Amateur Radio

Ham Radio, Hobby Projects related to Communications.

A long, long time ago a bright ape figured out that by climbing down from the trees he could more easily master his life, and that of others……Homo sapiens wanted something else, and better. He started to play. Homo ludens was born!

Homo sapiens to Homo Ludens

  • Homo ludens radiactivus – amateur radio
  • Homo ludens radiohistoricus my antique radio collection
  • Homo ludens electronicus – electronic projects
  • Homo ludens aeromodellisticus – model airplanes

Transformers and coils: This is not a building project, but a short and concise lesson in how to design electromagnetic parts. It’s much simpler than what you may expect!

A 40 meter SSB QRP transceiver

A 40 meter SSB QRP transceiver

“This transceiver was conceived as a power-efficient, small, lighweight unit to be carried in the backpack, along with antenna and battery, for use during trekking and mountaineering trips. It had to be reasonably rugged and reliable, and perform well. Furthermore, I wanted it to solve all the problems the old DSB transceivers had, such as frequency instability, distorted modulation, lack of sensitivity and selectivity, and others.”

The only way to improve the reception of FM-signals or particularly of stereo FM-signals under disadvantageous receiving conditions is to amplify the antenna signal. This should be made directly at the antenna, since the loss is increased meter by meter of any cable. In most cases higher line attenuations can be expected than usually calculated. Even receivers with an additional noise figure of zero do not show any improvements of the signal-to-noise ratio becomes too low because of a long transmission line. Therefore it is practically useless to require extremely low noise figures only for the receivers.

To avoid interferences of signals received from stations of other bands it is propitious to amplify the FM-band only. The band amplifier shown in Fig. 1.3 is connected directly to the 60 ohm output of the FM-antenna, i. e. it is placed at the top of the antenna pole. The matching is achieved by the input band-pass connected to the base of transistor BFT12, being a typically linear silicon transistor for broadband amplifiers. The output filter matched accordingly to a 60 ohm coaxial line is connected to the collector. The operating voltage of 15 V can be supplied by the coaxial line.

Fig. 1.3

Antenna-amplifier with BFT 12 for FM-range

Technical data:

  • Power gain Gp = 22 db
  • Noise figure F = 3.5-4.0 db or 2.2-2.5 KT0
  • Input and output reflexion coefficient |r1| and |r0| <= 0.3
  • dim(60db) at Vout = 680 mV
  • dim(50db) at Vout = 1000 mV

Optimum operating point of minimum intermodulation

Ic =~ 80 mA Vce =~ 7-7.5 V
Supply voltage 15 V

Coil data:

Vogt coil former, ordering code: Sp 3.5/16.6-2048C
Core: U17

  • L1 : 5 turns Cu 0.6 mm \o
  • L2 : 3 turns Cu 0.6 mm \o
  • L3 : 3+2 turns Cu 0.6 mm \o

Choke Ch1 = Ch2: 20 turns Cu L 0.3 mm \o, cross section of winding = 4 mm

Credits –

Antenna-amplifier with BFT 12 for FM-range
from Design Examples of Semiconductor Devices – Siemens

The new Ham Project Pages are VHF/HF Aerial Analyser, A 600MHz Frequency Counter.  Then there is a an ESR Meter for Electrolytic Capacitors.

VK5JST Amateur Radio Ideas with Photos

With a two tone tester, a dummy load and an oscilloscope, a transmitter can be really put through its paces. Two tone testing consists of applying two clean non-harmonically related sine waves of approximately equal amplitude to the audio input of an SSB transmitter.

Simple Two Tone Oscillator

 

The sine waves are typically around 600 – 700Hz and 1800 – 2000Hz i.e. about 300Hz from either end of the audio pass band.

A Simple Two Tone Oscillator

This project was published in the September 2004 issue of the Australian magazine “Amateur Radio”.

Other Readworthy Pages

  • Easy PCB’s Made With Kitchen Appliances
  • How to Make a Q Meter
  • Making a High Current 13.8 VOLT Supply For SSB Transceivers
  • VK5MM’s excellent amateur radio homepage
  • Transformer Construction Details
  • Shortform Method of Designing Power Transformers

The photos at VK5JST Homepage are very educative and express the idea better than words. – delabs

Designing Bipolar Transistor Audio PreAmps, Designing JFET Transistor Audio PreAmps, Designing Op Amp IC Audio PreAmps, Switching Regulator Basics, Using Transistors As Switches.

RASON Projects Page – Amateur Radio

  • 10 Amp, 13.8 Volt Power Supply
  • 12 Volt Gel Cell Charger
  • Thermal Fan Controller
  • Transistor Audio Amplifiers
  • 12 Volt Gel Cell Charger
  • Switching Regulator Basics

 

A Potpourri of Audio Amplifiers  By N1HFX

“I intentionally avoided the use of IC amplifiers to provide a real learning experience for audio amplifier design. Although many IC amplifiers provide excellent performance at low cost, we need to learn the basics first. I will address IC audio amplifiers in a future article.”

The Radio Amateur Society of Norwich
P.O. Box 329 – Norwich, Connecticut 06360

I am designing a circuit that implements an AM radio circuit that ultilises the IC Double mixer and Oscillator NE612. I was just wondering whether there is any standard symbol for this kind of IC.

mail from CM


There is no standard symbol for NE612, just a square box. You have to make a custom part in the CAD software or see if someone has done that. check these links on info of NE612 circuit and symbol….

GM47: Simple 30m Band QRP CW-Transceive

The Rx mixer is followed by a IF stage featuring an NE592. The mixer’s balanced output is directly connected to the amplifier’s differential input, minimizing component count at this point.

Simple 30m Band QRP CW-Transceiver

Direct Conversion Receiver using NE612 for HF Bands

The NE612 is an integrated circuit which contains a balanced mixer with its own on-board local oscillator and voltage regulator. The mixer can provide up to 18dB of gain at 45 Mhz, and the local oscillator will operate up to 200 Mhz.

HF Transceiver using NE612

I would be working on the Transverter first, as with this, I could try out the 9Mhz SSB Module that I already have. I would be building the Transverter for the 14 Mhz band depending on the values from my DC Receiver project using the NE612 IC

delabs

“One day I noticed a project, obviously homebrew, mounted on a piece of plywood, and nearly covering the worktable. When I asked him what it was, he glowed as bright as the half-dozen tubes that lit up when he turned it on. Twenty seconds or so later, out spews from the speaker the cracklings and whistles of 40 Meter CW. I was amazed, and at that moment the homebrew bug bit me hard. I was determined to build something myself, and get my ham ticket.”

N5ESE – Gizmos for QRP Ham Radio

N5ESE - Gizmos for QRP Ham Radio

N5ESE’s GIZMOs For the QRP Homebrewer and Ham Operator

“Everybody loves a “gizmo”. Hams have a weakness for them. Gizmos can be expensive for full-power amateur radio equipment, but homebrewing QRP gizmos is “cheap and easy”. Most of the projects here cost less than $20 (or nothing, if you have a modest junk box), and take only a few hours to build). Most are even suitable for the novice builder. And all have real practical value, especially for homebrewers and QRP operators. “

Amateur radio is a technical hobby. The attraction? To cover long distances with a low power radio to talk with other people, learn about their countries and cultures.

Amateurfunkbasteln – Amateur Radio Crafts and Electronics

But amateur radio also means tinker devices themselves, solder, apply electronics and learn something. In this sense, it can be a preparation for a technical career or even an engineering degree.

Use Google Translate, the pages are in German.

A Data Logger that records Slowly varying parameters, such as the temperature or decreasing the voltage of a battery. This copy records up to four measurements on parallel and saves it on a EEPROM.

Four Channel Data Logger - Amateurfunkbasteln

Four Channel Data Logger

It measures self-sufficient – without a PC – analog voltages (0-5V), it digitizes and stores the numerical value obtained in a separate memory. Later, after the measuring and recording phase, passes the data logger its information to the PC.