March 8, 2024. When all you have is an old shoe.

With 3D printing some old bugaboos are soon dispelled with delivering a high quality finished looking project.  I don't have a 3D printer, but some blog readers do. Just like I have a CNC, but most hams do not.

So where is this going -- well sometimes all you have is an old shoe and how do you turn what looks like crap into a nice-looking rig suitable for display on your operating desk. That is our journey for today. Lots of photos so you don't have to read much.

The Simple SSB Transceiver came about when I asked myself about how I would design a new rig that was not a warmed over Bitx. Not that there is anything wrong with a Bitx -- it is just I wanted my imprint on the design and the challenge to do it using only 10 devices. I was successful and later on that same challenge to myself was to do it with only 7 devices. That challenge was successful and resulted in the P3ST.

The Simple SSB Transceiver

 

 

 

At this point I should note that the Simple SSB Transceiver was taken up as a Club Project by The Vienna Wireless Society where some 15 units were fabricated. [Now for a bit of irony and a twist of fate. One of the VWS Club members who built this project initially started by building a prototype set of boards. Recently he took those boards and replaced the 9MHz Filter with a homebrew 45MHz, 28kHz wide filter. Then using those prototype boards, he successfully homebrewed a copy of the SBitx, a SDR version of the Bitx. Indeed, a twist of fate.] 

But what was not previously divulged was that the actual rig was built from a bunch of "old shoes" (a metaphor). Basically, I used what I had in the junk box and from the scrap pile.  This also presented some technical challenges beyond the circuits. 

My opinion, but I think the front panel looks pretty cool with the 16X4 Green LCD and the yellow background panel. The ergonomics of my Fat Fingers have been addressed in that the main knob is easily gripped without bumping into other controls. 

I could lead you into thinking this was all by design that required many hours of noodling. Well, the truth is that the front panel was formerly the front panel (cut down) of the 30M CW transceiver previously shown on this blog. (I hated that project.)

The move to the 16X4 LCD was to cover over (by cutting out) some former holes. While I was at it, I added a 2nd VFO to the sketch as I needed something to fill the LCD Screen.

 

Above is the bare front panel and two of the former holes in the panel needed a fill. In the lower right-hand corner, one hole became the home for audio phone jack and the hole to the right of the Microphone jack was filled with a 4-40 bolt and nut --it serves no purpose other than to fill a hole.

An attempt to conserve valuable space behind the panel resulted in mounting the digital electronics behind the LCD. 6-32 aluminum spacers fitted to the LCD mounting holes provided 4 mounting points for a sub-panel to contain the Arduino Uno and Si5351. This conserved a huge amount of horizontal space behind the front panel.

The Plessy Module with ADE-1's

Several Small Assemblies vertically mounted on Angle Stock

Unknown at the time, the above three circuits represented a technical challenge and later I will describe the simple fix. Note the BPF on the right.

The Back Panel ~ Scrap metal from a former rig!

The sides were made from galvanized flashing ~ Home Depot.

To provide a rigid mounting for the front panel I made triangular shaped side panels and the hypotenuse side was "hemmed over" to add stiffness. This galvanized metal about the size of a sheet of paper cost about $1 a sheet at Home Depot and is easily cut with Tin Snips and bent in a vise.

Now to the resolution of the technical problem. If you look in the photo above, you will see a remnant of a price sticker (small piece of sticky paper) on the galvanized metal. Right behind that is the band pass filter seen in an earlier photo with the small three circuit boards. 

When you put the left side panel on the assembly the BPF coils were so close to the galvanized steel that they became de-tuned. Since the board was vertical -- no way to tune the trimmers. About a minute of thought and a return to a "tool of old". I have a set of Greenlee Chassis punches including one that is 1.25 inches in diameter. Boom I cut a perfect round hole in the side panel and now with that hole could have access to the trimmers. Simple solution!

The Driver and Final Boards Fill the Back Panel.

Just to round things out, the Microphone amp and the Audio amp were small circuit boards vertically mounted on a piece of angle stock along the right side of the main Plessey board.

I can say with certainty there were a lot of old shoes used in the project but if you look at the front panel you would never know that much of the physical construction aside from the electronics was nothing but recycled and repurposed stuff. 

Hopefully there was some tribal knowledge tips of use to the blog readers.

73's

Pete N6QW

March 7, 2024. Some Old School Circuits

As a follow on to yesterday's SSB transceiver resurrection here are some details on a couple of circuits from that era of my radio fabrication.

Firstly, I always build in Modules which has several really desirable features. The big plus is troubleshooting, as you can easily isolate a module that has a hiccup. The second, almost as big as the first, is experimentation and upgrading.

 

The first circuit I will soon describe is straight from the LBS (Lets Build Something) project which I co-authored with Ben, AI6YR. The whole thrust of that project was to build a working SSB transceiver that could be undertaken by those new to the hobby. Using readily common parts and a with simplified design, it was aimed at encouraging homebrewing.

 

The LBS which appeared in QRP Quarterly (10 years ago) was undertaken by a radio club in Canada and one of their radios won a prize at FDIM (Four Days In May at Dayton). 

 

Bi-Directional Amplifier using 2N3904's.
 

1/2 The Circuit and this amplifies Left to Right

 

There is a subtlety to this design as the output is always terminated in 50 ohms using a 100 Ohm resistor and a 100 Ohm trim pot in parallel. The output is taken from the wiper on the pot. This provides a means of optimizing the stage gain to the next stage while keeping 50 Ohms as a termination for the amplifier stage. A pair of these are used as the Rx RF Amp stage and Transmit Pre-Driver.

 

Relays controlled by the TR selects the correct amp for receiving or transmitting.

 

I am not a fan of homebrew Double Balanced Mixers (DBM) and the reasons clearly come from anything that gets published by me will likely get undertaken by those new to homebrewing. Often the new builder neglects some key elements that are needed to have a successful DBM. Then the trouble starts.

 

The first issue is the diodes and the need that they be matched. There are published videos by some notable hams that conclude you do not need to match diodes. I disagree and you do need matched diodes! The name itself Double Balanced Mixer connotes balance and that starts with closely matched parts. 

Taking a similar example if you are homebrewing a crystal filter you start by finding a number of crystals that are extremely close in frequency - no successful filter is built by having all of the crystals hundreds of hertz apart in frequency.  

Still another parallel argument for matched diodes is the audio phase shift networks using op-amps. The resistors must be precisely matched to the specified values. Even 0.1% tolerance resistors will not give a precise 90 Degree shift. Using 5% resistors puts you out in left field!

 

The next piece is the physical construction where often parts are tack soldered on glue down Manhattan pads that have no symmetry or balance to the layout. Crossovers and signal leakage are the issues. Double Balanced Mixers result when all aspects are in Balance.

 

Finally, the construction of the Ferrite cores themselves requires a triple trifilar winding that should be evenly spaced around the core. To assure a coupling coefficient of 1, I twist the three wires with about 8 twists per inch. Multi-color wire keeps the wiring straight.

For a little icing on the cake, I include a balance pot and a means (39 Ohm Resistor) to unbalance the DBM for tune up purposes.

 

Above is an Alternate Layout to achieve symmetry and minimize cross over wiring. If you look closely at the photo of the DBM build you will see the Red and Green Wires. This alternative arrangement will facilitate shorter connections to the matched diodes.

 

Again, I dislike the homebrew DBM's not as a component in itself but the fact that new homebrewer's have difficulty building a high-quality unit and then I get emails about your circuit sucks. 

If after homebrewing a DBM you find the carrier suppression sucks then look at matched diodes, physical layout and evenly spaced wiring on your cores using twisted wires.

 

There is a low pass filter so that only audio frequencies pass into or out from the 2nd Ferrite Core. On the side that says AF and Audio In/Out simply connect the output from the Microphone Amp and the Input to the Audio Amp at this point. Only one of these circuits are "ON" at any time thus they can be paralleled. 

The audio filter serves a very important function on transmit to limit the audio frequencies that ultimately gets impressed on your crystal filter. The 2.7kHz filter means just that -- anything above that falls outside the filter pass band.

Next is the IF Module which uses the Plessey Amp circuit. Matching transformers are a must and for those that insist on building their own crystal filters it is important you know the Z in/out of your filter. 

 

If you follow the directions of the various filter software packages you will derive that number and then you need to build matching transformers to match to 50 Ohms for the Plessey amp. The Matching transformers also impact band pass ripple of the homebrew filter -- don't leave them out.

Undoubtedly this is where the excitement builds to try out your $30 Nano VNA. That same matching transformer will be needed for your Nano VNA measurements. For a simple homebrew ladder filter typically, the impedance is usually not less than 100 Ohms nor more than 300 Ohms. 

The transformers in the schematic below are 10 to 1 as it so happens the Filter is a Commercial Filter with a Z in/out of 500 Ohms. 19^2 =361 and 6^2 = 36. Thus 361/36 = 10:1. You can have two separate windings of 19 and 6 turns or a solenoid type winding of 19 turns tapped at the 6th turn. 

 

 Have fun and enjoy.

 

73's

Pete N6QW

March 6, 2024. Back To Radios!

With no time to spend on new builds, I am forced to look at some older radios that worked but not to what I would call my Left Coast Standard. 

This is a twofer project in that I fixed some problems with a radio. When I accidentally found a nice 5 MHz 6 Pole Homebrew Filter, I built but had misplaced, this was the icing. It was now my chance to bring an old radio back to life using a new filter.

The end result is a two-band radio -- 20/40M with USB/LSB Switch Selected and a Tune Function. Nothing like hearing it up close and personal. Not as good sounding as the SDR but quite good.

Main Video

 

FT-8

As with most of my radio builds of this vintage, it uses the Plessey Circuit with a bi-directional amp stage consisting of two identical 2N3904 amps. In transmit, one of the 2N3904's is the transmit Pre-driver and in the other direction the 2nd 2N3904 is the receiver RF Amp stage. A small pot in the emitter of both circuits enables setting individual stage gains consistent with optimum performance.

 

The Microphone amp is a garden variety PNP transistor, and the Audio amp is a healthy NE5534 driving an LM380N (14Pin).  The driver stage is the one out of EMRFD but modified by me and uses the 2N2222A driving a 2N5109. The Final is a standard IRF510 and good for about 6 watts on 40M.

I don't have a BPF or LPF installed for 20M but that is for another day. This radio when built used a large piece of PCB Board as the base and with an appropriate insulator kit is the heat sink for the IRF510. The surface area is about 100 square inches.

 

The Digital LO uses the Arduino Pro-Mini with a custom Si5351A built for me by a ham friend. It is smaller than an Adafruit Breakout Board and only has 4 I2C Pins plus the 3 SMA connectors.

Incidentally, last weekend using the HB SDR with the SB-200 (100 watts) I worked the contest on 40M. My best DX was Japan while also working about four Caribbean stations. I guess my Delta Loop likes the East/West propagation.

It was so nice to be able to break the pile ups with the SDR. I attribute that to plain luck but indeed a very nice sounding SDR radio does get a response.

73's

Pete N6QW 

March 5, 2024. Happy Seabee 82nd Birthday!

Today March 5th will mark the 82nd Anniversary of the founding of the US Navy Seabees! Can Do, their motto, is not simply two words but a concept that the impossible just takes a bit longer to accomplish! So, to all current and former Seabees -- a Very Happy Birthday.

1965 Chu Lai

I am always proud to say I was in the Seabees and believe much of what I do is driven by that Can Do spirit!

Regrettably I personally believe our nation has lost that Can Do spirit. We can't even get a budget approved without cliff edge drama and brinkmanship. 

From afar we must appear no longer as a nation ruled by law but as a nation driven by the rich and powerful special interest groups. We only need to look at SCOTUS and I will stop there. 

No longer is it Can Do but the words Can't Be Done!

AN-PRC47 Our Main Comm Gear at Chu Lai

Solid State, 20Watts SSB/CW and all Collins

73's

Pete N6QW

March 3, 2024. From Whence Cometh Radio Innovation?

When I was an Ensign in the US Navy often, I would get orders that just didn't make sense and I would say (under my breath) "Who in the hell thinks this stuff up?" Often the answer is surprising. As a Lieutenant I was surprised to find out the answer for one order. 

The CO calls me up to his office one day and says to me "Pete, I want you to form a Seabee Band and with the best of the players a small Dance Band?" Aye, Aye Sir!

I did just that as it turned out it was not too hard to find quality musicians as being in the Seabee Band was the alternative to a mount out to South Vietnam.  I found a Chief Petty Officer who played sax in Woody Herman's' band and so we had a key player.

The dance band was also formed, and their debut was opening night at the Port Hueneme Seabee Officer's Club.  That is when I got my answer. It was the CO's wife! It seems the skipper and his wifey were former ball room dancers and she missed that venue to doing some serious dancing. You never know from whence the order comes.

Thus, our subject of where radio innovation starts, and I sat down and prepared this chart.

 

This was an eye opener for me and likely I forgot some manufacturer, but this shows not the coastal guys, but the mid-west has the majority. One or two started in a garage and the rest is history. But that begs the question as to why.

I wondered about a company like Ten Tec who had a start-up in Tennessee (Dolly Parton Country) and formerly produced some high quality and innovative radio products. Having had some personal experience in setting up a manufacturing plant in Melbourne AK, I think I know why. 

The answer is that the workers often came from a farm background where problems were aplenty, and they were the only path to solution. There was no help line or 800 number (which actually is in Indonesia). They had to figure it out -- and they did. I also think it was inherent in their upbringing about being self-sufficient and not giving up. 

Sadly, today most on that chart are gone with only two who remain technical innovators one in the mid-west (FLEX Radio) and a left coaster (Elecraft). I am not certain if Ten Tec is still active under their new ownership so there may be a third. 

In case you wondered this is a Morrow radio receiver from Oregon.

 

In mind, the left / right coast "think tanks" like Stanford, Cal-Tech, Harvard and MIT may have come up with the theory part, but it is the mid-west who turned that theory into radios that even today are in use. (Gulp, my boat anchor stable includes Drake, Collins, Hallicrafters, Swan, Ten Tec, SBE and National.)

73's

Pete N6QW

 

March 2, 2024. Crystal Set Exotica

Some more stuff about Crystal Sets. Either this will further pique your interest or cause a severe case of nausea, vomiting, loss of sex drive and maybe even make you go bald.

Crystal sets are like the Roaring 20's. Their entry onto the scene during the 1920's was exciting, vibrant and downright leading-edge technology. But in 1929 that all came to an abrupt end. For those in their 50's (born in 1970) likely the Roaring 20's and Crystal Sets mean nothing.

Thus, always a good idea to get some "skinny" (a term from my Navy days) about Crystal Sets and as usual Jeff Bezos is your friend. Buy this book through the Solder Smoke Daily News Blog.

There is a Xtal Set Society which promotes the use and advancement of Crystal Sets, and the above book (cheapest one I could find) has projects from that organization.

I have seen some pretty exotic crystal set circuits including lifting a diode bridge rectifier from a power supply and fitting it on to a pine board. Selectivity was an issue with simple tank circuits and some designs included a band pass filter.

This schematic above shows the BPF and two diodes. Driving a loudspeaker directly is a question mark.

Or how about a two coil Crystal Set? Caution La and Ld should not be two widely spaced coils. For this to work they must be closely spaced likely on the same form with a small gap between the windings. Also, of import -- phasing of the windings would be a concern. I do not know the why of the design other than selectivity.

I have reached my gag level and long ago probably yours. But keep in mind simple circuits with few components yet capable of receiving radio signals.

73's

Pete N6QW

March 1, 2024. Crystal Sets and ARC-5 Radios

Without fail, daily at noontime, on 7.204 MHz, the Jefferson Noon Net Convenes. The name Jefferson in itself is an interesting side trip. Long ago there was a group of Californians who wanted to split California in half. The lower half (where all the coastal lefties live) would retain the name California and the upper half, for those of the other persuasion would form a new state called Jefferson. I suspect some of the founders of that movement were also hams. Several years ago a ballot petition initiative was underway to make that happen but it did not go forward.

I split my shift at the Board and Care Facility so that I am home during lunch time. Thus, I usually tune in this net if only to have some connection with ham radio, slim as that is. Today the net is non-political and offers signal reports and takes general information. If you check into the net, you are usually asked to answer the question of the day. 

Within the past week here were two of the questions. 1) Did you ever build a Crystal Set? and 2) What was your first ham rig you put on the air?

The day the Crystal set was the topic of the day I did not check in but in case you wonder what a crystal set is, it looks like this.

For just a handful of us, our very first radio may have been a Crystal Set. Batteries were not included or required.

The schematic is pretty simple with a tuned network (L1 & VC1) connected to an antenna and ground where D1 takes the RF signal from the tank network, rectifies it and sends it to a pair of headphones. 

Don't get too excited as this only works on AM signals as those signals include a carrier for demodulation. Without a BFO this simple setup won't copy SSB or CW. Now if you included two diodes arranged as a product detector plus a BFO it will copy SSB or CW as in a direct conversion receiver.

Now D1 in the early days was a chunk of Galena and it was held in a lead cup like holder and a Catwhisker wire probed the Galena until a "hot spot" was found. At that point you would hear either voices or music. No Batteries required.  

 

Galena Cup
 

Later the D1 was sold as a fixed unit and one of the most popular fixed diodes was from the Philmore Company. Think of a stack of 10 quarters with two screw terminals on top. Later we had the 1N34 Germanium diode for D1. 

Philmore Fixed Crystal Detector from the N2CQR Blog

In our 1st photo it looks like a Toilet Paper Roll wound with many turns of fine wire (#28 or #30). I have doubts about the coil in the photo with the slider wire to form a tuned circuit.  

Real Crystal sets had a Quaker Oats Box instead of the toilet paper roll and you first had to soak the Quaker Oats cardboard cylinder in many coats of Varnish to make it stiff. Next you did a trial run with the slider over the coil to just barely nick the wire. Then with a piece of fine Sandpaper folded over you followed that line to expose the wire BUT you were careful to not go so deep as to have a 1 Turn coil. 

So OK, why the slider? The tank network can be tuned by either varying the capacitor VC1 OR varying the inductor L1. It was cheaper and more easily done by homebrewers to vary the inductor.

 

[Some builds using the Quaker Oats box had the box itself as the enclosure like this one. Note the Catwhisker and Galena Crystal on the top of the box. The Slider is mounted on the rod.]

 

 

If you lived in a remote area, to copy the Broadcast Band you needed lots of wire in the air. If you lived close to a transmitter site, then the antenna was less of an issue.

My dad as a kid built many crystal sets and after WWII when he was home from the war, he built a Crystal set and let me listen to the magic of radio. It was about 1947 and I was like 6. The transistor would have to wait a year before being invented at Bell Labs.  In 1950 we moved from an apartment to a home and then things got serious about building crystal sets with proper antennas. I was fortunate in that KDKA in Pittsburgh, was only 20 Miles from my home and was running 50KW clear channel. I found that by connecting the antenna to my exposed bed spring mattress I could copy KDKA on a set of Brush Headphones. 

Every night I would fall asleep listening to a talk radio program on KDKA (The Ed and Wendy King program).

I was never very successful in perking up the tuning so you could copy other stations in the Pittsburgh area nor turn it into a short-wave Crystal set. One of my ears has a kink in it and that was from laying on the earphones while I slept. In the early 1950's I took my newly built CK722 audio amp and installed that on the crystal set. Hey, my first transistor radio!

A radio using two CK722's

There are many radio enthusiasts who build and/or collect Crystal sets today. Some rare sets fetch thousands of dollars. As with our ham rigs some are pretty crude while others border on works of art.

So, the question for February 29th, was what your 1st ham rig was. I checked in with my Al Fresco SDR rig tickling the SB200 to 100 watts. I gave my call and name and said my 1st rig was a BC454 (80M ARC-5) for a receiver and a 6V6 on a wooden chassis and a single crystal on 3.709MHz for the transmitter. Still have the crystal and note that frequency was in the Novice band in 1959. 

80M ARC-5 Receiver

[I bought my BC-454 (NIB) from Meshna Electronics is Malden MA, for $3.50 and the AC power pack which Sub'd for the dynamotor was$7.5o. A total of $11 bought me something more than a Crystal Set.]

A 6V6 (6L6) Transmitter from QST

The net control said I never heard of either one of those but that was a long time ago -- yes it was, about 65 years ago. Then I said I am using a homebrew SDR transceiver today and I could just imagine the question mark on his face -- a homebrew SDR -- you mean it is not an ICOM IC-7300? In the span of 75 years a journey from Crystal Sets to FT-8 and Homebrew SDR Radios. It sure is fun when you know stuff.

73's

Pete N6QW

 

 PS Forgot to mention that my TR Switch for the 6V6 and the ARC-5 was a DPDT knife switch. More than once I got RF burns on my left hand as I touched a contact on the switch while still transmitting. RF burns turn purple in color and easy to spot.