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Author Topic: Boat anchors in Hollywood  (Read 24328 times)
KAPT4560
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Posts: 554




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« Reply #30 on: August 29, 2015, 04:47:40 AM »

  There was an old eHam thread that addressed how to go about a makeshift tube transceiver. 

  http://www.eham.net/ehamforum/smf/index.php?topic=42397.0;wap2
 
 The ham I spoke with did the audio output-to-transmitter mod to his S-20R. He got "across the river" with it.  It was low power and it struck me as a novel idea when you didn't have the resources for a proper transmitter.
  There were plenty of single tube oscillator/exciter 'glowbug' projects in the ARRL publications at the time. I built one and I remember how hot it ran when keyed with a plate load, but it remained fairly stable.

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W1BR
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« Reply #31 on: August 29, 2015, 11:04:37 AM »

Found it!!

http://rigreference.com/en/rig/2804-Hallicrafters_SR_75

This a Hallicrafters S-38 that uses the audio tube for both audio, and with some simple changeover circuitry, the same tube serves as a cathode keyed CW transmitter!  The design is very clever... but I'd hate to have the been the Novice who started off with this radio!  It wasn't very popular, and is somewhat rare.

Pete
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JS6TMW
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Posts: 1255




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« Reply #32 on: August 29, 2015, 07:45:10 PM »

Well, I'll be durned! Thanks for that...  I'll bet it's rare.

There is a dedicated xtal oscillator/multiplier, but it does indeed use the audio stage as the RF amp. I hope there was a polarized line cord or tha antenna would get squirrely if it's plugged in the wrong way.

Steve
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K0OD
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« Reply #33 on: August 29, 2015, 11:18:56 PM »



Wow, the SR-75 "transceiver" is new to me. Extremely rare, no doubt. I'm sure some current owners don't even know about its 10 watt transmitting ability. Virtually identical in appearance to  early S-38 models.

Reminds me of the obscure Hammarlund HQ-105TR general coverage receiver (ca 1961) that has a single channel CB transmitter built-in.
http://www.universal-radio.com/catalog/commrxvr/hq105tr.html
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N6OIL
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Posts: 31




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« Reply #34 on: August 30, 2015, 02:10:27 PM »

I thought I saw a Kenwood hybrid on the Avengers: Age of Ultron. Can someone fact check that?
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K4PIH
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« Reply #35 on: September 03, 2015, 09:48:14 PM »

Here's the Gilligan link for the S40:

gilligansisle.com/radio.html
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N2SR
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Posts: 1207




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« Reply #36 on: September 04, 2015, 05:25:15 AM »

In one issue of QST, the previous column writer (K2TQN) of Vintage Radio described being on the set of Paranoia, where they used his old radios as props for scene. 

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If no one is doing it that way, there is a probably a very good reason.
N2EY
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Posts: 5082




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« Reply #37 on: September 04, 2015, 02:31:32 PM »

The SR-75 is indeed rare - and with good reason!

The various versions of the S-38 receiver ranged in price from about $40 to $50, depending on model and retailer. The SR-75 cost about $80 during the short time it was made. Which meant you were paying $30 to $40 for a ten-watt crystal-controlled transmitter! There were much better choices, and I suspect most amateurs made them.

73 de Jim, N2EY
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K0OD
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« Reply #38 on: September 04, 2015, 09:59:12 PM »

The Hallicrafters SR-75 dispensed with antenna switching by using separate antennas for transmit and receive. There was a 3-conductor terminal strip on the back for the receiver antenna and a single wire on the other side of the radio to feed the transmitting antenna. The transmitter's oscillator and amp tuning controls are on the back of the chassis. A single crystal socket is inside the cabinet. For transmit, it seems that each band required its own manually plugged in coil inside the cabinet.  Ugh!

http://gmcotton.com/ham_radio/misc%20manuals/Hallicrafters/Hallicrafters_SR75%20HF%20Tranciever_Manual.pdf
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W1BR
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« Reply #39 on: September 05, 2015, 06:53:12 AM »

It was a kludge from the get go. Wink  I wonder how many Novices gave up ham radio after trying to use that radio on 15 meter CW?

Pete
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G3RZP
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Posts: 1280




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« Reply #40 on: September 05, 2015, 07:01:34 AM »

Peter,

More likely
Quote
I wonder how many Novices gave up ham radio after trying to use that radio
?
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K0OD
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Posts: 3030




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« Reply #41 on: September 05, 2015, 07:57:58 AM »

The SR-75 is indeed rare - and with good reason! ...
73 de Jim, N2EY

Another reason for the rarity of the SR-75 was that it broke new ground... Sorta. Compare it with Heath's wildly popular AT-1  transmitter that came out in '53. The 35 watt AT-1 had a front panel crystal socket, band switching from the front panel including the new 15-meter band,  grid and plate current metering. Plus it could be upgraded with a Heath VFO and antenna tuner. Cost $29! I guess too that any ham who wanted a cheap bad transmitter in 1950 could just buy a Command Set for under $5.

From QST in 2007. The KWM-1 and its Competition
"Hallicrafters was the first major American manufacturers of ham gear to put a rig resembling a transceiver for HF into mass production. Its SR-75, introduced in late 1950, actually was a modified version of the company's entry-level HF receiver, the S-38B. The SR-75 could put out a few watts of crystal controlled CW on 80 through 10 meters." [not 15-meters]
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JS6TMW
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« Reply #42 on: September 05, 2015, 07:53:06 PM »

The SR-75 is indeed rare - and with good reason! ...
73 de Jim, N2EY

From QST in 2007. The KWM-1 and its Competition
"Hallicrafters was the first major American manufacturers of ham gear to put a rig resembling a transceiver for HF into mass production. Its SR-75, introduced in late 1950, actually was a modified version of the company's entry-level HF receiver, the S-38B. The SR-75 could put out a few watts of crystal controlled CW on 80 through 10 meters." [not 15-meters]


I am not an expert on WWII military radios, but I am fairly sure that there was some gear we would recognize as transceivers for VHF and portable use.
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K0OD
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Posts: 3030




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« Reply #43 on: September 05, 2015, 08:21:57 PM »

"that there was some gear we would recognize as transceivers for VHF and portable use"

Yes, plenty of that, some even in the 1930s, but not for HF.

Here's the article I was referring to regarding the 1957 Collins KWM-1 and other early HF transceivers such as the radical Cosmophones.
http://www.arrl.org/files/file/QST%2520Binaries/obrien0107.pdf
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JS6TMW
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« Reply #44 on: September 05, 2015, 10:50:04 PM »

"that there was some gear we would recognize as transceivers for VHF and portable use"

Yes, plenty of that, some even in the 1930s, but not for HF.

Here's the article I was referring to regarding the 1957 Collins KWM-1 and other early HF transceivers such as the radical Cosmophones.
http://www.arrl.org/files/file/QST%2520Binaries/obrien0107.pdf

I should have specified that there were WWII rigs that used shared common components for transmit and receive, not just a tx and an rx in the same box.

Interesting article on some real obscure rigs. But the KWM-1 was a lovely little rig.
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