WTD: Electrovoice 638 Microphone

[Dave Edwards]

If you want to be safe, and not add another project to the list...
A kenwood desk mic will be plug 'n play with any (recent) Kenwood rig...Icom for an Icom, Yaesu for a Yaesu.

If you are a serious DX'er...well, then you can play around with something like a shrill. tinny Heil DX element. 
But...if you're a serious DX'er....you already know that!!

If you have an old Heath, Drake, etc tube rig....
Find any 'old' mic....or just beeline to an old D104....and you will be good to go!!





 -------------- Original message ----------------------
From: Paul <k5rt at VERIZON.NET>
> I've edited out the earlier comments from this thread to maintain message
> size compliance (no more than 150 lines)
> 
> You folks have hit on something DXers and Contesters have known for years. 
> 
> At the risk of stating the obvious (but frequently over looked)...
> 
> Radios behave differently with microphones types. Just because the
> manufacturer provides a mic with the radio doesn't mean it's the right mic!
> 
> There are a number of variables in the transmit audio chain. These include
> the impedance of the mic (cartridge itself or any built in amplifier),
> impedance of the mic amp in the radio, gain of the mic amp in the radio,
> output level of the mic itself (when properly terminated. You can actually
> have a microphone who's cartridge has such a high output that it will
> overdrive the mic amp in the radio - this becomes evident when the mic gain
> setting of the radio is very sensitive (usually very low value)
> 
> Typically "hollow state" rigs have a high impedance mic input and solid
> state rigs have a low impedance input. 
> 
> Next is the audio response of the mic (when properly terminated), audio
> response of the mic amp of the radio and (finally) the users voice. This
> topic leads to the "mission" of the radio. Are you a ragchewer who wants
> good, clean audio, are you a DXer or Contester who wants punch and every bit
> of advantage he can get, or are you one of those hi-fi audio types?
> 
> Most SSB radios are designed with transmit audio circuits that have a
> response from 300 Hz to 3500Hz. Keep in mind that radios that can support AM
> or FM (as well as SSB) will have mic audio circuits with frequency responses
> that are wider than this.
> 
> There are two messages to take away from the above statements. 1) If
> impedances don't match, the audio will be impacted. Typically you will get
> reports of low or "muddy/muffled" sounding audio. 2) If the frequency
> responses don't match up, your audio will have excessive high or low
> frequencies or possibly even sound "constricted" (over filtered) and make
> your voice less intelligible.
> 
> Do a little research. Read the manual to determine what the audio input if
> your radio is. Some manuals may even indicate what the typical input level
> needs to be (not many and most don't say anything about frequency response).
> Read about the microphone you want to use to understand its impedance,
> output level and frequency response. Be doing your homework, you can get a
> good idea about what should work and what won't work (without a lot of extra
> effort). Finally, when you hear someone with outstanding audio, ask them
> about their mic/rig/accessories. What you learn may be worth applying to
> your station!
> 
> Possibly this note will inspire someone to do some research into the various
> microphone cartridge types and their characteristics and share that
> information with all on this reflector. This would be good reference
> material to have on hand.
> 
> If you want to experiment to determine what really works best for you, you
> will have to try different mics. Does this mean you have to actually buy all
> sorts of different mics? No it doesn't. You can borrow different mics from
> your buddies! All you need is to invest in a male connector that fits your
> radio and various female connectors (2 pin, 4 pin, 8 pin or what ever).
> Change the adapter as required. The best suggestion is to have a buddy
> listen to your station and make recordings of your audio. If you want to do
> A/B/C type comparisons, you may need to fabricate two or three adapters. No
> big deal, it's still cheaper than buying mics!
> 
> Also, there's one last set of variables that you need to be aware of, how
> your radio behaves with speech processor on/off or any audio mixing devices
> (W2IHY etc) will also be affected when changing microphones.
> 
> If you have access to lab grade equipment and have the time, you can really
> "dial in" your transmit audio, but (IMHO), it's not worth it.
> 
> One last point, external audio devices (W2IYH equalizers or external speech
> processors for example) can be a point for RF to enter the transmit audio
> system. Pay careful attention to reports of screeching noises or VOX
> circuits not releasing.
> 
> The definition of communication is to convey information between two or more
> parties. Needless to say, you can't communicate effectively if your transmit
> audio is poor.
> 
> VY 73
> Paul
> 
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parties involved.  This list and the City of Tempe are not responsible
for losses or misrepresentations of any kind.  Buyer beware!

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