[AMRadio] The Manual Sez

[James M. Walker]

Ahh not for nothing again,

You are taking my statements out of context, then applying an erroneous
assumption to "YOUR" findings.

The resistor in the hv line in the BC-610 is R-19, it is only in the hv
primary in the "E-model" when the transmitter is in tune mode. Which
lowers the HV output by approximately 1/2 so the tune function can be
made. The "E" model transmitter in then placed in normal mode to operate
AM or CW. at which time the hv dc level on "MY" BC-610(E) is measured at
2450 VDC in CW mode, and 2275 VDC in AM mode, the additional loss in the
hv level being brought about by the addition of the 100th pair and the
modulation transformer. now being in the hv path along with the
subsequent
additional current draw thus lowering the HVdc output. there is NO
switching of the ac input to lower the power supply output voltage on
"MY"
BC-610(E). Plain enough, onward.

My statement below was in fact in error, as my description of what
happens
in the (E) and (I) models is intermixed and confused in "MY" Statement.
This comes from trying to think ahead while typing, and is solely my
fault
consider me suitably chastised.

There is in FACT no switching at all of the HV DC output, the ONLY thing
that happens when you switch from fone to CW is the secondary of the MOD
transformer is shorted (CW) or not shorted (FONE) the increased load of
the modulator is the ONLY voltage reducing element in the circuit.

Your comment about series resistors in the primary are indeed valid,
which
is called out in the manual as (A) do not operate the transmitter in
tune
mode for either CW or FONE. The transmitter MUST be in NORMAL mode
otherwise the plate voltage to the modulator tubes is wrong for the
rated
plate load for the tubes to transformer match. In CW mode the additional
draw (on/off) while in "tune" mode causes chirp in the transmitted
signal
(Actual experience observation) and rightly so.

I only say this as The flaming war has started, I think it is time to
move
on to another topic, as this one has become moot.

73
Jim
WB2FCN


Donald Chester wrote:
> 
> >From: "James M. Walker" <chejmw at acsu.buffalo.edu>
> 
> >the is
> >just one pair(ie two leads) that go to the transformer, there is in fact
> >a 600 watt heater coil (cone shaped) with a light bulb base that is
> >switched into the circuit when the transmitter mode is changed from FONE
> >to CW.
> 
> The purpose of that heater cone is to reduce HV plate supply voltage and
> serve as a current limiting resistor to the transformer primary in the
> "tune" mode.  The transmitter runs full plate voltage on CW and reduced
> plate voltage on phone.  The series resistor would be unsatisfactory in
> "phone" because, with the variations in class-B modulator current, a series
> resistor in the transformer primary would result in extremely poor voltage
> regulation.  You would have the same problem in the CW mode, as the voltage
> would soar with the key in the "open" position.
> 
> Don K4KYV
> 
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