Skip to main content

MMR40 L1/L2 Connections

 

MMR40 L1/L2 Connections

Filed in Kits on Feb.25, 2009

One of the members of the MMR40 Yahoo Group is having difficulty getting his MMR40 PTO to oscillate.
We had worked out how to wind the L2 coil, based on the pads of the Homebrew version being different than the pads of the Kit version.

We didn't look close enough at the feedback winding pads, though. In the Homebrew version, it appears that you have to swap the ends of the feedback winding, in order to keep the feedback in phase with the main winding.

Here is how I think the feedback winding needs to be connected for the homebrew version:

L1/L2 connections for Homebrew PCB

As opposed to the way L2 is connected for the Kit version of the PCB:


L1/L2 Connections for Kit PCB

The thing to watch is that the windings have a hot end and a cold end. If you start at the hot end of a winding, the other end is obviously the cold end. If you connect a second coil in series, off of the cold end of the first, as we do here, That point is the hot end of the second coil.

To take it a step further, the ho€ end of the feedback coil is the end nearest the cold end of the primary coil, when you wind the feedback as if it were a continuation of the primary, then cut the wire to separate the primary from the feedback.

So, while a properly wound L2 in the Kit will just drop straight into the holes in the Kit PCB, the pattern for the Homebrew version forces you to cross the leads of the feedback winding to keep it in phase. If the feedback is out of phase, it is providing negative feedback, which does not make a good oscillator!

Comments

Post a Comment

Popular posts from this blog

Building the W8NX Short Trap Dipole

Image
  Building the W8NX Short Trap Dipole Filed in Antennas on May.31, 2021 For the past five years, I have been operating the lower bands (30, 40 and 80 meters) with a trap dipole that was modeled after a web article written by John DeGood NU3E. [1] While the antenna performed well, a monsoon storm last summer beat it up enough that the antenna wire broke at the center balun. So I climbed the tower and lowered the remains of the antenna to the ground for repairs. On closer examination, I discovered that the relentless Arizona sun had taken its toll on the traps. The insulation on the exposed ends of the coax had rotted away. They were still working, but would need to be rebuilt and weatherized to insure good operation many years into the future. Since I was going to have to rebuild the antenna, I started thinking about whether this antenna met my current needs and wishes. I had been wanting to get on 160 meters at this QTH for some time, but my small back yard would
Read more

Yaesu G-450XL Rotator Repair

Image
  Yaesu G-450XL Rotator Repair Filed in Antennas on Dec.30, 2007 In December of 2007, the rope support for the center element of my Cushcraft A3 broke, requiring me to climb the tower and bring the beam down for maintenance.  At the same time, at had been noticing that the rotator control was not indicating correctly, it was very erratic.  So I brought the rotator down for maintenance, as well. The first step was to mark the side of the case, where the top and bottom of the clam shells connected together.  This would allow me to assemble it in the correct alignment when the time came.   Marked Case of Rotator Next, I took the top cover off.  All of the bearings between the clam shells in the depression on the outside were safely stored.   Top Removed A little inspection revealed what the problem was.  The center gear had broken away from the shaft it was pressed onto.  I tried re-pressing it back onto the shaft, but it was too worn out.  I found the phone number for p
Read more

JuncTek Battery Monitor MQTT Controller

Image
 I recently installed some 48 volt Lithium Iron Phosphate battery packs at the Ranch to replace the 9 year old Lead-Acid batteries that had started to fail.   eg4-lifepower4-battery-48v-100ah   These are rack-mount battery packs that are intended for powering computer servers.  They are reported to work very well in an off-grid power system.  The Problem I had a problem to solve before the upgrade, in that the old 48 volt inverter I had been using in our solar power system required a programming interface to change its operating parameters to match the new battery specifications.  Unfortunately, the manufacturer wants over $400 for the required interface to make these changes.  I am unwilling to pay this extortion money for a simple device that should cost less than $100. The communications protocol and interface is proprietary, so it would take a considerable effort to hack the interface. There are two sets of parameters in dealing with the inverter/battery connections: 1. The chargin
Read more