Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

donate to eham
   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Astatic D-104 problems.  (Read 1097 times)
IW5CI
Member

Posts: 69




Ignore
« on: November 27, 2018, 01:31:17 PM »

I recently decided to buy a D-104 mic for my johnson Valiant. Until now i Used a home Made high impedence mic with a dynamic capsule bought at an hamfest with very good results.
When i received the D-104 bought on ebay i checked the capsule and it Was original. The base is amplified . Then i cabled the mic for the valiant, ptt cold side and ground together to the Valiant ground, ptt hot side to ptt pin and mic output to mic input of the radio.
All worked at the first try, very strong audio output from the mic (i have to set the volume under the D-104 to 30%) but...... the modulation is not good. It’s really very tinny, no bass at all , poor midrangei tones and a lot of high. I read that D-104 is the best choice for vintage trasmitters, but in my case is definitely better my 5 bucks home Made mic.
How can i solve the problem? It’s a impedence issue or something else?
Logged
WA2CWA
Member

Posts: 548


WWW

Ignore
« Reply #1 on: November 27, 2018, 03:11:46 PM »

The amplified D-104 audio quality is poor and has a restrictive audio response. By-pass the the amplifier section and just connect the mike element directly to the audio input of the Valiant. The Valiant does not want or need an amplified D-104.

Pete, wa2cwa
Logged
WA4JQS
Member

Posts: 275




Ignore
« Reply #2 on: November 27, 2018, 07:38:07 PM »

the Johnson like Drakes need 100 to 150k Impedance you can do one of two things just bypass the amp (remove the audio wire and run directly to the cable. or try putting 150 k ohm resistor in line with the audio. Drake C lines do much better then the B line with the D 104.
 a lot of the guys use Shure 444 . i really do not like the way they are build style wise. On my B lines i just bypassed the amps in my D104's and put a 150k ohm 1/2 watt resistor in the audio line and the bass came up . Hope this was of some help
73 Tony
WA4JQS Since 1962
Logged
IW5CI
Member

Posts: 69




Ignore
« Reply #3 on: November 28, 2018, 10:26:22 PM »

I connected the capsule directly to the radio , bypassing the amplifier and i god , maybe, worse results. Extremely tinny modulation .


this is the recording from my icom 7300 of Valiant with D-104 with original capsule (without amplifier):

https://drive.google.com/file/d/1NSXn54P4nizv7on7jzQOgM62FHL34znx/view?usp=sharing

this is the recording with a Shure dynamic microphone:

https://drive.google.com/file/d/1bgeU23iQN-fPQRHNhNuJ7Mld34-DLQvO/view?usp=sharing

maybe the element is gone?
Logged
ZS5WC
Member

Posts: 699


WWW

Ignore
« Reply #4 on: November 28, 2018, 10:59:55 PM »

I have the Astatic D-104 with TUG-4 amplified base, works with all my rigs, old and new response is more sharp than bass.
If you want good AM mic, get astatic JT-30 , or EV. Smiley

73 de William
ZS4L / ZS5WC
Logged
VK6HP
Member

Posts: 455




Ignore
« Reply #5 on: November 29, 2018, 03:02:03 AM »

The crystal elements do degrade in some cases but, to get a better bass response, the element needs to be pretty lightly loaded at the best of times - several megohms.  With that sort of loading, you have to watch the capacitive burden of typical interconnecting cables. I found that the best result was obtained by tossing out the bipolar amplifier in the base of the unit I acquired, then replacing it with a FET source follower.  This allows a high impedance loading of the crystal element, while giving a low impedance output suitable for driving modern and classic radios.  It's the loading on the crystal element that's important; any amplifier to radio mismatch is much less significant. You also need to watch the input stage and drive levels; I had the feeling that your D-104 test might have been using a bit too much level, causing more distortion than I'd expect.

Even after everything is optimized, the response will be much more peaky than you are accustomed to hearing with modern systems but it's that response that makes the audio intelligible when microphones with a flat response, or systems with sub-optimum equalizers, often fail.

I should add that I don't use the D-104 as my default microphone; for routine use I have a Kenwood MC-90 amplified, switched, isolated and impedance matched between classic and modern radios.  However, the D-104 is fun to use, and reminds me that many marginal SSB QSOs would be improved considerably if people used less woofy audio.  

Good luck, and let us know how you get on.

Peter.
« Last Edit: November 29, 2018, 03:17:54 AM by VK6HP » Logged
WA4JQS
Member

Posts: 275




Ignore
« Reply #6 on: November 29, 2018, 01:20:57 PM »

add a 100k ohm or a 150 k ohm resistor in the audio lead and you will get the lows and get rid of the tinny sound.
73 Tony WA4JQS
Logged
KE0ZU
Member

Posts: 444


WWW

Ignore
« Reply #7 on: November 30, 2018, 06:43:56 AM »

Peter gives good advise regarding the Astatic D-104 crystal mics.   These classic crystal elements like to be terminated into 5 Meg Ohms for optimal response, but as low as 1 Meg Ohm is acceptable with some, but certainly not severe, loss of low frequencies.

Its a simple matter to verify the frequency response of the microphone using an SPL meter.   HERE is how I've done it.




 
« Last Edit: November 30, 2018, 06:59:14 AM by KE0ZU » Logged

Regards, Mike
https://mikeharrison.smugmug.com/
Pics and bold print are usually links.
WA4JQS
Member

Posts: 275




Ignore
« Reply #8 on: November 30, 2018, 05:02:54 PM »

Yes Peter is correct before i file 13 the D 104 i would add resistance in the audio line.. also Heil and a W2 make replacement elements for the D 104's
73 Tony WA4JQS
Logged
KE0ZU
Member

Posts: 444


WWW

Ignore
« Reply #9 on: December 01, 2018, 09:48:13 PM »

I listened to your two recordings and am very surprised at the response/sound of the 104.  

How did you make your home made dynamic mic "High Impedance", and what is it's impedance?

My first thought is that the speech amplifier circuitry of the valiant has been modified in some way.

Have you done anything to the Valiant?   Have you verified the circuit is "original"?  

If the Mic input load resistance of the Valiant is 1 Meg Ohm, as originally designed, adding 100 - 150K in series with the element shouldn't make any significant difference.

 
« Last Edit: December 01, 2018, 09:53:42 PM by KE0ZU » Logged

Regards, Mike
https://mikeharrison.smugmug.com/
Pics and bold print are usually links.
KD6VXI
Member

Posts: 177




Ignore
« Reply #10 on: December 02, 2018, 06:54:57 AM »

Good to see you, Pete.  Haven't seen ya on amfone....  Glad your back on the forums.

I load my d104 mics with 2 megs of resistance twice.  A 2 Meg resistor in series with each lead to the mic element.  I do this in the element housing.

With this method, I can change the tonality of my TX signal by changing heads.

Also, no 2 D104 elements sound the same.

If you do decide to file 13, lemme know.  I may be interested.

--Shane
KD6VXI
Logged
KM1H
Member

Posts: 4722




Ignore
« Reply #11 on: December 02, 2018, 09:54:51 AM »

Quote
Good to see you, Pete.  Haven't seen ya on amfone....  Glad your back on the forums.

Last time I looked Shane there it was pretty much down the tubes with a small clique making believe they knew it all.
I find the AM forum on QRZ much better and thankfully AMForever is long gone.

Carl
Logged
IW5CI
Member

Posts: 69




Ignore
« Reply #12 on: December 02, 2018, 03:01:05 PM »

I Made a mistake in rewiring d-104 without amplifier, now it works with a good voice response.. my Valiant has received a restoration from an american ham, now deceased (i have been told) and a modification of the bf circuit that exclude the clipping circuit. The previous owner told me that it received hifi mods, but i dont’t have the mod schematic.
Logged
KE0ZU
Member

Posts: 444


WWW

Ignore
« Reply #13 on: December 02, 2018, 07:41:39 PM »

Quote
I Made a mistake in rewiring d-104 without amplifier, now it works with a good voice response.
Great, glad to here your problem is solved.   If you could post a recording I would very much like to hear it.
Logged

Regards, Mike
https://mikeharrison.smugmug.com/
Pics and bold print are usually links.
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!