Build a sensitive shortwave receiver!

[VA7AAX]

http://www.arrl.org/tis/info/pdf/0009061.pdf

The above link will download a QST article by N1TEV for a very simple, sensitive shortwave receiver. This is a really nice construction project. One note for beginners: there are no special parts in this project. All can be bought at the local Radio Shack. The Variable capacitor can probably also be one of those plastic tuning caps. But it is better to use the actual mechanical ones. Probably get them at Ham Fests.

http://www.arrl.org/tis/info/HTML/regen/index.html

Above link is some extra notes from the Author N1TEV

Have Fun!

Ask questions...

BUT be sure to BUILD SOMETHING ! :)
73 de va7aax

[W4HAY]

These little sets are not only fun, but you actually learn stuff.

Here's one (http://www.lindsaybks.com/bks/vtrcvr/index.html) for the "hollow state" fans. Many OTs built sets like these back in their Novice days

[VA7AAX]

If I want to use a random wire antenna , then I may have to use a gimmick capacitor with the antenna to prevent overloading, right?

[N0WVA]

If I want to use a random wire antenna , then I may have to use a gimmick capacitor with the antenna to prevent overloading, right?
Yep....maybe two or three twists and thatll do it. But be sure to use a good ground. Else you may find hand capacitance bothersome.

[VA7AAX]

Thanks for the suggestion, N0WVA. Your suggestion works. I actually found two 10pF caps in my junkbox. So hooked 'em up in series between the antenna and cap.

Yep, I built my first regen. It is the same one as the one in the link. Really Love its operation!

And yeah, I do have hand capacitance problems.

Will post photos later for any beginners looking for a place to start..

[N0WVA]

Thanks for the suggestion, N0WVA. Your suggestion works. I actually found two 10pF caps in my junkbox. So hooked 'em up in series between the antenna and cap.

Yep, I built my first regen. It is the same one as the one in the link. Really Love its operation!

And yeah, I do have hand capacitance problems.

Will post photos later for any beginners looking for a place to start..

This is one of my favorite subjects....Its been a few years but I learned a lot of tricks with these simple rigs..But the best type of antenna coupling? Link coupled to the tank, maybe a turn or two....hooked to a dipole antenna. Always seemed to give minimal problems with maximum power transfer.

And congrats on the rig...working properly they can be amazing.

[VA7AAX]

here are some photos:

http://va7aax.googlepages.com/DSCN1129.JPG/DSCN1129-full;init:.JPG

and

http://va7aax.googlepages.com/DSCN1128.JPG/DSCN1128-full;init:.JPG


as you can see, The RF stage is just to the right of the coil. The black box to the right of the RF stage is the LM386. The pot behind the audio stage is the AF gain. The volume was okay only when I had it full gain. so I skipped putting it on the front panel. The Varicap was not mounted at the time this photo was taken 'cause I was experimenting with different caps to get the right range.

Hopefully, There arent too many mistakes I have made!

73 de va7aax

[N0WVA]

That , right there, is what its all about!

To get more audio, I use a fet or bipolar for a preamp right after the detector and remove the 10uf gain cap from pins 1 and 8 on the 386. keep in mind, when you add audio stages like that, you must also decouple them B+ line with a resistor and 10uf or greater cap to keep it from "motorboating".

My favorite amp is an LM380 with one stage of audio ahead of it, preferably an FET for low noise.

How smooth does it go into oscillation? Can you "sneak up" on it?

[N0WVA]

Also, one more tip on the antenna coupling. If you get too much coupling, you will have dead spots of regeneration over the range of tuning....In other words, regeneration should hold fairly steady over the range of tuning, only needing to increase regen a little as you tune downwards in frequency...If you experience spots while tuning where you need to max out the regen control only to have to back it way down further down the scale, then you might have too much Ant. coupling.....or perhaps too many turns of tickler on the tank, which usually makes it "pop" into oscillation.

[VK2TIL]

Well done; real "breadboarding" in 21st-century-style!! :)

[VA7AAX]

Thanks for the really great comments.

N0WVA, what do you mean by "Can you "sneak up" on it?"
I am new to the regen "club" and would like to know some jargon.
I did look up a few preamp circuits and saw this one ( http://www.qsl.net/wb3gck/pipsqk.gif , the preamp is right after the diode and 0.01uF cap.)

This has been a very fun project for me and will continue to build up and improve on this

[N0WVA]

That audio circuit would work, but its basic and will likely cause you some problems when combining it. The more gain you get, the more you need to use DC decoupling and rf bypass. The trick is to contain the different types of energy where they wont effect others.

Sneaking up on them means as you approach oscillation, the circuit retains stability where gain skyrockets, but the circuit still is not oscillating. This is the best point for AM reception. Some tubes decreased gain at this point, therfore making an even smoother transition. A good functioning circuit shouldnt "pop" or "plunk" , but smoothly "swoosh" into regeneration.
"Perculate" is also an old term for oscillation. The better circuits used a variable capacitor for regeneration instead of a potentiometer. This method is better because you are not changing the voltage, which effects tuning, and the device can run at maximum voltage all the time. This was called a "throttle capacitor". The gate resistor is called a "grid leak".

[VA7AAX]

Oh yeah, I can smoothly go into the "sweet spot." It's just fun to listen to shortwave stations while looking at your setup for the receiving it. Just amazing what a handful of components can do when they are connected in the right way.

Today I was rummaging through my junkbox (A little sidenote: Junkboxes have a snowball effect; when I started out in Ham Radio, it was maybe a couple of bits and pieces, just a couple of years later, whoa you could probably build a full multibander rig with the parts.)
Ok, so I was rummaging through my junkbox when I found an Audio amp I had built just for fun based on the TDA2822M(QRP Quarterly Spring 2008; functionally like an LM386 'cept it can work on pretty low voltages.)

So I was wondering whether it is better to build a preamp for this or could I just plug in my outboard amp?(I am suspecting that just using an outboard amp would just increase "noise".)

Thanks for all the help.

[AF6LJ]

I wanted to take a moment and tell everyone how much I have enjoyed this thread. I use to have one of those radio shack regen short wave radio kits. it was fun to put together and worked rather well.

I might have to build one of these.

[VA7AAX]

Yup, this is what ham radio is all about for me. Such projects are real fun. I enjoyed building the radio a lot and hope that others are inspired to build stuff like this!

[KB1LQD]

va7aax, It's awesome to see another young amateur operator building! The circuit looks good! Keep it up, let use know how it comes out!

[VA7AAX]

It works beautifully! Audio quality is excellent and yes, it does receive stations. I am now working on putting some finishing touches(no ham can resist those!)

Thanks and best regards

73 de va7aax

[KB1LQD]

I am now working on putting some finishing touches(no ham can resist those!)


Awesome! I love blinking LED's and spinning Motor Wheels!......


Just kidding! That's awesome, congrats, I'd love to be able to build as much as I was in the past but college is keeping me busy enough! Especially throwing a varsity sport on top of that.
Yes, we can never resist adding new features and such, take a look around and find more features! I may suggest building small "modules" that you can easily solder in and such so that you can try additional circuits. Maybe a new preamp, a filter, experiment with VCO's..... There are even kit's that you could add on that will read the frequency back to you in morse code. Basicaly, keep trying new things as the one thing I really learned through experimenting has been that I have learned more from my mistakes that most other things!

Congrats! Keep it up!

[WA8LGM]

Hi!! Looks like a lot fun. Think I will do this one. Let you know later on how it works out 73! de John N8ABD

[VA7AAX]

N8ABD : Great! let me know if you need any help. I can take voltage measurements,etc.

I received my Amateur QSO(20m) on a homebrew rig using this receiver!(before this RX, I had never really built a satisfactory RX and one of my "dreams"was to receive amateurs on a homebrew) I was really skeptical about this receiver too,I mean I received SW broadcast but I thought 100 watts might not be enough for this receiver's sensitivity, you know a one transistor rx with a random wire. Now I really believe that regens are super sensitive and that if you could live with some of the regen's annoyances, it is possible to make contacts with this.

I was just tuning and suddenly I hear duck quacking. I tried to set the regen into oscillation for receiving the SSB but I could not set it right(I know it's just my mistake, I will have to play to find its optimum position for oscillation)....... So guess what I did? I took one of those cheapie "all band shortwave" receiver and tuned around the 20m band for the "whoosh"(more like a "grunt" because the radio is not completely in oscillation) . As soon as I got that, I put on my headphones and now I could hear the quacking more like a tinny sound. I carefully tuned the All Bander for the correct sound and even it was drifting(I had to keep my hand continous on the knob). I was amazed at the homebrew ness and how effective even such a simple setup was for listening to 20m.

Thanks to everybody who helped me,

73 de va7aax

[N0WVA]

Oh yeah, I can smoothly go into the "sweet spot." It's just fun to listen to shortwave stations while looking at your setup for the receiving it. Just amazing what a handful of components can do when they are connected in the right way.

Today I was rummaging through my junkbox (A little sidenote: Junkboxes have a snowball effect; when I started out in Ham Radio, it was maybe a couple of bits and pieces, just a couple of years later, whoa you could probably build a full multibander rig with the parts.)
Ok, so I was rummaging through my junkbox when I found an Audio amp I had built just for fun based on the TDA2822M(QRP Quarterly Spring 2008; functionally like an LM386 'cept it can work on pretty low voltages.)

So I was wondering whether it is better to build a preamp for this or could I just plug in my outboard amp?(I am suspecting that just using an outboard amp would just increase "noise".)

Thanks for all the help.


Im not familiar with that amp, so Id just wire it up and see how it does....Glad the regen is smooth....I found this on youtube:

http://www.youtube.com/watch?v=pK2ikMNYRXo&feature=related

Thats how I started out, then the junkbox kinda took over the whole room!

[VA7AAX]

Hi guys,

I am going to be adding the fine tuning mod(in the article) so that tuning SSB/CW can b much more easier!

http://www.geocities.com/pa2ohh/07swrx1.htm
Here is another receiver which might interest simple-receiver-builders!
I suspect that the sensitivity might not be as great as the regen but it will be more selective.

[KB1LQC]

Hi guys,

I am going to be adding the fine tuning mod(in the article) so that tuning SSB/CW can b much more easier!

http://www.geocities.com/pa2ohh/07swrx1.htm
Here is another receiver which might interest simple-receiver-builders!
I suspect that the sensitivity might not be as great as the regen but it will be more selective.

Great job and it looks like you are learning a lot from the project!

[CT2JUT]

It works beautifully! Audio quality is excellent and yes, it does receive stations. I am now working on putting some finishing touches(no ham can resist those!)

Thanks and best regards

73 de va7aax


This project seems nice and very simple.

I wonder if you have any frequency stability issues (i.e. - when you approach your hands from the device).

I remember many years ago when i went for a similar project (although it was an FM BC receiver). I had many problems.

Super Regenarative receivers are very sensitive to weak signals, which is cool! So i could only run a short antenna even with decent decoupling.

Please tell me more about this receiver! :)


73 and Merry Christmas!

Miguel

[VA7AAX]

I do have hand capacitance problems. It helps a little to have a metal case(which I do) and I have a knob. Still it does change frequency a little but I "compensate" whenever I tune a station.

[VU3UBR]

hi evryone,
Im new to regen receivers and started doing this project. I could not source the proper parts. But tried some replacements. Instead of the air dielectric capacitor, i could get only a FM pvc gang capacitor. Instead of the LM386 audio amp, i used an old audio amp that i had, using TBA820. All im hearing is a strong buzz,probably the "motorboating" sound when i try to control the regeneration. But it goes off occasionally,though not periodically. I am sure that its the oscillation, but dunno wats the problem. I have a 24 inch whip antenna and have put a random wire for 15ft after that. Plz help me. Im eager to listen to the QSOs.

Thanking you,
Shyam,vu3UBR

[VK2HHS]

Charles Kitchin is certainly your man when it comes to regens. He’s taken the old designs and updated them for solid state components and improved remarkably the performance of these little beasts.

The simple ones are quite easy to build but there are a few of his more high performance designs out there too. A simple net search will find them.

I built my first regen from the following link, also a Kitchin design. Differing from the circuit in discussion here, it has a 2N2222 RF preamp which doesn’t really amplify much but rather provides a stable “coupling” to the antenna and really cuts down on stray capacitance problems and improves stability. This one also uses a reverse biased common diode as a fine tuning control and is well worth including in any regen build.

I highly recommend this circuit for those wanting to take the next step.

http://www.electronics-tutorials.com/receivers/regen-radio-receiver.htm

After this one, perhaps try Kitchin’s “High Performance” regen.

Once you’ve become addicted, as I did, go on to build a hollow state regen and then the 4 tube “Ultimate Regenerative Receiver” a design by Bruce Vaughan NR5Q.



Cheers all, VK2HHS

PS My regen is on the left hand side, next to the FRG-7. It tunes form about 3 to 9 mHz. I heard my first ever "numbers station" on this little rig. What a rush ............http://braincambre500.freeservers.com/Henrick%20third%20picture.JPG

[VA7AAX]

I am not sure what a "FM PVC gang" capacitor is.... Is it the plastic polyvaricons? If so, it should work, but you will have to increase the value of the capacitors for HF.
Are you sure you are using the TBA820 correctly? If the transistor is being asked for more than it can source, it won't oscillate.
All wires need to be as short as possible, look at the pictures posted in this thread.
Make sure you are using a "gimmick" cap between the antenna and the variable capacitor. It will refuse to oscillate unless you do so. Gimmick cap can be two wires with a few twist (not critical).

Motoboating is caused by low voltage, or oscillation. Don't turn the volume all the wap up, and make sure all wires are properly routed.

hi evryone,
Im new to regen receivers and started doing this project. I could not source the proper parts. But tried some replacements. Instead of the air dielectric capacitor, i could get only a FM pvc gang capacitor. Instead of the LM386 audio amp, i used an old audio amp that i had, using TBA820. All im hearing is a strong buzz,probably the "motorboating" sound when i try to control the regeneration. But it goes off occasionally,though not periodically. I am sure that its the oscillation, but dunno wats the problem. I have a 24 inch whip antenna and have put a random wire for 15ft after that. Plz help me. Im eager to listen to the QSOs.

Thanking you,
Shyam,vu3UBR