RF Cafe Software
About RF Cafe
1996 - 2022
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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RF Cafe visitor and occasional contributor Gary S. just sent me photos of two fine looking vintage U.S. Navy radios that he restored to working order. The condition of the front panels on both radios is amazingly good. Here is Gary's Tale of Two Radios.
"I thought I would share with you my latest refurbished WW-II Navy receivers I acquired last spring. I say refurbished because I do what repairs are needed to get them operational again and then clean them up a bit. I consider a restoration to mean made to work and look like new again using original parts if they are available.
The first receiver is the Hammarlund RBG-2 general coverage HF communications receiver. It covers from 540 kc to 32 mc. They didn't use Hertz in those days. It is basically an HQ-120X beefed up to Navy specs. The band spread dial is calibrated for the maritime HF communications bands. It has a BFO for CW and weak signal detection. No SSB in those days. It is a light-weight at around 65 pounds.
The second receiver is a Scott RBO-2 shipboard entertainment receiver. Also known as the moral[e] receiver. It receives the AM broadcast band and 5.6 to 15.6 mc split into 2 overlapping bands. Mode is AM only. As its name suggests, it was used to tune local or shortwave broadcast stations to be played on the ship's entertainment PA system. I don't doubt this receiver has been tuned into some of the Tokyo Rose broadcasts. This receiver is a heavy weight at 103 pounds.
Both of the receivers were DOA and looked like they had been through a war. Once I got 'em working, I gave the front panels a good cleaning and decided they didn't look too bad, battle scars and all. So I left the front panels in their original finish.
I pounded out the dents and dings in the cabinets and gave 'em a fresh coat of paint.
They don't just sit around here collecting dust. I fire them up often and tune the ether. They both have a great mellow sound to them." (see more notes below photos)
Shipboard Entertainment Receiver (aka Morale Receiver)
"I have attached additional photos per your request. I didn't think to take any "before" photos. These show the chassis after I cleaned them up.
There wasn't too much difference in the Scott RBO's appearance. The varnish that was generously applied didn't look much better after I cleaned off the dust and dirt. However, the varnish sure went a long way to preserve the components. All of the paper capacitors are still intact and didn't dry out over the years. I was amazed. There was very little effort needed to bring the beast back to life.
Not so with the Hammarlund RBG. All of the paper caps had to be replaced. The yellow polystyrene caps are the new ones. Many of the old paper caps were in metal cans and were oil filled. The fiber terminal bushings dried out and the oil leaked everywhere. What a mess that was.
Both receivers have multiple audio output impedances that can be used in a variety of audio distribution systems. The matching speakers for these receivers have the required transformer built in. Of course I don't have the matching speakers. Dave from Dave's Homemade Radio has the solution. He posted detailed data on the Bogen T-725 audio transformer showing how to match an 8 Ohm speaker to a wide range of impedances.
Details here: http://makearadio.com/misc-stuff/t-725.php Dave's a cool fellow and has a lot of interesting things going on in his web site."
"I forgot to answer your question on how I came across them. Craigslist. I browse the listings for Stockton CA for ham, vintage, antique, military radios to see what may be in the general area. I found these in Martinez CA, nearby my last Navy duty station on Mare Island in Vallejo. Among other things, Mare Island was a shipyard. It is a possibility the receivers were removed from a WW-II era ship there and eventually sold as surplus. Pure speculation on my part. Mare Island was turned over to the city of Vallejo in the 90's. There is a lot of history there. It was the Navy's first sea port on the west coast. "
Posted November 15, 2013