National Receivers

National Company in Massachusetts was primarily known for the fine communications receivers it produced from the late 1920's through the 1960's. The SW-5 and SW-3 were extremely popular deluxe regenerative receivers using plug-in coils. The SW-3 actually lasted into the immediate post-WWII era, going through several versions mainly involving improved vacuum tubes.

sw3 1 sw3 2

I have one example of an early National superhet, the RHM, which was designed and built for the US Dept. of Commerce in 1932. It is still operating with its original capacitors, although it is time to upgrade some of the parts.


The "HRO" model first produced in 1934-35, was a marvelous receiver which underwent some electronic changes over the years, but maintained the same rugged hardware configuration that made it unique. It saw considerable use in WWII particularly for monitoring purposes in England. I saw an HRO displayed in the Pentagon a few years ago that was used by an Australian coast-watcher in the Pacific.

National kept up with the technology and the competition with Hallicrafters and Hammarlund until Asian manufacturing caught up with and undercut our economy.

This is the popular and long-lived HRO "Senior" developed in 1934, culminating in the HRO-60 produced in the late 1950's. The primary feature was the plug-in coil drawer with coil units for a myriad of receiving segments throughout the LF, MF, and HF ranges. A few folks even modified coil drawers for the 6 meter band.
My HRO is serial number 102-C which puts it circa 1938-1940. The tubes are still 2.5 volt filament types.
Like other collectible radios, HRO parts can bring a higher price than the radio itself, tempting sellers to "part out" a classic unit to make a larger profit.


The circa 1939 NC-44 pictured took almost a month of occasional work to restore. All the capacitors were replaced along with some of the wiring, two tube sockets, a wafer switch, and the broken glass cover for the dial. I purchased a glass cutter and breaking pliers thinking I would do my own glass work. After ending up with a wastebasket full of broken shards, I went to ACE Hardware where it took a guy 30 seconds to make me two nice dial covers. He didn't even charge me for it.
I also added an isolation transformer since this model of the NC-44 was an AC-DC transformerless model with a potentially hot chassis. Following alignment, the set performs quite well on shortwave with adequate audio quality. It even copies CW and SSB, although the stability isn't good enough for normal communications use.


This NC-156 from WWII was a specialty model made for the Navy and Coast Guard. There was a great fear that the enemy could monitor the local oscillator in un-shielded receivers to home in on a convoy for a torpedo attack, so National designed a non-radiating unit for ships. As it turned out, after the war, the Germans said that they had considered the possibility, but decided the radiated signal wouldn't be strong enough for practical detection anyway.
Jim Millen of National developed the innovative sliding coil assembly for the NC-100 series of receivers in the late 1930's.


The NC-173 was a post-WW II single conversion superhet that was chosen for the 1947 Kon-Tiki expedition. In that role, it ran on dry batteries for much of the voyage and survived a salt water dunking when the balsa raft ran aground on a reef adjacent to a Pacific atoll.

This NC-183 was the best general shortwave receiver produced by National just after WWII. It was a step up from the NC-173 and was about the ultimate in general coverage single-conversion superhets of the time.
This one was in terrible condition when received and a week was spent replacing all the capacitors and a few out-of-tolerance carbon resistors to bring it back to life. I had obtained a refinished case for it, so after cleaning it up, I installed the new cabinet and aligned the receiver. It still needs a couple of original knobs and new plastic frequency dials, but it sure looks a lot better now than it did when I got it.
National came out with an NC-183D shortly after which featured double conversion on the higher frequencies for better image rejection.


The SW-54 was a low-end receiver for the casual shortwave listener. It was a shortwave version of the "all-american five" AC-DC circuit that was popular into the 1950's. I never heard of anyone using it as an amateur receiver, but it couldn't have been any worse than the Hallicrafters S-38 that I started out with.


Here is an NC-88 from the 1950's. It was the low-end amateur radio offering and actually was useable, even on CW (provided you didn't operate on any band higher than the 40 meter band). It does a great job on shortwave broadcasting.


You may think that I goofed and uploaded the NC-88 twice, but this actually is the NC-98. It cost a little more than the NC-88 because of the added S-meter and crystal filter. Other than that, it suffers from the same mechanical instability as the former.


The NC-125 featured a built-in "Select-O-Ject" audio filter in an otherwise average single-conversion superhet. It still is a better performer than the NC-88/NC-98 models.


A blue receiver! No way! That's what I thought when I first saw one of these at AES in Milwaukee in the mid-1960's. All radios had to be black or grey.
Actually, the NC-270 was an inexpensive ham-band-only receiver with a complex ceramic filter setup that actually works pretty well. Coming out just prior to the SSB explosion, no pains were taken to make the AGC compatible with SSB and CW, so you have to ride the RF gain control to copy those modes. I'm sure modifications can easily be made to overcome this problem.
A missing bottom plate was recently acquired to make it complete.

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