The AM Forum

I was looking back through the pics of the mic I have coming and can see the tag on the base is the T-UG8 which I believe is the amplified version. I see many people prefer the non amped version but I don't see any reason to not use it except I planned on using the tx/rx switch on the radio and bypassing the one on the mic. Seems like this would kill the battery for the amp pretty fast.

I was thinking that it might be nice to have a ptt box next to the mic so my idea is to use a replay in the radio and use the tx/rx wires coming from the mic to switch on the amp and bypass the chicken choker rig. Does this seem logical or is there a better way?

The non-amplified versions were typically the older crystal elements that had an extremely high impedance (~10 Mohm). These are very desirable for use with older tube radios, but when used with newer radios they lack any low freq response. I added a simple FET circuit that provides a good impedance match to my Flex 6500 and that old mid 1950's chrome lollipop sounds great now! It all depends on what radio you want to use it with. I posted the info a few months ago. Search my call and all the info is available - even a perfect match for the gray hammertone paint!

Replace that old mic amplifier with the one from K7dyy  (http://k7dyy.com) and you're good to go. Use any keying method you prefer.
Doug

Doug, I don't know how I didn't find that while searching around. My google foo must be weak this month. Thanks!

Robert, I thought that the amped versions where high impedance too? I want to plug it into my Clegg 99're so I need the high impedance.

Or I should say that I thought that impedance match was between the amp and the element? Can I just bypass the amp then?

The amplified versions appeared with the introduction of the solid state radios. That preamp did perform the impedance matching, though I was told that newer D-104's had a ceramic element. I have 2 D-104's, an old one and an amplified version. While the amplified version worked with my Flex 6500, I had many comments of too much "coloration". I prefer the sound of the original rochelle salt crystal element.

The Clegg 99'er will work with crystal or ceramic elements. If you don't want to use the mic amp, disconnect the leads coming from the mike element and connect them to the microphone leads to the microphone cable going to the 99'er. On 6 meters, Hi-Fi sounding AM is unimportant.

My first microphone for the Clegg 99'er was the Lafayette crystal lapel mike. Still have it and it still works. Have used it on my Flex 5000. Cost a whopping $1.95.
Here's the Midland Version:

(http://thumbs2.ebaystatic.com/d/l225/m/mosPJr5w7HA3CUq7eLfn8cA.jpg)

I then upgraded to the Lafayette PA-42 crystal mike for the Clegg 99'er and other Clegg rigs. Cost $3.95.

(http://www.retromicrophones.com/images/mic/lafayette_crystal_6900.gif)

Get rid of the amplifier in the base. The MPF-102 mod is the best for impedance matching. Its been around for 25 years. Build your own.

http://web.archive.org/web/20060303104026/http://hamelectronics.com/k1deu/pages/ham/audio/mic_preamp.jpg

Al VE3AJM

Yup....the stock D10-4 amp was useless and is not needed for the vintage radios.  Start by bypassing it. Its the yellow and green wires that come from the element IIRC. Most of the vintage radios like Clegg and Gonset were made for a high Z mike.  The MPF 102 amp works well too.  You dont need to go quite as elaborate as the DEU circuit but you do want to protect the fet from transients.

my .02.

~ps

I bypassed the amp but I'm not seeing any modulation on the 99'er s meter when I transmit. I took the head apart and I see someone poked a couple holes in the foil for some reason.

Is there some way to repair elements or are they pretty much a replace it kind of thing?

""    poked a couple holes   ""


 A GudBudy enhancement.

Its probably FuBar. Put a voltmeter on the output and see if you can get some voltage. Ya never know.


klc

check to see if the center post is still bonded to the foil...sometimes the glue drys out....

Not a blip on my analog vom if I shout into the element. 2 holes, one dent and a blob of glue where someone reatched the center post already. It is the mc321 ceramic element and I see no used or new that might fit. I saw a NOS crystal element on ebay for $80!! Probably doesn't even work.  :'(

Anyway, I'm thinking about one of the electret replacement elements on ebay but the ptt is on the radio and I dont think leaving the amp on is going to be good for battery life. I'm going to have to get creative as in maybe wiring the mic amp to the radio ptt. Any ideas?

I see Heil sells a dynamic element they say will works with their XT transformer on high Z inputs. Bit pricy but probably good quallity? Plus it doesn't require any power like the electret element.

Cant find the size specs for the transformer but they say it is "small" anyone know if it will fit in the mic base?

Looks like $100 for the Heil conversion so I'm gonna have to really think it over with the family budget right now.

Just for fun I'm going to try and remove the diaphram tonight and see what it looks like inside.

J,

Maybee you can use one of those electret mics  found stuck in Styrofoam at the ham fests., and late of RatShaft.

http://www.allelectronics.com/make-a-store/item/mike-79/electret-microphone/1.html

klc

At "normal" voice levels, about an inch away from the grill, using an original, unamplified D104, there is approximately 10 to 15mV  of signal, and if you shout as loud as possible right on the grill, you might see 150mV.  

There were at least two Astatic designed amplifiers for the D104, one using bipolars and a second using a JFET, why some say the "original amp" is no good seems an odd statement to make.
(http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/D-104/radioastatic10_zps360eb889.jpg)

(http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/D-104/radioastatic01_zps6fbf0ccb.jpg)

As for the condition of the diaphragm I doubt the two holes will have any effect to the overall operation, since there is already a vent on the back of the case between the two connections, and the dent, depending on how bad it is, may well be pulled out using a straight pin.

Your "glob of glue" is stock Astatic, as you can see in the pic.   That is how the diaphragm was attached to the Rochelle salt crystal.  Quite possibly its actually wax, a quick touch with a hot iron will tell that, while relieving any stress from the diaphragm being dented/repaired.    
(http://i670.photobucket.com/albums/vv62/mikeinkcmo/Radios/D-104/AstaticElement%201_zpsvjm2buft.jpg)

I have installed 2 of the Heil conversion kits with the HC-5 element.
The element is a low impedance unit but the transformer brings the impedance back up to hi-Z.
No amplifiers, batteries or other nonsense.
If the stand has an amplifier installed....remove it and toss.
Then...after wiring it all up I just wrap the transformer in bubble wrap and let it float inside the stand base.
Essentially all you have to do is cut the foam mounting for the element according to the instructions and wire the transformer.
I use them on Collins, Johnson 500 requiring hi-Z and get unsolicited audio reports.
If I need to use the mic for a modern radio with low impedance mic input....the wiring can be changed to straight through from the element in seconds and the transformer left inside the base for later. A switch might be installed in the base to change back and forth...put the switch between the element and transformer....ie the low-Z side of the transformer to hopefully avoid hum.

Highly recommended!

Thanks Mike, I should be able to read down to 75-100mv with my meter but just to be on the safe side I'll borrow one from work this week as that seems to be on the high end of the output and the low end of my meter. One of the two holes apears to be factory and the other is also the cause of the dent. I doubt they affect it too much either. Thanks for the pic of the glue/wax, that is exactly what mine looks like so probably factory.

Dave, thanks for the input and recomendation. I thik this is exactly how I'll go if I can't fix my element.

Put an RB Micro replacement element in and put the fet circuit in the base and you will be good to go.
It will sound better than the original.
Done this to a dozen or so D-104 mics.
No need to over think this.
Don W9BHI

Don, I've been to his website a couple time but when I went to products there is no way to add any products. It may be a problem with my tablet not displaying his page properly because if I google search his website I find links to actual products. Thanks!

Also, do I need the fet circuit if it's being used on a high impedance rig like the clegg?

Depends on whether you don't care about any lows.  Most input circuits on vintage gear is still too low for the D-104.  The FET amp solves that problem

Al

If you are talking about the K7DYY D-104 board, just be aware that the noise gate is a problem with some listeners.  Not sure if there is a way to turn it off.  Most noise gates introduce an unpleasant artifact of its own

Al

It's RB Micro's website I'm having a problem with but I'm also looking at K7DYY's processor. I did notice that the processor says it has an improved noise gate. Not sure about the specifics.

Hi 'DGG,
   After reading thru this thread, I ordered from RBMicro today. If you click the "products" drop down at the top of page and select "mic elements" you should be able to add to cart.

Ed

For some reason I'm not getting the drop down. I'll try another computer tomorow. Must be my browser.

'DGG,
   Are you linking to http://www.rbmicro.com   ?

Or here: http://www.rbmicro.com/mic-elements.html

Thanks guys. Thats where I'm looking but the products drop down doesn't work on my tablet. Pete's link bring me there though. Gonna get that stuff ordered!

Ordered. I see he seems to be the last scource for these and last night he had 208. Now he has 204. Might order a spare with my next paycheck.

Is that mounting kit needed?

RSWL.................

You could make your own. I bought it because it sounds like he put a lot of effort into figuring out what combination of materials gave it the best sound but I'm sure it would work if you cut out some foam to hold it in place.

Thanks!

It's been a few days since i ordered from rb micro. Paypal has charged me and I got a reciept from the rb micro site but no shipping information and no reply to the email i sent either. The website says same day shipping so I'm just a little concened. There is some talk that he may have gone out of business when I google him. I'm hoping it was just the long weekend.

Anyone get any orders lately?

I ordered the element and mount kit yesterday. I got an order confirmation number in my Email. Not worried about same day shipping.

RSWL...........

I also got the confirmation number but that is just an automated email. I don't mind when it ships but the not shipping when he says it will and no response to emails just has me nervous. Monday was a holiday though so I'll give it until Tuesday before I make any decisions.

I just got an email from Bob. He shipped same day but didn't get out the email right away so all is good and happy.  ;D

"John,
 
I haven’t been too good about sending out shipping confirmations.
 
The first order was shipped the 8th and the 2nd was shipped on the 9th.
 
Thanks,
 
Bob - K0FR"

Just got an Email that the order has been shipped with tracking#. Seems OK.

FYI,
I have used a few of the FET boards that W9AC sells.
He sells them on Ebay.
His ebay name is  vibroplexkeys and the ad # is 231594072242.
They are a little bit pricey and you could probably make one from scratch a lot cheaper.
I just wanted to get something that would just go together quickly and work with the RB Micro kit.
It works great.
If you look him up on QRZ you will see some of the interesting projects he has designed.
Don W9BHI

Thanks! That's not a bad price.

Just curious. From the EBAY ad:

Output impedance:  Less than 300 ohms and will drive both Lo-Z and Hi-Z terminations;

Does that 300ohm output work well with Hi Z tube radio microphone inputs?

RSWL.....................