Archive for the ‘Radio Frequency’ Category:

2018-12-09 Selectivity V. Sensitivity

from FB group Building Transistor Radios 2016 Dec 9 Jim Glover An ideal receiver would have a bandpass shaped like a square wave where the bandpass is flat with no attenuation and the attenuation is infinite outside of the passband. In the real world this isn’t possible but any receiver buyer with the money would

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2018 Dec 8 Sinclair Book 22 Tested Circuits Using Micro Alloy Transistors

from FB group Building Transistor Radios 2018 Dec 8 Nick Bastian posted the schematic of a Sinclair Micromatic radio. I found the book by Clive Sinclair about the circuits using micro alloy transistors. Germanium transistors and especially micro alloy transistors are no longer made so it’s better to use silicon BJTs instead. Here is the

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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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2018-11-19 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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2018-11-13 PSI Pacific Semiconductors Inc.

from FB group Building Transistor Radios 2018-11-16 The guy I worked for got us some Pacific Semiconductor power transistors for use in aircraft radios. That was before they were bought out. The logo on them was the Greek letter Psi. I think I might still have one in my old parts drawers. PSI was one

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2018-11-07 The 2 Transistor Boy’s Radios

from FB group Building Transistor Radios 2018 Nov 7 I bought some 10 uF, 10 volt MLCC (multilayer ceramic capacitor) capacitors, which do not have the electrolyte so they can’t dry out. They are smaller, too. If they are used for replacements, then radios might last much longer. About the only thing left to go

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2018-10-29 Early Transistor Radios And LW Band

from FB group Vintage Transistor Radios 2018-10-29 One may find that some early transistor radios, along with AM, had Long Wave band before they had SW or FM. We should keep in mind that earlier germanium junction transistors had a maximum frequency that was limited to 2 to 4 MHz. The radios could have a

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2018-10-18 Admirable Admiral Radio

from FB group Vintage Transistor Radios 2018-10-20 Was it made in the late ’50s? The transistors are early RCA types. These old time radios are about 60 years old and I am amazed and inspired to hear and see that, once the caps have been replaced, they perform as well as the day they were

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