Wednesday, September 5, 2018
The NC-81X sat in the National receiver price lineup below the NC-101XA. Comparing the two, the NC-81X had transformerless AC/DC power, no S-Meter and no RF stage but I found it really performs pretty good. Shifting the IF to 1560KC helped eliminate any image problem.
Along the way to adding it to my station lineup I did change a few things. First the obvious one, I changed out all of the paper and electrolytic caps. I left the original electrolytics in place but replaced them with modern electrolytics mounted under the chassis. I'm not a fan of transformerless AC/DC receivers and this one had a short between the chassis and the metal case. Unless run with an isolation transformer it was a shock hazard waiting to happen. I had a small isolation transformer big enough to handle the NC-81X B+ requirements so I wired it into the receiver to supply B+ and I left the filament string connected across 120 VAC. I addition I fused each side of the AC line and added a three wire/grounded cord. Now this radio is safe to use but repair work under the chassis still requires a "real" isolation transformer. The NC-81X is not an HRO though. While very usable it still tends to FM/wobble on strong CW signals. I suspect the B+ needs to be regulated.
The 1938 list price for the NC-81X was $165 while the NC-101X listed for $215. This was back when the US average wages per year was $1,730 compared to about $60,000 today. I bet 10% of my wages towards a new radio would lead to some interesting dinner time conversation. No wonder National introduced the NC-44 at an even lower price point ($82.50) and by 1939 dealers sold these radios at a very steep discount (NC-101X for $129 and NC-81X for $99).