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Building Bitx part 2- The crystal filter.

July 15th, 2008 Comments off

The 10 MHz crystal filter is one of the most important modules of bitx transceiver. Bitx uses an IF of 10 MHz. 10 MHz crystal filters are available at approximately Rs10 ( 1 US$ = Rs40 approximately) in the Indian market. I bought 10 crystals from a local electronics shop. The first thing I did was to number the crystals with a marker pen.


I wired up the following circuit (as described in Farhan’s website.

I didn’t have 680pf in my junk box I used 560pf capacitor. The circuit was built on a small PCB as shown below.


The Test Circuit


The crystal test circuit wired in ugly style

Then I measured the frequency of the oscillator. My readings are tabulated below.

Crystal no Frequency in MHz
before closing the
Frequency in MHz after closing the switch
a 9.99531 9.99819
b 9.99535 9.99809
c 9.99553 9.99832
d 9.99560 9.99835
e 9.99547 9.99818
f 9.99558 9.99809
g 9.99530 9.99810
h 9.99560 9.99824
i 9.99567 9.99827
j 9.99587 9.99814
k 9.99582 9.99815

As per Farhans advice I choose 4 crystals that are matched.

Then I built the filter as shown below.


The filter half built.


10mhz filter completed.


10 MHz filter fixed to a small PCB for testing.

I have the following test set up in my shack.

a) a frequency counter. ( A beautiful piece of equipment I bought form vu2ptr during ham Fest.)

b) A DDS vfo

c) An oscilloscope.


My Test Setup

I terminated both sides of the filter with 200 ohm resistors and then the DDS out put was fed to the filter. The DDS frequency was varied and the filter output observed on the CRO. I have taken readings at 100 Hz apart. I plan to plot a curve using gnuplot tomorrow.

How do they recruit teachers in Kerala

May 11th, 2008 4 comments

Today’s Hindu has an advertisement by Kerala public service commission for recruitment of High school teachers. The notification is available online at the commission’s website here

Here is the method of appointment” Recruitment by transfer from among the employees who have completed the 5 years of prescribed service and are working as  Clerk/ Typist/Attender/ Peon in Education Department.”

This is pretty ridiculous. If you join the education department as a Peon and some how attain a degree, you will become a teacher in 5 years.. I have seen this kind of academic degradation in Kerala’s polytechnic colleges.
For example, an 18 year old guy( somehow he passed the high school) is recruited as a watcher or gardener in a polytechnic . He will join a part time ITI ( certificate) course and complete it in 3 to five years depending on his intellectual capacity. The pubic service commission will appoint him a tradesman after some 5 years of glorious service( Here again a notification will come which will select from among peons or gardeners only). Then he will try to get a Diploma in engineering( may be by correspondence or from Tamilnadu). If he gets his Diploma in another five years, he becomes an assistant lecturer( again recruitment among peons/tradesman etc). Then he joins a part time BTech course. Another 5 years he will become a lecturer ( again closed recruitment among assistant lecturers). This process goes on and by the time he retires at the age of 55 , our poor gardener will be heading a teaching deparment. I can point out several such cases.
I am not against people building their careers. But here , a certain percentage of posts are reserved for such people and they need not compete with other outstanding guys outside education department. They become teachers by virtue of being a peon or an attender in a school.
I pity the future generation. May be I will have to teach them multiplication table when they reach our college.
Finally, please take a close look at the notification shown above. The public service commission has floated a short “tender ” for recruitment of teachers. I thought tenders and quotations are for purchase of materials by Government departments . My guess is that the under secretary who drafted the above tender might have been selected from among gardeners peons etc. 😀

Journey to the Hiranges

February 13th, 2006 Comments off

I am just back from a long journey to the high ranges of kerala. In fact Idukki is my home district, even though I am away from there for a long time now. My destination was a place called “Chempakapara” and my plan was to attend the marriage of one of my cousins. I started out in the early on 10th February and reached Thodupuzha around 11 am. Visited my uncle. He gave me two of his latest books.
I left his place around 2pm. The upward journey from Moolamattom to Kulamavu is exciting. There are 12 U turns on the way. I was a frequent traveller on this route during 1997-1998, while I was working in Model Polytechnic Painavu.
You can see a lot of surrounding places as you climb up. It is seen that there are some new tourist resorts on the way.
Once you reach Kulamavu, the bus crosses the Dam and enters into the forest. The bus journey through the forest is really refreshing. I was looking for wild elephants, but I could not spot any. The summer is slowly coming and some of the trees are showing signs of it.
I reached a place called Karimpan at around 3.30pm. Then, the further journey was on a Jeep. The jeep moved through narrow and dusty roads for about an hour. Many of the passengers were looking at me. It seems most of the people know each other and a stranger is easily spotted. The journey on the Jeep was really exciting. The driving was rough and many times the vehicle was passing through the edges for huge gorges. I reached my destination at about 5pm. I had to walk for about 15 minutes.
My cousins place is really good, located on a hill and surrounded by greenery it was real fun to stay there. Several of my relatives were present. There was a small liqueur party too. Locally brewed stuff was served along with beef and tapioca. I tried to tune my VHF handy. I thought Kodaikanal was very near, but I could not hear any stations.
Asha , whose marriage was to take place the next day, was brimming with joy. Ponmudi , where the marriage was to take place was some 20 kilometers away. The marriage party started around 10 am on 11th February. There were around 10 Jeeps in the party. The trip to Ponmudi was also interesting. We crossed Chinnar and travelled through numerous hair pin turns.
The marriage was a routine affair, except for a beautiful song sung in Anantha Bhairavi. ( I am hearing it for the first time in a church). After lunch I caught a bus to Adimali and reached my home at Thodupuzha around 6pm.
The journey to Idukki was really refreshing. I think I will revisit the places again.

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Some interesting articles to read

October 30th, 2005 Comments off

I have been reading a lot of radio related stuff this week.
Some of them are,

How to make a 40m reciever from a cheap chinese FM radio
Manual of TDA7088
Crystal Radio

Two other interesting articles I read were
Does Visual studio rot the mind and
Remembering Prof. John Kraus .

My ham licence is still elusive. I dont know how long it will take to come out from Delhi. Hopefully a month or a year .. 🙁

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