[IRCA] Audio Switching Network for UltraLights and Others

["John H. Bryant" <bjohnorcas@xxxxxxxxxxxxxx>]

I'd like to recommend a simple device that I built 8 or 9 years ago 
that has been my most useful piece of peripheral equipment. Its three 
switches and four audio output ports (RCA or 1/8" phone jacks) 
mounted in a small box. What this simple circuit does is take two 
monaural audio inputs and puts either signal in both sides of a pair 
of stereo headphones, or it puts one of them in each phone 
simultaneously. The device will also, simultaneously but separately, 
put either signal out to an outboard speaker, if the input will drive 
a speaker. That is it! Sounds simple, but it is a wonderfully useful 
device. Basically, you can listen to one radio at a time, in both 
ears and switch to the other radio instantly.... or you can listen to 
both radios, one in each ear.... and even swap them left-for-right.

I did not design this circuit, but discovered it in a Scandinavian DX 
publication from the 80s. I modified the circuit some, built several 
samples and have been happy as a clam ever since. I cannot live 
without this device doing Trans-oceanic DXing.... checking for 
parallels, watching two stations at a time, DXing on one receiver 
while recording on the other, etc.

The other use that I have found for the device is comparing the 
performance of two different radios. When we go on one of the 
GRayland DXpeditions and there is a new radio present, its fairly 
common to take an audio feed from the new rocket and compare it 
closely to my own current favorite.  I've never found a more accurate 
way to compare the realworld DXing performance of two radios.

I wrote an article on the design of this audio circuit in 2000, with 
pictures that was published widelyand I'm sure it is in the IRCA 
reprints. Its also right down at the bottom of the dxing.info 
equipment page   http://www.dxing.info/equipment/

I'd strongly suggest that you buy the stoutest switches you can get, 
because you'll be flipping them a lot, once you get used to this 
beauty. My cost, even so, was under $20 and that included a 1"x2"x4" 
cast aluminium Bud box.  Construction time was one afternoon or less.

Personally, I'm gonna be UltraDXing with my Eton e1 in one ear and 
the Ultra in the other!

Give this thing a shot.... you'll not be sorry!

John B.
Stillwater, Oklahoma, USA
Rcvrs: WiNRADiO 313e, Eton e1, NRD-535(kiwa-mods)
Antennas: 700' NE/SW mini-Bev, Wellbrook Phased Array (pre-production version)

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