[ARC5] Hacked R-27/ARC-5

[Robert Downs]

Mike explained the majority of the mods.  However, he didn't comment on another internal mod that will have been made if the phone jack on the modified MX-21 has audio on it.  And that is a wire added to whatever pin number that the hacker chose to connect the phone jack to.  The unmodified AN/ARC-5 receivers don't have the normal receive audio run to the front connector.  Because all of the receiver racks have headphone jacks on them.  So a phone jack was not needed on the C-24 Local Control.

One possible reason for using 1:1 helical gears instead of 1:1 bevel or miter gears is that the former is closer to being a true 1:1 ratio with little to no jitter whereas the latter is not and has a constant and well defined jitter.  The rep rate or frequency of the jitter is directly proportional to the tooth count and is caused by the fact that the actual line of contact between the driving and driven gear moves in and out as the gears rotate.

Robert Downs

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On Behalf Of mmab
Sent: Thursday, September 30, 2021 23:16
To: Michael Hanz; ARC-5 Mail List
Subject: Re: [ARC5] Hacked R-27/ARC-5

Thanks for answering my question, Mike, and for the information you sent on this modified R-27.

Now I'm debating what to do with this set.  It has more holes drilled in the front panel than were necessary for the remote tuning unit due other gizmos the previous own attached to the front panel.  For regular use it's missing the regular worm drive, spline bushing, dial and dial gears.  Otherwise, it's in good shape other than the MX-21/ARC-5 adapter, that came with it, with the usual ham mods for adding a switch, RF gain control and phone jack.

Mike, W6MAB

On 9/30/2021 7:14 PM, Michael Hanz wrote:
> It's an R-27 modified for remote tuning, normally with an ART-13.
>
> https://aafradio.org/docs/C-131.html has a rundown on the set.
>
> 73,
>  - Mike  KC4TOS
>
>


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