New Technology for 2020 ~ The SDR RADIG #2

The Lockdown Special (LS) ~ 2nd SDR

July 24, 2020 ~ WSPR Listening


Some listening tests with the 2nd SDR on 40 Meters this morning. Doing OK. I just shifted up to 20M and will report that data.
The 20 Meter Data



Sadly another 1000+ souls died yesterday from the Trump Virus. The medical experts predict that because of the emperor's (with a small e) botched response that the 145,000 death toll today could grow to 200,000 before Election Day. We all need to say"He's Fired!"

Pete N6QW

July 23, 2020 ~ Awaiting some parts!



First Tests!




I hope to start some basic testing of the 2nd SDR possibly today. Basically I want to see that I have the sidebands in the right order and that the 2nd board will decode signals. I did those tests and I am pleased. I will be posting a second video tomorrow. I did have to adjust the I and Q channels so that when Quisk shows LSB it is indeed LSB. 

Using HDSDR I was able to calibrate the Si-570 so when you go to 10MHz you copy WWV dead nuts on frequency. Well actually for fun I made it 6 Hz high just so those FLEX Radio Police on 40M can tell me I am 6 Hz off Frequency.

Interestingly I was spotting some spurs on the spectrum and upon further invetsigation --it was the specific RPi3 I was using. It has had some problems in the past. When I swapped in a New RPi3 --spurs gone. That was further verified when I used the ASUS Tinker Board. 

I am pretty excited about having a 2nd SDR. As mentioned previously it will have plug in BPF's. The testing was done without any BPF and so I was able to listen on 80 - 20 Meters and the copy was excellent.

These initial tests make "cents" as the mainboard has to work on receive before it will work on transmit. So assuming all goes well with all of the tests then I can proceed to the transmit only boards. 

I will provide some detailed photos of the various boards.

Well the Trump Virus took the lives of about 1200 souls yesterday including a 9 year old in Florida. Keep in mind the emperor (with the small e) is demanding that all schools open this fall so your children can be subjected to the Trump Virus. That is the issue --his demand has no strategy to make it happen safely. 

73's
Pete N6QW

#TOT ~ Tune Out Trump!

July 22, 2020 ~ Alternate Names

According to Speaker Pelosi the alternative name for COVID19 is the Trump Virus. What a pitiful briefing yesterday! As if most Americans didn't know: Because of the lack of leadership, things will get worse. Yes emperor (with a small e) 1000 of our fellow citizens died yesterday from the Trump Virus!


The WB6DHW USBI2C and the K5BCQ Si-570 Board

July 21, 2020 ~
Suddenly what you think may not be working is in fact working!

Today I experienced an interesting series of events. I placed my DSO with the counter option on the output of the Si-570 and when you shifted bands sure enough the frequency would change to 4X the operating frequency, But when you moved the mouse across the spectrum -- the frequency would not change. I also found that you could manually enter a frequency and sure enough you would see 4X times that manually entered frequency. So what gives? This testing was done using Quisk but the LO was not actually connected to the RADIG

Then I connected the Si-570 to the RADIG and boom when I moved the mouse --the signals were being tuned. I did find a 1 kHz difference from what is being received to what is displayed in Quisk; but there is a calibration to fix that.

Then it hit me what was happening. Going back to the early Soft Rock configurations, a Crystal Oscillator at 4X was dumped into the 74AC74 and the software then enabled you to tune 48 KHz around that Center Frequency. The Center Frequency was fixed --it is in fact that you were tuning the audio about that fixed frequency.

So now think of the Si-570 as not as fixed crystal frequency but as a movable crystal frequency from which you can tune a 48 khz slice anywhere in the ham bands. In the background of the Quisk when you move to a new section of the spectrum by manually entering a frequency then you are tuning about that frequency about 48 kHz using the audio CODEC (sound card).

So indeed the alternative to the SDR-Kits LLC works. The WB6DHW USBI2C also works -- although I smoked it by an accidental reverse power hookup. Even I smoke things! So add that to your list of optional approaches.

73's
Pete N6QW

More good stuff found in the Junque Box this morning. Dave, WB6DHW has long been involved with SDR Kit Transceivers and sells a line of  SDR products that are quite elegant. He also sells a similar USB Interface Board (The USBI2C Board) and companion Si-570 Oscillator board. Do an Internet Search for WB6DHW. I believe he has some stock of boards that would work with this project. It uses the same K5NWA chip that I mentioned. 


This is the USBI2C Convertor from WB6DHW --small! 

One key piece of the LS is the interface frequency control board between the RPi3 and the two ADE-1's (after passing through the 74AC74). In the original RADIG this was done with the SDR-Kits LLC USB Synthesizer Controller Board. 

So today I looked for what else might work for that piece. Taking a vey selective tour through my JUNQUE Box, I found a substitue. 

In the early days of the Soft Rock transceivers these were crystal controlled. Later on Tony Parks sold a USB Interface board that would contol the Si-570 for frequency injection in lieu of the crystals. I actually think there was participation of the SDR-Kits with Parks. 

I found one of those boards today in my JB complete with the ATMEL microcontroller. About 8 months ago I bought some suitable programmed microcontrollers from Cecil Bayona K5NWA (Springdale, Arkansas. Check QRZ.com) so those might be still available. The rest of the parts are standard resistors, some diodes  and caps. That board also has the control circuitry for PTT. Hit the PTT on Quisk and you get the signal out of the soft rock board to control TR in other parts of the rig. 

The second board I found was an actual Si-570 LO board sold by K5BCQ. This kit also used a microcontroller and a funky extra large non-backlit display. K5BCQ shared with me that they got a carload of these displays for pennies on the dollar and thus they were used in this kit. Read a big display; but not backlit so hard to read without looking head on.

The K5BCQ kit uses a Motorola Microcontroller (16 pin DIP). So in looking at the schematic, I saw if you removed the Motorola Microcnotroller you could access the SDA and SCL pins on the Si-570. Well just a couple of wires later I was controlling the K5BCQ Si-570 Board via the Quisk software. Don't you just love it when a plan comes together.

If you check WB5RVZ's website you can find the schematic for the Soft Rock USB Interface Board and Cecil Bayona (K5NWA) had the Microcontroller. BTW that same Microcontroller works in the SDR-Kits LLC Board. It is like incest!

 The USB Interface Board.


 The K5BCQ Si-570 Board. This Kit has been retired


The RADIG Board

So there may be an alternative to buying the SDR-Kits LLC board. One thought comes to mind as I seem to remember one of the earlier Farhan Transceivers (Minima) had an embedded Si570. So that might be a possibility if that is true what I recall. 

I do not believe the code set architecture for the Si-570 and S-5351 are the same; but that might be worth investigating as then the Soft Rock USB interface board could simply control the Si5351. One immediate problem I foresee is that the Si-570 essentially has a single clock and the Si-5351 has three. Thus unless you address which clock to use [on the Si-5351] then no output is likely to result. There are also some setup instructions for the Si-5351 such as the power output and which PLL (A or B) to set. So there may be some additional conditions to be met and a simple plug in and replace may not be so direct.

A tunable LO frequency is what counts, not the source device. Thus the ability to use the Si-5351 would be a huge advantage. If you know the answer then email me at the email on the masthead. 

It is amazing what a bit of scrounging might turn up.

73's
Pete N6QW







A 2020 version of the Paraset... 

California (Ventura County where I live) has returned to the prior lockdown state. I received formal notification of this action yesterday via my local Catholic church (St, Julie Billiart) which had only been back open for a couple of weeks. 

But technology to the rescue... Mass will now be live streamed over Facebook and You Tube. But a new twist: outdoor remote mass in the parking lot. It seems like our church located some giant jumbotron TV screens to be installed in the parking lot. You are encouraged to bring your lawn chair which can only be placed on marked slots in the parking lot (social distancing). But still another requirement. You must register via email before attending so that they will have contact tracing data. Wow someone has thought this process through.

BUT (this is so Catholic Church) if you watch on you tube or facebook --do not neglect the mail in collection plate. This may be construed as "The Sermon on the Amount". 

So now that we are back in lock down time to work on the Lockdown Special, a multiband homebrew, scratch built SDR transceiver,

But first a short bit of Nextion Fun...




******

We started first with a G Simple layout of the board which in large measure was dictated by some available PC Board stock I had. This design is in the CNC computer so cutting a board took about 5 minutes. In the 2nd photo we added the components and about 90% of the wiring. The board is roughly 3X4 inches. 



The next step will be to add a second board that will house a relay steered bi-directional amp and the plug in Band Pass Filter assembly. I have two choices for the bi-di amp and have used both. One involves two J310's connected as a Dual Gate MOSFET and the 2nd is a 2N2219A (hot biased). You do need a heat sink for the 2N2219A. One ham recently emailed me that he got a serious burn on his finger when he touched the 2N2219A that was installed without the heat sink. How many times can I tell you --it needs a heat sink ( a big one).

This board will be the same size as the mainboard above. For more info on the wiring of the 74AC74 which is hidden under the machined pin socket and the general hook up of the other components see www.n6qwradiogenius.us

I purchased BPF Boards from QRP-Labs and they are in route to me (about three weeks as they come from Turkey); but I have some individual BPF's that I will hardwire for test purposes. For less than $15 plus shipping you get three Plug In Boards.

The Audio/Mic amp stages consist of a dongle (Sabrent ~ about $7 from Aamazon). The I/Q audio processing is done with an Optimal Shop USB 2.0 Sound Card (Amazon ~ about $16) and I heartily recommend shopping for a bare bones Raspberry Pi3 SBC (roughly about $35). The RF Driver board will use another 2N2219A and the final will be the RD06HHF1 ($5 from RF Parts). The USB Controller Synthesizer will be the kit (with the CMOS Si-570) from SDR-Kits LLC (in the UK about $30)

For the Low Pass Filters (LPF) use the W3NQN design and you can find this on the Internet. These filters are the gold standard and address the 2nd harmonic issues.


Watch this space.

73's
Pete N6QW

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