Navy MAK and the HY1269

[KK4YY]

I'd always imagined copper and zinc plates hung in a spittoon.

As a matter of factor, I found a brass spittoon probably made in India and gave it to him on one of my visits. I envisioned it to be filled with some ungodly mixture of bacterial goodness but alas, his wife made a planter out of it per Tim

Leaves one to wonder then...

[Opcom]

I wonder how bigga battery needed for a Timtron transmission ?

I recall a hand cranked generator on a little stand with a built in seat that I was introduced to when I joined the Texas State Guard.
Fortunately the introduction was from another soldier's collection and not something for use during what they call "summer camp" which is a week long anual training in August. Haha that was pretty rough on some of us city boys, vs. the outdoorsmen and former military.
There were some big AGM batteries - but we moved them on ATVs or trucks and only carried a short ditance to a desk or ground pad.

So.. field day - ya get more points for battery ops. I bet a couple of 92AH AGMs would last the day especially if you used a static converter instead of a dynamotor.

[KA3EKH]

The project so far. Using a NARCO power supply modulator that provides +190 for the receiver plates and 350 volts with modulation for the PA. Everything runs from 12 volts DC for use in the field. The issue now is that at full power, about ten watts the modulation is distorted and the plate current is very low. If I tune to either side of the plate current dip to around 50 MA plate current modulation is good but power drops down to around four watts. Can’t understand why the plate dips to almost no plate current and although that he highest output it produces the worst modulation.
If I use the internal modulator don’t have this issue but the two additional modulator tubes suck an additional four amps of current and do not appear to get a lot of gain from the internal modulator but it will work. Using the external modulator I pull the two tubes out that were in parallel with the PA tube forming the hessing modulator.

[kg7bz]

If the externally modulated B+ is having to go through the internal modulation choke to reach the PA tube, you have a major impedance in series that's going to choke off the audio modulation. Running higher current probably partially saturates the choke, reducing it's impedance and letting more audio frequencies through.

August KG7BZ

[KA3EKH]

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 can take a crystal that was for the receive channel on 3.0 MHz that’s at 3.455 and that crystal worked in the transmitter and it ran on 3.455 with no issue so the question is what’s the difference between the two crystal types? And what can I do to adapt the 12A6 oscillator to get it to work? Think maybe the old series huge crystals had more capacitance and possibly a padding capacitor may help but have not tried that yet. Spent most of last night building the adapter and when it did not oscillate was too late to mess with it.
The plan would be to build something into the crystal adapter and not modify or change the original design of the radio. Don’t want to result to installing an external chip oscillator and want to try to keep this using a crystal.
Can this be an issue with the 12A6 not having enough gain? Think the 12A6 is just a twelve volt version of the 6V6 and they make great crystal oscillators.
Also it’s not clear from my drawing but the oscillator stage uses tuned slugs to set the oscillator frequency and you peak the tuning coil by reading the grid drive via the ¼ plug on the front of the radio.
Wasted a lot of time using a HV supply that was grounded and a separate Bias supply and having all sort of issues with getting the modulation right and lots of additional stuff to make it work and finally looked at the original design where the dynamotor had the negative side of the HV supply used for providing Bias and microphone voltage and did the same thing with isolating the HV supply and found the radio works a lot better, just goes to show that sometimes the original design is better then what you can hack together and thinking that I can  maybe find an equal solution to this crystal problem but just can’t see finding any of the original DC-34 rocks for 3885.

[KA3EKH]

Spent a little time playing with the MAK last night and developed a new theory. Although the radio has a published specification of being capable of operating from anywhere in the 2 to 4 MHz band the four channels that were in the radio when I got it were all within 2.1 to 3.0 MHz The output tank has six taps that can be selected in advance for each channel depending on the frequency of that channel and that’s how they match the PA for the band that the radio is using but the oscillator only has a signal LC circuit for each of the four channels. Using old school techniques learned from Mr. Smith brought out the AN/PRM-10 grid dip meter and found that I can check the resonance of the four oscillator tank coils and found that with the coil backed out to the end of its range it only peaks at around 3.7 MHz, and that’s with the slug backed all the way out of the coil. There are four capacitors located just under the coils, one for each coil and I am going to now speculate that maybe the reason the capacitors are so easy to get at is because they were intended to be swapped out depending on what section of the band the radio was on? And perhaps by changing out to a lower value I will be able to get the oscillator to osculate. Know for a certainty that until the LC tank for the oscillator tunes to 3.885 the oscillator won’t work, just need to figure out what capacitor I need. If I were smart I would know two things. First, what’s the value of the existing capacitors? Take a look at the picture. And second, what would the value of the new capacitor be? Recall something about determining resonate frequency of a tuned circuit and knowing the value of C can determine the value of L and with that knowledge be able to determine what C would be at 3.9 MHz but just not that smart. If someone can tell me the value of the capacitors, all four are the same then I will know where to start with smaller value capacitors and try to determine where the tuned circuit is at that time.
Think that they are 50 pf being green is 5 and red for a multiplier is two zeros? Or would that be 500 pf?

[KA0HCP]

You are making good progress!

www.RadioDaze has an excellent chart for component codes. I keep a copy on my bench within reach.
http://www.radiodaze.com/vintage-component-color-code/

From the chart, this would be a 250pF, 500V, 20% capacitor.

You could find the coil Inductance via
1. Disconnect one end and measure with LCR Meter
2. Count turns, measure coil inside diameter, measure wire AWG, use an online calculator or chart from old Handbook.

Engineer Method:
Use the parallel and series LC formulas to confirm the installed resonance, then plug in values for the installed coil; Desired Frequency to solve for required capacitor.

Technician Method
Alternatively, hook up a variable capacitor in place of original capacitor. Using dip meter, adjust variable cap until you reach desired frequency resonance.  Use LCR meter to measure value of variable capacitor.  Install new cap of nearest value.  Adjust slug of inductor for peak.

bill

[KA3EKH]

Used my old LCR Bridge and found it was a 250pf capacitor. Replaced it with a 120pf cap and now the LC circuit resonates in the high end of the 80 meter band without issue. Developing around 11 watts at 3.885 with 375 VDC at 0.05 Ma into 50 Ohms.
The output tank was ok being on its forth strap that I think covers 3 to 4 MHz
Next step is the receiver.

[KA3EKH]

Video of the radio in operation on 3885, built up DC power supply so the radio will be run from twelve volt power source like a car battery. The next step is to try to come up with an antenna for use in the field.
See it at:
https://www.youtube.com/watch?v=X7iniVgFOxk