Archive for November, 2018:

2018-11-29 Fixing Badly Worn Volume Controls

from FB group Building Transistor Radios 2018-11-30 I’ve done some experimenting on volume controls that are badly worn and noisy. The idea is to substitute some resistance for the badly worn spot. The loud crackling will be reduced and the normal volume point will be moved to a higher point on the control. For a

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2018-11-26 Two 6 uH RF Chokes

from FB group Building Transistor Radios 2018-11-26 https://archive.org/stream/ETIA1983/ETI%25201983-03%2520March_djvu.txt Two 6 uH RF chokes The photo shows two different RF chokes, each about 6.4 microhenrys. The one on the left is a ferrite bead, made by Fair-Rite, Cat. # 2643000801. These were about 12 cents apiece from Mouser.com. Yes, the wire passes through the small hole

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2018-11-25 One Transistor FM Receiver Schematic Part 1

From FB group Building Transistor Radios Larry Daniel 2018-11-26 This is the original schematic posted by Larry. GM is a gimmick capacitor made of two short lengths of solid hookup wire, twisted together for a few pF capacitance. List of RF Chokes for the ham bands Larry said he used an RCA SK1008, then corrected

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2018-11-24 The Rise Of The PCs

from FB group Vintage Transistor Radios 2018-11-24 Early on, I built and upgraded many PCs when they became popular. Some for myself and friends, but most at work. Before that I was maintaining and repairing terminals and other equipment attached to mainframe computers. It started out small with TRS-80s and Apples but really took off

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2018-11-22 Homemade 9 pF Gimmick Capacitor

Also posted to FB group Building Transistor Radios Watson’s 9 picofarad homemade “gimmick” capacitor This homemade capacitor can be used for circuits were the capacitance is not critical, such as a wireless microphone for the FM broadcast band. The wire can be obtained from the cable used to connect telephone outlets. Solid (not stranded) plastic

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2018-11-20 Solder V. IDC Punchdown

from FB group Bell Telephone… 2018-11-22 Happy Turkey day! I use solder all the time, and I trust it as long as it’s done properly. But one thing I learned in my decades of telephone work is that the wiring systems the telcos developed were tested and proven before they were deployed, and they were

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2018-11-19 Depth of Loop Antenna

from FB group Building Transistor Radios 2018-11-19 I shared my loop antenna – see photo, and it is somewhat 2 dimensional. The arms are 762mm across but the depth of the windings is only about 35 mm. Compare that to the ferrite loopstick at the other extreme, it’s 10 mm diameter but 100 mm long.

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2018-11-17 Cause Of Bleedover From Radio Stations

from FB group Building Transistor Radios 2018-11-19 IMPORTANT I used to work for a guy who did radio engineering and would troubleshoot problems such as this ‘bleedover’. For convenience some radio stations colocate their transmitters near or at the same site. Because the signal strengths are very high, the two stations can cross modulate their

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2018-11-16 Low ESR MLCCs

From FB group Building Transistor Radios 2018-11-19 Garry Heard I’ve found that a problem with using electrolytic capacitors to filter out the RF noise is their internal ESR, effective series resistance. They don’t filter out the RFI as good as they should. I found that MLCCs do a better job, if I used some multi

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2018-11-15 ESD and Weather

from FB group Building Transistor Radios 2018-11-19 Bob Johansen I worked at a company that had ESD mats on the workbenches, about 1980. We had wrist straps with a 1 Meg resistor in series with the cord to prevent shock hazard. I found that the leads of the resistors were broken but the heat shrink

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