William Haywood Jones

There have been many ways to control the gain of radios over the years and will discuss several of the important ways starting close to the beginning of the AC radio.  While I may not cover all of the ways used for control but will cover the important ways and will discuss some of the reasons for their use.I plan to cover the 1920’s to at least to the present day volume control plus AGC (Automatic Gain Control) gain control – this would be the last of the tube radios. I plan to provide a simple but accurate analysis of the automatic gain control.  Another proper name for AGC is AVC, or Automatic Volume Control, but here we will generally use the term Automatic Gain Control. To be accurate I believe that the term Automatic Volume Control is a more proper name if you are interested in marketing. I tend to use th?e term AGC, but the terms are used interchangeably.  I have never seen the AGC analyzed before. The analysis can be very tedious without some simplifying assumptions. I have made

Variable Capacitor Analysis   Bill Jones The capacitor to be analyzed is shown in Figure one. It is desired to find the capacitance C (A+B) and how it varies with respect to d.                                                                         Figure one shows two capacitors. For our analysis they will be connected in parallel.  The stators are separated by a distance x and the distance d is from stator A to the rotor. We are interested in the total capacitance C (A+B). The rotor thickness is negligible for our purpose. We normalize for simplicity.          A=area in cm. squared. K=1 (dielectric constant).  d=distance in cm.  C in pf.      We set x=1 and P=1 for simplicity since we are not interested in the absolute value. This will give equation2. A plot of the equation is shown in Figure 2.  If we imagine the rotor plate to be perfectly centered at d=0.5, the capacitance is a minimum value.  If d varies in either direction from d=0.5 the capacitance increas

Signal Generators The H.P. 606 and the Hickok 288X By Bill Jones This paper is not meant to suggest that the HP 606 and the Hickok 288x are in any way equivalent generators.  The HP was a modern laboratory generator in its day.  It is mostly a tube type generator - it used miniature tubes. It was never meant for radio service. It was expensive and its features were not necessary for any radio repair shop. Today however the HP is available at a moderate cost and offers those interested in radio repair and Amateur Radio work a bargain generator.  I find it quite useful and even a joy to use because of its known frequency and signal level outputs.  It is simple and straight forward to use.   The Hickok generator was really meant for radio repair and in its time it was a desirable generator for the radio shop and not an inexpensive generator. The Hickok is today and perhaps has always been a misunderstood generator because of its complex design.  It was cleverly designed.

The RCA Battery Voltohmyst .. RCA WV-65A THE RCA VOLTOHMYST WV-65A VACUUM TUBE VOLTMETER WAS PROBABLY MANUFACTURED IN THE MID TO LATE FORTIES. THE RCA WV-65A VOLTOHMST IS MENTIONED IN AN ARTICLE FROM THE RCA “HAM TIPS” IN JULY 1949.  THERE ARE VIDEOS REGARDING THE METER ON THE INTERNET.   THIS IS AN UNUSUAL AND RARE VACUUM TUBE VOLT METER BEING BATTERY OPERATED.  IT IS PERFECT FOR RADIO REPAIR. THE METER MAY HAVE BEEN ORIGINALLY MARKETED TO “HAM” RADIO OPERATORS.   AS WITH ALL THE VACUUM TUBE METERS BUILT BY RCA THE WV-65A HAS THE USUAL ONE MEGOHM RESISTOR IN THE PROBE. THIS ALLOWS DC MEASURMENTS TO BE MADE ON A RADIO WITHOUT INTERFERING WITH THE RADIO OPERATION.  THE PROBE WILL NOT ALTER THE AUTOMATIC GAIN CONTROL VOLTAGE AND WILL NOT KILL THE OSCILLATOR WHEN MEASURING THE OSCILLATOR NEGATIVE GRID VOLTAGE.   THE WV-65A LOOKS LIKE THE RCA 195 VOLTOHMYST AND HAS A BRUSHED CHROME FRONT PANEL LIKE MOST OF THE 195’S. IT HAS A DC CURRENT SCALE WHILE THE RCA 195 VOLTOHMYST DOES NOT.

Arvin Radios ~ Bill Jones While there is no shortage of Arvin’s, a particular model may, at times, be difficult to find. I have been looking for an Arvin 422 for some time and finally found a cream colored one. I did not care if it was brown or cream since I plan to restore one of each. The brown is the 422 and the cream (Ivory?) is the 422A. The electronics are much the same for all of the four tube Arvin’s, but there are minor changes. The 422 that I just restored had the I.F. transformer on the underside of the chassis and the transformer was not shielded. Most four tube Arvin’s that I have seen have had the I.F. on the upper chassis with shield. In restoring the chassis of this Arvin I found an oscillation at the low end of the dial. I have noted this type of oscillation before with other radios. I paid little attention since it is removed by a slight detuning of the I.F. While checking this Arvin I began to wonder why this was happening. The oscillation was of a type