How to make foxhole radio receiver (with no batteries)

Foxhole radio receiver or Crystal receiver is a form of radio that does not operate on local oscillator, which makes it hard to be detected by other electronic device. One of the most interesting thing of Foxhole radio is that it could be operated without the use of batteries, as it is powered solely by the radio waves through its long wire antenna.

Foxhole radio was (supposedly) popular during World War II because it enabled the GI to receive radio broadcast in the middle of the war, particularly in France as the Germans has outlawed the use of radio by civilians, thus the American GI need to build their own receiver to receive broadcasts. Typical component of foxhole radio during those days are : a period razor blade (not the newer galvanized one), carbon (obtained from pencil) and some copper wire with woodblock or cardboard as its base.

I’ve found a video on Youtube on how to build a Foxhole receiver, it still requires considerable skills and experience to build a working version of the receiver though.

Hamradio Homebrew 2 Meter Square Dipole Plan

Here is a plan for homebrewing a 2 Meter Square Dipole plan. The advantage of this antenna is that it is unidirectional, and it takes less space than the regular 2 meter dipole. The calculation included on the diagram below is for building the antenna using copper tubing, you should use MMANA-GAL or other antenna simulation software to come up with new dimension for other materials (aluminium, wire, etc).

2 meter square dipole plan

2 meter square dipole plan

Click on the diagram to enlarge it. Hopefully this will help you in brewing new antennas! Original plan taken from KOFF website

Tak-Tenna Compact and Space Saving HF Antenna Review

Tak-Tenna is a type of compact antenna which is suitable for those who has space constraints on erecting their HF antenna. It is small enough that a 40 meter Tak-Tenna is just about the size of a 4-element Yagi 2 meter antenna. Here’s photographs of 40-meter Tak-Tenna in action. Compare that to the typical 40-meter dipole or Inverted-V configuration ! Thus it has the advantage of space-saving and unobtrusive setup when compared to other design of HF-antenna.

Tak-Tenna 40 meter
Tak-Tenna 40 meter

Tak-Tenna is available in 3 models – 40, 20, and 10 meters, with the 40 meter model can be use on 40, 30, 20, 15, and 10 meters with a tuner.

Refer to this article: “The TAK-Tennaâ„¢ Review – A Limited Space HF Antenna Review” for further review on Tak-Tenna performance and advantages.

Tak-Tenna can be ordered from the official Tak-Tenna website

Simple L antenna (2 meter antenna)

Here’s the simplest antenna that you can build to transmit with your HT or mobile rig when you have nothing else to rely to. The configuration gives you a 3.5dBi gain and it is simple to construct when you’re at outdoor.

Simple L antenna
Simple L antenna
Simple L antenna

I built this antenna, specially for hitting repeaters during lightning storm, as my usual high mounted antenna might attract lightning.

This antenna can be built using any conductive wire. Though, for my configuration, I use thick copper wires with the length A = 0.525m and B=0.4815m. The A-B angle is about 100-110 degree. It gives SWR 1.0 between 145.5MHz – 145.8MHz and SWR 1.3 at 148.0MHz, the edge of 2 meter amateur radio band.

Practice Malaysian Radio Amateur’s Examination (RAE) test online

Are you planning to take the Malaysian Radio Amateur’s Examination (RAE) this year? Good news for you as you can test your knowledge and skill using the RAE web quiz at –

Malaysia RAE Examination

The benefits of the the online web quiz are :

  • You will be able to test your knowledge before sitting on the real exam
  • You can customize the test set according to match your free time and level of comfort
  • Can view result of the test in whole or within specific section, allowing you to focus more on section that need to be improved
  • The question set mimics the real RAE test
  • It’s free, and you can take the test as many times as you like!

Amateur Radio: Malaysian APRS Seminar in Unimap (Perlis)

A seminar on APRS will be held in Universiti Malaysia Perlis (UniMAP) on 7 March 2009. Details of the talk as follows:

Name: Art Takahashi
Academic Qualification: Satellite Microwave System Engineer
Expert Field: Satellite communication engineer & Hamradio
Experiences: Hamradio licence holder about 40 years

Holder Radio Callsigns
Working for NEC Japan Yokohama & Australia Papua New-Guinia

Professional Bodies Membership:
Rens & Rens , Stedehouwer NERG
The Netherland , Australia Japan

Title: A.P.R.S (Automatic Position Report System)

Explain what is all about APRS, how it works and what do with it.
Main reason about my second visit is to Malaysia is to help radio amateurs in this country, to understand a other side of hobby. So they start building digital electronics project for the radio amateur hobby. (APRS)

Date: 7 march 2009
Time: 10:30 am ~ 1:30 pm the length from the seminar is depends about visitors interest.

Vanue: Lecture Hall, UniMAP Kuala Perlis.

Info Direction QRV: 9M2RMK 147.9800Mhz Shift -0.600 Tone 203.5
Info Direction on :
a) Wikimapia
b) Google Maps

Those interested to learn more about APRS technology are invited to join in the seminar. It’s free of charge!

RAE 2008-2 Results : Congrats to new Malaysian Ham!

Radio Amateur Examination (RAE) results is out! Congratulations to those who have passed the examination! Heck even piju passed the test!

You can view the results here : RAE 2008-2 results from MCMC website.

Important Forms to download :

For those who didn’t pass, dont despair.. there’s plenty of time to study for the next RAE!

Common Courtersy and Procedure when working with Repeater

  • Before making a call, listen to the repeater frequency for 10 seconds or more to make sure it isnt busy
  • If you are going to test if a repeater is working in your place, just announce “your callsign, testing” “your callsign, monitoring”. Do not press the PTT and listen for its tail feedback (kerchunking).
  • When joining a conversation, do not say “Contact, contact” that will make it harder for the stations on the repeater to identify you and arrange your station in a conversation, especially for mobile station. The correct way is to announce your callsign between the pause, or say “your callsign, join”.
  • Most Important: When people pass the mic to you, do not immediately transmit. Wait for 2 seconds then continue your conversation. Failing to do so will prevent others to join your conversation, and will make other people uneasy with you when you are on a repeater
  • When you heard a station requesting radio check on a repeater, then wait 2-3 second then respond. It is common courtesy to do so in order to help a fellow ham testing his setup. But you should only answer radio check when you are in a good position to do that yourself. See Below
  • Avoid answering to radio check when you are operating in a less than desirable setup, such as operating on a moving vehicle behind mountains or tall buildings. Worst if you are operating from a moving vehicle with rubber ducky antenna
  • Please give an honest report to a station when responding to a radio check. If the station can barely hold the repeater, just say so. Do not give a Q5 report on a Q2 signal. The station might be in false impression that it can established a good transmission between repeater and this going to create undesirable interruption during a conversation.
  • Leave a conversation when the other stations are giving you a Q2 signal report, unless if its an absolute emergency. your signal would be too noisy to be readable by other stations it will disrupt communication.

Non Repeater specific

  • When signing off, simply say “guys, I need to sign off because i want to attend some chores, waiting for your final“, then pass the mic. Avoid using Q-Code, especially the wrongs one. Some station even combine QRU, QRX and QRT together in conversation when signing off, this will create confusion to newcomer as well as old-timer as the codes were used wrongly in this type of situation.
  • Using tons of Q-Codes simply to look cool, isn’t going to make you sounds cool . Using QSY as in “I’m going to QSY to Singapore tomorow” is not correct, QSY should only be use when you are changing frequency. Just say “I’m going to Singapore tomorrow”, sounds even better. Malay rendering would be like this, “Esok saya nak QSY ke Kuala Lumpur” versus “Esok saya nak pi ke Kuala Lumpur“. Notice the pronunciation “Q, S and Y” actually makes the conversation longer and harder to pronounce than a normal conversation. Try and think it over

Note that this post serve as a general reminder to myself as well to others when working on air, especially on a busy repeater. It is just a common sense guideline which I accumulated from old hams over time and it is a good advice to be practiced by all hams.