improve readability of weak Dx voice signals in SSB noise

Circuit developed by NASA engineers to improve intelligibility of voice communication during Apollo moon shots passes only the three portions of the speech spectrum required for clear speech:300-400 Hz and 2500-3000 Hz for both sexes and 900-1700Hz for males or  1100-1900 Hz for females. Pot ad lusts null to about 600 Hz. Circuit improves readabilhy of weak DX voice signals in noise.

-J. Fisk, Circuits and Techniques, Ham Radio, June 1976, p 48-52

- for best results for pcb pls print 100% size from this link
NASA audio filter
best regards
SU1HZ

   

20m oscillator Design (TXR Oscillator)

Hello, 

from last years ago i try looking to 20m oscillator from little available components with high performance and stable frequency  & can tuned.

so this is my full design & tested . i call it TXR Oscillator Design.
it's take from me  2 weeks to design & more than 70 experiments in other 10 days but hi hi cost me some parts from my electronics junk box!
i build this design and it's great work for me  & i tuned it on 14.290 with 100% perfect results.
but all the ways if your want make some experiments i Recommended by the:
-total C13 ,14   from 350 pf to 370 pf for best optimum output... but check Commercial values ​​are available
-R8 value 1k  
- R9 value from 100 ohm to 10k  .... i hope try 450 or 550 ohm soon
-R7 some friend try change it  for output level

if your have any question i will be happy to help you 

best regards

 

Welcome

Well, as a licensed Ham for some years, I recently decided to get active again and thought my musings may be of interest to others.

This is my first attempt at a blog and it will take me a little while to get all I want up here.

Feel free to stop by often and see what is new.

73

Hassan Zidan . SU1HZ