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

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: Radio Shack 33-128 Microphone  (Read 1690 times)
W9ATB
Member

Posts: 3




Ignore
« on: April 18, 2014, 04:03:46 AM »

I recently purchased a Radio Shack 33-128 mic to use on my Ten-Tec Omni 7.  Can't get the mic to work with the TT mic adapter.  I can get it to key the radio but it's just a carrier and can't get any modulation.  Purchased an after market 3 pin xlr cable with the 8 pin Yaesu mic adapter and same problem.  Any assistance would be appreciated.

73 W9ATB
Logged
K9YLI
Member

Posts: 872




Ignore
« Reply #1 on: April 18, 2014, 07:33:20 AM »

Does the specs on the mic  match the  TT  mic input  impedance.
Did you have to do any wireing to the mic connectors, if so  check your work.
Does the  'adapter'  wireing match the  radio  input. ??
Lots of  unknowns.......
Check the  8 pin yeasu radio  inputs  to  TT inputs.  There is no rule that the wireing is the same from on brand to another.
Logged
KB4QAA
Member

Posts: 2419




Ignore
« Reply #2 on: April 18, 2014, 10:37:44 AM »

Well it's not a surprise that it doesn't work.  The impedances are grossly mismatched.  While it is generally acceptable to go from lower to higher impedance, this situation is extreme and just won't transfer enough audio power to modulate.  Did you obtain and read the spec sheets for mic and radio?

RS Super Cardiod Mic, XLR balanced, 600 Ohms output
http://www.radioshack.com/product/index.jsp?productId=2997390#tabsetBasic

Ten Tec Omni VII, unbalanced, >10,000 Ohms input, Page 38
http://www.w4ish.net/Manuals/pdf/588_manual_release_2.pdf

You need to provide an impedance matching transformer, or an active device.
Heil Sound sells a transformer, XT-1 which you would need to mount in a box.  
http://www.heilsound.com/amateur/products/parts
DX Engineering order:
http://www.dxengineering.com/parts/hls-xt-1?seid=dxese1&gclid=COmhgunG6r0CFUNqOgodCnAALw

Audio Technica makes an inline transformer from 250Ohm - 50,000 Ohm, which may or may not work.
http://www.audio-technica.com/cms/electronics/f4b735b4cabc30ea/index.html

Radio Shack has an XLR to unbalanced adapter/txfmr but no specs.  
Shure makes one 300 - 40k Ohm.
http://www.musiciansfriend.com/accessories/shure-a95uf-impedance-matching-transformer

Heil Info on Balanced to Unbalanced mic connections:
http://www.heilsound.com/amateur/tips/129-balanced-to-unbalanced-wiring
« Last Edit: April 18, 2014, 10:43:08 AM by KB4QAA » Logged
KB4QAA
Member

Posts: 2419




Ignore
« Reply #3 on: April 18, 2014, 10:52:29 AM »

Possible "Quick and Cheap" solutions:

RS has a general purpose 8:1,000 Ohm audio transformer with a million uses for about $3.  The ratio may be close enough for your needs. Alternatively you may be able to scrounge a similar transformer from an old pocket transistor radios, VCR, Stereo, turn table, boom box, etc.  This would be used to drive the speaker, etc.

RS Catalog #: 273-1380
http://www.radioshack.com/product/index.jsp?productId=2103254&filterName=Type&filterValue=Transformers

-Don't give up. Any microphone can be used with any transmitter, audio system, etc. with the proper matching device and wiring configuration!
Don't be afraid to experiment, you can't blow anything up!

bill
« Last Edit: April 18, 2014, 10:57:07 AM by KB4QAA » Logged
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!