29 September 2013

Transmitting on 23 cm (thinking of)

After one year of SWL'ing on 23 cm I feel I would like to have a QSO up there. Besides buying a transceiver for that band, another option is a transverter. Current DB6NT catalog lists a 144 to 1296 transverter for 425€ built, or 199€ in kit (SMD). But how about a simpler solution? I came up with:
  • a Si570 generator/kit, at 60€ or so, and it requires a power amplifying chain
  • a frequency multiplier
While checking if any of my XTALs or canned oscillators would fall within 1296 MHz, it occured to me that 1296 is an integer multiple of 144 and 432 MHz. This observation led me to explore the almost forgotten world of multipliers and I met the varactor component.

A varactor is a sort of high power varicap diode which is able to return a signal tripled in frequency with a 35% efficiency, all with passive components. FM or CW only. Since I own a 30W UHF transceiver, I potentially have a 10W CW 1296 MHz transmitting chain. I think this technology has been almost forgotten, while today it would allow many amateurs to give 23 cm a try.

A quadriband transceiver will transmit on 70 cm (or at least 2m if using a 5x multiplier), and they are very popular => no additional cost.
An RTLSDR stick will provice wideband 23 cm coverage for 20 USD.
A computer is then needed as part of the receiver, but I would say most HAMs own one => no additional cost.

So, for the cost of a RTLSDR and a varactor multiplier you can be active on 23 cm (CW/WBFM). Not bad.

24 September 2013

Inside Gould 4072 DSO - bottom side

Out of curiosity (and giving a shot at troubleshooting the item), I opened the bottom lid of a Gould 4072 DSO. Top view has been studied back in 2009.

The darker board consists of analog signal processing circuitry for the two input channels, while lighter green PCB carries flat connectors and interconnections for top-side boards. Fortunately this side is not subject to forced air cooling, so it has almost no dust accumulation and its side effects.

Edit 2014-02-11: I do not own anymore the Gould 4072.

13 September 2013

Gould DSO 4072 startup sequence

Filmed mostly for future self-reference in case it breaks: the startup sequence of a working Gould 4072 DSO as seen by the "operator":

Just plain through-hole technology from 1980's.

Edit 2014-02-11: I do not own anymore the Gould 4072.

03 September 2013

Breakfast with chamois

The old road.
Woke up at 5:30 (local), had a quick breakfast, drove 30 min up to a mountain pass and started hiking.

In about 30 minutes lone walk I joined a family of chamois having breakfast. The telephoto equipment was finally put into outdoor use.
Can you count them?

They followed me as I proceeded to a nearby peak.

I got few blowing warnings to keep the distance from them. My excursion ended on a SOTA peak and two FM contacts, but I was not chasing SOTA points.

It was really nice to be part of (almost incontaminated) Nature.

Here is a link to the area of my excursion: L'Alta via dell'Assietta.