming North America

May 2018

I installed this beverage for experimental purposes. It was used in Spring Stew Perry DX Challenge to check the performance listening to NA station (antenna beaming). The location is approximately 100km away from 3V8SS where the TX Inv-V antenna is.

Transformer Box

26 Ground spikes were prepared in advance. 1m long PVC pipes were hooked up on the spikes partially buried. Due to some constraints, the beverage length was limited to 240m beaming North America (at 291 deg). One ground rod (1m long) is installed at each antenna end. The receiver end has 2 radials (15m).

Beverage Antenna Radiation Pattern (MMANA)

The antenna was connected to Reverse Beacon Network (3V/KF5EYY). After 5 days of receiving, data was gathered for 160m. Calculation were made on Excel to turn raw data into station locations. The map below shows the received stations. The circle size indicates the average signal strength from the region. The signals from North America were good compared to those of much closer European stations!

During the Spring Stew Perry, I was operating from 3V8SS using an Inv-V for 160 while listening on the remote beverage. European signals where clearly better on the inv-V while no NA signal was heard on it. NA signals were easily copied on the beverage.

Here below are two audio recordings of NA stations:



Later on, the ground spikes were replaced by 2m long steel tubes set up on small cement blocks.

The SWR curve of the beverage is plotted using Rig Expert AA-30.ZERO and was found as below:

Signal Source and F/B Check

I used a signal source of about 0,5W at 1834.4 KHz to check the front to back of the beverage antenna.

The distance from both ends of the antenna is about 470m on the same line.

The signal source was powered by two 9V batteries and the antenna consisted of a 2m wire.

When plotting the radiation pattern of the antenna on MMANA at an elevation of 0.18 deg (corresponding to 470m distance and 1.5m of elevation), the difference of Front to Back was found to be around 8 db (See pattern plot at right).

SpectraVue has been used to record the FFT Spectrum from RF Space SDR-IQ during the signal source transmission for a later comparison of signal strength at the TX frequency.

According to the plots above, a difference of 7 db between front to back can be noticed which is in line with the plotted pattern at 0.18 degree (Blue line: Front Signal, Red Line: Back Signal).

In order to check the maximum null, signal source should be placed much higher in the air.


Name: Ashraf CHAABANE "Ash"

Date of birth: 19/12/1983

Nationality: Tunisian

Origin: Kerkennah Isl. AF-073

Job: Process Engineer


WRTC2014 Competitor


E-Mail: ash.kf5eyy@gmail.com



3V8SF Radio Club


Call: 3V8SF
Location: Sfax, Tunisia
Locator: JM54ir
 - 17m Vertical 160m

 - 260m Beverage

 - 4SQ Receiving Array

QSL Manager: LX1NO

LotW: OK




3V8SS Radio Club


Call: 3V8SS
Location: Sousse City, Tunisia
Address: Maison de Scout Avenue Abou Jihed 4011 Hammam Sousse
Locator: JM55hu
LONG: 10.5941 E
35.85662 N Google map


 - CT-37HF for 20/15/10m

 - Spiderbeam for 20m~10m
 - Vertical 40m GP
 - Vertical 80m/160m GP
QSL Manager: LX1NO

LotW: OK




3V8BB Radio Club


Call: 3V8BB (Inactive)
Location: Bir El Bay, Tunisia
Address: ISAJC POBox 2055

Bir El Bay, Tunis, Tunisia
Locator: JM65er


Antennas: View

 -160: Inverted-V

 - 80: Vertical

 - 40: 3 Elements @ 20m

 - 20: 4 Elements @ 20m

 - 15: 4 Elements @ 20m

 - 10: 4 Elements @ 20m

 - PRO-67

QSL Manager: LX1NO

Direct Received QSLs: here

LotW: OK



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