[N6QW] 2019 ~ Building SSB Transceivers

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N6QW

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2019 ~ Building SSB Transceivers

Posted: 09 Feb 2019 07:34 AM PST
http://n6qw.blogspot.com/2019/02/2019-building-ssb-transceivers.html

The Building of a SSB Transceiver ~ You can do it![In a few days (after
2/10) I will start publishing schematics for the Simple SSB on my website
at www.n6qw.com. Although it is doubtful that many (if any) would take up
the fabricating of this rig; there just may be one or two who have an
interest.]
Just the other day I was having a very nice QSO with Gene W6QFU and we
exchanged our station line up. W6QFU is lucky in that he just recently
acquired a very nice ICOM 7300 and has joined the ranks of perhaps over
100,000 other hams world wide who now have that rig sitting at the
operating position. Some would suggest it is an appliance rig; but at the
same time it is a great sounding rig that undoubtedly is very popular and
the current price point puts it in reach of many hams. Guess there is a
link to price point and the numbers in shacks around the world.
On my end --yes, yet another new rig just finished and W6QFU was the third
contact on that rig. So I was anxious to see how it held up. Well I might
add...

ARRL as previously reported will start a new podcast one month from now
called "So What Now?" A possible answer to that question (or perhaps it is
a challenge) is to suggest you build your own SSB transceiver. Trust me
what I am suggesting you build is not in the ICOM 7300 class; BUT it puts
out a respectable signal with a rock solid frequency stability and it is
something you built and can be built for about $100. [YMMV depending on how
much junk you have in the junk box.]
But let us go back in time to review SSB transceivers starting in the late
1950's and early 1960's. BOOM there was an explosion of technology in that
time frame starting with the Collins KWM-1 and KWM-2 (the cost --read a
years salary for most middle class working folk) to more modest rigs that
were less costly. Heathkit did much for the hobby in offering single band
transceivers that could be had for about $100. I remember being on Midway
island (actually two island Sand and Eastern Island) in 1963 where a fellow
Navy ham on Eastern ran one of those rigs into a 13 dB gain Rhombic antenna
pointed at the US. Everyone wanted to talk to him--firstly he was DX and
secondly that gain antenna took that 100 watts and made it look like more
than a KW (like 2KW and you can check the math [10*log(2000/100) = 13dB])
But even the simple Heathkit rigs involved some pretty complex circuitry to
receive and transmit a signal using common circuit elements.
There were many complicating factors in building a homebrew SSB rig in the
1950's and 1960's
Socketry --yes you had to do all of that metal bashing and mechanical
engineering to layout all of the tubes and components that had to be
affixed to a large aluminum chassisPower Supplies. You often required
Filament, Bias, LV, HV and control power to operate the rig. We are indeed
fortunate --12 VDC and we are there todayFront panel controls abound as
does a space reservation for the Analog Dial ReadoutSo there was much
involved aside from just a few schematics.

In todays rigs none of those issues exist as many circuit elements simply
solder to a few pads. Socketry is minimized so you can feel secure in
selling your set of Greenlee Chassis Punches at the next block yard sale.
You won't need them. A 12 VDC well regulated supply or even batteries can
run your rig. You only need to cut out a rectangular hole in the front
panel for your favorite display (LCD or Color TFT). If it is a touch screen
then that will reduce further the number of controls needed

Fast forward to today some 60 years later and building a transceiver is
much easier and uses far less components thanks to IC's, PLL's and
inexpensive commercial crystal filters. Let me take a moment to discourage
the use of homebrew crystal filters especially if you have not previously
built one, and two if you lack some pretty decent test gear. Sure you can
purchase crystals inexpensively but that is only 5% of the task. So reject
all of those claims that you only have to buy 5 crystals at 40 cents a
piece and you are there --you aren't! INRAD sells a nice 4 pole 9 MHz
experimenter's filter for about $30 and you can also buy 9 MHz filters from
the GQRP club for about the same shipped to you. Yes I do have several rigs
with homebrew crystal filters so I do speak with experience. But it is a
simple decision if you do not have that experience --buy the filter!

So lets talk a minute about the SSB transceiver architecture. and we'll
proceed first to the block diagram.





Many rigs today are bilateral or as some prefer bi-directional in that a)
signals can be routed in two directions through the circuit element and b)
because of (a) you can use that circuit element in both transmit and
receive.

Here is an example of one circuit element that I frequently use... a
bidirectional IF Amplifier Module as shown above. This module has four
transistors, a bunch of caps and resistors, two matching broadband
transformers, a crystal filter and a relay to bias parts of the circuit to
change the signal direction. The common 2N3904 and 2N3906 make up one
amplifier stage and following the crystal is a second identical stage. The
amplifier circuit was invented by Plessy and appears in EMRFD (just so it
has street creds). Here is what is happening .. with one bias condition the
two 2N3904's take on the amplifier role. With the alternate bias condition
the 2N3906's are doing the heavy lifting. This circuit is good up to about
the 6 Meter band and a single amp pair is good for 15 to 17 dB of gain.

Here are some notable items. This is a broad band circuit --there are no IF
transformers and there is nothing to peak or tweak. The resistor compliment
for a single amp stage is 22 Ohms, 2 X 100 Ohms,. 2X 680 and a 1K. For caps
-- six each 100 Nano Farad. The power source is actually 6 VDC but I run
mine on 8 VDC through a three terminal regulator. Add in two FT-37-43
matching transformers [19 Turns solenoid wound tapped a 6 turns. The 19
turns squared is 361 and the 6 turns squared is 36 --thus 361/36 = 10. So
this transformer matches the 50 Ohms of the Plessy to the 500 ohms on the
GQRP filter.]

Including the Linear Amp control ( another 2N3904) there are eleven
transistors and FET's along with two packaged ADE-1 Double Balanced Mixer's
an Arduino Uno R3 (because it was in the junk box) a 16X4 Seasick Green LCD
(also a junk box refugee). BTW I was looking at some 16x4 Blue White LCD's
--$8 shipped from the USA. Lest I forget the GQRP 9 MHz crystal filter. If
you use the INRAD it is a 4:1 match as the INRAD's are 200 Ohms.

This may be a good place to stop for now… but to whet your whistle:



Interesting note this front panel was cut out of the front panel that was
used for the 30 Meter CW transceiver that originally was a QRP Quarterly
article. I should tell you that I was encouraged by QRP Quarterly to design
and build this CW rig so it would appeal to those QRPer's who dominate CW.
I did as was suggested and did make one contact to prove it works . The rig
then went into the never to use again and possible use in other projects
bin. There it has sat for five years. Now is the time to use it!

The panel was reversed as it was double sided PCB. The Key is now the Mic
jack and where the analog dial was --it was cut out for the LCD. The audio
amp stage was cut out of the original main board. There are three empty
holes in the new panel. Above the red knob the audio gain control will be
installed and the hole in the lower right hand corner will house the audio
output jack. and the small hole next to the mic jack will be filled with a
bolt and nut. The original panel was 8 inches long and with a bit of
juggling and cutting material off of each end the size is now 6 inches wide.

Thank you Velocity Channel for giving me some really great ideas! Yes
Virginia having a CNC sure makes life a lot easier when you are fabricating
radios. The part that was cut off included the former part containing the
volume control and headphone jack. The two bolt holes nearest those were
enlarged to house one of the toggle switches and the new headphone jack.

New panel controls include MOX and TUNE button (red button), Volume
control, Main Tuning, USB / LSB Select and VFOA / VFOB Select, Microphone
Jack and Headphone Jack. Lest I forget the 16X4 LCD.



Below is the rig screwed down to the top of the work bench. In the very
bottom is the IF module, Audio amp and Microphone amp. To the left of the
IF module is the BPF and above the IF the bidirectional J310 amp and the
single 2N2219 feeding the IRF510. To the right of the IRF510 and the
microphone amp is the LPF. The junk in the center is my power buss and some
relays used for TR. The RCA plug/cord above the J310's is the linear amp
control. The "T" line feeds a 1K resistor into the Base of a 2N3904 with
the Emitter grounded at the collector goes to the control line in the
follow on linear amp.

Take a good look --aside from looking like crap --there are not many parts.
I did use it on WSPR and FT8 as well as a few SSB contacts. the future work
will involve some packaging to sanitize the look.
!



It is a shame that many hams think building a rig is too difficult. Drop me
a comment if you would like to see more detail on this project. Oh should
mention portions of the design are LT Spice simulations so there is solid
science behind the modules. These include the BPF, LPF, the J310
Bi-Directional amp, the 2N2219 driver stage and the microphone amp circuit.
Oh --the mic amp design is now the same design used in the audio pre-amp
stage. The circuits not simulated are the Plessy amps (from EMRFD) and
audio final stage LM386 and the IRF510.

I was asked a question about how the Simple Transceiver compared to the
Sudden Transceiver Project. There are two areas of comparison the first of
which is performance and the second the circuit elements themselves.
Performance is equal and thus I am pleased; but the circuit elements do
differ and the following explains the differences.



There is some circuits which are alike and some not so. Physically the
Sudden is a smaller footprint. Some circuit differences include:




The IF Module uses the Plessy amps and external DBM’s. The Sudden
using the NE602 provides the mixer stage and the balanced modulator on
the input side and the mixer and product detector on the output side.
The LO & BFO are switched whereas in the Simple SSB rig they feed the same
DBM regardless of T or R. The Sudden is a single pass whereas the
Simple is bidirectional.The simple SSB takes the pre-driver used in
the Sudden and makes it bi-directional so it is the Rx RF Amp on
receive and Tx pre-driver on transmit. The Sudden has a separate Rx RF
Amplifier stageOnly one BPF versus two in the SuddenThe Driver and
Linear Amp are the sameThe Mic Amp is the same but the Audio Amp
differentThe Sudden uses a Color TFT and Nano and the Simple the Uno
R3 and the 16X4 LCDThe LPF’s are the same.


Bottom line ~ not a lot of parts! For those who wonder this is not a Bitx40
repackaged. The Dual J310bi-directional stage configured as a Dual Gate
MOSFET has some interesting possibilities. The stage has a manual gain
control pot built into the circuit board so that stage gain can be
adjusted. This opens up some potential for adding AGC and ALC to this stage
so now we can add more additional refinements. One comment I made arising
from the Sudden Transceiver fabrication was the opportunity for
experimentation. With a change in the BPF and LPF the Simple SSB
Transceiver can traverse to other bands. A simple DPDT toggle switch on the
front panel could with 1/2 the switch controlling the VFO range and the
second half controlling 4 SPDT relays would switch in the proper BPF's and
LPF's for each band. One switch, four relays and a few more toroids and
caps and you are on two bands.



73's
Pete N6QW