[David Dunlop]

Thanks for the input on wire lengths, Chis. Much appreciated.

My apologies if rumours of the death of either myself, or this project, had begun to circulate. Neither is true.

I have been sidetracked during the three sets of resistance tests I needed to complete on the 52-Set Sender. The main cause was some very odd readings I was getting. The initial assumption was a serious fault, or faults, lurking somewhere in the Sender, but as I pondered all the data; a more likely suspect for the high readings began to be my Digital Multimeter. It has performed very well whenever I needed to test a more modern, solid-state piece of electronics and never gave its reliability much thought. I began to have second thoughts when so many Sender tests started showing up where the DMM sampling rate simply would not stabilize, and would start a massive sweeping action, either in Full Auto Resistance Mode, or a narrower manual resistance range. In Auto, it invariably ended up reading at Infinity and stop working.

15 or so odd results showed up in the final data collection and I was suspicious enough to pull out my RCA VoltOhmyst VTVM (actually the recommended VTVM in the Canadian Army Test Instructions for the Wireless Set No. 19 and the 52-Set) and randomly sampled three of the odd tests. All three came back higher than I would have liked, but not even close to the ‘Infinity’ values the DMM was giving me.

So I started redoing the testing with the RCA Analog Meter for all the really odd values and from time to time rechecked a few of the tests that came back OK on the DMM. All was going well for a while and then the good test results started going off. A quick check of a couple of known resistance standards showed those results were now out and panic set in. After about a week, it dawned on me I had been watching the RCA Analog Meter warm up and was checking the Zero status of the needle in voltage mode while the meter warmed up, but had forgotten to also Zero the needle for Ohms. So I tried that and could not get it to Zero to save my Soul. I had put a brand new pair of D-Cells in the VTVM in January, so they were not on my radar, but should have been. When I finally realized they were worth a look, one tested 1.34 Volts and the other came in at 0.32 Volts. Popped a brand new set in and problem solved.

In the meantime, checking my two digital multimeters showed both were quite accurate and the RCA gave me results that were so close to correct resistance values I was a happy camper. However, my only backup analog multimeter, a cheap modern one about 15 years old, was consistently 25% off values for resistance, It’s manual claimed +/= 5% when new. So I was short a reliable analog backup.

I have now found a very nice, very accurate Simpson Model 303 VTVM, and being a give away, I am a happy camper and can now get these tests finished on the Sender.

David