[Milsurplus] The Navy MAK project

[David Stinson]

On 8/11/2019 12:51 AM, Robert Downs via Milsurplus wrote:
>
> Ok, here is a question for the Brain Trust. Been working on the MAK 
> project for a while now and now have a radio that works well on the 
> original channels. The highest current channel is 3.00 MHz
>
> I am including my latest drawing that shows the modified Heathkit 
> HP-13 power supply that provides the B+ and HV for the radio. I am 
> running the radio at reduced voltages of 165 for B+ and 400 for the HV 
> and getting an output of around ten watts into fifty ohms.
>
> The new problem is I can only get HCU-6 rocks and the radio uses 
> something that looks like a DC-34/35, built an adapter and tried to 
> get the transmitters oscillator up and running but no joy,..
>
I haven't seen a manual for the MAK, but several pieces of that era,
like TCS, require the use of fundimental frequency crystals which are
then multiplied up to the operating freq.  The oscillator is design to
use these lower-freq crystals.  If you use a small-blank fundimental crystal
at 7 MC, rather than 3.5 x 2, there can be issues getting it to oscillate.
Large-blank crystals somewhat outside this range- 4 or 5 MC or so-
can be made to oscillate, but large-blank crystals above about 5 MC
are hard to find.  Small-blanks like FT-243 and HC-6 may not oscillate
if outside the designed band of the OSC circuit.

For example, from the TCS manual:

a. OSCILLATOR. (See figures 2-5, 2-6, 2-7.)-The master-oscillator section
employs a type 12A6 tube VIOl in a Hartley circuit and is
continuously tunable from 1.5 MC to 3 MC.
By adjustment of the TUNING capacitor C-lOlA, output may be
obtained on any frequency within this band.

In Band 1 ( 1.5 MC to 3 MC) and Band 2 (3 MC to 6 MC) the plate circuit
of the master oscillator tube is untuned and the output is capacitively
coupled through C106 and Cl08 to the grid circuit of the buffer-doubler
tube V103. In both these bands the output of the oscillator is within the
range of 1. 5 MC to 3 MC. In Band 3 ( 6 MC to 12 MC), however,
a tank circuit (see figure 2·3) consisting of L103, C107, and ClOlB, is 
switched
into the oscillator plate circuit and the oscillator then acts as a 
harmonic
generator. Thus, output from the oscillator may be obtained in the band
  12A6 tube Vl02. When crystal control is selected, the screen voltage is
removed from the master oscillator VIOl and applied io the crystal 
oscillator
V102. As in the case of the master-oscillator circuit, when the BAND SWITCH
SlOl is rotated to Band 3 (6 MC to 12 MC), the crystal oscillator operates
as a harmonic generator, producing an output on
the second harmonic frequency of the crystal in use.

73 Dave AB5S



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