This is the main operating position at W2NBC Radio. The large
transmitter to the right is a WRL Globe King 500B
1956. The construction is modular as in there are three separate racks for VFO
and High voltage , Modulator (with its own supply), and top mounted RF deck.
I have owned this transmitter for over 6 years, and have done extensive audio
modifications to the modulator deck, as well as increasing the plate voltage
to the 811A's to achieve over 100 percent modulation with well rounded audio.
The bandswitching on the VFO has been solid stated, with relays used to pull
up the oscillator coils, making the frequency almost rock-bound steady. An added
reduction drive makes VFO tuning a dream, and I highly recommend it. The transmitter
to the left is a WRL Globe Champion 300-A
. This transmitter
is a real sleeper from World Radio Labs! It is a stoutly built 200 watt output-class
piece, with a pair of rare (and expensive) Amperex AX9909's in the final. Luckily
I have a few pairs of NOS tubes to keep her going for a while. As in almost
all WRL transmitters, the dreaded audio restrictive "couplates" were
removed, and line audio fed directly to the grid of the 6AQ5 driver. The modulator
tubes were changed from a pair of 809's to a pair of 572B's at zero bias. The
mod transformer has also been changed to a UTC unit with MUCH headroom, and
caps were changed out for a total of 250 MFD at 1000 volts. Needless to say
the transmitter sounds great, and it was a pleasure to work on and to operate!
The receiver is a much coveted (by me) but much maligned unit made by Bearcat
. As delivered from the factory in the early 80's, this receiver
was about as insensitive as you could get! The radio was "detuned"
by the manufacturer perhaps to meet some obscure standards of phase noise, etc.
After doing an alignment this is a wonderful radio! The audio and filter selection
are perfect for AM, with 2.7, 6 and 12 KHz widths. The detector output is fed
to an amplifier and speaker setup that will be explained below. The audio chain
has the following components: The microphone is a large capsule condenser type
by Shure model KSM27. Unlike many of the imported mics of the same type, this
mic is designed for continuous service at 48 volts phantom supply. It is a beautifully
balanced mic with incredible low end response. That is powered by and fed into
an Art TPII tube preamp, which has an adjustable input impedance, that really
makes a difference in frequency response. That is then fed to the "glowing
green" lcd panel you can see in the rack, which is a DBX
. This is a pure digital box, with compressor, limiter, EQ, De-Esser
and and the abilty to save favorite programs based on band conditions.The mixer
above that unit is a Shure M367, that is used to feed the Globe King mic output,
and the 300-A line level. The rack gear is powered by a Furman AR-117 line regulator
that does a great job of keeping the AC steady at 117 volts. How do I hear the
great audio from other AMers? With a 200 watt Soundcraftsmen 3 fed by a room
equalized graphic EQ with spectral display, sub-woofer, and 4 speakers that
surround the operating position. The cluster of gear on the desk includes a
digital wattmeter, frequency counter, and line voltage monitor. And the vintage
makes it all come together!