HRO-W Comments - Barry Williams

HRO-W Comments

by Barry Williams, KD5VC

copyright 2006 Barry Williams

The primary differences between the HRO-5T and HRO-W are the S-Meter and the "Tropical Anti Fungal" coating. There should be a tag in the upper left corner stating that it is "R106 Mk III". These were ordered by the British for use in the Pacific war, when they thought the war might last into 1946. Many of them were never shipped, I have not seen one in England, and none of my friends there recall any of them. So it appears that the ones they did receive either stayed in India, Malaya, and perhaps Singapore, or were dumped. My friends in Australia have also not seen any. National sold some of them direct to the public as HRO-W. They then converted some to HRO-5TA1. You can tell those because the tag is on the left side, where they removed the R106 tag. In some cases they just left the four little holes on the right where the contract information was originally located. When you look inside one of these you will see a small chassis mounted on top of the receiver chassis with the noise limiter. I have seen a few with correct front panels built on the W chassis using this same mounting of the limiter, and even one 1st model HRO that was rebuilt by the factory into a 5TA1 with the same little chassis.

I have only seen one 697-W power supply, they were built very much better than the doghouse supply, the filter cap actually plugs in. Concerning the coils, National would do about anything to build a product, but the two HRO-Ws that I have came with the "Silver Front" coils like on the HRO-5TA1 except without the band spread capability. These were marked JA, JB, JC, JD, JE, and F. These match the serials on the receivers. The frames and charts were used in the HRO-M and MR series. Check and see if there is a serial stamped on the coil set and if it matches the receiver.

The British used a 0-1 ma meter rather than an S-Meter. I also noticed that the two Ws I have seem to have more gain than the 5TA1s. With a moderate antenna they would overload on the local AM broadcast stations with the meter pegged. It is possible that they were set to a specific gain in order to be able to compare meter readings and determine roughly where the transmitter was located with reference to the stations. A reading of .27 mils versus S2 plus 1/8" would probably be preferred.

Bill Fizette at the AWA wrote an article about the HRO-W some time back, he thought they were quite rare as that one was the first he had seen. I was able to get two sets.

Also the fungicide was supposed to be installed on the receiver without the knobs and with some internal masking. One of mine had fungicide on the knobs, giving them a gold tint, I have been asked a couple of times if I had the knobs gold plated.

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