Re: LOW tx output

Soundararajan Ra.
 

Tried for short circuit in the predriver transformer but no luck .
I am getting 1.1. Volt at q13 collector but at center tape suppose to 1.5 instead getting 700 to 800 mv ..1mfd capacitor c134 alright .
Today planning to remove the transformer and rew
ound with new wire and see any raise in power.


On Nov 23, 2016 1:14 AM, "Baruch Atta baruchatta@... [BITX20]" <BITX20@...> wrote:
 

Ashar
Now that you mention it ... " RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor)" ...

I think that I resolved an issue that I was having with my BITX 40 meter version 3.  The receive is great but the transmit was unintelligible.  I set it up with a dummy load on the antenna, shorted out the transmit switch, and put the mike by an AM BC radio (on my favorite station).  Just experimenting, I found a small adjustment to R136 fixed the problem.  

Now, as to the power output, I did see that the BITX was drawing about a half amp at 12 volts (with the famous 'HAAAAALOOOWW!') That's 6 or 7 watts, conforming to the specs.  

I have an oscilloscope, so I will measure the peak to peak tonight.  I can't wait to install the rig in the enclosure!

W3TTT Joe  





On Mon, Nov 21, 2016 at 10:42 PM, Ashhar Farhan farhanbox@... [BITX20] <BITX20@...> wrote:
 

By now a number of builders have reported low output. This seems to be a distinct trouble as opposed to being a one-off report. Let's analyze and fix this.

I would start my asking if anyone who has seen just  2 watts output and has an oscilloscope to report the following while transmitting a loud 'HAAAAALOOOWW!'
1. RF peak to peak at hot end of the R136, (the shiny preset near the driver transistor)
2. RF peak to peak at the R150, the 47 ohms resistor at the gate of IRF510
3. RF peak to peak at the drain of IRF510

let's go from there

- f


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