Joe,
I'm not sure why you think the StationPro causes problems in interfacing to
amateur equipment. The problems a few StationPro builders have encountered
with hum in their microphone circuits have all been traced to improperly
configuring their mic connections. The most common problem has been when a
builder hooks up a vintage mic which uses the shield as the audio return
(along with the PTT return). My little writeup on the topic describes a
workaround for this situation. In actuality, the StationPro does not share
any signals or power with any of a transceiver's microphone connections. It
is, in effect, nothing more than an eight-conductor extension cord (one for
each microphone pin), completely isolated from all desired or undesired
power sources.
That said, I believe your comments about problemmatic RF chokes between the
Mic- line and transceiver ground are well taken, when using audio
accessories which allow microphone leads to share other currents. As I
recall, Elecraft eventually solved their "pin 1" problem by jumpering the RF
choke just inside the front panel, as you suggest. (Incidentally, the
StationPro can be configured, if desired, so that the RF choke can be
jumpered at the transceiver end of the interface cable - at most a few
inches from the transceiver chassis. In some cases this has been a suitable
workaround to the RF choke problem.)
All of these problems are properly called "ground loops," in my opinion,
because they are caused by undesired currents resulting from AC voltage
differences between the transceiver chassis and the chasses of peripheral
equipment. Back in my graduate student days, I worked on experiments
involving voltage measurements of picovolts (measured on materials in a
supercooled liquid helium bath). As you can imagine, keeping track of the
various grounds and signal paths was quite a challenge!
73,
Jim W8ZR
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Joe Subich,
W4TV
> Sent: Friday, June 07, 2013 1:16 PM
> To: amps@contesting.com
> Subject: Re: [Amps] The Pin One Problem
>
>
> I am quite familiar with the issue and while Dr. Garland may call
> it a "ground loop", the problem with The W8ZR Station Pro is the
> same old problem in interfacing with improperly designed amateur
> equipment.
>
> If you bother to look at the schematics for nearly every Yaesu, Icom
> or Kenwood transceiver, you will find that the "mic return" connects
> to the emitter (discrete transistor preamp) or non-inverting input
> (op amp amplifier) of the microphone preamp or amplifier and that
> point is connected to the transceiver chassis via an RF choke for
> DC.
>
> When the mic return is not *tightly bonded* to the chassis, it causes
> currents on the return to find their way to the chassis through the RF
> choke and in doing so produces a voltage in series with the mic audio
> (I^2*Z). It is not rocket science and not "new." It is amazingly poor
> design - one "designer" coping from another - nobody knowing what they
> are doing and why. A lot like the blind copying of "floating" grids
> in common grid triode amplifiers.
>
> Quite simply, when a transceiver and an audio processing accessory
> - whether it be W8ZR's Station Pro or a microHAM microKEYER II -
> are connected to a common power supply (at the power supply), some
> fraction of the current drawn by the transceiver will return to the
> power supply via the connections (PTT return, Computer control return,
> mic shield, FSK return, Key return, headphone return, etc.) between
> the transceiver and accessory device. Unless *all* of those returns
> - *including the mic return* - are terminated to the transceiver
> chassis that current will appear across the RF choke (remember the
> current varies at at an RF rate) which will act like an old fashioned
> choke modulator.
>
> It doesn't take much current through that RF choke to generate enough
> modulation to be a problem. Typical audio levels for a microphone
> vary from around 5 mV for a dynamic (Kenwood, Yaesu) mic to around
> 25 mV for an electret (Icom) element.
>
> There are a large number of "band aids" for the design problem in the
> amateur transceiver mic inputs. *ALL* of them work by reducing the
> current in the returns between the transceiver mic amp and the
> accessory. They are as varied as the designer - including reducing
> the resistance in the power supply jack on the rig (multiple pins
> in parallel), increasing the gauge of the power cord, bonding the
> respective chassis together with wide strap, providing power to the
> accessory from an *isolated* power supply or from an aux port on the
> rig, etc. However, none of them really fix the design flaw in the
> transceiver which would generally be as simple as connecting the
> mic return directly to the chassis at the mic jack and connecting
> a jumper across the offending RF choke.
>
> The amateur manufacturers (except Elecraft, in part) have not learned
> what Muncie showed decades ago in professional audio equipment.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 6/7/2013 11:38 AM, Carl wrote:
> > It is obvious that you have drifted off the subject which related to the
> > Station Pro which Jim thouroughly explained the ground loop issue.
> >
> > Carl
> > KM1H
> >
> >
> > ----- Original Message ----- From: "Joe Subich, W4TV" <lists@subich.com>
> > To: <amps@contesting.com>
> > Sent: Friday, June 07, 2013 11:12 AM
> > Subject: Re: [Amps] The Pin One Problem
> >
> >
> >>
> >> The problem is that it is not a "Ground loop" - there is no issue
> >> with multiple grounding if the inputs to the device are designed
> >> properly. It occurs only when the signal return is not correctly
> >> connected to the shielded enclosure or bypassed - that also impacts
> >> things like VHF/UHF stability, etc.
> >>
> >> If you continue to call it a "ground loop" it is obvious that you
> >> do not understand the nature of the problem. "Pin 1" problem is
> >> as good a term as any since the mechanism for this issue in audio
> >> was first identified in professional equipment using XLR connectors
> >> and the understanding extended to audio equipment with other
> >> connectors (including consumer/prosumer equipment with RCA I/O).
> >>
> >> 73,
> >>
> >> ... Joe, W4TV
> >>
> >>
> >> On 6/7/2013 10:58 AM, Carl wrote:
> >>> That would be too easy since ground loops go almost back to prehistory
> >>> when many discovered the same thing independently at almos the same
> >>> time.
> >>>
> >>> OTOH, before the Brown Theorem it was always called ground loops,
> >>> especially in the pro audio industry.
> >>>
> >>> Carl
> >>> KM1H
> >>>
> >>>
> >>> ----- Original Message ----- From: "Alex Eban" <alexeban@gmail.com>
> >>> To: "'Ian White'" <gm3sek@ifwtech.co.uk>; <amps@contesting.com>
> >>> Sent: Friday, June 07, 2013 5:11 AM
> >>> Subject: Re: [Amps] The Pin One Problem
> >>>
> >>>
> >>>> What about plain old ground loops, numerology set aside?
> >>>> Alex 4Z5KS
> >>>>
> >>>> -----Original Message-----
> >>>> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Ian
White
> >>>> Sent: Friday, June 07, 2013 9:52 AM
> >>>> To: amps@contesting.com
> >>>> Subject: Re: [Amps] The Pin One Problem
> >>>>
> >>>> K9YC wrote:
> >>>>
> >>>>> When you invent, create, or discover something, you get to name it.
> >>>>
> >>>> Would that would be "Brown's Law"? I'm sorry, Jim, but it just
> >>>> ain't so.
> >>>>
> >>>> We all understand your personal respect for Neil Muncie, but there
are
> >>>> other
> >>>> overriding priorities such as respect for truth and accuracy.
> >>>>
> >>>> It is only justifiable to call this "the Pin 1 problem" where that
name
> >>>> accurately applies: specifically to Pin 1 of an XLR connector in the
> >>>> pro
> >>>> audio industry. But this problem extends far beyond the area where
> >>>> it was
> >>>> originally identified by Neil Muncie. It is no disrespect to insist
> >>>> that the
> >>>> more generic problem needs a better name.
> >>>>
> >>>> Calling it the "Pin 1" problem in situations where it simply isn't
> >>>> pin 1,
> >>>> and even where there isn't a connector at all, is a deliberate
> >>>> falsehood
> >>>> which misdirects and confuses people. It can only be understood by
> >>>> someone
> >>>> who is already initiated into the secret. At so many different
levels,
> >>>> that
> >>>> is simply A Wrong Thing To Do.
> >>>>
> >>>> We badly need a short GENERIC name that accurately indicates the
> >>>> nature of
> >>>> the problem. That won't be easy to find, but it is something we can
> >>>> work on.
> >>>> Calling it the "Pin 1 problem" simply isn't good enough.
> >>>>
> >>>>
> >>>> 73 from Ian GM3SEK
> >>>>
> >>>>
> >>>> _______________________________________________
> >>>> Amps mailing list
> >>>> Amps@contesting.com
> >>>> http://lists.contesting.com/mailman/listinfo/amps
> >>>>
> >>>> _______________________________________________
> >>>> Amps mailing list
> >>>> Amps@contesting.com
> >>>> http://lists.contesting.com/mailman/listinfo/amps
> >>>>
> >>>>
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06/07/13
> >>>>
> >>>
> >>> _______________________________________________
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> >>>
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> >
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