Replace variable capacitor with varicap

[Audioguru]

so he need demulator, sorry audiogurru i realy dont understand, why somebody can lie, is workinig?

thnx

Please post a link to the webpage that has this horrible circuit.

 

[michael1978]

Please post a link to the webpage that has this horrible circuit.

You are right .....

 

[rakhmatvaris]

just like michael1978, i am also interested in learning how to replace varco with varicap.
perhaps this is a good and successful example of replacing the variable capasitor with diode varactor/varicap

http://theradioboard.com/rb/viewtopic.php?t=6327






http://x01a4.net/dirc7/elec/am-fm-radio.htm



this video "TheAstro30" that managed to change 2 gang variable capacitor with varicap from this schematic

http://www.bowdenshobbycircuits.info/radio.htm

 

[Audioguru]

I see a few problems with the LM386:

 

[michael1978]

just like michael1978, i am also interested in learning how to replace varco with varicap.
perhaps this is a good and successful example of replacing the variable capasitor with diode varactor/varicap

http://theradioboard.com/rb/viewtopic.php?t=6327

View attachment 40636

View attachment 40635

View attachment 40634
http://x01a4.net/dirc7/elec/am-fm-radio.htm



this video "TheAstro30" that managed to change 2 gang variable capacitor with varicap from this schematic

http://www.bowdenshobbycircuits.info/radio.htm

View attachment 40641

thanks a lot

 

[rakhmatvaris]

I see a few problems with the LM386:

wow..thank you, i will try your tips

thanks a lot

this is a good article too "Replacing polyvaricon tuning for varactor tuning"

http://golddredgervideo.com/kc0wox/bitx20amods/varactormod.htm

youtube:

another good example of the varicap circuit and its explanation

https://electronics.stackexchange.c...-to-properly-connect-and-drive-varicap-diodes

 

[michael1978]

wow..thank you, i will try your tips


this is a good article too "Replacing polyvaricon tuning for varactor tuning"

http://golddredgervideo.com/kc0wox/bitx20amods/varactormod.htm

youtube:

another good example of the varicap circuit and its explanation

https://electronics.stackexchange.c...-to-properly-connect-and-drive-varicap-diodes

thanks mand, yesterday i make my one trf radio, so now is time to experiment, very cool tutorail

 

[rakhmatvaris]

thanks mand, yesterday i make my one trf radio, so now is time to experiment, very cool tutorail

yesterday i've tried it .... and it works
first, I use polyvaricon first. then i just use diode varicap. I do not know why the radio sounds more detail when using varicap, that's my opinion

 

[michael1978]

yesterday i've tried it .... and it works
first, I use polyvaricon first. then i just use diode varicap. I do not know why the radio sounds more detail when using varicap, that's my opinion

View attachment 40679
View attachment 40680

i gonna try also...;-)

 

[Audioguru]

"Detail" of sounds is high frequency response. When humans are young we can hear as high as 20kHz and CD players and MP3's produce it. FM radio goes to 15kHz and sounds good. But an ordinary AM radio MUST cut the 10kHz interference beat frequency produced by adjacent stations and ordinary interference between them so its frequency response cuts frequencies above about 3kHz. A TRF radio has only a single LC tuned circuit so its frequency response is determined by the bandwidth of the tuned circuit which is affected by using a varactor to replace a mechanically variable capacitor.

 

[aurelZ]

Back to first circuit.
It work as is given with 500pF air variable capacitor as MW TRF receiver.
if you wish to turn it as normal regen look into modifications.
This circuit can work on smaller voltages using 2 AA batt - 3V.