Building the Ceramic Direct Conversion Receiver -- Part 1 Introduction, Stages, Parts.

I hope many of you decide to build this little receiver.  With it, you can break into the ranks of those intrepid ham homebrewers who have actually built a receiver.  Today I'll begin a series of blog posts on how you might do this.  Of course, there are many ways of proceeding.  I will describe my method.

FIRST:  ALWAYS look at this receiver as a collection of stages. Understand what each stage does and how they all work together.   Build it stage-by-stage.  Proceed to the next stage only after you confirm that the stage you just built actually works.

I see this receiver as having four stages:

1.  Front end  (RF gain control, input filter, first RF amplifier).

2.  Mixer

3.  Ceramic resonator variable frequency oscillator (and buffer)

4.  Audio amplifier (consisting of four transistors and associated parts).

In the picture above you can see the four stages.   On the left side of the copper-clad board you can see the Front end: the input filter and the RF amplifier (transistor near the top).  Moving toward the center you can see the mixer stage (around the circular 1k trimmer potentiometer).  Below the mixer (near the big round hole in the Bud Chassis) is the Variable Ceramic Oscillator stage and its buffer amplifier. The right 1/3 of the board is taken up by the audio amplifiers.  Note the use of Manhattan pads throughout.    Click on the picture for a closer look. 

I think you should build the oscillator stage first. 

What you will need:   In most cases, you shouldn't buy individual parts for this receiver.  I won't be providing a BOM.  Here is what I think you should do.  If you do not already have a good stock of electronic parts, start developing one.  Buy assortments of parts, or at least several of each part that you will need.  I use e-bay, amazon, mouser, digikey.   The parts are out there.

-- Get an assortment of resistors.  1/4 watt resistors will do.
-- Get a bunch of .1uF capacitors.  You will use a lot of these as bypass caps.
-- Get a bunch of 2N3904 and 2N3906 transistors. 
-- Get a bunch of 2N2222 transistors
-- Get a bunch of MPF102 and/or 2n2819 FET transistors.
-- Get an assortment of small electrolytic capacitors.
-- Get some Zener diodes in the 6-8 volt range. 
You will need some trimmer caps (8-80pf work fine).  Some 1K trimmer pots.  and some other stuff.

Get some copper clad board.  Pete suggest this, or something like it. 
https://www.ebay.com/itm/18-pcs-4-x-6-CEM-1-060-2-oz-Single-Sided-Copper-Clad-Laminate-Board-PCB/311756276147?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

Try to avoid the cheap fiber glass boards.   I prefer single-sided, but double sided is OK too. 

You will need to cut the board.  Get some tin shears.  Mine look like big strong scissors.  Use them to cut your boards to size AND to cut the little isolation pads for Manhattan construction.

Crazy glue.  I kind of like Gorilla Glue liquid (not gel).

Small wattage soldering iron.  35 W or so.   Get a small fan to keep the smoke and glue fumes out of your respiratory system.

   I used a piece of scrap wood to get the variable cap into position. 

Here it is with my fancy Archer Dial.  I used a bit of copper clad board to finish the front panel 

and to support the audio gain control. 

Next time I'll write about how you might build the Variable Ceramic Oscillator stage. 

SolderSmoke Podcast #201 Santa, Storms, BUILDING A DC RX, SDR, uBITX

SolderSmoke Podcast #201 is available:  http://soldersmoke.com/soldersmoke201.mp3

9 December 2017

Santa Juliano

Forest fires, snow storms, and an earthquake. 

Santa arrives from Hyderabad -- uBITX in the house. 

Radio history.  First transtalantic amateur contacts. 

Bill's International Brotherhood Ceramic Discrete Direct Conversion Receiver Project. 
-- Goals -- Build your own receiver.  Really.  From scratch.  No cheating. 
-- How to get started.  Get parts and tools. 
-- Stage by stage. 
-- VFO first -- maybe build two. 
Bill built two already
-- Nephew is testing the first one. 
-- Polyvaricon limitations. 
-- Varactor limitations
-- Variable cap limitation.  
MEETING THE JULIANO STABILITY CRITERIA

Understanding the F5LVG mixer

Pete goes to the dark side with an SDR receiver. 
Pete's 800 Watt Amplifier gives him trouble. TRGHS. 

People in the News
Cliff Stoll -- Still Passionate about Electronics
Peter Parker -- VHF/UHF  By the Bay
Yardley Beers -- Early SSB with "The Black Rose"
John Kraus -- Moonbounce without the Moon. 

MAILBAG

Discrete Ceramic 40 Meter Direct Conversion Receiver in Action (Video) -- BUILD THIS THING!

I've been holding off on making this video until I improved the stability.  N6QW is vigilent!  I only did this video after certifying that it meets the Juliano Stability Criteria.  I had to dispense with the polyvaricon and go with an air variable. 

We will be talking about this on the SolderSmoke podcast next weekend.  I hope to put on the blog  a stage-by-stage discussion of how to build this receiver.  

The dial from HI8P and the knob from a SW receiver that Elisa gave me definitely add soul to this new machine.  

JOIN THE RANKS OF THE TRUE HOMEBREW RADO MAKERS!  BUILD A RECEIVER!  BUILD ONE OF THESE!  

Cliff Stoll -- Still Passionate About Electronics (Video)

I open Chapter 3 of my book "SolderSmoke -- Global Adventures in Wireless Electronics" with some quotes from Cliff Stoll:  "Where's the joy of mechanics and electricity, the creation of real things?  Who are the tinkerers with a lust for electronics?"  Well Cliff, that would be us! 

I'm glad to see in the (obviously) recent video that OM Still has not lost his passion for electronics. You guys will like this one.  Keep 'em comin' Cliff!

"The Black Rose" -- Yardley Beers' 1955 HB SSB Transceiver

I've been a fan of Homebrew Hero Yardley Beers W0JF for a long time.   Here is a link to previous posts on him: http://soldersmoke.blogspot.com/search?q=Yardley 

Yesterday I got a nice e-mail from Boulder Colorado about Yardley's very early SSB rig.  I'm guessing that the 4.7 MHz is a typo -- it might have been 3.7 and 14 MHz.   FB.  Thanks Mike

Bill,

 

Yardley Beers W0JF moved to Boulder in the early 1950's to work at the National Bureau of Standards (now NIST) laboratory.  There he headed the Time and Frequency Division, which maintains the atomic clock.  He later taught at the University of Colorado and Denver University.

 

About 1955 he homebrewed what, at the time, may have been the only SSB transceiver in the world.  It was built with individual transistors (no IC's in those days) and Yardley had to grind the crystals himself for the filter.  He enjoyed naming his radios and this one was "The Black Rose."

 

The transceiver ran at 4.7 and 14 MHz.  Its 1/2 watt output was fed to a home built amplifier.  The transceiver demonstrated the practicality and benefits of SSB in a world where AM was the voice mode.

 

In the year 2000 Yardley demonstrated this original, old SSB transceiver to the Boulder Amateur Radio Club by using it to make contacts with two club members.  Attached to this e-mail are a couple of photos.

 

73,

Mike W3DIF

Treasurer, Boulder Amateur Radio Club (BARC)

VK3YE QRP by the Bay Goes VHF/UHF

Peter Parker again hosted the VK3 radio amateurs.  This time the event fell on VHF/UHF Field Day weekend.   So Peter and his friends went up in frequency and up into SPACE!  

VK3HN has a nice blog post here:

https://vk3hn.wordpress.com/2017/11/25/qrp-by-the-bay-chelsea-beach-melbourne-25-11-2017/

Be sure to read about Peter's ankle manacles -- he apparently uses them to get a good ground (sea) plane while running pedestrian mobile on the sea shore. Peter is DEDICATED! 

Listening for Your Own Signals on the Long Long Long Path

I heard some guys talking about this on 40 SSB last night.  A very cool use of the bidirectional pattern of the W8JK beam. 
From: http://qrznow.com/the-w8jk-is-a-famous-and-effective-dx-antenna/

Round-the-world paths The bi-directional nature of this antenna makes it possible to discover open round-the-world paths, something not possible with a normal beam antenna. The technique used by Kraus is to rotate the beam slowly, sending short Morse code dots, with a full-break-in or QSK transceiver. The delay time for the signal to return is about one seventh of a second, so there is plenty of time for your transceiver to switch to receive mode. When you have found and peaked an open round-the-world path, call CQ, and you may be rewarded with DX anywhere along the path. Also, the question of Long-path and Short-path does not arise – you are transmitting on both paths at once, giving you a greater chance of catching the other station’s beam direction….

Videos of iPhone Box DC Receiver

These are just a couple of short videos that I made for my nephew before sending him this receiver. 

As you can hear, deafness is not a problem with this design!   I did make some frequency stability improvements after this video was made -- I think you can hear a bit of drift.  Still, not bad for a very simple circuit using a polyvaricon superglued to the back of a cardboard box.  

I'll post more videos of the second version of this receiver.  There are further improvements in frequency stability.  My goal:  "Juliano Si5351" levels of stable-ness.  

Polyvaricon Variations -- Polyvaricons Are Not all The Same

When I built the first prototype of the iPhone DC receiver, I just reached into my junk box and used a polyvaricon capacitor for the main tuning control. It was marked PL 051.  I was really pleasantly suprised at the stability of the Variable Ceramic Oscillator circuit.  I could tune the entire 40 meter band with complete stability -- Juliano levels of stability. 

By the time I put the second version into its box (see above), I used a different polyvaricon (the one pictured below).  It worked, but with this part the receiver drifted noticeably.  So this morning I pulled it out and put in a second PL 051 Polyvaricon.  Viola!  Eccolo!  Success.  Drift eliminated.  Rock stable.    

Has anyone else noticed variations like this in the stabilty of polyvaricons?  

The dial in this version is an Archer device that has been kicking around in my junkbox for more than 20  years.  I think it was given to me by my old friend Pericles HI8P -- this adds a tremendous amount of soul to this new machine).   The box is an old Bud aluminum chassis.  Man, this thing sounds great.  I will try to post a video soon. 

iPhone Direct Conversion Receiver with Variable Ceramic Oscillator

A while back Bob N7SUR got us talking about winter projects.  Receivers.  Of course, Pete and I quickly went down different paths.  Pete is making great progress with lots of interesting digital circuitry.  He is going over to the dark side. Check it out here: 

http://n6qw.blogspot.com/2017/11/21st-century-homebrew-sdr-ssb.html

I went with simplicity.  Extreme simplicity.  Direct Conversion (thanks Wes!).  Discrete components.  No chips.  Analog Oscillator.  40 meters -- monoband.   

Schematic updated 29 November 2017

There it is.  You can click on the picture to make it larger. Here is an outline of the circuitry: 

-- Single tuned circuit bandpass filter preceded by a simple pot that serves as a gain control. 

-- JFET RF amp

-- Singly balanced passive mixer inspired by F5LVG's RX-20 in SPRAT 100.  For the coil I used one of the many trifilar toroids that Farhan gave me. 

-- The local oscillator is the coolest stage.  I used a 7.37 MHz ceramic resonator and a circuit inspired by Miguel PY2OHH. With a polivaricon I can tune the entire 40 meter band. I put a reduction drive int here to make tuning easier. 

-- The AF amp is an op-amp free design.  It works well into ear buds or into a computer speaker. 

-- Perhaps in an effort to catch the attention of the younger generation, I built it into an iPhone box.  

Please let me know if you spot any flaws in the circuit, or see any places where it might be improved. 

More to follow.   This prototype is now in the mail, en route to my nephew John Henry who will be testing it for me. 

China and SETI: What Happens if China Makes First Contact?

Here is a really amazing article from The Atlantic.  It is very thought provoking.  Mind blowing.  Strongly recommended. 

You can read it here: 

https://www.theatlantic.com/magazine/archive/2017/12/what-happens-if-china-makes-first-contact/544131/

Or you can listen to a reading of it (like a podcast) here: 

https://soundcloud.com/user-154380542/what-happens-if-china-makes-first-contact-the-atlantic-ross-andersen

Thanks to Mike Rainey AA1TJ for alerting us to this. 

Jeff Murray's Grumpy Audio Guy from 40 meters

I've talked to this guy several times.  He usually waits until I'm testing a new rig.  

https://www.facebook.com/6sj7jeff/videos/10208309648978285/

I'm sure Pete has worked him too.