March 31, 2024. Happy Easter to those who celebrate this day.

What a great day to Binge on Chocolate and experience the pain of that filling that has been leaking. 

I would be in that category with the leaking filling(s) had I not just spent an amount equivalent to one of the fancy new uptown appliance box transceivers on two filling repairs. Well at least I can binge on the Chocolate bunnies without fear of pain.

Regrettably everything appears to have jumped in price including the price of parts. Well not so much the parts as the shipping costs. 

That notably is seen in the eBay treasures. I spotted a nice heathkit DX-20 for about $50 and the shipping was $65. Likely it is a twofer with part being a way to in effect charge a higher price by inflating the shipping and in part by increased shipping costs. Shipping with insurance across the US was about $150 for this jewel and that was three years ago.

6AM on the Left Coast ~ 20M Easter Sunday!

My only hope is the cost of Chocolate Bunnies remains steady although a pound of See's Candies for the XYL to mark this day was $40.

Happy Easter!

73's

Pete N6QW 

March 30, 2024. Chasing a dream!

 One of my cherished boat anchors!

Since 1967 I have owned about eight SWAN SW-120's and this one I acquired about 14 years ago. For those who don't know, the very first offerings from Swan Engineering were three mono-band transceivers covering the 80, 40 and 20M Bands. 

 

This particular unit appears different from many of the single band Swan units and that is because while not in the 1st group of 10 produced (Gold Face) it was in the early builds and built in Benson, AZ. The Swan Net has a keeper of the S/N's, and I was told this one was built in June of 1961.

 

Noticeable is that later units had a Meter Face over the dial readout and this one has a very expensive Triplet meter. The later units had a less expensive meter and the dial cover and the meter front matched. The final is a 6DQ5 and typically you can get 100 watts on Tune. The Balanced Modulator is a RCA 7360. 

 

[AD4DQ on his QRZ page has photos of his vintage gear. Sitting side by side is a photo of two Swan units with one that looks like mine and the other a later unit.]

 

The radio is operational and of note has a linear dial readout and it tunes from 14.2 to 14.235 MHz USB only. A true Transceiver it uses a unique system of biasing the tubes to cut-off when not being used. Certain tubes are biased OFF in transmit and others OFF in receive. A simple 4 Pole DT relay does it all. 

The IF is 5.173MHz and the VFO is at 9 MHz. This topology was pure Genius as it would result in an instant two band rig with the 5 MHz Filter. The additive sum gives USB on 20M, and the subtractive mix inverts the sideband to give LSB on 80M. By shifting the VFO from 9MHz to 12MHz gives LSB on 40M. This is how it is done on the later SWAN SW-240.

 

The Audio Gain control is really the RF Gain Control. Owner mods include adding an AGC circuit and a padding cap to shift the frequency down to the CW bands. Kind of a Kludge!

 

Herb Johnson the founder of Swan Engineering, later Swan Radio, hand built most of the early production units and the silk screening is kind of crude. Much of the early builds were done in his garage in Benson. 

Keep in mind this was Cycle 19, the hottest sunspot cycle to date for ham radio and the other big advantage was size. The home station might be a Hammarlund HQ180 and a Johnson Invader that combined weighed a ton and needed the whole desktop. The SW-120 was light weight and could fit under the dash of a then modern auto in the space between the dash and transmission hump. Yes, I had one mobile in a Chevy Vega.

 

This jewel cost in the $300 range and when a KWM-2 cost $1250 in 1961 -- the price point made it a winner. Shortly after moving his operations to Oceanside, the Swan 240 hit the market and it had all three bands in one box.

One very interesting design note (among many) is that the Transmitter Pi Network is in the receive chain so on receive if you peak up a signal with the plate and load controls --you are close to the values for transmit.

 

Just for fun I once checked into the 20M Collins Net with the Swan 120. What fun!  

 

This SW-120 was in particularly good cosmetic and electrical shape and remains so today.  Too bad it doesn't tune down to FT-8 as that would be a blast. 

Thus, the SW-120 was indeed chasing a dream: DX operation in the car running 100 watts and a small size. Much later the ICOM IC-706 would be a similar dream chase with an even smaller size, no special power supply, multi-band and noise blanker. 

 

Also in my favorite category are the KWM-1's I have. Herb Johnson went on to found Atlas Radio.

 

73's

Pete N6QW

PS About a year ago I bought a SWAN SW-175 (80M) for $50 and it works, and I had thoughts of converting it to 20M by adding an Arduino and Si5351 and put a color TFT in the dial face. As best as I can tell three or 4 coils plus caps would need changing. Currently on eBay is a SW-140 for $200. That is outside my $50 template.

March 28, 2024. Just another Day at the Office.

 FT-8 with a RPi Zero W

Given the FT-8 achievement maybe even QUISK would work on the RPi Zero W for a really small SDR Transceiver.

But all that glitters is not Gold! The Zero does not work well with Chromium and even Firefox is an issue. So, it is a bare bones device, and you trade off the low cost with low performance. But for FT-8 this will do just FB.

73's
Pete N6QW

March 27, 2024. Dual Gate MOSFETS and Ferrite Cores

 If you dabble with homebrew then most likely at one time you have used a Dual Gate MOSFET (DGM) and Type 43 Ferrite Cores.

Type 43 cores especially the FT 37-43 form the backbone of much of our homebrew gear. They show up as matching transformers or RF Chokes. The Type FT 82-43 can become a 2.5 Millihenry RF Choke with about 70 Turns of #28 enamel wire. 

Amidon is a short distance from my QTH -- about 70 miles but a standard shipping fee of $14 for $12 worth of product is not cost effective. The W8DIZ Kits and Parts is of course a great alternative especially since he is known as the Toroid King. 

But a funny thing showed up on my phone yesterday and that is that Digi-Key sells the Fair-Rite Toroid stock. Don't get too excited they only sell the ferrite side not powered iron. Below is a link to the equivalent FT-37-43 cores and 100 pieces are about 21 cents per unit. 

The Al values are the same so whatever turns are specified in the design will work with these Fair-Rite cores. Thus, a Ferrite Toroid lot can be an add on to any Digi-Key order and the shipping is much better.

Fair-Rite FT-37-43

One of the most frequently used DGM's in designs of old was the RCA 40673. Alas no longer made and a Surface Mount rival the BF991 also no longer made. Before you dash off an email about BF998's still being made -- that is true and can be purchased "Mounted" from www.mostlydiyrf.com. The one difference is the BF991 can operate with 20Volts Vdd but the BF998 has a 12Volt Vdd limit. 

An alternative to the 40673 is to connect two J310's with the Source of one J310 connected to the Drain of the second J31o. This LINK features a N6QW Direct Conversion Receiver using the J310's c0nnected as a DGM. 

The J310's are employed as DGM's in three areas in the above photo: the RF Amp stage upper LH corner, two in the IF Module (center) and one in the Product Detector lower middle.

BTW that IF Module was converted into a steerable IF Module shown in yesterday's posting.

So why even consider a DGM -- the all important Gate #2. The Bias setting on Gate #2 can control the stage gain. In one transceiver build I have the stage gain set with an AGC circuit on Receive and with a small relay switches over to a fixed bias on transmit. Look for the blinking LED's showing the AGC Action on Receive. (Yes, this is a work of Art! WYKSYCDS.)

Those are your two Tech Tips for today.

73's

Pete N6QW

March 26, 2024. Old boards that may become rigs.

I have boxes of boards that didn't quite make the grade and I now find since I have little time to build new, this is a perfect time to fix some of those boards. It is all there -- they just don't work.

Here is a case of a candidate board where I tried to skate by with a 4-pole homebrew crystal filter and it had a few hiccups. This is a ripe selection.

 

A Board that might become a Rig.

So, what really happens with a filter of less than 5 or 6 crystals. Ten Tec sold the early Triton I and II radios with 4 pole filters and early on KVG made a 5 pole and 8 pole 9MHz filters. [I can really tell my Triton II only has a four-pole filter. The Triton IV has an 8-pole filter.]

The 1st problem is that the lesser pole filters likely have a shape factor such that the skirts are not approaching vertical but more like gently rolling hills. 

 

A plot from my Nano VNA (one of two) -- more poles would give you skirts that would have a greater depth of null before flaring out. The pass band ripple isn't too shabby, but the broader skirts mean adjacent channels will be heard. 

 

The filter is not symmetrical and favors LSB (right side) as that skirt is more vertical than the left-hand side (USB). Will it work -- yes. Will you get reports of being wide or distorted -- most definitely! But hey you are making contacts with a marginal 4 pole Crystal Filter.

Placing the LO above the Crystal Filter frequency would cause sideband inversion and now that more vertical right side could be used for USB.

The board itself has a steerable module (2 Relays), an ADE-1 (PD/BM), and SBL-1 (Rx/TX Mixer), the 4-pole 4.9512MHz Filter (SMD Caps backside) and two DGM's fashioned from pairs of J310's with a tuned tank, and an on-board BFO with two SMD 2N3904's. A couple of trim pots sets the stage gain (Gate #2) of the DGM's. There is input matching to the DGM's.

I have no recollection why this didn't work but am not seeing the Crystal Filter matching transformers. (Must have been liberated for another project.) Or the input match to the DGM's takes care of that issue since the cores are FT-37-43s.

If this were to be fixed for use (FFU) I would remove the BFO board and use the Arduino + Si5351. 

Today's post demonstrates that sometimes old non-working projects possibly can be resurrected and that I do have a Nano VNA useful in looking at filter pass bands plus knowing how to build crystal BFOs.  

While some would look at the plot as having low pass band ripple, I see a filter likely to show its shortcomings on a contest weekend on 20M and the need to have the LO above the filter frequency to take advantage of the LSB slope.

Check your junk box as you just may have a rig awaiting resurrection.

73's

Pete N6QW

March 25, 2024. MMIC Amplifiers

Yet another tool for your tool kit ~ The MMIC (Monolithic Microwave Integrated Circuit) Amplifier. The MMIC amplifiers are simply superb when looking for a module to add 20dB gain to a circuit, are termination insensitive, 50 Ohms in/out and low noise figure and good to 2GHz. 

I first used MMIC amps in a bilateral 20M SSB Transceiver way back in 2010 and while it didn't make the cover of Rolling Stone it did make the cover of QRP Quarterly.

 

By far the biggest hurdle with using MMIC amplifiers is that they are surface mount and really small. They are incompatible with glue down Manhattan pads, Fat Fingers and require steady hands. Careful circuit layout is also a must!

 

 

12 Sq In. and 50% of a SSB Transceiver, A steered module with IF, PD/BM, Rx/Tx Mixer

My AG393-86G MMIC Amplifier

The devices you see above are Tri-Quint AG303-86G's which are now obsolete. BUT Mini-Circuits sells the MAR-6SM+ which is DC to 2GHz, with 20dB gain and a 2.3 dB Noise Figure with an application circuit shown below. For less than $20 you can buy 10 units at Digi-Key.

The MAR-6SM+ operates with 3.5 VDC but the table shows the dropping resistor needed for various voltages. The Mini-Circuit devices draw about 16ma. I used a 1uH choke with the Tri-Quint devices and the caps are 20nF. The supply voltage on my application was 5VDC.

Aside from that 1st project in 2011 I have used MMIC devices in several SSB Transceivers especially where space and performance were a concern.

MMIC's are for the more advanced homebrewer since they are SMD and are way beyond the Ugly or Manhattan style of construction. But then again, their specifications and SMD size suggest a perfect balance for a minimalist yet feature packed radio. 

The MMIC 20M SSB on the Cover of QRP Quarterly!

Yet another tool for your kit.

73's 

Pete N6QW

PS I have been collecting some important topic data. It appears the blog readers are focused on simple project style posts and bypass anything Raspberry Pi or digital communications modes. I got the message!

March 24, 2024. The Medium is the Message

A bit of magic is always a good place to start. With magic, coins appear from nowhere or perhaps with a bit of magic you can make your mother-in-law disappear. Or perhaps a new radio appears on your operating table with no idea how it got there. But as with all magic what appears to be likely is just an illusion.

Yes, your mother-in-law disappearing was just a dream, and she is still there always telling you her daughter could have married a lawyer or doctor.

For instance -- how did this radio get inside a Champagne bottle? Yes, it is a fully functional 40M SSB Transceiver!

 

Or maybe more fundamentally how with but a few hundred milliwatts of power long distance communication is possible? 

 

In the 1970's Marshall McCluhan offered a simple paradigm that the Medium is the Message and a template for the Orange Guy for his political purposes.

But our medium is ham radio and the tied at the hip connection to technology. Our message is that you have to know stuff to be a ham. For instance, you have to know where the "ON" button is for your $5K FLEX Radio and how to find the best deal on a new appliance box. Or better still how to leverage you credit card, so those purchases of expensive offshore rice boxes give you the most cash back. Yes indeed, you do know stuff!

But we really use a technically oriented medium in the conduct of our hobby and so doesn't it make sense that all hams should have some modicum of technical ability other than just contesting or operating.

73's

Pete N6QW

PS The bottle is made out of Lexan Plastic and the bottom comes off!

March 23, 2024. For Less than $20 You can have a ham rig!

 The $20 Radio Transceiver

This is where you must be skeptical and say Too Good To Be True! Likely it is. 

True out here on the left coast that $20 translates into about 3.5 Gallons of Gas and thus not incidental. Perhaps a slightly different metric, One Big Mac Meal with water.

The subject today is metrics and how they relate to our hobby. But first a personal story about unusual metrics. 

In 1984, I was working for McDonnell Douglas and assigned responsibilities as Program Manager to transition the Hughes Helicopters physical plant from Culver City to Mesa, Arizona and to build the new facilities to house all of the manufacturing and administrative operations. 

Routinely I would brief Jack Real the then President of Hughes Helicopters on the project progress. Follow the link to read about an aviation pioneer. 

At my 1st briefing where we discussed buildings sized at 300,000 square feet, he stopped me and asked that when I did future briefings that I convert the building sizes into Jack Real Homes. He gave me the square footage of his home and we would then make the conversion. My staff just didn't understand that Jack Real was a true engineer and was sizing things in a metric that could be understood by him. 

Other notable points -- he always referred to Howard Hughes as Mr. Hughes and offered that those who really knew Howard Hughes never called him Howard. In case you are wondering yes, the Culver City plant did indeed have an apartment where Howard Hughes would stash his girlfriend's. 

So, to our metrics. Critically we are always interested in power like how much power output and how much power input and often we see the term dBm. That is a measure that relates the power gain as referenced to 1 milliwatt. If you see a rating of 30dBm that is a 1-watt (1000 milliwatts) signal as compared to 1 milliwatt. 10*log(1000/1) = 30dBm. The 1 watt is expressed as milliwatts. Think back to Jack Real and his house size -- same idea.

Easily enough if you had only 0.5 watts that is 1/2 the power or 3dB down and this its value is 27dBm. If you had 2 watts then that is + 3dB or 33dBm. Five watts is 37dBm. Lest we forget 1 milliwatt output is 0dBm. 

You can have negative values of dBm and that occurs for powers less than 1 milliwatt. For instance, if you are seeing 1/10 of a milliwatt that is -10dBm and 1/100 of a milli-watt is -20dBm. 

If your ADE-1 DBM calls for no more than 7dBM of LO Drive, then that my friend means no more than 1.414 Volts PTP. The math: 1.414 Volts PTP into a 50 Ohm load is 5 milliwatts. That equates to 7dBm where 10*log(5/1) = 7dBm. If you pump 2 Volts PTP into the ADE-1 that is 10 milliwatts or 10dBM a 3dB increase in power a +3dBm.

So, whether it is Jack Real houses or dBm it is important we understand the reference basis when using our metrics. Alas 1KW is nothing more than a 60dBm signal. That sounds so puny when referenced to dBm.

PS. The Home of the Apache Helicopter is Mesa, Arizona. 

73's

Pete

March 22, 2024. Technology at our doorstep.

It is hard to keep up with the new technology hitting the market and what it can do for our hobby. Regrettably no time at the N6QW Laboratories to really explore all the possibilities but here is one that looks like it can be something useful in the shack.

Over 15 years ago the Raspberry Pi hit the market and at that time was advertised as the full computer the size of a credit card and costing about $35. We are now on the Raspberry Pi5 -- but the $35 price point is significantly higher.

On the other end currently available is a Raspberry Pi Zero W which is half the size of the original R Pi and less than $35 in today's dollars. Grossly speaking the Pi Zero has a faster processor than the original but somewhat limited in the on-board RAM and more like the original R Pi. By the way the Pi Zero W is a wireless version so affords internet connectivity.

One of the very 1st projects I saw using the original R Pi was a beer dispenser that checked your ID before it would dispense the brew. Undoubtedly that Beer Dispenser DIYer was a ham.

But the Pi Zero W has some possibilities for our hobby like remote control of an Antenna Tuner or a Digital SWR Bridge. How about the guts of an I/Q SDR transceiver? A DDC SDR might be more of a challenge.  One current you tube video shows the Pi Zero W displaying You Tube Videos on a 40-year-old Commodore computer.

But there are always issues and the Pi Zero W has limited I/O capabilities and so you would need to tack a powered USB Hub on that jewel which now makes it physically larger. The other problem to fully explore its capabilities is the software availability for specific projects. Thus, you likely would have to learn Python or Micro-python to get the full bang from your buck. 

So OK time to retreat back to your comfort zone and I didn't even mention using the Pi Zero W to control the slug in your Glue Stick Analog PTO. It could count the turns and give you a readout of the turns and a conversion matrix of turns versus frequency. There are very small stepper motors that could easily interface the Pi Zero W with the Glue Stick. Oh well, too hard.

73's

Pete N6QW

March 21, 2024. March Madness... Electronics not Basketball.

If Brackets (or Analog VFO's) is not your thing, then today something for a weekend project. Another Swiss Army Knife is the 2N3904 NPN transistor. This device shows up everywhere and anywhere literally covering the audio to RF Spectrum. We are not going to showcase that device today!

Instead, we will be sharing something about its twin complementary PNP brother the 2N3906, which also can also function from audio to RF. Often the PNP devices are bypassed because the Emitter is the + side and the collector is the ground side. It is tough enough to keep the NPN devices on the straight and narrow now you are switching pins. 

The two devices (2N3904 and 2N3906) are almost equivalent in specifications as to the Ft and device dissipation. The tricky part is how to use both the devices in the same circuit.

I have often mentioned the Plessey Bilateral amplifier circuit. For the anal-retentive blog readers, it is described in EMRFD, so it is OK to talk about it. I find it noteworthy that many US homebrewer's look with skepticism at any circuit until you say what seems to be the magic decoder ring words "found in Bitx or EMRFD".

The genesis of today's circuit comes from my separating out the 2N3906 device from the Plessey circuit and putting it to work for me. By design I simulated the circuit first in LT Spice and then used it in one of my more popular articles, the MC1496 Direct Conversion Receiver in SPRAT 187. For this application it was the RF Amplifier stage following the Band Pass Filter. 

Now this is just like using your Nano VNA where you don't calibrate the device and have no clue what you are really seeing. The plot above at first glance seems awful. But from high to low (DC to 50MHz) the gain goes from 14dB to 9dB. The 3dB point is 10 Meters where you have 11dB gain. So a 10dB gain amp at 30MHz is not too bad --- especially for a simple set up with 5 resistors, 4 capacitors and for a device bought in bulk costing 4 cents.

[Special note because if I don't say it, I will get emails... R6 is for simulation purposes and not used in the actual build. ]

3906

I also find it interesting that this DCR has seen a far greater interest in ham homebrewer's outside of the US. Oh, right missing the Bitx or EMRFD magic words. I have a track on this from the requests for the Arduino code to run the DCR. About 70% are from outside the US with the total set being about 200 requests.

The LT Spice simulation has the info, and you can see the plot. This is a handy amp to have for general purpose usage when testing out various circuits. The cost is low, no toriods to wind and no special parts required with the added bonus you can even use the W1REX MePads to build it. 

This is a one and done circuit and takes but a short time to build. It will operate with any voltage between 6 and 12VDC. 

73's

Pete N6QW