Sunday, January 5, 2014


The resistive bride to detect the vswr is what i am making.  ( I made it but there was not enough power to drive it from my transmitter 27jan2015)

Then may be LC tuner will be used. Lets see.... tried this but did not work for me.

Meanwhile during LL qso, VU2KD suggested just put a two diodes and one vu-meter and tune the antenna for max deflections. Actually this shows the antenna voltage.  May be know something is going into the air.
simple tuning help.
I had the sked and talk about the antenna tuning issue of my qrp tx, cw and dsb with VU3YFD. he suggested the tuning up procedure and we had talk about the strip line, diode, homebrew swr meters. wow ! excerpts on the few words is .... ( will write down later on pls wait)

I was little sad, as i did not have swr meter and i brewed this much and tx not putting up on air. Earlier did not feel need for it ! wow. Searched the net I will sure to tune-up and be on air with this qrp rig, but anyway this is process of re-inventing the wheel , it will help lots other hams also. Theoretical knowledge is one thing and actually putting togather is a different thing. Ya, and this is the step towards it.......

Then i remembered my first rf sniffer probe. It has the similar ckt and tried it man-hattan style. put whatever was on hand and around 1pm put tx and rx on. c1-10pf, c2-33pf , r1-one megaohm,  LED. and did the test with cw and dsb tx. they show the light. next was done put  a capacitor in-between the output of rf amp and antenna and tuned for maximum brightness what i think and in rx also one s point increased. that means it was tuning up...... on daytime i tried this indicator and observed that due to dim light of LED without proper shielding or putting it in small empty bottle it is not possible to see the led light.....

then comes the experimental fsm.
This was the ckt 10 years ago i brewed as RF sniffer. exactly i dont remember but I will reverse engineer it from a old rf probe lying somewhere in my junk box. And when i transmit it went full bright.

when my dsb tx did not work, even the first birdge ckt did not work it was time to retrospect. PA is drawing up the current , dummy load is heating up, receiver is crying loud but does the antenna radiating fully ! FSM is a tool to see the answer in full scale or as bright light.

In first ckt there was false indications due to hand capacitance induced emf. so damped it with few more components and it shows the presence of rf as designed.

c1-10pf, c2-33pf, r1-10k preset,r2- 2k2, r3-470k,r4-10 ohm for overall current limiting. d1-d2 are 1n4148 diodes.

Then cw tx was connected to antenna. I placed this ckt near dipole, LED was full bright.  But with one or two feet apart it went dark. There was not much RF radiating from the antenna. There was not enough umphhh......

Now, i understood why people did not hear me on 14316kc dsb rig.

The antenna fine tuning / matching and one  RF Power Amplifier is needed.
( around Jan2015 made succesffully the single ended RF linearing using the IRF510/IRF840)
(Still ATU has been not made, so this is  pending work, may be later on................)

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