R2 Modifications

by John Seboldt, K0JD, 
Milwaukee, WI

Last update: 3/23/04

The Mods
r2pamp.txt, a lower-noise audio preamp and revised diplexer design by Glen Leinweber, VE3DNL

Glen's complete R2a. I have actually built (and regularly use) the revised audio phase shift network from Glen's article, one which includes trimpots to really get the phasing right on over a band of audio frequencies. It's also optimized for lower noise. Using his suggestion to wind your own audio inductors on potcores, I've also made a three-pole LC highpass filter at about 600 Hz, for tighter CW response. It's switchable back to a single-pole highpass at 300 Hz for voice and casual CW reception.

The SETI League, Inc. Hydrogen Line Receiver Development Photos - this is none other than an R2 receiver, modified for a full 22 kHz audio bandpass. Good for sweeping space for alien intelligence - AND would meet all my wildest hi-fi specs! Kanga even sells a kit version with these mods.

W1AAZ's 850 Hz CW filter - the link has disappeared, I'll check my rig and post details later

A few of my mods to the basic circuit -- quick and dirty tighter bandpass, faster recovery for QSK, a cure for excess popping with keying at high gain.

R2-DSP, the online version of the recent QST article on a DSP for the R2, by Rob Frohne, KL7NA/W7. (Funny: the ham station is all haywired analog, but the very computer I'm using contains a Motorola DSP of the same family as used in the article. It's on my Soundscape Mixtreme professional audio card! Oh well, someday we'll get that ham station digitized...)

The QRP2000 project by G0BBL - something like what I'm aspiring toward, with full DDS generation of both I and Q LO signals and complete microprocessor control.

John's Mugshot

John Seboldt, K0JD, Milwaukee, WI
  • Email to: k0jd at seboldt dot net (not spamfoil - translate to standard e-mail-ese ;-) )
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