I think there were different D104 mic's, some had a crystal cartage, others had a ceramic one?
The crystal ones have a REAL high impedance, and want to look into a 2 to 5 meg resistor to ground at the grid. I also found the mic cord critical, I tried to replace mine, as it was on the short side, I only added a few feet more, of quality mike cable, but the audio sounded nasty, and I went back to the oem cord. Its real tricky to get a good frequency response out of such a high impedance, without getting a lot of hum. If you open up the transmitter audio, it will allow the passage of the 60 and 120 cycle hum coming from the mic amp. I run the mic amp filaments off DC, which eliminates the hum. I just add a diode in series with the filament, and an electrolytic cap. The size of the cap sets the voltage, the bigger the cap, the more voltage. I just experiment to get around 6 volts. The DC running the filaments does not have to be pure, the rough filtering seems enough to eliminate the hum. I run a 5 meg to ground on all the D104 rigs. With the audio opened up, and DC filament, and some feedback from the secondary of the mod iron to a low level speech amp stage, it can sound very nice and smooth, and I like the D104 feel. Plugging a D104 into any stock rig usually ends up sounding like a really cheap telephone.... I never had one, but I have been told the D104's with the amp built in are no good... Brett N2DTS > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Jack Schmidling > Sent: Tuesday, November 14, 2006 11:03 PM > To: Discussion of AM Radio in the Amateur Service > Subject: [AMRadio] Ranger Audio > > So I get my new D104 yesterday and spend a few hours removing the > un-needed junk from it and fire up for the NoonTime Forum > expecting all > sorts of kudos and no one can hear me. One guy that could said it > sounded tinny and crummy. > > So I switch to the Kenwood and they all say wonderful. > > I went of over the whole mic again, plugs, wires, grounds and fixed a > few things and converted it into a boom mic. I make another > contact and > he says tinny but could be his receiver... nice guy. He > suggests a few > caps to check so back to the bench with it. > > After looking around, I find that the mic wire goes directly to the > grid, no resistor divider and no input cap. I now see what > that strange > mess at the end of the shielded wire is... what is left of a > 1m resistor. > > I replace all this stuff and it still sounds crummy. Then I find that > R22 is missing in the cathode circuit of the output side of the first > audio. I replace this and it still sounds crummy. > > To establish "crummy" I set the mic near a nice sounding > radio and set > up a shortwave receiver in an adjacent room to listen to > while loading > up a light bulb. > > In all cases, the Kenwood with the handheld dynamic mic sounds better. > > The only thing (I have said this many times) that I see left as a > possible problem is C59a/b. These were resistors when I > started working > on it. I replaced these with 47uf and 67uf caps as that was > all I had > left at the required WV. They are supposed to be 15mf. > > I am not sure just what these do so the question is... could > these cause > a lack of lows in the audio? > > If not, any other ideas? > > js > > -- > PHOTO OF THE WEEK: http://schmidling.com/pow.htm > Astronomy, Beer, Cheese, Fiber,Gems, Sausage,Silver > http://schmidling.com > > > ______________________________________________________________ > AMRadio mailing list > List Home: http://mailman.qth.net/mailman/listinfo/amradio > Partner Website: http://www.amfone.net > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected]
