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Author Topic: D-104 mic impedence matching  (Read 16456 times)

Posts: 5688

« Reply #15 on: March 30, 2011, 05:25:37 AM »

I got over moaning about the loss of 11 meters a long time ago. 

I have also always kept a legal CB rig of some sort or other in every shack as well. 

Don't know how many CB'ers I've Elmered over the years, but the "evangelism" of amateur radio suffers when folks on either side draw lines.  Homey don't play that.


Posts: 369

« Reply #16 on: March 31, 2011, 12:54:34 PM »

Hey, it is all just "radio tech" and if anything, hams were doing mic stuff long before CB was even a gleam in ole Al Gross' eye.  Al earned his amateur radio license back before WWII as a teen, kept it all his life. 

When I was a young ham, and AM was still hangin' on while the rich guys bought SSB rigs, an old ham gave me an old D-104 that was in really bad shape, the chrome was pitted through down to the brass in many places and the crystal element was shot.  But I loved the look of it and not having lotsa money for parts back then, I ended up putting a small speaker cannablized from one of the ubiquitous transistor handheld am radios of the day in there where the crystal element had been, along with the output transformer from the same little radio's circuit board.  High Impedance dynamic D-104 that drove my little DX-60 rather nicely.  One night a guy told me my audio had too much low end on it, so I pulled the little speaker back out and spray painted the cone with some cheap red krylon that was laying about, let it dry and put it back in there.  Nothin' to brag about, certainly, but I was on the air on the phone bands because of it.  Even back then I preferred the code key, though. 

One of the old Technician class old-timers in the amateur club said that he figured out why I like CW so much. 

Because it was the only mode that allowed me to stay on the air with one hand and EAT with the other. 

Actually, it was the beer in the other hand most times back then.  Okay, maybe a turkey leg on contest days. 

If you are old enough, you may recall when 11 meters was one of the ham bands...


Just a little fun natured ribbing.

It amuses me how many Hams got their start in CB but are ashamed to acknowledge it.

I started in radio (CB) Back in the late-mid seventies before it became the freak show it is today. back when they had such things as "coffee Breaks" to help out other CB'ers in need, R.E,A.C.T. and all the other fun stuff. You could actually drive into a town and get directions from a local.. yada yada yada.

Back then is when I first learned how to figure out Mic wiring, Solder coax connectors, replace bad transistors, build simple regulated power supplies and other projects, was introduced to schematics...30 years before I even thought of becoming a ham. Of course all this acquired knowledge carried over....

Hams didn't loose 11 meters, They gained a rompus room for potential newbies. Smiley

Posts: 1279

« Reply #17 on: March 31, 2011, 02:13:10 PM »

Back to the D-104 Mike with the T-UG8 stand. The following are some specifications of the D-104 Mike:

Original D-104 or T-3                  Crystal element
D-104C or 10C                           Ceramic
10DA, DN-HZ or DN-50                Dynamic
77L or 811                                Dynamic cardioid

Freq. response T-UG8                 flat 200 HZ to 20 KHZ

Output impedance                      5000 ohms or less

I have been using the D-104 with the T-UG8 stand for over 50 years. I have the model made in the 1970s, I use it now on my Yaesu FT-4540AT with excellent results. To check the type of cartridge you have open the mike head and it will be printed on the top of the mike cartridge. I would guess that just about every D-104 in use today will have a ceramic cartridge. I would imagine all the crystal elements are inoperative by now.

If you want complete information on the incredible D-104 mike it is still available for download on the Astatic web site. It has schematics, wiring diagrams and complete specifications on the different models and dates of the D-104 and the different stands available for it.

I was a CB operator after I had my Ham license and the 11 meter band became the Citizens Band. I used it to communicate with my wife at home from my car. It was very convenient until the band became so crowded that I could only hear my base when I was a mile or two away. I was originally able to communicate from 8 to 10 miles. My CB call sign was 2Q7421 (yes an FCC license was required when CB was first authorized). Then the 11 meter band opened up and everyone was calling to see how far they could talk. Linears came into play and a good number of CB operators used them to see how far they could talk. Everyone stopped getting the required license and the CB handle was born (This is "Big Red" calling anyone that can hear me). Then came the 55 mile per hour speed limit and just about every motor vehicle had a CB radio tuned to channel 19. (see any "Smokey's" (Police Hwy Patrol)  up the road). This is my nostalgia for CB radio. The loss of the band at this time presents no problem as the FCC opened 12 meters for ham use. The only problem I see, is I notice some truckers using the 10 meter ham band illegally for local mobile communication. The same way the CB band is supposed to be used. They do not have licenses and the same problem that happened with the CB band could happen on 10. The FCC does not have enough personell to monitor the 10 meter band and the vehicles being mobile would be very hard to locate and catch. We will just have to wait to see what happens with this.

I am now done with my rambling. I am old and old people tend to ramble.

Barry K2OWK                           

Posts: 6764

« Reply #18 on: April 02, 2011, 08:58:58 AM »

K2OWK - All:  I read this thread with great interest because a couple decades ago I bought my wife a D-104 "Golden Eagle" amplified mic.  (we were both into CB pretty hot back then - reasons irrelevant here)

I still have the mic on my radio desk and it still looks brand new.  Paid right around $120 for it as I recall. 

With that being said, I now wonder what, if any, modifications need to be made to it to work with my Kenwood TS-830s?

A Pessimist is Never Disappointed!

Posts: 268

« Reply #19 on: April 02, 2011, 09:23:46 AM »

K2OWK - All:  I read this thread with great interest because a couple decades ago I bought my wife a D-104 "Golden Eagle" amplified mic.  (we were both into CB pretty hot back then - reasons irrelevant here)

I still have the mic on my radio desk and it still looks brand new.  Paid right around $120 for it as I recall. 

With that being said, I now wonder what, if any, modifications need to be made to it to work with my Kenwood TS-830s?

Everyone tells me that my amplified D-104 will work with my TS-530S and 520S, so im sure that golden eagle will look great and sound great with your 830S..

Posts: 407

« Reply #20 on: April 15, 2011, 03:48:38 AM »

If my memory isn't faulty, the first 104s had crystal elements, but the later ones had ceramic elements. By this time, I would be surprised it any of the crystal elements were still functioning.

I think the 444 is a better sounding mike than the 104. In reality, I don't think the 104 is near as good a mike as legend has it, except for the looks. The only reason I have one is the looks. Smiley
  I have D-104s that make for excellent audio with boatanchor type rigs. Properly cared for they can last for decades. My favorite has a 1946 date on the still working crystal element (And working quite well ). Low heat and low humidity make for a lasting D-104. The key to good results with a D-104 has already been mentioned. The crystal element rolls off low frequency response sharply when it is worked into a low impedance load. The trick is to allow the element to see around 5 megohm loading.
 I collect microphones and have a very well rounded collection of some high end microphones but the D-104 still holds a good spot on the operating table.

 If you want to use the D-104 with a "modern" rig , look up the K7DYY mic pre-amp. It allows the D-104 to see a high impedance while providing a well buffered processed audio output for modern rigs. Works quite well with boatanchor vintage rigs too. A web search will turn up the K7DYY website.
« Last Edit: April 15, 2011, 03:53:08 AM by KG8LB » Logged

Posts: 108

« Reply #21 on: April 27, 2011, 11:15:41 AM »

If you want to use the D-104 with a tube (or FET) type rig with high impedance microphone input, use a straight D-104 without the amplifier in the base, or if your mike has one, disconnect and by-pass it.  But, if the grid resistor at the audio input stage is anything less than several megohms, replace it with 4.7 megohm resistor, the value of  load resistance recommended by Astatic ever since they first produced the microphone, before World War II.

A crystal microphone is electrically equivalent to an ideal a.c. generator with about a 500 pf capacitor in series, so you want it to work into a high load  resistance.  The mic will sound harsh and like a tin-can telephone if it works into something like a 50K or 100K load, not uncommonly found in "vintage" ham equipment.

Contrary to popular belief, the purpose of the amplifier in the base is not to make a "power mike" out of the D-104, but to allow the high impedance crystal element to work into the low impedance audio input, usually 150 to 600 ohms, of a modern rig. If you do not want to change out the 50K or even 470k input resistor, the amplified version would be the better choice, but that was never the best designed audio pre-amplifier in the world; a straight crystal element working directly into the first audio stage of the transmitter will sound much better, provided the input resistor that provides the load is of the proper value.

The ceramic element has lower output than the crystal, and is a little less "bright" in audio response.  The purpose of the ceramic element was for use in a high temperature and/or humidity environment, which may quickly destroy the standard crystal element.  The more durable ceramic element was never the standard element that came with the mike, but was sold for a while as an option.  The standard mic, until they stopped making them, always used the crystal element.

There are still plenty of crystal elements around providing faithful service, and these mikes are still plentiful at hamfests. If properly taken care of and not dropped or exposed to high temperature or humidity, they should  last for many decades, so it will be many more years before all the working D-104s with original crystal element are gone.  Of course, like any electrical component, a particular crystal element may unexpectedly fail at any time without explanation even under the best of care, and like anything else, you take a chance when you purchase a used one at a hamfest if you have no way to test it on the spot.

I use a D-104 myself, and have several working spares just in case. A fair hamfest price is about $35 for a good microphone with desk stand.  However, I use a homemade boom to hold mine, not the desk stand. I often get reports of near-broadcast quality with my D-104.
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