FM sets for the old 45MHz FM broadcast band
FM sets for the old 45MHz FM broadcast band
The Zenith bakelite
set pictured above had the old 45MHz FM
band. A later version of this set, on the
right, was made without this band. The wooden Zenith set below
had the 45MHz band.
One can usually find a set like these
on one of the auction websites about once a month.In 1945 the FCC decided that FM would have to move from the established 42 - 49 megahertz pre-war band to a new band at 88 - 108 megahertz, to make way for television. Both in frequency spectra and consumer dollars. Therefore, all radios with an FM band of 88 to 108MHz are post-war. RCA's David Sarnoff in particular wanted FM to "go away" so the public wouldn't be distracted from buying his latest up and coming product: televisions. Maybe if Armstrong said to Sarnoff in the early days that FM sound would be perfect for the television soundtrack, they wouldn't have become rivals. Turns out modern TV doesn't even use this spectra. There was to be a channel 1 here. But co-channel interference from stations in distant towns would occasionally happen. And this would be worse for television than FM signals, as FM has the FM capture ratio working in its favor. FM receivers will capture a signal that is a few dB stronger than another co-channel signal, without the weaker signal causing interference. TV, being an AM type signal with one sideband partially suppressed, would suffer more severe interference for the same given signal strengths. Seems odd that the FCC chose to replace FM with TV in this spectra, but they were more politically motivated by RCA than scientifically.
Channel 1 was to be used by low power TV stations, and police and fire users in areas without a channel 1 TV station. Interference to a TV channel from a fire or police station would be particularly objectionable when propagation was good. TV channel 1 was dropped, and land-mobile fire and police now use this spectra everywhere. These users would sometimes hear distant signals, as the local signals are usually off. They do not broadcast continuously like commercial stations. Capture ratio doesn't help you ignore weaker signals if your local station isn't transmitting. Fire and police departments in different jurisdictions use differing audio tones to help discriminate between each other. Some older cordless phones can be heard on these frequencies. Commercial broadcast would have been a better use of this band.
Because of this reallocation, more than half a million FM
receivers and
some 50 transmitting stations would be
rendered obsolete. My father once had a 45MHz
FM tuner, a Meissner 9-1047A, (pictured below)
that was also rendered obsolete. It tuned from 41.2 to 50.4MHz. He didn't
receive any compensation or trade-in offers for his now useless radio he spent
his own money to purchase.
The Yankee Network of 45MHz stations in
New England did not survive the change.
But the worse fear for Edwin Armstrong (inventor of FM) would be a loss
of confidence in FM by the
growing number of faithful hi-fi listeners.
This move to higher frequencies, however, proved to be
only a temporary setback for FM. By 1950 there were over
600 FM stations on the air in the new band.
Zenith,
GE, Westinghouse, Temple (above Temple not in the collection) and Stromberg Carlson, to
name a few paid patent
royalties to Edwin Armstrong for FM, but RCA wouldn't.
Armstrong instituted a suit against RCA and NBC charging them with
infringing his five basic FM patents. RCA's David
Sarnoff figured he could outlast Edwin Armstrong in court in patent
infringement lawsuits. Sarnoff wasn't thrilled with FM
being selected by the FCC to carry sound for TV. RCA did outlast Armstrong, who went
broke.
My Zenith 45MHz FM radio model 8H023 looks very
similar to my 8H034Z above. Uses the same chassis (8C01), even.
Not in my
collection, two Philcos with AM, SW, and the old prewar FM band,
marked with FM channel numbers 21 to 99.
Philco 42-355 
Another not
in my collection, a Silvertone 6143.
I was outbid for this Pilot AM/FM set. Note that the
FM band on this set is the old 45MHz band, and that the normal
AM band is also present. Possibly one of the first AM/FM
sets ever produced.
Another AM/FM prewar set, this one by Emerson. It has a push-pull
pair of 25L6s and separate AM and FM front ends and IFs. And
an eye tube.
I modified a small B&W portable TV set by extending
channel 6 into the modern FM band (do that by reducing the
inductance of the coil of the TV set tuner local oscillator),
and tapping the TV IF (which happens to be in the range of 40 to 47 MHz)
after the tuner but before the IF filters. Then feeding that into
the 45MHz FM radio antenna terminals for FM broadcast reception.
Alternatively, I modified an old ham radio band converter from 146MHz input to 30MHz out to 100MHz in to 45MHz out. Changed a crystal and messed with its tuned circuits. I used two crystals, one for "upper" 108-100 and one for "lower" 92-100. Better than that portable TV I had kludged before. To obtain a usable crystal for "upper" I bought a pair of toy walkie talkies (the superregenerative AM kind) and removed the 49.88MHz crystal. The converter's LO is a trippler circuit, which gets me up to around 145MHz for the LO. Beat that against FM broadcast signals, and you'll get them on the 45MHz FM set. One problem is that the crystal being at 49.88MHz, I'll get a birdie there on the FM set. Not a real issue unless a station of interest gets clobbered there.
Yet another and possibly easier method (if you are familiar with solid state TV and VCR electronics) is to use an old cable ready VCR, the kind that can tune cable channels 95, 96 and 97. These happen to be the same spectrum as the modern FM broadcast band. You'll need to tap the 45MHz video IF inside the VCR. Older VCRs will have a tuner (just the front end, ie, RF amp and mixer) module and and IF out RCA jack running to the main circuit board. Others will have the front end, mixer, and IF filters and amps and detectors in one metal box. You want the video IF just after the mixer but before the video IF filter, which is usually an epoxy covered glob, or a fat looking transistor style can. Tune in cable channel 96, with an antenna connected to the VCR F connector. Using a small capacitor, like 100pF in series with the center conductor of some coax you have feeding the 45MHz FM set, poke around the video IF filter to see if you can find some FM stations (you'll have to tune the 45MHz FM set up and down the dial as well). The VCR's local oscillator will be running at 143MHz, subtract a strong FM station's frequency (one around 97MHz) from 143 to get an idea where the station will appear in the video IF. Say a station at 97.7, 143 - 97.7 = 45.3MHz, so tune the 45MHz FM set around there. You should be able to find a spot on the video IF filter that gives good signal stregth, so solder the cap to that spot, and the coax shield of the coax to the 45MHz FM set to a nearby ground near the video IF filter. The cap is to block DC. Note that stations higher in their carrier frequencies will appear lower on the dial of the 45MHz FM set. Like 98.7 will show up at 44.3 MHz.
Seems the old FM band used the same or close to the same deviation and preemphasis settings as the modern FM band.
After a recap, the radio got more sensitive, thus the brighter phosper on the eye tube target next to the shadow area when the radio receives a strong signal.
Replaced the grill cloth, and put a light coat of semigloss
polycrylic on the cabinet (didn't do a proper restore because I
didn't want to lose the decals). Also replaced a bad resistor in the
audio amp to fix distortion. It uses a pair of 25L6's push pull,
fed by a floating paraphase phase inverter.
dial detail:
This radio, in bakelite color, appears in the movie "War of the
Worlds". Here people are listening to Martian reports.
My father's Meissner 9-1047A:
Diagram of my father's Meissner: ("M" means "thousand"
in this diagram)
K45LA Don Lee Broadcasting System, Los Angeles 44.5
K49LA Hughes Tool Co, Los Angeles, 44.9
KALW Board of Education, San Francisco United School District San Francisco, 42.1
WTIC-FM Travelers B/c Service Corp. (WTIC), (45.3), Hartford W53H
WDRC-FM WDRC Inc. (WDRC), (46.5), Hartford W65H
WINX-FM WINX B/c Co. (WINX), (43.2), Washington DC
WTOP-FM/WHUR Jansky & Bailey, Washington DC 43.2
WOWO-FM Westinghouse Radio Stations (WOWO), (44.9 mc), Ft. Wayne
WABW Associated Broadcasters (WBBW), (47.3 mc), Indianapolis
W45V Evansville On the Air, Inc, Evansville IN, 44.5
W79C Oak Park Realty & Amusement, Chicago 47.9
WBEZ Board of Education, City of Chicago, Chicago, IL 42.5
WWZR/WEFM/WUSN Zenith Chicago W51C 45.1
WIUC University of Illinois, Urbana, IL 42.9
WBKY University of Kentucky, Lexington, KY, 42.9
WBZ-FM Westinghouse Radio Stations (WBZ), (46.7 mc), Boston W67B
WMNE Yankee Network (43.9 mc), Boston
WGTR Yankee Network (WNAC), (44.3 mc), Boston W43B
WMTW-FM Yankee Network, Boston W39B
WBZA-FM Westinghouse Radio Stations (WBZA), (48.1 mc), Springfield
WENA Evening News Assn. (WWJ), (44.5 mc), Detroit
W77XL WJIM Inc, Lansing, 47.7
W81SP Westinghouse Radio Stations, Inc, Springfield MO, 48.1
KMBC-FM Midland B/c Co. (KMBC), (46.5 mc), Kansas City
WFMN Edwin H. Armstrong (44.1 mc), Alpine, NJ
WNBF-FM Wylie B. Jones Adv. Agency (WNBF), (44.9 mc), Binghamton
WQXQ Interstate B/c Co. (WQXR), (45.9 mc), New York
WABF Metropolitan Television Inc. (47.5 mc), New York
WEAF-FM/WNBC-FM National Broadcasting Co, New York 42.6
WABC W67NY Columbia Broadcasting System Inc, NY, 46.7
W99NY Frequency Broadcasting Corp, NY, 49.9
WHNF W63NY Marcus Loew Booking Agency, NY, 46.3
W55NY William G. H. Finch, NY, 45.5
WNYC-FM City of New York, Municipal Broadcasting Co, 43.9
WOR-FM Bamberger Broadcasting Service, New York 43.4, 47.1
WGYN W47NY Muzak Corp, New York, 44.7
WHFM Stromberg-Carlson Co. (WHAM), (45.1 mc), Rochester W51R
WHEF WHEC Inc. (WHEC), (44.7 mc), Rochester W43R
WTAG-FM Telegram Publishing Co, Worcester ???
WGFM General Electric Co. (WGY), (48.5 mc), Schenectady
WBCA Capitol B/c Co. (44.7 mc), Schenectady
WMIT Gordon Gray (WSJS), (44.1 mc), Winston-Salem, NC
WELD RadiOhio Inc. (WBNS), (44.5 mc), Columbus W45CM
WBOE Cleveland City Board of Education, Cleveland, OH 42.5
KYW-FM Westinghouse Radio Stations (KYW), (45.7 mc), Philadelphia
KDKA-FM Westinghouse Radio Stations (KDKA), (47.5 mc), Pittsburgh
W81PH Seaboard Radio Broadcasting Corp, Philadelphia 48.1
WSM-FM National Life & Accident Insurance Co. Nasvhille 44.7
K47SL Radio Service Corp. of Utah, Salt Lake City 44.7
WTMJ-FM Journal Co. (WTMJ), (45.5 mc), Milwaukee W55M
WEBC-FM Head of the Lakes Broadcasting Co, Superior, Wi 43
Source, and more info on early FM is at: Jeff Miller's Broadcasting History Pages
Realistic PRO-2B. Two independent
dial scales. Normally intended for NBFM, it can accept
WBFM signals like those of the FM broadcast band if downconverted
to 45MHz, for example.
Channel master 6252A. An analog
tuned VHF Lo and Hi communications receiver
Uniden Bearcat
BC140 Scanner.
To make it a 16 channel
scanner, clip the diode crossing over
(component side) the biggest chip on the
main board, IC8.
Japan has their FM broadcast band
between 76 and 92MHz. And television channels occupy the rest
of what would be the American FM band.
This set is from the USSR. Better dead than red! 
Their FM
band goes from 66 to 73MHz.
