Topband: DXE NCC-1 phasing box

[Rob Atkinson]

Since I started the thread I think I should post a follow up on what I
found regarding the NCC-1 phasing network.  I apologize for the late
post.  The past 24 hours have mostly been spent preparing for and
attending a hamfest.

Firstly the box is working okay; problem solved.  The problem was a
combination of haste, some misunderstanding of the manual, and
possibly a bit of missing information in the manual.  These are great
ingredients for trouble.

Background:  I am on a 50 x 100 foot city lot and need small rx loops
and phasing to reduce or eliminate the worst RFI from plasma TVs, and
other junk.  My 160 m. tx antenna, an inverted L with a 101 radial
ground system is not a good rx antenna, as I'm sure most here
discovered in their salad days.

The loops, Pixel Pro 1Bs need 24 v. dc to run their preamps.  I have a
24 v. supply but it is used to power relays on transmit so I decided
to go with the supplied wall wart dc supplies that accompany the rest
of the antenna for powering the preamps outside via the feedlines.
The T/R supply is dedicated to a homebrew sequencer and my operation
involves separate transmitters and receivers most of the time.  I also
wanted separate independent on/off control of the dc to the antenna
preamps so one could be energized or the other but not both.   All of
this could have been done with the sequencer supply but I figured use
these wall wart supplies and get on with life.

I'll save time by not going through the process--after fooling around
with a clip lead I eventually discovered that the relays in the box
were not getting energized because apparently some DC supply has to be
there for that to happen, either an external antenna preamp supply or
the internal supply (actually the recommended 2A 13.8 v. outboard
supply that powers the NCC1).

I did not want to use the 13.8 v. supply for the antennas so I moved
the jumper to external, but I also did not have an antenna preamp
supply on the rear panel jack that is there for that purpose.  I did
not realize that the jumpers on each rx antenna jack are to
disable/enable dc to the antennas.  I moved them to disable dc, and
with the jumper that switches between the 13.8 supply or an outside
antenna preamp supply back on the "internal" supply, the NCC1 internal
relays operated and the box works FB.

What I missed was that you have to have a supply enabled for the
relays to operate, either the one that powers the box or I guess an
external antenna preamp supply coming in from outside.  If you disable
the 13.8 v. supply for antennas at that jumper, but run the antennas
from sources removed from the phasing box then the LED lights up on
the front panel, you think the box is working, but unbeknownst to you
the internal relays are all in bypass mode and you think something
inside died on you.   I began to suspect this when I put the antenna
supply jumper back on internal (it was the only change I had made),
and used a clip lead to short the T/R jack center to ground and heard
the relays switching.

If I had been using preamps that took 12 v. I would have probably
never run into this because I would have just used the same supply
that runs the NCC1.   I also mistakenly thought the enable/disable
jumpers, one for each antenna A  and B were there to disconnect those
antennas; not block DC to them which the manual was pretty clear
about, and I missed because uh, life is too short for a thorough
reading of manuals?  hi hi.

So, the takeaway is enable the internal supply to the antennas then
disable it at each antenna jack jumper if you are either not using
active antennas or you are using active antennas powered completely
apart from the NCC1.  If you have made it this far without being
confused congratulations.  I wrote it and I need more coffee.

With limited use I can't comment extensively on the NCC1 performance
but after around an hour running it last night I was pleased with the
ease at finding noise nulls.

Tnx for the time and also to everyone who responded to me privately --
I can't reply to each person but I appreciate the advice, tips, and so
on.

73

Rob
K5UJ