Portable 3 EL 70cm Band Yagi

Hello. I want to share one of my recent projects – 3 el yagi for 70 cm band. It’s very light, portable and great for backpacking or hiking.
I like hiking a lot so to have the necessary equipment is important. For HF bands I have IC-703+ and set of J-pole antennas.
Many HAMs use a small handled VHF/UHF radios but unfortunately the original antenna is very bad and not efficient. It cause bad communication or radio overheating.
I decided to make one antenna that I can handle and have with me every time when I hiking or backpacking.
The antenna should be:

  • – light
  • – small or foldable
  • – have a good performance

Finally I found a solution and made this antenna. It met all my criteria. I got a ultralight, foldable and portable pocket size antenna with decent performance.

Frequency: 436.00 – 445 MHz with SWR 1:1.5 – 1:1:1.5 and 1:1.1 on 440 MHz.

Gain: 7 dBd 

Weight : less than 12 oz

I used a material that had in my garage, there is nothing special or expensive. The boom is a simple fishing rod that I bought  on eBay for HF projects. The antenna elements made
from 1/8″ (3.18 mm) brass rod. You can find them from K&S Engineering store. Simply drill a two holes, one for reflector another for director. The driven element can be just zip tied to the boom.
The important step is tuning. At least you have find a position of driver element whenever you get a lowest SWR on central frequency (the antenna can be tuned ether for SSB or FM). Personally I use this particular antenna only for FM, repeaters and satellites. As you can see on photo, I’d attached my cheap chinese radio directly to the boom.




Download in high resolution here in PDF.

Simple Bluetooth CAT Interface, RX/TX App Android

Hello everyone. Want to share another project for who like spend time with smelling flux and solder. The project is – Simple CAT Interface.
I guess everyone knows what it CAT for, no isn’t CAT or DOG. Most of us have the cable CAT interface which we use to control our rig from computer. The standard cable is a simple converter from one level to another ans usually based on MAX232 IC. But how about make it cordless? Let say it in other words – make it wireless or Bluetooth device. Sounds good, doesn’t?
This project is not new or something breathtaking and have been successfully done many times. So you can find a lot of information online, just Google It!
What I want to share is just How You Can Do It By Yourself in simple way. Make it for yourself or ether better make it for your Dad or Mom as a present. That would be a great present ever.
Just remember one thing that you will not find something like this on the market so it would be awesome gift. Let’s start.


HC-05 Module 100% Compatible with: YAESU FT-857/D, FT-817/ND, FT-897, FT-100D 

Available with custom settings (baud speed up to 38400 bps, name, password and etc)

The new version of HC-05 which I have in my store on eBay compatible with Android OS and RX/TX App by YO3GGX. Guaranteed 100%.

It’s very easy to connect and use. It doesn’t required knowledge other than how to connect a regular Bluetooth device.

Just plug my HC-05 module into your TRX and run the application on your phone. Connect via Bluetooth. Done.
– Change Bands
– Tune Frequency
– Change Modes
– Transmit (PTT)blu1blu2

High reliability, quality and strong support.

Just read this:

This Bluetooth CAT interface works GREAT and is EASY to setup! (FT897D)
well assembled component, excellent service
Great! Thank you, work very fine!
A+++++ Quick shipped, good service

How it works?
It works as any other Bluetooth devices in your room. Like a cellphone. Turn On. Pair. Connect. Ready. Sounds simple! Oh yes, trust me you wouldn’t believe how it simple.
Look at the picture. Just want to show an example for FT-857D (have done many CAT adapters for this rig)

What we can use it for?
In same way as you use the standard CAT cable. To control your transceiver (frequency, modes and also PTT). Imagine, no cables, no web on your desk, just rig and computer.
What transceivers are compatible?
Any with CAT connector. Simply you have to use the correct plug for your rig (8 Pin mini DIN for Yaesu, 3.5 mm Stereo CI-V for Icom and etc)
What do you need to make it?
Some components, soldering iron, magnifying glass, tools, wires and patience.
What components do we need?
– Bluetooth Module (HC-05 or similar)
– Voltage Regulator 3.3 V LP2950 (or any with out 3.3 v and in 5-20 V)
– 4 resistors 1 kOhms 1/125 W
– 2 capacitors 0.22 uF, 25V
– Dual Ultralight LED
– Connector which will be plugs to your rig
– Some box or case for module
Where we can buy parts?
Anywhere. Local radio components store (radioshack or etc), online store (digikey, mouser), eBay. The Bluetooth module sells on eBay and average price is $5.
There is not a big difference between modules but I recommend use or HC-05 or HC-80. They were tested by me in my projects. Other parts are not critical.
How the module looks and pin out?

HC-80 Bluetooth Module (difference with HC-05 only with one pin for LED. I will talk about that later)
HC-80 Bluetooth Module
Now let take a look at schematic and module connections:
As you can see there is HC-80 module on the picture. For HC-05 module the LED (Paring) should be connected to PIN 32.

To make it easy I uploaded a datasheets:
download HC-05 (in PDF)
download HC-80 (in PDF)

Also I guess you noticed that I use triple color LED. It’s really up to you and TX indication just an option. Realistically you need only POWER and BLUETOOTH Connection indications.
Basically you need to solder some component on top of the board. I usually solder 3.3v regulator first along with 0.22 uF 0805 size SMD capacitors and then LED on other side of the board.
Be careful when you solder and avoid the overheating. The board as you noticed very small and you have to hold it when solder. 1 kOhms resistors are soldered straight to the pins TX and RX.
Before solder to the connector you have to check the board and all connections. Use a small power supply. Apply 12 v to the input of voltage regulator. Power ON LED should light on and Pairing should blinking. That means everything works as should. Of course you can check the Bluetooth connection. Just follow the steps which you can find below.
When everything is tested and ready to use now time put all together. I don’t know what box or case would you use but I want to show my idea. I used the simple plastic case of 10 Pin DIN plug. The 8 Pin mini DIN slides in to 10 Pin mini DIN plastic cover. Simple, easy and looks neat. Take a look.




Certainly there is no standards and all depends on you and your imagination. Use whatever you have and whatever you like. Just remember some important things:
– It’s a wireless device so the case suppose to be plastic (NON METALLIC)
– No metals around PCB antenna (otherwise it’ll reduce the distance)
All right it looks like you made it and now time to do a final check.
How to Connect it?
Before Use:
Make sure that your laptop or PC has Bluetooth Adapter otherwise it will NOT work.
1) Turn Off transceiver
2) Plug in HC-05 into CAT/Linear Connector
3) Set in transceiver Menu – CAT
4) Search for new Bluetooth devices
5) Click to PAIR (passcode 1234)
6) Make sure that HC-05 is connected to PC
7) Check for assigned COM port (example COM12 or COM9)
If you don’t know how:
Right click on “My Computer” icon -> Click on “Manage” ->Click on “Device Manager” -> Click on “Ports(COM&LPT) -> Verify the assigned to HC-05 COM port.
8) Change COM port in your program (HRD or etc) to that COM Port
9) Check if all work as should.
10) Got a problem with communication or connection feel free to contact me.

Default settings for HC-05 Bluetooth Module (verify it in COM Properties).


The Technical Data:

The Technical Data:


Alex K6VHF

2014 WW WPX CW contest results

Glad to inform that I’ve received a winning award for 2014 WW WPX CW.



Just another award for my collection. Thanks to everyone!



The Portable QRP SWR Meter – “Magic Bridge”

KIT PRICE – $32 with Free Shipping USA only.
ASSEMBLED PCB – $30 with Free Shipping USA only.
BLANK PCB – $12 with Free Shipping USA only.
ASSEMBLED and TESTED – $55.00 with Free Shipping USA only.


UPDATED: 12/21/14


New PCB v 7.0 is arrived. Better Quality, easy to assemble and Lead Free. 100% is safe to use!

New PCB v 7.0 for Magic Bridge

New PCB v 7.0 for Magic Bridge

Hello everyone. I want to introduce the new project from Ivan RA3WDK which is a Portable QRP SWR Meter. We call it a “Magic Bridge” (MB). The MB can measure SWR from 1.0 up to 4.0 and holds 10 Watts. So it’s ideal for the QRP radios like an Elecraft KX-3 or Yaesu FT-817ND. You can take it with you to the camping, hiking or expedition.

It pocked sized and works without any batteries (NO external or internal DC power source) and can be used everywhere and with any QRP transceivers. The MB has a 4 color LED’s and indicates the certain SWR when transceiver is on TX. As you can see on the photo there is the two BNC connectors, one is male (to TRX side) and female (to ANT side).

Portable QRP SWR Meter

The Portable QRP SWR Meter

So, what’re the benefits of this particular SWR meter?
– pocket size
– no batteries required
– LED (good in dark or at night)
– light weight
– you don’t have to be present at the meter to check a SWR

Sounds good, doesn’t? Let’s see what we have inside in that “magic” black box.

The "Magic Bridge" with open lid

The “Magic Bridge” with open lid

As you can see there is only one small PCB with the SMD components and a couple film metal resistors. You’ll be surprised but the board hasn’t special or expensive components. Basically it’s the simple RF bridge and voltage comparator. Let’s take a look the schematic diagram of our “Magic Bridge”.

"Magic Bridge" schematic diagram

“Magic Bridge” schematic diagram

You can download the schematic diagram and part list as a PDF file here.

It’s really easy to assemble and will take just an hour of you time. No tuning required after assembling it’s should work without any issues. I’ll give to you advise how to assemble, test and use. We’re offering to you a kit which is an enclosure, blank PCB board, all components, two BNC connectors with a cable and hardware screws. That’s all that you need.

"Magic Bridge" kit

“Magic Bridge” kit

The price for the basic kit is $29.99. The “Magic Bridge” comes only with BNC connectors and holes are nor drilled. You can use the drilling template.

Assembly Instruction :

PCB board

Click to enlarge

The first, we have to solder all SMD components and then the through hole components.

1 – solder the LM339
2 – resistors 3.9KOhms and 2KOhms
3 – diodes VD2-VD5
4 – resistors 5.1KOhms
5 – resistors 100KOhms and 56KOms
6 – caps C1-C4
7 – caps C5-C6, C8-C11
8 – resistor R14

Now the through hole components. The resistors all through hole resistors should be mounted 1 or 2 mm above the PCB. Don’t forget they will be hot during operation.

9 – zeiner VD6, diode VD1
10 – resistors R1, R4, R6
11 – resistors R3, R6
12 – cap C7
13 – all four LED’s


You also can download the assembly instruction from Howard W1ZKK. Thanks Howard!

Now let’s check all components and soldered points. I recommend to use a NON clean flux but anyway after soldering please clean the board.
Here is some tips about the components.

Some tips.

Some tips.

Check again. This is how the board should look with the all installed components.

The PCB board with the all components

The PCB board with the all components

After that our board is ready to use and now it’s time to get ready the case (enclosure). We have to drill the 4 hole for LED’s and other 2 for the cable and connector.
Please use this template to drill a holes. Diameter of all holes for the LED’s is 3 mm.
Here is a datasheet for the 1591XXM enclosure.

Drilling template

Drilling template

The holes for the RG-58(.195″ or 4.95 mm) and BNC connector depends on your uses and can be not centered. When you finish drilling please verify that all holes are correct and have a right diameter. If they’re fine now the next step is put the board and screw it down.
Now we have to solder a cable with the male BNC connector and single female BNC to the board. Look on photo.

Male BNC to TRX and Female BNC to ANT

Male BNC to TRX and Female BNC to ANT

As you can see for the female BNC I used a short solid wire (20 AWG) between the pin and PCB. Also use a same wire for the ground connection.
Please check again all connections and PCB board with the components as well. Now is time to test our SWR meter.
– HF transceiver
– 50 ohms load or just 2 W 50 Ohms resistor (it’s better to have at least a couple with different values)

The first, set the output power of TRX to 1 or 2 Watts. Connect the SWR meter to the TRX and leave open the ANT input. Select a CW mode and press the key or set to FM mode and press PTT. All LEDs (red, two yellow and green) should light. Perfect. Release the key or PTT. Now hook up the 50 Ohms resistor to the ANT input of the SWR meter and repeat the previews procedure. Should be NO light. This is equivalent to the SWR 1.0. Great, everything is work!!! My congratulations!

If you have a couple more resistors (25, 75, 100, 150, 300 Ohms) and free time you can try to do more experiments to find out the right SWR measurements.
Here is a table, look at it. Questions?

SWR measurements

SWR measurements

Worked fine? Since that our SWR meter is ready to use. If the “MB” didn’t worked don’t give up, we’ll try to find the problem and fix it. Let’s start a troubleshooting.
1 – visual check for shorts, solder bridges or missing components
2 – voltage check

Voltage Diagram

Voltage Diagram
Click to enlarge

Check this out. Here is a voltage diagram. To check the voltage in those points you need to hook up the “MB” to the transceiver, set the output power to 2-5 Wstts and push the PTT (in AM or FM mode on any HF bands), another words we have to transmit the RF signal. Take the multimeter and check a voltage in all points.
That’s it, if there still no voltage, please check the circuit, diodes and LM339 (could be you soldered them backwards). That is the most typical issue. There is no more possible issues. The circuit it’s easy and should work if all components were soldered properly.

Ver 4 current one
– resistors R3,R6 now rated 2W
– capacitor C9 now 1206 size
– capacitor C7 in new position
– capacitor C8 moved to new place
Ver 3 
– needs a jumper or 0 Ohms resistor in the joint point VD2, VD3
– second generation with the one single PCB
Ver 2
– first generation of the MB on two boards

Thanks for you patience!
Don’t forget – DO NOT EXCEED POWER MORE THAN 10 Watts.

Stay in touch!
Our technical support is 24/7.

KIT PRICE IS – $29.99 with free shipping USA only.
International customers please contact me before buying.

You can buy it on eBay in my store.

Alex K6VHF

4 Event Sequencer by US4ICI

The 4 Event Sequencer for transverters and power amplifiers (PA) is designed by US4ICI.
You can buy it in my Online Store or on eBay.

This 4 event sequencer has four outputs which able to sink up to 100 v at 7 amps and another output up to 30 v at about 10 amps for LNAs. Each output is protected from transient spike. The delay is adjustable (R4 on the board) from the few milliseconds to seconds. The board has the LED’s allow a visual indication of timing for each port (event).The sequencer use a ground for PTT activation and simply can be activated from any transceivers or transverters. Each board is tested and ready to use. You just need to adjust the desired delay.

  • Technical characteristics:
    – Board Material: FR4
    – Output: 7 A (max)
    – DC voltage: 12 – 30 V
    – Dimensions: 65 mm x50 mm
    – Assembled in Ukraine

The sequence is following:
TX on RX off (PTT to ground)
EVENT 1 (active ground) -> EVENT 2 (active ground) -> EVENT 3 (active ground) -> EVENT 4 (active ground)
RX on TX off (PTT not connected)
EVENT 4 (active OFF) -> EVENT 3 (active OFF) -> EVENT 2 (active OFF) -> EVENT 1 (active OFF)

On this picture you can find the typical connection of sequencer board:

The power line of LNA should be connected to port which labeled TO LNA (look at the picture). This output does provide +12 V (same voltage as on VCC pad of sequencer) on RX and 0 V on TX (PTT active to ground). Do not use this port for something else beside the LNA power. If you need other than 12 V
coming from LNA port you have to remove the jumper (0 ohms resistor circled on the picture) and supply your desired voltage to point A. Do not exceed 30 V.
The sequencer board could work from 12 V to 30 V DC.

All boards that I have in my store are assembled, tested and ready to use. There is no tuning required unless if you want to change a sequence time.
I recommend to perform a PRE-CHECK before installation.
The Pre-Check is :
– apply voltage to the board at GND and +12 V points
– connect the PTT to ground and verify the TX sequence (listed above)
– verify the sequence on RX
– adjust a delay if it needs
– remove the DC power

This simple Pre-Check will show you how board is works. I have some cases where buyers damaged the board before installation and then reported the bad board. I strongly recommend to use a DIOD across all relays that you want to control from this sequencer. It will protect the board and save your nervous system.

Questions are welcome 24/7.

Alex K6VHF

Audio and CAT interface for Echolink or Digi modes

Hello everyone.
Do you like the Digi modes?  If yes you might like this device. Basically it’s the CAT and Audio interface in one box. I use the cheap FTDI chip which works great under Windows 7 and 8 without any issues and troubles with installation.

All parts are SMD and total cost of this interface just $10-15 and affordable for everyone. Good luck. Feel free to ask me.

If you want to have the PTT and CW commands just add following components:

With PTT and CW functions

With PTT and CW functions


Приветствую всех.
Данную схему разрабатывал для управления своих трансиверов. По сути у меня используется один интерфейс для двух трансиверов. Опробовано совместно с трансиверами Yaesu и Icom.
САТ интерфейс выполнен на базе FTDI FT232RL USB UART SSOP-28 чипа по классической схеме включения. Данный девайс отлично работает под многими ОС без всяких проблем с установкой драйверов. Последние скачиваются на официальном сайте . Опробовано под Win7 и Win8.
Звуковой интерфейс не представляет собой ничего особенного за исключением того, что добавлен простейший RC фильтр. Все выполнено в одном корпусе. В моем варианте также имется возможность управления усилителем (TX и АLC) без применения дополнительных разьемов. Все остальное понятно из фото и схемы интерфейса. Печатку не изготовлял, применял навесной монтаж, все применяемые детали SMD размера 0402. Сейчас работаю над новой версией устройства и программным обеспечением для управления трансивером и усилителем посредством одного USB кабеля, и индикацией режимов на компе на базе ATMega.

Из опыта:
FTDI чип слегка “шумит”, поэтому советую применять небольшие ферритовые колечки надетые на кабель в непосредственной близости от чипа, а также клипсы на каждом из кабелей.

Схема интерфейса:

CAT interface

CAT interface

CAT + Audio Interface for Icom and Yaesu Transceivers

CAT + Audio Interface for Icom and Yaesu Transceivers