Injection moulding machine problem

It was a crisis call for a table-top injection moulding machine. Clear acrylic meter faces were being moulded and the output quality had deteriorated overnight.

The controls were fairly simple, the key ones being those for temperature control of 3 zones. Temperature setting was through potentiometers with graduated dial plates. The instruction manual had a chart listing the 3 settings for various plastics.

The easiest way to check whether the temperature controllers were working was to connect bulbs across the heating elements and observe the change in the switching while changing the settings. All 3 tested okay.

When I was mulling over the problem the owner excused himself for a while.

Then 'Eureka'! I turned the knobs fully anticlockwise and the pointers were not at 'zero'.

All I had to do then was to loosen the knobs to rectify that.

After changing back to the settings for acrylic, the machine was back in business!

Speaker vibration/distortion

A Radio Cassette Recorder was received for repair.

The problem: Speaker vibration/distortion within days of its purchase in another city.

On opening the set, a cockroach was found perched on the back of the voice cone. It appeared to enjoy the vibration, for it wouldn't budge even with the volume turned high.

Without getting into details, out went the cockroach and along with it the vibration/distortion.

It was my fastest repair job, ever!

My first satellite QSO

My first satellite QSO was with my good friend OM Bindu - VU2IR.

It was around 6.00pm, one evening in the early 1990s, when Bindu and I were chewing the rag on 2m and he excused himself to work through a satellite.

I was curious when he said he would work SSB via RS-12 with a 21MHz uplink and 145MHz downlink and would I care to join?

With hardly 10 minutes to go, I hurriedly set up a Yaesu FT-757GX (just serviced and ready to be delivered) with my 40m inverted 'V' dipole antenna for the uplink. My homebrew 2m converter and ¼ λ ground plane antenna would serve for the downlink, with my RCA BC312-D receiver as the tunable IF stage (see My homebrew 2m FM rig for more details). And my first satellite contact was thus established.

Fortunately, it was just the two of us and we continued our ragchew for the duration of the pass. With OM Bindu just 5km away, it was once again proved that the long way round is the short way!

Remembering radio pioneer J.C.Bose

Here's a comprehensive article on radio pioneer J.C.Bose.

J.C. Bose: 60 GHz in the 1890s

Interesting read.

Crystal Radio Circuits - Alternative Concepts

The most commonly used circuit is parallel-tuned.

Conventional Crystal Radio Circuit
The high-impedance parallel-resonant circuit requires high-impedance phones (around 2kΩ) series-fed through the detector. Use of  low-impedance phones in this circuit necessitates the use of a transformer.

The alternative circuit is series-tuned.

Alternative Crystal Radio Circuit
The low-impedance series-resonant circuit requires low-impedance phones (around 300Ω) shunt-fed across the detector. Low-impedance 'Sound-powered' / 'Balanced-armature' phones are well suited for the purpose.

Remembering OM Joe - VU2JA

My memories go back to a day in the year 1976 when OM Ramesh - VU2NRS and I had an eyeball 
QSO with OM Joe - VU2JA at his shack on # 20, Union Street, Bangalore.

It was in an imposing building with a tiled roof.  More imposing was the antenna, strung well 
clear of the roof, between two tall ground-mounted masts.

On the huge wooden shack table was an open-frame vacuum-tube CW rig, coax-coupled to a big open-frame transmatch mounted on the wall. Entry of the ladder-line feeder into the shack was through a ventilator high up on the wall. The sight of  the homebrew transmatch, with its neat copper coil and variable capacitors, is still etched in my memory and so is Joe’s characteristic CW sending.

Joseph Alexander Faithful was born on 11th April 1898 in Calcutta. In the year 1914, working as a deckhand for his passage, he sailed to England to take up a course in Mechanical Engineering. But fate willed otherwise. War broke out when they neared Hamburg. Joe was also taken prisoner and released only six months after the war was over.

More on his incarceration at:

In England after his release, Joe qualified in wireless telegraphy and, after a fulfilling career, retired and settled down in Bangalore.

Joe married Hildred Joyce Dique at Karachi in the year 1934. They had no children.

More details including that of his career and ham radio activities at:

He was an Amateur Wireless Pioneer, a member of the Old Old Timers Club, USA (OOTC # 695).

OM Joe passed away on 25th January 1985. Hildred followed on 31.10.1988, bequeathing their property to the following in Bangalore for religious and charitable purposes:

Little Sisters of the Poor, Missionaries for Charity, St. Michael’s Convent, Christu Seva Samaj, St. Mark’s Cathedral, Bangalore Cheshire Home, Bangalore Children’s Society, Kidwai Memorial Institute of Oncology, St. John’s Medical College & Hospital.

Memorable lives indeed.

QSLs from India