Wednesday, September 13, 2017

Simpleceiver Plus Superhetrodyne ~ An Ultimate form of DifX

The Simpleceiver Plus Superhetrodyne!

 

9/19/2017 ~ Feedback on the Simpleceiver Plus DCR

First let me once again mention the Arduino/Si5351 Circuit board available from KV4QB that can be found here: http://kv4qb.blogspot.com/ I can attest that these are 1st rate boards and WILL shorten the critical path. Thanks again DuWayne for designing the boards and making them available.
 
Several days ago I posted information from Johannes in Freiburg Germany where he designed boards for the Simpleceiver Plus project. Yesterday I am happy to report that Joh has populated the boards and now has a working Simpleceiver Plus Direct Conversion Receiver. Congratulations Johannes as you now have experienced JOR -- The Joy Of Reception.
 
In typical ham fashion Johannes reported he first started inhaling RF at midnight, on his kitchen table using a 12 foot chunk of wire for antenna. It doesn't get any better than that! He sent some photos of his build which I will now post so other can see his work.


Starting with the naked board ...

 
 This is what resulted ...

 




 
 
We have since heard from Johannes beyond what he sent in these photos and he is continuing to work on the project beyond just the DCR and will soon start by populating the board with the Superhetrodyne components. So far he is a pretty happy camper. Thank Johannes for sharing with us. 
 
I am aware of several builds in progress with the Simpleceiver Plus DCR. I would be happy to post photos of projects now in work. Send me your photos to n6qwham@gmail.com
 
My next posting will be "how to build the crystal filter". Also don't overlook the possibility of using a commercial filter for this project.
 
 
73's
Pete N6QW


9/17/2017 ~ More Exciting Information on Circuit Board Availability!!!!!

 
The critical path item for the Simpleceiver Plus project whether it is the DCR or final SSB Transceiver is the LO/BFO using something other than  cranky/rickety/drifty/old school Analog circuits for tuning the rig. The critical path is the move up to the Digital LO/BFO  with the Arduino and Si5351. If it sounds like I disdain the analog stuff --I do! But my position is well known.

[There are solid technical reasons to migrate to the Arduino/Si5351 aside from my flippant comment about old school and that has to do with the Frequency Scheme in the transceiver. Firstly the Crystal Filter frequency is rather high @ 12.096 MHz where most of the commercial ones in your ICOM's, Yaseu and Kenwood's were below that -- like any where from 3 to 10 MHz. This has to do with the practicality of crystal stability where a 50 PPM crystal at 3 MHz is 150 Hertz and at 12 MHz that number is 600 Hz. The stability of the crystal filter is an issue --and these are crystals not some coil and cap.


The second reason is where the LO is placed. Good design practice typically will place the LO above the incoming frequency by the amount of the IF. So our Si5351 is operating at 19 MHz (7 + 12) for the 40 Meter Band. Essentially in the mixer stage we have the LO - the Incoming = 12 MHz. Now the 2nd product out of the LO is the sum frequency of the LO + the incoming and thus we have a component at 19 + 7 = 26 MHz. The 26 MHz is easily filtered out of Band Pass and Low Pass Filters operating at 7 MHz -- as is 19 MHz. The issue here is the alternative input LO at 5 MHz where that is awful close to the 7 MHz Band Pass and Low Pass Filters --not so easily removed.


The third problem given the LO above is good design practice -- have you built a stable 19 MHz VFO lately? Building one at 5 or 7 MHz has challenges --forget the 19 MHz. That is why even though some commercial transceivers were single conversion the VFO was mixed with various crystals to produce higher frequency outputs beyond say a 5 MHz VFO to achieve the desired higher frequency injection frequencies. If you are going to use that approach you just added a whole additional level of complexity. I used the 7 MHz VFO for the DCR as a quick and dirty way to demo that the DCR works. I would not use that approach with the SSB Transceiver.


So given the issues of design practice, unwanted mixing products and stable signal generation you are directly pointed to the Arduino and Si5351. By the way if you are contemplating operating in the just newly authorized 630 and 2200 Meter bands -- the Si5351 can operate all the way down to the 30000 Meter band where your dipole length would be 45720 feet long or about 8.66 miles! Try building that analog VFO to run that rig. Read on for a great solution.]
 
But where does that leave the homebrewer's who want the digital LO/BFO but have never built one and thus while knowing which is the hot end of a soldering iron are not sure about the SDA & SCL pins (A4, A5) on the Arduino.
 
I hinted a bit of this in a earlier posting and now it is time to share. One of our supporter's and in his own right a homebrewer "Supreme", DuWayne KV4QB has designed a universal LO/BFO board that installs the Arduino and Si5351 while making provisions on that board so that a range of displays and peripherals can be connected to the Arduino/Si5351. DuWayne's effort makes your job much easier. The bonus -- he is making available for sale the circuit boards shown below:
 
 
For information on how to acquire the board see DuWayne's blog. You will also see an array of displays that can be used with his universal board.

 http://kv4qb.blogspot.com/

 
DuWayne is selling just the board and the builder/homebrewer must supply all of the other parts and components. But the board is the Critical Path. Contact DuWayne direct regarding acquiring the board(s). Again this is a Universal Board and can be used on any project and not limited to the Simpleceiver builds.
 
Grab one before they are gone. A big Thank You to DuWayne! Largely through KV4QB's efforts the singular obstacle to building the Simpleceiver Plus is now gone! So get off that couch and start building.
 
73's
Pete N6QW


9/17/2017 ~ New builds of the Simpleceiver Plus DCR

Yesterday I received an email from Johannes in Freiburg, Germany regarding his build of the Simpleceiver Plus Direct Conversion Receiver and Superhetrodyne and has allowed us to share his build information. Should mention that Johannes is pursuing a license and is using the project as a means to expand his ham radio knowledge.  There are several photos showing board layouts and parts placement. Joh mention that Microsoft Paint can be used with the templates.
 
 
 
 
 

 

 
 
These boards sure would make implementing the project a much easier task. Thanks Johannes.  A
 
As advertised I will shortly be detailing how I built the crystal filter. Stay tuned.
 
 
73's
Pete N6QW

9/16/2017 ~ Another ECN (ECN#2) Upping the Gain of the 12 MHz IF Amp

Kind of pressed for time today. But had an inquiry about the tank network in the 12 MHz IF stage. Essentially the two 47 PF caps are in series and so they look like about 24 PF which is now in parallel with the 5.13 Uhy coil. I used the 47PF because that is what I had in the junk box and the simulation in LT Spice looked OK.
 
This inquiry caused me to go back and tinker a bit more with the LT Spice and if you adjusted the  two caps (C1 and C2)  that now have an effective capacitance around 31 PF and based on their ratio to achieve 31 PF -- the gain is raised by about 12 dB for a total of close to 30 dB.. The circuit  with the pot adjustment to minimum, the gain goes down to 10 dB. The 30 dB in practice may be way too much --but its better to have gain in the circuits following the mixer than ahead of it. In one of the videos (Part II) it was shown that increasing the gain of the RF amp stage ramped up the noise and I commented about not having it wide open. 
 
Major Hint: Install the capacitors (C1 & C2) as shown otherwise you will not see the increased gain. You are effectively picking off the voltage between the 350 PF and Ground. The 350 PF technically is in series with the 100 Ufd (C7) to ground and the effective value is C2 since C7 is so much larger. If you are having trouble with the concept, think of a resistive voltage divider and if you swap ends of the resistor combination and measure at the junction of the two resistors you get different voltage readings depending what end goes to ground.
 
 
 
 

 
Got to run -- have fun.
 
73's
Pete N6QW 

9/15/2017 ~ More circuit details on the Superhetrodyne configuration.

Here is some info on the circuits shown on the Block Diagram aside from the circuits used in the Direct Conversion Receiver. Below is the IF amplifier blocks and interconnections. Not shown is the Crystal Filter detail but that will be coming soon.
 

 The IF Amplifier Block.

 
Show above is the interconnection of the IF amplifier block into the Simpleceiver Plus Superhetrodyne. On the input side the matching transformer is connected to the "IF" side of the SBL-1 which are pins 3 and 4 connected together. The LO is connected to Pin 8 on the SBL-1 and the Band Pass Filter Connects to Pin 1. Pins 2,5,6 and 7 are connected to ground.
 
Inquiring minds will fire off some emails to me so here is the math. A match from 50 Ohms to 170 Ohms is 1:3.4. If you take a 7 Turn winding squared that is 49 and if you take a 13 turn winding that is 169. (Thank You Mr. Boyer my 8th grade math teacher who required us to know the squares of the numbers from 1 to 20.) Thus 169/49 = 3.44 which is close enough for government work. If you match 170 Ohms to 2.2K Ohms that is 1:12.94 and easily done with 5 turns which is 25 and 18 turns which is 324/25 = 12.96. And of course 50 to 2.2K Ohms = 1:44. Three turns squared = 9 and 20 turns squared = 400. 400/9 = 1:44.4 -- again close enough. (Thank you Mr. Boyer)
 
On the output side of the 2nd IF amplifier this is connected to the input matching transformer (3 Turn side) of the same product detector as used with the DCR. Later this connection will be made to Pin #2 of an ADE-1 Double Balanced Mixer.
 
So you are scratching your head a bit. When we transition to the SSB version I would have to build another J310 DGM configured as a Balanced Modulator and similarly supply Carrier during transmit into Gate #2 and audio into Gate #1.
 
If we use the ADE-1 it can be used in a bi-directional mode and the audio port to the audio amp input is now input from the microphone amp output. Another consideration is to use some relays at the input side and output side so that the Input / Output Ports are switched depending on whether you are transmitting or receiving. This would now only require one filter which really makes things a lot easier and simplified. Not a done deal but now in the plan.
 
 
73's
Pete N6QW

9/14/2017 ~ Further Exploration of the Simpleceiver Plus Superhetrodyne!

Part II of the Simpleceiver Plus Superhetrodyne receiving tests. Added a filter cap in the audio amp to reduce hiss level and explored the three gain controls on the RF and IF Amps. Dramatic is a good word!
 
 



 
Part II Simpleceiver Plus Superhetrodyne
 
 
Part III Simpleceiver Plus Superhetrodyne
 
 
 
Later today I will post some information on the 12 MHz IF Amplifier Stages and Pete's Magic Crystal Filter. The RF Amplifier, Band Pass Filter, Product Detector and Audio Amplifier schematics were detailed in the prior post.
 

For those keeping score above is the "Block Diagram" of the Simpleceiver Plus Superhetrodyne Receiver. Note that the modules that were in the Simpleceiver Plus DCR simply move over. Just a note the DCR has the 2N3904 and LM380 --that will work perfectly. I used the NE5534/LM380 as it was available. I also used duplicate modules so I could keep the DCR intact for other experimentation purposes. Thus the Superhetrodyne is all duplicate modules that are in the DCR. In the event any questions come up about the DCR -- I can still fire it up on the bench.
 

 
 
 
This is the IF stage and is good for 18 dB of gain (R9 = 13.3K) and drops to 9 dB with R9 set to 3.3K. This gain drop is demonstrated in the above video. On the output of the 1st stage following the 2 dB Pad is a 50 to 170 Ohm matching transformer into the Crystal Filter. On the output side of the Crystal Filter which is 170 ohms you need a 170 Ohms to 50 Ohms and then a step up to 2.2k from 50 Ohms. That would mean TWO transformers or you could just match 170 Ohms to 2.2K or 1:12.94. This is an easy match if you have a 5 Turn primary and an 18 turn Secondary. 5^2 = 25 and 18^ = 324. 324/25 = 12.96. That my friend is close enough for US Government work.
 
On the output of the 2nd IF stage there is no pad and this feeds the Product Detector. In the transceiver this will feed the 50 Ohm Port on the SBL-1 or ADE-1. Do not skip THE MATCHING TRANSFORMERS!!!!!!!!
 
Below is a peek at the Crystal Filter(s) which I will cover in a subsequent blog post. Focus on the 4 Pole Filter.
 
 
 
 

73's
Pete N6QW


 
 



 
Before jumping into the SSB Transceiver Configuration, I want to make an interim stop by focusing on building the Superhetrodyne Receiver. This was done for several reasons including the possibility the builder is only interested in having a receiver and will use some other form of outboard transmitter. I can see it now -- a Simpleceiver Plus Superhetrodyne coupled with a Heathkit DX-20. Or maybe a Harvey Wells TBS-50 Bandmaster. Possibly even an SB-400 is your cup of tea.
 
The basic configuration is the J310 DGM in the RF Amp stage just like in the DCR followed by a Band Pass Filter (again like in the DCR). The next stage is a packaged DBM like the SBL-1 or the ADE-1 as that will serve as the receiver mixer (later also used as the transmit mixer stage). The next stage is the IF amp block comprised of the 1st IF stage , (J310 DGM) a four pole 12.096 MHz homebrew crystal filter and then a 2nd IF Stage (J310 DGM). For the Product Detector it is the same as used in the DCR. The audio amp is the NE5534 driving the LM380. Thus there are four blocks all using the J310's configured like a DGM. We will use the simplified "good enough" crystal filter method for building the crystal filter. You are encouraged not to use the Dishal or other arcane methods.
 
 
When we shift to the SSB transceiver I will most likely use an ADE-1 for the Product Detector and it will also serve as the Balanced Modulator with minimum wiring needed to serve both functions.
 
The LO and BFO signals (Arduino Nano & Si5351) are supplied by the same code used for the DCR with only minor value changes (and getting the USB/LSB to display correctly). The DCR had the BFO signals (USB/LSB) set to zero and the frequency being generated for the LO had no BFO offset.
 
Drum Roll Please! Here is a short video of the Simpleceiver Plus Superhetrodyne working today and being used in an A/B test with the SoftRock SDR. Bottom Line --simple circuitry and worthy of a build. The next several series of blog entries will detail the circuits in the Superhetrodyne Receiver and fleshing out the SSB Transceiver configuration.
 
 
 
 
Strap in --this is going to move along quite quickly.
 
73's
Pete N6QW