Jerald, would you shoot me if I answered, "Duct tape"?
Anyway, thanks for the excellent thread. I think I'm going to look for a
D104 mic. Until a few years ago, they were still available new.
You pointed out a very good problem, though. I have the same problem with
my Shure 444. The keyboard sits where the mic needs to sit, so I always end
up holding the 444 in my hand when I transmit.
Maybe the solution is to buy a cheap mic from the consumer audio market and
install the D104's capsule and amp inside it. There are plenty of stands,
goose necks, and booms available for these.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Jerry Volpe
Sent: Thursday, December 02, 2004 11:34 PM
To: tentec@contesting.com
Subject: [TenTec] Modified D-104 versus Heil on the Omni-VI.
Yesterday a ham friend of mine reminded me that I had some time in the
past mentioned seeing an article on modifying a D-104 for use on
lower-impendance mic input rigs... and that he wondered if I remembered
about the article. Well, fact is I had and that a few weeks ago I
actually stripped out the stock preamp in my circa 1980s D-104 and
installed my home-brewed version of the MPF-102 based amp detailed in:
http://members.cox.net/n4jk/d104.htm
My only modification to the circuit was the addition of a resistive
attenuator in the output as it was initially a bit too strong for my
Omni-VI Plus. In short I was more than pleased with the results with the
modified D-104 on my Omni-VI Plus. I had made recordings before and
after and there simply wasn't any similarities whatsoever. The stock
D-104 was tinny, thin and even somewhat distorted. The modified D-104
was full without being muddy and had the necessary peak around 2kHz to
add voice clarity.
Anyway, back to yesterday. I told my friend that I could do one better.
I asked him to meet me on 40 meters (he lives about 10 miles away in San
Francisco) and that I would demo the modified mic. Before I got to the
modified D-104 I began the on-the-air test with my newly installed
boom-mounted Heil Dual Element HM-10 (I had just used the Heil
microphone on the previous weekend for the SS SSB contest). My friend
immediately commented that my audio was really nice. I changed from the
HC5 to the HC4 element and he respoinded kindly. I changed microphones
to my Ten-Tec 700 hand mic and he said that it was nice but not
particulary distinguished. I then put on the modified D-104 and got a
rave review. In fact an easedropping ham friend of mine came on
frequency and echoed how great the modified D-104 sounded. Just to
illustrate the difference I placed a stock D-104 on and they cringed.
eBay is full of adds for these fine microphones that nearly all of us
totally ignore as 'CB fare' from the bygone AM days. Fact is they are
really a treasure to be rediscovered. The D-104 crystal cartridge needs
a 2-3 megohm working impedance to give its fullest audio response but
the versions with the built in amplifiers (several designs over the
years) just loaded down the mic element at the input and mismatched to
the newer transceivers on the output. A recipe for audio disaster. The
FET buffer detailed in the web article above provides a more correct
match to both ends and results in simply great audio with both my Omni-C
and my Omni-VI Plus. Now I no longer have my Jupiter so I couldn't test
it but the article's author created his mod for the Jupiter/Pegasus so I
have to imagine it does well there too. The Orion? Well, I am saving my
pennies but manybe someday.
So if you have one of these D-104 gems in your junk box and are not
afraid of putting a few cheap parts on a tiny perf board why not give
this a try.
My only complaint is that the modified D-104 is still a handfull and my
operating desk is centered around the pull-0ut keyboard tray so I have
to lean into the mic or hold it (Bah).... that is why I spent the money
on the Heil (but I got the boom from Radio Shack for $15 so that wasn't
too bad.). Now I have the quandry... The Heil is easy to use but the
modified D-104 just sounds better. Oh what to do? Anyone know how to
boom mount a D-104?
73,
Jerald, KG6TT
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