Tuesday, February 10, 2015

CW TX 14318kc ( second)

Today I promised one old time friend in exchange of the old BC radio to give atleast one 5watt , 14318 kc based CW transmitter. Hope I will be able to put it up within a two week.

It should not pose any problem as all the modules are learn by heart.

Lets hope it works out for him as well as me.... Atleast this way he will be able to be on air and I will good karmic benefit....

Reason I am taking this effort is a very simple he is willing to work CW... I have not mastered the bitx... so not making it...  Now a days peoples prefer the SSB and CW is looked down but I like CW ....So as a bonus will try to make the linear also.....

I have promised what I can make easily. I will make just full ckt... He needs to find the old computer heatsinks with fans....he is also required to do some soldering and cabinet building,  power supply making, antenna, will try to incorporate some sort of antenna tuning indicators... etc... this is a little tough task  ...

1. 28-0-28 V ac, @5amp
2. 12-0-12 volt @3amp
3. Small cooler fan.
4. Antenna & wire.
5. Morse key.
6. Receiver and changeover things..

Here is the picture of that :-

two linears
The two modules shown in the black rectangle is the  small linear amplifier. Marked (1) & (2)...

One friend said after some time it will be boring. Right 100% but this will put you atleast on air easy and low cost. What else you need ?

16 February 2015 :- Today I tested one linear board with crystal oscillator and a tuned buffer amplifier. Wow ! it can directly drive the 5watt lamp with brilliance. Humm power is very high. It can be used as a standalone transmitter without using the after burner. There is no self-oscillations. Feedback is there.

DC current/voltage readings were crazy. Set bias preset it for idle current of 60 mili amp.  On applying the RF and increasing/decreasing ( I had used preset in buffer amp), current reached upto 5 amp. Even on zero gate bias i.e. class-c amp it takes the 1 amp... Too much power.

Need to reduce the gain. Will put one 100 ohm in the tuned amp, buffer amp and also 4k7 accorss the 2n2218 amp.  As I want to use it an Intermediate linear amp to drive a big linear about 15watt.... working on it.... As of made the changes. Now the fan using the LM7805 and side tone, DC /RF indicator LEDs need to be fitted only. Power Amp and DC receiver will take some time. But meanwhile this cw-tx will be ready for its journey....

24 February 2015

With the help of VU3INK, om KISHOR it was tested on air and the report he gave me 579 and 547. Good for  1.7watt RF power with 3 swr. Frequency he tuned was 14314kc.

My Advantage is 33ft high antenna.  Wish my end user reads my blog and follows my tips particulary about antenna. I advise him to use the transformer based well cooled 12@ 3amp power supply only. No smps please.

So, the wheel has been re-invented it will be used by my friend.