Archive for the ‘Radio Frequency’ Category:

2020-06-18 Michael Pupin & Patents

From the list of his patents in his wiki. Armstrong co-authored some patents. https://www.google.com/patents/US1416061

2020-06-08 Military Intelligence Is A Joke

From FB comment Jun 8 Gayle McGowen Nobbs 🙄🙄 “Military intelligence is an oxymoron.” I was stationed in the Army nike site in Minneapolis. We had to keep the buttons with the secret words for the Radar’s switches in a locked safe. The very same buttons with Lin-Log, Integrator, Dicke Fix, etc. were on the

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2020-05-28 Solid State Shortwave RF Preselector

Comment left 2020 May 29 on YouTube video in the title. This video covers MOSFET, dual gate MOSFET, JFET and BJT tuned preamps (preselectors) for his shortwave crystal radio. “The talk about using 18 volts for the cascode got me thinking about tube designs. When the plates need 100+V, and when the heater to cathode

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2020-05-22 PIM Passive InterModulation Explained

Good article on passive intermodulation, AKA the Rusty Bolt Effect. https://www.electronics-notes.com/articles/radio/passive-intermodulation-pim/what-is-pim-basics-primer.php

2020-03-31 Collecting Novelty Transistor Radios

Also FB group Vintage Transistor Radios Collecting novelty transistor radios has a few drawbacks, the most obvious is that they are much rarer than regular transistor radios. Generally the new novelty transistor radios are much more expensive then a regular radio due to their limited production. The customer who just wants a radio is going

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2020-03-29 AM Osc + Modulation + Buffer

This is from Electronics Illustrated Projects 1968. It shows crystal sockets, but instead a RF coil may be used and its value will be about 220 microhenrys. And C1 and C2 will have to be changed to bring the frequency down to the AM band. The germanium transistors are no longer available so silicon transistors

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2020-03-10 Simple AM Band Antenna Tuning Coil 240 Microhenrys

The standard ferrite antenna loopstick for a 365 pF tuning capacitor has an inductance of about 230 microhenrys. This in combination with the tuning capacitor tunes across the full AM broadcast band. It’s useful to be able to wind your own inductor so it can be used for an antenna coil, a trap to attenuate

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2020-02-19 Nobility 15 transistor Radio Repair

2020 Feb 18 – Nobility 15 transistors OTL S/N (?J)29549 I replaced the electrolytic capacitors. The spkr buzzed when I touched the volume control. Nothing from the detector (transistor). It’s unusual. I pulled and tested some IF parts including one of the transistors, no problems found – transistor tested good. I called it a night.

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2020-02-17 I Bid On A Boy’s Radio, Lost

From FB group Vintage Transistor Radios Last week I bid on a boy’s radio, $26 which lasted up until near the end. But as usual I was outbid at the last minute. I think the demand exceeds the supply, and the prices go up too high. Looks like I’ll be getting one that no one

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2020-02-14 Zenith Royal 400 S/N Z551549 Replaced Capacitors, Driver Transformer

Zenith Royal 400 s/n Z551549 I soldered broken orange wire to battery holder. Replaced all four electrolytic capacitors. Silent speaker and nothing from earphone jack. I checked the voltage at the collector of the driver transistor, it was zero. One pin of the driver transformer primary measures 5.8 V, the other pin measured 0. Checked,

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