Saturday, May 7, 2016

A New SSB Transceiver from N6QW -- Now Working!

5/23/2016 ~ Late in the Day Close to a Smoke Test

The rig sure cleaned up nice -- not too many jumbled wires!!
 
Pete N6QW
 
 

 

5/23/2016 ~ Progress on Cleaning up the Rat's Nest!!!

As I frequently only 15 or minutes at a time to work on project based on my other commitments, I did
manage to get some of the wiring "cleaned up" as you can see below. I use a standard --Yellow for Transmit wiring and Orange for Receive which helps quickly identify wiring to various stages. About two more days and we should be able to run a smoke test. The actual work is maybe only 1 to 2 hours -- but at 15 minutes at any one time stretches the overall schedule.
 
73's
Pete N6QW
 
 

 

5/22/2016 ~ Progress on the Box!

The size will be 8 inches wide by 10.5 inches deep and slightly less than 2 inches high. So ask why that size? The bottom plate is a piece of PC Board I had that was the 8X10.5 --so no cutting and as it turns out is just about the exact size needed-- The Radio Gods Have Spoken!
 
 
The front panel is very ergonomic in the placement of the controls. Starting at upper left is the Headphone jack and below that is the Microphone jack. Next to that is the volume control and the two switches include LSB/USB and the red Push Button places the radio into Tune, which also gets displayed on the front panel as TUNE during the timed tune period. I finally found a perfect application for the weighted main tuning knob and next to that is the main display. The back panel has the BNC antenna connector, an RCA Phone jack for linear amplifier switching and an entry port for the power cord.
 
This is the ugly stage where the boards are being fitted inside the homebrew case and there are wires every which way. I promise things will look neater!
 
[So OK I probably convinced you there was a lot of "noodling" regarding the box layout and how the front panel would look --actually NOT. I just sort of marked the panel with a bunch of pen marks and said "BASTA" and then cut the holes -- I got lucky this time.]
 
Pete N6QW
 
 
 
 

5/20/2016 ~ Lets get the Rig into a Box

I always do this part wrong -- I don't think inside the box! After carefully mapping out the radio topology usually my last thought is the enclosure and that usually brings on a lot of grief in the process. This rig will now be fitted into an enclosure that is 8 inches wide by 10.5 inches deep and 2 inches high. Essentially flatter and not so tall!
 
Sometimes when we are busy multi-tasking we will make an error in calculations and that just makes things worse. But it can also make things better. I measured the standard 128X128 Color display and proceeded to mill out a hole in the front panel with those dimensions. It was a really nice "squared up" hole. Only the problem was that the dimensions that were used were the outside dimensions of the whole display enclosure and not just the screen. You can't un-mill a front panel. The I remembered I had a slightly larger display in the bin --a 128X160. Well dumb luck me --the hole size was perfect for the larger display. No problem --or so I thought!
 
Well the code for the 128X128 is not unlike the code needed for the 128x160 BUT not the same. So while I got the smaller display code to fill the larger screen -- there was a white band on the face of the screen. A little research revealed an almost entirely different instruction set -- so after a bit of fiddling I got the code to display full screen but then had to move the various elements to fit on the screen at the proper place and to fully take advantage of the larger display screen. Well after about three hours it all came together. So now we are ready to add other elements to the front panel.
 
 
As usual the front panel will be painted flat black. If readers would like to have the Arduino code for the 128X160 TFT display --send an email request to N6QW (n6qwham@gmail.com)

You always worry when you make a modification --will it still work. After making the install I heard W5IP in New Mexico and gave him a call running 8 watts -- he heard me at 5X7. "CD" was running a FT-9000 a legal limit amp and a three element 40M beam at 70 Feet. Needless to say he was really strong here at this QTH. This is now the 4th contact with the new rig. Yeah!!!!

 
 
73's
Pete N6QW

 

 5/19 ~ 3rd Contact with Stu, W7FE in Las Vegas

The contact was initially made at 8 Watts and then the band lengthened out and so I cranked on the "afterburner" and we spoke for about 15 minutes. Stu commented that the audio sounded good --not bad for a single 2N3904.

2nd Contact with K7KF, John in Utah

Running barefoot at 8 Watts had a nice exchange with John in Southern Utah. I would guess the path is in the 600 to 1000 mile range and my report was 5X5. My antenna is a droopy dipole. So contacts can and are made with this simple radio from N6QW!

5/18~First Contact with the New Rig

 
5/18/2016 ~ As many of you readers know the health situation of my XYL has severely limited my bench time. I am not grumbling; but merely know where I must spend the most time and that is not on ham radio! But what little time I do have available has now challenged me to not so much build a lot of new hardware but to look around the shack and see what is available. So it is with this new transceiver.
 
Today I looked lovingly at the LBS project co-authored with Ben KK6FUT, which was written up in QRP Quarterly in 2015 --and I said why not? The original LBS was on a board 2' x 2' and so a little hard to lug around. This morning I liberated the bi-lateral RF amp Transmit pre-driver board and the intermediate/final amp board (IRF510). I also took the LPF and TR relay. Five minutes of screwing the boards down to the bench top and hooking up a few wires and I was ready to put the rig on the air.
 
Boom --heard KK6ZUU, Steve, down in San Diego calling CQ and I returned his call running about 8 watts. And there we were -- in a serious QSO with the new radio -- he gave me a 5X9 and he was the same here. The distance between us is about 150 miles. Steve has a brand new ICOM 7300.
 
This is exciting --as it shows with just a few components what can be done. I will later publish the schematics of the additional boards but you can find them on my websites (n6qw.com and jessystems.com) under the LBS project (Let's Build Something).
 
Below is the driver stage ~ 2N3904 + 2N3866 (direct from EMRFD) and the IRF510 Final similar to what is used in the BITX transceivers.
 
 
 
 
 Next we have the bilateral stage using 2N3904 separate amps that are relay switched.
 
 
I am stoked and ready for more QSO's. I know it looks like crap; but works like hell!
 
73's
Pete N6QW
 
 
5/14/2016. First Tests of the Transmit Portion of this Project. I am very satisfied with the results and you can witness the same by viewing the video below. There is a really good reason why I like the architecture that I have developed for these simple rigs --few adjustments and that provides two benefits: 1) Easier to troubleshoot 2) Performance is well known, documented and understood.
 
So give it a try -- once you have the receiver built --just a few more parts and you have the transmitter.
 
Pete N6QW
 

 
A New Display ~ Postage Stamp Size (5/11/16)
 


video
 
 
 
 
 
One day of progress: Band Pass Filter, Mic Amp and Audio Amp Installed:
 

 
 
 
5/8/2016 There is added info about using J310's in lieu of the BF991 for the Rx Tx Amplifier stage. The video shows a small 10K pot with the top end to + 8 VDC and the bottom to ground with the wiper connected to a 22 Ohm resistor and on the other end to Gate #2.

5/9/2016 Replaced the 12.096 MHz Filter with a Yaesu Filter from an early FT-101. The Cf is 3.180 MHz. probably OK for a single conversion on 40 Meters. Better suited to dual conversion on the higher frequency bands. The LO is above the incoming so it is a down mix to 7 MHz. The Z in/out of the Yaesu Filter is 500 Ohms. The match to 50 Ohms is a 10 to 1. This can be done with a 19 turn auto transformer tapped at 6 turns on a FT-37-43 core. It is turns ratio squared. If you can't figure that out then you shouldn't be homebrewing radios!!!!



 
After a couple of days of testing, it became apparent that the former 30M CW transceiver board worked OK as a receiver section, but I was having significant problems with adding the balanced modulator along with the NE602 Product Detector. No matter what I "noodled", it would be a complex switching arrangement --read problematic.
 
So it was time to simplify and that is when I decided to use the Plessey  bidirectional amp circuits along with SBL-1's, one on the front end serving as both the transmit and receive mixer and one on the back end serving as the product detector on receive and the balanced modulator on transmit. The LO and BFO would remain connected to these devices at all times. Simpler is better!
 
In my bin of boards and partially completed projects, I had such a board. But this board had different IF filters and having had such good luck with the 12.096 MHz filter in the Simpleceiver project I built another filter for that frequency. Boom --a couple hours of work and there I was listening to signals on 40 Meters. The audio amp is a small board containing a 2N3904 driving an LM386. The microphone amp will be a single 2N3904. The Si5351 will now supply both the LO and BFO signals. Again the 128x128 TFT will provide the frequency display and other pertinent data. This rig while similar to the LBS-II has a mix of through hole and surface mount components. The differences include the choice of IF frequency and the signal chain beyond the main board.

I also found in the bin a surplus Yaesu 3.180 MHz Crystal Filter from an early FT-101, which may be tested in this radio as well. That said don't rush out and buy a filter. Keep in mind filtering in the Band Pass Filter as the 2nd harmonic of the BFO (2 X 3.180) is awful close to 7.0 MHz. But with the Si5351 a couple of lines of code changes and the Yaesu 3.180 MHz Filter is operational --ahhh the power of software. Think what you would have to do if the rig was all hardware based?
 
Rounding out things will be the use of a bidirectional amp consisting of a single BF991 Dual Gate MOSFET that is the receiver RF amp on receive and in the transmit mode will provide the 1st transmit amplifier stage following the SBL-1 transmit mixer. This circuit was developed by Ron Taylor in SPRAT 128 (GQRP Club). I have used this stage in several transceivers. This was an easy choice as it was one of the boards in the bin so easy to get working with the new transceiver. Recycling fits perfect with my limited time schedule.
 
Here is the heart of the new radio. Ahead and following this circuit block is the SBL-1's. This circuit uses voltage application to switch the direction of the signal path. The 2N3904/2N3906 combo used in this board are surface mount as is the other components and are known as the Plessey circuit which was found in EMRFD. The arrows show the direction of how the signal passes based on how the circuits are biased. There is no signal switching as such --it is purely voltage switching. This schematic shows the use of a single DPDT relay -- not two relays. The Z in/out of the filter is close to 200 Ohms so using a 4:1 step transformer is a close match. For those purists who will do the very rigorous calculations and conclude it is more like 170 Ohms, then a 13 turn winding tapped at 7 turns will get you there. Or as in this case alternatively you could use a 12 turn winding tapped at 6 Turns.

[ So OK 50 Ohms to 170 Ohms = 170/50 = 3.4. If you had a primary winding of 7 turns and square that you get 49 --if you multiply that by 3.4 you get 166.6. The closest square is 13^2 = 169, So 169/49 = 3.45 which is close enough for government work. Or you could be just lazy and make it 4:1.] 
 

Here is the Microphone Amplifier as laid out using Surface Mount. BTW this circuit was also used as a part of an audio pre-amp circuit and you will see the note 3. For the microphone application you will use the 200 NF connected to the SBL-1 through the audio low pass filter. This connection is in parallel with audio input to the audio amplifier. The 200NF is part of an isolation network.

 
 
 
5/28/2016. Earlier I mentioned the use of the single BF991 that is diode steered to be the Receiver RF amplifier on receive and the transmit pre-driver stage on transmit. This is show below. Two J310's could be used as a substitute for the BF991 as was done in the Simpleceiver project. The schematic below shows the J310's and for the BF991 it is a direct substitute. W7ZOI on his website, which I think may now be removed, did an investigation of the BF998 DGM as an amplifier and in the Source circuit had a 30 Ohm resistor -- this will really make the DGM run hot but works quite well. I am now back to the two LED's as AGC or ALC voltage could be applied to Gate 2 and you can visually watch the stage gain change based on the brighter/dimmer LED illumination. Color is good! Right now the voltage is fixed based on the 10K pot setting. Keep in mind the pot could be used as a manual RF gain Control on Receive. But unless you uncouple that pot on transmit via a small relay and the substitution of a fixed voltage, the Power Output would depend on your Receiver setting. In 2009 I used the approach where on Rx the gain was adjusted with a front panel pot but on Tx a fixed voltage was applied to set the stage gain on transmit.

 



Here is the audio amplifier schematic. Note the similarity to the microphone amplifier stage as mentioned earlier. We just borrowed what we made for the Simpleceiver project.



So now with just these few simple circuits we are getting close to having the new 40 Meter SSB transceiver be operational..

Now to the Si5351 ad the 128X128 TFT. This circuit has been used in several radio projects and to my surprise the code for the combo has been showing up in projects across the world. I have also received inquiries regarding the code. I strongly suggest that users learn about the Arduino in this application and resist plugging and playing the code only to end up by sending me an email saying your code doesn't work. It works for my use and if are doing something different then you will need to modify the code accordingly. I will gladly assist you but I do not do custom code development.

For a Band Pass Filter, I am using one that I designed in LT Spice for use on the Simpleceiver. I also included a plot of the simulation so that you can see the performance curve. This filter is now installed on the mainboard.



 
Here are some additional photos of the boards.
 


 
Listen to the new radio --hot off the press!
 
 
 
 Stay tuned for more exciting news.
 
73's
Pete N6QW