BITX Hacks : Improved audio


Jorge Luiz Fenerich
 

    Hi Farhan, I have the same problem but I have low signal on the TX, about 450 mV only then should I increase the emitter resitor? Thank you. Jorge PY2PVT _._


2017-01-31 2:44 GMT-02:00 Ashhar Farhan <farhanbox@...>:

the other thing to do is reduce the rf amp gain. you could try removing or increasing the 10 ohm in the emiiter bypass of the rf amp.
the original bitx was for 20 m where the noise levela were lower and we were riding the cycle 23.
- f

On 31-Jan-2017 3:48 am, "Mike Hoddy" <g0jxx.radio@...> wrote:

I must try that, looks like a simple AGC but every bit helps!


73 de Mike, G0JXX




--
  73 de Jorge PY2PVT
  Campinas SP
  GG67MD


Rahul Srivastava <vu3wjm@...>
 

Hi,

Can also try gain reduction at IF stage instead of connecting agc at audio try connecting the collector of AGC transistor to the base of Q3 in series with  a 10nF-100nF cap..

73's

Rahul VU3WJM..



On Tuesday, 31 January 2017 10:14 AM, Ashhar Farhan <farhanbox@...> wrote:


the other thing to do is reduce the rf amp gain. you could try removing or increasing the 10 ohm in the emiiter bypass of the rf amp.
the original bitx was for 20 m where the noise levela were lower and we were riding the cycle 23.
- f

On 31-Jan-2017 3:48 am, "Mike Hoddy" <g0jxx.radio@...> wrote:
I must try that, looks like a simple AGC but every bit helps!

73 de Mike, G0JXX



Ashhar Farhan
 

the other thing to do is reduce the rf amp gain. you could try removing or increasing the 10 ohm in the emiiter bypass of the rf amp.
the original bitx was for 20 m where the noise levela were lower and we were riding the cycle 23.
- f

On 31-Jan-2017 3:48 am, "Mike Hoddy" <g0jxx.radio@...> wrote:

I must try that, looks like a simple AGC but every bit helps!


73 de Mike, G0JXX


Mike Hoddy
 

I must try that, looks like a simple AGC but every bit helps!


73 de Mike, G0JXX


Mike Hoddy
 

Hi Randy - I took out C113 between Pin1 and Pin 8 of the LM386 and it reduces the overloading, not a lot but enough.  The problem with the LM386 is that its a good general purpose amp but its prone to overloading and its a bit noisy.  I've used them in other rigs and they work OK but I tend to drop the gain and feed an outboard AF amplifier?

73 de Mike, G0JXX


Soundararajan Ra.
 

After Adding AGC  (vk3ye) Audio is much better with out any modification in original Bitx40 v3
soudar vu2rjw

On Sun, Jan 29, 2017 at 10:53 PM, Randy Hall <listk7age@...> wrote:
Mike

Which fix did you implement?

Randy, K7AGE

On Sun, Jan 29, 2017 at 8:37 AM, Mike Hoddy <g0jxx.radio@...> wrote:
Yep, just done that - helps with overloading - thanks guys.




Randy Hall
 

Mike

Which fix did you implement?

Randy, K7AGE

On Sun, Jan 29, 2017 at 8:37 AM, Mike Hoddy <g0jxx.radio@...> wrote:
Yep, just done that - helps with overloading - thanks guys.



Mike Hoddy
 

Yep, just done that - helps with overloading - thanks guys.


 

This mod really makes the audio easier to listen to, it just had way too much gain before. I like the audio now.

Joel Caulkins
KB6QVI

On Nov 11, 2016, at 6:14 PM, Ashhar Farhan farhanbox@... [BITX20] <BITX20@...> wrote:

 


The bitx transceivers have more than necessary gain. The strong signals tend to distort with the lack of AGC. Here is a simple hack to reduce the gain slightly. 

All you do is remove the 1uf capacitor between pins 1 and 8 of the LM386

Don't worry it will not affect the sensitivity of the transceiver at all!

I hope people have seen the handsome bitx40 of Bill in his latest post on the hacks blog!

- f


Ashhar Farhan
 


The bitx transceivers have more than necessary gain. The strong signals tend to distort with the lack of AGC. Here is a simple hack to reduce the gain slightly. 

All you do is remove the 1uf capacitor between pins 1 and 8 of the LM386

Don't worry it will not affect the sensitivity of the transceiver at all!

I hope people have seen the handsome bitx40 of Bill in his latest post on the hacks blog!

- f