HFU HF Underground
Technical Topics => Part 15 AM and FM Station Operation => Topic started by: ThaDood on July 24, 2020, 2039 UTC
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https://www.smecc.org/knight_kit_home_broadcasters_-_allied_electronics.htm
Ya know, of all the Part #15 kits that have been out there through the ages, none have been, or even still, talked about as much as this one. Folks are still kickin' themselves for getting rid of it, or when their parents did. People still want this today!
Heck... I'd still take one.
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Yeah, my first build from Knight. Followed by the Space Spanner and Star Roamer.
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That's awesome! And so simple too, big parts to solder too, and with tubes it must have sounded smooooth on the radios of the times.
I've never seen one in action, but long ago read an article about a guy who described his Kinight like a pro radio station, how as a kid he thought it was even better, no expensive calibration or metering and if something goes wrong, it's a cheap matter to replace a tube. That was a great article!
It only cost $11.95 for the Knight Kit!
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Wow, cool to see hfunderground has added a part 15 specific section. Anyway , there's some cool knight broadcaster stories at knightkit.com/fanstories.html They were apparently very capable. The range seemed to average from a few blocks to a mile, but some of the more non compliant installs faired much better, as one of the stories explains:
Excerpt:
".....Our antenna ran about.. 900 hundred feet, a simple long wire, strung about 30 feet over the ground. Our tests showed us getting pretty good coverage out to about 10 miles. As kids, we didn't know any better and thought them rules about antenna length didn't pertain to us.
Our shows were the latest "Nifty Fifty records," news from last nights newspaper and assorted comedy skits...."
There's another story the antenna was fabricated using a fishing pole to support the wire on top the house which got out a solid four miles in all directions.
Elsewhere there is a webpage about someone who still uses one of the original knight kits for broadcasting today, but he only does it one day a year.. every year.. I forget the details and now I can't find the link, but it was a license AM station who does it.. Does this story sound familiar to anyone? It's probably the same story which Kingbear refers to.
Also recall someone at the antiqueradio.com forums mentioning they had utilized a knight kit for their drive-in theatre in the 1960s
Another cool story involved an FCC visit at https://nofars.net/jacksonville_radio_collection/fcc_visits_fun_radio
Excerpt:
"..... The polite FCC official made it clear that we could not use another licensed call sign, WFUN, that our antenna length was excessive giving too much coverage area. There was about 20 feet of coax from his two story home going to a 3 foot metal antenna up about 35 feet above ground..."
Lastly, of worthy mention, in the late 1950s at least one of the National parks had been using the knight kit broadcaster in a lead car for the tourist caravans following behind. (https://2.bp.blogspot.com/-MvesU0LqMDY/Ws5cZq3C2eI/AAAAAAAADWg/adJqZ0WAXw4lkS9EzH-Bala64ghC5nlswCLcBGAs/s1600/part15-NPS1957.png)
There are now Knight Broadcaster replicas for about $200 on ebay, but he doesn't supply the tubes with the sale... What the heck!
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The Knight must have been out at exactly the right time, when rock & roll radio was hitting big and kids all wanted to be DJs, so it was perfect timing, just take the phono oscillator, which had been out for many years, and make it junior DJ friendly, with a mike and phono input, and make it put out some power, and that's a neighborhood radio station.
Another article I saw once was kids had their own home station, the teen age guy and his younger brother ran it, Dad might have helped to build it, and they had news reports every morning and local announcements. The signal reached down their block, and they had listeners tuned in. People remember it in that it was filmed for a news report that even ran on AFRTS I think.
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Yes!!! And something like this can be done, again. Either a solid state version, or keep it tube-type.
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For anyone interested there is an original Knight kit Wireless Broadcaster on eBay for $84, there's no bids on it and it ends in 3 days. It does not appear to include the tubes, however
https://www.ebay.com/itm/Knight-Wireless-Broadcaster/324440515964
(https://i.ebayimg.com/images/g/CScAAOSwx8Nf8gYq/s-l400.jpg)
There is also newer replica models for sale, when I first saw them about a year ago the price
started at $149 or 'Buy it Now' $194, but I see they have gone up to $244 now. It doesn't include the tubes either...
https://www.ebay.com/itm/UNBUILT-KIT-vintage-vacuum-tube-Knight-RADIO-BROADCASTER-AMPLIFIER-repro-set/293922978847
Personally that is more than I would ever want to pay for the repo, although I would probably go for the $84 original if I weren't so broke right now.
Last year I had looked up (two 50C5 tubes, and a 12AX7), the total cost for all three tubes with somewhere around $70 if I recall right.
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That's the classic Knight I've seen on review sites for awhile. Nice with the solid metal cabinet. Too bad it doesn't have the tubes, they might have burned out and the owner threw them away, or maybe fell out of their sockets during a move or something.
I've heard stories that these Kignts have hum, frequency drift and you can even get a light shock from the case of it, and with all that would you still use it today on your station, or is it more for old time's sake, like doing a show once a year because you learned radio on it as a kid?
I didn't think vacuum tubes were so expensive, but maybe the Knight's are because they're in demand, since 5 years ago I got two power pentode tubes for old hifi output, and they were $10, shipping included 6bq5 I think. The guy said they tested good on a tube tester.
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Tube Depot shows the 50 C-5 to be $30 the each. There are a number of versions of the 12AX7 tubes prices ranging from $10 to $250 a piece, I presume the $10 one would be fine, but I really wouldn't know.
https://tubedepot.com/products/50c5
A couple speculations I've made concerning these transmitters.. Based on the copyrights in the manuals, the Knight broadcaster came out in 1953 but did not show up in the Allied radio catalogs until 1954.. Then in 1956 the alternate provision now known as 15.219 was created, but not finalized until in 1957. The next Knight model which added amplifier circuitry came out in 1958 which included in the manual a FCC certification to attach to the bottom of the transmitter.
It stands to reason that the original model was designed to conform with 15.209, and the later model been designed to conform with 15.219 and it's 10-ft limit. Now, with that in mind let's consider the revisions to 15.219 in 1957, which at that time was known as 15.204....
[Docket No. 9288; FCC 57-790]
...The Commission proposed in its
November 1956 Notice that low power
communication devices be operated on
frequencies below 1600 kc. In the band
10-1600 kc, the proposal contained field
strength limitations and, alternatively,
power input and antenna length limits
for the bands 160-190 kc and 510-1600
kc. No comments directed to these par-
ticular limitations have been received.
Recently, however, additional radiation
data were obtained for low power com-
munication devices operating in the
band 510-1600 kc. The data indicate
the advisability of reducing the power in
order to further limit the area within
which interference may occur. There-
fore, the maximum allowable input
power in the band 510-1600 kc has been
reduced from 200 to 100 milliwatts as
set forth in Section 15.204 of the ap-
pended rules.
I couldn't help but to suspect that the Knight Broadcaster was somehow behind that "additional radiation data"" which the FCC had recently acquired, resulting in the decision to lower the power from 200 to 100 mw, it was after all the most iconic part 15 transmitter of the 1950s and 60s thus the most likely culprit! So I set out to confirm this theory.....
So much for gut feelings, only months prior to the FCC reducing the power limit, they did conduct feild strength measurements on a part 15 device in their lab, but it wasn't a Knight Broadcaster, it was a "Radio-Talkie Radio-Vox ". They have manufactured about 20,000 of these walkie talkies and now had the federal trade commission investigating them four false claims, which is what prompted these lab tests to occur. Although I don't really see how it influenced the reduction to 100 mw, it's just too much of a coincidence to have not been the culprit. Not to get too far off track, but here's a brief excerpt from the report...
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Office of Chief Engineer
Laboratory Division
Tests of Radio-Talkie Radio-Vox
Manufactured by Western Radio, Inc.
April 16, 1957
.......The instructions with the instrument suggest an additional antenna
of 50 to 100 feet be used as well as connections to various
other objects, such as lamps, telephones, bedsprings, large
metal windows, doors, screens, etc., as well as to “outside
aerial wires of any type.” Provision is also made for a
ground connection. The transmitter itself consists of a transistor supplied
by a 6-volt battery. The unit is designed to operate in the lower part of the standard broadcast band and is tunable.......
Conclusions:
At 820 kilocycles, the Part 15 limit is 15 microvolts per
meter at 190 feet. At 950 kilocycles, the 15 microvolt limit
applies at 165 feet. The values obtained in (c) and (d)
above are well outside those limits. The unit tested was
within the limits when used only with the whip antenna
and extension provided, or with short extension thereof.
................................
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Maybe interesting for anyone!
https://www.6v6.co.uk/tube-transmitter-kits.html (https://www.6v6.co.uk/tube-transmitter-kits.html)
https://www.6v6.co.uk/solid-state-transmitters.html (https://www.6v6.co.uk/solid-state-transmitters.html)
André
CoolAM Radio
the Netherlands
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That 1W, 10kHz step, Spitfire would be great for Carrier-Current Coupling for the USA and Canada. And, permissible too.
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Ooh 'Permissable'... :'(
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That's a good use for 1Watt here, that if the intercoms use only a fraction of that, then a watt might be nice for a small station.
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Coincidentally I ran across this today:
Part 15 Old Style Tube Broadcaster - Part 1: https://www.youtube.com/watch?v=-pJ-kErTI54&feature=youtu.be
Part 15 Broadcast Band Transmitters part 2: https://www.youtube.com/watch?v=rs0w7ZS9hFE
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NICE!!!!! I copied & paste those VID on to The FRN. There are Part #15'ers over, that don't come over here. Duh-know why, but.... Oh... And I also dumped these to my newer Minds.com page, https://www.minds.com/groups/profile/876322093051867136/feed
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Lit up is a good term, with that transformerless design!