Ham Radio

Auckland, New Zealand

My new antenna control box







 The is my lastest project. It is a HF antenna tuner with a power and SWR meter, also five radio inputs. Their are four radio in puts on the back and one on the front for easy access. This is my design but the ATU is a MFJ-941D tuner. Their is also a dummy load and a low pass filter. All this was designed to reduce cables and patch leads.

The radio input stage is power from either an installed 12V recargeable battery or external 12V supply, which the external supply charges the internal battery and is switchable from the front panel. All the radio inputs are passed through the low pass filter.

The ATU section from MFJ now selects the dummy load via the coax direct position and has been relabled on the front panel. It still has the balanced transformer for long or open wire feed lines. All the ATU's antenna outputs are now shorted to earth via relays when this unit is switched off. The five radio input's are all earths and remains earthed untill the port that is been used is selected and the remaining four ports remain earthed.

9 Way 12V Distribution box with LED bar graph volt meter



This is a nine way 12 volt distribution box with a very simple bar graph volt meter. The bar graph volt meter can be made with a LM3914 chip but I went through my junk box and came up with this simple design. If you decide to build this design, you will need a veriable power supply to calibrate it. you may find a higher voltage LED will light before a lower LED so you will have to play around with different zener diodes. To made a certain LED light you will have to make the zener aprox. 1.5 - 2 volts less (eg: 11V LED to light you will need somewhere around a 9 volt zener) you can make-up certain voltages by having more than one zener diode in series. Depends on when the LED and the zener will conduct some playing around is needed. An LED will conduct around 1.2 - 2 volts aprox. so when a 12 volt zener conduct (maybe 11.5 - 12.5 volts aprox.) you will still have to wait for the voltage through the zener to raise another 1.2 - 2 volts. So that is why the zener should be aprox 1.2 - 2 volts lower than the voltage you want the LED to light at.

 The distribution box was built because I had too many wires hooked to the main battery. Now I can run low current devices like my "Antenna Safety Switch" and my "Timewave noise canneller" etc

This circuit is the Kenwood IF-232 interface which I use to control my Kenwood     TS-850SAT.

Most of these circuit I build show using a MAX 232 chip. I used a MAX 202 chip. Using the MAX 202 chip, change the 4 x 10uF caps connected between pins: 1 to 3, 4 to 5, 6 to ground and 2 to +5V, change to 0.1uF caps.

I find it's easier to put 0.1uF caps around the chip than using 10uF caps. You can even solder to the under side of the board without making a mess.

Note! You can NOT use 10uF with the 202 and NOT 0.1uF with the 232 chip. 



This is my home brew CAT interface for my FT-990. I have had so much problems to get this interface working. After searching the net for the solution, it seems alot of people have had the same problems with the FT-990 and to all there help other have suggested it seems all was lost.

I spent 3 nights trying to nut it out and came up with the solution. I am using a standard 232 interface chip. It's a MAX202 (the same as the MAX232) but different caps.

You may wish to leave out the 4N35 coupler. This device keys the PTT line. You may only wont this interface for receive only. 

This interface works on my FT-990 which has the latest version 1.30 ROM. You may have problems with version 1.20 ROM.

To find out what ROM you have... turn the FT-990 off and hold down the 1 & 3 keys on the keypad, while holding those keys turn on the FT-990 and let go of the keys and watch the display go through it's check mode and at the end it will spell out YAESU. To the right will show either 1.30 or 1.20, wait a few second... the FT-990 will return back to receive mode. 

The KEY to getting the interface going is to put a 10k resistor from pin 10 of the MAX202 to ground to hold the input signal down a little. IT WOKRS GREAT!!!

Should also work with the FT-1000D, FT-840.

3 way electric antenna switch



  I designed this unit to get away from heavy clunky switches. All antenna positions are held in electrically via relays. To switch on this unit, just press one of the antenna switches, and when another antenna position is selected the first antenna selected will drop out. This unit is switched off by pushing the red button or if the power is lost. The antenna's that are not being used are automaticlly earth, and when the unit is switched off all antenna's are earthed. There is a dummy load button which will select the dummy load or earthing the transceiver when the unit is turned off or power is lost. So if you wish to load up your rig with a dummy load, just select the dummy load position which is indicated by a red LED and then turn the unit off.

The Dummy load position is selected by a latching type relay which will hold it's position even when the power is lost. The black button controls the latching relay even if the unit is switched off but the power is still connected. The red LED will still be lit when the power is off and a higher value resistor is placed in series with the LED so it will only draw 270uA in the off position, the red LED can still be seen glowing.

For protection there is an amber LED which will glow if the power is reversed and nothing will be damaged. Also there is a bi-metal auto resetting fuse inside for extra protection.

This unit works great up to six meters at 130 Watts.

I have been designing this unit over a year with many proto type.

I built This ciruit to progamme my Kenwood TM-G707A


This interface has reverse protection with a LED which will light if power is reversed and the circuit in not damaged. The reverse protection circuit is not shown in the photo but shows is in my up dated circuit diagram

YAESU / ICOM / ALINCO programming interface.

 I built this curcuit to program my Yaesu VX7R. By connecting the TX/RX to the sleeve of a 2.5mm stereo plug and the ground to the body of the plug, I am using the Yaesu CT-91 microphone adaptor, in which I simply plug the 2.5mm plug into the 2.5mm socket of the adaptor... It works perfectly.

I also noticed that my Alinco DJ-X2000 scanner has a 2.5mm programming socket with the same connections. It works on my Alinco perfectly as well. I have also noticed that Alinco and Icom programming leads are compatible.

This circuit WILL work with most Yaesu's, Icom's and Alinco's just by changing the plug to suit your radio.

Radio's that I have programmed myself with this circuit are: Yaesu VX1, VX2, VX5, VX7, FT7800, FT8900, FT857, Alinco DJ-X2000.

This circuit will NOT work with Kenwood because they use a separate RX and TX line. 

I built this ICOM interface to control my IC-729

 Parts used:

1 x 220 ohm resistor, 5 x 0.1uF, 1 x 10uF caps, 2 x 1N4148 diodes, 1 x 4V7 zener diode, 1 x MAX202 ic


A simple 10W QRP Z-match antenna tuner, good for 80 through to 6 meters

I have been trying to locate an Amidon T-130-2 toroid to build this circuit. The toroid I was looking for is red coloured, but unable to find one; I found a smaller red toroid that works perfectly. The tuning capacitor's measured at 330pF per side. 

Home built AM/CW 4 Watt transmitter



 The two photos below shows the trtansmitter updated with  a built-in ATU and a SWR meter



This is my home brew AM 80 meter phone and CW transmitter. Using a single EL84 for the output at around 4 Watts. The large transformer in the centre, is a HT power transformer which I use as the modulation transformer.


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