Archive

Archive for the ‘Ham Radio’ Category

Adding CW to bitx

June 24th, 2009 Comments off
Bitx Cw module

Bitx Cw module

I was playing with  my bitx build yesterday. Specifically, I tried to add CW  to the rig.   Original bitx20 is a SSB rig.  I my mod was inspired from PY2OHH bitx40.  I  wired  up a 10mhz crystal oscillator as shown below.

bitx20 CW module

The idea is to inject 10mhz ( approximately) at the  beginning of transmitter IF amplifier. This will in turn produce 14 mhz sine wave at the output.  The receiver part is unmodified.  See the diagram below.  Connect  the point marked X to the point x .

Bitx 20 modified for cw

Bitx 20 modified for cw

Adjust the  10Mhz oscillator to  around 700khz above the  BFO frequency. I added a small inductor (10 micro henry) in series with the crystal to adjust the frequency near BFO,.It is not shown on the figure above.

Categories: Ham Radio Tags: , ,

How to become a HAM radio operator in India

June 14th, 2009 10 comments

Several friends have asked me to explain the procedure and formalities of becoming a ham radio operator in India. Unlike many of the western countries , the active population of amateur radio operators in India is very minuscule. The major reason for this is the cumbersome procedure and the lack of interest from concerned authorities.

Obtaining a license can be a tiresome process. The general algorithm for obtaining a license is some thing like this.

1) Decide whether you are really fascinated by the hobby.

2) Get hold of the application forms and fill them out.

3) Send them to the nearest monitoring station

4) After 2 to 4 months you will get get an intimation from the monitoring station, asking you to appear for the ASOC examination.

5) Write the examination and forget about it. If you are successful, you will get another  intimation from the monitoring station  within 2 to 3 months.

6) Get yourself into an infinite loop. This will allow the government to verify about your antecedents

7) If you are lucky, the Ministry of communication will interrupt you to remit the license fee ( you are still in the loop :D)

8) Once you remit the fee, you may get a license in another 2 ( may be more) months.

By this time any reasonable Indian will have lost his interest in the hobby.

I will now attempt to give more information on tackling the algorithm.

Step 1

This is the most important step in the process. Read about the pros and cons of becoming a ham. Whether you will have the time ( and money) to build and operate a station. Interact with a nearby ham about the virtues. If you are a geek, you have a better chance.

There are several website giving information on ham radio. Look  around them. You can start with  this and this.

Get hold of a decent radio ( ordinary broadcast band radio with short wave band.) . Most of the amateur operators in India work on 40M and 20M. You can easily tune to 40M on an ordinary radio. The 40m band is from 7.0 to 7. 1.Mhz. Most of the radios will have 41M marked on their dial. So our 40M band is just below that.

Build a simple VFO and place it near the radio. When you turn the  tuning  capacitor on the VFO , you will get a sharp whistle on the radio. Now,attach  a long wire to the telescopic Ariel  of the radio. Make the length about 10m and  hang it horizontally. Tune around 40m band.

The circuit of a simple 40m VFO is given here.

Most of the amateur activity on 40M band is around 7am to 8.30am  IST  on weekdays. On Sundays, you can find some stations through out the day. However,  better band conditions prevail during mornings.

Listen for some days and see whether you like to be a ham.  A  good ham station can be built at a cost of say   Rs 1000.  You  can alternately purchase equipment costing lot of money. For building a station you need to put in lot of time and effort. Think well before starting out.

Step 2

For me this was the most difficult step. I will give you the details.

In India. there are four kinds of amateur licenses. They are:

1) Advanced grade

2) Grade 1

3) Grade 2

4) Grade 2 (restricted)

These licenses are issued by the Wireless Planning and Coordination section(WPC) of Ministry of Communications Government of India.( They have a website but seems to be down for some time ) For obtaining the license, you must appear for an examination conducted by WPC. The examination will cover topics in basic electronics, radio regulations and Morse code. This examination is called Amateur Station Operator’s Certificate (ASOC) examination. The rules regarding amateur radio is here. The syllabus for the examination is also available along with the rules.

Depending on your license, the power output and frequencies that  you can use vary. For reasonable operations on the air, you need at least a grade 2 license.

The application forms for the examination is here. You have to fill out the form. Against item no 9 (Particulars of apparatus used), you can write “home brewed”. You  need to fill in 4 copies of personal details . and   4 photographs.

Take a Demand draft (DD) for the required amount. The draft must be purchased from State Bank of India.( This is very specific,no other bank acceptable. )  You can apply simultaneously for grade 1 grade 2 and grade 2 restricted. It is a good idea too. So purchase a draft for Rs 40. in favour of " PAY AND ACCOUNTS OFFICER (HQ), Department of Telecommunication " payable at Service Branch, New Delhi .  The guy at the bank counter looked at me scornfully when he saw my application for  demand draft. The DD commission was around RS 25.  He also warned me that I may not be able to cancel the DD later on.

There are few attachments to be submitted .

a) Nationality certificate . The format of nationality certificate is here. The certificate must be from a  Gazetted officer of the state or central government or from the Principal of a school/college.

b) Personal details 4 copies.

c) photographs (4 nos)

d)(Optional)  If you have a B Tech in Electronics and Communication Engineering, you can furnish a copy of the certificate. You will get exception from  part 1 of the examination.

Step 3

Once you have filled in the application and collected all certificates , send the application to the nearest wireless monitoring station. The  list of monitoring station are available here. Please note that your DD is payable at New Delhi, even though you are sending the documents to  a local monitoring station.

The examination will be conducted once in three months in most of the monitoring stations. They will  intimate you the date of examination approximately 2 weeks before the examination.

Step 4

Preparing for the examination

Now you have to prepare for the examination. There was a book named ABC’s of Amateur Radio in India published by EFY. I think it is almost out of print. You can download the book ” A Guide to ham radio ” from Vigyan prasar.

Learning Morse code

There are several software’s available for learning Morse code. Links to some of them are listed below.

There a good tutorial CD published by ARRL. You can buy it here.

Alternately, you can download lessons teaching Morse code in KOCH method from here.

PC  based tutorials are available on the Internet. You can try cwcp on GNU/Linux systems.

Learning Morse code can be difficult for some people. But if you practice it consistently , it can be mastered in 3 weeks time. The Morse code test has 2 parts. Morse code sending and receiving. Sending part is pretty easy .

Step 5

The actual examination is a silly affair. There will one only one or two candidates  present. The WPC officials conducting the examinations are  generally helpful.

See this post for some sample question papers.

Step 6  7 and 8

You don’t have much to do other than  waiting for a letter from WPC.

There will be a police verification.  But it is done in  a clandestine manner. Don’t bother about it, if you have a clean record.

Once you get it remit the fee  and get hold of a call sign and enjoy your hobby.

Probably, you will be 2 to 3 years older by this time.

Categories: Ham Radio, Living in India Tags:

Manhattan Style construction for Hobbyists

May 7th, 2009 3 comments

Most of the home brewers and electronics hobbyist  see  fabricating  a PCB as a roadblock . I  will describe an alternate approach to circuit construction where you  need only bare copper clad sheet. This method is some times called Manhattan method.( I don’t know the reason.)

The basic ingredients  you need for this type of construction is bare copper clad sheet. Either glass epoxy or paper phenolic  boards can be used.  As the first step take a small pieces of copper clad sheet and chip it into small pads. There is no minimum size or maximum size . Use a sharp tool like a chisel  for cutting the board. Some sample pieces that I made is shown in the figure below.  If you have access to a sheet metal cutting tool, it is very easy to make them.  I keep a small box of such PCB chips.

050720093144

Collect all the components that you need for construction.  Study the circuit you are planning to build  and make a rough  layout of component placement  on paper. Pay special attention to the size and shape of the components you are planning to use.  If possible,  make  the circuit layout  section by section . This will make debugging easier.  The circuit will be fabricated on a a plain copper clad sheet .The copper clad sheet will be the ground of your circuit  Keep this in mind when you make the sketch. Here is the circuit and  a rough sketch I made for constructing  bitx20. ( This is RF preamplifier stage of bitx20).

ckt 050720093154

Make a pad layout next from the above layout.

050720093155 050720093145

The size of the copper clad sheet needed can be roughly estimated if you have some idea about the components. Cut a sufficiently large piece of copper clad and then clean it properly.  Affix the pads using super glue. Any other adhesive used in electronic repair can be used.

050720093143 050720093146

Now start soldering . Make sure that the pads are clean. I use a sharp knife to clean the pads. Start with the resistors. Keep the leads small..  Next , solder the capacitors followed  by other  low foot print components.

050720093147 050720093149

Finally, fix the transistors. You circuit is ready for testing .

050720093152

There are several advantages to this type  of construction. The plain copper clad sheet will act as a ground plane and will improve the performance of RF circuits. Also, If you want to replace a faulty component it is very easy.

Categories: Ham Radio Tags:

Bitx 20 update: The band pass filter.

May 3rd, 2009 1 comment

The  bitx, I  built using the ugly construction method was too ugly to look at.   The board  was rebuilt using Manhattan style construction last week end . Now the board looks tidy and neat. The added advantage is that  I can plug and play with any section.  Individual sections are built on smaller PCBs and all sections are  glued to a larger copper clad sheet.

Bitx Rebuilt in Manhattan Style

Bitx Rebuilt in Manhattan Style

However, the power output in transmit mode was very low.  Up on investigation , it was noticed  that the band pas filter was not performing well.

Bitx version 3 band pass filter

Bitx version 3 band pass filter

This morning, I decided to  experiment with the band pass filter.  My board is based on version 3 schematic of the bitx and the band pass filter was built from old IFTs recovered from a junk radio reviver.  The filter was  not tuning properly. The output at the end of the filter was very low ( 100 mv)  May be the ferrite  used  in the IFT is of inferior quality.

The  band pass filter that was built with IFT

The band pass filter that was built with IFT

I looked around my junk box and found out some small resistor looking  inductors. I decided to try the  band pass filter  from the original design. This design uses 2 ?h inductors wound on tap washers. Fortunately, I had a few 1?h

Bitx version 1  band pass filter

Bitx version 1 band pass filter

I built the circuit as shown below and soldered it to the board.  Oops. The performance went down. I was getting only 50mv  on transmit and the receiver performance also suffered.  Again ,I suspect the  junk box components. I thought of rewinding the coil using tap washer.   Ferrite slugs and torrid cores  are not easily available in this part of the world.

Bitx Version 1 bandpass filter

Bitx Version 1 bandpass filter

. I looked around the junk box again and found out a set of coils used for 3 band broadcast radio.  I decided to rebuild the  version 3 band pass filter again

The radio coil rewound

The radio coil rewound

The coils were rewound .  I  used 11 turns for the main winding and 3 turns for coupling winding The coil inductance was varying form 2.7 to 1.65 micro henries.  The completed filter was installed and bitx powered up . Now I was  getting around 700mv RF  from the filter stage.  I am yet to test the power amplifier section . I hope I will get 5 watts as advertised.   With the new filter in place the receiver performance has improved tremendously. I can hear lot of stations both on CW and  SSB.

Bitx with the new front end filter

Bitx with the new front end filter

The signal I got while whistling to the mic is also shown below.

Scope waveform after filter

Scope waveform after filter

Sample question papers for ASOC Examination

January 16th, 2009 9 comments

The Amateur Station Operators Certificate Examination is conducted   by Ministry of communication Government of India.  You have to pass this examination if you want to be a HAM radio operator in India. Several SWLs have asked me  about the nature of the examination and how the question papaers look like. I am posting some sample papers that I collected when I wrote the examination.
This Zip file has several sample papers that you can try before the actual examination.

Categories: Ham Radio Tags: