Forums :: NEW! Web Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives
Support This Site: Contributors :: Advertise


It is currently Nov Tue 30, 2021 10:49 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 1047 posts ]  Go to page Previous  1 ... 49, 50, 51, 52, 53
Author Message
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 7:42 am 
Member

Joined: Jan Sat 25, 2020 5:23 am
Posts: 799
Location: Colorado Springs, CO 80917
That's an unusual way to draw the LM386.
The usual output position on the triangle is the Vcc?
What did you have for the antenna length?


Top
 Profile  
 
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 7:48 am 
Member
User avatar

Joined: Dec Tue 26, 2017 1:30 am
Posts: 35
Location: MN
Here it is on the breadboard

Attachment:
Screenshot 2021-07-06 014803.png
Screenshot 2021-07-06 014803.png [ 359.34 KiB | Viewed 492 times ]

_________________
Dan


Top
 Profile  
 
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 7:52 am 
Member
User avatar

Joined: Dec Tue 26, 2017 1:30 am
Posts: 35
Location: MN
hwhall wrote:
That's an unusual way to draw the LM386.
The usual output position on the triangle is the Vcc?
What did you have for the antenna length?


Used the "PCB Express Plus" software they didn't have a LM386 in the database oddly enough, so I modified an existing DIP-8 part.

Ant length is about 5.5 Ft

Edit, I have a 33pF in line with my variable, so that' with about 40 pF on it.

_________________
Dan


Top
 Profile  
 
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 8:30 am 
Member

Joined: Jan Sat 25, 2020 5:23 am
Posts: 799
Location: Colorado Springs, CO 80917
Quote:
I have a 33pF in line with my variable, so that' with about 40 pF on it.

You mean 33pf in parallel with the variable, right? In line sounds like series, which would reduce the capacity, of course.

Looks like a major change in RF filtering between the LM386 & the OSC, more inductance & bypass caps, too.

I assume L2 & C9 may need tweaking if other than 1000Khz OSC is used instead.


Top
 Profile  
 
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 8:32 am 
Member
User avatar

Joined: Dec Tue 26, 2017 1:30 am
Posts: 35
Location: MN
Here is something from my last one:

Attachment:
Screenshot 2021-07-06 023041.png
Screenshot 2021-07-06 023041.png [ 326.48 KiB | Viewed 490 times ]

_________________
Dan


Top
 Profile  
 
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 8:38 am 
Member
User avatar

Joined: Dec Tue 26, 2017 1:30 am
Posts: 35
Location: MN
hwhall wrote:
Quote:
I have a 33pF in line with my variable, so that' with about 40 pF on it.

You mean 33pf in parallel with the variable, right? In line sounds like series, which would reduce the capacity, of course.

Looks like a major change in RF filtering between the LM386 & the OSC, more inductance & bypass caps, too.

I assume L2 & C9 may need tweaking if other than 1000Khz OSC is used instead.


Correct on the cap. Not sure on the Osc. I have a 1.2288 but never use it due to the earlier mentioned oscillation. Have tried literally every value of every part, within reason and sometimes not, in that config including versions of the 386 (8 ohm and 32 ohm "4" version) but not the OSC.

_________________
Dan


Top
 Profile  
 
 Post subject: Re: LM386N MK-XI BCB Transmitter
PostPosted: Jul Tue 06, 2021 8:43 am 
Member
User avatar

Joined: Dec Tue 26, 2017 1:30 am
Posts: 35
Location: MN
Retrotube wrote:
hwhall wrote:
Quote:
I have a 33pF in line with my variable, so that' with about 40 pF on it.

You mean 33pf in parallel with the variable, right? In line sounds like series, which would reduce the capacity, of course.

Looks like a major change in RF filtering between the LM386 & the OSC, more inductance & bypass caps, too.

I assume L2 & C9 may need tweaking if other than 1000Khz OSC is used instead.


Correct on the cap. Not sure on the Osc. I have a 1.2288 but never use it due to the earlier mentioned oscillation. Have tried literally every value of every part, within reason and sometimes not, in that config including versions of the 386 (8 ohm and 32 ohm "4" version) but not the OSC.


Notes from my first build that could do both:
"Running it on 6 AA batteries (9v). The LED is running on the 9V. Has a 220uh and 330uh L2 and works with a huge range of antenna sizes. I could have used just a 270uh with the 5-100pf tuning cap but antenna length was limited to about 6ft max at 1228 MHz and 2ft minimum at 1000 MHz while still being able to peak the antenna. A 40in antenna was perfect for a 270uh L2 peaking at about 33% and 66% of the capacitance range for 1228 MHz and 1000 MHz."

_________________
Dan


Top
 Profile  
 
Post New Topic Post Reply  [ 1047 posts ]  Go to page Previous  1 ... 49, 50, 51, 52, 53

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 5 guests



Search for:
Jump to:  




































Privacy Policy :: Powered by phpBB