Mare & Gal Electronics

Introduction

I have couple of raspberry pi’s laying around doing nothing useful. I decided it’s time to use it better than dust collectors. This tutorial is placed here for reference for any OM who would like to setup APRS Rx only node based on R.pi. Here’s what you’ll need (hardware):

• Raspberry Pi (I have model “B”)
• At least 4GB SD card
• PC running windows
• RTL USB DVBT Dongle
• 5V USB power supply (or powered USB hub)

… and software:

• RASPBIAN Debian Wheezy
• Win32DiskImager
• and other, installed directly from r.Pi

Continue reading ‘Raspberry Pi + RTL SDR dongle = APRS Rx only gate (Part one – FM Radio)’ »

I was looking for dummy load on ebay for HF testing. All dummy loads were too expensive. Then I found bag of thick film resistors. Unfortunately they were 820 ohm, which is not optimal for 50 ohm load, but close enough. Then I constructed two PCBs.

The construction is simple…

At the end I would like to put everything into oil bath to make it more suitable for high power testing.

The small SMA connectior is for measuring via the 1:10 voltage divider.

Here’s altium PCB for the two boards: dummyload (31.10.2014 21-23-06)

During summer vacation in 2014 we had new piece of equipment for portable work. The QRP rig FT817ND is excellent for quick setup and has low power consumption to operate from battery for many hours.

Our Balkan tour started in Korčula island, where Gal S57GP and myself S54MTB operated from 27.08.2014 to 02.08.2014 with 9A/ prefix.

Continue reading ‘Balkan tour 2014’ »

I bought 6 alluminium tubes, 2m long, diameter from 45 down to 20mm for 40m quarter wave vertical antenna. This 10m simple construction collapses to 2m pack with nly 45mm diameter. The base is made from PVC plastic isolator, which is fixed to alluminium plate with 4 M6 screws and additional nut, placed inside the plastic hole, which is normally used to fix the steerer tube on the bicycle.

Photos are worth more than 1000 words…

Continue reading ‘Alluminium vertical for 40m’ »

This is part II for 4 element 6m yagi. Part I is about metal parts. Here is some brief description about electrical connection and preliminary test.

4. Antenna feed

To finish the antenna few parts must be 3D printed (or produced with other materials, like plastic pipes). Holder for air coil consists of three parts: coil holder, coil support and connector holder.

Coil holder is simple cylinder (pdf drawing: chokeholder), which is long enough to accommodate 12 turns of RG58 or similar cable:

Continue reading ‘4 element Yagi for 6m, part II’ »

S57GP and S54MTB rode mountainbikes (MTB) to local SOTA summit. The expectations were low, because it was our first contact with SOTA activation. We started in Idrija with two small rucksacks with HAM equipment, two bottles and two bikes.

Our destination was Kobalove planine (Mount Kobalove) with SOTA reference S5/TK-026. The summit is nicely visible from Idrija. We took the road through Idrija centre. The road turns right and uphill just in front of old elementary school. After few km we reached the tourist farm with some cows and beautiful views. The weather was excellent.

Continue reading ‘First field experience’ »

6m band is sometimes called “magic band”. It has combined propagation properties of HF and VHF. When conditions are good, very long DXs are possible. Beside the sporadic E occurence some other requirements are essential. One of the most important pieces of equipment is good antenna. There is no shortcut for good performance in small package. Good antenna is big when lambda is long. For 6 meters, the antenna usually occupies about 3x3m floor area. Here’s my implementation based on Ljubisa Popa – POP  YU7EF design EF0604S.

Continue reading ‘4 element Yagi for 6m’ »

Me and my son recently got HAM licence. No, it’s not about meat from pigs, but amateur radio. Our call signs are S54MTB and S57GP.

We started with small QRP (low power) rig Yaesu FT817 ND and homebrew antennas.

If you are interested in radio-amateur (HAM) related topics, please follow the “Ham” section.