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Author Topic: First true homebrew project  (Read 11848 times)
WA8JNM
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Posts: 172




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« Reply #15 on: December 29, 2013, 07:22:47 PM »

Yes, Mike, I hear you. I just figured a receiver would be much more complicated.

Dave
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W0BTU
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« Reply #16 on: December 29, 2013, 07:43:33 PM »

I just figured a receiver would be much more complicated.

A superhet is, but not a regen. But if a transmitter interests you more, then by all means build that instead.

This is similar to what I made as a boy, except that mine had a third coil that the antenna was connected to:



These are just some examples I found in  a quick Google Images search:



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WB6BYU
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Posts: 13230




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« Reply #17 on: December 29, 2013, 07:57:46 PM »

Quote from: WA8JNM

...Dale (BYU), the circuit you suggested strikes me as much simpler compared than the QST circuit...




Simple is good, but sometimes added complexity provides better performance.  A lot of the added
circuitry of the Universal Transmitter provides improved key shaping.  Sometimes keying a crystal
oscillator causes chirps as the transmitter starts up:  the Universal Transmitter keys the oscillator
first (where the chirps happen) then keys the power amplifier after a very short delay - that way
the oscillator transients don't get radiated.  But it also requires some additional circuitry to key
the two stages at slightly different times.

With a 2-stage transmitter you can build the first stage and get it working, then add the second.
That's a good approach because you only have to debug one stage at a time.  The two directly
coupled transistors in the Pippen are a little more difficult, as neither will work properly without
the other in the circuit.  On the other hand, the Pippen circuit is so simple that it has a very good
chance of working properly to start with, and there aren't that many things that can go wrong
if you have to debug it.  If you choose to go that route, I can suggest some coil and capacitor
values for the output stage.  (You can also find cheap colorburst crystals that would allow you
to use the transmitter on 80m without having to order a custom crystal - there might not be
a lot of activity on that frequency, but it will allow you to test the transmitter while waiting
for the proper 40m crystal.)
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G3RZP
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Posts: 4540




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« Reply #18 on: December 30, 2013, 04:24:29 AM »

I never had any luck with differential keying - the VFO chirp was too long.
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W0BTU
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« Reply #19 on: December 30, 2013, 10:47:38 AM »

I little chirp never hurt anyone. :-)

I heard a chirpy CW signal about a year ago, and it made me smile. It was quite nostalgic, and brought back some old memories.

Now, if I started getting 589C reports from my Icom, that would bother me. But hey, this is homebrew. Let the chirping begin!  Grin
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KH2G
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Posts: 272




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« Reply #20 on: December 30, 2013, 03:01:53 PM »

I would suggest getting a copy of the Radio Amateurs Handbook from the 50/60's as plenty of circuits and the theory behind.
As far as layouts, you see that addressed in the handbook and add to that the kits you built and WHY they laid out the way they were.
Any rig can be made as clean and stable as you want the difference is the amount of dedication - Cheesy
Enjoy - I've been doing the thing for over 50 years and still enjoy
Dick KH2G
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W0BTU
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« Reply #21 on: December 30, 2013, 04:20:29 PM »

I would suggest getting a copy of the Radio Amateurs Handbook from the 50/60's as plenty of circuits and the theory behind.

Excellent suggestion!

I've built more than one project from the Handbooks in that era. Learned a thing or two while I was at it.

Over a period of up to 4 years, I actually wore out one of those handbooks that I checked out from the school library as often as they would let me.
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N3KXZ
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Posts: 77




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« Reply #22 on: December 30, 2013, 04:27:16 PM »

Even though I'm 60, I have much less experience than most of the guys here. I'd like to add this from my beginner's prospective:

Study and build a few power supply projects. You can use them for many of your future projects, they can be simple and still teach a lot.

Consider buying an oscilloscope. You can get a high quality vintage analog Tek scope for less than $100, and they will open up a world of learning that you can apply to your projects for years to come.

Read up on bypass and coupling capacitors.

If you don't already have one, buy a good quality soldering station.

If you are an ARRL member you can get copies of most any/all of the past QST project articles free and fast from the website. Many of the Handbook project chapters/articles first appeared in QST.

Keep a notebook of your project building and findings- it will save you time in the future and help reinforce concepts and real-life tidbits that you learned/discovered. Also, consider photo documenting your projects, however humble.

Keith
N3KXZ
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W0BTU
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« Reply #23 on: December 30, 2013, 04:39:21 PM »

Consider buying an oscilloscope.

The suggestions in your post were indeed all very good ones. But before a person buys a scope, he needs an accurate meter that will display at least voltage and current. I have more than one DVM here, and I use them FAR more often that I do my oscilloscopes. Even good brand new ones are not very expensive. And a beginner doesn't need an expensive Fluke brand DVM, IMO.

I got along just fine for many years building homebrew projects before I ever owned a single scope. And after I got the scope, I found that --for most of the things I was interested in-- I didn't need it as much as I thought I did. :-)
« Last Edit: December 30, 2013, 04:42:58 PM by W0BTU » Logged

WA8JNM
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Posts: 172




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« Reply #24 on: December 30, 2013, 06:22:35 PM »

Thanks for all these suggestions, my friends!  There is so much for me to absorb in this thread.  I think I am getting a flavor of how to start.

BTW, there is a new video on Youtube as to the various construction styles, which I found to be most helpful. It was just uploaded, I think, ad I watched it only this morning.  Given that there may be other beginners of scratch building who are reading this thread and who have similar initial enthusiasm, search for this in Youtube:  w2aew: "Electronic Circuit Construction Techniques".

Any comments on my earlier thought to build one more KIT, the NorCal 40A, while I read David Rutledge book about that build, "The Electronics of Radio"?  It obviously delays my first scratch build, but perhaps the education achieved that way would allow for a more successful later build.  Al, K8AXW, who has been graciously advising me offline after I telephoned him, thinks that may be a good idea.  Then, he suggests the first scratch build could be an amp for the two watts that the NorCal generates.

Dave
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N0NZG
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Posts: 122




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« Reply #25 on: January 04, 2014, 05:00:40 PM »

If you want to start building RF project and don’t have a scope you can’t beat a simple RF probe made with a 1n34a diode and about 3 other components.  This is a great home brew project  in its own right.  Google 1n34a rf probe and you will fine quite a few renditions of this  project.  Whats so great about it? This simple instrument will convert rf voltages into dc voltages that can be displayed on you multi meter. There are probability 101 uses for one and no shack should be without 1 or 2.  It’s only good up to about 60 RF volts so don’t hook it up to you 1kw amp.  I am experimenting with putting 2 or more diodes in series  so I can measure higher voltages ,however  that will degrade accuracy on the lower end of the range.  So it’s best to have more than one rf probe.  A dummy load makes a great afternoon project too.
73, Jeremy


http://n5ese.com/rfprobe1.htm ----- link to a good probe design.
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G3RZP
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Posts: 4540




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« Reply #26 on: January 05, 2014, 05:24:05 AM »

A really good RF probe uses a Philips EA52 or EA53 tube - there are 4 digit US equivalent numbers. The trouble is that those tubes are expensive and rare, but you can get a probe that will handle 100 volts at 1 GHz and 300 volts below 100 MHz, while presenting a load of less than 1 pF. They do need a high resistance load such as a VTVM  or these days, a DVM.

I seem to remember a Heathkit RF probe that used 3 gold bonded diodes in series to get up to handling 100 volts below 30 MHz. Again, for a high resistance load.
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KK4MRN
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Posts: 91




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« Reply #27 on: January 09, 2014, 08:10:06 AM »

As I stated, my ultimate goal is to build some RF device purely from scratch, using only a schematic.  I have built a few kits over the years, but it didn't seem as satisfying, or as educational, as I imagined a scratch build would feel.

I have bought kits, but I have decided not to use the pcboard they provide.  I use my own - this way it requires me to think about where to place the parts.  Plus, you could always modify the radio to do something else, such as, add an amp.   I buy the kits for sourcing the parts, instructions, schematic, etc.

I did not like the TRF radio schematics I found online or in some books, so I built my own.  I took a crystal radio for the AM broadcast band that I built which used a 1N34A diode and then added an audio amp which used a LM386 IC.  I found schematics online for both.  Yet, I figured out on my own how to hook them up.    Yet, it only picked up part of the AM broadcast band, so I modified the coil by making it smaller (less turns of magnetic wire) so I could pick another part of the band.  My battery died and I did not want to go to the store 1:00 in the morning before I could try it out.  So, I hooked it up to a noisy AC adapter to 9v.  Put an electrolytic capacitor to clean up the noise.  Yet, this affected radio.  Instead of moving up or down the AM band, it had shifted to 6 MHz and I picked up shortwave broadcasts.  I verified this via another receiver.   Now, that was surprising.

- Daniel, KK4MRN
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K8AXW
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« Reply #28 on: January 09, 2014, 08:46:38 AM »

Daniel:  Building is great fun and also a great teacher.... not only electronics wise but also teaches patience, observation (you learn to pay attention to how circuits are laid out in books, publications and online) and how to lay out parts on a perfboard or piece of PCB using the Manhattan method of component mounting.

If you make your own PCBs (without cheating and seeing how the store boughten board has been laid out) you're taking all of this to a whole new level.

One thing you are missing though.  That is the search for parts from various vendors.  Looking at a schematic, writing down the parts needed, categorizing them and finding them becomes a very interesting part of homebrewing.   

I've found that homebrewing has been the most interesting facet of ham radio for 57 years.  Homebrewing is becoming a lost art.

Al - K8AXW
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KL7CW
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Posts: 71




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« Reply #29 on: March 01, 2014, 09:06:03 PM »

I have been building home brew projects for over 60 years.  To maximize your chances of success these are my rules in order of importance:  1) ALWAYS build your project one stage at a time, and thoroughly test and even operate that stage on the air if possible before building the next stage.  One idea is to build each stage on its own board, then mount each board on a larger board.  Consider trying a different construction method on each board.  Try dead bug, perf board, glue on pads, etc.  After you get the whole project wired and working, you should even try rebuilding a module or two on a printed circuit board and see if that method interests you.  2) Early projects should be relatively simple.  Transmitters and receivers for 160, 80, or 40 meters are often easy to get working and lead length, circuit layout, and other issues are much more forgiving than at higher frequencies.  3) Buy two or three of each part.  After you get your big ugly breadboard project working, you will have the option of "hiding" it in a big box, or rebuilding it properly in a smaller enclosure.  Sometimes for audio, dc, or low frequencies I use longer leads than necessary for parts on my breadboard version, then clip the parts out when I rebuild the project.  This does not always work, since excessive lead length often ruins a circuit !
All of my early home brew projects involved separate transmitters and receivers.  After each was working, I had lots of fun on the air and did not care if I had to throw a switch or two to go from TX to RX.  Later I could work on how to make switching automatic, or build a transceiver.
           Have fun,      Rick  KL7CW  Palmer, Alaska
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