Update: PA3GSV's Amazing Mighty Midget Receiver (video)

Jan sent me an amazing update on his Mate for the Mighty Midget Mk 2 receiver project.  I'm really blown away by the skill that he brings to the mechanical phase of this project.   This is a homebrew dial-string reduction drive using the end cap from a sewer pipe as the big wheel.  Think about that.  Amazing. Jan reports that with the mechanical work almost done, he is almost ready to start melting solder.  FB Jan!  Check out the video above and the photos below.

HRO (not HOR!) -- The King of Reduction Drives

At the recent Manassas Virginia hamfest Armand WA1UQO and I came across an old HRO receiver. Armand mentioned in passing that he had an HRO dial and drive for me if I wanted one.  When Pete heard this he said I definitely NEEDED one.  Armand heard Pete's comment and very kindly put an HRO dial and reduction drive in the mail for me.

Wow, it is a magnificent thing!  After years of struggling with small Jackson Brother reduction drives and with reduction drives brutally cannibalized out of innocent Heathkit Q multipliers, I now realize that I have been playing in the minor leagues.  This, my friends, is the reduction drive that helped win WWII!  I will have to build something worthy of its inclusion. 

The designation HRO has a wonderful story behind it: 

This is from: http://www.cryptomuseum.com/df/hro/

The new radio was also designed by James Millen at the National Radio Company, but this time with two RF amplifiers and two IF amplifiers at 455 kHz with a 20Hz crystal filter. He kept the pluggable coil packs as part of the design and added the now famous epicyclic dial, which allows the operator to tune the frequency scale in 1/500th units (with the aid of a calibration chart).

The design was finished in 1934 and National pushed hard to get the receiver out by the end of that year. When creating the tools for the first production run, the tool makers had to work overtime and used HOR (Hell Of a Rush) as a job number on their overtime slips. As National's marketing department didn't want their radios to become known as HORs (whores), the name was changed to HRO (Hell of a Rush Order). Despite the best engneering efforts, technical problems delayed the release of the the radio until March 1935. The price at the introduction was US$ 233.

Another site provides tech details and history on the drive itself:
https://www.prismnet.com/~nielw/PW_NPW_Dial/hro_dial.htm

The HRO dial introduced by the National Radio Company in late 1934 was the hallmark of top-of-the-line National receivers from the mid 30s through the 60s. By late 1936 the "HRO dial" was appearing on the NC-100 series of receivers and even the 1-10, National's VHF receiver. Throughout WWII many of the NC-100 variants that National provided to the military used this same dial. By 1950 National had added built-in direct frequency readout to the HRO-50 but still kept the same 0-500 reading dial. Through the mid-50s and into the 60s National mimiced the HRO dial look on their mid-priced receivers such as the NC300, 303 and 270. Even the solid state HRO-500 introduced in the early 60s used a version of this dial. When combined with the required 20 to 1 venier gear drive, the HRO dial provided an effective scale length of 12 feet and was direct reading to 1 part in 500. Ten turns of the dial drives the tuning capacitor stop to stop. Published HRO calibration curves showed each ham band spread over eight turns (or 400 divisions). In addition, dial divisions were about 1/4 inch apart. On all bands below 10 meters the HRO dial is easily resettable to within a KC (or KHz).

Occam's Bench: M0XPD on the Minimalist Measurement Mindset

Our ace correspondent in Dayton, Bob Crane W8SX, caught up with Paul Darlington M0XPD (above, the guy with the rifle) and interviewed him about his presentation at Four Days in May 2016.  You can listen to the interview here by clicking on the link below.   I especially liked the comments on the joys of fixing things and the advantages of SIMPLE analog circuitry. Listen to the end and you will learn about Paul Darlington's connection to the famous Darlington Pair.    

http://soldersmoke.com/M0XPDFDIM.mp3

Paul provided more info (including his slide show and presentation notes) on his BRILLIANT Dayton talk here:
https://sites.google.com/site/shacknasties/presentations/fdim-2016

You can  buy Paul's book here:
https://www.amazon.com/getting-there-Paul-Darlington/dp/1523452196

Thanks Paul!  Thanks Bob! And thanks to George Dobbs and William of Occam!

Narrow Band FM on 160 Meters? Using SSB phasing rigs?

On the G-QRP mailing list our British cousins are discussing the use of Narrow Band FM on Top Band.   160 meters has long been used for day-time local "chin wags" in the UK.   Noise, of course, is a factor to consider on 160.  FM would take care of the noise problem.

I was wondering if this would be legal in the USA. This is the kind of question that seems to provoke passionate, sometimes angry reactions.   I think the answer depends on the resulting bandwidth of the signal. 

There was an interesting discussion of this here:

http://www.eham.net/ehamforum/smf/index.php?action=printpage;topic=65481.0

Especially intriguing to me was Tom's comment about the link between Narrow Band FM and the early SSB phasing rigs.   I hadn't heard about that:

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Title: RE: Narrow Band FM is it legal below 30 MHZ.
Post by: N5EG on January 22, 2010, 11:10:43 AM

---

Hi Tim,

Yes - NBFM is legal. This is actually a hold over from long ago equipment. Back in the olden days phasing SSB exciters could also be adjusted to produce NBFM.

It's a little different than modern FM, in that the signal looks just like an AM signal, except the phase of one of the sidebands is 180 degrees reversed compared to the AM equivalent (doesn't matter which sideband). This gives an angle-modulated signal with +/- 45 degrees phase variation, but also 3 dB of amplitude variation.

While we don't normally like amplitude variation on an FM signal, it has the effect of preventing the generation of the higher order sidebands that true FM produces. A receiver than has a limiter stage doesn't care that much.

The result is that the old phasing exciters could produce this different kind of Narrow Band FM (probably the true meaning of NBFM long ago) that had the same channel width as AM, and a modulation index that's well below 1. Such a signal is compliant with current FCC regulations on HF bands.

-- Tom, N5EG

Great Video: The Secrets of Quantum Physics