National NC-81X

I've gotten my NC-81X back on the air! It is paired with my Stancor 10P for a mid-class 1939 AM/CW station. I'm using it on 40 and 80 meter CW.

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).

AWA 1929 CW Party

With snow on the picnic tables here in Minnesota my operating has moved from K1/QRP to the boat anchors in the basement. The AWA 1929 CW Party occurred the first two weekends of December. This contest requires that the transmitters reflect 1929 or older technology and tubes. Participation is in the 50 - 100 station range so it is a fairly low key "contest". Even the required log information forces operators to slow down as name, QTH, signal report and transmitter descriptions are exchanged. Power is limited to 10 watts input (except for late east-west QSOs) on 80 and 40 meters. Many of the transmitters are self excited Hartley, TNT or TPTG oscillators link coupled to the antenna. Some are MOPA (master oscillator-power amplifier) two stage transmitters. I put my TNT transmitter on the air with my National NC-81X receiver. Running about 2 watts out on 3560 KHz I had seven enjoyable QSOs. Longest "DX" was N4GJV in Cleveland, NC. All of the others were in MN and WI. The contest was not without some last minute challenges, but not with the 1929 gear. As I got started I realized that I had no way to zero beat my signal. The '81X muting function has no mute bypass switch. With it wired into my T-R relay to mute on transmit I had no way to tune my receiver to listen for my own frequency. Fortunately the '81X is ham band only with relatively good calibration so I wasn't to far off ... but then the NC-81X receiver dial string broke. My receiver could be tuned just fine but I had no direct frequency readout. I made it through the contest by listening for a signal of known frequency and then not straying far from that. It was a fun evening.