[EMAIL PROTECTED] (Robert Schenck) made an utterance to the drakelist gang ---------------------------------------------------------------------- I guess we have ll seen most of the various mods over the years. Personally, I tested the radio out extensicvely and came up with the following mods:
Replaced power supply board with a new board with largest filter caps for B+ and negative bias for minimum ripple. also has +/- 12 volt regulators for solid state circuitry. Replaced audio amp board with new one with a pair f LM 380 in a bridge output driving the original output transformer to still have anti vox work correctly. ANy bridge amp would do. LM 380 chaep and stable. Replaced If amp/ detector board with new board with 1496 product detector and precision AM detector I designed and on AM Fone website. Added a second first IF four pole filter in cascade with original. easily mounts on bottom oout of sight. First IF now 7.5 KHz BW and 85 dB stop band. Discoverd that sensitivity with 2509 Hz 2nd IF CW filter was not 10 dB better than with 2.4 KHz SSB filter as would be expected. was only 4 dB better. Problem was reltively low gain from ant to third mixer (6EJ7). Added a Mini-circuits MAR 3 at output of second switch that selects 2nd IF filter. made up for half increased gain by ading second cap to voltage divied signal to 50 KHz IF amp. The much lower noise figure of the MAR 3 reduced ovrall noise to be that of front end and now I get the 10 dB better sensitvity with 250 Hz filter. If you don't get a big noise peak with preseltor tuning then later stage noise is dominating. Love the radio now. ras __________________________________________________________________ Switch to Netscape Internet Service. As low as $9.95 a month -- Sign up today at http://isp.netscape.com/register Netscape. Just the Net You Need. New! Netscape Toolbar for Internet Explorer Search from anywhere on the Web and block those annoying pop-ups. Download now at http://channels.netscape.com/ns/search/install.jsp ---------------------------------------------------------------------- Submissions: [email protected] Unsubscribe: [EMAIL PROTECTED] - unsubscribe drakelist in body Hopelessly Lost: [EMAIL PROTECTED] - help in body of message Zerobeat Web Page: www.zerobeat.net - sponsored by www.tlchost.net ----------------------------------------------------------------------
