UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Ferrite rod antenna and RF amp for Valve radios

Argus25 · 6th Oct 2019, 8:26 am

By a stopper David means place a 47R to 100R resistor in series with the 10nF input coupling capacitor. Another place you can put it is in series with the transistor's emitter which will lower the gain a little and increase the stability.In that location a 27R would be OK probably. It will set the AC gain at about roughly 470/27 ignoring the the transistor's little re. Otherwise the gain is about 470/re , re is about 25/the collector current in milliamperes.

6th Oct 2019, 8:26 am	#4
Argus25 No Longer a Member Join Date: Oct 2016 Location: Maroochydore, Queensland, Australia. Posts: 2,679	Re: Ferrite rod antenna and RF amp for Valve radios By a stopper David means place a 47R to 100R resistor in series with the 10nF input coupling capacitor. Another place you can put it is in series with the transistor's emitter which will lower the gain a little and increase the stability.In that location a 27R would be OK probably. It will set the AC gain at about roughly 470/27 ignoring the the transistor's little re. Otherwise the gain is about 470/re , re is about 25/the collector current in milliamperes. Last edited by Argus25; 6th Oct 2019 at 8:31 am.