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I've recently purchased a Hallicrafters S-120 -- 4-tube superhet receiver from the 1960s, continuous tuning from 540 kHz to 30 MHz, bandspread control, and a regenerative IF that doubles as a BFO for SSB and CW reception. Someone before me appears to have worked on the set, as the capacitors seem good (no hum, good reception for the antenna currently available).

What I've learned since receiving it, however, is that this set lacks the selectivity, stability, and fineness of tuning to make a good communications receiver; that is, it's for listening, rather than the listening side of two-way operation. While I have tuned in CW, digital, and SSB transmissions, the latter especially are hard to really clean up. AM transmissions in any band come in very readily and clearly, assuming they're above the noise floor.

With a limited budget, however, I'm looking for a better receiver for use when I get on the air (likely mainly CW, as a CW transmitter can be had fairly cheaply). I need to be able to tune across a band to search for calls, hear the spot tone to set the transmitter, have support for muting when the tranmitter key is down (or the ability add it), and by preference, I'd like it to use vacuum tubes.

What do I need to look for (that can be identified from photos and eBay listings that usually are intended to hide the faults of a piece) to distinguish "listening" radios from "communication" receivers?

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    $\begingroup$ Does your S-120 have an IF output? $\endgroup$ – Marcus Müller Feb 6 '19 at 13:52
  • $\begingroup$ Not that I've seen. It appears to be completely stock (with the likely exception of the original selenium rectifier being replaced with a silicon version), the only unusual control is the "BFO" knob, which controls the IF regeneration. $\endgroup$ – Zeiss Ikon Feb 6 '19 at 14:25
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    $\begingroup$ Would an SDR be acceptable? I use a kiwiSDR for this; there are plenty of others also. $\endgroup$ – Chris K8NVH Feb 6 '19 at 16:49
  • $\begingroup$ A vacuum tube SDR would really be something... $\endgroup$ – Phil Frost - W8II Feb 6 '19 at 17:01
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    $\begingroup$ What is your "limited budget"? $\endgroup$ – Glenn W9IQ Feb 6 '19 at 22:08
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Since you plan to get licensed, I recommend that you purchase a transceiver, for two reasons.

  1. There is no "modern" transmitter to pair with a communications-grade receiver.
  2. A quick perusal of the classified ads reveals that, for similar receiver capability, the price of a receiver is not too different from the price of a transceiver.

The latest generation of ($$$!!) high-performance receivers appear to be "cut downs" of the same generation of transceiver. But, again, no mating transmitter is available.

If you still want to go the "separates" route, you will probably be relegated to the Drake "twins" or similar. Beware - the oscillators in these units may not be sufficiently stable to support digital modes beyond RTTY. If you want to operate FT8, for example, check with an expert to be sure you don't waste your time and treasure.

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  • $\begingroup$ At present, I have little to no interest in digital; I'm pointed mainly at CW and, to a lesser extent phone. I've been seeing what you point out, also, that transceivers cost the same as useful receivers, so I'm changing my search. $\endgroup$ – Zeiss Ikon Feb 10 '19 at 12:26
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When looking at legacy receivers, a key differentiator is often general coverage (shortwave) vs amateur radio coverage. Most shortwave receivers lack the band spread, selectivity, filtering and demodulation features needed for practical use as a receiver for a QSO. Receivers targeted primarily at the ham radio community tend to have better overall features for ham use.

The next major differentiator is the superheterodyne architecture that represents the epitome of legacy receiver architectures.

Having selectable filters such as 3000 and 300 hertz can help to cut adjacent QRM.

A notch filter can help to cut an offending signal or noise.

If you have a computer (even a Raspberry Pi 3) and are willing to invest $200, you can get a state of the art software defined receiver. An example of such a receiver is the Airspy HF+. It is an amazing piece of hardware for the price and will give superior performance to many heterodyne receivers. It even allows you to operate it over the Internet.

For slightly more money, you can purchase an SDR transceiver such as the HackRF One. This will eliminate the need for frequency spotting and transmit/receive relays or PIN diode switching that you would need to accommodate with a separate transmitter.

If you are not familiar with SDR receivers, there is a network of them on the Internet that are free to use.

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