Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Micro portable 75m AM receiver




 
The AM Forum
December 12, 2018, 09:25:12 PM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Micro portable 75m AM receiver  (Read 799 times)
0 Members and 1 Guest are viewing this topic.
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« on: November 19, 2018, 07:33:38 AM »

Hereís another project that Iím working on. Iím challenging myself to build things smaller. This idea Iím trying to fit in a 1.75Ē x 1.75Ē plastic container that I bought from the Container Store.

Itís powered from a small A23 12v battery. The direct conversion receiver uses an SA612 chip and an LM386 audio amp. The antenna transformer is wound on a Starbucks straw, but I could only fit enough turns for 11.5uh. It still should do ok.

Now, we can discreetly listen to 3870 KHz in the club without spooking the chics.

Jon

* Doc Nov 19, 2018, 05:36.pdf (696.75 KB - downloaded 56 times.)
Logged

DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1217


« Reply #1 on: November 19, 2018, 09:38:26 AM »

If you would like to build an All-Band receiver sometime check out the Silicon Labs
Si473X series;

https://www.silabs.com/documents/public/data-sheets/Si4730-31-34-35-D60.pdf


Phil - AC0OB
Logged

"What kind of Koolaid do they make you drink in the Physics Department?" Charlie Epps to Dr. Larry Fleinhardt, NUMB3RS   Smiley
Carl WA1KPD
Contributing
Member
*
Offline Offline

Posts: 1491



WWW
« Reply #2 on: November 19, 2018, 12:37:46 PM »

If you would like to build an All-Band receiver sometime check out the Silicon Labs
Si473X series;

https://www.silabs.com/documents/public/data-sheets/Si4730-31-34-35-D60.pdf


Phil - AC0OB
Could one add a BFO for CW? Does not look like it to me.
Thanks
Carl
Logged

"Okay, gang are you ready to play radio? Are you ready to shuffle off the mortal coil of mediocrity? I am if you are." Shepherd
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #3 on: November 19, 2018, 12:47:29 PM »

The purpose is for a fun AM project, not CW.

Jon


* 8B7D44BE-88E0-42CE-B9D4-CBA161CCDCD9.jpeg (2145.97 KB, 4032x3024 - viewed 67 times.)
Logged

Carl WA1KPD
Contributing
Member
*
Offline Offline

Posts: 1491



WWW
« Reply #4 on: November 19, 2018, 02:55:06 PM »

My question was more hypothetical and technical, not having worked with either of the chips discussed
Carl
Logged

"Okay, gang are you ready to play radio? Are you ready to shuffle off the mortal coil of mediocrity? I am if you are." Shepherd
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #5 on: November 19, 2018, 03:09:10 PM »

No problem. Iím sensitive to people pointing out my overuse of CW. I have built class E rigs, you know... 😉

Jon
Logged

PA0NVD
Member

Offline Offline

Posts: 404


Nico and Chappie (Chappie is the dog...)


« Reply #6 on: November 19, 2018, 03:57:30 PM »


Phil - AC0OB
[/quote]
Could one add a BFO for CW? Does not look like it to me.
Thanks
Carl
[/quote]

A direct conversion does mix the RF directly to AF, so it can receive CW, SSB and DSB. For AM it should be tuned exactly right like an SSB receiver receiving AM
Logged
Carl WA1KPD
Contributing
Member
*
Offline Offline

Posts: 1491



WWW
« Reply #7 on: November 19, 2018, 05:16:12 PM »

OK Thanks. I did not know it was DC. I have built several of those, a 40m meter one as a companion too the 1970s Tuna Tin 2 from QST and a nice little 75 meter one from maybe early 80s from QST. Fit the entire thing including speaker and batteries into a small Radio Shack project box.
Nice little rcvrs
Logged

"Okay, gang are you ready to play radio? Are you ready to shuffle off the mortal coil of mediocrity? I am if you are." Shepherd
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #8 on: November 19, 2018, 06:06:11 PM »

Not a lot of parts yet, but hereís the starting point.

Jon


* 07AF8210-BA28-435C-88C0-F7712626D296.jpeg (3183.24 KB, 3762x2823 - viewed 61 times.)
Logged

WBear2GCR
Member

Offline Offline

Posts: 3585


Brrrr- it's cold in the shack! Fire up the BIG RIG


WWW
« Reply #9 on: November 20, 2018, 04:04:11 PM »

Hereís another project ...<snip>

Now, we can discreetly listen to 3870 KHz in the club without spooking the chics.

Jon

Ummm... so carrying in that 12ft diameter 3" thick copper tubing for the magnetic loop antenna
will not attract any undue attention??
Logged

_-_- bear WB2GCR                   http://www.bearlabs.com
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #10 on: November 20, 2018, 05:52:12 PM »

Chics dig it.
Logged

N1BCG
Member

Offline Offline

Posts: 620


« Reply #11 on: November 24, 2018, 10:36:51 AM »

Making this regenerative would add a lot of gain and selectivity. For AM, set regeneration just below oscillation, for SSB/CW, just above.
Logged
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #12 on: November 24, 2018, 01:39:18 PM »

I just ordered the other parts that I need from DigiKey today. It's just a ha-ha project, maybe just a talking piece, but it won't take too long to put together.

Jon
Logged

ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #13 on: November 25, 2018, 08:50:07 AM »

And about the antenna, I remember my father showing me a trick back in the day. I had an kid's electronics learning board, and one project was a simple broadcast receiver. It had an antenna coil with a ferrite core built onto the board but it didn't work well. He just ran a wire from the wall receptacle's ground to the receiver and it worked great! I'm pretty sure he must've said not to plug it into the small hole one, but those neurons are lost to time.

Jon
Logged

PA0NVD
Member

Offline Offline

Posts: 404


Nico and Chappie (Chappie is the dog...)


« Reply #14 on: November 30, 2018, 06:00:30 PM »

You did infect me with this fun project Jon, which is highly appreciated, I had fun. My shack isn't ready yet, so I am limited to just a small experiment.
I did drive a schottky mixer TFM-2 (=SBL-1) with my DDS VFO, and added a transistor LF amp and an input tuning, which is absolutely required in DC receivers to keep the unwanted signals out
Works very nice, I heard many stations at 40.
I had to do it with a passive mixer. The customs in Costa Rica stole all my IC's, so I didn't have any active mixers left. But the TFM-2 gives an excelent IM


* DC Receiver.JPG (377.02 KB, 2592x1944 - viewed 33 times.)
Logged
ka1tdq
Member

Offline Offline

Posts: 1131


Massachusetts Democrat


« Reply #15 on: November 30, 2018, 06:42:44 PM »

That's great!  There's lots of ways to do everything, and I'm glad I sparked something.

To be honest, I scrapped my project.  I experimented with the tank circuit being plugged into the wall socket ground and I tried to make a working antenna.  It worked, but not really well at all. Tuning the tank circuit had little effect on what little I received. 

I was going to go further by using the ground prong as the ground plane for a loop antenna hidden in my duffel bag, but I didn't get too far with that.  This 24-FETter captured my attention and I haven't looked back.

But yeah, customs can be SOB's especially when they're thieves! 

Jon
Logged

Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone © 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.054 seconds with 18 queries.