Saturday, 17 January 2015

Yet More 630m Activity!

Another VE7 has been bitten by the 630m bug ... well, intrigued enough to start building a station. On the weekend VA7MM (Mark), in Port Coquitlam, asked if I could take a listen for his low power signal. I'll let Mark describe his setup:

"My transmitter is a HP8640B signal generator. It is stable and has 1 Hz
frequency readout with maximum RF output of 20dBm. CW keying was done by latching the antenna on and off of the HP8640B. The latching relay was driven by the send relay in an IC-746Pro running with full break-in CW
turned on. A 1N914 switching diode was installed across the relay coil as
the back EMF from the relay was measured using my oscilloscope to be a +50V spike. This effectively attenuates the voltage spike. A good safety
precaution before installation.

A second HF radio, an IC-7600, was on a separate wire antenna for receive
only and with Spectran running for signal analysis.

In the final setup three series coils totalling 330 uH and a series of
parallel variable capacitors adjusted to about 1000 pf were installed in a
series resonance circuit outdoors at the base of a sloping dipole with the
apex at about 40 m. The antenna outside shielded and center conductor were connected effectively making the antenna a vertical. There was no impedance matching. One ground radial about 300' long was laid out laying on the surface of the ground. The resonance circuit was tuned using a combination of a Blackberry Z10 smart phone real time video chat link of Spectran from the ham shack in combination with a portable VHF audio feed to both visually and audibly tune the resonance circuit for maximum output. I tried a parallel resonance circuit but it did not work.

The straight line distances between QTHs from Google are:

VA7MM to VE7SL: 60 km
VA7MM to VE7CNF: 10 km

Amazing that a piece of lab equipment can be enabled with a few hours of
tinkering to transmit a signal on the 630 m band a distance of 60 km.

Thanks for the first 630 m band contacts. It was fun. Now I'm going to start planning a permanent capability on 630 m."

Mark's setup reminds me of a Rube Goldberg machine but it all worked well enough for him to put out a solid 559 signal at 60km distance and provide his first official 630m contact.

As of today, the following VE7 stations have now made two-way contacts on the new band:


It would be great to see some activity from northern BC, VE6, VE5 and points further to the east. How about it fellas?

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