Wednesday, October 11, 2017

Simpleceiver Plus SSB Transceiver ~ A new DifX

A Move to the Simpleceiver SSB Transceiver


The first steps to the Transceiver Configuration.


10/16/2017 ~ Response to some questions.

The Ghost in the Machine has struck again and now it seems I can't respond to questions that are posted. So I will do it this way
  1. I used two relays for some specific reasons. One is of course thinking they would be better for the isolation issue and 2nd -- That is what was in the Junk Box. I do think this isolation is an issue as I found that was a problem when I used the diodes. The diodes did not prove as good as the two relays.
  2. Following on to Jan's comments. Yes a pair of TIA amps does involve six transistors just as the J310's would require 4 for a pair of amps. Jan, I guess my approach has always been that there is never a single point solution. Often I see and hear comments that the TIA is the only amp that should be used or that the Bitx is the singular approach to building a transceiver. Today I have one Bitx and only one that uses the TIA amps. Thus about 20 or so other transceivers  use other approaches. The bottom line is to foster experimentation and trying new things.
Pete N6QW 

10/16/2017 ~ J310 Spice Model & Photo of IF Amp Block

I received an inquiry about how to find the LT Spice Model for the J310. I am not sure that LT Spice has updated the library with the J310 --keep getting a message about it being 764 days since I updated my LT Spice. Guys there is a very good reason why I don't do things like that -- I updated my Arduino IDE and none of my old sketches would work and in fact I lost some sketches. That was a disaster!
Now if you look carefully at this blog page you will see that long ago I added a Search Block. If you type in J310 Spice Model it will take you to a page about two years ago called Simpleceiver 7 and on that page is a link where you can find the spice models for many devices including the J310. [Do I have to do all of the heavy lifting? ] Anyway that page has now been updated to the following link:
So I guess it is now time for me to remove the Search Block as it obviously is not being used!
I have installed the two relays on the IF block module. I also installed a 7805 which provides power to the two relays -- tried it initially with just a 78L05 -- too much current draw with two relays. The 7805 is sitting next to one of the relays. I have yet to install the RG-174U cables which are used only on transmit but if I switch the relay --the receive signal is not in the loop-- so my quickie test tells me I wired it correctly. You can also see the board with the ADE-1 Product Detector / Balanced Modulator installed.
IF Block Module with Relays
Next to the ADE-1 is a blank area for the microphone amplifier which is the next build. Once I have the Microphone Amp built I can test the low level transmit stages. See there was a method to my madness. We are getting closer to having the transceiver built. Keep in mind how I earlier said that once you have the Superhetrodyne built that you were about 65% of the way to having the transceiver --now you can see why I said that.
Stay Tuned for more excitement!
Pete N6QW 

10/14/2017 ~ Switching the IF Block Module ECN #2.

In an earlier series of posts I detailed how to keep the IF Amplifier Module and Crystal Filter intact and arrange for the switching of the signal direction using diode steering. My first attempt at doing that raised some issues about signal isolation and thus am changing that approach to using two simple small relays. The schematic for that change and the notes explain how it works. The relays also make it easier to retrofit the board --lots less wiring and lots less parts. The relays are SPDT from Omron G5RV - 5 Volts. They were bought surplus form All Electronics here in California. I think the price was under $1 each.

 Hope you can read the drawing and the notes. Engineering Drawing was not one of my strong suits when I was in College.
We are getting much closer. I will install the 2nd relay tomorrow and take some photos so you can see.
Pete N6QW

10/12/2017 ~ A Question about the J310 Configuration

Jan Ciger posted a question about why use the J310 as the basic amplifier circuit as deployed throughout the Simpleceiver Plus project, versus using the Termination Insensitive Amplifier building block from Hayward and Kopski vintage 2009. That is a good question and so I will attempt an answer as to the "why".
Fundamental to the answer is how I build things. Several days ago I responded to Johannes in downtown Freiburg suggesting he build a second receiver that was not so nicely packaged on a single board. My suggestion was that he build another one made up of modules i.e. audio amp module, RF amp, Product Detector that in effect becomes a test bed.
Thus we introduce the  rationale for the concept of an Experimenter's Platform. By building in modules, it is possible to try new circuit elements without destroying the whole project. Another key factor is the use of you tube videos. You can film a baseline of performance and then when you make a change you film that as well. Boom you now have documented data like when you go to the eye doctor and are being fitted for glasses. Is lens A better than lens B?
A second point is that we started the Simpleceiver Plus Project with the concept of a very basic and universal common circuit template. The  building block layout for the RF amplifier (Transmit or Receive) was essentially the same as for the Product Detector as well as the IF amplifier blocks. This made possible the use of very common parts and a limited number of parts values. The use of LT Spice enabled fine tweaking of a circuit dependent on its use. I could evaluate an RF amp circuit using the J310's and then see how that works for the IF amp. Further I could adjust the gate voltage (or introduce a signal on Gate #2 when used as a Product Detector) and see the performance change depending upon the specific application.
Now I am beginning to understand the real issue! I am not a Farhan, Hayward or Kopski!  Nor am I well known in the ham community as they are. So why would I suggest the use of J310's configured as a Dual Gate MOSFET versus simply pressing on with the well documented and frequently mentioned TIA?
Obviously many homebrewer's have heard that Dual Gate MOSFETs are like ancient technology --so much so that RCA no longer makes the venerable 40673. Most DGM's made today are surface mount so another "bad feature". The TIA (Termination Insensitive Amplifier) circuit was specifically developed for use in bi-directional radio transceivers --so again why in the world would you use J310's --and who is the N6QW guy?
For your Dining and Dancing pleasure I have prepared a chart that compares some of the features and benefits of the two circuits.
In looking at the chart it depends what lens is in place ( A or B). The TIA has many fine attributes and is well known and revered in the EMRFD community. Besides the  J310's have not been used in  a broad band mode but rather specific use of LT Spice enabled the performance to be fine tuned for a narrow band of frequencies.
For the most part they are comparable in performance. There is one aspect that I do find as being a difference and that is the ability to use AGC or manual gain. There are several You Tube Videos where I demonstrated the manual adjustment of the stage gain in the RF and two IF Amps -- I thought that was pretty impressive!
Now for a moment back to the Experimenter's Platform. It would be an easy matter for someone with this burning question to simply substitute TIA amps for the J310 amps and decide which is better. I have built a 20 Meter transceiver using the TIA amps where initially I set the gain for the 15 dB (using the 1st set of resistors in their chart). I was underwhelmed with the performance in that there was insufficient gain and the receiver sounded deaf.
When I changed the two resistors (from the data table) in the TIA application note so that the gain was 24 dB then that was more like it. Initially I thought I had a wiring error or bad parts --nope 15 dB per stage was not enough. Keep in mind that you have 6 dB of conversion loss in a SBL-1 and there is loss in the SSB filter. By my WAG I had lost about 15-18 dB of gain in the two SBL-1's and the crystal filter.  Adding about 18 dB of gain (15 to 24 = 9, and 2 X 9 =18) made it work.

I hate to say this --but it is gain across the whole topology that is the key factor --hold back the gain of the front end (because you amplify the noise as well) and make up that gain in the IF and audio stages. Thus you may get the point of my having adjustable stage gain capability for the RF and IF amps.
While I have not measured any noise figure ( I don't think I would even know how to do that) but I can tell you and others have commented --the signals seem to "pop" out of nowhere and the background noise between stations is low. So I guess that counts for something.
For those who may not believe N6QW actually built a transceiver using the TIA amps see below. [So OK stop drooling --- it does look like a rather nice layout!]
Now Jan, back to your question. You need only to listen to the current You Tube videos and ask do the J310's configured as a DGM sound OK? After all it is how it works and not so much what is under the hood.

Maybe a more fundamental question would be would I ever use a TIA circuit again? The answer is it depends but more than likely not. My first choice would be the J310's followed by the Bidirectional circuit I developed using the Tri-Quint MMIC amplifiers. The Blue Rig at the top of the masthead has the MMIC amplifiers for one of the stages.  Given what is the Simpleceiver Plus project (a clue is in the name), the J310's were a clear choice.
Thank you Jan, for your question as I am sure others would want to know why I did what I did.
Pete N6QW
It is always best to start with a block diagram and this is shown below. You will note the blocks that are highlighted in yellow which reflect what is built so far. Noteworthy much of the built receiver becomes the transceiver.
I have posted several videos of the Simpleceiver Plus receiver configuration and I believe what you heard reflects the performance built into the design. Now look carefully at the block diagram you will see that many of the circuits are used both on transmit and receive. So this should be a huge flashing billboard that by working on the receiver and having it perform well will carry over to the transmit side as they are the same circuits.

What is not shown is the control/switching circuitry which will be detailed in subsequent postings. Thus it is imperative that you have the receiver working just as you heard on the you tube videos before starting the transceiver.

The next few days I will spend cleaning up the Simpleceiver Plus bread board by removing the original Product Detector and installing the ADE-1 onto the bread board. the plan is to take detailed photos so you can follow along with your build. We are getting closer.

Pete N6QW