CW has a new Buddy

There are quite a few basic apps out there for basic logging with rig control and CW keying, as there should be. No two ops are the same, nor should they be.

So I tried a few then realized, as usual, that I might as well make my own.

After working some with the Arduino Uno investigating the RTTY potential it became obvious that the platform should make a decent keyer, if not just for PC interface then maybe even with a paddle hooked into it.

This is nothing new of course, I believe an ARRL book has a recipe for an Arduino keyer and I'm sure there are plenty of them on the air these days.

On the PC side, the idea is to just have a small interface for doing CQ runs for a contest (or just for fun) and have a versatile scheme to configure the exchange and TU/73 at the end of the QSO. Oh, and of course, logging. Since I generally use a spreadsheet for this all I need is to write to a CSV file upon completing a QSO.

So the Arduino has two jobs,

• Accept input from the host PC
• Accept input from a key paddle

And then key the rig through the key jack.

Once again we turn to the Qt platform for a desktop kit app. The parameter names are all ADIF standard (MYCALL, STX, etc) and are tagged by [brackets] whereas any literal strings are, well, literal. So the hailing call can go in as TEST [MYCALL] [MYCALL] or such, the exchange as [CALL] [RST_SENT] [STX] or such, etc. 

One thing to note, the STX field can be set as a static literal (IA, GTA, NLI, etc) or an incremented serial number, just need to set a config file flag. The config file is generated with default values when first run using the Qt QSettings class.

CW Speed is set with the slider and will be remembered in the config file. The speed is sent to the Arduino each time a transmission is sent.

Hit Clear and CQ to send the hail, HALT, as expected, will stop after the next sent character in case you hear some QSK. The ? buttons will send any text in the corresponding box with the ?, or else a bare ? if blank.

The expected workflow is to hit Enter after entering the heard call and that will send the exchange. Once the SRX is recorded hit Enter in that field to write to a log and send the TU line.

 

 The Arduino wiring is pretty basic. For the Uno I used pins 7, 8, and 13 but this can be switched around as needed for different boards. This program is so light it doesn't need anything bigger than the Uno but any of the boards should work, even if a little massaging is required.

Source is available here.

FSK RTTY using CD4046B but still with RS232

About a year ago I put the LM565 modem on the air and have had success in several events since while still pursuing a solution that uses the newer/CMOS CD4046B PLL chip and preferably Arduino instead of RS232.

While pursuing a solution that is more 21st-century than the TTL-based (and mostly retired) LM565 circuit I was getting hung up on the tendency for Arduino communication to be geared toward higher speeds (>9600 baud) while forsaking lower ones (below 300 baud). This limitation is understandable since the need for such a low serial rate is an anomaly these days save for a few legacy equipment situations such as this.

The learning curve over this has shed light on the fact that the USB communication with the Arduino must be at least 9600 before ASCII text will pass correctly between it and anything on the host side. Another limitation, even when using an Arduino Mega board, each of the hardware serial ports can only go as low as 245 baud, evidently a limitation from the standard 16MHz system clock. Software serial is going to be the answer to this, it goes as low as you want, just need to adapt it to 5 bits at some point.

I had gotten partial decode with the 4046 using RS232 and running on a 13.8V bus, but then switched to Arduino and its 5V bus to see what I would get, and due to the challenges mentioned, got nowhere.

So after resetting to the 13V/RS232 scheme it didn't take long to get a partial decode, and then by experimenting with different C1/R1-R2 combinations we arrived at a perfect decode of some recorded RTTY (part if it is fldigi-generated text and then some W1AW bulletins recorded off air).

So at this point I have a slightly updated modem that does exactly the same thing as the previous design. I believe the earliest signs of decoding were with the 4046's Comparator II which is more geared toward clean, locally-generated signals, tried as a hail-mary. But the final answer, not surprising, is Comparator I which is geared toward high signal rejection which is crucial when you need it to lock onto the tuned signal.

Working with the LM565 version has shown that its sensitivity is lacking when the signal is marginal, especially when running the rig's decoder which seems to lock onto anything the ear can detect. That got me to thinking that a preamp might be prudent, as the 4046 spec says it will accept either an AC signal or a biased signal with swing as large as the supply voltage.

I had been thinking that biased amps were very complex, but that's only true of biased filters. Didn't take long to find a paper from an MIT course that spells out a simple biasing op amp that can have variable gain, and best of all, I can use all standard components to get it tuned properly to the standard 2125/2295 Hz range. For the prototype I had to estimate the capacitors but that didn't seem to matter. I also had guessed that ~6x gain would suffice and not overload the 4046, but I quickly realized that the 4046 still decodes fine when overloaded with a clipped signal. 

And so, I ended up with a 1 meg pot that can produce up to 100x gain. Didn't take long to determine that this brings the sensitivity on par with the rig's decoder. This means a lot of junk characters and such hitting the screen, but isn't that better than nothing at all? I am just thankful that it's not eating up paper as in the good old days.

Much of the circuit is essentially held over from the LM565 version, there's still the filter stage that leads into the op-amp comparator that in turn feeds the TTL drive circuit. One quirk is adding a jumper between the serial's TX to the TTL interface circuit, as it was originally designed. For some reason that was omitted before and I'm frankly not sure how it worked without it. Oh well. 

I am also going to switch to CMOS op amps to replace the 741s, more modernization that will run with less current. Not that the rig's 1-amp supply suffers when powering the older TTL chips, good to be as efficient as possible. Was going to add a power LED just to help knowing that all is alive and well once things are wrapped in a box...nahhh.

At this point we have a wonderfully successful proof of concept that is worth wiring up, even at the prospect of getting the Arduino version into play, this will make a great backup unit if ever needed. At this point I'm tempted to think the immediacy of a hardware serial port is always  going to be ideal, but time will tell.

Trying to keep the gain pot at a place where the input doesn't clip going into the 4046, but the 4046 doesn't care, this is while copying W1AW bulletin and the idea is to keep the input just at the supply swing (or a little less) to test copy off the air to see how it does when the band ebbs and tides.

This captures the shifting between mark and space (2125/2295 - yes I have an ancient scope and love it, have yet to try one of the new USB ones):

Once again the SerialRTTY terminal captures it all:

In the end it seemed best to not bother using a pot for the gain and just fix at 100x with a 1 meg feedback resistor and be done with it. If I want to clamp off the RX stream momentarily it's easy enough to just kill the AF gain on the rig.

Another adventure was working through the TL072 in the soldered version without having tested it in the breadboard version. Not surprisingly there was a bit of learning curve here, but the answer came down to adding in some decoupling caps near the ground of the ICs and then the 10 uF one that the 565 circuit employs - right away this added some stability. After that it came down to just finding the the right timing and filter components for this particular board since we know how certain layouts will add their own capacitance.

I've also given in to adding contest automation and logging to the serialRTTY project, should just be a matter of three input fields below the center bar and most control will be done with Alt-keys.

After working the WAE again recently it's hard to resist the appeal of those QTCs, such a cool aspect that the DARC folks baked in, so we may have to see what can be done to accommodate those as well.

 

Sources:

• MIT Course Paper: MAS.836 Sensor Technologies for Interactive Environments Spring 2011, page 7, retrieved 2020.
• RCA CMOS Integrated Circuits Databook 1983, pp 573-578, retrieved 2020.
  
• CD4046B Phase-Locked Loop: A Versatile BuildingBlock for Micropower Digital and Analog Applications, retrieved 2020.
  

FSK RTTY via Serial Port and in Linux

This is a quest that started a few years ago, more for the technical challenge than for any operational advantage. The goal is to utilize FSK rather than AFSK for TX, and to RX using a hardware modem rather than via a PC sound card. Essentially, just use a rather light terminal mode in an old-school fashion.

Naturally this is not ideal for contesting nor the most effective for general contacts in this day and age. Instead it's just exploring the simplicity of the two-tone FSK scheme. I've recently gotten back into CW and can better appreciate how the simple pulsing of tones is pretty effective even when the band fades. Not as efficient as the newer and well-engineered PSK schemes of course, but the brute force approach still has its charm.

Why not just use the pseudo-FSK with fldigi? Well, I have built the circuit and can report it works very well, and hope to write an entry on that endeavor soon once I get the final version wired up.  Again, this is an exercise in letting the hardware do most of the radio interfacing and so the software just needs to handle the Baudot translation and be intuitive to work with, maybe do some simple logging to a file from which to skim what's needed for QSO logging later on.

Another part of the goal is to work in Linux, since my shack operations are all done in Kubuntu, with the exception of a few things I've tried in native Windows when required. Since the termios.h is well documented there are plenty of examples for doing this in C++.

As for the hardware side, this was a bit more of a search. Most of the examples for receiving centered around the use of the DTR pin and software timing, whereas to use hardware timing we would use the RX pin set at the desired rate.

Another challenge is that the newer serial drivers in the Linux kernel have integer params and not floating-point, and so we can't specify a decimal for the baud rate (i.e. 45.45). But since transmitting FSK from a serial port only requires a transistor switch, I set up a test for this and was able to decode perfect copy when transmitting via dummy load and decoding from a different transceiver with fldigi, specifically, with the serial port set to either 45 or 46 bps. This was quite encouraging.

At this point I had spent not a few evenings sending text back and forth through a serial port using Baudot, serial port set at 5 bits, etc. Only recently did I start using a port emulator (tty0tty, akin to com0com for Windows) for such testing, but it was good to verify that the interface to the hardware was all in line.

On to the receive hardware, for which I had originally tried using a tone decoder, to little success. But eventually I came across the spec sheet for the LM565 PLL, which I remembered from Radio Shack catalogs growing up as usable for an FM tuner (along with trying to convince Dad that it was possible to do that without a varicap, miss those days).

It didn't take long to figure out that the 565 had recently gone out of mainstream production, is only available in a new pressing from hobbyist-friendly NTE, or NOS here and there for about the same price as NTE, or else...yeah, from the far east with questionable authenticity or quality. Given the experimental nature of all this I decided to roll the dice and grab 4 chips for about the price of one of the other choices. My experience was that even the counterfeits would work well enough for proof of concept, and that's what I'm after, for now.

So the chips arrived and I went to work breadboarding a circuit, testing the decode with an LED pulse that looked like RTTY pulses - HUZZAH. But then, getting the signal to read pure text in my test program was another matter. At best I would get some of the first characters then garble. It sort of looked like the timing was wrong, but then, I wasn't sure that it was pulling the RX voltage below zero, there wasn't a strong bias "south of the border" so it was questionable as to whether it was really triggering the pin. Also, I was beginning to wonder whether the National Semiconductor sample circuit was compatible with a serial port, being designed to hit a printer head magnet.

All this came about at a time when I was packing up for a move and life change, so it got shelved. Somehow I never took apart the prototype, and recently decided to give it another go. In the interim three years, Arduino boards have come about. Originally it was very clear that this concept won't work with a USB serial dongle, as these typically just don't work below 300 bauds, and why should they? A quick google indicates folks are doing RTTY/FSK already with an Aduino board, but still I'd like to take this as far as possible on the original vector using standard RS-232.

What I discovered recently is that all I needed is to

a) Emulate the voltage comparitor circuit using a 741 op amp
b) Find a very standard darlington-ish circuit for TTL/RS232 interface AND mind the polarity on the 1 μF electrolytic capacitor that has the poles reversed, that seems to provide the proper negative bias, and
c) Correct a capacitor value in the original 565 circuit,

Also, for the TX and FSK lines to the rig I had originally wanted to use optocouplers, but It appears there is not enough drive current for these. I didn't really spend a lot of time trying them since NPN transistors are pretty good at this, so we could always revisit if needed.

Once all this came about I was amazed at the accuracy of the receive when using audio generated in fldigi. It's still impressive when feeding it recorded W1AW bulletins (with filtering enabled on the receiver rig).

At this point I have found the recipe that couldn't be found anywhere else, i.e. demod of the FSK and feeding it to the RS232 RX and it works better than I'd hoped for a possibly subpar 565 chip.

I also have the fortune of a working terminal UI coded in the Qt platform, designed in Linux but conceivably usable on any of the Qt-supported environments. It's very basic and intuitive to use, reads the modem info from a config file and if it can open the port it begins receive mode. Then, just hit Enter in the TX box to start transmit and then type. There's a timer that reverts to RX after about 1.5 seconds.

So we have a proof of concept for this. It can be done, and there's other things to explore. Not planning to solder up the 565 version, but rather explore the TI CD4046 chip, which appears to be a similar concept but with a simplified external component selection scheme.

This is how it's wired for an Icom rig, using the 13.8 V bus for power. This hasn't shown to be a problem although we have to bear in mind that the PLL sync frequency is generally tied to the supply voltage.

I should point out that to date I have only had a handful of RTTY contacts, mostly just touch n go DX, but there was one that really sticks out as an impetus for pursuing this. One evening as 20 meters was going long to the west I answered a CQ from Ken, K6SAD in California, he turned out to be a long time aficionado of the mode and was even running a HAL. The entire exchange from 14.085 on the dial is further down.

This endeavor feels like something like a custom kit ride that gets taken for a spin on a nice day, just for kicks.. The traditional RTTY segments of the HF bands usually seem rather quiet during non-contest or event times. Recently when trying CQ using the pseudo-FSK with fldigi I did get a comeback, but then the band was not in the greatest shape so I just caught a wisp, but it was encouraging. 

One important thing to remember is the rig will use the lower sideband for FSK, so try to keep out of the way of the JT/FT folks when selecting a frequency above 3580, 7080, 10142, 14080, etc. 

*****

UPDATE Nov 2019: Have been looking at an Arduino version of this concept using a 4045 PLL since realizing that an Uno with the ATMEGA USB interface handles 45 baud serial.

Also ended up taking this on the air (in breadbord form) and made 33 contacts during a weekend contest - learned a LOT and it was rigorous fun. Just now getting this soldered up and will use that good breadboard to work on the Arduino/4046 concept.

*****

CQ CQ DE K6SAD K6SAD K6SAD

CQ C  CQ CQ CQ CQ CQ CQ CQ CQ CQ CQ CQ CQ DE K6SAD K6SAD K6SAD

KK

LZ

K6SAD DE N8VWY N8VWY N8VWY K

YE

N8VWY DE K6SAD. TKS FOR THE RETURN. LOOKING FOR A REAL RTTY CONTACT.

NAME HERE IS KEN KEN. LOCATED IN NORTHERN CALIFORNIA. HAVE NOT BEEN ON

HERE FOR SOME TIME AS GOT TIRED OF JUST GETTING BUFFER QUEENS COMING

BACK. BACK TO YOU. N8VWY DE K6SAD KKK

K6SAD DE N8VWY THANX FOR CALL KEN, GOOD TO HAVE A REAL RTTY CONTACT

AS WELL. AM FAIRLY NEW TO GDIGI MODES AND ESPECIALLY RTTY.L   

RST   NAME MIKE MIKE QTH COLUMBUS OH USA LOC EN80 EN80 THAT IS MY BUFFE

R THERE FOR CONVENIENCE. YOUR RST IS 599 599 .BTU KEN K6SAD DE N8VWY

K

SDM

QVKGVN8VWY DE K6SAD; TY ON SOME OF THAT MIKE. YOUR NOT MOVING THE METER

HERE AT ALL. BUT GUESS GOT ABOUT 50 PERCENT PRINT. RUNNING ABOUT P

WATTS HERE TO AN OLD FIVE ELEMENT MONO BANDER THAT SHOULDBE LOOKING

RIGHT AT YOU. USED TO WORK A GROUP ON THIS FREQ BUT LIKE ME THEY ALL

GOT OLD AND SOME NO LONGER HEE AND THE GROUPLJUST IS NOT THERE ANY

LONGER. USED TO CALL IT THE WHITE HAIR FREQ. HI. RIG HERE IS AN ICOM

775 AND DRIVING A DRAKE L7 RIGHT AT THE MOMENT. AND THE RTTYS ALL OLD

HAL GEAR. ALL DEDICATED STUFF. SO THAT IS IT HERE. AND THE HOBBY JUST

IS NOT WLAT T WAS IN THE PAST FOR SURE. I STARTED USING THIS MODE IN

61. 61. SO A EW YEARS BACK. N8VWY DE K6SAD KKK

GBK

B

K6SAD DE N8VWY FB THERE KEN, I HAM USING THE FLDIGI SOFTWARE, IC-756

PRO RUNNING ABOUT 50 W 50 W CURRNENTLY. SEEMS MOST OF THE QSO IS ON

PSK MODE THESE DAYS AND SO ALL I SEE ARE CONTESTERS AND SUCH ON RTTY

MODE, BUT GLAD TO USE SOEMTHING SO CLASSIC. BTU KEN K6SAD DE N8VWY K

N8VY ZZZZZ N8VWY DE K6SAD. OKAY ON MOST OF THAT MIKE. FINE ON THE 50

WATTS. NOT SURE WHAT THE ANTENNA IS. OKAY. JUST GUESS THE BAND IS NOT

THAT GOOD. SO WILL NOT HOLD IT. DO THANK YOU FOR THE CONTACT. FIRST

CONTACT HERE FOR SOME TIME. JUST HAVE NOT BEEN GETTING ON IT. OKAY.

THANKS AGAIN MIKE AND WILL PASS ALONG THE 73ES FOR NOW. N8VWY DE K6SAD

SK SK

K6SAD DE N8VWY FB KEN , BTW SOLID COPY HERE ON ALL THAT, FB ON DEDICATE

D EQUIPMENT. BAND IS IFFY SO WE'LL NOT HOLD IT EITHER. ANTENNA IS END

FED WITH COUNTERPOISE, 85 FEET LONG. THANKS AGAIN AND HOPE TO HEAR YOU

AGAIN, ALL THE BEST,

TX 73 K6SAD DE N8VWY SK

General Musings of a Wire Antenna Junkie

• It's only a bad idea if it doesn't work.
• I use a tuner, not tuned antennas. Camping out on a band then twiddling knobs for a minute never killed anyone.
• 9:1 toroid unun/balun is a miracle worker.
• 85 feet seems to be a magic number for 160-10, sometimes even 6. String it in a tree and load with a 9:1 and some counterpoise. If it doesn't work right try a capacitance hat. If it's worse with the capacitance hat then don't use one.
• 1:1 wound over a bolt can be paired with the 9:1 so the unun is more of a balun as well. evidently this chokes all the bad currents into undisciplined metal, no need to use disciplined metal for this, save it for transformers
• Nothing wrong with a bottom-fed (horizontal) delta loop, they work just fine.
• Always see what Uncle Doug (SK W1FB) has to say
• There are PDFs of golden-age ARRL antenna book online, check there too
• Homemade ladder line is more rugged than i would have imagined
• A 1:1 isolator unun at the feedpoint really does clean up a lot of RF issues with these end-fed antennas. The MFJ-915 has exceeded my expectations, even after winding some common mode chokes around a ring.

 (more to come)

GSC 20A DC Linear Power Supply Redo

This boatanchor was a find at the area radio store, as-is, think I paid 20 bucks for it, a buck per amp. Brought it home and did the usual lookover, found no issues, output was around 14V. Tried it with some VHF mobiles and ended up using it to power 3 at a time for monitoring and could transmit on one at high power with no issues. 

But not surprisingly, since this thing is old school brute-force (completely opposite from modern switching supplies) it just has a huge transformer, two diode rectifier (half-wave), a Zener diode regulator then a classic thee-transistor array to regulate the higher current flows. The transformer is simply bolted to the bottom of the case, the nuts had worked loose enough so it would buzz until i smacked the case. Plus these things tend to run hot, again, they are old school. 

Eventually I took the case apart again to analyze the design. Right away i realized most of the heat was coming from the two ECG5980 40A rectifier diodes mounted on a sheet of aluminum. This got me thinking how a full-wave would be nice to try in there, and make at least that part more efficient. The ripple tanks had been replaced from the original, for which there were still two ring mounts on the base of the cabinet, each measuring 1.5 inches diameter - like finding dinosaur tracks. We all know that vintage capacitors were much bigger than today and didn't age well, so it's not surprising these had been replaced with two 15,000μF axial lead in parallel. I also noticed there was a 510Ω bleeder resistor soldered across the outputs, so someone had done a decent job fixing it up. 

So in taking stock of what this thing offers, we have the dual-secondary coil that is presumably of 360 VA variety across both the windings. We also have the sturdy metal case that could be refinished, and the three TO-3 bays with heatsinks. Plus the main switch still worked fine, as does the fuse holder and rear binding posts. These would be the most expensive parts to start with from scratch, and so this makes it a worthwhile exercise to explore the PS theory I'd always read about. 

The panel light ran from the 120V side, and I believe the exact same lamp is available in the NTE line. But in this day and age there's nothing like the reliability of an LED, as long as the regulation works as it should. Plus, the LED acts as a bleeder circuit and helps indicate when things have gotten closer to steady-state.

For the rectifier I started getting a vision of the full-wave made of single diodes mounted on a breadbord that could be bolted to the case. Since this is dual-winding we'd go with parallel rectifiers, research shows nothing wrong with this. Quickly found the 10A diodes that would be decent to work with. 

As for the new ripple tanks, this part involved some of the biggest learning curve. I noted that my switching supply just had low capacitance and grounded two series ones at the middle, so that is what we tried first. Also at first I stuck with the original 15V Zener diode and replaced the original 270Ω 3W resistors with metal film equivalents, but wasn't seeing the regulation kick in. 

So I made a small breadbord tester with a 300mA transformer and some 3904 transistors, ran lots of tests, and concluded that a 7815 regulator would be the way to go. This would mean that all 3 of the 2N3055 power transistors would be in parallel and help share the current load, whereas in the original Zener circuit the first one sets the bias for the other two. 

But the regulation still did not live up to par, and just recently I got back to researching it. 

Realized it was time to consider high-capacitance for the ripple tanks. According to a couple formulas I found online it should come out to around 60-70,000μF across the regulated output. Well, the highest 25V capacitors I could find within a decent budget are the 22,000μF. (Note they need to be 25V since the regulators produce ~21VDC if memory serves.) Now a lot could be said about how these add up in the final circuit as wired, with all the series and parallel going on, but suffice it to say they seem to pass muster. 

When first test-firing it I noticed the panel LED stayed on quite a while, and realize i should have expected it given the massive boost in storage. Something made me check how much voltage that LED would take. The specs say 13.5 V max, and the nominal output is right around 14.2, so the finishing touch at this point is the 33Ω 1W resistor which brings it down to 13.25V according to my meter. Just to note I would have spec'd a 47Ω for the 2-volt drop @ 0.417mA but didn't have one. 

One also quickly notices the instant gulp as the transformer kicks in and loads up the capacitors, but I don't think it's enough to blow a lot of breakers.

So for the first real test I try it with the IC-706MKII running a packet station. The nominal receive draws 2A and 50W ERP transmit now and then will test the filtering. I let it run this way for almost an hour. The unit understandably got hot, but now it's mostly in the TO-3 units in the back and just a little over the transformer (which no longer buzzes). Granted, this is not a normal scenario, since the 706 at full power will draw 20A and I had never intended to use this PS for an HF rig. 

But, this seems to be a successful test, as I could detect no faltering or AC hum when transmitting at full setting when listening on a separate receiver. 


So, yeah, this can easily go back to being a workhorse PS for things that need bursts above 15A but cruise much lower, and that only need to run occasionally.

----------------------------- 

Update 2021: Gave in and upgraded the transformer to a new Hammond, and just as expected this leaves any remaining heat production to the semiconductors. Also drilled some 1/4" holes in the sides of the lid for a cross breeze and now I can trust it on a fairly shallow shelf below the desk. Could always add a quiet fan but there seems no need, this is what it should be, a no-drama and fairly efficient linear PS that has no qualms powering a 100W rig. 

Astatic D-104 Lollipop Mic Modernization

Objective was to procure an all-vintage D-104 and make it appear to my modern solid-state rig as a modern stock active mic. My first desktop mic was a non-amplified D104 variant that I bought with a 23-channel CB from a friend, and I always loved the design. 

A lot of learned souls have written about these mics and I found a bevy of sage advice, special shout out to K3DAV. 

They boast a clear, strong audio, they just plain look cool, and are an icon of American radio culture.

The restoration was spread out over a year thanks to my own indecision at times and waiting for inspiration to hit...

• The one I found was made to order for about 40 bucks on eBay. Chrome had some pitting but not going for a looker, this is about feel. This had been sitting for years, all original wiring and parts. We can rebuild it. We have the technology. Thankfully it doesn't cost six million dollars.
• First order of bitness is to inspect and clean up,
• Disassemble the barrel section and Deoxit the switch and mic plug contacts
• Remove bottom plate an Deoxit the trimmer pot, Elec/Relay switch, etc
• Exterior - tried some steel wool on the chrome and it took the pits down to spots looks some better, good enough for my shack.
• The original crystal mic elements are known to not age well due to the formulation used back then, but replacements are available for about ten bucks. The one I got is physically smaller than the original, but thanks to some spare foam and speaker grille cloth it fits just fine up there in the ol' crow's nest.

• To make it plug-in ready to a ham rig,
• Replaced the cord - the original is high-quality but for a few bucks it was worth while
• Get an 8-pin plug
• Tap into the DC power supplied by the rig - for Icom this is 8V which is perfect for replacing the 9V battery, after all, what is that 8V there for?
• Add a 33k resistor in series with the audio line going to transceiver, to bring it down from tube-drive to levels consistent with solid state equipment.
• At this point we tested it and found some noise...
• Part of it was crackling in the 5k trimmer pot. Took it apart to find a worn spot in the paint, right where it needed to be set. Found it easiest to just swap around the end connections so the sweep would rest on solid carbon.
• After the trimmer was back in play, found it still had low audio, bad fidelity, and a popping sound. Basically it was like someone talking from the other room while someone near by was drumming on an empty beer can. I think I cleaned the switch contacts once more and took some emery to them to make sure, but that didn't clear it up.
• Finally decided the amp board had to be bad and to rebuild it -
• Subbing a 2N3904 for the original 2SC945, which appears to be a legacy part these days
• Wired on plain breadboard, since that's what I had. Some have made very nice etched boards for this but the redneck way will do just fine, if...
• ...there's a way to mount the board and provide a chassis ground, as the original board does with lugs. At some point realized some 12-guage solid wire would do the trick, just need to drill holes in the board and bend it properly, and avoid cracking the board in the process. The solid wire is in a U-shape with the ends looped for mounting stubbs and the crossbar serving as a ground strip for the circuit.
• Somehow this all came together, and once the new board was in place we are in bitness.

Should note, I don't do a lot of voice mode, mostly digital, but I've gotten some great reports with this mic, even on FM, which doesn't lie. Seems I no longer have to repeat information as often and sure is nice not having to worry about the battery.

Preamp Circuit:

• Note the wire colors are for my particular base, which should be fairly universal but at least useful for reference.
• The 5k variable is the trimmer that's accessible from the bottom. Generally this is just set once then left alone.

Base schematic sticker for this TUG8 stand:

73 de N8WWY