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 Post subject: One FET Regen
PostPosted: Mar Tue 11, 2014 3:22 am 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
Here is my design of a one fet regen. It has quite loud headphone reception ( low-z). Coil and variable cap covers about 3.5- 3.85 Mhz. Very usable for general work. I will eventually team this up with a Michigan mighty-mite. A two-transistor ham station.

I found that Radio Shack phones # 3300088 are cheap and much much more sensitive and louder than most other cheap phones. Going through a radio shack 1k to 8ohm transformer ( they still carry it). I also made a one-turn variometer for the tickler. With a variometer, you can eliminate the need for two parts, the usual pot or variable capacitor, and the large and bulky choke.


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 Post subject: Re: One FET Regen
PostPosted: Mar Tue 11, 2014 12:16 pm 
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Joined: Nov Mon 26, 2012 6:17 pm
Posts: 718
Location: Osyka, Mississippi, 39657
That looks great to me. Do you have a schematic for this rig. I just might try it myself.

sitn 8)

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 Post subject: Re: One FET Regen
PostPosted: Mar Tue 11, 2014 4:53 pm 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9203
Location: Santa Rosa, CA
Nice work.

I love that vernier drive... looks like it could be used to crank an old Ford starter! Is that WW II vintage?

Rich

PS: With a name like "J310" you must really like JFETs?


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 Post subject: Re: One FET Regen
PostPosted: Mar Tue 11, 2014 10:46 pm 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
sitn wrote:
That looks great to me. Do you have a schematic for this rig. I just might try it myself.

sitn 8)


Yes, I will draw one later this evening and post it. Check back later to have a look. :)


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 Post subject: Re: One FET Regen
PostPosted: Mar Tue 11, 2014 10:49 pm 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
Rich, W3HWJ wrote:
Nice work.

I love that vernier drive... looks like it could be used to crank an old Ford starter! Is that WW II vintage?

Rich

PS: With a name like "J310" you must really like JFETs?


I think the knob is WW2 era, but the vernier/variable cap unit I picked up at a hamfest. It has a ball vernier built into the shaft, then the brass gears slow it down some more. A little more than 8 turns stop to stop. It says its made in England, but I dont know what it was for originally , I wish I would stumble across some more!

I love FET's you guessed it. :)


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 Post subject: Re: One FET Regen
PostPosted: Mar Wed 12, 2014 1:30 am 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
Ok, here is the schematic. Ill gladly answer any questions.


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 Post subject: Re: One FET Regen
PostPosted: Mar Wed 12, 2014 2:10 am 
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Joined: Nov Mon 26, 2012 6:17 pm
Posts: 718
Location: Osyka, Mississippi, 39657
Thanks for the schematic. I think I can weed my way through it.

sitn 8)

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 Post subject: Re: One FET Regen
PostPosted: Mar Wed 12, 2014 3:33 am 
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Joined: May Tue 30, 2006 4:46 pm
Posts: 9203
Location: Santa Rosa, CA
Interesting approach to the JFET bias. Doe the LED pull enough current to light?

English verniers used to come from Jackson Bros.

http://jlkolb.cts.com/site/vernier.htm

Rich


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 Post subject: Re: One FET Regen
PostPosted: Mar Wed 12, 2014 10:46 am 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
Rich, W3HWJ wrote:
Interesting approach to the JFET bias. Doe the LED pull enough current to light?

English verniers used to come from Jackson Bros.

http://jlkolb.cts.com/site/vernier.htm

Rich


Yes, the LED lights and gets brighter when it goes into oscillation.

From that link, the picture in the lower left corner looks the most like the vernier/capacitor drive I have.


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 Post subject: Re: One FET Regen
PostPosted: Mar Wed 12, 2014 2:57 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1529
Location: Canyon Lake, TX
Have you tried a bypass capacitor with the LED? Does it make a difference?

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 Post subject: Re: One FET Regen
PostPosted: Mar Wed 12, 2014 9:23 pm 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
Ed Engelken wrote:
Have you tried a bypass capacitor with the LED? Does it make a difference?


I tried a .01 and a 10uf capacitor as a bypass. It made very little to no difference. The LED does a good job at bypassing RF and audio while setting the bias......

I also tried red and green LEDs and the green ones seem really close to optimum bias. Also, I noticed many others have been 4 or 5 turns for a tickler. This is way too much feedback for an FET. Also I stick with air core coils only, no toroids. On AM you can couple more antenna into the tank, but for CW and SSB, you want very light coupling. The signal will boost itself up in oscillation mode.....With light coupling on tickler, tank, and gate cap, the Q stays high.


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 Post subject: Re: One FET Regen
PostPosted: Mar Thu 13, 2014 6:03 pm 
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Joined: Feb Sat 08, 2014 7:43 pm
Posts: 67
Looks like a fun radio. Interesting that you got good regeneration control with a variometer. So the vario doesn't cause much frequency shift?


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 Post subject: Re: One FET Regen
PostPosted: Mar Sat 15, 2014 1:24 pm 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
pentagrid wrote:
Looks like a fun radio. Interesting that you got good regeneration control with a variometer. So the vario doesn't cause much frequency shift?


Very little frequency shift as I used only one turn and very fine wire. And it still will oscillate hard enough to mix against stronger signals to eliminate overload.


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 Post subject: Re: One FET Regen
PostPosted: Mar Mon 17, 2014 10:47 am 
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Joined: Oct Fri 08, 2010 10:28 am
Posts: 74
Location: Melbourne, Florida, USA
J310, I built the Michigan Mightymite for 40m.
http://www.nt9k.com/image/flmightymite.jpg
I think I'll dig it out and redo it for 80m and give your regen a try.
As I recall, the mightymite didn't do so well on 40m, maybe 80 will be better.
Thanks for sharing with us!

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 Post subject: Re: One FET Regen
PostPosted: Mar Mon 17, 2014 2:20 pm 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
NT9K wrote:
J310, I built the Michigan Mightymite for 40m.
http://www.nt9k.com/image/flmightymite.jpg
I think I'll dig it out and redo it for 80m and give your regen a try.
As I recall, the mightymite didn't do so well on 40m, maybe 80 will be better.
Thanks for sharing with us!


Im hoping to get my MMM together sometime in the fall, I have to put radio on the back burner for a while. Your website is awesome!


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 Post subject: Re: One FET Regen
PostPosted: May Tue 06, 2014 3:41 am 
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Joined: May Tue 06, 2014 3:35 am
Posts: 21
Hello there! New here. Been playing with crystal and simple transistor radios for many years. I also collect and restore antique radios.

Quesiton about this circuit please. How do you adjust the "variometer"? I see no adjustment on the coil or the schematic.

Thanks much!

Gabe


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 Post subject: Re: One FET Regen
PostPosted: May Wed 07, 2014 3:41 am 
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Joined: Mar Tue 11, 2014 2:54 am
Posts: 51
gabevee3 wrote:
Hello there! New here. Been playing with crystal and simple transistor radios for many years. I also collect and restore antique radios.

Quesiton about this circuit please. How do you adjust the "variometer"? I see no adjustment on the coil or the schematic.

Thanks much!

Gabe


Hi Gabe,

The single turn tickler coil is inside the tank coil on the cold end and rotates to increase/decrease regeneration. The small knob turns the shaft which I made from one of the wifes insulin syringes. The shaft passes through into the tank and rotates a smaller pill bottle form with the one turn tickler.

Also, I thought I would add that the miniature audio transformer (8ohm-1k) is a radio shack part number 273-1380


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 Post subject: Re: One FET Regen
PostPosted: May Wed 14, 2014 8:58 pm 
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Joined: May Tue 06, 2014 3:35 am
Posts: 21
J310 wrote:
gabevee3 wrote:
Hello there! New here. Been playing with crystal and simple transistor radios for many years. I also collect and restore antique radios.

Quesiton about this circuit please. How do you adjust the "variometer"? I see no adjustment on the coil or the schematic.

Thanks much!

Gabe


Hi Gabe,

The single turn tickler coil is inside the tank coil on the cold end and rotates to increase/decrease regeneration. The small knob turns the shaft which I made from one of the wifes insulin syringes. The shaft passes through into the tank and rotates a smaller pill bottle form with the one turn tickler.

Also, I thought I would add that the miniature audio transformer (8ohm-1k) is a radio shack part number 273-1380


Thanks for the reply! So in keeping consistent: pill bottle, syringe. ;-)

That's pretty nifty. I am guessing you used the plastic plunger piece?

I prefer to use a linear pot across the coil myself. Haven't played with a variable ticker coil. I have a radio kit that while uses a tickler for regen, varies the bias on the transistor. Not sure which is best.

Thanks!
Gabe


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