March 1, 2018 Club Meeting

Thursday, March 1, 2018 at 7:00 PM Red Cross Building, 60 Hawthorne St., Medford, OR (across from Hawthorne Park)

Program: History of Radar

NOTE: This program was originally scheduled for the February meeting, but due to time constraints was not able to be presented. We have tentatively re-scheduled it for March. If it is not given in March then we will substitute a contingent program on either: Transmitter non-linearity, distortion, and spectral widening, or else a presentation on The use of ferrites to make common-mode feedline chokes. Either of these would perhaps use presentation material written by Jim Brown, K9YC.

Announced in the March 2018 issue of The Repeater.

Meeting Notes

From the April 2018 issue of The Repeater.

2018-03-01 March Rogue Valley Amateur Radio Club Minutes

The March meeting was held in a conference room east of our prior meeting room, as the sale of the Red Cross building to United Way is in progress.

President Allen Taylor, K7GT, called the meeting to order at 7pm. 29 attendees were present.

It was mentioned that future meetings may be held at a new Red Cross location at 1050 Crater Lake Avenue, across from Providence Hospital. The Suite # was still unknown.

Mike Bach said that the Scala-Kathrein cafeteria might be a viable location for the RVARC flea market, and that Science Works asked about whether we wanted to use their location for Field Day 2018.

Jerry Fulstone, K6KSI, said a GOTA station would be there at ScienceWorks in October for the BoyScouts.

Treasurer’s Report: After paying a late arriving bill from last year’s Field Day, the current bank balance is $5090.04 with an additional $75 in petty cash and $110 in checks from CARE for dual-membership dues.

Darrell Barker, N7CZX, advised that the CARE club has a float in this year’s Pear Blossom Parade, April 14. They will also have a truck with so many antennas that it will look like a porcupine.

There was a short break for coffee and visiting at 7:14pm, prior to the presentation.

At 7:32pm, Tom McDermott, N5EG, gave the presentation on signal cleanliness in transceivers, based on a talk given by by Bob Wolbert, K6XX and Jim Brown, K9YC, at the 2013 NCCC ( www.nccc.cc/pastmeetings/2013/11nov2013.html ). The slides are available at k9yc.com/K6XXAmpTalk.pdf More good info is also available at k9yc.com/publish.htm

A summary of the main points were:

Local Osc Phase Noise Hurts both TX and RX quality.
Key Clicks are generally due to fast rise/fall time on the modulator. 5-6 mSec rise/fall time setting is good to minimize key clicks.
Usually, having ALC “on” is bad because slow attack = overshoot. Turn off ALC.
Transceiver IMD can be helped by running at half maximum power. Also IMD at 13.8V power supply voltage is noticeably better than at 12.0V and IMD is best with a 50 Ohm load.
Tune your antenna.
Adjust power amp bias for best linearity.
Slightly increase loading (then readjust tune) to improve linearity and reduce grid current
Minimize power supply hum.
On the audio side, don’t overdrive the mic input (to minimize splatter), and “Don’t Crowd Your Mic”, also cut bass below 300 or 400 Hz.
Be careful to not over compress. Adjust compression carefully, and monitor the audio quality.

There were many good spectrum analyzer slides illustrating these points with an ICOM 7600.

After questions, the meeting was adjourned at 8:25pm due to possible icy weather coming.

Tags: meeting