Yaesu Interface Cable SCU-28

 TX Relay, Power and TX REQ IN

R&L Electronics sent me a SCU-28 10-pin DIN cable by accident and were nice enough to let me keep it.  Consider shopping from those guys.  They offer great communication and good prices.

This cable is typically used to wire connections for an external amplifier.  I don't have an external amplifier but I wanted to make use of the +12v power and transmit relay for the protection relay I built for my SDR-Play a few years ago.

I had also read that the TX REQ IN pin could be used to switch the radio into a lower power tune mode for use with external tuners. The absence of a TUNE button for external tuners is one of my pet-peeves about the FT-DX10 so I was excited to have one.

Wiring the Break Out Box and TX-REQ-IN

So I used my last spare plastic project box, some female phono jacks and found a push-button that I'd cut off of some other project in my junk box and went to work.

I used some shrink wrap for the momentary switch for the TX-REQ-IN pin.

I wired up 3 phono jacks... One for the TX relay, another for the +12v out, and one for the ALC control in case I ever do get an amp.  I safed the other wires for future use inside the project box.

Partial Success

I connected the box and verified that I was getting power for the relay and that the Relay Switch operated

Unfortunately, the TX-REQ-IN does NOT do what it does with other Yaesu transceivers.  Pressing the button grounds the TX-REQ-IN - the radio does transmit a carrier in any mode (here I tested with LSB) but rather than transmitted a reduced power carrier as it's supposed to, it just transmits at whatever wattage the mode is currently set to.  In this case I had the power set to 50w into a dummy load and it transmitted the full 50w rather than a reduced power 10w or 20w carrier for tuning.  See the power out on the radio's display

In my opinion Yaesu screwed the pooch on this one.  I don't see any reason why they wouldn't operate like they do with their bigger brethren radios when the TX-REQ-IN is grounded.  Some subsequent forum searching turned up posts from others that confirmed that the FT-DX10 does not properly respond to that signal.

My Elecraft KX3 and Ten-Tec Eagle both have a "TUNE" button that sends a low power tuning signal regardless of what the current power setting is at and there's no reason that the FT-DX10 shouldn't do the same.  Having to dive into a menu to change the power setting for tuning an external matching unit is just silly in this day and age.

I have confirmed that my box is working the relay properly to my SDR-Play.  I reference the relay I built to protect the front-end of the SDR-Play in this post https://www.hamradioqrp.com/2017/02/spruce-up-basic-transceiver-with-sdr.html

That's all for now.

So lower your power and raise your expectations

Rich AA4OO https://www.hamradioqrp.com/

Portable Ops in Comfort

Towable Shack

Working my rolling shack portable station from air-con comfort

We've had a few RV's over the years, but for some reason I've never thought to operate from inside the RV.  I have always tossed a wire over a tree and operated from a picnic table or from my camp chair, as here...

But I thought, "Hey, I have a 12v power supply built-into the RV and the built-in ladder makes a nice solid mount for an antenna mast."

Early try with a military fiberglass pole mast

Now I use a Flagpole Buddy with a 30 foot telescoping mast

Here's a link to the flagpole buddy... link

Our RV has a Converter / Inverter with a spare 25 amp 12v circuit.  I tapped into that and ran a power pole wire to the dinette table.  

The camper had a coax outlet to watch a TV outside the camper... that's obnoxious.  So I cut the cable TV coax and crimped on a UHF connector, and ran that to the dinette table.  I simply attach my coax from outside the camper to cable TV coax adapter to get the antenna connection inside the camper.  Wallah, coax through the wall with no drilling. The cable TV coax run from the dinette to the wall outlet is only a couple feet so it's not really impacting the impedance of the coax run to the antenna.

I've tried a couple of antenna's and have settled on my end-fed 44 foot wire fed with a 9:1 balun and some clip on radials.   I pull the antenna wire through top end of the telescoping mast with kite string, counter-weighted with a heavy sinker.  That keeps the wire taught from the end-fed point up to the top of the mast and out at an angle.

Gone RF fishing with a 30 foot pole and a big sinker.

The Elecraft KX3 and Ten-Tec Eagle will both match a bent spoon with their auto-tuners and have no trouble with the end-fed on 40m and above. 

For a portable key I use my Palm Radio Single paddle.  Either magnetically attached to the steel side of the Eagle or just held with one hand while operating with the KX3.

Palm Radio Single Paddle

On the Eagle the Palm Radio Single magnetically attaches to the side

One thing I find interesting about operating while "camping" (if you call towing a small house to a campground camping) is that I seem to also work a suprising number of other stations that are operating from a campground.

Note the power and antenna connections under the table

The KX3 can stay on the dinette and doesn't take much room.  Keeping the footprint small and the earbuds in, keeps the XYL happy when operating during an outing.

I worked a number of stations on 40m, 30m, 20m and 10m this weekend.  It's always fun to tell a station that you are portable, even if you are essentially operating in your home away from home.

Thats all for now.

Lower your power and raise your expectations

Rich AA4OO HamRadioQRP.com

Benefits of the Yaesu XF-130CN 300 Hz Crystal Roofing Filter

Do You Need That Filter?

The Yaesu FT-DX10 comes standard with a 500 Hz crystal (xtal) roofing filter, but offers an optional 300 Hz roofing filter.  Should you purchase the optional filter?

The 300 Hz roofing filter is twice the size of the 500 Hz filter so it must be twice as good right?  

If you casually switch back and forth between the two filters on a noisy band, it sounds like the 300 Hz filter markedly improves selectivity and quiets the noise.  But try this: Select the 500 Hz filter and narrow the bandwidth (using the bandwidth control) to 300 Hz, then switch to the 300 Hz filter. 

When you digitally narrow the bandwidth of the 500 Hz filter to 300 Hz you will "hear" the same reduction in noise as you have cut out 200 Hz of higher frequency sound.  Engaging the 300 Hz filter lowers the volume a bit (3-6 dB) due to insertion loss.  

So what you are actually "hearing" when you switch back and forth between the filters without changing the digital bandwidth is the reduction of the higher frequency noise that can be accomplished using the bandwidth control alone with the 500 Hz filter.

So, from a selectivity standpointthe 300Hz filter doesn't gain you anything over using the digital filtering with the 500 Hz filter.  The real benefit should come in the form of adjacent signal rejection.  So let's look at that.

In the video below I demonstrate the signal rejection of a 40 dB over S9 adjacent signal to a weaker S3 - S5 signal.

From the video you can hear that there is a very small demonstrable difference in strong signal rejection when using the 300 Hz optional filter, but the difference is so small that I doubt many of us would find practical benefit over simply narrowing the DSP bandwidth while using the 500 Hz filter. Even when contesting.  The digital filtering built into the FT-DX10 is really, really good when using the included 500 Hz roofing filter alone.

Yes, I spent the $200 for the optional filter thinking it would help, but I wished I had known what I do now.  I would have $200 for some other nifty radio gadget to spend instead. 

That's all for now.

Lower your power and raise your expectations

Richard AA4OO

https://www.hamradioqrp.com

Yaesu FT-DX10

Shiny new Rig -- Yaesu FT-DX10

I ordered my FT-DX10 from R&L Electronics this week, along with a 300Hz Yaesu Crystal filter from Ham Radio Outlet, because R&L didn't have the crystal filter in stock.  This is my first order from R&L and I'm happy with their communication and slightly lower prices than the major equipment providers.  They also included an R&L Electronics branded 30A 12v supply for only $40, and I always seem to need a separate power supply.

FT-DX10 next to the KX3

Initial Impressions

It has been over 12 years since I used a Japanese brand transceiver.  Compared to the Elecraft KX3 and Ten-Tec Eagle the FT-DX10 has a higher level of fit and finish.  The case, buttons and switches have a high grade feel.  

I had previously not been able to physically see one of these radios and if I had I may have passed due to the way you physically interact with the radio. The button placement is decidely cramped.  Even though the KX3 and Eagle have significantly smaller front pannels, they both have good spacing between their buttons and knobs compared to the FT-DX10.  All the front panel space used by the FT-DX10's large display definitely reduces the space for physical controls.  

I probably touch the AF/RF knob more than any part of the radio.  It is small.  It is slightly smaller even than the AF/RF knob on the compact KX3, and much smaller than the control knobs on the Eagle.  It's proximity to the VFO has resulted in me accidently moving the VFO off-frequency multiple times.  I would have preferred Yaesu have a smaller VFO knob to make more room for the physical control surface.

Related to the "cramped" controls, I find myself regularly locking the VFO on this radio.  I've never needed to do that on another radio and it's a bit frustrating.  I'm assuming I will become more familiar with the placement and reduce my incidental presses with practice.

In Use

Audio

The audio from the built-in speaker sounds okay on SSB but is very muddy on CW.  I tried playing with some of the EQ controls but I think the large cabinet space under the speaker is just creating a bit of a CW echo chamber at the 450Hz frequency that I like to listen to code at.  CW output at a higher frequency doesn't have the muddy problem but I've developed a painful sensitivity listening CW at higher frequency.  I'm now using an old Vertex mobile speaker on top of the radio and that has cleaned up the CW audio.

Similarly, when using headphones I hear a lot of high frequency hiss even when the audio is turned completely down.  It requires an in-line resistance (outboard volume) or use of higher impedance headphones to eliminate the hiss.  I know a lot of older hams have lost much of their higher frequency hearing but I'm not there yet.

The "sound" of CW from the radio when gain levels are properly managed and the digital noise reduction is employed is quite nice.  It is MUCH better than the audio of the Elecraft KX3 but still not quite as good as the audio from the Ten-Tec Eagle.  The only thing I can say about it is that it sounds less musical than the Eagle.  At some point I will hook up an audio scope to both and compare the audio waveforms.  For now I don't mind listening to it but I haven't had the chance to spend hours listening.

Button mashing

I was concerned about how many times I would have to enter the menu during operation and so far I'm fairly pleased.  There are physical buttons for most of the functions I want to perform during a QSO.   I had considered buying the less expensive FT-710 rather than the DX10; but the MPVD (Multi-Purpose-VFO-Outer-Dial) on the DX10 provide a lot of value by having an additional control ring.  By having both a function knob tied to one of a dozen different functions, as well as being able to assign a function to the MPVD I find that I don't often have to go into the menu.  

Compared to my Ten-Tec Eagle it is easier to operate because the dual-use buttons on the Eagle are perpetually in the wrong mode for me.  Compared to the Elecraft KX3 it is about on-par usability wise.

I wish it had a dedicated knob for power but I understand that I am likely in the minority of people who start nearly every QSO at QRP levels then raise power if needed. Speaking of QRP, 5 watts is as low as the RF power can be set.  The Eagle will go down to one watt and the KX3 will go down to 1/10 watt.  

I am still a little confused about the APF (Audio Peaking Filter) functionality.  The button goes through 2 presses in CW mode and the second press seems to do something different but I'm unsure what that is.  The manual doesn't mention a second press.

The APF is not as effective as the APF on the KX3 at pulling out a weak signal, but the KX3's APF is very strong and makes the signal sound weird.  I don't normally leave it on.  The FT-DX10 APF doesn't negatively impact the sound of the signal but doesn't pull it out as much either.  Mabye there's something else in the menus I haven't seen yet.  

Features

FT-DX10 DNR (Digital Noise Reduction / as opposed to 'Do Not Resuscitate') works very well on CW.  It works much better than the NR (Noise Reduction) on the Eagle or KX3 for CW.  You have to play with the different DNR levels on any particular QSO to find the right match, but once you do it works very well.  I don't think it works as well on SSB as the NR on the Eagle, but blows away the NR on the KX3 on SSB.

The display, ah yes the display.  The display is large and colorful.  I tried using the 3DS (Three Dimension Waterfal) for about 30 minutes and while it is mesmerizing I don't find it as useful as the standard veritical waterfall.  In particular, when there are static crashes the historical 3D waterfall image creates a tall "wall" that makes it very hard to see the signals before and after the static crash.  Since we've had a lot of thunderstorms in the surrounding states (on Thursday evening one storm was producing 443 strikes a minute) it makes that 3D waterful useless.  

The standard waterfall is quite useful although precisely selecting the signal with you finger is very hard, so the mouse needs to be used.  

The internal tuner is matching all the bands on my 80m Windom including 30m which, according to my Elecraft W1 meter is 5:1.  It shouldn't be able to perform a match on that since it's advertised as a 3:1 tuner yet it's working.  YMMV.

The CLAR RX/TX (Clarifier) is what everyone else calls a RIT and it works very well.  When pressed the MPVD ring makes adjustment quick and easy and it both lights up the button as well as has an indication in the display so you don't forget it is engaged.

The ZIN (Zero In) is essentially the same feature as the SPOT function on the KX3 and it works very well to automatically zero beat a CW station.  I think it actually works better than the KX3's SPOT.

I haven't had need to work Split operation with it yet, but it has a button labled TXW which is a momentary button allowing you to listen to the transmit frequency which I think is nicer than having to swap the VFO's back and forth like I do on the Eagle.  However, it's not quite as spiffy as the KX3 allowing you to hear VFO A in one ear of your headphones and VFO B in the other.

As far as standard memories, its operation is a bit disappointing.  My Eagle and KX3 store both VFOA and VFOB frequencies when I save a memory, but the DX10 is only saving the VFOA frequency.  On the other radios I like to quickly jump up to SSB by simply pressing the VFO A/B swap but here I have to store that as a different memory.  That seems like an oversight, so I'm probably doing something wrong.

Nits

My biggest dislikes so far are related to how noisy it is in CW operation.  The T/R (transmit/receive) relay is very noisy.  Not in the same clacky league as the Heathkit HW-101 but still very noisy.  In full QSK it sounds like an old school typewriter in the radio.  My KX3 has silent PIN-Diode switching and the Eagle has a very quiet relay, nearly silent, so to hear the clacking doesn't put me in a happy place.  I've sinced changed my normal full break-in use to semi-break in and lengthened the timeout to 500ms.  I really, don't like that.  I do very conversational CW and like to hear the other station wanting to break-in or hear if I've accidentally infringed on someone.  I feel like I'm keying a repeater.

The other noisy thing is the fan.  The fan comes on even when not transmitting and it's quite noisy.  Compared to the Eagle which has internally baffled fans that you never hear and the KX3 has no fans at all; it creates a much noisier environment.  I wish they'd placed the fan inside the chasis like the Eagle so that it wasn't so loud.  I understand that again I'm in the minority.  Most operators are used to nosiy relays and noisy fans or have an amplifier running that sounds like a Window Air Conditioner, but I'm used to a very quite operating environment.

Headphone use would mitigate both the noisy relay and fan noise but many times I'm just doing casual operating and listening through the external speaker.

It has an "external display" connector to go to an external monitor but the resolution is 800x640.  That's like early 1990s monitor resolution.  Anything bigger than a 15" external monitor results in a great deal of pixelization on the display.  They could have upscaled the display to eliminate the pixelization which would make the external display looks less cheesy.

CW Decode works, sorta.  The radio was advertised as supporting CW decode.  The decoder covers up the waterfall and you have to exit decode to see the waterfall.  I do use CW decode on the KX3 if I'm trying to get a DX station that is sending his call at over 30wpm, and the KX3 displays about 12 characters of information while leaving everything except the VFOB frequency visible.  It's very useful on the KX3 and quite accurate.  The decoder on the FT-DX10 shows paragraphs of decoded CW.  I just want it for a quick assist, not to read 30 minutes of ragchew content from two ops.  The other issue with the DX10 CW decode is that you have to set the CW speed in the menu to match the speed or the accuracy is really poor.  Most decoders just figure it out.  Even the ardruino decoder I built works better. I just wish it displayed a single line in the bottom of the screen.

While we're on CW, it has a CW "memory keyer" function but you have to display the menu and touch the screen to send a CW memory during the QSO.  The memory keyer menu covers up most of the waterfall and going into any other menu function makes the "contest keyer" disappear.  There is a FH-2 keypad that I believe operates without having the menu displayed.  It's a very pricey $100 for a box with buttons connected to different resistance values, so I'll probably build one.  For now I'm using my external memory keyer, which also allowed me to have my manual keys in series with the external keyer output so I can use both mechanical keys and my paddle at the same time.

My KX3 has two key inputs and so does the Eagle, so while I knew the DX10 didn't have two key inputs it is still something I'd miss if I didn't use an external keyer.

Lastly, this is a NIT for me but I can't find anything on the interwebs that says other people have this issue.  I cannot get the radio to reliably interface with OmniRig.  I use OmniRig to interface my radio with Log4OM and other software.  I have searched and searched and others are not having this issue.  I am using the most recent FTDX10.ini configuration file for OmniRig and have it configured with the same serial port settings that work with N1MM (38400, N, 8, 2, Handshake, Low).  It is perplexing.  OmniRig continuously loses connection to the radio.  So this is likely some local PC / software problem I have that I shouldn't blame the radio for.  I even performed a full reset to no avail.

Conclusion

This is the first new HF radio I've ever purchased.  I've been licensed to use HF bands for about 16 years at this point, but I've only owned 6 other HF rigs in that time; all purchased used.  I've owned a number of Yaesu VHF mobile and handheld radios but only one HF and that was the FT-857D.  The FT-857 was a good, portable HF/VHF/UHF radio but due to the limited front panel space and very early DSP implementation was really on the struggle bus when used for HF.

For me this was a very expensive purchase.  So expectations are high.  I knew it was missing some features my other radios already had but I'd hoped the shiny display would make up for it.  At this point it's a mixed bag.  I do like the DNR very much and I can get clean sounding audio out of it using a external speaker, but that's about the only positive.  The clacky T/R relay and noisy fan are a major Debbie Downer at this point.

I know that since I'm primarily a CW operator most of the issues are unique to CW.  If I used Digital modes or did a lot of SSB I'd probably be thrilled with this radio.  If I can figure out the rig interface problems I may try some digitial modes again and maybe it would seem more shiny.   (I know I use the word "Shiny", a lot... It's because there was a Sci-Fi Series on a decade ago called Firefly. The chief engineer used that word for anything she thought was cool or nice... I have sort of adopted it)

I'll give it some more time and see how it works with weak signals.  So far, I've only made a few dozen contacts and less than a dozen extended ragchews due to lots of lightning in my area.  It's really a toss-up at this point as to whether the shiny stuff outweighs the musical audio, and slent operation of my Eagle.

That's all for now.

Lower your power and raise your expectations

73s Richard AA4OO

GAS is Rearing its Ugly Head

 GAS - Gear Aquisition Syndrome

I have some excellent radios.  I have a KX3 that does everything including ironing my pants (well almost) and a Ten-Tec Eagle that has the smoothest CW anyone could ever want.  I also have old crumugeonly radios that require the patience of Job to operate.  I've been well pleased with my collection of RF generating and receiving gear for quite a while.  However, my Eagle is showing its age.  I had to recently replace its T/R relay and the encoders need some cleaning, but it still sounds beautiful.

The problem is these newfangled rigs with their dang, pretty front panels providing information overload with aluring displays of 3D waterfalls and teleporter controls (maybe I mis-read that last one in the specs).  Many of my QSOs now are with operators that have shiny new rigs.  It's just not fair that I'm staring at a segmented LCD display... or in the case of my GRC/9, the front panel equivalent of a Slide Ruler.

The GRC/9 has the operating interface of a Slide Ruler
but wow it's fun to operate... slowly and noisily

The KX3 interfaces wonderfully to my Computer
but it looks dated

Surely ham life must be better when I can gaze at the equivalent of a smart phone on the front panel when using the oldest operating mode known to man?

The Genesis of "Want More"...

In preparation for the upcoming camping season in our RV, I wired a spare 12v 25A circuit in the camper's inverter to bring 12v rig power to the dining table, and co-opted the 75ohm cable running to the cable TV output outside the camper for watching TV (why would anyone watch TV outside the camper).  That cable TV output now takes my antenna connection out of the camper without drilling any holes.  I bought a stellar thing called a "flagpole buddy" to hold my 30 foot telescoping mast on the ladder and wallah, I have a portable Ham shack.  I was using my Ten-Tec Eagle on the dining table, and my wife was not-enthused with having half of the dining table consumed by my bleeping radio. I assured her I'd set it on the seat when not in operation, but I still received "the look".

The magnetic in the Palm Radio Paddle attaches to the side of the Eagle
when operating portable

Flagpole buddy holds the mast extending up to 35 feet

My KX3 would take up less space than the Eagle but it's a pricey little thing to leave in the camper, and I primarily use it now as my primary station in my home shack because it's wired up to the computer using HDSDR to provide a panadapter display. 

I had convinced myself that the KX3 should stay in the Shack. So being the wise and kind husband that I am; I started looking for a small, portable, inexpensive QRO capable radio, given the compromised antenna. All this was to please my wife of course.  

I used to own a Yaesu FT-857 that I kept in my truck, but it was terrible at CW (IMO) and that rig seems to be pretty rare now... After considerable searching I settled on a Yaesu FT-891.  They had good reports and I could separate the face and it would take up very little room on the table.  Plus it had a band-scope of sorts (ah shiny).  But alas, I couldn't find used ones that didn't look like they'd lived under the seat of an off-road vehicle racing in the Baja, and the new ones are out of stock everywhere.  All that web searching kept popping up the rigs with the pretty front panels.  Google decided it needed to serve me advertisements of pretty radios everytime I opened any web site.

GAS

So, I convinced myself that I needed to replace the KX3 in the shack with a shiny, teleporter control rig and permanently install the KX3 in the camper.  I could mount the KXPA100 QRP amp out of the way in the camper and leave the radio in my corner of the table.  I'd also easily be able to take it outside to the picnic table and run off battery.  My mind was made up, I needed the KX3 in the camper and a new shiny toy for the shack.

Reality Strikes

Here's the problem... my KX3 with its 10:1 auto-tuner, silent QSK relay, dual antenna ports (thanks to the KXPA100), built-in IF/IQ output, and dual key inputs (one for paddle and one for manual keys) just can't be found in a shiny, smart-phone panel radio without breaking my bank account.  So I'd have to settle for a "new rig" with fewer features than I've grown accustomed to.  Surely that would disuade me from this folly... but Google keeps serving me advertisements.

I will be soon be writing about my KX3 in the camper and my new, shiny, less-featured shack rig.

Blast you GAS ! 

The Endurance of CW in Amateur Radio

CW Spans a Century

I've enjoyed using my "new" GRC-9 radio for making CW and AM contacts over the past month.  During that time I've also discovered https://worldradiohistory.com/Archive-Radio-News/ which has magazine articles about radio dating back to 1919.  Reading about amateur operators building and using equipment at the time where CW (continuous wave) was beginning to replace spark-gap operation in wireless communication made me consider just how enduring the ability to communicate using CW and AM have been. 

Prior to the introduction of continuous wave transmitters and receivers, the detector used for spark gap communication would have made it difficult to hear a CW transmission (lacking a BFO). So, even though wireless transmission and reception of International Morse Code dates back earlier than 1919; employing CW (continuous wave) to send Morse Code seems to have began its popularity around that time.  AM (amplitude modulation) phone mode was also in use at the time, and grew in popularity during the 40's and 50's until more efficient voice modes overtook it in popularity for voice communication.

Radio Telegrapher School for Enlisted Specialists 1921

What other modes have remained as popular standards using standard ham equipment and continuously in use by amateur radio operators as CW?

My GRC-9 was designed near the end of WW2 (circa 1945), and was in continuous production for various armed forces around the world until around 1974 (3 decades is a long production run).  My particular unit has a receiver manufactured by Telefunken in 1955 and a Lewyt manufactured transmitter from 1966.  I have made CW and AM QSOs with other amateur radio operators whose equipment ranged from home-brew xmtr/rcvrs, Drake and Collins radios as well as shiny new Icom 7300 and Flex radio systems.  

A modern amateur radio (typically a HF model) can be used to communicate with radios built 100 years in the past. The same might be said for AM fone (phone), but that mode has become a niche for a much smaller set of enthusiasts.

There are lots of new and exciting modes of communication in amateur radio.  Many are pushing the boundaries of weak signal reception, or alternatively allow for high transfer rates of data. But it is somehow comforting to me to consider that amateur radio hobbyists have kept one mode in particular, CW, popular and in continuous use for over 100 years using equipment that remains compatible to communicate with one another.  I wonder if that will be the case in another century?

That's all for now, so lower your power and raise your expectations

Richard, AA4OO

Modernizing the DY-88 Power Supply

Go with a Modern Vibe

The DY-88 Power Supply is a marvelous design... for the 1940's.  It could take 3 different DC input voltages (6v, 12v or 24v) and output the 2 different filament voltages (1.5v, 6.3v), plus the low and high B+ voltages (105v, 585v).  It was designed to be as efficient as possible when the radio wasn't in SEND mode (receiver only) by employing a mechanical vibrator and transformer to power the low B+ 105v at about 1 amp current (when running off a 12v input).  

Turning low voltage to high voltage

Prior to the DY-88, I'd restored a 1960's Heathkit HP-13, which was a mobile DC to DC power supply.  It employed a multi-tap transformer and 2 transistors to create the needed low and high B+ voltages for Heathkit radios.  in the case of the HP-13, the two transistors worked in tandem to collapse the magnetic field in the transformer to create high voltage DC, which was rectified and filtered for the radio.

Prior to the DY-88, I'd never heard of, or encountered a mechanical vibrator used in power supplies; so it's been an interesting learning experience for me.   Vibrators were very common up until transistor revolution, for use in mobile applications where 12v needed to be transformed into much higher B+ voltages needed by hollow state equipment.

In oversimplified terms: the vibrator makes DC look like a square wave version of AC which can then be used by a transformer to raise the voltage required by the circuit, then rectified back to DC.  Low voltage DC enters the Vibrator, which contains a relay that makes and breaks contact rapidly, chopping up the DC.  It occurs so fast that the unit "vibrates" or buzzes.

The contacts eventually, become worn and pit making the vibrator less reliable.  Additionally, military vibrators (maybe others) used a rubberized insulator that broke down over time inside the vibrator, releasing a corrosive gas that would further affect the components and essentially, "stick" the contacts on the relay together, making it difficult to get started or completely non-operational.  Depending on how it the contacts "stick" the vibrator can act as a short and unpleasantness ensues.

The vibrators were intended to be disposable devices but they aren't being made anymore.  What to do?

Bad Vibrations

In the case of my DY-88, when I received it the vibrator power supply refused to start but eventually, after a bit of percussive maintenance (banging) and reapplying power it started.  Over the past couple of weeks it usually will start, but there are still occasions where power has to be switched off and on repeatedly to get it to start.  It is obviously entering failure mode.

There is a procedure using an AC light bulb in series with the contacts to attempt to freshen a stubborn one up, but the procedure is hard on the contacts and generally only restores it for a while.  It needs to be replaced, and vibrator power supplies have not been manufactured for many decades.  The NOS vibrators are generally not good due to the breakdown of the materials inside over the decades rendering them bad even if they've never been used.

The solution is to replace the mechanical operation of the vibrator power supply with a solid state equivalent.  

Solid State 

Entering the age of the Jetsons, we have these nifty things called transistors that are excellent and making and breaking contact of DC voltages rapidly and reliably.  I found a number of articles describing a solid state circuit I could build but most did not offer much in the way of circuit protection if a component upstream failed, or if the circuit itself failed.  There are a lot of difficult or un-obtainable components in that DY-88 that I'd rather not have to replace due to the failure of the Vibrator Power Supply.

I read an article by a GRC-9 enthusiast from 2004 (NC6AV) on using a commercial circuit that was designed for this very purpose to replace mechanical vibrators in vintage automobile radios https://www.radionerds.com/images/c/cd/Wire_VBN-1.pdf.  In the article describes the procedure for using a solid state replacement.

I purchased my solid state module from http://dodgem37.com/vibrator-conversion-module/ and ordered some high voltage diodes from antique radio supply to use in the conversion.  I cut apart a non-functional vibrator module to use the phenolic 7-pin base for the VBN-1 module.

Note

The instructions for soldering the VBN-1 module are great with one exception.  From the instructions: 

. . . The pins are numbered 1 to 7, pin 1 is the large diameter pin on the right, and pins are counted clockwise from that pin. . . . 

If you are looking at the base of the vibrator there are 2 large diameter pins.  The instructions say count them from the pin on the right.  That pin will be different if the large diameter pins are at the bottom rather than the top, when looking at the base.  Turn the base such that the two large diameter pins are facing you and located at the top (12 o'clock position).  Now the instructions will be correct.   This may seem minor, but when I first read the instructions I was looking at the two large diameter pins situated in the 6 o'clock position and all the pins were off-by one.

Results

The replacement circuit works a treat, except that I can't hear the faint humming from the DY-88 now when the radio is in Receive mode.  Of course that is immediately obliterated as I turn the radio to SEND and the Dynamotor leaps to noisy life.

Next step would be to JB-weld the can back to the base to restore the look, but I'm debating whether to do that.  I kinda like the look of the modern mixed with vintage vibe (vibe, get it?).

That's all for now,  keeping my heavyweight QRP GRC-9 rig on the air, one repair at a time.

Lower your power and raise your expectations, 

AA4OO