The Robyn SB540D AM/SSB Base Station Transceiver.
Serial Number 336
Robyn International Inc.
Rockford Mich.

The Robyn SB540D was Robyn's top of the line AM/SSB scanning Base Station and introduced during the height of the SSB craze on the citizen band...approx 1978 to
1981 It seems that finding one today is a real catch. A
pretty rare find indeed. With a serial number of only 336, I wonder just how many were actually made! Upon unpacking this rather heavy transceiver, the first thing that caught my eye was it's oversized front faceplate and the taller than normal height. The black brushed aluminum front face along with it's woodgrained looking case give this radio a big, rugged, and professional look. Amongst the well laid
out front face is a big bright read LED clock and a jumbo red LED channel readout just to start with.Details of all the features will follow.

In addition to the nice front faceplate, Robyn decided to add "grab handles" to the front of the radio to protect the front and make moving the radio convenient. This addition certainly adds to the rack mount type of look and adds class. Similar to what Sparkomatic did on it's beefy looking CB5100 AM base station. Moving along, another really nice feature is the front firing speaker. The audio circuit of this radio is no dog and puts out plenty of loud/clear sound with room to spare.

Other features:
Green RX indicator.
Red TX indicator
S/RF meter
SWR meter
Power button on the front which shuts power off to the
radio but leaves the clock running and a master AC
power switch on the back panel; great for child
security.
Headphone Jack
6 pin mic connector.
Tone high/low switch
CB/PA switch
Noise Blanker on/off
Internal/External speaker switch
Volume
Squelch NOTE: This squelch performance is in the top
three out of over 100 different radios that I have used. The squelch performance is very smooth, non-popping, and a real pleasure to use. *Special clarifier knob that allows for front panel tuning or the option to pull out on the clarifier knob to go into the "remote tune" mode where clarification
can be done from the microphone itself. (A really cool
feature for it's day).
RF Gain
Mic Gain knob (not too linear on my model). Seems to
go from very low to low to medium to normal in about
3/4 of a turn clockwise. The last 25% of the pot makes
a huge modulation output difference but still within
100% modulation with little or no detected distortion.

AM/LSB/USB switch.

The keypad features the following:
Direct access to memory channels (five memories).
Direct channel input for 1 thru 40 Memory channel scan (scans 5 user programmable memories). memory enter
scan stop auto scan (scans all 40 channels). memory recall
and scan delay for memo scan or auto scan.

Back Panel features include:
Master On/Off AC power switch
AC/DC switch
12vdc jack for 12 volt operation from a battery.
SO-238 antenna connector
External Speaker and PA jacks.

On the air tests proved to be just as good as most of
my other radios. Audio reports were clear and clean
with great punch,and receiving showed good sensitivity
along with typical adjacent channel rejection capabilities by comparison to many other radios of that era.

The instruction manual is two steps above many radios
of it's day. It not only does a reasonable job of explaining functions and controls, but also shows specifications, and surprisingly shows the block diagram, wiring diagram, parts layout of top and bottom boards, and a complete parts list as well.

If I had to boast just one thing about this transceiver, I would have to say that the squelch performance impressed me the most. Of course the whole front panel layout and good overall performance, coupled with leading edge (at the time) scanning and the "clar-o-mic" feature, along with it's
serious/beefy look certainly add overall points to this nice radio as well.

This particular radio came to me completely original
with no modifications whatsoever! Thats how I like my
rigs and this one will make a fine addition to the growing collection of the BIG/RETRO RADIOS OF THE 70s
and 80s.

Thank you for reading. For any further information
about this radio you can contact me at:

w6tod@yahoo.com

Best of 73s to all from "The Harmonicat" KDM-6659
Mojave Desert California. The Gateway to Death Valley!
Channel 19 AM and Channel 37 LSB