[Elecraft] Microphones for K2/3

[John Huggins]

Thank you for the hints.

Thanks to your and other's comments on the Elecraft list I have found 
numerous good examples with some as minimalistic as a FET + passives all 
the way to a good Instrumentation Amp + passives.

This has inspired me to create a circuit based more on the modern In-Amp 
method leaving the only question of what the input impedance and range 
of typical radio mic inputs.  Plus a survey of what voltage and current 
are available on the mic connector helps design for the most radios.

In support of this I am scoring some wins on D104 mics on Ebay which are 
available on the cheap.

Fun stuff... perhaps I will make this available as a "kit" for fellow 
D104 freaks.

John


Greg Derda wrote:

> I am pretty sure that there are a couple of very simple circuits in 
> "W1FB's Design Notebook" that specifically use the "D104 -> 
> modern_radio" as an example.
>
> Greg
> KI4MMM
> K2 #6100
>
> On Sep 6, 2007, at 1:29 PM, Don Wilhelm wrote:
>
>> John,
>>
>> If your D104 is an older one with the high impedance crystal or 
>> ceramic element, yes it will not work so well (if at all).
>>
>> There was an article in QST about a year ago with a circuit design 
>> that had a very high impedance input and the low impedance output 
>> required by modern day radios, although a transformer with the right 
>> ratio should work too.
>>
>> Another alternative is to change the element in the D104.  Heil 
>> offers a kit to do just that - check www.heilsound.com for info.
>>
>> My D104 with an HC5 element draws comments from time to time.
>>
>> 73,
>> Don W3FPR
>>
>> John Huggins wrote:
>>
>>> Thanks for the information all.
>>>
>>> So...
>>>
>>> I guess hooking up a D104 straight to K2 is not going to work out so 
>>> well.  Yes I know this is like putting tail fins on a Ford Taurus, 
>>> but the kids really dig talking into a mic like that during times we 
>>> promote ham radio.
>>>
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