A sample text widget

Etiam pulvinar consectetur dolor sed malesuada. Ut convallis euismod dolor nec pretium. Nunc ut tristique massa.

Nam sodales mi vitae dolor ullamcorper et vulputate enim accumsan. Morbi orci magna, tincidunt vitae molestie nec, molestie at mi. Nulla nulla lorem, suscipit in posuere in, interdum non magna.

Patents Can Produce Odd Bedfellows–The Precision ACE D1 Radio


I try to avoid writing strictly technical articles in this blog since it is aimed at those who only have a casual interest in technical history.  However, I recently obtained a little radio that is unusual enough that I wanted to provide some documentation for other collectors.

The radio is the Radio ACE Products Type D1 manufactured by The Precision Equipment Company of Cincinnati, Ohio in the early 1920s.  Its serial number is 127.

The ACE D1 came to me as a parts radio.  I was considering a different radio from a Craig’s List posting.  When I found that radio to be rather rough, the owner threw in the ACE to sweeten the deal.  I could tell that it was a rather early one-tube radio, but it was just about ruined.

Just a handful of years after it was new, a one-tube radio from the early 1920s had very little value.  This one apparently was given to a kid to play with.  He or she converted it to a crystal radio, removing the tuning coil and grid leak, then rewiring the tuning capacitor and variometer.  Numerous new holes were drilled into the Bakelite panel to hold a crystal stand, an audio transformer salvaged from a Radiola III (who knows why), and a few extra terminal posts.  The audio transformer was mounted on top of the tube socket, where the tube would have fit.  Most of the terminals were removed from the back panel.  Removal of the tuning coil eliminated the need for the tap switch.  This did not prevent our young friend from breaking off many of the tap contact points, replacing a couple with screws, then drilling more holes above each contact point for wiring that seems to have later been deemed unnecessary.  A replacement phone capacitor was installed in place of the original.  Vintage instructions for St. Joseph’s Aspirin were stuffed between one of the capacitor’s terminals and the ground plate on the front panel to prevent a short.  Three out of the four contacts for the tube socket were removed as well as some other hardware.  Then our young radio designer got even more creative.  To spice up the look of the set, the knobs, the delicately painted brass labels, the screws, and the front edges of the walnut case were painted silver.  One of the distinctive tuning knobs was broken as well.  All to say, it was pretty rough!

After looking into the Precision company a bit, I decided that this radio would be worth restoring to whatever degree I was able.  Precision was a small company that was not in business for very long.  There are not a lot of their radios out there to give clues as to how this one originally looked.  Little documentation is available either to guide in the replacement or reproduction of parts.  As of the time I am writing this, I haven’t found another ACE D1.  If you have one or anything close, I would love to hear from you.

Fortunately I was able to luck into some critical parts.  Just as importantly, Alan Douglas, author of the three volume RADIO MANUFACTURERS OF THE 1920’S graciously researched and identified parts in my radio using his extensive collection of radio literature.  Alan also sent me a copy of a catalog that provided specifications and dimensions of parts.

First, let’s talk about Precision.  The company would be largely forgotten if not for its most famous customer.  More about him shortly.  Most of the information I share here about Precision is from Alan Douglas’s books mentioned above as well as from Rusty McClure’s book CROSLEY, TWO BROTHERS AND A BUSINESS EMPIRE THAT TRANSFORMED THE NATION.


Precision made radios in Cincinnati, Ohio.  They were a small manufacturer. McClure describes Precision as a boutique radio shop that consisted of men working around tables of parts rather than the assembly lines that soon overtook the industry.  The company got on its feet in 1919 and used the recently glamorized name ACE as a trade name for their radios, in reference to World War I’s flying aces.

RADIO MANUFACTURERS OF THE 1920’S Used with Permission

Precision’s most important asset was acquired in 1920—a license to build regenerative radios.  Howard Armstrong patented the regenerative circuit in 1914.  In a day that a one tube radio was an expensive item, the regenerative circuit made the best use of that single tube.  Regenerative radios performed better than any other circuit of similar sophistication  and cost.  In 1920 Armstrong offered licenses to interested parties.  About twenty companies jumped on the offer.  Soon afterward Westinghouse bought Armstrong’s patent and froze the sell of licenses.  Westinghouse then joined RCA which aggressively protected its intellectual property, including the regeneration patent.  This put Precision and the other licensees in an enviable position.  They could not transfer their licenses to another company, but they could produce regenerative radios until RCA figured a way to scare them out of the business.

Now about that famous customer.  Powell Crosley was a Cincinnatian who did well for himself selling after-market car accessories.  In 1921 his son expressed an interest in joining the growing radio craze.  Since Precision was a local company, Powell and his son visited their showroom.  Upon learning that nothing in the showroom cost less than $130 (in a day that the average factory worker earned 61 cents an hour), Crosley stormed out with nothing but some parts and an instruction book for making a radio at home.  Crosley and his son built that radio, but more importantly Crosley decided that he could make a good profit manufacturing radios that cost considerably less than $130.  Crosley expanded into the radio business.  He soon realized that he was severely limited without access to a regeneration license—especially as the radio-buying public became more sophisticated.

By 1922 Precision was struggling.  They may have had a valuable license, but their small-shop method of building radios was not competing well with the radio factories popping up around the country.  Crosley heard about their troubles and quickly purchased Precision for access to the regeneration patent.  Of course, the patent was not transferable, but Crosley circumvented that problem by keeping Precision in business if only on paper.  The radios were made by Crosley’s factory with Crosley parts, but the name on the front was Precision and Precision’s trade name, ACE.


That same regeneration patent caused Precision to cross paths with The AC Electric Company which started making radio parts under the Dayton label about 1922 according to Alan Douglas in RADIO MANUFACTURERS OF THE 1920’S.  Precision seems to have occasionally used some Dayton parts–the two companies were only some fifty miles from each other.  Dayton also made radios.  Dayton had the same problem as Crosley–they could not legally build a regenerative radio.  That seems to have been the impetus for creating the D1.  Apparently Dayton commissioned Precision to make a regenerative radio using Dayton parts.  The radio was marketed in a Dayton catalog under Precision’s name and trade name, ACE.  I assume this was done to meet the conditions of the regeneration license.  Page 1 of RADIO MANUFACTURERS OF THE 1920’S includes a picture of what appears to be my ACE radio as featured in an un-dated Dayton catalog.

Used with permission

The placement of the phone jacks, tube observation hole, tap switch, and distinctive Dayton gear-like knobs are identical to my D1.  It is identified as the ACE Radio Phone Receiving Set.  One can even see Precision’s distinctively shaped brass nameplate on top of the radio, as well as the Armstrong license tag.  The catalog entry describes the vernier tuning condenser and vernier filament rheostat found in my D1, as well as its solid walnut cabinet.  The catalog also indicates that this radio uses tuned plate regeneration–typically requiring a tapped tuning coil and a variometer, rather than a tapped variocoupler coil with a tickler coil.


Dayton may not could make a regenerative radio, but they could certainly make other designs.  About the same time that the D1 was marketed, Dayton also offered the Dayton Phone Receiving Set which I will call the DPRS for short.

From Dayton’s Nov 1922 QST ad, reproduced from RADIO MANUFACTURERS OF THE 1920’S, used with permission

There are a number of photos of this radio on the internet that show it uses many of the same parts as my D1 (I have not been able to secure permission to reproduce those photos here, but they can easily be found with an internet search).  The DPRS uses the same tuning capacitor with its unusual vernier knob.  It also uses the same tapped tuning coil found in the Dayton catalog.  The tapped tuning coil uses an eight contact switch like my radio.  The DPRS has the same brass panel labels as the D1, as well as the distinctive Dayton knobs.

Beyond that, the radios are rather different.  The DPRS uses 1/4 inch phone jacks and front-mounted terminals for the electrical connections.

There is a much closer cousin to the D1: the Precision TRU which was marketed about the same time.

QST September 1922

Randy James sent me photos of his prize-winning TRU.  Unlike the D1, the TRU is constructed of Precision parts.  It also uses a tickler coil for regeneration, removing the need for a tuning coil with a separate variometer.  Because of the different location of the tapped coil, the tap switch falls at a different location on the panel.  The TRU doesn’t have the vernier tuner or vernier filament rheostat.  It also sports an engraved panel rather than the more primitive brass labels used on the D1.

Beyond those differences, the radios are strikingly alike.  From a quick glance, you would think they are the same radio.  The cabinets are identical (although the TRU has an indention in the lid to more easily accommodate the tube tip).  The layout of the panel is nearly the same and the same phone connectors are used.  Both radios use the same small panel in the back for all electrical connections other than the headphones.  Precision’s ACE nameplate is tacked to the top lid.  It would seem that the TRU and the D1 were manufactured by Precision about the same time.

Compare these photographs of Randy’s TRU to those of the D1 at the beginning of this article to see the similarities.

The TRU was reviewed in the December 1922 issue of Radio News.  I expect that the D1 was made about the same time.


It was a bit of a puzzle to figure out what parts should be used to replace those which had been removed.  Since this was a Precision radio with a lot of Dayton parts, it was not real clear when I started which remaining parts were original.  As I mentioned, Alan Douglas located and mailed to me a Dayton catalog of the period (yet different than the Dayton catalog featuring my radio).  From this I could determine which parts were appropriate.

The distinctive gear-shaped knobs are Dayton.  They are found in Dayton’s catalogs as well as on Dayton radios of the period such as the Dayton Phone Receiving Set.

The tuning condenser carries a Dayton label.  An inspection of the mounting holes in the panel indicate that it is original.  Some folks at the Antique Radio Forum shared my initial concern that the small knob at the bottom of the front panel seemed out of place until we found the photo of the radio in Alan’s Dayton catalog.  The catalog also showed the vernier plate controlled by that small knob.  Mine was missing the plate.  Having the catalog information allowed me to reproduce an appropriate plate.

The tuner with its mica insert

With the new vernier tuning plate

The variometer is also made by Dayton.  It does not carry a label, but is identical to those found in the Dayton catalog.  Its mounting also looked original to the panel.

The vernier rheostat with its concentric controls is also a Dayton part.

The tube socket was not made by Dayton.  It carries the ACE name and is identical to the sockets used in other Precision ACE radios.

Radio News December 1922

The socket is distinctive in that it uses a pot-metal shell attached to a Bakelite base.  A colorful feature of this socket is its markings.  Most Navy-standard tube sockets of the time had terminals labeled +, -, G, and P for the two filament connections, the Grid, and the Plate.  This socket is marked +, -, G, and W, using De Forest’s obsolete designation of the Plate as the Wing.

Alan Douglas told me in an Antique Radio Forum post that the owners of Precision were amateur operators from the days when a ham’s most precious possession might be a De Forest Audion.  They may have used the obsolete term as a salute to their past.

Again, the mounting holes for the socket also indicate that it is original to the radio.

A big hole in my plans for restoration was determining what the missing tuning coil looked like.  Since the radio has a tap switch, I knew it had a tuning coil of some type which was removed by our enthusiastic, young radio engineer.  Alan’s Dayton catalog came to the rescue in a big way.  Dayton made an accessory tapped coil for their tuning capacitors.  The coil came with mounts to connect it to studs on the capacitor.  The catalog fortunately specified the coil’s length, diameter, wire size, and number of turns.

I was able to locate an orphaned 1920s coil of the same diameter, although the length and wire size were off.  I unwound the coil and cut the form to the correct length.  I sanded off the old varnish with its shadow of the original wiring.  I re-varnished the form and rewound it with 1920s double silk magnet wire of an appropriate size.

Nickel plated hardware from another parts radio was used to fabricate mounts for the coil.  Dayton’s non-regenerative Phone Receiving Set used this same combination of tuning coil and vernier tuner.  There are a few low resolution color photos of these sets on the internet that helped me identify the appropriate color for the coil form and windings.

The only components I had to guess at were the grid leak and the phone condensers.  Most of the components of my D1 were made by Dayton.  The tube socket was made by Precision.  Precision advertisements for that socket said it could be provided with a grid leak as an accessory.  So did Precision use their own grid leak with their socket, or did they use a Dayton grid leak?  Without finding another D1 I don’t know that I could answer that question.  I found no suggestions from the Antique Radio Forum community.  The Dayton catalog gave me photos and specifications for Dayton’s grid leak and phone capacitors.  The photos of Dayton Phone Receiving Sets on the internet showed how the grid leak authentically attached to the tube socket in the Dayton radio and also provided the color of the paper used in the capacitor’s outer wrapping.  I decided to reproduce the Dayton products.


With most of the original wiring gone, I needed a schematic.  Granted, it is not hard to guess such a simple circuit, but I wanted to be as authentic as possible.  I used three credible sources.  The first was the Dayton Phone Receiving Set.  The Farmer’s Old Radio Notebook website includes a schematic of a Dayton Phone Receiving Set found inside an actual set.  http://www.gifarmer.com/radio/battery/dayton.shtml

As mentioned above, this radio shares Dayton’s tuning capacitor–coil combination with my set.  In the Dayton set the two are in series with the antenna connected to the capacitor and the ground to the bottom end of the coil.  The grid leak connects to the point between the two.  My second source is Alan’s Dayton catalog which includes the parts found in my D1.  Although Dayton couldn’t build a regenerative set, there was no law forbidding them from publishing a schematic for hobbyists who would want to construct one from Dayton parts.  The catalog includes a circuit that, I expect, is pretty much identical to my D1.  It uses a variometer for plate-tuning regeneration.

The 1923 paperback 100 RADIO HOOKUPS includes schematics for just about any circuit used up until that time.  One of their circuits for a plate-tuned regenerative receiver was a close variant to the Dayton schematic.


Gary at Playthings of the Past was able to locate a replacement for my broken Dayton knob, as well as new old stock tap switch contacts, appropriate screw terminals, and the aforementioned coil form.

Three of the four tube socket contacts were missing.  I used nickel plated brass to fabricate replacements.  I collected nickel plated screws and nuts from my junk box to replace missing hardware as needed.

The one original contact with a new one, before it is bent and the locating pin is cut to length.

I was not confident that I could remove the silver paint from the panel labels.  I carefully masked them off and gently sanded the paint with 0000 steel wool.  Fortunately I was able to remove the silver paint while retaining the original black lettering.  I then buffed and lacquered the brass plates and tacks.

The silver paint easily loosened from the Bakelite panel as I polished it with Brasso.  I filled the extra holes with dark epoxy that I later painted black.  I also filled the tube observation holes that had been enlarged.  I then re-drilled them to the proper size.

The tube socket, tuning capacitor, and variometer cleaned up easily, and the walnut cabinet came back to life (the joy of real hardwoods).

As described above, I used the photos and specifications in the Dayton catalog to create new grid leak and phone capacitors.  The pictures on the internet of Dayton Phone Receiving Sets indicated the color of the capacitors and also showed the fiberboard grid leak cantilevered from the tube socket screw terminal.  That provided guidance for my installation.  As described in the Dayton catalog, I used brass foil.  At least that is what you see.  Yes, I cheated and mounted a modern capacitor and grid leak resistor in the hollowed out center of the fiberboard.  Waxed paper and brass foil formed the edges, covered by light brown cardstock printed with a cleaned up JPG lifted from the catalog photo.

I then wired the set using new-old-stock wiring lugs.


So, how does the D1 perform?  Few one tube sets will impress your socks off although Dayton indicated you could expect a 1000 mile range from the radio.  I tuned around local stations using a UX200 detector tube.  The radio didn’t seem to do as well as some other one tube sets I have.  Most of them use a tickler coil for regeneration rather than plate regeneration with a variometer.  I’m not sure if that makes a difference.  Well, I didn’t fix up this radio to listen to.

The Precision ACE D1 was created to bring a regenerative radio to market while complying with a well defended patent.  It is not clear that the venture was a commercial success for Dayton.  While there are many Dayton sets out there, there don’t seem to be many D1 radios.  Of course Crosley bought Precision the same year that the D1 appeared.  I expect he didn’t see any point in building radios for a competitor using parts that didn’t come from his factory.  If the D1 was still being made at the time of the Crosley buy-out, production would have quickly been terminated, as it was for all other existing Precision models.  The new Precision ACE models were made at the Crosley factory using Crosley parts.

If you have any information about the D1 or similar radios, please contact me.

1 comment to Patents Can Produce Odd Bedfellows–The Precision ACE D1 Radio