RAN Technology

The Multi Elmac A54-H project

Vintage Ham Radio 0 Comments 01/13/2022 

A tribute to Gus Undy W8YNC

Posted By: Robert Nickels (ranickels)

Elmac aka Multi-Elmac was actually the Multi-Products company after tube maker Eimac complained that their original name was too confusing.  Most hams just call them Elmacs anyhow!

The company was started by Cletus Collum in 1947 to commercialize his design of a radio-controlled opener for garage doors and gates.  That product still lives on through the Stanley Company and it's successors.  Of course the ham product lines ended with the end of the AM era, even though the company was a fairly significant maker of early CB radios in the 1960s.

It's worth taking a moment to remember the designer of the first "Mighty Elmac", the A-54 transmitter, in 1952.  Rather than summarize his life, here's a snippet from his 2013 obituary that does a nice job of it:

"Gus was a man of his times. Born in Hungary in 1920 shortly after the Spanish flu
epidemic, he immigrated to the U.S. with his family as a toddler and spent his 3rd
birthday at Ellis Island. He spent his young childhood on a Pennsylvania farm during
the great depression, and was in Detroit, Michigan during his high school years. It was
there that he was able to begin indulging his fascination with radios and electronics. He
graduated from Cass Technical High School in Detroit in 1939 and went on to work
at Weltronic during the war years. During WWII, his work at Weltronic was deemed
necessary to the war effort and kept him out of the armed services and traveling the
country trouble-shooting problems with welding controls. It was at Weltronic that he
met the love of his life, a “wonderful girl”, Thelma McKeon. They married in 1942.
He became a U.S. citizen at the age of 25. When his deferment ended in 1945, he was
drafted into the U.S. Army where he served with honor at Fort Sheridan, Illinois.

Gus's independent and creative attitude shaped his life. Returning from the service, he
built a radio control for his garage door opener. This became the prototype that launched
his own company, Multi-Elmac, where he spent the rest of his working career. In 1950
Gus built the house he and Thelma raised their children in. He was active in the Detroit
Knights of Columbus. He was a ham radio operator (W8YNC)."  Gus became SK at age 93.



Elmac was a small company and one neat bit of ham history can be seen below - Gus's initials in the title block of the A54-H schematic...which he drew himself!

The A54 came in two flavors:  the plain A54 had a 6C4 speech amplifier wired for a carbon mic, which was probably the better choice due to the inherent "punch" the carbon mic gave to a low power AM signal.  But most hams preferred the A54-H which swapped the 6C4 for a 6AU6 pentode for extra gain to drive the modulator with a high impedance crystal or dynamic mike.    Many hams did the conversion themselves, and in the case of mine, stopped about halfway through.   My A54 was not fully "H-ifiied" as while the 6AU6 speech amp was present the modulator output was still wired the original way.   As the schematic shows, the "H" model used the second set of contacts on the PA on/off switch to short the secondary of the modulation transformer when the PA was off.  That seems like a really good idea since the modulator remains fully powered up when spotting with the PA off, and high voltage transients caused by inadvertent mic pickup could have easily damaged the mod transformer.

I completed the modification and made other changes and updates.  A previous owner had replaced most of the old electrolytic capacitors but made a few errors in the process.  No one had ever added a mic gain pot on the input of the speech amp, without which it would go in to extreme audio oscillations.     The official method evidently was to drill a hole in the panel cover and add the gain pot there, I just went with a small trimpot under the chassis, figuring it would be a set-and-forget adjustment as long as I didn't switch mics too much.

Speaking of vintage mics, I found a Shure 55S had a problem, click here for my simple fix.

The design is very straightforward.  Two separate oscillators are used for crystal or VFO control and the switch selects between them.  The buffer is broadband enough that tuning is not critical to obtain sufficient drive for the 807 final and no one every went wrong with a pair of 6L6s as a modulator!    The fact that many A54s can be heard on the air is tribute to Gus's conservative design and selection of quality components.

After the conversion was complete and the A54-H was producing 20-25 watts output with good modulation I decided it would make it's debut on the Mighty Elmac net where it was given a 20-over-9 signal report from net control WA6GYC in Troy MI, 330 miles away.  Not bad for a low-power AM rig from the 1950s!

The companion receiver for the A54 was the PMR-6 and I've used them but the selectivity is broader than desirable for a crowded band so I opted for the Pierson-Holt KE-93 instead.   These are true communications receivers in a very compact package and having the power supply/speaker accessory make it easy to use on AC power.    

One of my VERSA-TR RF-actuated antenna relays was used to simplify operation.   Since the Elmac PSA-500 has a set of normally-closed switch contact I'm using them for speaker muting, although the VERSA-TR can do this as well.   I may change that around if/when I reconfigure the A54-H to drive an amplifier.  And since there's no PTT relay I rewired the mic jack to have audio on the tip rather than ring contact so I can use vintage mics with a 2-circuit plug.  

It ain't "heavy metal" but it makes for  a pretty snazzy-looking set up I think!

Click on the image title or on the image itself to open the full-sized image in a separate window.


The Pioneer 530

made by JAARS for Wycliffe Bible Translators
Category: Vintage Ham Radio
In 1917 a missionary named William Cameron Townsend went to Guatemala to sell Spanish Bibles. But he was shocked when many people couldn’t understand the books. They spoke Cakchiquel, a language without a Bible.   He believed everyone should understand the Bible, so he started a linguistics school (the Summer Institute of Linguistics, known today as SIL) that trained people to do Bible ...  READ MORE
- Robert Nickels (ranickels),  07/02/2022 
    Visitors to the Elgin National Historic area along the Fox River in Elgin Illinois may not realize they are at the site of a famous shortwave radio station - W9XAM - the time signal station operated by the Elgin Watch Company.Elgin was the only watch company maintaining an observatory that observed, recorded and broadcasted time from the stars correct to the hundredths of a second. Located a...  READ MORE
- Robert Nickels (ranickels),  05/09/2022 

The Mosley Commando II

Made in England and scarce even there
Category: Vintage Ham Radio
The Mosley CM-1 receiver is quite well known and not especially hard to find in the US even though it was the only radio produced by the company that has been well-known for antennas since 1939.   Or is it...?A full-page ad (advert for you on the other side of the pond) appeared in the RSGB Bulletin in 1963 for a nice looking and very capable SSB transmitter called the "Commando II&...  READ MORE
- Robert Nickels (ranickels),  04/15/2022 
   I'm not ready to publish a description of exactly HOW it works, but 20 minutes effort with scissors and tape produced a prototype  Droplet Energy Generator that allows me to say for sure that IT WORKS!I duplicated the design shown in this video.   I wrapped a scrap of plastic in aluminum foil, then applied a strip of double-sided tape and to that attached a piece of PTFE thread-...  READ MORE
- Robert Nickels (ranickels),  03/30/2022 
   When I was first licensed in the 1960s in Nebraska, two groups of hams were commonly heard on the air before those with jobs got off work - other teens like me and the disabled hams.   Some of my earliest Novice ham buddies were blind students at the Nebraska School for the Blind in Nebraska City, and there were many other visually-impaired hams, all of whom were exceptional operators, e...  READ MORE
- Robert Nickels (ranickels),  03/21/2022 
   Old style mica capacitors were used in the pi-net matching sections of several vintage transmitters and the combination of age, heat, and high RF currents have made them likely failure items.   My Collins 32V-2 transmitter was to the point where it would not properly load to full power on 75 meters so something had to be done.   Mica capacitors are no longer made but fortunately new...  READ MORE
- Robert Nickels (ranickels),  03/19/2022 
   I found myself wanting to convert various frequencies to other frequencies and wanted a cheap and easy solution, so I designed a simple "universal converter" using the NE-602 and a programmable oscillator from Epson.  I'd used the same combination in hundreds of "RANVerter" SDR Upconverter projects since my Dec. 2013 QST article and knew that while there were limitatio...  READ MORE
- Robert Nickels (ranickels),  03/17/2022 
   It's always a challenge to hold PC boards during assemly and testing.  After purchasing a magnetic holder from Amazon  I realized I wanted more and could easily make as many as I wanted using inexpensive 3 mm hardware from eBay and some strong "fridge magnets".     All that's needed is to epoxy a standoff to the magnet - both tapped and threaded ...  READ MORE
- Robert Nickels (ranickels),  03/09/2022 
   The Si5351 has been the biggest boon to homebrewers since the invention of the NE-602, especially now that quartz crystals are essentially obsolete.   But it's redundant to run the output of the 5351 through a johnson counter to develop the quadrature signals required for QSD/QSE SDR front-ends when there are three clock outputs available and the IC allows for phase offsets. &nb...  READ MORE
- Robert Nickels (ranickels),  03/09/2022 
   It's pretty well accepted that the Pacemaker was not EF Johnson's finest effort.   In fact it was the first of several failed attempts by the King of the AM Transmitters to make the transition to SSB.    In the end, it was the rise of CB popularity that kept the company viable, along with its component business, while their ham business gradually faced away. &...  READ MORE
- Robert Nickels (ranickels),  03/03/2022 

VIEW News Item

Announcing the W9DYV Radio Society

honoring SSB pioneer Wes Schum W9DYV
VIEW News Item

Hamfests Return!

A quick look at the Wauseon OH swap on June 6, 2020
VIEW News Item

Making A Transistor Radio

in memory of Rev. George Dobbs G3RJV (SK)
VIEW News Item

Wes Schum, Amateur Radio's Unsung Hero

new book released, available on Amazon
VIEW News Item

Soviet Spy Radio found in forest

(oh yeah, I put that there...I'll take it now thanks!)

(There are currently no Blogs.)