Operating and (sometime later) Installing the Nomad Radio Digital Slider in the Browning Golden Eagle Mark III SSB transmitter Copyright 2003 nomadradio.com

Preliminary version 0.11 07/10/2003

So, just what's it good for, you ask? Consider it a 130-Channel external selector for this particular 23-channel transmitter. One crystal gets removed from the radio, and a cable is installed there instead. The cable leads to an external slider. In this case, there is no need for a frequency counter to see your transmitter frequency. The Nomad Radio Digital Slider tunes in 5 kHz steps, two clicks per 10 kHz channel. Dial it up, and there you are, no frequency counter needed. It's worh noting here that the transmitter and the slider have absolutely NO influence on the RECEIVER frequency. None. Zilch. Nada. The Browning receiver is a completely independent, stand-alone unit. The receiver has no idea at all what frequency the transmitter is on. Adding additional tuneable bands to a Browning receiver is a whole 'nother issue that isn't covered here, at all.
The slider powers up at channel one when you first switch it on. Turn the selector ONE (only) click to the right, and you will see:
The LED to the right of the digits indicates that you are 5 kHz ABOVE the channel number. That's right, you went up from channel 1 at 26.965 MHz, up to 26.970 MHz. Click once more to the right, the LED goes off, and the channel number now rolls over to "2". I didn't think you'd need a picture of that. Keep on rolling up past channel 3, and what appears next is the "RC" channel indicated by the letter "A".
The next four RC channels appear where a normal channel selector skips them. The three "two-digit" RC channels, 11A, 15A and 19A won't fit into two digits, so they appear without the left-hand digit "1"
The coverage continues past channel 40, to channel 97 (27.975 MHz). The transmitter is not wide-banded enough to travel that far, but that is where the slider's coverage ends.
Now, if we go back to Channel one, and turn the selector to the LEFT two clicks, it displays one channel below.
This works okay up to nine below, but we run out of digits again at ten below. The Left-Hand LED is lit on all channels below one, so you will know that this is thirteen channels BELOW channel one, and NOT channel 13. The coverage stops at 32 channels below channel 1, 26.645 MHz. That's were the lower channel coverage stops for the average Browning receiver.
So, just exactly what's inside this borrowed PAL cabinet? A filtered 3-prong universal IEC socket on the back panel. That means the power cord is totally generic. Any office-supply store can sell you a replacement computer/monitor power cord. The filter stops any potential RF interference from "sneaking" into the cabinet from the power cord. Above the power socket is a manual-reset circuit breaker. I just don't like one-time fuses. Too easy to defeat with small piece of aluminum foil. Besides the internal power transformer and power switch is a pair of custom-designed printed circuit boards. The front one contains the two LEDs, the two digits and a custom-programmed one-chip computer that runs the show. The selector knob feeds the computer, and it feeds the digits and the rear circuit board, containing the MC145106 PLL chip. You might recongnize that part number from the Browning Mark IVA (NOT the Mark IV) and from nearly every Galaxy/Connex/Superstar radio of the last 15 years. No, it's not a new high-tech chip. It's one that has been in production long enough to be a dependable choice.
This is where the directions should go for installing the slider cable in a Mark III SSB transmitter. Soon. That takes us to the Specifications.....
Technical Performance Specifications
Compatibility: The Browning Mark III SSB transmitter, or any radio that uses "low-side" first Local Oscillator injection with an IF offset of 10.695 MHz. Please note that the output drive level will have to be reduced before using it with a solid-state radio. Excessive drive is bad for a transistor the same as insufficient drive level is bad for a tube.
Output Level: At least 8 Volts peak-to-peak (as measured at V6 pin 9, the oscillator tube grid. Drive level is typically more, but that's what they call an "engineering margin". Compare that to around 2 Volts output for a typical Siltronix analog slider, or about 4 Volts for the Glenn 326-G slider. If the radio contains a "buffer" amplifier in line with the slider cable, it should be removed. Our unit will overdrive a Glen 326-1A buffer amplifier or an equivalent. The Siltronix and Glenn sliders were designed to match typical drive levels for a solid-state radio, NOT a tube-type unit. Ours is designed to drive a tube-type radio. It just takes more.
Coverage: Output Frequency is from 15.950 MHz (at "32 below"), to 17.270 MHz at "96". Output frequency for channel 1 is 16.270 MHz.
Stability: From cold (room temperature) to warmup, drift is under 200 Hz (two-tenths of a kHz). We don't recommend it, but sitting atop a hot tube radio, it may drift as much as 300 Hz. Still not enough to make a difference on AM, and far less than the typical "analog" slider of years past. There's a good chance that your frequency counter drifts more than this much. That brings us to:
The Digital Slider is supplied set to exactly (within 100 Hz) 16.270 MHz at Channel 1. There are two OTHER sets of crystals in a Mark III SSB transmitter. Both of them are mixed with the channel crystal, or in this case the slider output. If either one or both of these internal crystals has drifted with age and use, the radio will transmit off-frequency as a result. You could just rip those crystals out of the radio and install new ones. There's an easier way. If you remove the cover of the Digital Slider, you will see a small trimmer capacitor with screw slot, indicated by the arrow, next to the short little quartz crystal. The screw slot is grounded, so you don't have to use an insulated tool. Just be gentle with it. This takes a screwdriver with a thin blade.
Turn on the slider and select the channel number on the transmitter where the slider cable is installed. Key the transmitter with an external frequency counter in line. Carefully turn the trimmer indicated by the arrow until the counter reads the correct frequency for that channel. If the trimmer goes as far as it can and the transmitter is still off frequency, consider two things: 1) How close is the counter? All frequency counters contain a quartz crystal and a trimmer screw, just like the ones in the slider. If the counter you are using has not been calibrated recently, it's worth checking. One of the easiest ways is to put the counter on a NEW stock 40-channel AM(only) CB (not a "10-meter") radio and see what the counter reads that way. Most legal 40-channel CB radios are within a couple of tenths of a kHz brand-new out of the box. 2) How close did you get to exact channel 'center' frequency? If the error is less than 500 Hz (5 tenths kHz) don't worry about it. Very few AM receivers can tell a frequency error that small. The range of the trimmer capacitor in the Digital Slider is plus or minus 1.5 kHz typically. Very few Mark IIIs that we see are off by more than that much. The big, ugly "X" marks an internal adjustment that you really DON'T need to turn. Trust me. Eventually I should describe the internal alignment for those two slug-tuned cans, but not this week.
Schematic Diagrams
Of course these little thumbnail pictures don't tell you a thing. Click on either one to see the full-size images. They are approximately 200k bytes each. Use the browser's BACK button to return to this page.

Channel Selector/Display schematic

PLL schematic
That's all there is for this preliminary page. What's still missing? Instructions to install a slider cable in the transmitter. Alignment procedures to extend the bandwidth of this 23-channel transmitter, so you don't lose power below 1 and above 23. Pictures and a list of parts that are typically damaged from using a slider with insufficient drive to the radio. Well, it's a start, anyway.