New Technology for 2020 ~ A Second ZL2CTM SDR Radio
When You Know Stuff, You Can Do Stuff! All In A Days Work!
June 12th, 2020 ~ WSPR Data for the New 40M Loop Antenna
Tabular Data for Transmit at www.n6qw.com
Most stations that heard me at 500 milliwatts are close in; but N6QW was heard in New Zealand. Received stations were from Japan, Australia and many across the USA for about a two hour period.
Two days is just that -- two days.
No Op-Amps, Precision Capacitors or Resistors were used for this evaluation.
June 11, 2020 ~ 1:2 Magic Balun Info
With thanks to Lars we now have info on how to build that 1:2 Balun. It is like a head slap moment one you see the pictorial. Initially I had seen just a photo of the completed balun which used the same color wire for both windings -- it was hard to tell the actual number of turns and what connected to where. The color coded wire makes everything lucid! The 1:2 matches 50 Ohms Unbalanced to 100 Ohms Balanced --This will also work for other antennas aside from Delta Loops.
Ran some preliminary WSPR tests with the new antenna on 40 Meters and was heard in Australia running only 500 milliwatts. So that is a good sign but only one day of observation. I will continue to collect data and provide hard statistics on the antenna based on a period of many days of observation versus just a single snap shot in time.
Since there will be much data I will most likely post the results on www.n6qw.com. Accordingly I will post info on this blog when I have posted the results on the website.
No Op-Amps, Precision Capacitors and/or Resistors were used for the evaluation.
June 10th, 2020 ~ New Antenna + SDR
So late yesterday I had the new antenna configuration in place and connected to the ZL2CTM SDR Rig.
Now the burning questions: Were there angelic voices being heard gently singing in the ether, Were there rock crushing 40dB/S9 signals being heard coming out of the speaker, Did the whole SDR rig take on the aura of Juliano Blue, Was the SDR Rig being driven into saturation from so many strong signals, Did it seem my station was on par with the $20K ICOM IC7851? OK Back to earth!
I made several contacts with the new lash up and the received signals were strong and my reports were like wise in the S9+ category running only 100 watts. But hey dude, this is like saying a Six Pole Op-Amp phasing network has 70 dB opposite sideband suppression (like I was told by one ham).
We need to have some real data on performance and that data should be over a sufficient sampling period so as to look at the average of band conditions. From this data then one could make cogent and reasoned pronouncements on performance. The perfect tool when you have no fancy spectrum analyzers or costly test equipment is to use WSPR.
I plan on using 40M WSPR to look at both the received signals being heard as well as my transmitted signal at 0.5 watts. I happen to have data from prior WSPR runs using the older antenna configuration and will use the same transceiver that was used on those prior runs. Thus the variables are reduced to a few such as the new Antenna itself and band conditions. Now if you sample over a long enough period then hopefully we will arrive at average band conditions.
The selection of 0.5 watts of power output will provide a baseline that says --for this low a power level the antenna performs thusly -- at 500 watts --it only gets better. (That is a 1000 times increase in power.) I will also have a chance to see the area of coverage and has that changed since I did have to shift the broadside direction a bit to fit on my lot.
I will share my results as I develop the data base.
Needless to say no Op-Amps and or Precision Capacitors or Resistors will be used for this evaluation.
June 9th, 2020 (Late Afternoon) More Antennas!
Daily I take the XYL to a local Mall which is still closed along with a sack lunch and we just park in an abandoned lot and have lunch. Afterward she gets to walk around without concern for social distancing or having to wear a mask. It is outdoors and no one around! So this is good.
Today while we were sitting in the car eating our sack lunch it was like a lightning bolt hit me! I already had the makings of a Delta Loop that would enable me to experiment before I committed to buying hardware and homebrewing a complete metal antenna. True it would be fixed in one direction but by making it for 40 Meters it will also work on 20 Meters.
So here is the idea. My 40 Meter antenna is 98 feet long so it would look like 3/2 wavelengths on 20 Meters. That was the starting place.
Now in looking at the Single loop Delta Loop the formula is 1005/Frequency. Thus for 7.2 MHz we are just shy of 140 feet. The two legs are 49 feet each and so a piece to connect the two ends would be 42 feet. All I had to do was find a piece of wire that after connection was 42 feet long. So for 20 Meters this is a 2 wavelength long loop antenna! That has got to mean something!
I have a wide range tuner and sure enough I was able to get a good match for 40 Meters and 20 Meters as well. Later tonight I can see how the East Coast is coming through on 40M as that is the broadside direction.
One area of tinkering will be the Balun. Right now I have the 9:1 in there and when the cores come I can try winding some different ratios to see what works best. If this 40M antenna conversion works, all I can say I have been asleep at the switch these last 5 years.
This will be a good test bed to see if I proceed with the metal version. The current arrangement has about a 45 Degree tilt to it, so I don't know how that will hurt or help.
June 9th, 2020 ~ Antenna Stuff
For those of you who regularly listen to the Solder Smoke Podcast, specifically SS#222, I mentioned this might be a great time to work on antennas.
Several years ago I undertook the installation of a two element Mosley Tri-Band Beam. The technical aspects of the installation have worked out well. My install has weathered several years of some fairly significant wind storms and the beam stands tall and has not fallen down.
The problem -- the beam itself is intermittent and I hardly got a year of service before it started acting up. It will load and then the SWR goes to hell and the received signal drops off the face of the earth.
A contact with the manufacturer was not very fruitful. The beam will take legal limit which I never ran and so the probability of a blown or intermittent trap is less likely. This was affirmed also by Mosely. One possibility was that there was a latent defect in the traps at install. The coax could be an issue and I have a new piece ready to install; but the pesky secondary problem -- I don't do roofs or climbing and getting someone to take down the beam is problematic as the Covid19 is still rampant in California.
I tried to noodle my way through a repair of the beam. So you take it down and evaluate the first easy possibility -- bad coax and get it hoisted back and perhaps the problem is still there which requires a trap replacement. That adventure for the traps is $150 and not counting the labor for down, up and maybe back down.
I really only want a directional antenna with some gain for 20 Meters and that opens up spending my limited cash on a new antenna that would cover just 20 Meters.
There is a company (SAL) that makes a 20 Meter Moxon (all metal) and that cost is $400. I could buy a single band Spider Beam -- more than $400. Or I could write K3LR a check for $600 for a 20M single band Hex Beam or send him $300 for a EA Delta Loop.
The Delta Loop has less gain than the other beams but offers possibilities for me to homebrew an all metal version for less than $300 that DX Engineering charges. Thus I have been doing research on Delta Loops.
This is where blog readers come in... I am looking for the following info.
- Anyone have a Delta Loop and your experience with this antenna?
- Anyone homebrew a Delta Loop?
- For 20 Meters it looks like using the formula 1005/(Operating Frequency), that about 70+ feet of antenna is required with a 1/3 wavelength in each leg
- There are many configurations for arranging and feeding the Delta Loop and my approach would be to have the equilateral inverted triangle with the feed at the bottom. Anyone have this configuration?
- The input impedance is around 100 Ohms (balanced) and there are several methods shown for matching including a quarter wave matching section of 75 Ohm coax and another using a 1:2 Balun where 50 Ohms unbalanced is matched to 100 Ohms balanced.
- Now this is where the 1:2 Balun's shown on the Internet and you tube videos are much like saying she has "big boobs" which is described as anything from a cup size 30A to a whopping 44DD. There is much creditable info on 1:1 4:1 and 9:1 Baluns --but the 1:2 is a gaping hole. There are some commercial companies selling 1:2 Baluns which typically have a price point of $100. I have a FT240-43 core coming ($14) and I already have a spool of #16 enameled wire. The piece de resistance is a HD plastic electrical outlet box which is about $4 at Home Depot.
- To date I have not seen a cogent electrical schematic of the 1:2 Balun as to number of turns/connections. Additionally photos of homebrew 1:2 units are all over the map (like the gal with big boobs). So if anyone has a reliable schematic sharing of same would be appreciated.
- This past week there have been some good openings on 20Meters so there is an incentive to get cracking.
- No Op-Amps or precision capacitors or resistors would be involved with the build of the homebrew Delta Loop.
***********June 8th, 2020 ~Alert! Alert! Alert!
I received an email today that sort of knocked me off my feet and thought I would share this interesting situation with the blog readers.
Some of the blog readers might be members of QRPARCI and thus receive the publication QRP Quarterly. At one time I belonged to QRPARCI and contributed many articles to that publication.
In 2013 at the suggestion of one of the editors I actually designed a 30M CW Transceiver and built the unit which then was formally published in QQ at that time. As you well know I hardly ever operate CW; but this rig had some nice features like RIT.
That rig has since been canabalized and the modules are now resident in at least a half dozen SSB Transceivers. I never did see much interest in that project from the readership and I was not put out because of a lack of reader feedback. This was so unlike the LBS project!
So today's email... I was advised that the latest QRP Quarterly Issue contains that same article that was published nearly 7 years ago. I must claim ignorance as I was not made aware that it would be republished and never contacted about that possibility.
Since I was never compensated for any article I produced or reimbursed for all the parts used, that leaves a question in my mind about who really owns the article. Maybe some of you lawyers out there have the answer.
So if anyone has a question about the article --don't contact me as I no longer have the actual hardware in its original form and that was a long time ago. You know I had a bad feeling at the time about that project and now here it is like Freddie Kreuger.
If you have any questions on the 30M CW Transceiver as it appears in the current QQ, contact the QRP Quarterly Technical Editor not me. Regrettably my name is on the By Line; but I cannot vouch for what was republished as being accurate.
June 7th, 2020 ~ A Hardware Tour!
On the Air QSO ...
June 6th, 2020
Yesterday as I looked at the second build of the ZL2CTM SDR Transceiver, I realized I had successfully anchored down all of the boards on two metals plates; but had a structural problem. The issue -- how to make it an integral assembly. There was no easy way to mechanically assemble (connect) the two metal plates.
Then I remembered that about two years ago I bought a large aluminum chassis to house the original RADIG SDR Transceiver. I did not proceed with that plan as it would have involved a lot of metal bashing. Now the problem where did I put it for safe keeping? I found it. A preview...
( This photo has the Mic Input and Audio Gain Control Swapped for better ergonomics)
This is when the value of experience comes into play. The Plan: I carefully removed all of the boards from the two metal plates and used those metal plates plus the front sub-panel as drilling templates for metal bashing the aluminum chassis. The chassis size is 12X8X3.
Firstly I used heavy duty tape (Gorilla Tape) to tape the drilling templates to the metal chassis. This is where you measure twice and cut once. You have to keep straight that the template must be the mirror image side that you drill through. It took only about 15 minutes to drill the chassis through the two plates. Also a caution about clearances and centering to allow room to work on the various boards once installed.
One particular assembly has a clearance problem. For those who use magnifying glasses to pick over my work, you will see a black rectangular box assembly that is fitted with two 3.5 MM stereo jacks. (Left side of chassis looking from above.)
This assembly is sold by PJRC (Teensy supplier) for the purpose of isolating the audio ground from the system ground. Without this device --the SDR suffers from a high pitched whine. There is a short cable to connect this box to the Teensy CODEC board and the connectors are straight in so that is the clearance problem.
Normally with flat stock I can use my CNC mill to cut the rectangular hole for the LCD. Not easy to do with an aluminum chassis. So after outlining the size of the hole on the front panel first with a pencil then with Gorilla Tape, I drilled out the LCD panel space using a series of holes that were aligned slightly smaller than the actual cut out. The final holes size was carefully filed with a series of files. Initially I used a rough file and the finish filing was done with a Jeweler's File.
With all of the boards already wired and aided by the cable ties (good idea Pete) I was able to simply drop the boards into the inside of the chassis and bolted everything back up. I used 4-40 nuts and bolts with liberal amounts of star washers so there would be a "tight" connection between the copper boards and the metal chassis.
The IRF510 assembly, Low Pass Filter and TR Relay were simply bolted in place on the back panel. The bonus of course is the whole chassis is the IRF510 Heat sink! The final wiring involved connecting to the IRF510 Board, the TR Relay and the External Amplifier control circuit (Who in their right mind runs QRP?)
Luckily where the TR Relay is located and where there is the interconnect to the receiver circuitry is but a short 2 inches --now that was pure luck -- but made things "Tight and Tidy".
A short piece on wiring --- I use Yellow wire for anything transmit and Orange wire for anything receive. This project uses a relatively small number of boards so not as difficult as one with more boards --but having the color coded wires sure makes things easier to trace and troubleshoot. Wiring that has power applied at all times is Red.
There is a switching power supply installed on a piece of perf board right behind the LCD. This is a 9 to 18 VDC IN to 5 VDC OUT used to power the Teensy 3.5, CODEC Board and the Si5351. This was to isolate this critical part of the circuitry from the rest of the rig. This little switcher is good for 2 amps and is made by Mean Well. I heartily recommend using this supply for application to this critical circuitry.
The blank panel space on the right hand side will eventually have a panel mounted speaker installed and there is a plan afoot to swap the locations of the microphone input jack with the audio volume control. The two controls used the most are Tuning and Volume. It makes sense to have them grouped close at hand.
BTW I have two additional switcher units good for 3 Amps a piece -- and there is a plan to take the original RADIG with the Raspberry Pi3 and 7" inch HDMI and run the RADIG completely off of 12 VDC as a portable rig.
Please note: No Op-Amps, and/or Close Tolerance Capacitors and Resistors were used for this project.
The total elapsed time to convert from the prior assembly to the chassis form was about 5 hours. The work was greatly aided by having in addition to a CNC mill a Manual Mill. When you have the right tools a lot can get done.
I hope to use this Rig on the CPAC Contest today.
Forget that Phasing Stuff. Real Radios use Microcontrollers or Computers!
No Fake Claims about Opposite Sideband Suppression. No Op-Amps! No Fiddly Circuits. No Expensive Capacitors. This one works!
Note the aluminum bottom plate to collect all of the circuit boards and the liberal use of "pink" cable ties, Five watts of pure joy and another opportunity to use my can of Juliano Blue Spray Paint. (Including my hands when the can accidentally misfired)
Now this rig makes sense and is a dream to operate. No reports about the other sideband. How quaint!
I am skeptical that all the glowing reports about phasing rigs I received are in fact true. Basta!
CPAC Contest this weekend -- good opportunity to use the new rig.