Posts
Alan Roe’s “At-A-Glance”program grids for RRI and the BBC
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Many thanks to SWLing Post contributor, Alan Roe, who writes: I have
attached a new “at-a-glance” programme grid of all Radio Romania
International English...
48 minutes ago
Nice job Bill! Looking forward to your next addition to this receiver. Forgive my ignorance but, what was the reason for halving the value of the cap in the amp? Thanks! Ted KE4NBB
ReplyDeleteThanks Ted. In the LM386, if you put a 10 uF cap between pins 1 and 8 you take the gain up to around 45 db. That is a lot. If you don't put anything there I think it is about 20 db. 5 db looks like around 30-35 db. At very high gain it can be hard to keep the amplifier stable -- it will break into oscillation and howl. So if you don't need all that gain, life is easier at lower gain levels. Bill
DeleteI meant "5 uF looks like around 30-35 db."
Deletejust for fun ... put the antenna after the filter and tune 75 & 20 at the same time!
ReplyDeleteThat would be fun!
DeleteInteresting that you like to listen on 75m AM through your SSB receiver. I often listen to those AM guys on the N1NTE KiwiSDR, there are some great conversations and quite a number of old and modded BC transmitters, and homebrew transmitters as well. Some of thise guys are hugely knowledgeable. It makes for good technical conversations.
ReplyDeleteWhat about extending Mythbuster with a second IF filter, and a true AM detector? -- 3HN.
3HN: I would, but to tell you the truth, the AM signals sound just as good to me just by zero-beating the carrier and listening to the lower sideband. I know the AM guys wouldn't like to hear someone say that, but I think it is true. Also, I think that is why the Drake 2-B has a max passband of 3.6 kHz -- they must have figured that users would be listening to just one of the sidebands (but the Drake does have a diode detector). 73 Bill
ReplyDelete