The Direct Conversion Receiver -- More
September 7, 2020 ~ GQRP Club Virtual Convention -- some thoughts.
The Covid19 dramatically has changed all of our lives and yet technology has jumped in to take up where normalcy left off. The GQRP Club Virtual Convention is a sterling example of how through the use of Zoom, hams around the world were able to participate in the two day event. High marks for the team that put the event together.
I liken GQRP Convention Central to Mission Control in Houston, much like when the first space ship headed to the Moon. As a presenter I was really concerned how well this would work -- about 5 seconds into my presentation and it was clear -- it was going to work seamlessly --and it did. I think the message is clear when perhaps normalcy returns, future conventions will take form as a hybrid with personal and well as virtual attendance.
But the GQRP club is more than just the annual convention as it is an organization with a publication that fosters low power communication. The SPRAT (the GQRP Publication) is always chock full of articles on homebrew gear, gizmo's and gadgets that are useful in the shack. Many projects range from complete transceivers (Ahem, The Sudden and The Paesano from N6QW) while others might focus on how do I really use my Nano VNA aside from turning it on.
Bill, N2CQR and I frequently will say on the SolderSmoke Podcasts -- if you are not a member of GQRP then YOU ARE WRONG! If not a member join today. Contact the Membership Secretary (Daphne) and join! Even if your interests are not purely QRP, the publication features articles that will catch your eye and interest. GQRP Link
Another bonus is the Club Sales that feature hard to find parts at very reasonable prices and the shipping is fast and shipping cost reasonable.
Join today.
73's
Pete N6QW
September 6, 2020 ~ Time for Wine!
I lived in the Northern California wine country for several years and this is the time of the year known as the CRUSH. This is the time where the grapes are picked and the crushing of the grapes starts the fermentation process. It is quite a frenzied; but exciting time.
That reminds me of my paternal grandfather who in about two weeks hence (near the end of September) would go to the train yard outside of Pittsburgh to purchase a load of grapes to make homebrew wine. You would see all of these quite weathered Italian gentlemen bidding on grape lots while puffing on those wicked and stinky Parodi cigars. After a load was bought, I got to operate his hand cranked crusher (while standing on a box as I was kind of short) and thought this great fun.
For those who really know, making wine is a chemical process where you control the speed of fermentation as well as the brix (sugar) level. At some point when the stars cross the fermentation is stopped and the wine juice is pressed from the grape skins/stems and put into barrels. Once in the barrel the aging process starts and there are different times for the whites and the reds.
My Grandpa Juliano always the anxious one, had his "tribal knowledge" test for when the wine was ready to drink. The barrels had a petcock and Grandpa had a large ladle. Periodically he would sample off the wine in the ladle and the taking a lit match would hold it over the ladle --if it exploded --He would declare it is ready to drink.
Grandpa's wine was awful which I didn't discover until I moved to California in 1963 when I tasted really great wine. Ahh those things we remember.
Don't forget to vote and do it early!
73's
Pete N6QW
September 5, 2020 ~ GQRP Presentation
September 3, 2020 -- Where are we?
This weekend I will be a guest presenter at the GQRP Club Virtual Convention via Zoom. Thus my bench time is limited as I try to arrange my thoughts in some sort of coherent manner. [That alone is a life's challenge!]
I am looking forward to the event and marvel that the technology is at hand where information can be shared around the world in real time. My subject involves "Homebrewing SSB Transceivers" using this specific project below --- The Simple SSB.
But what is apparent today --- it is hard to keep up with the many projects being undertaken world wide. Just yesterday I was made aware of another just released seminal piece of work from the man himself, Wes Hayward, W7ZOI. His effort details how to homebrew 9 MHz Crystal Filters.
What has aided his project are new tools such as the low cost Nano VNA, where once you have built a filter, you can visually see how good or bad is your handiwork. You must do more than plunk four crystals in a circuit and declare victory. There is a process where if it is rigorously followed, a high quality filter can be built. Do Not be misled that it is as simple as walking and chewing gum. RTFM!
As for me personally, I think my days of homebrewing crystal filters are over!
When I think about the time sink to build a really excellent filter I can do the same (FBC -- Faster, Better and Cheaper) using SDR techniques. If you consider the time to characterize crystals and run the Nano VNA plots -- you are at a time trade off with the effort to boot up a Raspberry Pi3 and install SDR Software like QUISK.
In the end with the SDR, you have not a singular bandwidth filter but many filters covering all of the modes. You also never have to fool and fiddle with finding the Cf (Center frequency) so you know where to place the BFO frequencies.
The hardware in a rig employing SDR techniques can be pretty simple consisting of two ADE-1 DBM's in a Direct Conversion Receiver (and Transmitter) configuration. Read that the cost trade off is about even! BTW to build one of the W7ZOI Filters you would need a starter stock of crystals likely in the numbers that equate to the cost of two ADE-1's -- about $10.
But like anything, we do things because of the challenge or like to collect trophies. Do not let me deter any one from homebrewing a W7ZOI Crystal Filter -- I have built many homebrew filters with some being better than others.
That said, I would have chosen 4.9152 MHz versus 9 MHz as the 17M problem goes away. Besides if that frequency was good enough for Wayne and Eric (@Elecraft) there has to be some excellent reasons to use that choice.
With the 4.9152 MHz filter you also place the LO above the IF for image reductions. Likely the choice of 9 MHz is for the afficianado's who still cling to analog VFO's where a 5 MHz VFO range would work both 75 and 20 Meters. The 9 MHz Crystal Filter would work well with digital LO's/BFO's and you would have great frequency agility. (The Simple SSB uses a commercial 9 MHz Filter and Digital LO/BFO)
But time has moved on and so have I with Digital LO's, BFO's and SDR; but not everyone is ready to do so. It reminds me of when I first started in ham radio late in the 1950s', there was tug of war with the AM/CW diehards and the new SSB crowd. Well it took about 5 years until the mid 1960's where most rigs being sold were SSB with some offering AM and CW.
Today just look at the plethora of commercial radios and even kit offerings --we see either the direct application or the embed of SDR techniques. But just to always put things in perspective we have new work being released on how to build crystal filters.
In case you are wondering while my GQRP presentation does focus on a filter rig built over a year ago, I do include info on SDR rigs. It is important to recognize an audience has many diverse interests. I guess if the presentation were made a year from now the focus would be ALL homebrew SDR RADIG's.
BTW according to the emperor (with a small e) you should vote twice in the upcoming election. Once by mail and once in person. This must be like the Chicago of old -- vote early and vote often! I am affronted by his suggestion and hope you are too!
As a veteran with two trips to South Vietnam, I look at the current revelation that the emperor cannot see military service as anything but negative as direct evidence of someone who should not be Commander-in Chief. It was a priveliege to serve and I am so thankful to have that experience. Cadet Bone Spurs will never understand and that is why he should be voted out of offcie!
Those who are veterans and support this man should likewise be ashamed. BTW my first tour was in May of 1965 --one of the early units in country!
73's
Pete N6QW
A ham shared with us (Bill, N2CQR and myself) a project launched by Guido PE1NNZ where a QCX CW transceiver from the Hans Summers, QRP Labs was converted to an all Mode SDR Transceiver -- yes SSB, CW, AM, FM. Hams across many continents are developing/building on this concept.
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I am a little uncertain as I think initially it was just a conversion of the QCX; but now may be a separate circuit board. What I saw was impressive and just goes to show the collaborative effort happening across the greater ham community.
Through the magic of Hilbert Transforms the signals are manipulated to create the various modes. Oh I think the brains are an ATMEGA 328.
So now the challenge --why can't two of these babies below be made into a SDR transceiver. Harder to do than with two ADE-1's but with some signal steering or four devices (two each for the Rx and two for the Tx) is still within the realm of possibilities. Now mind you a single MC1496 at today's prices is about $0.84. So for less than $3.50 you have all four devices and likely for about another $10 you could buy all the resistors and capacitors. Just in case you are counting pennies -- a single ADE-1 cost about $5, There is already code developed for quadrature Si5351 signals.
We don't even have a back of an envelope and already the design is starting. Now the radio illuminati would argue this is not an efficient design; but can you imagine the arguments surrounding taking a QCX CW transceiver that even uses a Class E amp stage and running it in such a way as to produce SSB signals. It was a challenge that a brilliant engineer (Guido) took on and made it work.
Just so you never loose sight of the nut job behind this blog here is a snap of N6QW in formal attire taken just before a Zoom event.
73's
Pete N6QW