[AMRadio] Ranger Audio

[Brett gazdzinski]

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: amradio-bounces at mailman.qth.net 
> [mailto:amradio-bounces at mailman.qth.net] 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
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> 
> 
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