Airplanes and Rockets' history & copyright Google search American Modeler Air Trails American Aircraft Modeler Young Men Hobbies Aviation Flying Aces Saturday Evening Post Boys' Life Hobby Distributors Amateur Astronomy Engines & Motors Balsa Densities Silkspan Covering Comics Electronics My Models Model Aircraft Articles Plans Model Boat Articles Plans Model Car Articles Plans Model Train Articles Plans 1941 Crosley 03CB Radio Model helicopter articles & plans Crosswords Model Rocket Articles Plans Restoration Projects Photos Peanuts Collection Model Aircraft Articles Plans Sitemap Homepage Hints and Kinks Amateur Radio Archives of the homepage R/C Modeler Electronics About Airpleans and Rockest, Disclaimer, Terms of Use Model Topics Please Donate to Airplanes and Rockets Parole Plaza, Annapolis, Maryland Hobby Items for Sale Airplanes and Rockets Hero Graphic
Plastic Scale Model Kits - Airplanes and Rockets

Model Aircraft Museum, AMA - Airplanes and Rockets

Rocket Kits + Accessories - Airplanes and Rockets
Drones - Airplanes and Rockets

Sensitive Field Strength Meter
May 1954 Model Airplane News

May 1954 Model Airplane News

May 1954 Model Airplane News - Airplanes and RocketsTable of Contents

These pages from vintage modeling magazines like Flying Aces, Air Trails, American Modeler, American Aircraft Modeler, Young Men, Flying Models, Model Airplane News, R/C Modeler, captured the era. All copyrights acknowledged.

It was six years prior to this field strength meter construction article being published that Mssrs. Brattain, Shockley, and Bardeen invented the transistor using the element germanium and a point contact "cat's whisker." In 1954, the date of this article,  Texas Instruments introduced the first commercially available silicon device - the TI 900 silicon transistor. However, operational frequencies of semiconductors were only in the hundreds of kilohertz, so vacuum tubes were still necessary in higher frequency radio circuits like the field strength meter, which operates in the 30 MHz band. Sylvania 1AD4 Miniature Vacuum Tube (eBay photo) - Airplanes and RocketsFortunately, by the mid 1950s there was host of miniature tubes available for use that reduced that physical size and weight and also often worked on lower plate voltages and lower currents so that power requirements were reduced as well. The 1AD4 RF/IF pentode is used in this field strength meter to increase its sensitivity over the passive diode type detector.

Sensitive Field Strength Meter

Your finished field strength meter will look like this - Airplanes and Rockets

Your finished field strength meter will look like this. Uses various available meters.

Pot enables voltage adjustment - Airplanes and Rockets

Pot enables voltage adjustment according to the value of the meter used.

Rear view of field strength meter showing placement of component parts - Airplanes and Rockets

Rear view of field strength meter showing placement of component parts. Batteries at the bottom.

By E. J. Lorenz

Are you really sure your transmitter is putting out? Here's a simple unit for accurate checking.

Range, range, range!

You just don't have it unless your transmitter is properly tuned and the antenna is properly loaded. We have flown excellent flights with our two-tuber using a half-watt transmitter.

In order to obtain the greatest efficiency from your transmitter, we are presenting a simple field strength meter. Perhaps you are using one which consists of a half or full wave diode circuit. This type of meter registers well at close range but has the disadvantage of low sensitivity and the need for a sensitive meter, usually 0-1 ma or less. The described field strength meter employs a sub-miniature 1AD4 RF pentode in a grid leak detector circuit, and uses a 0-3 ma meter, one that every RC modeler has on his bench.

This will not be a full-fledged construction article, for space does not permit, but the schematic diagram plus photographs should be sufficient. In addition, this circuit has been built with a variety of components, such as air trimmers and ceramic trimmers, air coils and slug-tuned coils, and tubes including the 1AD4, IAG4, CK5607, RK-61, XFG-1, CK525, and CK5677. Meters have ranged from 0-1 to 0-5. Results have been similar in all cases. Your unit may be built into almost any size case that will suit the construction; we used a 3006 mini-box.

As far as construction is concerned, keep all leads as short as possible; this is not imperative but always advisable. The B voltage may range from 15 to 45 volts depending upon the value of meter used. When using an 0-1 ma meter, 15 volts are sufficient, and 45 volts will operate a 0-5 meter. Since the unit is on but a short time, we soldered the batteries and A cell in place.

To use the meter, when finished and in its case, switch on the unit and adjust the pot R2 to read about half-scale on the meter. Insert a 12-18 in. antenna (a thin piece of wire soldered to a banana plug) in its socket and rotate the tuning capacitor, or slug, until the maximum dip is obtained on the meter. Remember this: a field strength meter gives only relative readings at a given distance from the transmitter. In other words, if the unit is held by someone, the dip will be greater than if the unit is placed on a box or bench. Once properly tuned, remove it from the vicinity of the transmitter until a .2-.5 ma dip is obtained when a signal is transmitted. Leave the field strength meter in one position and adjust final tank capacitor or antenna loading until the maximum dip is obtained. Be sure the field strength meter antenna and the transmitter antenna are in the same plane; that is, vertical to verrical and horizontal to horizontal. Greatest accuracy is achieved at a distance of at least one wave length away from the transmitter, or about 40 ft.

Field Strength Meter schematic - Airplanes and Rockets










Posted March 1, 2014

Plastic Scale Model Kits - Airplanes and Rockets

About Airplanes & Rockets 

Kirt Blattenberger, Webmaster - Airplanes and RocketsKirt Blattenberger

Carpe Diem! (Seize the Day!)

Even during the busiest times of my life I have endeavored to maintain some form of model building activity. This site has been created to help me chronicle my journey through a lifelong involvement in model aviation, which all began in Mayo, MD ...

Copyright  1996 - 2026
All trademarks, copyrights, patents, and other rights of ownership to images and text used on the Airplanes and Rockets website are hereby acknowledged.

Homepage Archives  |  Modeling News Archives


Kirt Blattenberger


Family Websites:

RF Cafe

Equine Kingdom

Drones - Airplanes and Rockets

Academy of Model Aeronautics (AMA) - Airplanes and Rockets

Academy of Model Aeronautics

Tower Hobbies logo - Airplanes and Rockets

Tower Hobbies

Horizon Hobby logo - Airplanes and Rockets

Horizon Hobby

Sig Manufacturing - Airplanes and Rockets

Sig Mfg

Brodak Manufacturing - Airplanes and Rockets

Brodak Mfg