[AMRadio] Apache Audio Mods

[LEE BAHR]

I also heard the interstage audio transformer iron core is terrible. 
Antique Electronic Supply sells a replacement interstage audio  transformer 
with much better iron.  It in itself will improve the rigs audio.

Lee, w0vt


Subject: [AMRadio] Apache Audio Mods


> Electric Radio Magazine published two articles on audio mods for the 
> Apache.
>
> In issue # 20, December 1990, Ken Morgan KC5DW reported that the audio 
> bandpass of his stock Apache began to roll off at 1600 Hz and was down by 
> 6 dB at 600 Hz.  On the high frequency end it was down by 3 dB at 3600 Hz. 
> Ken changed C61 and C64, both 510 pf audio coupling capacitors between the 
> first and second and second and third audio stages to 0.0047 mfd units. 
> He then measured the lower frequency 3 dB point to be about 2000 Hz.
>
> In issue # 150, November 2001, Glen Zook K9STH did a similar job.  He 
> replaced C61 and C64 with 0.01 mfd, 400 volt Orange Drop caps and also 
> replaced C60, another audio coupling capacitor between the third audio 
> stage and the clipper, with a 0.01 mfd, 400 volt Orange Drop.  C60 was 
> originally a ceramic capacitor, and Glen preferred to use an Orange Drop. 
> He did not measure the bandpass, but he reported that his modified audio 
> was much more "natural sounding."
>
> I can scan copies of the two articles for anyone who is interested.
>
> Jim, W8KGI
>