Regenerative kit identified -Burstein Applebee (and also "Archer Globe Patrol" from Radio Shack)

Regenerative kit identified
Burstein Applebee (and also "Archer Globe Patrol" from Radio Shack)

Three tubes, four bands, six controls

 regenerative receiver kit

This regenerative receiver is apparently quite rare. It had no manufacturer name or model number on it. The set is four band with broadcast and three shortwave ranges. Tubes are 35W4 as rectifier, 50C5 for audio output and a 12AV7 dual triode as the regenerative RF detector and audio preamp. The radio has screw terminals for antenna and ground, a front-panel phone jack for headphones, and a pilot light. The circuit is completely identical to the Lafayette KT-135 with the exception of the pilot light which the KT-135 does not have. The front panel is larger than that of the KT-135 and the layout is different. It has the phone jack on the front rather than on the back of the chassis.

So who made it?
Since the Lafayette KT-135 and this kit have identical circuitry, that leaves the question of who may have supplied the kit. Most of the components inside this kit appear to be American made although the three tubes are all "Perma Test" brand, Made in Japan with a code of "III 443". The Lafayette ads for the KT-135 clearly specify "Made in USA", so I assume a company in the USA supplied both but which company? I believe the front panel was purposely designed so as to NOT look like the Lafayette. Let me know if you also have one.

To my query, Carl S. supplied me with a picture of the front of the manual. This particular one was sold by Burstein Applebee but had no front panel markings identifying Burstein-Applebee. The proof was the manual cover page which showed the radio without the identifying logo.

Also sold by Radio Shack
The set was also identified by Don WA1KVK as an Archer Globe Patrol sold by Radio Shack. Don notes that, "this radio provided a start for my twin brother and I to get into Ham Radio and helped kickstart our careers in electronics!" Here is a picture of the one he built in 5th or 6th grade in about 1964.

 Archer Globe Patrol logo

Archer Globe Patrol 3 tube regen

Since Don's identification, I found another picture of this Globe Patrol on the web.

Archer Globe Patrol 3 tube regen

Previous update 9-17-12
The set was earlier correctly identified by two folks as coming from Burstein-Applebee. However, there were some questions. Here is a Burstein-Applebee version in their 1967 catalog. (Thanks to Scott WA9WFA for this catalog picture).

Burstein-Applebee 1967 catalog pic

The Burstein-Applebee set shown in the catalog has some variation in the height of the tuning controls and the shape of the speaker grille. There is also no pilot light. Note the BA logo on the catalog picture. According to Tom Dailey W0EAJ, who worked at the company for a number of years, as well as his co-workers, Burstein-Applebee always put their logo on their products. Tom mentioned that it was an "ego thing with Jerry Burstein". Tom also said, "The BA part-number... 32B26, indicated it is a "repurchase" from another entity - and the cabinet ... was BA p/n 32B27."

I suspect that the Burstein-Applebee model in the catalog was a very similar but somewhat later version of the one shown here.

The Radio Shack kit and this Burstein-Applebee model have an identical circuit to the Lafayette KT-135. All three kits were likely supplied by the same manufacturer headquartered in New York. Strong indications suggest that manufacturer was the Accurate Instrument Co. which also supplied a Signal Tracer/ Generator to Lafayette and to other catalog distributors under their respective names.

Regenerative circuits
Regenerative circuits, discovered by Edwin Armstrong, date back to the very beginning of vacuum tube radios. The circuit for this set is similar to the Knight Space Spanner and the Heathkit GR-81 except for its regeneration control. Instead of varying the total voltage on the plate of the regenerative triode by way of a 100,000 ohm potentiometer, the Lafayette circuit uses a much smaller 500 ohm variable resistor. The triode plate is fed by two paths for its voltage. One path is direct from the B+ source. The other path is through the coil feedback winding. The relatively small variable resistor acts as a variable short circuit to the RF energy in the feedback winding path. The feedback winding is traditionally called a "tickler" winding. Too much regeneration is a bit like holding a microphone too close to a public address system speaker, resulting in a squeal of positive feedback. The same effect occurs at radio frequencies, but just prior to the squeal, the regenerative circuit has tremendous amplification and narrow bandwidth.

Six controls
This receiver has six controls, three of which are variable capacitors. Those capacitors all interact. The largest variable capacitor on the left side sets the approximate tuning range. The smaller bandspread cap in the center tunes a portion of that range. A smaller variable cap on the lower left is used as the antenna trimmer. The band-select switch, the regeneration control and the volume control with power switch make up the remaining controls.

AC-DC power supply
The power supply is transformerless AC-DC using one side of the power line as floating B- with two 0.05 MFD capacitors and a 100K ohm resistor between the power line B- and the chassis. That introduces some safety concerns although the floating B- is a lot safer design than directly placing the chassis at B-. Since the set was in excellent cosmetic and working condition after repairs, I did not want to modify the set beyond a simple safety improvement, polarizing the power cord. Use of an isolation transformer or GFCI outlet is strongly recommended when using this set.

All the caps in this set are ceramic except one. I replaced that cap, a color striped Sprague "Black Beauty" located across the power supply. That capacitor type is now often called black ugly because it is prone to failure. To my surprise the cap was in good condition. I will save it for someone insisting on using it in a tone circuit in a guitar amp where the cap will not see serious voltage and the possibility of a bit of leakage will not affect the circuitry. I also replaced the 47K ohm resistor from B+ to the regeneration control because it had drifted high.

The biggest problem with the set turned out to be a bandswitch with poor contacts. The switch is plastic-sealed. I had to thoroughly coat the back side of the switch with deoxit and place the radio on its face, letting gravity help overnight.

I used the Lafayette KT-135 schematic and kit building manual. Lafayette has both a schematic and a pictorial in the manual but they do not match for the regeneration control connections. The schematic shows connections at all three terminals as a potentiometer while the pictorial shows only two connections as a rheostat. I tried it both ways. Reception results were about the same. I left the set with the rheostat two terminal connection as found and as indicated in Lafayette's kit building instructions.

One of the advantages of these simple regenerative sets is they have no alignment needs. However, since the band coils are not adjustable and the variable caps including the antenna trimmer interact with each other in tuning, the dial setting frequency at which the set is tuned is a rough guess at best.

Homebrew cabinet
Like the Lafayette KT-135, a vinyl covered cabinet for this set was sold separately. The beautiful cabinet for this set is home brew. The quality of the woodwork is excellent.

Playing with it
Listening to short wave with a minimalist regenerative set is a fun experience for me. Such simple sets introduced many to the wonders of radio which may explain the continuing appeal and demand for these sets. Experience and a skilled hand are required to bring out its full capabilities, but that's part of the fun.

The next generation of Radio Shack's "Globe Patrol"
Radio Shack introduced a transistorized regenerative kit called the Science Fair "Globe Patrol" shown at this link.

Schematics and further information
As stated, the Lafayette KT-135 is the identical circuit. The schematic and all of the instructions for that set apply to this one as well. The Lafayette manual is available online. Click here for the KT-135 manual from BAMA in djvu format.
A better quality pdf version of the KT-135 manual is available from this source.

More regenerative radios
Click on this link to go to a list of all the regenerative radios on this website

Date 8-18-12, updated: 8-27-12, 9-17-12, 10-18-12, 2-5-13, 9-22-14

The National Schools AM/SW radio kit was the previous item on the bench.

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