[Hallicrafters] Re: [Hallicrafters]V4#468 - Microphone choices

[Phil Barnes-Roberts AD6PQ]

[Sorry- Wrong return address last time!]
At 04:05 AM 2/22/04 -0500, hallicrafters-request at mailman.qth.net juggled 
the keys to produce...

>Message: 5
>Date: Sat, 21 Feb 2004 12:35:33 -0500
>To: "hallicrafters-mailman.qth.net" <hallicrafters at mailman.qth.net>
>From: George KB2Z <Thermionic_Emission at earthlink.net>
>Subject: Re: [Hallicrafters] HT-37 & PTT???
>
>Hello again all,
>
>Thanks to all for the advise and suggestions with the PTT. I downloaded the
>73 mag mod from Al's site and accepted two other offers for mods. An sase
>for a factory mod from Ken, and a QST mod for PTT and QSK from Larry later
>in the week.
>My question now is probably more of an opinion type, but not knowing which
>mic. might be better with the HT-37 I thought I would ask.
>I have a Knwd. MC-50 (50k ohm) wired for a TS-530, with a spare 4pin
>chassis mount in the junk box.
>The chassis mount looks to be the same diameter as the original mic.
>I also have a Turner 254 wired for a T-4X. I dont have a spare female
>connector and it looks like it might need a washer to fill the gap.
>As long as it works I dont really care about the look.
>Would one of these mics. be preferable to the other from an audio standpoint?
>
>Again thanks, George KB2Z
>
>
>At 07:25 AM 2/18/04 -0500, you wrote:
> >Good morning all,
> >
> >I got to checking out my new HT-37 last night after reading the manual and
> >see no provision for PTT.
> >Do you wire it somehow through the 11 pin jack and use it with MOX? I live
> >in a loud house, 4 harmonics, with music, animals, and friends. VOX is
> >hard to control in the noise.
> >
> >Thanks in advance for any info., or suggestions, George KB2Z

Hi, George et al--

A thought struck me about microphones.  (It didn't leave a bruise.)  Two 
things to consider; one, is the Mic. Z vs. the radio's Z (impedance out 
should be ballpark-matched to impedance in.)  Most modern mic's are dynamic 
or even electret (with a transistor amp on-board), and can be fairly low 
impedance, but that can be corrected with a transformer, either in-line, or 
perhaps hiding in a base.  The electrets also need a source of power, say 
5-8VDC.  If you also move the mic to your modern rig, you might switch it 
from Hi to Lo.  A lot of the mic's originally used with these old beauties 
were high-impedance, on the order of 50K-ohm to a Megohm, to match the 
input-Z of a triode grid in the speech amp.  I'm thinking here of the 
Astatic D-104 "lollypop" crystal, and its cousins.

The other thing has to do more with the setup of your shack, and the 
background noise in which you mention you have to operate.  (A quiet, 
separate, room is sometimes just not in the cards; been there, done 
that!)  That's where the pattern of your mic comes into play.  Some mic's 
are cardioid (sort of a fat-heart-shaped pattern), which picks up sound 
from all around the table, with one steep notch to the back.  Some are 
called omnidirectional, which I assume means they found a way to hide the 
notch.  Some others are unidirectional (fairly much so), and yet another 
kind used in aircraft and military operations are called noise-cancelling, 
having some clever way to accept sound from the direction _away_ from your 
mouth, and _subtract_ it from the signal coming from you.  Modern commuter 
propjets have long used a similar tricky way of suppressing the high cabin 
noise levels, with speakers in the overhead, focused at your average ear 
location, doing the noise-cancelling at every seat.

The unidirectional style is said to be what Gov. Dean used during the 
boisterous rally that produced the infamous "Dean Scream."  Reporters that 
were _there_ agreed that the noise level in the room was high and rising, 
and Dean was just talking over the background, but the mic captured only 
him.  So you have to be careful about not just what and when you say, but 
_how_ you say it these days...

Hope any of this helped!
-
73, Phil Barnes-Roberts AD6PQ  DM04we | Mailto:AD6PQ at arrl dot net
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