Well this thread has become more interesting than I expected.
I think I need to tell you more about what I want. I like nice audio. I
dislike 75% of the audio I hear on the ham bands and I am actually
impressed by no more than 5% of ham audio. I want to get my Scout's audio
somewhere in the top 25%.
I operate portable, alternate base and parked mobile. Mostly parked mobile.
Every time I operate I take the Scout out of the box, unwrap the bubble
wrap, do the same with the tuner, set up the Scout on the console, set up
the tuner on the floor, take the mag mount and whip out of the car's trunk,
assemble the antenna, connect coax to the tuner,(sometimes I skip the tuner
depending on the band and range of freq.),connect coax to tuner and then
connect the coax from the tuner to the rig ,connect mic and power supply
and then I apply power and find out if all the connections and solder
joints are still tight. If I added an audio box, it would have to be on the
floor with the tuner because there is no room anywhere else. Do you see why
I would prefer either an internal mod to the Scout or one mic with 2 or 3
elements rather than connecting and disconnecting another box everytime I
decide to operate?
But maybe I would not be satisfied with a dual element Heil, perhaps I
would be happier with the flexibility of a box. If so, I'd like a good one.
I would want the "more complex circuits possible using some classic tone
control circuits" with separate treble and bass pots.
I own solder and soldering irons and multi meter but have never done
anything more than make a dipole and resolder loose connections in my HT. I
have never made a real kit. Although there are guys in my club who would
help me, I think an RF tight, tone control circuit with provision for dc to
the ten tec mic or amp for other mics is *probably* beyond my skills. I
don't have a workbench in my small condo, so this project would be built on
the kitchen floor with help from my cat.
The W2IHY 2 band equalizer sells for $99 in kit form. It includes an amp
and noise gate. I think I could build that. Would this be significantly
better than a dual element Heil mic? I am concerned about RF getting into
the audio through the equalizer - my mobile operation is probably not
perfectly RF tight.
So the options are:
a) attempt to build an RF tight tone control circuit with 2 pots as my 1st
project (on kitchen floor) and set it up on the car floor
b) build a 2 band EQ kit for my 1st kit and set that up on the car floor
c) accept the limitations of a Heil 2 or 3 element mic without a separate
box on the floor
I'm eagerly awaiting Jerry's opinions but I also hope to hear from others
on this list as well.
tnx & 73
Bob, KB1CIW
At 10:36 PM 8/18/02 -0500, you wrote:
>The resistances need not be changed, that way the mid range level stays
>constant. Only the series and shunt capacitors need to change to modify
>the low and high roll off frequencies. With the lows and highs reduced,
>then you increase the mid range by increasing the microphone gain.
>
>I can't suggest capacitor sizes because I don't know the impedance of
>the Scout audio input. The capacitors and switches could be located in a
>box external to the scout. I believe the scout supplies DC for the
>microphone element also which may complicate adding series capacitors
>unless its a separate wire. The scout manual specifications or schematic
>should show the audio input impedance. From that you can choose a range
>of capacitors, probably with ratios between them of about the square
>root of 2, for both the series and the shunt capacitors and then can
>experiment ad nauseam with listeners. Remember that many hams have tin
>ears made tinnier by their radios with infinitesimal speakers. Many
>Tentec built in speakers are not out of that range. You will find
>totally opposite opinions from any change you make.
>
>There are more complex circuits possible using some classic tone control
>circuits so that the amount of bass roll off can be adjusted with a pot,
>and the treble with a separate pot.
>
>When working at microphone level you need to be sure to keep the
>circuits shielded or RF will get in and cause feedback and weird radio
>sounds while transmitting.
>
>A couple switches and a gaggle of capacitors is cheaper and more
>versatile than a single Heil microphone.
>
>Using op amps with RC circuits gets more rapid roll off, and sometimes
>much more roll off per RC element at the cost of adding power and noise.
>I don't think you need that much roll off to make the improvements you
>desire. There are makers of microphone equalizers for ham use that will
>be glad to separate you from your pocket change (up to twice the price
>of the Scout) for fancy microphones and adjustable equalizers.
>
>73, Jerry, K0CQ
>
>--
>Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
>Reproduction by permission only.
>
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