Friday, November 7, 2014

Looking inside a 144 - 432 - 1296 triplexer

It has recently come into my hands a 144 - 432 - 1296 MHz triplexer. A Comet CFX-4310. I was curious, so I opened it:

Tuesday, October 21, 2014

Sunspot region 2192 with a compact camera

These days a really large sunspot is visible on the sun. It's so big it is visible to the naked eye. I tried to take a photograph of it, just for fun:

Sunspot region 2192 on October 21, 2014

Wednesday, August 20, 2014

Revisiting DC blocking solutions for DC damaged IF filters

During these last years a new problem appeared in many commercial ham radio equipment, from many manufacturers. The receivers suddenly become deaf, hearing only really strong signals. The problem is the premature failure of IF filters, because DC is applied to them. Why?

Because applying DC to these piezoelectric devices causes electromigration, and therefore the filter destruction. Manufacturers warns about applying DC to the filters, but manufacturers have been ignoring this for decades.

A transceiver with this problem can be easily repaired by just replacing all the damaged filters, and to prevent this problem to appear again, a pair of DC blocking capacitors must be inserted at the filter input/output pins. In fact some manufacturers have modified their PCB in latest revisions to add these capacitors. But are these capacitors enough to keep DC out of the filters?

Tuesday, August 19, 2014

Simple phone battery test

Do you suspect from your phone battery? Testing today's mobile batteries is very easy: Lay it over a flat surface and make it to spin.

Friday, July 18, 2014

Installing BG7TBL noise source as poor's man tracking generator

After finishing the modification to the BG7TBL noise source, and put it in a shielded box, it was time to place it inside the spectrum analyzer, so I could use it as a poor's man tracking generator.

Wednesday, July 16, 2014

Modifying BG7TBL noise source

I own an old IFR-A7550 1GHz spectrum analyzer. It works fine, but lacks tracking generator, so its usage is somewhat limited.

The tracking generator for my unit is difficult to find, and very expensive, so aimed by Iban, EB3FRN, I explored other solutions, for example a noise source.

Friday, July 11, 2014

Getting 1PPS signal from a Bluetooth GPS

Recently some new experiments have been added to the (large) TO-DO list. For some of them, a time reference signal will be needed. So why not to use GPS timing? I have some old GPS in the junk box, so I could try to get the desired 1PPS signal from one of them.

One of the units is a Fortuna On Clip Bluetooth unit. This unit has been with me more than five years. The bluetooth side died, but the GPS side was still working, so I keep it to use in a future, maybe with a microcontroller. Also, this unit has connector for external antenna, so it is ideal for me. But, does it has the 1PPS signal?

Wednesday, July 2, 2014

Transverter rework

I have spent this weekend to rework the 10 GHz transverter. After one year since I finished it (but only three months of operation) it was time to fix some minor problems it showed.

Wednesday, May 7, 2014

One month in 10GHz

Last weekend I completed my first month in 10 GHz, and now it's time to put all the experiences together trying to get some conclusions.

Sunday, March 16, 2014

Using old walkies with Li-ion batteries

Like most hams, I have some old equipment. To be precise I own an FT-911 walkie, who uses from Ni-Cd batteries. The original battery died many years ago. Because nowadays it is difficult to get Ni-Cd batteries, I rebuild the pack using Ni-MH batteries instead.

No matter what brand of batteries you choose, or what kind of charger you use with them: they will be dead in just few months. I'm really concerned about the quality of Ni-MH batteries today. Because I really got tired of replace the battery cells, I looked for a different kind of battery. What about Li-ion batteries?