[Milsurplus] LV on ARC RX

[boeing377 at gmail.com]

Correct. My ARN 6 still has the spare.

When I was in high school I put an ARN 7 on my dads commercial fishing
boat. Got almost everything from Fair Radio. Built my own 12 VDC to 110 VAC
400 hz inverter borrowing heavily from one designed by Linear Systems in
CA. Used a 400 Hz Variac and rectifier diodes and filter capacitor to get
28 VDC for the receiver relays and ratcheting bandswitch.

Tweaked osc coils on band 4 to cover 2-3 MHz marine AM signals. Worked
really well. I made a non proportional steering interface that connected to
our Wood Freeman model 11 vacuum tube autopilot. I’d swing the loop so it
was oriented 90 degrees to the bow so that a null would be dead ahead. Shut
off loop motor power which stopped loop rotation. The interface allowed the
autopilot to seek the null heading. Turned the boat instead of the loop.
Bingo. Coupled approaches to NDBs that had continuous signals such as the
one on the Farallon Islands off San Francisco.

I preferred the ARN 7 to the ARN 6 for ADF performance on weak signals, but
for ease of installation and maintenance and repairs the ARN 6 was the
clear winner.

The RCAF had some ARN 6s modified to cover 2-3 MHz for maritime SAR work.
Relabeled ARN 44. Jerry Proc had a great writeup on these.

http://jproc.ca/rrp/rrp3/tracker_arn44.html


http://jproc.ca/rrp/rrp3/tracker_arn6.html

Mark
AF6IM







On Mon, Sep 8, 2025 at 9:03 AM B. Smith via Milsurplus <
milsurplus at mailman.qth.net> wrote:

> The ARN-6 needed the 400 cycle AC via the vibrator to make the "needles"
> work. Vibrator Failure resulted in a usable receiver but a frozen needle
> and the fun began- you could still turn the aircraft to take a aural null -
> but the secret was there was a spare vibrator attached  inside of the
> receiver lid.
> k4che
>
>
>
> On 9/7/2025 11:10 PM, boeing377 at gmail.com wrote:
>
> Add R 392 to that 28VDC B+ list. I found better performance with higher
> plate voltage but not enough to justify any permanent mods.
>
> ARN 6 was so much easier to install than SCR 269
> or ARN 7 which both required 400 cycle 110 VAC.  ARN 6 needed high
> frequency AC for the
> selsyns  but it used a 28 VDC vibrator to accomplish this.
>
> Mark
> AF6IM
>
>
> On Sun, Sep 7, 2025 at 2:09 PM Charlie L. <mjcal79 at gmail.com> wrote:
>
>> I have run every ARC 5 receiver I have on only 28VDC B+.  Have to use a
>> set of headphones, but with a clean DC supply, feeding 28 to both filament
>> and normal dynamotor B+ pin, they work fine.  The ARN6 RDF uses all common
>> tubes and runs only 28 on the plates.  I have never analized the ARC 5 on
>> 28V B+, checking sensitivity and selectivity, but just for normal
>> comparisons, seemingly  very little difference except for audio power out..
>>
>> Charlie W4MEC in NC
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