View Single Post
Old 4th Dec 2020, 12:34 pm   #7
FERNSEH's Avatar
Join Date: Mar 2005
Location: Gateshead, Tyne and Wear, UK.
Posts: 6,480
Default Re: System A Ch1 modulator using MC1374.

The attachments show an early ETF modulator. The example I have here required considerable modification before it would work.
The MC1374 was designed for negative modulation systems, that being the case a separate sync tip clamp is used to so that the sync tips can reference to zero modulation. An emitter follower is introduced between the input amplifier and the input pin of the MC1374. Seems that the IC demands a low impedance drive.
The carrier oscillators can be modified to crystal resonators.
Modulator will work on channel B4 frequencies.

Information about the MC1374.

Attached Thumbnails
Click image for larger version

Name:	ETF_Modulator_1.jpg
Views:	99
Size:	103.5 KB
ID:	221836   Click image for larger version

Name:	ETF_Modulator_2.jpg
Views:	87
Size:	103.1 KB
ID:	221837  

Last edited by FERNSEH; 4th Dec 2020 at 12:40 pm.
FERNSEH is offline   Reply With Quote