Re: {Collins} Circuit info wanted



Oh, and to modify the input Z of the AF amp, remove the 1 Meg to ground at the grid and install a 4 Meg To Ground. ..


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-------- Original message --------
From: Garey Barrell <k4oah@xxxxxxxxxxxxxx> 
Date:03/11/2014  22:50  (GMT-05:00) 
To: COLLINS <collins@xxxxxxxxxxxxx> 
Subject: Re: {Collins} Circuit info wanted 

The only problem with the amplified version of the D-104 is with people who run the gain too 
high for their radio to take.  The D-104 is a crystal (or ceramic) cartridge which has a volt or 
more of output  _into a very high impedance_  load, like a Megohm or more.  This is fine with 
tube type rigs, but modern radios (mostly solid state) are designed for a low impedance 
microphone with much lower output.

The amplifier was added by Astatic to allow the microphone to work with newer radios, mostly CB 
type.  Therein lies the rub.....  CB types think that the higher the gain, and the louder they 
talk, the louder their signal will be.

The amplifier provides the Hi-Z load that the cartridge wants to see, and has a Lo-Z output to 
drive any radio, Hi -OR- Lo Z.

Most tube type radios will work fine with the 'bare' D-104, although they will sound better with 
another Megohm or so resistor in series with the cartridge.  If your mic has the amplifier, just 
set your transmitter GAIN control to where you set it with other microphones, then start at 
minimum gain in the MIC preamp.  While talking normally into the MIC as you usually do, increase 
the gain on the MIC preamp until you get the desired modulation level.  Works just fine........

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>

Michael victor R wrote:
> John:
> all that I have read says do NOT use an amplified mic on Collins. Although
> I have a bunch of Astatics I do Not have a "K" but I only buy junk that I
> can rebuild to good working microphone and ironically I have not seen that.
> Have fun! good luck
> mike K9LSH.
>
> On Thu, Oct 30, 2014 at 3:25 PM, Garey Barrell <k4oah@xxxxxxxxxxxxxx> wrote:
>
>> John -
>>
>> I don't have a schematic, but the 'function' of the 'K' version is that it
>> sends either a CW letter 'K' or a multi-tone burst at the end of
>> transmission.  "In other words, 'K' ".  Apparently popular amongst the CB
>> crowd.
>>
>> 73, Garey - K4OAH
>> Glen Allen, VA
>>
>> Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
>> and TR-4/C Service Supplement CDs
>> <www.k4oah.com>
>>
>>
>> John Clare wrote:
>>
>>> I have tried unsuccessfully previously to obtain circuit information
>>> regarding "K" versions of Astatic D 104 microphones.
>>> I have details for most other versions of the D 104 Crystal Mics but K
>>> info seems to be shrouded in secrecy. Are there any Collins owners out
>>> there that have repaired or adapted K versions?
>>> I have a lovely Night K Eagle that needs repairing prior to use with my
>>> KWM-2A.
>>> John Clare VK1CJ.
>>>

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