Re: [IRCA] Quantum Phaser

["Craig Healy" <bubba@xxxxxxxxxxxxxxxxxxxx>]

I had a few minutes tonight to work on the phaser.  In effect, I made a new
one from parts I had or bought.  However, the circuit is the same basic idea
as Gerry's or Dallas Lankford's.

I replaced the antenna level pots with two 1000 ohm conductive plastic ones.
The phase pot is a new 500 ohm conductive plastic.  Both Mini Circuits Labs
transformers were replaced with home-made.  Cores are 1/2" OD toroids
salvaged from a Harris transmitter board.  Probably a 75 or 77 mix.  I used
a six turn primary and 14 turn center tapped secondary.  A cross connected
DPDT switch for 0/180° phasing on one antenna input is used.  The same 560pf
capacitors used on the output of the transformers.

The printed circuit card was not used at all.  Construction was by the dead
bug method. I also used a cast aluminum box I had used for another similar
project.  The only parts I used from the Quantum were the two 560pf caps.
Everything else was new.

Rather than dig into the JFET amplifier circuit, I wound a third transformer
for the output and eliminated it.  14 turns as the primary and four turns
for the secondary on the same 1/2" core type as the other two.  I used an
external DX Engineering RFA-1 preamp to make up the gain.

I brought it out to the truck and hooked it to the cross-azimuth copper tube
loops I use in there.  I was able to phase local WPRO-630 down to where
something else was starting to come up under it.  Also halfway decent
results on a couple other stations.  Only had a few minutes to test, but I
may have more time tomorrow.

The basic circuit seems OK, but there may be some other issue I haven't
found yet.  What I'll probably do is reassemble the Quantum after checking
each part and retest it.  If it works, I'll sell it or use it in a difficult
EAS monitoring location at one of my clients.

Craig Healy
Providence, RI


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