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[Articles Home]  [Add Article]  

Transistor Radios and D-104 Microphones

James (N8NSN) on March 12, 2011
View comments about this article!

How to get good audio characteristics from an old Astatic D-104 on a modern transistorized rig.

Experimenting with different peripheral ham radio equipment has opened the door to a lot of education. In the learning process it has been found that some older equipment is not compatible with newer gear. One of the things we always strive for when using voice modes is keeping the audio ineligible and not tedious for others to listen to.

The old classic Astatic D-104 microphones were great sounding mics on the old boat anchor tube-type rigs. This was because the impedance of the D-104 head is in the order of several thousand ohms. The responsiveness of the tube type audio input circuits facilitated a great impedance match to the D-104. However, in the newer transistorized rigs, these audio input circuits leave the D-104 sounding very "tinny", at best. It's not because the crystal type element of the D-104 doesn't have the ability to "hear" any low end in the human voice characteristics. It is directly a result of impedance mis-matches between the microphone element and the radio's audio input circuitry.

For example, here is a short list of low end roll-off stats for the input of audio circuits when using a D-104 microphone element:

100 k = roll-off @ 500 Hz
500 k = roll-off @ 250 Hz
1 meg = roll-off @ 100 Hz
4 meg = roll-off @ 30 Hz

Information was sent to me from a good friend, Joe ( K2PSI ). Along with a couple dollars worth of parts the schematic was sent with the preceding roll-off statistics. I have reworked the schematic drawing for placement in this article. So, it will be easier to read.

The way this works is a field effect transistor (FET) p.n. MPF 102 is placed in a common source configuration. The D-104 cartridge sees a 2.7 megohm load impedance. The 1 k source resistor provides the proper load impedance to the rig with transistor audio input parameters. The 1 mH and 100 pF capacitor combos are used to filter any RF that may be picked up by the D-104 element or interconnecting wires. The voltage required to power the FET is supplied at the VDC pin of many modern rig's mic connector. (a voltage anywhere between 4 and 14 volts +DC works well) If your rig does not have a voltage out pin on the mic connector, a nine volt battery can be used.

This circuit works very well with the Ten Tec Jupiter, here in the N8NSN shack. Certainly other transistorized rigs may benefit from this circuit in combination with a D-104. An old defunct jewelers magnifying lamp served very well as a boom for the mic head. The cavity which once housed the transformer for the fluorescent circular tube, now provides the perfect place for the home brew circuit board of the D-104 requirements.

This is the circuit inside the transformer cavity of the old defunct jewelers lamp. As you see the circuit could easily fit in the base of a D-104's T-UP-9 stand base. Here, the circuit board was drawn, cut, and mounted on a couple of 3/4 inch metal stand offs. This also provides the means of shield/ground for the entire apparatus. The circuit is small enough that it can be mounted on bread board, wrapped in some kind of insulator and stuffed in any available containment unit.

There you have it... The old D-104 is back in the line up. Fabricating the means you choose, should you decide to try this, for making the old D-104 a part of the modern shack – how to connect it in a convenient operating position and such – will be left to you. The photos here were provided as a means of size comparison. The defunct jewelers lamp was only a matter of convenience coupled with a desire to not have any desk microphones lingering around on the desk. My hope is that we all continue to grow in the amateur radio service. There is something for everyone from the plug and play operators, experimenters, builders, to the design and fabricate types. The main thing is... HAVE FUN !

Here is a recap on all the parts you need to build this awesome little circuit:

3) each of 1 mH inductors
3) each of 100 pF
2) each of .01 uF
1) each of 2.7 megohm
1) each of 1 k ohm
1) each of 220 ohm
1) each of 1000 uF @ 15 V
1) each of MPF 102 FET

The 13 parts, some sort of circuit board, a dab of solder, and a whole lot of fun.

Member Comments:
This article has expired. No more comments may be added.
 
Transistor Radios and D-104 Microphones  
by K6JPA on March 12, 2011 Mail this to a friend!
Nice job with the schematic and photos. Thanks for sharing your project!
 
Transistor Radios and D-104 Microphones  
by KB2DHG on March 12, 2011 Mail this to a friend!
FANTASTIC Now I know what I am going to do with that extra D-104!
 
Transistor Radios and D-104 Microphones  
by KC2KCF on March 12, 2011 Mail this to a friend!
The same schematic with an identical description can be found here: http://members.cox.net/n4jk/d104.htm

Can't help but wonder who is plagiarising from who?
 
RE: Transistor Radios and D-104 Microphones  
by K2BEW on March 12, 2011 Mail this to a friend!
It was never claimed by the author that it was his original design. In fact he clearly stated it came from his friend and we don't know where the friend got it from, perhaps the other website. That is not plagiarism.

According to the Merriam-Webster Online Dictionary, to

"plagiarize" means

to steal and pass off (the ideas or words of another) as one's own
to use (another's production) without crediting the source
to commit literary theft
to present as new and original an idea or product derived from an existing source.

No he did not clearly identify the original source but we have to assume he did not know it to give proper credit since it came from his friend.
 
RE: Transistor Radios and D-104 Microphones  
by KC2KCF on March 12, 2011 Mail this to a friend!
Don't get me wrong - I don't accuse the author of this article of plagiarism. I do not know who copied from who, with or without permission, etc. so it would be premature to judge.

But something does look fishy. Plagiarism is, at least in the field of scientific/engineering publishing, almost unforgivable (on almost the same level as forging data). A student might be expelled from university from this, and degrees/doctorates have been stripped from plagiators. (For a recent case, look at Germany's ex-defence minister.) Beyond academic and ethical issues, there are also legal issues (copyright violation/piracy) that should not be overlooked...

I just think it would be good if the author could clarify.
 
Transistor Radios and D-104 Microphones  
by WU8P on March 12, 2011 Mail this to a friend!
Great article. I thank James for the info. I don't see the need to question Jame's ideas or methods.
I don't think Jame's is looking for fame and fortune on a E-Ham article.
 
RE: Transistor Radios and D-104 Microphones  
by W4FCC on March 12, 2011 Mail this to a friend!
Really?

A clear and helpful article and this is the response? Things such as this keep people from writing articles for this website.

There's not much new under the sun, especially with respect to D-104s-- and the author states he got the information from another source. This is ham radio, not some academic thesis. This article clearly lays out what you'd have to dig through QST archives and the like to find, and will be helpful to a lot of people who may be new to the hobby.

You don't like this approach-- OK, what's -your- idea for impedance matching ceramic/xtal mics to solid state rigs. You do have an original idea on this, right?
 
RE: Transistor Radios and D-104 Microphones  
by AA4PB on March 12, 2011 Mail this to a friend!
I submit that that the RF bypass capacitors are on the wrong side of the chokes to be most effective. The bypass caps should be on the "inside" of the choke so that any RF picked up by the connecting wires must flow through the high impedance of the choke before encountering the low impedance of the bypass capacitors.

In the case of the power source, the bypass capacitor should be on the drain side of the isolation resistor for the best filtering.
 
Transistor Radios and D-104 Microphones  
by K1TWH on March 12, 2011 Mail this to a friend!
The output coupling capacitor, at 1000uF, is sized for a 4 ohm load (speaker). For an input impedance of 200 ohms (lower than 99% of all amateur rigs) a 22uF at 16VDC would pass down to 100Hz with less than 6dB roll off, and fit more easily, commercial units would typically use 1 to 4.7 uF for a 600 ohm input.
Also beware of self resonant frequencies of the 1mH RF chokes. It can result in some band(s) causing RF feedback interference in the transmitted audio on that band(s). More than one radio manufacturer has found this out the hard way (same thing happens on occasion when choosing Linear Amp's plate choke, with much more destructive results).
73 & thanks for documenting the D104's response.
Tom Howey WB1FPA
 
RE: Transistor Radios and D-104 Microphones  
by N8NSN on March 12, 2011 Mail this to a friend!
"QUOTE"

by KC2KCF on March 12, 2011
The same schematic with an identical description can be found here:
http://members.cox.net/n4jk/d104.htm

Can't help but wonder who is plagiarising from who?

"END QUOTE"

You know Wulf,

I think you may want to try a little introspection. You want to accuse someone of plagiarism, then back pedal and say you're not accusing anyone of plagiarism, then yet again claim that "someone stole the idea".

Just for the record, Since this was put together only to help other hams make use of an old D-104 on a newer rig; I never claimed that this was my idea ! For Pete's sake I even stated; where the information came from, that I reworked the schematic to make it clear and legible (This is because what I received was hand drawn), and that the specs were even provided to me.

Clearly, I stated that this was provided to me from a friend. As a matter of fact, I have followed through a step further and asked Joe (K2PSI) to provide me with the person whom sent him the info... This turns out to be Rich (W2DAP). How many people would you like to continue to accuse of plagiarism?

E-Ham posts in the articles section are to help other hams. Few eham articles I have ever read claimed to be an originator of any idea. Should we go through the archive and pull any articles that are just a rehashed old school idea and claim that the article is plagiarized? A one tube regenerative receiver comes to mind... How long have those been around, and how many articles have been written on them? How many people would you like to continue to accuse of plagiarism?

As a final point, Wulf. Perhaps you need to read things more clearly before you pop off at the finger tips.

Amateur radio is ALL about people helping others in the hobby/service. Had I claimed that "I came up with this idea and here's how to do it"... Then a plagiarism accusation would be acceptable.
 
RE: Transistor Radios and D-104 Microphones  
by KC2KCF on March 12, 2011 Mail this to a friend!
Dear James,

I really have no intention whatsoever to engage in a p****ng contest, but your misleading claims leave me no choice to clarify.

1. Fact: I did never want to accuse anyone of plagiarism. I wrote that I was wondering who plagiarised from who, which given the evidence, is a pretty obvious question that comes to mind.

2. Fact: I did not back-pedal on this. I stated I didn't accuse the author (you) of plagiarism, since it could be that the other party copied the details from you, or they originate from yet another source - which is exactly the same as point 1.

3. Fact: I never claimed that an idea was stolen. I frankly find it quite infamous to put this in quotes, suggesting this was a quotation when I fact I never wrote this or anything like this! The concept of stolen ideas was brought up solely by (an)other contributor(s) to this thread.

Now, there is little question that someone deliberately copied. And by this I do not mean a basic concept (a voltage follower is indeed pretty elementary), but a specific circuit, with the exact same component values (which, as pointed out by others, are somewhat peculiar) and the schematic drawn/laid out EXACTLY the same as another source. This is clearly not a coincidence.

(I also note that the supply voltage range is given as 4 to 14 V in both sources, nevermind that e.g. according to the Fairchild data sheet, the gate-source threshold voltage of an MPF102 may be as negative as -7.5 V, which would likely pose a problem for the self-biasing scheme when using only a 4V supply. But I welcome if someone can correct me on this.)

I won't argue whether amateur radio is about helping each other (though I have a hard time imagining why amateurs, who in the US are at minimum deemed qualified to safely beam 1.5 kW of UHF or microwave radiation into the neighborhood, should need help designing a 1-transistor audio frequency voltage follower).

The point is, you are not operating an amateur radio here. You're publishing an article online, which these days is not much different than publishing on paper. The relevant standards are not those of amateur radio, but of publishing, and plagiarism is a deadly sin in this field.

If the originator of the schematic complained about a copyright violation, I believe s/he might even have (under US anti-piracy laws) the legal power to have this web site shut down! Just because you tidied up a hand-drawn schematic doesn't entitle you to publish it - e.g., do you think people would get away with distributing a pirated copy of a J.K. Rowling bestseller because they typed it in from a poor quality photocopy of the original, even if they acknowledged "I got the manuscript from someone else"? As an author, it is your responsibility to make sure the material is original or properly attributed and referenced.

(The following is not solely targeted at your article, but a more general rant.)

This is not my web site, so I don't have a say in how it is run. But I believe it would reflect VERY poorly on the amateur radio community if it were deemed acceptable to have "elastic" standards when it comes to technical quality, intellectual property, and moral rights to an article. In such a situation, association with "amateur radio" could be seen as a liability for qualified experts/professionals - and if we lose them, the amateur community would get LESS help from people who they could learn the most from.

Want quality articles on eham? One possible way is to make sure that professionals don't feel embarrassed to publish here!
 
Sure Wulf, what-ever...  
by N8NSN on March 12, 2011 Mail this to a friend!
OK Wulf, I suppose you think I need to slit my wrist here?

I appreciate you bringing the originator of the schematic to everyones attention. I only wish someone else in the line of where this all came to me from, would have. The information simply was not available.

Do you spend your days searching every article you read for the possibility that someone else already patented it?

Yes, the circuit is simple.

Last time... I will state again, Just trying to help others.

Last time... I NEVER claimed the circuit was MY IDEA...

The jewelers lamp/boom... MY IDEA.

Pi__ing contest? Nope... not for me, but your whole response to this leads me to believe that that is essentially what you do best in life.

By the way... What a way to make friends and build camaraderie through your statement that essentially says USA hams are incompetent. You sir are not worthy of my further attention.
 
RE: Transistor Radios and D-104 Microphones  
by KG4TKC on March 12, 2011 Mail this to a friend!
The eham Philosophy:

NO GOOD DEED GOES UNPUNISHED!
 
RE: Transistor Radios and D-104 Microphones  
by W8JII on March 12, 2011 Mail this to a friend!
Much Ado About Nothing!!!!!!!!!!!!!!!!!

So sue me Shakespeare!
 
Transistor Radios and D-104 Microphones  
by N4UE on March 12, 2011 Mail this to a friend!
N8NSN, THANK YOU for the great article. Some people are NOT happy unless they try to make themselves appear superior, just by "stiring the pot".
Just like the 'Reviews" section, where a particular piece of gear will have 100 'reviews' of 5/5 and someone has to write in with a 0/5 and not even own the equipment!
Like the one complainer, these are easy to 'filter out'......

Thanks again OM!!!

ron
N4UE
 
Transistor Radios and D-104 Microphones  
by N8TNJ on March 12, 2011 Mail this to a friend!
Great article, I have 2 of these mics to try it on. I wish the people who BITCH so much over these things, would take the time to write an article themselves.
 
RE: Transistor Radios and D-104 Microphones  
by W4KLP on March 12, 2011 Mail this to a friend!
Nice article. Thanks for "passing it along".
Too bad there are always those out there that always enjoy stirring up the pot.
 
RE: Transistor Radios and D-104 Microphones  
by KB1GMX on March 12, 2011 Mail this to a friend!
RE: AA4PB:

Actually the 220 ohm on the drain not bypassed serves a function. It keeps the FET from taking off at VHF or higher due to leads and strays. Keep in mind at VHF
and up that gate lead is effectively at ground with long leads on the device. Also the 100pf at the output may or may not be on the wrong side of the choke depending of if you are viewing it as a source of RF or a destination. In varying cases it's right, wrong or not any effect.

This is a very old circuit [read classic], I remember building it back in the early 70s to use a ceramic (high impedance) mic for a solid state PA system that only had low impedance dynamic inputs. I thing the original was published by one of the device vendors of the 2n3819.

There is one caveat. more voltage is better than less
with a minimum of 6V and 9 or higher (as much as 20!)
suggested. Reason for this is Ceramic/crystal mics put out fairly high voltages and too low a voltage can cause limiting/clipping when close talking the mic.
You do want the amp to resist overload.

Allison

 
RE: Transistor Radios and D-104 Microphones  
by W5TTW on March 12, 2011 Mail this to a friend!
Wulf, I hope you forgive me for plagiarizing others in this thread, but "Nice Article!"
 
RE: Transistor Radios and D-104 Microphones  
by PHANTOMFIXER on March 12, 2011 Mail this to a friend!
Thank you for the article.To the other "gentleman" get a life.
 
Transistor Radios and D-104 Microphones  
by KE7FD on March 12, 2011 Mail this to a friend!
Thanks for the excellent information. There have been many write-ups over the years on the D104 which is probably my favorite mic, and I have one with the Heil element and one with the original element. Thanks to your inspiring article I am going to renovate the unused "head" and get it on the air. I guess I was just waiting for the right inspiration to come along. Yours was just the trick.

Thanks for sharing in the true ham spirit.
Glen - KE7FD
 
RE: Transistor Radios and D-104 Microphones  
by W4KVW on March 12, 2011 Mail this to a friend!
I use an ASTATIC "SILVER EAGLE" D-104 on my ICOM 746 PRO & after testing with the D-104,ICOM SM-20,& HEIL HM-10(Dual Element)the D-104 WON out over the other two microphones with my "ON THE AIR" testing so I am now running the SILVER EAGLE with the 746 PRO & I SOLD the HEIL HM-10 & the ICOM SM-20.NO MODS on the radio or the D-104 & it sounds GREAT!

GOD BLESS,
CLAYTON
W4KVW
 
Transistor Radios and D-104 Microphones  
by K1DA on March 12, 2011 Mail this to a friend!
Bands must be dead. Too many beauties here with nothing better to do than sharpshoot someone. On the other hand, who would want to talk to these Mensa types anyway.
 
RE: Transistor Radios and D-104 Microphones  
by K0BG on March 12, 2011 Mail this to a friend!
I'm not taking sides here with whomever designed, copied, plagiarized, or anything else to do with the basic article. Fact is, I could't care less.

What really bothers me are the statements herein where folks claim the microphone in question (it really doesn't have to be a D104, Shure 444, or any other), sounds better. The question is, how do they know it does? Mostly, it is because someone told them so. But this fact brings up yet another issue.

Very few, even precious few, amateurs own the necessary equipment to measure spectral purity. Rather, they assume that a good audio report is adequate proof that their microphone selection, gain, compression level, you name it, is right on! The truth lies elsewhere.

IMD is very difficult to physically hear within the bandpass of most transceivers, unless it is really, REALLY bad. You can't see it on a station monitor, cheap oscilloscope, or by ear! However, a kHz or so either side of the transmit frequency, IMD can be clearly heard in most cases.

The truth is, it is very difficult to achieve a better transmit quality, than that garnered by a stock, closed-talked, hand held microphone, with the gain set just high enough for full modulation.

Any amateur, who thinks their audio is top gun, should read this article: http://www.eham.net/articles/8069

Alan, KBG
www.k0bg.com
 
RE: Transistor Radios and D-104 Microphones  
by KD8DEY on March 13, 2011 Mail this to a friend!
I believe the point of the article was to show how to modify the original NON amplified D104 to a modern rig.

The silver eagle already has an amplifier board which serves the purpose of helping match the high impedance of the element to the lower impedance of a more modern rig....

BTW anybody ever notice that a lot of people like to mount the DAL heads on a amplified TUG/TUP stand BUT never modify the amplifiers output filtering to match the increased frequency response of the DAL?......

if you look at the first stage of a D-104 it is a buffer stage (emitter follower). All the amplification is done by the 2nd stage which has the gain fixed and the output set by adjusting the tap point of the 5k pot feeding the collector......

 
RE: Sure Wulf, what-ever...  
by VA7CPC on March 13, 2011 Mail this to a friend!
FWIW --

It's a nice, worthwhile article.

Having a reference to an earlier source is useful as well.

"No good deed goes unpunished" ? That statement is supported by the evidence.

charles
 
D-104 SOUNDS GREAT!!!! }:>)  
by W4KVW on March 13, 2011 Mail this to a friend!
ALAN,NO MATTER what the article says,"I'll take the SILVER EAGLE D-104 audio OVER the TWO OTHER microphones I listed"! I have heard it as well as MANY others & it SOUNDS "MUCH BETTER"(GREAT)on the air & for ME that's what's IMPORTANT" or what matters anyway! Some thing work when REASON says they will not in MANY cases.Just look at a BUMBLE BEE & tell me how does that BIG BOY "FLY" with those TINY wings?

Clayton
W4KVW
 
RE: D-104 SOUNDS GREAT!!!! }:>)  
by K7PEH on March 13, 2011 Mail this to a friend!
Thanks for the article. I have a D-104 sitting in the garage and this looks like a good incentive to play around with it.

But, my motivation is not to obtain great audio. I mean, aren't most of us operating SSB. Sure, I have heard some good audio and some bad audio. But, if I am working a station for the first time (which is most of my contacts) why do I care about his audio if I have good copy.

Actually, most of the time I operate CW but I really do not understand this audio thing of ham radio.

I will do this D-104 project for two reasons. One, I think I might learn more about my mic and how it can be used. Two, it looks easiest enough to do. Who knows, maybe I will turn the D-104 into something useful for the shack rather then something that sits in the garage.
 
RE: Transistor Radios and D-104 Microphones  
by WA7NCL on March 13, 2011 Mail this to a friend!
Its laughable, the argument of copying of the circuit. The use of a cathode, source, emitter follower to convert a high impedance source to a low impedance load is well known and very old. As an electronics designer, given this sort of design task, I would have come up with a very similar circuit without ever seeing the "original".

You might just as well accuse someone of copying the wheel without giving credit to the originator.
 
RE: D-104 SOUNDS GREAT!!!! }:>)  
by AA4PB on March 13, 2011 Mail this to a friend!
Also the 100pf at the output may or may not be on the wrong side of the choke depending of if you are viewing it as a source of RF or a destination. In varying cases it's right, wrong or not any effect.
------------------------------------------------------
Most of the time, RF is picked up by the connecting wires and fed back into the FET circuit thus the cables are the source. That's why L-C filters are most effective with the capacitor on the "inside". Of course, if you don't have any RF in the shack then it won't even matter if you use an RFI filter.


 
RE: D-104 SOUNDS GREAT!!!! }:>)  
by K9MHZ on March 13, 2011 Mail this to a friend!
Good grief....a long winter up there, Wulf?

And while you're on this purity kick, try looking up the word "whom" in the dictionary. Looks like you could have used it a few times in your posts.


Nice original article, and thanks for posting.

Best,
Brad, K9MHZ

 
RE: D-104 SOUNDS GREAT!!!! }:>)  
by W9AC on March 14, 2011 Mail this to a friend!
From the article text:

"The 1 k source resistor provides the proper load impedance to the rig with transistor audio input parameters."

The 1K resistor actually provides a reasonable source impedance, not load impedance to the transceiver's input. The source resistor value is calculated, for simple optimization, as the reciprocal of the FET transconductance (gm) value. For the MPF-102, a range of gm values is shown on a manufacturer's datasheet. The geometric range of gm values on the Motorola MPF-102 datasheet results in a source resistor value of under 600 ohms. 1K is probably on the edge of acceptability.

A couple months ago, W8JI and I discussed the circuit shown in this article as it appeared elsewhere on the web. It contains several opportunities for improvement. You can see better versions on the W8JI website or on my QRZ.com page:

1) Unlike a common-source FET amplifier, an FET as a source-follower is completely self-biased and requires no gate "leak" resistor. The only reason to use a gate resistor is to assist in protecting the gate from static damage in low humidity environments. The crystal cartridge requires no "impedance matching." It's only a voltage source being operated into a bridging high-Z circuit. Being in FL, a gate resistor to ground is not a concern for me. For those of you in low humidity areas, I would consider a gate resistor but no lower than 10 meg between the gate and circuit ground. The mic element sees the gate resistor in parallel with the 10-meg input resistance of the FET. For some D104 elements on the lower end of effective series capacitance values, this can make a difference in low-end response - for those wanting a response to extend below ~ 150 Hz (e.g., AM or ESSB).

2) The 0.01 uF coupling cap at the gate is not required. Since the FET source-follower circuit can be made so small, it can actually be mounted inside the D104 mic head (rather than the base of the lamp stand as shown), eliminating the need for the RFI components between the crystal element and FET.

3) The 1000 uF output coupling cap is way too large and does nothing more than to allow "thumps" and other low-frequency artifacts to pass. A more reasonable value into a moderately low-Z mic input circuit is 10 uF.

4) The 1 mH choke on the PTT switch line is ill-placed. If required at all, it should be located at the transceiver end.

The FET source-follower circuit is forgiving of its designers. That's one reason why we see so many variants of the circuit on the web and in print.
 
Transistor Radios and D-104 Microphones  
by KC6KIM on March 14, 2011 Mail this to a friend!
D-104 Jack!
He-He-He
 
RE: Transistor Radios and D-104 Microphones  
by KE7FD on March 14, 2011 Mail this to a friend!
To whom it may concern;

This is AMATEUR radio, not Commercial, nor is it entirely made up of professional engineers. Most amateurs don't have access to a rack full of calibrated test equipment and therefore need to rely on the good old fashioned method of the opinion of the guy at the other end. After a few dozen good/mediocre/bad reports we can get a pretty good sense if the mic is good/mediocre/bad. What is the fixation on a few select hams on waving their attention-grabbing flags for all to see? This article was intended from what I can tell as a way to utilize a vacuum tube era mic with modern radios. Will the same or similar method work with other mics other than the D104? Maybe, but we're AMATEURS, go experiment and try it out. We're not all purists and do not need to be one to enjoy the hobby. To suggest that we need to scope everything we do is elitist snobbery. We do have a legal obligation to make sure our gear complies with FCC regulations but come on. Why is it that the same few gasbags feel it is their duty to criticize every eHam article not authored by them? 'NSN did those with the true spirit of ham radio a favor by writing this article.

Glen - KE7FD
 
Transistor Radios and D-104 Microphones  
by KD8MJR on March 14, 2011 Mail this to a friend!
The kind of comment from KC2KCF is exactly what will keep more people from writing articles like this.
What Wulf should have done was contact the Author in private and ask his question, if he could not get a satifying Answer then make a statement on the forum.
I guess that's why in the old days before Telephone and Internet people where very Cautious in what they said, because the guy in front of you would punch your lights out.
 
RE: Transistor Radios and D-104 Microphones  
by AF6CO on March 14, 2011 Mail this to a friend!
It seems no matter where you go there are people who have to make themselves feel better by tearing other people down. There seems to be more of these people here on this site than the other sites I frequent. This is the main reason I don't come here often. Too bad, it's a nice site otherwise.


Thanks for the article. I'm sure there are people out there that will appreciate it and convert their old d-104's with this circuit.

73
 
RE: Transistor Radios and D-104 Microphones  
by G3LBS on March 14, 2011 Mail this to a friend!
Excellent article. Ignore the nanny state contributors - all knowledge, education and health should be free.
 
RE: Transistor Radios and D-104 Microphones  
by W8AAZ on March 14, 2011 Mail this to a friend!
Jeez, what if someone printed an article about a crystal radio on here with the schematic? Would someone claim it was taken from some obscure manual from 1915 or something? Stole the design from the Boy Scout manual? This is a fet simple preamp. Most of them look about the same. How many configurations are there to a single stage FET amplifier that it is an issue, unless the article writer claims he invented it or copyrighted it? I suppose he forgot to do a patent search, too.
 
RE: Transistor Radios and D-104 Microphones  
by W3LK on March 14, 2011 Mail this to a friend!
"all knowledge, education and health should be free."

Nothing is free, my friend; someone, somewhere has to pay the bills for it.
 
Transistor Radios and D-104 Microphones  
by CBISBACK on March 14, 2011 Mail this to a friend!
You morons would bitch if they hung you with a new rope.

The OP wrote a nice, informative, article.

Quit worrying about where it originated from and learn from the article.

Joe Biden did the same thing and look at Joe today.

What a bunch of morons.

 
RE: Transistor Radios and D-104 Microphones  
by W9OY on March 15, 2011 Mail this to a friend!
Thanks to James for writing about his experience. His experience is not plagiarism, it is his experience. I think it's a good thing for a ham to experiment a little and for his success to be shared.

Thanks to W9AC for a more refined circuit design based around the data sheet of the device used and the object of more precisely matching a very high impedance source, to properly matched low impedance source while simplifying the parts count to only what is relevant. If you look at both articles in a both/and kind of way there is a lot to be learned, as the thought process of this article feeds into the more refined thought process of Paul's article. I enjoyed the whole deal.

73 W9OY
 
Transistor Radios and D-104 Microphones  
by K1CJS on March 15, 2011 Mail this to a friend!
Thank you, James, for the ideas and the outlining of how to adapt those older mikes to newer equipment. Ideas and examples like this are what this site should see more of.

To those detractors who have nothing better to do but complain and accuse, why don't you close your mouth--or better, smash your keyboard--before you prove yourself to be the hind end of a horse!
 
RE: Transistor Radios and D-104 Microphones  
by K1CJS on March 15, 2011 Mail this to a friend!
>>"all knowledge, education and health should be free."

Nothing is free, my friend; someone, somewhere has to pay the bills for it.<<

Most of the time ideas like this one or others on this site are given freely. The price? The unsolicited and unwelcome complaining and the slamming of the donator by others who also use this site--morons who should know better.
 
Life is good  
by N8NSN on March 15, 2011 Mail this to a friend!
Well, just to satisfy any curiosity anyone may be sitting upon:

I contacted Art. I would post his reply, but I didn't ask him permission to do so. In condensed form, Art stated that he was thrilled the article was placed SO OTHER OPERATORS COULD MAKE USE OF THE CIRCUIT. That kind of says it ALL. Also, He really liked the way it was laid out, provided an "atta-boy", and stated this IS INDEED in the true spirit of amateur radio. Wow, big surprise, eh?

I figure the best reply was the one asking Wulf, "What do you have to offer?" Interesting that after Wulf's possible hang over induced dribble was met with honesty and dignity, he sort of went back under the rock from whence he came with his nasty (though claimed not to be nasty) commentary.

Something that just about anyone can learn from, a simple quote, which No, I am not the originator of...

" When you lose it, you lose. "

Just thought that may be a pleasant way to sum up the observations made in 'replies' to this posting.
 
RE: Transistor Radios and D-104 Microphones  
by KE7FD on March 15, 2011 Mail this to a friend!
One last thought James: Keep 'em coming. I'd like to read more articles like this.

Glen - KE7FD
 
RE: Transistor Radios and D-104 Microphones  
by W0FM on March 15, 2011 Mail this to a friend!
Nice offering once again, Jimmie. For whatever reason, Art (or the "original" originator) apparently didn't post the information here on eHam. But YOU DID! As a result, many of us saw it for the first time.

And most of us thank you for that.

73 my friend.

Terry, WFM
 
RE: Transistor Radios and D-104 Microphones  
by WB6DGN on March 15, 2011 Mail this to a friend!
"Nice job with the schematic and photos. Thanks for sharing your project!"

Yes! Although I enjoyed the article in its entirety, what caught my attention most was the quality of the schematic. Clean, uncluttered and very easy to read. This is something that is very rare these days, even in some of the technical journals that I subscribe to. Good job!
Tom DGN
 
RE: Transistor Radios and D-104 Microphones  
by WB6DGN on March 15, 2011 Mail this to a friend!
"
"This is AMATEUR radio, not Commercial, nor is it entirely made up of professional engineers."

TRUE enough and I will be one of the first to insist that there is room for everybody, AND THEIR OPINIONS, to be represented in the hobby AND THAT INCLUDES THE TECHNICAL TYPES.

"Most amateurs don't have access to a rack full of calibrated test equipment and therefore need to rely on the good old fashioned method of the opinion of the guy at the other end."

To some extent that may be true, but there are situations where "flying by the seat of your pants" is just not good enough. For example, when operating near the band edges, an AMATEUR, needs to be able to measure his frequency and understand the concept of "sidebands" sufficiently to assure his compliance with the law. The AMATEUR must insure the spectral purity of his emissions to very liberal standards but, none the less, to insure that he will not cause interference to others. The "...good old fashioned method of the opinion of the guy at the other end..." won't cut it here should one receive an FCC "pink slip".

"What is the fixation on a few select hams on waving their attention-grabbing flags for all to see?"

I don't think that was the intent of those who, like the author of the article, tried to provide useful information to supplement that given by the author. In the case of several of those who added contributions to this article, I am CERTAIN that that was not their intent.

This article was intended from what I can tell as a way to utilize a vacuum tube era mic with modern radios. Will the same or similar method work with other mics other than the D104? Maybe, but we're AMATEURS, go experiment and try it out. We're not all purists and do not need to be one to enjoy the hobby.

Absolutely true, I couldn't agree more. However, there are those among us who ARE PROFESSIONALS, and who have a great deal to offer the rest of us. If, in the course of offering their advice and expertise, they demonstrate their experience and ability, is it right that they should be ridiculed and condemned for it? Is that not the VERY SAME bias and prejudice that you are decrying?

"To suggest that we need to scope everything we do is elitist snobbery."

Would you consider it "elitist snobbery" for a carpenter friend to suggest that you use a table saw or radial saw when building your speaker cabinets rather than your hand saw? Would you consider it "elitist snobbery" for your mechanic to suggest that you use a torque wrench when replacing the cylinder head on your automobile rather than the Crescent wrench that you happen to have in your tool box? Every field of endeavor has certain "tools of the trade" which are required to do the job right. The equipment doesn't know whether its an "Amateur" working on it or a Professional! The results you get are directly related to the tools you use; AND, to large extent, the choice of tools separates the proficient (NOTICE, I DIDN'T say "professional"), from the tinkerer (NOTICE, I DIDN'T say "amateur).
"We do have a legal obligation to make sure our gear complies with FCC regulations but come on. Why is it that the same few gasbags feel it is their duty to criticize every eHam article not authored by them?"

A pity; I had a few constructive comments to add here, too but I REFUSE to respond to NAME CALLING.

Finally, I have noticed the trend, since I returned to ham radio about 11 years ago, of large numbers of hams to criticize and even insult, fellow hams having a technically oriented discussion and, now, I read of hams doing the same thing here on the internet. What is happening to ham radio? What happened to the "room for everybody" concept that is so often preached when the shoe is on the other foot? Technically oriented people are NOT second class citizens. They are NOT "nerds" or "hackers" or "geeks" or any other very thinly disguised, insulting, demeaning term (in fact, I believe that this may be the source of a lot of the problem). They are merely people, just like any other group of people, but who happen to have developed an interest in a technically oriented field. Most have very ordinary social and personal lives and occupations as widely varied as those with interests in any other hobby.
LIGHTEN UP PEOPLE! There truly is "ROOM FOR EVERYBODY"
Tom DGN
 
RE: Transistor Radios and D-104 Microphones  
by K4GW on March 16, 2011 Mail this to a friend!
I Agree with Tom - the capacitor should be around 4.7uf and the 1 mh choke is too large. Also a .001 uf across the output to ground will take any RF out of the circuit as well.

Jerry M K4GW
 
RE: Transistor Radios and D-104 Microphones  
by K1CJS on March 17, 2011 Mail this to a friend!
By WB6DGN:

>>"....but we're AMATEURS, go experiment and try it out. We're not all purists and do not need to be one to enjoy the hobby."

Absolutely true, I couldn't agree more. However, there are those among us who ARE PROFESSIONALS, and who have a great deal to offer the rest of us. If, in the course of offering their advice and expertise, they demonstrate their experience and ability, is it right that they should be ridiculed and condemned for it? Is that not the VERY SAME bias and prejudice that you are decrying?<<

If I may be so bold to offer this, no, it isn't that those among us who are professionals shouldn't demonstrate their experience and ability. BUT.... The method of demonstrating that shouldn't be to talk down to those of us who are NOT professionals, ridiculing US because we DO try things that the professionals will not, simply because we don't have that experience and ability that professionals do have.

In other words, accept what we amateur amateurs do and how we try to get our ideas across without telling us that we were foolish to try what we did.
 
RE: Transistor Radios and D-104 Microphones  
by N0EQ on March 17, 2011 Mail this to a friend!
K0BG wrote:
> " ...Very few, even precious few, amateurs own the necessary equipment to measure spectral purity..."

"Spectral purity" has absolutely zero to do with how good any component of an audio chain "sounds".

"That sounds great!"

""It can't sound great, my waterfall indicates a lack of spectral purity""

"But it SOUNDS great!"

""Sorry, you're wrong. My instruments prove it""

Honestly Alan, you come up with some unbelievably ridiculous views on communications.

SOUND is perceived, interpreted, subjectively judged by human ears. Not spectrum analyzers.


Craig 'Lumpy' Lemke

www.n0eq.com
 
RE: Transistor Radios and D-104 Microphones  
by KE5YTV on March 18, 2011 Mail this to a friend!
Thanks James, Great article. After reading the comments I'm reminded that there's an ass in every crowd.

Mike
 
RE: Transistor Radios and D-104 Microphones  
by WB6DGN on March 18, 2011 Mail this to a friend!
"If I may be so bold to offer this, no, it isn't that those among us who are professionals shouldn't demonstrate their experience and ability. BUT.... The method of demonstrating that shouldn't be to talk down to those of us who are NOT professionals, ridiculing US because we DO try things"

Your point is well taken. It made me recall an exchange that I had on this board with one of the "established gurus" as a newcomer (either my first or second post) and which made me so angry that I didn't return to this board again for two or three years. In response to a question asked on the ELMERS forum, I replied with two generally accepted formulas to assist the OP in solving his problem. While the formulas I gave would result in the correct answer, they did not go into extensive detail nor did I believe it appropriate to burden the OP with a tedious and wordy explanation of the derivation of those formulas. This provided the OP with a working tool on the level of an introductory electronics course while saving the "meat" of the subject for another time. Well, Mr. Guru had other ideas. To this day I have no idea of his motivation, but he repeatedly challenged my answer, not saying so, but insinuating that my reply was incorrect. I think he was trying to prod me to provide a mathematical derivation of the formula I gave and I was equally insistent that I would not do so as it would have only left the OP totally confused and, probably, with more questions than he started with. I have no idea why an experienced contributor would have gotten himself in the middle of a simple attempt to help someone but it took many years, even after I did return, before I would reply on that forum. I guess it all has to do with a person's (in this case, Mr. Guru's) intentions.
Tom DGN
 
RE: Sure Wulf, what-ever...  
by W9NET on March 19, 2011 Mail this to a friend!
Krauts love to criticize anything they can. Its in their DNA.
 
RE: Sure Wulf, what-ever...  
by W6EM on March 19, 2011 Mail this to a friend!
Great article. But, for those of us REALLY old guys with REALLY old D-104s, long ago I resorted to the easy way out. Shoe doesn't fit? Well, get a new pair.....

That is, I removed the crystal cartridge and replaced it with an inexpensive condenser element. Now, my radios have a device with an ouput level and impedance that they're looking for. Flat response from 100Hz to 15kHz or so, and the price was right. Couple of bucks for the element, a resistor and a dc-blocking/coupling capacitor.

The source follower circuit is a good effort, but again, that output coupling cap flew off the paper at me. Yes, something way less than an order of magnitude smaller would do just fine. And, save space to boot. With the stock crystal cartridge, if memory serves me correctly, there wasn't a lot of room in the 'crome dome' behind the element.

Also, the voltage for the source follower can be obtained from most radios that use condenser mikes. It's usually about 8V. If that's too high, use a 78L05 and drop it down. Just be careful not to load down the 8V line too much, especially with Icom radios.

I built a touch PTT device in the base of a custom crafted condenser desk mike using a 2n7000 FET and touching two base-imbedded pennies with one's fingers keys the Icom nicely.

73.

Lee
W6EM
 
Transistor Radios and D-104 Microphones  
by K4IKR on March 21, 2011 Mail this to a friend!
I noticed that almost ALL the negative comments came from calls that indicate they have been hams for a long time.

Are all the "old" hams becoming "grumpy old men"?

PS I'll be 70 in August

Don K4IKR
 
RE: Transistor Radios and D-104 Microphones  
by N4LRA on March 21, 2011 Mail this to a friend!
I think you hit the nail on the head. We are grumpy old men :-)

 
Transistor Radios and D-104 Microphones  
by WB3CFN on March 24, 2011 Mail this to a friend!
PERFECT! I donated my original non-amp'd D-104 to charity several years ago. A co-worker gave me another one that he (a non-Ham) was given.

I was hoping to find/buy a nice mic for my '817ND. Now, I can yank out the amp in the base of this chrome beauty and make it usable again.

I'm Bookmarking this one!

73!/72!! :)
-Joe
 
Transistor Radios and D-104 Microphones  
by KD3JF on March 26, 2011 Mail this to a friend!
I have a TenTec Delta (580) and it was manufactured probably around 1979. I use a D-104 mike not motified and have excellent reports on the audio.

 
Transistor Radios and D-104 Microphones  
by N8CMQ on March 26, 2011 Mail this to a friend!
Impedance matching, important with microphones, headphones and antennas...

Who'd a thunk it...
 
RE: Transistor Radios and D-104 Microphones  
by K3FHP on April 3, 2011 Mail this to a friend!
I am not judging if you are right or wrong, but if you make such a charge it incumbent on you to cite the original source of the article you say was misused. Also, this is such an old and worked over issue it would be impossible to know who originally wrote about such a circuit.
 
Transistor Radios and D-104 Microphones  
by W0FMS on April 6, 2011 Mail this to a friend!
Been there, done that...

http://www.fredspinner.com/W0FMS/micpreamp/

The key to those old mics is the HIGH IMPEDANCE input. They work great with a little preamp literally built out of Radio Shack parts.

Fred
 
RE: Transistor Radios and D-104 Microphones  
by KC9NCS on April 9, 2011 Mail this to a friend!
I've a handful of D-104's in the shack ranging from Golden to Silver Eagles, looks like a nice simple project to put one or two of them back into service in my newer Kenwood.

Thanks for sharing, 73's
Larry
kc9ncs
 
RE: Transistor Radios and D-104 Microphones  
by W9AC on April 11, 2011 Mail this to a friend!
From the W0FMS website:

"The JFET preamplifier provides a slight voltage loss, but a current/power gain for the microphone, resulting in a lower-Z output (selected by the "swamping" resistor marked Zrig above.) This provides a low-Z impedance to the rig..."

The output Z is set by the source resistor, not Z(rig). In fact, Z(rig) is a superfluous component. The W0FMS design is a good start but here are some opportunities for improvement:

1) As noted, remove Z(rig). Maximizing power transfer in audio circuits was abandoned when active circuits displaced tubes and audio transformers. Voltage matching is all that's needed. The FET as a source-follower requires no load matching. The rig's mic input simply "bridges" the source-follower's output;

2) Most users will want to eliminate the 1uF cap in what's shown as the FET's Drain lead. It's presence only serves to limit low-end response in a circuit designed to help maintain low-end response from a crystal cartridge;

3) Drain and Source leads on the schematic are reversed. Switch Drain for Source. In the schematic, it's really shown wired as a "Drain Follower." As stated earlier, the FET is forgiving of its designers and a reversal of Drain and Source in this application is probably not critical. If this were an RF stage, then we would want proper lead orientation. Still, it should be drawn correctly;

4) The 10uF NP cap on the output is fine, but most builders will have an easier time finding polarized electrotytics. Positive side goes toward the FET;

5) Some users will note that the D-104 still provides too much gain to the rig's input -- even when voltage is less than unity through the source-follower. A method I use to bring voltage down to within a working range of the rig calls for a series resitor inside the mic connector. Typically, that resistor will form a voltage diver with the rig's mic input circuit.

Paul, W9AC




 
RE: Transistor Radios and D-104 Microphones  
by W8NSI on April 16, 2011 Mail this to a friend!
Der Wulf sez: "The same schematic with an identical description can be found here: http://members.cox.net/n4jk/d104.htm
Can't help but wonder who is plagiarising from who?"

And Tom N2BEW replied: "It was never claimed by the author that it was his original design. In fact he clearly stated it came from his friend
and we don't know where the friend got it from, perhaps the other website. That is not plagiarism."

Quite correct Tom. But there are always trolls ready to jump in and tear someone down.

It is a very nice article and I plan to give it a try myself. I have a Tentec Jupiter and a D-104.

73 de w8nsi/nnn0uzw jim
 
RE: Transistor Radios and D-104 Microphones  
by KD0NKF on April 17, 2011 Mail this to a friend!
As a newly licensed ham with an old D-104, I think I'll give this a try, and I thank the effort made to post it.
73 Dave
 
Transistor Radios and D-104 Microphones  
by N7CUD on April 21, 2011 Mail this to a friend!
great news,I have an old d-104.been in storage fer @ 20 yrs, not sure if xytal still ok.personally don't care re source of info,besides, if NO $$$ involved, how is it stealing?
 
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