Old Style Simple Transmitters

QST Sep. 2013. In Technical Correspondence, there is a short article "Fun With Old Style Simple Transmitters" by Larry, WR1B. The basic idea is to build the 1946 style transmitter in current technologies. It uses the 74AC540 logic chip to put out 1W of power (with 6V). Clever.

Homebrew 50W linear amp for QRP transmitter

I found an interesting article on building a linear amp with MOSFETs: Homebrew Challenge II Co-Winner, The Lowest Cost Entry (David W. Cripe, NM0S), QST October 2010.

It uses two IRF520 MOSFETs that operate in Class E mode. The technique called Envelope Elimination and Restoration (EER) is used to make this a linear amplifier. As MOSFETs are relatively cheap and the efficiency of Class E amplifiers are very good (around 90%), this is something I am interested in and I would want to experiment with sometime.

Monitoring ADS-B System

I found an interesting article from TCA July/August issue.

In All Things Digital, Robert(VA3ROM) presents an article Monitor and track aircraft using the automatic dependent surveillance -broadcast (ADS-B) system.

I may have a necessary dongle so I would try when I have a chance but these are the summaries.
- Frequency : 1090mHz/1030 mHz
- RTL2832U dongle with R8207 or E4000 tuner (for DVB-T and DAB signal reception)
- adsbSCOPE software (free)

With the stock antenna (designed for lower frequency range), the reception range is about 75kM.
There are also Internet tracking sites.
- flightradar24.com
- planefinder.net
- planetracker.net

GNU Radio & RAC Canada Day contest

It is a long weekend. I am trying to do something useful during this weekend.

One of them is to start experimenting GNU Radio as I have been interested in the software defined radio(SDR) technology and its development. I have not been so passionate though. I installed something called UHD and GNURadio as per the instruction on the website. Unfortunately, it does not seem to work. It complains my computer is missing some DLL file. I will investigate this error later.

Monday, July 1st, is a contest day. I have been participating at the RAC Canada Day contest almost every year. I have won the contest twice on the single band (28Mhz) category. The reason for choosing 28Mhz band is because it is relaxing as there are not many contacts to make on this band. Maybe I am thinking to work on 21Mhz band this year to be a bit busy. The 21mhz band is more widely open apparently and the situation would be a lot different from 28Mhz, especially considering we are at the solar maximum this year even though a clumsy one.

 

OpenBeacon

An interesting beacon transmitter kit. I want to try this out sometime in the future when I have more time.
http://www.etherkit.com/transmitters/openbeacon.html

The following is a quote from the site.

Quick Overview

OpenBeacon is an open source crystal-controlled QRPp beacon transmitter kit which can output a variety of slow-speed modes, including QRSS, DFCW, and Sequential Multi-tone Hellschreiber. It is configured via USB port, so there are no jumpers to set and you can easily adjust all of the operating parameters via command line. Once configuration is complete, OpenBeacon may be removed from the PC and operate stand-alone.

D-Star net check-in

I checked into Cannet D-Star net through VA3PMO-B repeater (Mississauga) tonight. The net starts at 9:00PM EDT on Friday. This is my first time to check in to a D-Start net. I bought an Icom IC-91AD a couple of month ago. It is a different kind of fun to use or hear digital voice signal. I confirmed my D-Star rig is working, hi hi.

TS-590S portal

I have come across with a nice page for TS-590S. At the moment, I am interested in the articles that explain how to monitor the rig's  CAT commands in particular.
http://homepage.ntlworld.com/wadei/ts-590s.htm

UZ7HO AX.25 sound card modem

I tried to experience the UZ7HO AX.25 sound card  modem. The program can be downloaded from:
http://uz7.ho.ua/index.php?lang=eng&id=4
I installed it on my Windows 7. After launching the program, I set the modem baud rate to 1200bps, and monitored the APRS frequency on 144.390Mhz. With the internal mic, the signal shows on the waterfall but is not decoded. I tried to raise the mic gain from the menu but it does not seem to work - i.e. nothing happens after I select the menu item for setting the input gain. I will read the manual again thoroughly to see if there is something I may be missing.

There is a UNUN schematic provided by K0BG.

An F114-67 ferrite core is used with a few feet of #14 enameled copper wire (enough for 9 bifilar turns).

160m small receiving loop antenna

I found this small loop antenna diagram from an old magazine. It looks to be a reproduction of the 1938 QST drawings of the W6GPY receiving loop antenna for 160 meters. If the 4-turn is reduced to 3-turn, then it will cover 80 meters. One separate turn is used for coupling.

Then the following is another version of the W1FB loop as discussed in July, 1977, QST magazine.
Alright, the picture is upside-down.

50Mhz band plan

I copied the 6m band plan for my future reference. As a non-frequent 6m Ham radio operator, I do not bother to memorize this complicated band plan.

LF local oscillator idea

I found this schematic. What I am interested in is the circuit portion of using the schmitt trigger nand gate IC - CD4093. This can generate a frequency somewhere between 70Khz to 1Mhz or it is what I read. I bought the IC while I was visiting a store in case I need a low frequency local oscillator.

Intersting links for Android audio interface

I found a couple of interesting web links this morning. I have been thinking about developing Ham radio applications on Android. The major part that I have not figured out yet is how to sample audio data from Andriod audio input. It would need more digging for available APIs.

This gentleman (or company) must already figure that out and developed a hardware interface to be used with his applications including DroidPSK. The link is:
http://www.wolphi.com/android-apps/droidpsk/droidpsk-to-ft817-interface

He references another interface link upon which his design is based:
https://sites.google.com/site/kh6tyinterface/

The above shows how to enable PTT using the audio input from a receiver.

design a no-tune amp on your computer

This is an article that I found interesting from ham radio Sep. 1987.
The article is for designing a broad-band tube amplifiers.

Preparing ARRL 2011 Field Day

I am planning to use my FT-707 transceiver for the field day. It seems to work so I will be preparing a PSK31 interface cables to test drive for a couple of weeks to make sure that I would be well prepared for the field day.