{"id":50861,"date":"2021-11-14T09:47:14","date_gmt":"2021-11-14T13:47:14","guid":{"rendered":"https:\/\/swling.com\/blog\/?p=50861"},"modified":"2021-11-14T09:47:14","modified_gmt":"2021-11-14T13:47:14","slug":"guest-post-remembering-the-radio-shack-trfs","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2021\/11\/guest-post-remembering-the-radio-shack-trfs\/","title":{"rendered":"Guest Post: Remembering the Radio Shack TRFs"},"content":{"rendered":"

Many thanks to\u00a0SWLing Post<\/em>\u00a0contributor,\u00a0Bob Colegrove<\/a>, for the following guest post:<\/strong><\/p>\n

\n

Remembering the Radio Shack TRFs<\/b><\/h1>\n

As recalled by Bob Colegrove<\/strong><\/p>\n

\"\"<\/a><\/p>\n

There has always been an interest in DXing on the cheap.\u00a0 At the same time, most of us don\u2019t want to sacrifice any more capability than necessary.\u00a0 In the late 1970s and the early 1980s, Radio Shack provided an attractive answer to this conundrum for medium wave DXers.\u00a0 These were identified respectively by their Radio Shack stock numbers 12-655 and subsequently the 12-656A.\u00a0 I remember them being very popular among National Radio Club members of the time.<\/p>\n

These radios were commonly known by their sobriquet \u201cTRF.\u201d\u00a0 Initially applied by Radio Shack itself, the term stuck.\u00a0 TRF stands for tuned radio frequency<\/i> receiver.\u00a0 In the early days of radio, the term referred to the necessity for the operator to manually put an RF amplifier stage on frequency by adjusting the value of a variable capacitor or inductor.\u00a0 As amplifier stages became cascaded in two or three stages, this became a real problem, as each stage had to produce the correct frequency before anything could be heard.\u00a0 Eventually, designers hit on the idea of mechanically connecting all the RF stages together so tuning could be accomplished with a single knob.<\/p>\n

Fast forward to the standard AM radios of a later generation.\u00a0 Entry level (read cheap<\/i>) radios were limited to two stages consisting of a converter and an oscillator.\u00a0 This was standard design practice during the vacuum tube and transistor eras.\u00a0 Better, more sensitive radios added a third stage, an RF amplifier operating ahead of the converter stage.\u00a0 Obviously, this required more circuitry and, consequently, more expense.<\/p>\n

Enter the Radio Shack TRFs.\u00a0 The term TRF was a throwback to the days of the tuned radio frequency radios and referred specifically to Radio Shack\u2019s addition of an extra RF amplifier ahead of the converter stage.\u00a0 The TRFs were by no means the first radios to have this feature, but they were obviously marketed to folks who wanted longer than normal distance reception.\u00a0 Further, the radios were AM only uncompromised by FM circuitry, which would have to be integrated into the design and provide a distraction at best and a performance compromise at worst.<\/p>\n

I didn\u2019t discover these treasures until late in their production cycle.\u00a0 Consequently, my comments are mostly focused on the 12-656A.\u00a0 In later times, the -656A retailed for $34.95.\u00a0 On final clearance this dropped to $25, and I snapped up several for my friends and my own tinkering.\u00a0 The internal layout was not especially good for repair or modification, but at least was well within this enthusiast\u2019s capability.<\/p>\n

\"\"<\/a><\/p>\n

The picture below shows the dial of the -656A.\u00a0 The radio was designed prior to the expansion of the AM broadcast band to 1700 kHz; thus, it is only specified to cover 520 kHz through 1620 kHz.\u00a0 Although I don\u2019t recall ever having tried it, the circuitry could possibly be coaxed to 1700 kHz.\u00a0 On one of my \u201chot rod\u201d units, I replaced the silk-screened dial with a plain piece of Plexiglas backed with a hand-calibrated dial, which permitted accurate calibrations for 10-kHz channel identification.\u00a0 The tuning knob and dial cord mechanism work very well right out of the box.<\/p>\n

\"\"<\/a><\/b><\/p>\n

The controls are aligned along the right front side of the radio.\u00a0 Below the tuning knob are tone and volume controls followed by an off\/on switch.\u00a0 The 655 is similar, except the tone switch is replaced by a slider potentiometer like the volume control.\u00a0 In retrospect, the off\/on switch should have been recessed into the front panel, as it is easy to accidentally turn on the radio with the protrusion of the switch.<\/p>\n

\"\"<\/a><\/p>\n

The back of the cabinet (below) features standard 1\/8\u201d phone jacks for earphones (left) and an external antenna (right).\u00a0 The TRFs may be powered by either four C cells or from 115-Vac mains.\u00a0 Rather than having a separate 6-Vdc wall wart, the ac power supply components, cord and all, are contained inside the radio.\u00a0 For storage, the power cord is simply wrapped up in its own compartment next to the battery compartment.<\/p>\n

\"\"<\/a><\/p>\n

Below is a tinker\u2019s view of the innards of a -656A.\u00a0 Could the box have been made smaller?\u00a0 Obviously, one could replace the internal ac power components with a wall wart.\u00a0 Perhaps the C batteries could be replaced with AAs.\u00a0 Problem is with the speaker.\u00a0 The PC board hides a large drum for the tuning mechanism.\u00a0 Given the smooth tuning and large dial, the tuning arrangement is not something I would compromise.\u00a0 So, stacking the speaker with the PC board would require a much thicker box.<\/p>\n

The external antenna uses the standard approach of a small transfer coil wrapped around the ferrite bar for signal transfer.\u00a0 Just as an aside, keep in mind for any long- or medium-wave radio having an external antenna coupled to the internal ferrite bar, the ferrite bar will remain active with the external antenna attached.\u00a0 The external antenna is effective only to the extent that the phase and amplitude of its signal compliment or reduce that produced by the ferrite loop.<\/p>\n

\"\"<\/a><\/p>\n

In addition to two intermediate frequency (IF) stages, the circuitry includes a 455 kHz ceramic filter in the base circuit of the first IF stage.\u00a0 This provides very good selectivity.\u00a0 Never satisfied the way things are, when I first got these radios, I duplicated a third IF stage in one of the units.\u00a0 The result was a nice tight bandwidth still providing good audio.<\/p>\n

The \u201cimprovements\u201d in the -656A seem to be focused on the reduction of production costs.\u00a0 I\u2019ve already mentioned the tone switch for one.\u00a0 Another example is the replacement of discrete components in the -655\u2019s audio amplifier with a whopping 0.5-watt integrated circuit in the 656A.\u00a0 Having no way to make a performance comparison, I will say my experience with the -656A is that it is still a very hot radio.<\/p>\n

The TRFs filled a relatively minor marketing niche, namely DXing enthusiasts and perhaps a small number of expatriates who wanted to listen to broadcasts from their old hometowns.\u00a0 The format evolution of medium wave broadcasting was already well on the way toward news-talk-ethnic broadcasting, and the appeal to rock \u2018n rollers or virtually any music lovers just wasn\u2019t there.\u00a0 A sensitive radio had to include an FM band.\u00a0 So, the TRFs faded into history sometime in the early \u201880s.<\/p>\n

Enter the long-distance \u201csuperadios,\u201d notably General Electric\u2019s Superadios I, II, and III in the 1990s.\u00a0 Radio Shack itself produced a clone-like Optimus 12-603.\u00a0 The \u201csuper\u201d by that time referred more to the audio quality than the sensitivity.\u00a0 This later generation featured two higher-quality speakers packaged in a cabinet with somewhat better acoustics, separate base and treble controls, all driven by a higher-powered audio amplifier.<\/p>\n

Having worked in the industry for a couple years as an assembler, I have never been convinced that inclusion of multiple band coverage does not result in some performance compromise.\u00a0 Radios such as the TRFs have a special appeal to me.\u00a0 The General Electric P780 is another well-regarded example of an AM-only, high-sensitivity, radio.\u00a0 Maybe you have a favorite of your own.\u00a0 If you\u2019re into tinkering, and even if you\u2019re not, a functional TRF or such radio can provide a lot of cheap entertainment.<\/p>\n

\"\"<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Many thanks to\u00a0SWLing Post\u00a0contributor,\u00a0Bob Colegrove, for the following guest post: Remembering the Radio Shack TRFs As recalled by Bob Colegrove There has always been an interest in DXing on the cheap.\u00a0 At the same time, most of us don\u2019t want to sacrifice any more capability than necessary.\u00a0 In the late 1970s and the early 1980s, […]<\/p>\n","protected":false},"author":15,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[373,3194,433,3,3196,26],"tags":[625,7988,9537,9538,9539,9541,9540],"class_list":["post-50861","post","type-post","status-publish","format-standard","hentry","category-am","category-guest-posts","category-mediumwave","category-news","category-portable-radio","category-radios","tag-am-radio","tag-bob-colegrove","tag-radio-shack-trf","tag-radioshack-12-655","tag-radioshack-12-656a","tag-trf","tag-tuned-radio-frequency-receiver"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pn3uc-del","jetpack-related-posts":[{"id":15755,"url":"https:\/\/swling.com\/blog\/2015\/11\/guest-post-trip-down-shortwave-memory-lane-via-vintage-radioshack-catalogs\/","url_meta":{"origin":50861,"position":0},"title":"Guest post: Trip Down Shortwave Memory Lane via Vintage RadioShack Catalogs","author":"Thomas","date":"November 23, 2015","format":false,"excerpt":"Many thanks to SWLing Post contributor, Mario\u00a0Filippi (N2HUN), for the\u00a0following guest post: Trip Down Shortwave Memory Lane via Vintage RS Catalogs -Mario Filippi (N2HUN) Attached is a wonderful website containing archived Radio Shack catalogs and sales flyers going back to 1939, surely of interest to SWLs, hams, and other electronics\u2026","rel":"","context":"In "Articles"","block_context":{"text":"Articles","link":"https:\/\/swling.com\/blog\/category\/articles\/"},"img":{"alt_text":"RadioShack-Catalog","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2015\/11\/RadioShack-Catalog.jpg?resize=350%2C200","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2015\/11\/RadioShack-Catalog.jpg?resize=350%2C200 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2015\/11\/RadioShack-Catalog.jpg?resize=525%2C300 1.5x"},"classes":[]},{"id":39419,"url":"https:\/\/swling.com\/blog\/2019\/09\/guest-post-the-national-association-of-armchair-adventurers-naaa\/","url_meta":{"origin":50861,"position":1},"title":"Guest Post: The National Association of Armchair Adventurers (NAAA)","author":"Thomas","date":"September 3, 2019","format":false,"excerpt":"Many thanks to SWLing Post contributor, Bob Colegrove, who shares the following guest post: National Association of Armchair Adventurers (NAAA) as recalled by Bob Colegrove Those of you who were into SWLing in the late \u201850s or early \u201860s may remember the NAAA.\u00a0 It was an engaging promotional effort by\u2026","rel":"","context":"In "News"","block_context":{"text":"News","link":"https:\/\/swling.com\/blog\/category\/news\/"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2018\/07\/Radio-Dial-1024x679.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2018\/07\/Radio-Dial-1024x679.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2018\/07\/Radio-Dial-1024x679.jpg?resize=525%2C300&ssl=1 1.5x"},"classes":[]},{"id":12356,"url":"https:\/\/swling.com\/blog\/2015\/02\/chris-retro-review-of-the-radio-shack-dx-397-sangean-sg-622\/","url_meta":{"origin":50861,"position":2},"title":"Chris’ Retro Review of the Radio Shack DX-397 (Sangean SG-622)","author":"Thomas","date":"February 18, 2015","format":false,"excerpt":"SWLing Post reader, Chris Freitas, has sent me a link to a recent review he made of the RadioShack DX-397. I know many of us have had one of these little analog radios (branded as RadioShack or the original Sangean SG-622) at some point. Chris has fond memories of the\u2026","rel":"","context":"In "News"","block_context":{"text":"News","link":"https:\/\/swling.com\/blog\/category\/news\/"},"img":{"alt_text":"SangeanSG-622","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2015\/02\/SangeanSG-622.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":8729,"url":"https:\/\/swling.com\/blog\/2014\/02\/radioshack-to-close-500-retail-stores\/","url_meta":{"origin":50861,"position":3},"title":"RadioShack to close 500 retail stores","author":"Thomas","date":"February 5, 2014","format":false,"excerpt":"After serving up a comical, self-effacing Super Bowl ad\u00a0on Sunday, RadioShack's stock momentarily surged, only to plummet after RadioShack announced yesterday that they are to close about 500 of their 4,500 retail stores in the coming months. RadioShack admitted through its ad that the retailer's mindset had been \"stuck in\u2026","rel":"","context":"In "News"","block_context":{"text":"News","link":"https:\/\/swling.com\/blog\/category\/news\/"},"img":{"alt_text":"RadioShackAdClip","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2014\/02\/RadioShackAdClip-300x170.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":10354,"url":"https:\/\/swling.com\/blog\/2014\/07\/grab-a-radio-shack-dx-402-for-24-and-change\/","url_meta":{"origin":50861,"position":4},"title":"Grab a Radio Shack DX-402 for $24 and change","author":"Thomas","date":"July 25, 2014","format":false,"excerpt":"I just noticed that Blinq.com has the\u00a0RadioShack DX-402 (Sangean ATS-505 re-badge) for $27.09 shipped. \u00a0If you use the offer code WEEKEND10 it will take an additional 10% off at checkout for a total of $24.62 shipped. This is an excellent price, even for an open box deal. Last time the\u2026","rel":"","context":"In "News"","block_context":{"text":"News","link":"https:\/\/swling.com\/blog\/category\/news\/"},"img":{"alt_text":"RadioShack-Shortwave","src":"https:\/\/i0.wp.com\/swling.com\/blog\/wp-content\/uploads\/2014\/07\/RadioShack-Shortwave.jpg?resize=350%2C200","width":350,"height":200},"classes":[]},{"id":49864,"url":"https:\/\/swling.com\/blog\/2021\/08\/bob-colegrove-on-the-joys-and-challenges-of-tuning-analog-radios\/","url_meta":{"origin":50861,"position":5},"title":"Bob Colegrove on “The Joys and Challenges of Tuning Analog Radios”","author":"Thomas","date":"August 1, 2021","format":false,"excerpt":"Many thanks to SWLing Post contributor, Bob Colegrove, who recently shared this excellent article and has kindly allowed me to share it here in the the Post. 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