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Author Topic: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build  (Read 107152 times)

K8AXW

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #45 on: August 01, 2014, 09:48:29 PM »

Martin:  You're an artist with electronic parts.  You also have the ability to visualize what something is going to look like prior to doing it.  Similar to a "photographer's eye."  Few people have this ability.  Beautiful job.

One thing I've been doing, in reference to your "quick and dirty labeling on the rear panel."

I've been laying out my panels with Microsoft Visio. (But any graphics design software will work) When I get all holes and control positions laid out on the computer using horizontal and vertical lines..... label each control with the font and font size I want, I print off a copy using regular paper and taping it very tightly to the panel or apron.  I then mark where the holes are to go, remove the paper and do my hole drilling.

When it is all finished I then print another copy of the panel or apron without the vertical and horizontal lines but leaving the control labels, using photo paper.  I cut the photo paper to size and then cover the new panel label with clear acetate that has adhesive on one side and then trim the acetate.

I then mask and spray both the panel or apron and label with 3M rattle can adhesive, let both set for 2 or 3 minutes and then very carefully stick the label onto the panel.  I then take an Xacto pointed cutter to cut the openings or holes in the label and mount the controls.  Makes a pretty good label Martin.
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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #46 on: August 02, 2014, 01:20:46 AM »

Al: A year ago, I bought (or rather, I persuaded my mother to buy me as a birthday present) a complete "modern" panel-labeling system.

The brand name is "DecalPro" and their website is here: http://www.pulsarprofx.com/decalpro/.

It's the same principle as the "dry transfers" that you could buy in the 1960s, with the added (huge) advantage that you can design the labels on your computer. What you need is the basic DecalPro kit, plus an electric "laminator" -- which I bought from Amazon or Mouser, I forget which.

I have not yet labeled any of my front panels because both the receiver and transmitter are still a work in progress. Indeed I haven't even removed the Decalpro and laminator from their shipping cartons! Life is too busy, nuts!

For what it's worth, my local wonderful local electronics store sells Dymo labelers. I haven't checked them out but I suspect they are nothing like the Dymos of old!

Also, and this is rather weird, I have begun to think that the mark of a true homebrew project is that it doesn't have labels. For sure, in my projects so far, they are redundant: by the time you've finished building, fixing, altering and using something, you are so familiar with it that the labels are just eye candy!

We'll see.

Concerning the receiver: I have actually removed all of those modifications that are described earlier in this thread. This makes the receiver pretty useless on anything other than 40 meters, but for the moment I'm concentrating on 40m (monoband operation) and the receiver is "hot" on that band.

You are going to think I am completely nuts, but the current plan is to build a duplicate receiver that will be exactly the same at the original 1968 design, including the Bud chassis (I recently found the exact original chassis on eBay). This will be the "museum" receiver. I am in touch with the owner of the original Millen company (now located in Andover, MA) and we are trying to figure out a way to "re-create" the original unobtainium Millen knobs, since he still has the tooling for this. He still has the same size of knob in stock, but not the ones with the 280-degree numbered scales, only the 180-degree ones. This explains why, in the photos I posted in this thread, the receiver usually has National knobs.

I already have nearly all the parts for the "museum-quality receiver" because there were many duplicate components left over from the original build. Once this is done, I will feel "liberated" to "modify" the original build (the one constructed last summer) to my heart's content. I am rather keen to see how far I can take this simple design!!!

The "museum" version will indeed have front-panel labels. If you look at the original ARRL book from 1968, they labeled all the controls with dry transfers and that's what I will do, too!!!

This summer's birthday present from my mum is a Begali straight key, the Camelback, which was handed to me by Piero Begali in person, at the ARRL Convention in Hartford. Shhhhh! 1968 Novice Ham doesn't buy Begali keys.... I am not yet actually *using* it with my vintage Novice rig: the genuine Ameco K-4 is my stalwart key until I have completed my First QSO!

Ouch, I now have two telegraph keys and I suspect that once they have started reproducing, the collection multiplies uncontrollably! (One of my future projects is a hollow-state electronic keyer.)

73 de Martin, KB1WSY
« Last Edit: August 02, 2014, 01:45:22 AM by KB1WSY »
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K8AXW

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #47 on: August 02, 2014, 09:04:21 AM »

Martin:  Can you imagine any other hobby that is as mind or time consuming as ham radio?  You're a perfect example of why I have always said, "Ham radio is the greatest hobby in the world!"

I have a local friend who is into EME (Earth-Moon-Earth) communications and his work/attention to detail is similar to yours. 
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KB1GMX

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #48 on: August 02, 2014, 10:21:51 AM »

Martin,

There are many schools on homebrew construction.

One is design that works well, good mechanical and electrical layout,
pretty?  Well maybe not. 

Cleaver use of scrap, hardware store and other "junkbox" material.

Then there is all that plus doing all the panel and cabinet layout and work
required to get a first class better than factory look.  Over the years I've
seen many examples of that that are drool worthy.  I will admit the few
times I did that I spent more time on that on industrial than the actual
electronic design and assembly.  That makes for gear others want to
use or even lust to own. 

In the end a layout that makes the gear comfortably usable, safe and function well
is what its all about.

And true to the hobby its only 99 hobbies in one, electronic design, mechanical design,
assembly, industrial arts, and a long list of other to follow.  Oh, and very satisfying!


Allison
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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #49 on: August 02, 2014, 01:00:13 PM »

Al, Allison,

It is indeed a wonderful hobby. For those who like to build stuff, it is interesting to think about the meaning of that term "homebrew." There are almost as many different types of homebrewing as there are homebrewers.

I have started out on this bizarre thing of building almost exactly the same designs as found in ARRL books: not just the circuits but attempting to find the exact same components and adopting the same physical appearance.

But what I'm really looking forward to is reaching that point where I'm not just building stuff, but also largely designing it myself. Of course, almost no-one actually does this: even the best ham designers adopt sub-circuits and ideas from other sources. But you know what I mean.

One of the things I managed to lay my hands on is the entire Heathkit EK series of educational kits from the early 1960s. EK-1 is basic electricity, EK-2 is basic radio and EK-3 is basic transistors. I will be building all of that eventually (already done the EK-1). BTW, what I usually do is buy the assembled kit -- which is affordable -- and then disassemble it back into kit form, replacing some parts if necessary. For the instruction manuals, I buy the originals on Amazon.

It's funny how there are dozens and dozens of ham awards, for QRP, for CW, for whatever ... but as far as I can tell, there are no awards specifically for contacts made with homebrewed equipment. Of course, it can be difficult to define "homebrew," but surely rules could be written that would work OK.

You might be interested in this poll that I solicited some time back, asking hams: "Do you homebrew?" Of course the "poll" is totally unscientific but it has some value I think: http://forums.qrz.com/showthread.php?423663-Do-You-Homebrew.

73 de Martin, KB1WSY
« Last Edit: August 02, 2014, 01:03:04 PM by KB1WSY »
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JAHAM2BE

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #50 on: August 03, 2014, 08:24:20 PM »

But what I'm really looking forward to is reaching that point where I'm not just building stuff, but also largely designing it myself. Of course, almost no-one actually does this: even the best ham designers adopt sub-circuits and ideas from other sources. But you know what I mean.

I'm not sure I would agree with the "almost no-one actually [designs their radio circuits themselves]". I think it depends on which community you are considering. I am a member of a number of very lively discussion groups and mailing lists where many if not most of the members design their own receiver circuits (and I'm sure there are similar forums for transmitters too). Once you start to throw your own peculiar requirements into the design parameters (requirements like: it must use only the transistors I have in my junkbox, or it must be tuned with varactors, or it must use a Vackar oscillator, or it must run off of 1.2 volts), I think you'll quickly find that you have no alternative other than to design the circuit yourself! Circuit simulators are a real boon here, as you can quickly get your circuit constants in the right ballpark before physically building the circuit.

As an additional observation, the most active homebrew sites I visit seem to have a large number of non-ham members.

G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #51 on: August 09, 2014, 07:16:25 AM »

Today I thought of a neat solution for a "Mark II" version of this receiver.

You will recall that performance on 40m was good, but that for other bands, it was necessary to make (sometimes large) changes in the value of C9, which is connected between the source of Q1 (the FET regenerative detector) and ground.

My initial solution for this worked fine, but required mounting a selector switch on a new "back panel" (which allowed changing the value of C9) and I was never satisfied with the awkwardness of this system.

My new plan is to replace the 5-hole coil socket with a 6-hole one, and to replace the small Millen 1-inch, 5-prong coil forms with larger Amphenol 1.25-inch, 6-prong forms. Now, we can mount C9 inside the coil form, with one end connected to Pin 6 (which will be connected to Q1 source) and the other end of C9 connected to Pin 3 (which is grounded). This of course will allow "automatic" adjustment of C9 when the band is changed.

This will require a complete recalculation of the coils: the larger form diameter means that the number of turns of wire will change. OTOH, it was awfully tight inside those 1-inch forms and having the extra quarter-inch of room should make it quite possible to add that capacitor alongside the other capacitors that are already mounted inside those forms.

I have just checked, and the Amphenol forms will fit perfectly inside the receiver, even though they are bigger both in width and in height. Another advantage of the Amphenols is that they have a nice wide "lip" at the top which makes it easy to pull them out or push them into the socket. Finally, the Amphenols are built of transparent Lexan and it will be cool to be able to see the little capacitors inside the coils.

The only downside to this is that I have been hoarding those 6-pin Amphenols for my future "super receiver" (a double-conversion superhet to be built a few years down the road). OTOH, I have a stash of 12 of those forms, so there will still be 7 left over even if I use 5 of them now, and anyway I can keep looking for new ones to replenish the stash.

Once this "Mark II" coil configuration is in place, the only other key alteration is to move the antenna trimmer cap away from the "back panel" and mount it inside the cabinet, with its knob facing upwards just underneath the coil-change door. The trimmer usually only needs adjustment once (upon changing bands) so this is not a problem: insert coil, adjust trimmer, shut door.

I'll also be adding a one-transistor RF stage in front of the FET, not for amplification but to isolate the oscillating detector from the antenna and eliminate spurious emissions.

I'm not likely to do this "Mark II" version soon, because I'm currently focused on Getting On The Air in a monoband configuration (40m only) and the only point of "Mark II" is to deal with bands *other* than 40m.

73 de Martin, KB1WSY

« Last Edit: August 09, 2014, 07:39:49 AM by KB1WSY »
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KB1GMX

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #52 on: August 09, 2014, 08:33:41 AM »

If you add the rf amp it goes at point B after the BCB filter. 

There are many examples of such an RF amp and the
fet common gate version seen in other regen designs
would copy well.  Note the gate lead to ground must be short.


Allison
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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #53 on: August 09, 2014, 09:07:28 AM »

If you add the rf amp it goes at point B after the BCB filter. 

There are many examples of such an RF amp and the
fet common gate version seen in other regen designs
would copy well.  Note the gate lead to ground must be short.

Allison

I breadboarded this one a few months ago and it seemed to work fine with the receiver. It made no audible difference, but I guess the whole point is to achieve antenna isolation.



73 de Martin, KB1WSY
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G3RZP

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #54 on: August 10, 2014, 12:25:27 PM »

Martin,

you might find the 2 transistor regen in RCA Ham Tips, Vol 20, number 1, Jan-Feb 1960 of interest.

http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips2001.pdf

73

Peter G3RZP
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N0NB

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #55 on: August 21, 2014, 09:08:13 AM »

Outstanding work, Martin.

I do not posses the patience required to even embark on such a project let alone complete it.  I think a lot of that is due to a perception of not enough time to devote to something like this.  To achieve your level of craftsmanship is praiseworthy.  I know it is tedious work and I seldom did tedious very well.

Have you considered putting a video online of your receiver in operation?
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73, de Nate
Bremen, KS

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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #56 on: September 12, 2014, 03:06:54 PM »

To my astonishment, I find that although I created Chapter Nine of the receiver photo album more than a year ago (mid-Summer 2013) I apparently didn't post it here. I think I got confused after posting a few photos on QRZ, then forgetting to update the much more thorough description of my receiver project that I have given here on eham.

Since it's been a while, a reminder: the best way to view these albums is to click on the first photo and then click the "full screen" button near the top left of the window.

Chapter Nine, "Audio Amplifier, Cabinet and Speaker," is here: http://tinyurl.com/m4s55su.

(The work is still in progress.)

Outstanding work, Martin.
Have you considered putting a video online of your receiver in operation?

I would like to do a video eventually, but will need to buy a modern video camera first! I don't own one, or rather, mine is 25 years old and I'm not inclined to try to revive it. Does anyone remember "Hi-8"? The analogue-to-digital converter I was using to bring the video into FinalCut Pro died, which was a sure "sign" that it's time to buy a modern digital video camcorder!

73 de Martin, KB1WSY
« Last Edit: September 12, 2014, 03:42:54 PM by KB1WSY »
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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #57 on: September 13, 2014, 01:49:18 AM »

For those recently coming to this thread, here is a list of all the photo links in one convenient place, so you don't have to scroll through the whole eham thread:

Chaper One, "Project Description and Components": http://tinyurl.com/ktylgzn.

Chaper Two, "Metalwork": http://tinyurl.com/khckgdu.

Chapter Three, "Improving the Action of the Tuning Dial": http://tinyurl.com/lrpkoya.

Chapter Four, "Making the coils": http://tinyurl.com/lotc3ep.

Chapter Five, "Wiring the RF Stage": http://tinyurl.com/mubpkwk.

Chapter Six, "Completion and Testing": http://tinyurl.com/orqta39.

Chapter Seven, "Experiments to Improve the Set": http://tinyurl.com/kebfdwn.

Chapter Eight, "Building a 'Back Panel' and Improving Multiband Performance": http://tinyurl.com/q5vcls5.

Chapter Nine, "Audio Amplifier, Cabinet and Speaker": http://tinyurl.com/m4s55su.

73 de Martin, KB1WSY
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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #58 on: September 13, 2014, 01:51:17 AM »

This project is by no means over. Coming up, I hope:

Splitting the project in two.

(1) I will soon have enough components to build a "museum replica" of the original ARRL project, with no modifications whatsoever. This will use an original Bud chassis (not the LMC/Heeger modular chassis used in my first build), the original Millen dials (re-built to the correct specification by the actual Millen company, which is still in business) and, as we have discovered, the receiver won't work well on any band above 40 meters. It won't have a cabinet, because the original design didn't have one, either. I will label the front panel so that it is indistinguishable from the labeled receiver in the ARRL book, "How to Become a Radio Amateur," 1968 edition. This receiver will be "hot" on 40 meters and fun to use in "nostalgic" QSOs.

(2) There will be a duplicate receiver, using the existing LMB chassis, which I will now feel free to alter/improve to my heart's content, replacing and improving the temporary "back panel" experiment. I am very keen to see how far I can push this simple design, once I am freed from the (admittedly absurd!) constraints of staying "loyal" to the exact original ARRL design. This receiver will have the following additional features, at the very least:

(a) Six-pin Amphenol coil forms instead of the original smaller Millen five-pin forms. The extra pin will be used to allow for a different value of C9 on each band. Experimentation has determined that this is the only way to obtain decent multiband performance, beyond just "monoband" 40 meters. C9 is is connected between the source of Q1 (the FET regenerative detector) and ground.

(b) To reduce AC hum, the set will use the existing cabinet that I built, with the addition of a hinged door in the top left-hand end of the cabinet, to facilitate coil-changing.

(c) The set will have a preliminary RF stage in front of the regenerative detector, mainly to add isolation that will eliminate parasitic emissions from the antenna and frequency variations caused by the antenna being swung in the wind. An antenna trimmer and an RF gain control will be added to enable control of overload (regenerative sets are very easily overloaded; experimentation has show that the addition of the aforesaid controls is effective in dealing with this problem).

(d) There will be an extra audio stage to drive the speaker that's mounted in the top of the cabinet. Interconnections will be improved so that the transmitter's sidetone can be fed to the receiver and be audible in the headphones and/or the speaker. Transmit/receive switching will be added permitting easy muting of the receiver during transmit.

(e) In order to add this new circuitry, to make extra room on the chassis I am thinking of (i) eliminating the broadcast-band filter that is in the original design; in my experience so far, BC breakthrough at my location is only an issue on 160m, a band I have no intention of using, for the time being, and using the freed space for the new, one-transistor RF stage; (ii) removing the huge D-size battery holders underneath the chassis, which provide several years of power (I have never changed the batteries since last summer when the set was built!) and replacing them with C-size holders, which should still provide lots of battery life; this should free up enough extra room to build the audio amplifier, even with its big, 1950s-era transformers.

(f) I will eventually be building an audio filter for CW, but that will almost certainly be an external affair, so that it can be used later with other receivers.

I will also be building an entirely new, different receiver (my first superhet) at some undefined future time, and will start a new thread when that gets under way. This will be a tube receiver. It may be a variation of the "Novice Q5er" published in CQ magazine and authored by W6TNS, using a homebrewed crystal-controlled converter in front of a restored WWII-era military BC-453 receiver; or it may be something entirely homebrewed. Haven't decided yet.

Martin,
you might find the 2 transistor regen in RCA Ham Tips, Vol 20, number 1, Jan-Feb 1960 of interest.
http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips2001.pdf
73
Peter G3RZP

Peter: belatedly reading the article that you linked to, that does indeed look interesting, especially for portable operation.

73 de Martin, KB1WSY
« Last Edit: September 13, 2014, 02:43:32 AM by KB1WSY »
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G3EDM

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RE: "A Three-Transistor Receiver for the Beginner" ARRL 1968 -- Build
« Reply #59 on: September 13, 2014, 03:59:02 PM »

Busy day. I finally built the additional audio amplifier stage so that the nice speaker can be driven!

Chapter Ten, "Building an Extra Audio Amplifier Stage," is here: http://tinyurl.com/mnwd4n5.

I've been having fun listening to "shack-filling" audio from the speaker. It's not intended to replace the headphones, which I will still be using most of the time. Mainly, it's to make it easier to "show off" my radio to other people (including the future video I'd like to make). I'm also finding it quite fun to "monitor the ham bands" casually while doing other stuff in the shack; that's really only possible with a speaker.

73 de Martin, KB1WSY
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