AN/ARN-44 Radio Compass

Radio collector Tom Brent documents what he has learned about the AN/ARN-44 from available evidence as outlined in the summary below.

“Most of what follows is based on the equipment which was removed from the inventory of ex-Canadian Armed Forces Trackers sitting at Abbotsford Airport and owned by Conair Aviation. In the early 1990's, 27 or 28 of these aircraft, the last  in the Canadian military inventory were purchased and flown from Trenton to Abbotsford with the intention of converting them into fire bombers. When I first looked at these aircraft, it appeared that most, if not all, had been stripped of any radio equipment except for the AN/ARN-44 radio compass.

Only two of the Tracker aircraft at Abbotsford were found to be equipped with R-101A/ARN-6 radio compass receivers. One of these radios had originally been ordered and used by the RCAF while the other was an ex-Royal Canadian Navy unit, appropriately painted gray. All the other receivers found in the Abbotsford Trackers were labelled as R-713/ARN-44.  I currently have four receivers in my possession which were removed from the Abbotsford Trackers - two ARN-6's and two ARN-44's. All of them were manufactured by Northern Electric in 1955.

Magnavox in the US, also  produced the R-713/ARN-44 and it appears in a copy of  a Magnavox  manual T.O. 12R5-2ARN6-2 (February 12, 1969).  The pages in this manual devoted to the ARN-44 are dated August 15, 1958 and indicate the radio was made by Magnavox. This information is not shown in my December 29, 1955 version of that same manual. Based on the fact that  the ARN-44 is shrouded in obscurity, it would appear that relatively few were factory produced. I believe all of the ARN-44 receivers found in Abbotsford were originally manufactured as standard ARN-6's, covering 100 to 200 KHz on Band 1. Further, in 1968, Presentey Engineering (Ottawa) converted at least 165 ARN-6 sets to cover 2.0 - 3.5 MHz on Band 1 and relabelled them as R-713/ARN-44. My reasons for believing this are as follows:

Although the nomenclature plates on these radios identify them as R-713/ARN-44, the part number on the plate reads "R-101A (MOD)" which I would assume to mean "modified R-101A". According to photographs in manual T.O. 12R5-2ARN6-2, the “from-the-factory” ARN-44 should have the loop, antenna, RF 1, RF2 and RF oscillator compartments labelled L-3101 through L-3106. The Abbotsford Tracker ARN-44's are labelled L-101 through L-106, the same as a standard ARN-6.

tracker_arn44_coil_set_s.jpg Besides the modified Band window in the Control Head, the other distinguishing feature between the ARN-6 and the ARN-44 is the relabelled coil set. In the ARN-6 the coil sets is marked L101, 103, 104, 105 and 106  but in the ARN-44 it is marked L3101, 3103, 3104, 3105, and 3106. Click to enlarge (Magnavox photo via John Mackesy)
The ARN-44 sets I have were manufactured in 1955; manuals currently known to exist do not indicate the ARN-44 was available at that time. Nomenclature plates found on the ARN-44's in Abbotsford are attached with adhesive. Unused screw holes around and behind these plates as well as paint lines indicate that another ID plate was previously attached to these radios. The size of the plates which were removed is the same as ones on my unmodified ARN-6 receivers. Additionally, the ARN-44 plates identify the owner as "DEPT. OF NAT'L DEFENCE - CANADA"; this identification was not in use when these radios were manufactured in 1955 (ie before the Unification of the Canadian Armed Forces in 1968).

Modifying the ARN-6's to cover 2.0 - 3.5 MHz would have been a relatively simple task in 1968; the engineering had already been done for a factory produced ARN-44 that was little different from it's ARN-6 predecessor. When the Canadian military wanted a different frequency coverage for some of their ARN-6's, all Presentey Engineering needed to do was order and install the parts, align the new band and stick on a new ID plate with a new serial number.

I retrieved one ARN-6 control box from the Abbotsford Tracker fleet and it has an nomenclature plate that reads (in part):

Royal Canadian Navy
Control Panel ED-200
Part of AN/ARN-6 Radio Compass

The ARN-44 control boxes found in Abbotsford read (in part):


Once again, we find a notation that indicates these controls were once standard ED-200 units (used with standard ARN-6's) that had been modified for use with the ARN-44. The only obvious difference between the ED-200 and C-5161/ED-200(MOD) is the dial scale on Band 1. I have 3 control boxes (one for the ARN-6 and two for the ARN-44) and all were made by North American Phillips in 1955. These control boxes should not be confused with the C-1514 which, although appearing similar when viewed from the front, uses a different connector and therefore the two types (ED-200 and C-1514) are not interchangeable.

When I first came across my Royal Canadian Navy ED-200 control, I assume the "ED-200" identification was an in-house RCN number because it did not follow the standard (and familiar to us all) numbering system associated with military radio equipment. However, radio collector Keith Harrington has a control box pulled out of a DHC-3 Otter that carries an RCAF part number (10EA/49881) rubber stamped onto the case. The ID plate on this control reads "ED-200 - North American Phillips"........there is no mention of Canada or any military force. I wonder, is it possible that ED-200 is a North American Phillips commercial part number?

Further investigation is needed to determine if the Canadian ARN-6 and ARN-44 radios were interchangeable - in other words, if an ARN-44 would work in a rack from which an ARN-6 had just been removed. The ARN-44 manual indicates that the two factory-produced radios should have been interchangeable. However, I removed two ARN-44's from Trackers in the late 1990's and, if memory serves me correctly, the collector that received one of them indicated to me that the receiver and mounting rack connections were different from what was shown in his ARN-6 manual.

There is one other (and big) mystery in the ARN-44 story. How was the ARN-44 designator acquired from the Joint Electronics Type Designation System (JETDS) authority?  Did  Presentey Engineering or Magnavox or DND  apply for it?“   If anyone can explain,  please contact:

Radio collector John Mackesy offers information about his factory built AN/ARN-44.

“According to my copy of T.O. 12R5-2ARN6-2 the R-713/ARN-44 is essentially the same as an ARN-6 except for frequency coverage. My R-101B/ARN-6 was built by Magnavox.

Band 1 - 2.0 to 3.5 MHz
Band 2 - 200 to 410 kHz
Band 3 - 410 to 850 kHz
Band 4 - 850 to 1750 kHz

The Control Panel is a modified C-403A/A, Magnavox p/n 708224 lighted plastic dial for use with Magnavox manufactured  R-713/ARN-44. Alternately, a modified Control Box C-1514A can be used, Magnavox p/n 708225 to suit ARN-44. Some of the RF coils are different, but overall the ARN-44 looks the same and is mostly the same as an ARN-6.

The need to modify the set was likely driven by the requirement to monitor two frequencies, namely:

* 2182 KHz - MF International distress frequency for ship, aircraft and survival craft.
* 3023 KHz - Communications between mobile stations engaged in coordination of search and rescue.

There is only one known American aircraft to use the ARN-44 and that was the Convair HC-131A "Samaritan” aircraft flown by the US Coast Guard.

AN/ARN-44 receiver. The highest serial number found to date is #165.
AN/ARN-44 receiver nameplate.
This is the warning tag which limits the use of the ARN-44 to three Canadian aircraft only. 
Control Panel C-5161/ARN. Part No. ED-200 (MOD). It is similar in appearance to C-1514, shown in the ARN-6 manual. After the modification, the HF band was squeezed onto the scale with the smallest arc, which resulted in 100 KHz being covered in just a mere 1/4 inch of dial travel but at least there marks on the scale at 50 KHz intervals. So much for accurate frequency readout! In contrast, when the LF band resided on this portion of the dial, 10 KHz was spread over almost 1/2 inch.
Control panel nameplate
All photos in this table by Keith Harrington VA7SSB

The Loop antenna is an iron core loop which is rotated by a drive motor through a reducing gear train. A compensator, which can be adjusted externally, is used to correct for radio compass deviation error. An autosyn transmitter is geared through the compensator to the rotatable loop and supplies loop position information to the remote indicator system. The entire loop unit is sealed and filled with dry nitrogen. It cannot be opened without special equipment. Electrically speaking, the loop antenna uses a low impedance iron core loop of nine turns, is electrically centre-tapped by means of a shut coil of 12 turns and electrostatically shielded. It is directional in that the voltage induced in the loop is maximum when the line of travel of the received radio wave lies in the plane of the loop coil . The resultant voltage induced in the loop in the loop is 90 degrees out of phase with the non-directional antenna and leads or lags according to which edge the loop coil is nearer to the signal source.

ARN-44 loop antenna with close up of namplate data below. (Both photos in this table by Keith Harrington VA7SSB)

Tracker ARN-44 loop antenna radome. The duct in the foreground is an air outlet for cooling the electronics. A black/red bar holds the folded wing in place.  (Photo by Jerry Proc)


Sense antenna- The non-directional antenna input circuit of the receiver is designed to operate from a low capacity transmission line connected through the proper matching circuit to a conventional antenna having an effective height of from 0.05 to .5 meter.
ARN-44 sense antenna placement on a Canadian Tracker. The inset shows the detail of the feed through method. (Photo by Jerry Proc)


The output of the ARN-44 could be displayed on a standalone instrument such as this ID-307/ARN. 
ID-307 identification label. 
The ID-250/ARN  Radio Magnetic Indicator can also be used with the ARN-44. It has a rotatable azimuth 'card' fed by the compass system. 
All photos in this table by Keith Harrington
Back To Tracker Equipment Listing
Credits and References:

1) Tom  Brent <tgb(at)>
2) Keith Harrington  <>
3) John Mackesy  <mack(at)>

Mar 22/10