I used about 15 megs of grid-leak with a D-104 in the early 70s, and I was picking up a strong 9 Hz rumble that was probably from a nearby main road. The D-104 is a good choice for super-high Z inputs because it has a strong response peak around 3 KHz. This makes brighter, clearer audio, which improves things - especially with people listening on selective receivers.
Bacon (the old Bacon), WA3WDR Sent from my Verizon Wireless BlackBerry -----Original Message----- From: "Jim Tonne" <[email protected]> Date: Tue, 22 Sep 2009 11:07:19 To: Discussion of AM Radio in the Amateur Service<[email protected]> Subject: Re: [AMRadio] Microphone recomendation I have been lurking here and reading the discussion which seems to me to have reduced itself down to a kind of "my daddy is better than your daddy" kind of thing. The person who said the D104 microphone could be thought of as a voltage generator in series with a 500 pF capacitor hit the nail on the head! Exactly correct (although I thought it might be a *slightly* higher capacitance value). I have spent a few minutes with LTspice and made a plot which clearly shows what happens when you change the value of the load on the D104 microphone. With a 10 megohm load the -3 dB point will be right at 30 Hz. Please, fellows, take a quick peek at this plot: http://tonnesoftware.com/appnotes/D104loadTest.gif The bottom line of this note is that going higher than 10 megohms for a load is nonsense. Pure nonsense. - Jim W4ENE ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Our Main Website: http://www.amfone.net AMRadio mailing list Searchable Archives: http://www.mail-archive.com/[email protected]/ List Rules (must read!): http://w5ami.net/amradiofaq.html List Home: http://mailman.qth.net/mailman/listinfo/amradio Post: [email protected] To unsubscribe, send an email to [email protected] with the word unsubscribe in the message body. This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
