Re: Consolidated Murania Mods

Jim WB2LHP in MI
 

Great news Johnny!

On Sun, Feb 24, 2019 at 10:49 AM Johnny Matlock <jomatlock@...> wrote:
Gm Group
I found a few minutes to implement Jim's mods this  morning.
Excellent results!
The Muriana is now better than ever!
Thanks Jim!
73 Johnny AC0BQ


On Fri, Feb 15, 2019 at 2:53 PM Jim WB2LHP in MI <jmarco1955@...> wrote:
I've been asked to re-post my list of mods to the Murania receiver...This is the updated list with corrections to previous typos...Please feel free to ask any questions...Jim WB2LHP

Detector Gain Control...

FLOAT the wiper lug of R3
Place a jumper between the PADS for the R3 wiper and the high side of R3
Lift the leg of R1 that intersects with R2 and R3
Connect a jumper between the floated leg of R1 and the wiper of R3
 
This allows R3 to control the gain of the detector stage in the TA7642...The audio amp runs wide open...Adjust R3 for the best sounding audio...R3 now acts similar to a regenerative control where there is both volume and gain reaction...
 
Reduced audio distortion...
 
In addition to my previous post regarding the change in use of R3, change R2 from 1K to 2.7K...This biases the output stage of the TA7642 for linear operation...
 
Frequency coverage and dial mapping...
 
Increase L1 from 37 turns to 61 turns...Remove C8...This centers the frequency coverage and makes the dial tracking spot on...
 
Overall Performance...

The Murania now presents with crystal clear audio and sharper tuning...Remember, this is not a superhet receiver...It is a simple TRF front end, detector and audio amplifier...Careful adjustment of the gain and tuning controls will give excellent results...The battery life is excellent...This is my favorite AM BCB receiver...Enjoy!



--
QRP....."More smiles per Watt"
72
JOHNNY AC0BQ  ..


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