Hi, can somebody help to change dual gate jfet in transistor

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hi, everybody, can somebody help? how to change this 40673, in transistor is that possible, because difficult to find dual jfet and also i undertsand better transist bjt and jfet than dual jfet this is the shematic1.jpg
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,

There are quite some dual gate mosfets.
I have used the BF980 and BF981 in the past.
40673
BF980
BF981
BF982

If you really want to change the circuit to a BJT circuit, you could have a look at this post of your other thread:
https://forum.allaboutcircuits.com/threads/hi-can-somebody-help-me-how-to-build-fm-mixer-thnx.152805/page-2#post-1312576

Inject the signal of the oscillator to the emittor of the BJT.

Bertus
Hi Bertus, is this circuits the same like he show me sir Bordodynov, can i use that circuit in place from this circuits with mosfet, i understand beter.
and more question, normal local oscillator must be from 88-108mhz( i mean with tuning), for fm superheterodyne
 
Last edited:

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hi Bertus, is this circuits the same like he show me sir Bordodynov, can i use that circuit in place from this circuits with mosfet, i understand beter.
and more question, normal local oscillator must be from 88-108mhz( i mean with tuning), for fm superheterodyne
Hello Bertus, i have just this question because now i understand, just local oscillator must 88-108mhz, like i read in internet ? correct
 

bertus

Joined Apr 5, 2008
20,063
Hello,

For an IF of 10.7 MHz, the LO must be 10.7 MHz higher or lower than the frequency to be received.

Read the section about the LO on this wiki page:
https://en.wikipedia.org/wiki/Superheterodyne_receiver

The frequency of the local oscillator fLO is set so the desired reception radio frequency fRF mixes to fIF. There are two choices for the local oscillator frequency because the dominant mixer products are at fRF ± fLO. If the local oscillator frequency is less than the desired reception frequency, it is called low-side injection (fIF = fRF − fLO); if the local oscillator is higher, then it is called high-side injection (fIF = fLO − fRF).

Bertus
 

Thread Starter

michael1978

Joined Jun 29, 2014
309
Hello,

For an IF of 10.7 MHz, the LO must be 10.7 MHz higher or lower than the frequency to be received.

Read the section about the LO on this wiki page:
https://en.wikipedia.org/wiki/Superheterodyne_receiver

The frequency of the local oscillator fLO is set so the desired reception radio frequency fRF mixes to fIF. There are two choices for the local oscillator frequency because the dominant mixer products are at fRF ± fLO. If the local oscillator frequency is less than the desired reception frequency, it is called low-side injection (fIF = fRF − fLO); if the local oscillator is higher, then it is called high-side injection (fIF = fLO − fRF).

Bertus
Thank you very much Bertus, i understrand, have i nice day...:);)
 
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