Equipment

Last night, during light burn-in tests, the amplifier suddenly dropped gain.
No alarms, no nothing, but one of the MOSFETS was drawing a lot less current compared to the other, it was also operating in class C. It turns out that for some reason the gate2 on the failing MOSFET has broken down. DAMN!!!!!!!!

Digging in to the RF-deck

 

Failed MOSFET

 

Gate2 to source breakdown. 70 ohm  dc-path between source and gate2 do not make any sense.

Have been working on my 144 MHz SSPA project since 04:00z this morning.
Now the time is 22:30z and I am tired. Continue tomorrow morning.
Here are some pictures of project status.

Starting point this moring

 

PT-100 Temperature sensor

 

Left/Front

 

Rear/Left

 

Rear/Left

 

Inside

 

More inside

 

73 All

Temporary Yaesu Elevation Rotor Fix

Earlier I fried my elevation motor, and I was in need of a quick fix.
The plan is to eventually rewind the original 24VAC motor but this will take some time and materials I do not have for the time being.

The quick, non-destructive solution was to get a $7 worth 24VDC motor, and put that in to service.
All I had to do, besides the rectifier system, was to drill two new holes in the motor bracket and move the cogwheel over to the DC motor shaft.

The ZHENGKE ZGA25RP DC 24V 500RPM Micro Gear Box Motor have an unload speed at about 500 rpm, so the elevation is moving at about 1/5 of the original speed. However, this is more than sufficient when tracking the moon. The stall torque is also sufficient due to the low gearing.

I am considering to get a larger, faster and more powerful DC motor, but then I will have to ether do a non-reversal cogwheel modification or get hold of an another cogwheel that will fit.

 

Left: Original 24VAC motor.
Right: very small 24VDC motor fixed to the original bracket .

 

DC motor, rectifiers and relay in place.

 

 

schematics

The elevation on my old Yaesu G5400 failed last night. The load of winter with heavy snow freezing on to the EME antenna made it to heavy for the rotor, it stalled, then the elevation motor fried due to me not detecting what was going on.
The antenna is only a single antenna for 144mhz at 3wl length, a bit heavy balanced at the rear.
I think the G5x00 series I great for small SAT antennas, especially with its 180 degrees elevation movement. However, I think it is not sufficient to operate mid-size and up antennas in cold and snowy conditions. NOW! Tinkering about what to do next……..QRT for now, but will be back.

Probing around for a powerful 48vdc supply solution I landed on a fair priced Eltek Flatpack2 rack unit. I know, it is an overkill for HAM shack use with its 8kw of DC output power. But as Jeremy Clarkson says; quote “Power and speed solves many things”  🙂
Anyways, this really is a part of a telecom UPS system, and telecom 48vdc system has negative distribution with positive common return rail. This is the opposite of what we HAM usual needs, so it has to be rewired, or re-bared rather.
This is a 2U rack module with a smartpack2 controller and 4 x Flatpack2 2000w HE rectifier units. You can run a single rectifier without the controller but it will default to about 53,5 volts. In order to change the operating output voltage, you need the smartpack2 controller.
With the factory access password, you can with the controller permanently write new settings down to the rectifier, and it will default to any valid voltage value. Of course it is possible to hack and reverse engineer the eltek CAN-bus protocol with other tools. I know the e-bike community has done it.

Here are some pix:

Smartpack2 rack without load fuses cover panel.

Smartpack2 rack without load fuses cover panel.

Smartpack2 rack unit

Smartpack2 rack unit

Original common positive (+) return bar.

Original common positive (+) return bar.

Rewired to common (-) negative return bar.

Rewired to common (-) negative return bar.

20161106_122309c

Load fuses

Complete unit

Complete unit

PowerSuite for M$ windows config and monitoring tool.

PowerSuite for M$ windows config and monitoring tool.

This morning I decided to do some work on the good old Kenwood TS-2000.

The MULTI/CH encoder is operating erratic and has getting worse lately. I replaced that with new one.

The MULTI/CH encoder is operating erratic and has getting worse lately. I replaced that with new one.

Replaced the 144MHz UHF-type antenna connector with a N-type jack.

Replaced the 144MHz UHF-type antenna connector with a N-type jack.

Installed the 1.2GHz Tx Distortion mod/fix by VE2ZAZ

Installed the 1.2GHz Tx Distortion mod/fix by VE2ZAZ