Sunday, September 27, 2020

HFB01 Portable HF Antenna

Doing a short review and blog of my "Super Antenna MP1" clone from China with model name of HFB01. This antenna support from 3.5Mhz to 440Mhz, a really wide frequency range.




For the installation, I made a L shape water pipes mounted to the balcony grill. The base of the antenna is clamp using U clamps. with this setup, it is easier to adjust the angle and easier for me to adjust the variable inductor easily.

Once eveything seems secured to the grill, I started to tune the antenna for 40m, 7.070Mhz by adjusting the variable antenna up and down and looking at the SWR of the MR100 Antenna Analyzer. This step was really easy compared to my previos JPC9 antenna by adjusting the length of the telescopic antenna.



Once I m satisfied with the antenna tuning, I fire up FT8 to do some receive and transmit tests. 

FT8 Transmit Tests : I can only transmit to Japan and east coast of US but could not transmit to Europe side.

FT8 Receive Tests : I can only receive from nearby South East Asia and Japan only.

FT8 Rx & Tx

FT8 Rx

Overall, I am quite safisfied with this antenna with it easy to tuning and very light weight.

Saturday, December 8, 2018


SVT MMDVM first calls

The Digital Voice ( DV ) for the ham radio have started a few years ago but to build a hotspot ( a tiny personal half duplex repeater ), you will need some pricey equipments like DVStick with AMBE-3000 vocoder and USB interface plugged into a Raspberry Pi with an Arduino Mega to drive the UHF transceiver. 

It all started around Sept 2017 when the price of DMR radio was getting below RM1,000 and a few of us purchased a TYT MD-2017, one of the more popular DMR radio at that time.

Secondly, without a DV hotspot, having a DMR radio is kinda useless unless you are within the range of a DMR repeater in your area.


Thanks to Jonathan Naylor G4KLX ( ) (and many many people people) that created the MMDVM, a software that integrated multiple hardware ( teensy, Arduino DUE, STM32F1, STM32F4 ) and Raspberry Pi running pi-star ( ).

When I saw the hardware requirements, I noticed that I actually have ALL the hardware with me, STM32F103 red-pill, Raspberry Pi and they were also using a version of Arduino called stm32duino

A few STM32 red-pill I purchased previously

The only missing piece was the UHF transceiver called RF7021SE module plus changing the TXCO to 14.7456Mhz. So I started doing my research on different board designs and immediately design a single board layer to test out my design.

MMDVM boards

MMDVM boards

Here is the first version after many iterations and because it was a single layer board, I had to place the SMD LED at the bottom of the board.



Once my designed was almost finalised, I bring it to Uncle Chow ( 9M2CF ) to convert my PCB design to a single layer PCB.

SVT MMDVM negative

SVT MMDVM etched

SVT MMDVM copper removed

After some UV exposure and chemical baths, I got the SVT MMDVM board ready to be soldered.

SVT MMDVM fully soldered

SVT MMDVM top side with red-pill

SVT MMDVM running

Fully connected to the RPI 1 and pi-star software loaded.

SVT MMDVM connected to RPI 1

Saturday, May 27, 2017

Measuring capacitance of variable capacitor (varicap)

This is just a short post of measuring the capacitance of the variable capacitor at maximum capacitance.. 

The first picture is the measurement taken at both the stators ( stationary plates), this is used for magnetic loop as per the diagram below.

Capacitance at both stators

Position of variable capacitor

The below picture measure the capacitance between the stator (stationary plates) rotor ( moving plates).

Wednesday, May 3, 2017

Variable Capacitor for ham radio

A short posting with pictures of variable capacitors made using a CNC machine by 9W2CEW. The CNC cut both the rotor (moving plates) and stator (stationary plates) in one go. Refer to the last picture below.

This design is usually found in loop antenna to change the capacitance value from the shaft.

Side view

Variable caps with laser cut cover

0.7 mm aluminium plates

Sunday, April 16, 2017

40m vertical balcony antenna using PAC-12 , adjustable coil and telescopic whip

Just want to share an updates on balcony antenna using the following setup :-

PAC-12, coil and whip antenna with mounting
PAC-12, coil and 5.6m telescopic whip

Adjustable coil
Equipments :-
Antenna Base : PAC-12
Coil : Adjustable coil ( max inductance is 23uH )
Antenna : 2.5m or 5.6m telescopic whip at 2.29m length
Frequency : 7.080Mhz ( near JT65 freq  )

Telescopic whip ( either 2.5m or 5.6m length) at 7 1/2 feet ( 2.29m ) and the adjustable coil at 21.31uH.

This is the reading of the antenna analyzer at JT65 frequency, complex impedance of  25 + j0, SWR of 1.26:1, therefore I do not need to use any antenna matching tuner. When I transmit at 25W, the meter reads an output power of 20-22W going out to the antenna.

The antenna analyzer is a version of SARK100 called MR100. The details at summary links below.

MR100 showing the SWR
LC100A LC meter to measure the inductance.

LC meter show the coil henry readings

The below is the result of the short 40m balcony antenna, I am able to reach both Europe and USA using it.. In my condo, I am almost surrounded with highrise buildings and not much openings.


Summary Links :-

Sunday, February 26, 2017

SVTrackR with new PCBs and case for the LCD

LCD mounted on windscreen

MicroModem & SVTrackR 


Modem PCB

Making of the acrylic casing ...

Acrylic cover for LCD

Front and back cover
Red acrylic lasercut

Red acrylic parts

Installed acrylic