My small toys. Telephoto lens.

Today I have received and tested the small telephoto lens. It can be used either as an addition to the phone or tablet or as a standalone monocular. The box contains the tripod and phone holder (as shown in the picture) as well. Please note, the holder is suitable for 5-inch phones or less. Mine is 6.44" and didn't fit the holder. Also, there is the cap covering the viewfinder of the lens. But I would like to have one more cap to protect the front side of the lens. However, I can use some plastic box of appropriate size to keep the device in safety, though.

Chasing satellites. Part 3. FM Repeater Satellites.

There is a lot of satellites spinning around the Earth. Almost all of them have their own purpose and are useless for radio amateurs. But some of these satellites can be (and are) used by HAMs. Specifically, these are ones having FM repeaters on board. Below is a table containing information about all the satellites with FM Repeaters.

Chebyshev BPF: designing the PCB.

Recently I realized I need some number of filters of a different kind: lowpass, highpass and bandpass. The ready-for-use ones are pretty expensive and cannot be customized for my needs. Therefore I have decided to start building my own ones.

Everything starts from scratch. In my case - the schematic. I have dug the Internet and found some number of diagrams I could use. Below is the one I have used for my work. This is a bandpass filter developed by Sinisa Tasic-Tasa, YU1LM. A very good starting point.

Chasing satellites. Part 2 - listening on Icom

This evening I used the mobile Icom IC-F211 for listening to the satellite for the very first time. I heard IT9ZSB, and even was able to conduct a QSO with OH5LK.

Chasing satellites. Part 1.

Last winter I discovered a very nice activity: chasing the radio amateur satellites. I built the handheld antenna (open sleeve, 144+430 MHz on the single boom and being fed by the single cable), attached it to my handheld radio Wouxun KG-UV6D, and started listening to satellites and, quite later, transmitting. That was amazing! I loved this activity very much. It's an unforgettable feeling when you stay in the middle of the field covered by snow, hold the antenna in your frozen hand and try to not forget the callsign of the station just called you.

Bosch KF-166-6

Couple days ago I have bought a nice specimen of mid-1980 devices - the VHF automobile transceiver Bosch KF-166-6. Specifications say:

The Bosch motor vehicle radios KF 166 Chp operate in the 2m band of 146-174 MHz with a channel spacing of 12.5 kHz, 20 kHz and 25 kHz in Simplex or Semidupiex modes. The devices are intended for non-public land mobile broadcasting and are supplied in 2-channel version. It is possible to use a 5-tone sequence encoder-evaluator simple design without remote coding or a uP-controlled 5-tone sequence encoder-evaluator with up to 5 digit encoding.
Depending on the version, the transmit power is 6W, 12W or 25W (export only), the NF output power is about 4W to 4 ohms. The devices are for the connection designed for vehicles with 12 V and minus pole on the vehicle chassis. For other voltages, use a ballast regulator or converter.

Powerful dummy load. Step 1.

Recently I have got some parts required for the creation of the powerful dummy load.
They are:
- heatsink;
- non-inductive resistor;
- connectors (RF and DC 12V).

Magnetic Loop. How to retire capacitor?

It is known that the most valuable piece of the magnetic loop antenna is a capacitor, which must be able to handle very high voltage in case of 30+ watts of emitting power (up to 5000V for 100 watts).

The construction of the Magnetic Loop antenna is pretty simple: the one or two loops of wire (the more diameter of the wire is better) and capacitor breaking the loop. But in case of making the loop using the coaxial cable, there is an ability to retire the capacitor. The reason is simple: coaxial cable has its own capacitance. Therefore if you know the linear capacitance of your coax you can calculate the required length of the cable which creates the resonant contour on the desired frequency. Below is a sketch of the coax wiring allowing you to use both the cable shield and the linear capacitance of the coax (the image source).

Magnetic Loop. First impressions.

Yesterday I finished building my Magnetic Loop. I will provide all the details later, as soon as prepare pictures for the article. Now I would like to say the following: the tiny (in comparison to the half-wave dipole) antenna placed only two foot above the ground among a lot of trees and buildings is able to receive signals from all around the world! I tried it for transmission (FT8, driving 10 watts), but almost unsuccessfully - a lot of people heard me but only a few contacts appeared on my log. Next time I'll try to run in from the top of some building to ensure that the height of the antenna above the ground does matter.