[BC] WTEL/WWDB

[brew@theMode.com]

Dave Gardiner wrote:

> That's the price paid for protecting CJBC-860 Toronto. They diplex off
> the CHWO-formerly-CBL-740-tower in Hornby, ON, 25 mi W, I think of
> Toronto. The tower is 183 electical deg. high at 740; at 860 it's about
> 203 deg. high.

Well, the nulls may be required to protect CJBC, but I'm guessing that the
station sounded so bad in the nulls because of poor design of the pattern
and the actual array, at least by today's standards.  I've noticed other 4
and 5 tower inline arrays designed in the late fifties which had sharp,
deep nulls rather than the broad filled in nulls used today.  With today's
cheap computing power engineers can spend more time massaging the array to
the best fit what's required before submitting the design.

And further, with the old Nems-Clarke Antenna Monitors, non-phase
stabilized sampling lines and RF thermocouple meters that aren't as
accurate as today's base current transformers tuning a 4 or more tower
array must have been a bear!  The ones that I've worked on from that era
always had at least a few transmission lines that were poorly matched,
often with more X than R on them!  No wonder it sounded like SSB in the
nulls sometimes with such hi Q networks.

Note that this was in the early seventies, for all I know the phasor and
ATUs have been reworked by now.

Are there any old timers that know how you measured tower base impedance
while the array was operating before the Delta OIB came on the scene?

And I guess you could always adjust an ATU for a flat transmission line
with an SWR type bridge, right?  But without knowing the tower base
impedance how could you calculate the ATU network?  Maybe by matching the
line, with the array at operating parameters, then shutting down,
measuring the ATU network components and calculating the drive point
impedance by working the tee-network formula backwards?

Oh, yeah, I remember seeing some charts in an old IRE publication for
calculating the mutual conductance between towers, too.

Get our the slide rule!!!!

I once saw an Antenna Monitor from about 1950 or so, I think.  You checked
phase between towers by using the Lissajous pattern on the built in
Oscilloscope and reading the angle from the dial!

Actually I haven't worked on a DA in fifteen years, I bet the state of the
art is even that much more advanced today than when I last tuned a DA.

from another Old Codger.....

brew - Bruce Schiller at CBS-TV, NY Master Control Maintenance and WA2ZST