There's a 1939 radio manual in the online library - http://hetclub.org/burr/lithomepage.htm . Click on Manuals in the 1930-1939 File. Then look for 1933-1941 Hudson Radio Manuals. There is a diagram for the antenna on page 64. I apologize for the quality of the scan - the original was a very poor copy - but you should be able to figure it out.

Hudsonly,
Alex Burr
Memphis, TN

These are common to late thirties Hudsons. Usually they consist of two steel brackets that fasten to the underside of the runningboards, and stranded cable that runs back and forth between holes in each of the brackets, for a total length of maybe 16 to 20 feet per runningboard. The cables connect to one another and then to the antenna lead that runs to the receiver unit under the dashboard.

The radio section of the shop manual will have a crude drawing of this, but in order to replicate one, I recommend that you contact a number of 1939 owners and ask if any of them have the under the runningboard antenna. If one lives within driving range of you, you could go to his house, take photos and measurements. The brackets are simple affairs made of welded strap metal. I used S hooks and porcelain wire insulators as a means to loop the cable back and forth (without grounding on the brackets). Frankly, they under-runningboard antenna never worked very well for me, though it might have been the receiver that was at fault.

I was going to do the same thing untill i did some (lots) of research. The factory install under the running board was terrible reception. Dealers knew they would see the car again to install a cowl mount antenna. If you want a functional radio find a period antenna. Here is what mine looks like.
http://hudsonterraplane.com/Terraplane/2006/2006.htm

Gregg
www.HudsonTerraplane.com

If you do decide to do it as original: Black rubber insulated spark plug wire is just like what Hudson used for the antenna. My '36 still had some scraps of the original antenna, and that's what it looked like. Email me for a photo of the installation. pwald@comporium.net.

Thanks everybody. I had a cowl mounted antenna on this car but it didn't look right for the period. After seeing some of the under running board stuff, it looks pretty bad. I think I will look for a more period correct cowl antenna before I decide. Thanks for the responses.

I was told that the under running board antenna was brought about by the overhead streetcar wires in the big cities. So much static your radio would be almost useless. But then FM solved that problem.. or was it the invention of the smelly diesel bus?

Technically the proper antenna length for an AM radio is about 75 feet. In the early days (prior to the late thirties) many different schemes were tried to develop a modest size antenna that the radio's antenna circuit would "think" was much longer. Until this development could be achieved, it was "the longer the better." Manufacturer of the radios Hudson used (Zenith?) took the approach of laying out a very long antenna that would run back and forth under the running board(s). (The top of the line radios got the "both running boards" treatment, while the lower line of radios got one only under the left side). Finally, in the late thirties, it was discovered how to get the electronics to accept an antenna length of 3 to 5 feet, and the "modern" telescoping antenna resulted. The optimum antenna length for FM is about 28 inches, so the arrival of FM permitted the shorter non-telescoping antennas.

My 35 Terraplane has the running board antenna under both running boards. The rubber is pretty roached but the radio still works. It takes quite awhile for the tubes to warm up however. It looks like folks that know a heck of alot more than I do about these cars have already answered your question but I thought I would send a photo or two of what my antenna looks like for reference.

photo #912 shows an area under the dash directly above the radio that looks like it should be a light of some kind. Does yours have something like it? I don't know what else it would be for.

Mike - Thanks for your work to show me your under the running board antenna. Based upon the info I have learned, I think I will try to get a period correct cowl antenna. My radio doesn't look anything like yours. I would venture a guess that what you are referring to is supposed to be a little light to show the radio is on. It is perhaps burnt out on your radio. Thanks for your help. MS 🙂

If anyone's interested, Jerry Vinarcik in Seven Hills, Oh. makes a very nice repop of the running board antennas. Ain't cheap but his stuff fits and works! He operates as Yesterday's Radio and makes a lot of parts for Packards. Don't have his phone number handy right now but should be available from information.

MIKE I HAVE A FEW OF THE ONES LIKE ON THE CAR IN THE PHOTOS POSTED ON HERE BY GREGG MARONEY IT IS NEW STILL IN THE PACKAGE $25 + SHIPPING LET ME KNOW

Paul,

I sent you a PM. I would be interested if you have the rubber parts for my car.

Thanks,

Mike