CN-25T RECEIVER/TRANSMITTER


THIS DOCUMENT UNDER CONSTRUCTION

Model : CN-25T
Type: 113-948
Tuning Range: 1.6 - 6.8 MHz? Assumed to be the same as the companion 108-944 receiver less the broadcast band.
Frequency control: 4 crystals are currently installed. in the example held by the SPARC Museum.  However, the frequency selector switch on the transmitter has 6 positions and the frequency placard on the front panel also has 6 positions. The placard is inscribed with 1630 and 2182 KHz

Mode: AM Phone only
Marconi ID: 113948
Spec: 106-997
Power input: 32 VDC at 10 amps.

Comment:  This transmitter also incorporates the Canadian Marconi 108-944 receiver. The call sign of VXMR remains a mystery.

The Use of 1630 KHz

Frank Statham provides more details on the use of 1630 KHz. "1630 kHz was a unique Canadian west coast maritime mobile working frequency.
Ships would call the coast station on the distress and calling frequency of 2182 kHz and then switch to 1630 kHz to pass traffic.  That 1630 channel was abandoned by the coast stations in the late 1980s or early 1990s.   The frequency was useful in that most household broadcast receivers could pick it up if the tuning was "tweaked" to receive the top end of the commercial broadcast band (ie - up to 1700 kHz).  This allowed folks who dwelled in the logging communities to hear weather reports and such, especially at night when that broadcast band opened up.

1630 kHz was also the bane of technicians.  All commercial transceivers and antennas were designed to work above 2 MHz.  We had to fudge the system with loading coils and padding here and there.  A wooden boat with a center loaded marine antenna and a copper plate on the hull for a seawater ground was the worst.  It could be tuned on 1630, but I suspect the antenna losses were pretty high!

Fishing boats used to complain about the coverage on 1630 from our coast stations.  We were pushing anywhere from 200 W to 1 kW into the antennas - it was not much.  I would squelch the complains by asking them how well they could hear the commercial 10 to 50 kW stations on the broadcast band at the same location.  Reception of the commercial stations was usually not much better.

Aanother thing was that Spillsbury & Tindall in Vancouver built and supplied many a radio to the small vessel fleet on the west coast.  Marconi did have a foot in the door, especially on the government vessels. When 1630 kHz was decommissioned, 2103.5 kHz replaced it. but by then, most of the traffic had shifted to VHF.  VHF had much going for it--simple installation (VHF antennas didn't go out of tune).  If you could install a CB radio, you could install a VHF transceiver.  VHF had more channels and the international agreement to have VHF cover the coastal confluence zone,  we had coast station coverage everywhere from Victoria to Prince Rupert" .

As one example, the Roughradio web page indicates that radio VAG, located at the northern tip of Vancouver Island, had the  following capability in the 1970s:   500 kHz Morse plus a working/calling  frequency of  2182 KHz, 1630 kHz plus other 2 MHz channels.; VHF maritime mobile Ch 16 and Ch 26. All channels were voice. Bull Harbor Radio, VAG, closed its doors in 1989 as part of a cost cutting move.
 

cn25t_01.jpg
CN-25T front view. The call sign of VXMR painted on the chassis isn't a Canadian coast station call sign. They all started with VA*. ( ie  VAK VAJ VAE VAI etc.) , The final amplifier configuration is a pair of 807's in parallel which are modulated by a single 807.
cnt25_02.jpg
CN-25T front view with protective panel removed. This example is held by the SPARC Museum in Vancouver. The PA tuning components are located behind what appears in the p. hotos to be the back panel. Also behind that panel is the dynamotor. The switch located to the right of the VR-150's is for the meter, selecting which parameter to measure during tuneup after installing a new crystal
cnt25_03.jpg
CN-25T nameplate. 
All CN-25T photos in this table by Tom Brent. 

The call sign VXMR was assigned to the vessel DALMARIA which belonged to the Francis Millerd and Co. per the 1949 listing in Sea and Pacific Motor Boat Handbook. The Millerd Company existed from 1942 ro 2002. According to ITU publication "Alphabetical List of Call Signs" of the radio stations appearing in the 14th edition, Nov. 1950, the call sign VXMR was assigned to the Canadian vessel DALMACIA. The correct spelling of the vessel's name is not known at this time.

EXTRACT FROM SEA & PACIFIC MOTORBOAT HANDBOOK

/cn25_dalmaria.jpg
As found, the CN25T had the following crystals installed: 1630, 2015, 2142, 2182, 2318 and 2738 KHz


Contributors and Credits:

1) Tom Brent <navyradiocom(at)gmail.com>
2) Frank Statham <fstatham(at)gmail.com>
3) Station VAG  http://www.roughradio.ca/history_next/bull_menu.html
4) VXMR  https://books.google.ca/books?id=AFUeAQAAIAAJ&q=vxmr+ship&dq=vxmr+ship&hl=en&sa=X&ved=0ahUKEwibtKLpxd_YAhXq64MKHSwMAc0Q6AEISTAH
 
 

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Mar 21/18