[Lowfer] What receiver do you recommend?

[Steve Dove]

Hi Larry, et al,

Frank did a great job identifying the mixer input transformer as being a weak spot, and 
suggesting a macho replacement;  it does indeed make a big difference.

Further  -  very significant  -  improvement can be made by effectively demolishing the 
progressive-to-LF attenuator/filter on the front-end:  there is a series-tuned trap which 
abacus's out at being on 140kHz and so deserves to die, and very light input coupling 
capacitance.  Here's an excerpt of an e-mail I sent Frank about this at one point, which 
says it all: 

- - - - -
Long ago and far away I did your trifilar mixer input transformer mod, which made a
tremendous difference, of course.  Additionally, removing the 140kHz-ish trap (!) of L26,
C108 and R89 by lifting one leg of the resistor, and bypassing C106/C107 with a 0.1uF
brings an almost embarassment of sensitivity at LF;  external filtering for LF and/or
broadcast becomes necessary.  But frankly, with any size antenna, it was anyway.
- - - - -

As mentioned before,  stability is marginal for QRSS30/60/120, determined by three 
separate crystals.  A bit like hard work sorting all of those out.

All that said, it is a fun little radio, and better value for money as a general-purpose 
receiver than we're used to or probably deserve!

        Cheers,

                Steve


>Actually the RX-320 can be made to be quite sensitive!
>That was my main LOWFER RX before I got the RX-340.
>Here is a link to the AMRAD mod with some pictures of
>the way I did the mod.
>
>http://www.amrad.org/projects/lf/rx/RX320LFMod.pdf
>
>