March 5, 2020 Club Meeting
Thursday Mar 5 2020, 7:00 PM
Medford Police Department Community Room
219 S. Ivy St., Medford, OR
Programs:
- 1917 Ham Station
- Favorite DX Tools
Mini-program
- 1917 Ham Station
Mini program: Overview of an amateur radio station, circa 1917 in Lud Sibley’s possession. It’s, of course, a spark rig. The owner was a recipient of the Navy order requiring amateurs to take down their antennas and lock up their gear when we entered WW I. (The inheritors of the material had the letter but didn’t pass it along.) The gear is a small spark coil, fixed ceramic-based spark gap, big “oscillation transformer,” capacitor made up from 8 x 10 photo plates, slide tuning coil, and vintage headphones.
Biography: Lud Sibley, KB2EVN is a long time club member, historian, and president of the Vacuum Tube collectors association.
Main program
- My Favorite DX tools.
Program: A collection of DXtools—clusters, propagation analysis, and other tools related to finding and working that elusive and rare DX station.
Biography: Scott Cummings, NA7OM is the club vice president, DXer, and contester.
Announced in the March 2020 issue of The Repeater.
Meeting Notes
From the April 2020 issue of The Repeater.
RVARC Meeting Minutes 2020-03-05
7:09pm Meeting called to order by Tom, N5EG, since no President or Vice Present was available (and both the treasurer and secretary were busy). About 21 attendees present.
Discussion on the May 2-3 7QP contest location settled on either Agate Lake or the 3-county point on King Mountain, depending on the weather.
The June Field Day location was also to be Agate Lake, since there are minimum bureaucratic hurdles to surmount in getting permits there.
Treasurer, Mike Bach, WB6FFC, reported $1.25 in petty cash and a bank balance of $5108.38 that includes $314.50 reimbursement from the CARE club for half of 2019 Field day expenses plus dual membership dues.
John Laybourne, AC7S, said that a Middle School science teacher was asking if someone from the club could give a presentation on Amateur Radio at Kids Unlimited in April.
Pat, KD7MPA, has set up a web store for club swag at shop.k7mfr.org and any proceeds will first go towards a DMR repeater setup. The items are screen-printed on demand, so no funds are tied up in unused inventory. Shirts, jackets, mugs, pillows, and totes are available with the club logo or your custom design. Contact Pat for details.
7:20pm Presentation on an early spark-gap transmitter and receiver (from around 1917) by Lud Sibley, KB2EVN.
Lud showed several parts from the ’transceiver’ including wood-enclosed high-voltage coil, a stacked glass plate condenser made from 8x10 photo glass, ceramic spark-gap, vintage headphones, along with the F. B. Chambers’ Loose Coupled Receiving Transformer and (vertical) Oscillation Transformer. The transmitter power handling capacity was possibly up to a kilowatt.(images of the Chambers parts were featured in Lud’s article.).
The overall setup is shown in Fig 80 of Morgan’s 1916 book Experimental Wireless Construction.It was interesting to note the Fig 80 T/R switch was a cleverly modified DPST knife-switch. The Ham Station’s owner, Harry McWade, was ordered to dismantle and lock it up upon the US entry into WWI in 1917.(An entry for a Harry J. McWade of 26 Hillcrest Road, Watchung, N.J. is listed in the Jun. 30, 1920 issue of ‘Amateur Radio Stations of the U.S. as having callsign 3BEZ. Could he have been the owner of this set? [note added by John A., KF7UMK].
Another curious part in the Fig80 setup is use of a variable transmitting condenser made from paralleled test tubes in a rack, whose value is adjustable by adding or removing tubes from the set.The F.B. Chambers parts were also works of art in wood and copper.
Refs:
- Experimental Wireless Construction: A Practical Handbook Giving Detailed Instructions for Building, Installing and Operating Amateur Wireless Telegraph Apparatus, Alfred Powell Morgan 1916
- Reprint from August 1997 Radio Age: F.B CHAMBERS & Co.: Philadelphia’s First Radio Maker? showing #748 Loose Coupler and #914 Oscillation Transformer
7:32pm Break for snacks and visiting
8:00pm Second Presentation. (ed note: Scott was sick and not available to present the main program as previously scheduled).
Pat, KD7MPA, demonstrated the shop.k7mfr.org online store where T-shirts, mugs, etc can be ordered with custom logos. He also has plastic license ID cards available directly. Pat & Forrest showed the newly operational DMR repeater using a Motorola CDM1550 radio, with a MMDVM STM32 interface board and a raspberry pi computer. It is running on 442.8MHz CC1 (Color Code 1), at around 20 watts.
DMR ID’s can be registered at radioid.org
Many talk groups are accessible from Motorola’s dmr-marc.net or from the brandmeister.network
See Pat or Forrest for more info on how to get your setup going.
8:30pm Third Presentation
John, KF7UMK, demonstrated a portable SDR receiver setup to receive and decode natural-gas meter radio signals. The hardware was a raspberry pi with a Nooelec SDR dongle and whip antenna, (using the rtlsdr drivers) and the rtltcp and rtlamr programs working together to decode the AMR (Automatic Meter Reading) data that was transmitted by the meter around 912MHz. It decoded several neighborhood gas meters, and they can be filtered by ID#, which usually is found on the meter face.
More info can be found at:
- www.rtl-sdr.com/tag/rtlamr/
- github.com/bemasher/rtlamr
8:48pm Meeting Adjourned
- John, KF7UMK, Secretary
