The fact that it was the first fully transistorized communications receiver as early as 1965 adds to that reputation.
As mentioned in the discussion contained on the RADIO ROOM page, this particular radio and I go back at least 35 years when I was working at National Semiconductor, starting in 1969. I think this radio was purchased in the early 70's, even though its serial number indicates that it was manufactured in 1967.
The radio was part of the Linear Integrated Circuit Design department's test equipment. In some cases it was used to see if a device was transmitting on the frequency it was supposed to be on. In other cases it was used to make sure a device WAS NOT transmitting when it wasn't supposed to.
I used this radio as an oscillation detector when some IC test hardware I built oscillated and I could not find the source or the frequency because the capacitance from an oscilloscope or volt meter would KILL the oscillation. However, with this radio's sensitive front end you could just make a simple antenna probe and place it near the circuit in question and locate the source of oscillation. It might take a while to find it because of the wide tuning range of the radio. There are SIXTY bands of only 500 KHz each....so that is a lot of spinning of the knob to locate an unknown frequency.
A good writeup on this radio can be found here: http://www.io.com/~nielw/nat_list/hro500.htm
This is National's NC-125 Receiver. The blue knobs are obviously not original, but they do really stand out.
These receivers were built from 1950 - 1955 and this one has its matching speaker.
I just learned (4/3/11) that the speaker in this image is actually an NC-300TS which goes with the NC-300 receiver.
The following came from their marketing info:
"Now at last, you can get immediate delivery on the receiver that gives you more selectivity per dollar - the only receiver with the famed Select-O-Ject circuit built in ! And that's only one of the many fine features that make the NC-125 tops in receiver value ! Covers 550 kcs. - 36 mcs. in 4 bands. Voice, CW, NFM (with adapter). Edge lighted, direct-reading scale. Amateur, police, foreign, ship frequencies clearly marked. National Select-O-Ject built-in (rejects any selected audio frequency 45 db - boosts 38 db). Three microvolt sensitivity (for 10 db signal/noise ratio on 10-meter band). S-meter. AVC, ANL, ant. trimmer. Variable CW pitch control. Separate R.F. and audio gain controls. Volt. reg., stabilized oscillator. Jack for phono or NFM Adapter. Audio essentially flat to 10,000 c.p.s."
Now this National NC-300 is the epitome of a BOAT ANCHOR. It is big, bulky and heavy.
This receiver was made from 1955 - 1958
This is what National said about the receiver: National's famous "Dream Receiver." An extremely sensitive highly stable with exceptional calibration accuracy. Has eight electrical bands, 160 through 10 meters, plus a special 30-35 mc range used as a tunable IF for 6, 2, and 11\4 meters.
This radio was very well built and was very popular in its time.
I haven't done any checkout on this radio since I am missing the power supply and don't have other sources for all the required voltages at this time.
This is from National's marketing info:
Now from National - a brand-new Transceiver concept that brings you the three most popular amateur bands at a price equivalent to economy single-band units! No need to compromise on only one band - no need to spend a $300 to $800 premium for coverage of the two steadily deteriorating high frequency bands! The handsome, rugged, NCX-3 complements both your car and the ham shack and provides you with a solid 200 watts of SSB punch - plus - every feature National could think of for easy, relaxed ham band operation - vox or push to talk, CW break-in, SSB/CW AGC, S-meter - even a separate AM detector! The specifications really tell the story . . . study them carefully and see your National dealer as soon as possible. We're devoting additional production facilities to the NCX-3 to assure maximum delivery rate, and will start delivery December 30 - don't postpone your enjoyment of the new NCX-3 - get your advance order in now!
I was finally able to purchase a power supply for this rig and I am happy to say that the rig works very well!
Another real boat anchor and in a long line of HRO's is this National HRO-7.
This model was made in 1947-1949.
Here is National's marketing information:
Known and used by hams the world over for 13 years, the old HRO now has a new successor - the HRO-7 - incorporating every one of its strong points and adding a number of modern refinements. To begin with, the HRO-7 is housed in a streamlined gray cabinet which will enable you to meet the XYL's former objections to bringing your rig into the main part of the house. The whole family can listen when you pick up a French OP talking about the latest UN news. Two new miniature tubes have been added to further stabilize the receiver. This will enable you to turn the rig off and on again with an absolute minimum of retuning. As you turn the RF gain control, there'll be no appreciable change in the pitch of code signals and the HRO-7 remains unaffected by normal fluctuations in the voltage sent in by the power company.
The HRO-7 Radio Receiver is a twelve tube high-frequency superhetrodyne for the reception of code and phone signals throughout its frequency range of 50 to 430 Kcs., and 480 to 35,000 Kcs. Long an outstanding and proved performer in Communication and Amateur services, this new series of HRO-7 Receivers features many new refinements emanating from the latest advances in receiver circuitry and design. A new automatic, adjustable threshold, double action noise limiter effectively reduces interference caused by external noise pulses. Two new miniature type tubes, a 6C4 high-frequency oscillator and an OA2 voltage regulator, are employed to give a high order of oscillator stability. The addition of an Accessory Connector Socket, Tone Control, plus other electrical and mechanical revisions give this new HRO greater flexibility and adaptability. A 6 position crystal filter, maximum bandspreading of the Amateur bands, and an excellent signal-to-noise ratio continue to make the HRO a dependable Receiver, capable of maintaining communications despite the most adverse conditions.