[Milsurplus] BC-659 Fun and Games

Mon Jul 6 18:13:53 EDT 2026

Howdy Ray,

Yes, the RT-524 and RT-246 should operate on 29.6 Mc (red flag in Mc 
window).  Most, but not all will work down to 29.4 Mc.  The PLL in the 
synthesizer (or Crystal Reference System as they called it) has a 
relatively small pull-in range and so relies on the front panel gear 
drive mechanism (and the CRS Hunt Discriminator) to coarse tune the 
master oscillator close enough to pull in and acquire lock.  This 
mechanical coarse tuning action is not only from the megacycle steps 
knob; the kilocycles knob provides a vernier coarse tuning action 
between the megacycle steps.  The problem is that the gear drive vernier 
action stops at some point below 30 Mc, even though kilocycles control 
switching is otherwise normal.  The CRS will still pull in down below 30 
Mc--it's just a question of "how low can you go".   Best is to start at 
30.00, and tune the kc control backwards to the desired frequency.  
Check to be sure the radio works reliably there, as there's no transmit 
kill circuitry to mute RF output if the CRS unlocks, and you can end up 
transmitting out of band.

Some slight tweaking of the master oscillator can help on some radios, 
but you may cause problems on the 51 Mc end if you push it too far.  I 
think It may be possible to make some minor adjustments to the gear 
drive to pull in radios that don't make it down to 29.4.  Some day I'll 
get around to looking into it. Hopefully someone will beat me to it.

You may find it necessary to fuss with the stagger tuning of the driver 
and PA to get good power in the 29.4-29.65 Mc range and keep plate 
current in spec.   Go easy and alternately check at 51 Mc to be sure 
it's OK up there.  On a properly aligned radio with good driver and 
final tubes this is usually not difficult, and most radios will make at 
least 35 watts at 29.4 Mc.

73,

John K9WT

On 7/6/2026 1:49 PM, Ray Fantini via Milsurplus wrote:
> Wow man, it's amazing what you people know. Never knew any of this 
> about the loctal and now got to try that. Maybe because of the 
> difficulty in dealing with the sockets they never caught on?
> Between dealing with these weird tubes and now knowing what all those 
> countless boxes of crystal sets were for with the cryptic three-digit 
> numbers were used in I think I learned a lot from dealing with this 
> old 659. Waiting for parts to compleat repairs of the power supply and 
> hope to get this set up and running soon, had the receiver running 
> with substitute components for testing and it's not that bad going 
> full quieting at around 10 to 13 uV and useable down at around 3 uV 
> with a big fat IF passband but figuring if it had to work with things 
> like the BC-1000 (SCR-300) it has to be capable of about 30 kHz so 
> think netting with more modern sets like the PRC-25 or VRC-12 won't be 
> that big an issue. Finding a legal frequency may be more of a problem. 
> Think the VRC-12 stuff may go down to 29.6 as a Red Flag channel?  
> Will have to go out to the mutt and crank on the RT-524, maybe once I 
> get this all resolved can do a video of a BC-659 in a GPW having a QSO 
> with the VRC-12 in the mutt?
>
> Ray F/KA3EKH
>
>
>
> ------------------------------------------------------------------------
> *From:* milsurplus-bounces at mailman.qth.net 
> <milsurplus-bounces at mailman.qth.net> on behalf of sbjohnston--- via 
> Milsurplus <milsurplus at mailman.qth.net>
> *Sent:* Monday, July 6, 2026 12:06 PM
> *To:* milsurplus at mailman.qth.net <milsurplus at mailman.qth.net>
> *Subject:* Re: [Milsurplus] BC-659 Fun and Games
>
>
> Thanks John.  I have never before heard that there was a trick to 
> pulling loctal tubes out of their sockets.  I am eager to try it on my 
> next project involving loctal tubes.
>
> I got a 7C5 out of my loctal bin to look at the “bump”. Interesting - 
> I always thought those bumps were to aid in orientation when inserting 
> the tube (it marks the center post's key).
>
> When I am repairing/restoring equipment using loctals, I generally do 
> not pull any tubes unless they are suspect in some way.  If the stage 
> is performing as I expect, I leave them be out of concern I would 
> cause intermittents just by disturbing the pin-to-socket connections.  
> Now I have to worry about pulling with the right tilt, too.  Of 
> course, in the many past decades the owners might have repeatedly 
> pulled the tubes and loosened the sockets, so all bets are off really.
>
> My biggest gripe with loctals has been that some sockets have 
> excessively strong circular springs gripping the center post. Maybe 
> with the proper tilt that won't be the case.
>
> For those unfamiliar with the bump...  It is on the side of the metal 
> base (above the chassis line), as opposed to the bump on the end of 
> the center post that goes down into the socket.
>
> See the attached close up picture of the bump in question…
>
> image0.jpeg
>
>
>
>
>
> Steve WD8DAS
>
>
>
>
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