Re: Variable Capacitance and Inductance

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "rheidlebaugh by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rheidlebaugh-at-zialink-dot-com>

Ed/Matt : as I havs seen many changes in equipment through the years
Including the use of the COLPITS RC only oscilator for stability to the
current crystal controled systems of the lap top computer time base.
Frequency drift is and has been a problem for all physicly constructed
systems in electronics. An engineer designs a system, but a tech re works it
to make it work in the real world. There is no resonant circuit made that is
not affected by its enviorment including crystals. It is not reasonable to
think an open coil like a TC would not be subject to every change around it
including sun, moon, weather , and a mad wife.
   Robert  H       ( get off that list and talk to me!!)

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Fri, 24 May 2002 19:16:01 -0600
> To: tesla-at-pupman-dot-com
> Subject: Re: Variable Capacitance and Inductance
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Fri, 24 May 2002 19:32:39 -0600
> 
> Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <evp-at-pacbell-dot-net>
> 
> Tesla list wrote:
>> 
>> Original poster: "David Thomson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
>> 
>> Hi Matt,
>> 
>>> The vast majority of  receivers in the world don't use crystals for the
>> local oscillators. The commercial transmitters that use them and the tiny
>> number of military receivers that do, keep them in temperature-controlled
>> environments, because even a crystal's frequency IS temperature sensitive
>> (drift).
>> 
>> Every military radio I have sold (about 100 in the past year) had crystals
>> in them.  I haven't heard of a military radio without crystals.
> 
> I have, and own a operate a few.  The Navy ARC-5 and its USAAF
> counterparts were excellent gear and plenty stable enough for general
> use.  The infamous BC-375 was an antiquated transmitter used in almost
> all US bombers during the war, although as one guy put it "it was made
> mainly to be shot down in bombers".  Some equipments, like the Collins
> line, were exceptionally stable and probably still in use; certainly
> their use persisted long after the war and hams such as I still have
> them as part of their operating equipment.  Crystal-controlled receivers
> and the accompanying transmitters came into military use during WW2, as
> they could be used by inexperienced or incompetent operators.  The vast
> majority of HF transmitters and receivers were not crystal controlled,
> and the use in radios and TV's began only in the late 70's and early
> 80's, when inexpensive synthesizers came into use.
> 
> "VFO's" for frequency control are still used in ham radio gear and
> inexpensive short-wave receivers, although crystal-controlled
> synthesizers are becoming so cheap that they are used almost exclusively
> in top-end equipment.
> 
> 
>> 
>> As I mentioned to Dave P., the inductance used in the oscillators of radios
>> is far smaller than the inductance used in Tesla's coils.  And most
>> inductances in radio antennas that I know of use ferrite cores, which help
>> to stabilize the inductance.  In older radio oscillators most of the
>> oscillator inductance is in the wires between the vacuum tubes, and the
>> oscillations are maintained mostly with RC circuits.
> 
> Incorrect.  For example, I have a Navy RBL receiver built during WW2
> (the design was older) which uses inductors with inductance as high as
> as 50 millihenries and more, which is well within the range of some of
> the larger coils.  The RF input coil to almost all broadcast receivers
> had an inductance of about 330 microhenries, etc. etc.  Only very high
> frequency receivers depended on the inductance "in the wires" for
> tuning, and only very shoddy ones.  RC circuits were never used, to my
> knowledge; if they were they certainly aren't mentioned in any of the
> radio text or hand books.
>> 
>> In radios using only air core inductors in the antenna circuit, constant
>> tuning is necessary throughout the day.  Dave P. mentioned he turned on the
>> radio to one station, and the next day the same station was there with no
>> drift.  This is not surprising.  To check for radio drift according to the
>> diurnal effect Tesla mentioned one would have to monitor the same radio
>> station throughout an entire 24 hour period to notice any drift.
>> 
>> I have 4 old AM tube radios.  The stations come in fine during the day but
>> just after the sun sets and just before it rises the radio stations drift
>> considerably.
> 
> As has been pointed out already, that is due to changes in ionospheric
> propagation, not frequency drift.  The effect was observed as early as
> Marconi's 1904 transatlantic effect.  Long-distance sky wave propagation
> is the primary mode for short-wave communication and broadcasting, with
> the appropriate frequencies changing with time of day and year (affects
> the angle with which the sun's radiation strikes the ionosphere) and
> solar conditions which can vary the particle flux striking the earth.
> There was a major disturbance yesterday morning, for example.
> 
>> I know stranger things have happened.  Ham operators tell me strange stories
>> all the time.  
> 
> I've been a ham for well over half a century and hams operators have
> told me many strange stories.  A few of them have even been true, but
> readily explained by known laws of nature.
> 
>> But there is no doubt that the earth's position with respect
>> to the sun can alter circuitry such that there are frequency changes.
> 
> You and Tesla appear to be the ONLY ones who have ever observed such
> alteration in the circuitry due to solar influences other than direct
> heating!
> 
>> And
>> if frequency changes, that can only mean the inductance and or capacitance
>> have changed (in a LC resonant circuit.)
>> 
>> Dave
> 
> If the frequency did indeed change, that would be the reason.  No
> evidence whatever that it changes at all!
> 
> Ed
> 
> 
>