Yaesu FT-290R Problem width packet

Problem width packet.
Ham Radio
There is a very "hard" de-emphasis in FT-290R. This can cause serious problems copying packet signals with some demodulator chips, eg. like the XR2211. By a common request, here is a modification of this popular TCVR for packet radio. It was made after a RADIO-REF article in several copies, by HA5OB, HA5DI, HA3MA and others. Increasing the intelligibility in noisy environment, this modification is also useful in FM voice communications.

You'll have to add only a serial RC unit, the R being 4.7 kOhm, and C being a 1uF tantalum capacitor. Put them between the pin 9 of IC Q1019 and the collector of transistor Q1021, with the positive leg of the tantalum capacitor to the collector of the transistor. These points can be found as test points, near to IC Q1019. Solder the components together, wrap some insulation around them, then solder to the test points mentioned. That's all you have to do! With this modification, FM reception will sound somewhat noisy, but much louder. GW1NGL NA7KR Kevin Roberts Ham Radio
GW1NGL NA7KR Kevin Roberts Ham Radio

Page last updated on 09/10/2012 by Kevin Roberts NA7KR a colection of Ham Radio and Electronic Information