Wednesday, April 23, 2014

Dummy Load

To give a standard Lamp-test of the  VWN 40meter a lamp was needed. This vwn tx uses  the premixed 7059kc (11059-4000 kc xtals) as reference oscillator.

First Tried the kcommon electric lamp. It did not work. Then went for the torch light lamp.

Searched, in the general stores, paanwalahs and all sort of peoples who used to sell the torch lights and electronics related goods. No way. One gave me a fused lamp for rs10/-. then i was watching the autor rixa repair job in the station area, wow its tail has the good old lamp. i asked repair man and he said two types of the lamp are used. one is 12volts, 35 watt as head light and other is the 12 volt, 5 watt as tail lamp. Oh my god, i searched the entire city and they were found near my qth and this 5 watt lamp is cheap also. Just rs.5/- per pices. It will be available for some more time. So, this is a standard and cheap thing.

When i used the 5 watt electric light lamp, i could not get it lighted up in the transmitter. so was worrying whats wrong! is it the transmitter not pumping out the oscillations ? whats up mate !

Now, found the solutions in the form of ohm low. here is little maths to muse.

for auto tail lamp:- it takes 12 volts dck at 350 mili ampere. which turns out the about 33 ohm. near about the real dummy load of 50 ohm.

for the electric lamp:- by this ohms law resistance becomes very high and not in the viscinity of the 50 ohm. thats the reason for qrp  i could not get this lamp lighted.

v= i * r, v-volts, i, currents, r - resistance,
w=i *v

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