Thursday, December 31, 2009

Glory Days: my high school science fair project

Everyone likes to talk about their glory days, in fact, I believe there is a song about this phenomenon. My high school science fair project occupied most of my glory days. Today I have posted complete photos, all documentation, and schematics from this project. It is a 1.425 GHz radio telescope receiver. The concept behind this system was that you use a swept frequency spectrum analyzer to detect, then, blank out narrow-band in-band RFI signals. This is necessary when operating a radiometer in an urban environment, where, RFI signals from computers and other things are prevalent and when it is desired to operate your radiometer over a (relatively) wide bandwidth. Similar techniques are utilized in other radiometer projects, except now the implementation is digital, using wide band digitization and FFT's. The implementation of my high school science project was completely analog. Quite the learning experience!

Hope that you can use some of these ideas on your own projects,


Saturday, December 26, 2009

1901 tabulation machine

New as the century! 1901 model. Tabulation machine company.

(photo taken at the Detroit historical museum)

Thursday, December 17, 2009

Update: Olympic model 6-606

This is the most challenging radio i have attempted to restore. I
now have AF coming out and i can tune in lots of AM stations. But,
the audio remains distorted. It is even distorted when i turn the
volume down all the way.

Very strange. I am running this by enthusiasts at
to see what the pros think.

Lots of fun though!! Stay tuned for more....

Saturday, December 12, 2009

restoration of an Olympic Model 6-606, a 1946 portable tube radio

As of last weekend i have started the restoration of a portable tube
radio, it is an Olympic Model 6-606. This radio was built in 1946.
It is cable of running off either batteries (two type B 45 V
batteries and two type A 4.5 V batteries) or line voltage.

So far, most of the wax and paper capacitors have been replaced and
most of the electrolytic capacitors.

Waiting on some mail order parts, including a new leather handle and
a high voltage electrolytic.

More to come later..... Stay tuned!

Sunday, December 6, 2009

From Motor City to Maker City, Maker Faire comes to Detroit!

This is very exciting, there will be a Maker Faire in Detroit, July
31-Aug 1, 2010. It will be at the Henry Ford Museum, which is my
favorite museum, an amazing place, learn about the evolution of
American industry and creativity. Looking foreword to this one.

To add to this, the Henry Ford is also a functional museum. For example, last December I dropped by the Wright Cycle Shop (yes, the place where the first airplane was developed), in the Greenfield Village part of the museum, i noticed that the grounds keepers drove Ford Model A's around for their work trucks (see photo above).

Tuesday, December 1, 2009

Restoration Complete! Zenith Model K725, Chassis 7K01

I am very excited because I just completed the restoration of my
Zenith model K725 (chassis 7K01). This radio has a build date of
February 22, 1954. It is capable of both the standard AM broadcast
band and the modern FM band (88-108 MHz).

The build quality is very good. The internals were very clean and
easy to service. It was very straight foreword to find things from
the schematic inside of the radio. I'm sure this radio was designed
to be serviced.

The audio quality of this radio is absolutely amazing! I think this
is largely due to the fact that its audio power amplifier is a single-
ended class A power amp with negative feedback. There is a tone
control knob that is located on top of the tuning indicator that
adjusts the frequency response of the feedback network for this audio
power amplifier. All of this results in a nice warm sound on the FM
bands. The local jazz program sounds amazing, especially when soft
jazz guitar or a mellow Hammond B3 organ song is played.

I will write up a web article on my site about this with more details
to follow soon.