Amateur Observations During the Total Eclipse of the Sun
January 1933, QST
Amateur radio operators, as with hobbyist participants in many other realms, historically have contributed significantly to the efforts of their professional counterparts. I have written of it often. This particular instance is where signal measurements in the Ham bands during a total eclipse of the sun were used to assist scientists debating the merits of rival theories relating to origin of ionization in the Kennelly-Heavyside Layers of the E and F regions, both of which were proposed in 1902 (yes, the Heaviside of step function fame). Long distance (DX) communications are dependent upon such ionization to reflect radio signals that would otherwise pass through the atmosphere and into space. The test at hand would settle the argument since the one should fail if ionization was unaffected during totality. Read the article (or skip to the end) to discover which gentleman's theory won the day.
January 1933 QST
Wax nostalgic about and learn from the history of early electronics. See articles
QST, published December 1915 - present. All copyrights hereby acknowledged.
Amateur Observations During the Total Eclipse of the SunBy R.W. Woodward, W1EAO
The total eclipse of the sun on August 31, 1932, afforded a wonderful opportunity for the radio amateur to contribute to our scientific knowledge of short-wave transmission phenomena, and more particularly to obtain information which would lend support to one or the other of two rival theories concerning the origin of the Kennelly-Heavyside Layers.
EQUIPMENT USED AT THE CASE SCHOOL OF APPLIED SCIENCE, CLEVELAND, FOR GRAPHICAL RECORDING OF THE SIGNALS OF W1EKL
The output of the receiver was fed though a vacuum tube voltmeter to the standard Leeds and Northrup recorder with paper speed stepped up to record rapid variations. This work was under the direction of J. R. Martin, Assistant Professor of Electrical Communications. assisted by W. E. Slabaugh, W8CIM. and L. W. Fraser. W8DGP. Thanks are due to MT. Fraser for this information, including the photographs and copy of the recording shown in Fig. 6.
One theory supposes that the ionization of the reflecting layers (both the so-called E and F layers) in the upper atmosphere is caused, for the most part, by ultra-violet light from the sun. The other theory holds that the ionization of the lower, or E layer, is produced by neutral particles or corpuscles streaming from the sun at a rate of a thousand miles per second. If the first theory is tenable, any effect on radio transmission during the eclipse should correspond approximately with the time of the visible eclipse. On the other hand, if the corpuscular theory is acceptable, the effect on radio propagation should precede the visible eclipse by some two hours due to the slower velocities of the corpuscles coming from the sun as compared to the speed of light. Whereas the visible total eclipse cut a swath only about 100 miles wide across a part of New England and eastern Canada, the "corpuscular eclipse" would be maximum on a path starting from Spitzbergen, through Greenland, the mid-Atlantic Ocean, and ending at lower Spain. It would cover a path about 1600 miles wide, not touching the United States.
Equipment used at the Case School of Applied Science, Cleveland, for graphical recording of the signals of W1EKL. The output of the receiver was fed through a vacuum-tube voltmeter to the standard Leeds and Northrup recorder with paper speed stepped up to record rapid variations. This work was under the direction of J.R. Martin, Assistant Professor of Electrical Communications, assisted by W.E. Slabaugh, W8CIM, and L.W. Fraser. W8DGP. Thanks are due to Mr. Fraser for this information, including the photographs and copy of the recording shown in Fig. 6.
As requested in QST, by Official Broadcasts and by letter to Official Observers, a great many A.R.R.L. members all over the country and in some European countries sent in reports to head-quarters on their observations during the eclipse. Particular attention was directed to the transmissions of W1EKL, a portable station located at Douglas Hill, Maine, in the path of totality by a party from the Warner & Swasey Observatory of Cleveland, Ohio. Prior announcements indicated that this station would transmit c.w. on 3550 or 7100 kc. between the hours of 1400 G.C.T. (9 a.m. E.S.T.) and 2300 G.C.T. (6 p.m. E.S.T.), but implied that the 80-meter (3550-kc.) wave would be used. Observations on intensity of received signals, preferably by means of a suitable output meter, throughout the entire period were desired. On the day before the eclipse it was determined that the 80-meter signal was not strong enough for automatic recording in Cleveland, so that it was necessary to use a frequency in the 40-meter band. Actually during the eclipse transmission a frequency of 7150 kc. was used. Because of this change in the frequency practically no reports on reception of W1EKL were received at headquarters as many of the reports indicated that watch was kept for W1EKL on 80 meters. Also because of skip distance the station on 40 meters could not be heard in the eastern part of the U.S.A. It is understood, however, that very satisfactory automatic records were obtained in Cleveland and also that many reports of reception were received direct by W1EKL.
Possibly also many of the eastern observers did as the writer, who, after spending several days arranging equipment to take intensity measurements during the eclipse, and in spite of rain at the time, hopped in the car a few hours before the eclipse and drove to Maine for a ring-side seat. At any rate, many A.R.R.L. emblems were seen on the road.
W1BZI operated by F.S. Huddy at Chepachet, R.I., where the eclipse was 98% total, made special eclipse transmissions on 3896 kc. between 1900 G.C.T. and 2100 G.C.T. (2 and 4 p.m. E.S.T.) and was reported by many observers, several of whom gave very complete readings from vacuum-tube voltmeters in the output of receivers. Some submitted reports from privately arranged schedules, others of reception of commercial stations, and still others logs of scattered reception of many stations on the air at the time. The data included results on the 5-, 20-, 40-, 50-, and 160-meter amateur bands, broadcast band, and long wave commercial. Several also submitted interesting data on accompanying phenomena such as static conditions, atmospheric pressure, temperature, clouds, wind, and light intensity.
In spite of the request to take observations throughout the day, the majority failed to do so, reporting only for a short period before totality and a still shorter period after totality. This was important not only from the standpoint of testing the "corpuscular" theory, but also, particularly on 20 meters where longer distances were involved, the time of the maximum of the eclipse was quite different in the several sections of the country. Thus the maximum of 38% totality occurred in Seattle, Wash., at 1927 G.C.T. (2:27 p.m. E.S.T., 11:27 a.m. P.S.T.), at Tallahassee, Fla., the maximum of 68% was at 2047 G.C.T. (3:47 p.m. E.S.T.), while the time of totality in New England was approximately 2030 G.C.T. (3:30 p.m. E.S.T.).
The following contributed reports on their results to headquarters:
W1 - AFC, AGA, APK, ASP, ATW, AZQ, BBM, CTG, DGC, DIJ, MX, ST, VF; W2 - BJZ, EB; W3 - AAJ, AXJ, CL, DZ, QL; W4 - ADA, AJS, AYF, PM; W5 - AAQ, ARJ; W6 - DLV, RJ; W8 - AJ, AJK, ATN, CBF, DED; W9 - ABS, AKJ, AN, AOG, BN, EGE, EQW, FMX, RS, Chas. E. Dewey, Jr.; VE4EL; F8RJ; G2JA at sea on S.S. Rangitiki; ON4AU.
The reports received showed that the following stations were heard during the eclipse period, many transmitting special test signals. A great many reports did not list individual stations but classified their results by districts so that no doubt hundreds of additional stations also contributed to the results.
W1 - ABM, ABY, ADN, AHK, AKI, APJ, APK, AT, AVK, AYR, BBT, BCD, BDW, BIC, BGY, BTZ, BWP, BXC, BZB, BZD, BZI, CAC, CBJ, CKT, CKU, CLH, CMX, CNC, CPC, CPT, CVJ, CVR, CYN, DIJ, DZF, EKL, FH, GB, HE, HI, JJ, MX, SI, ST, SZ, ZC; W2 - ABT, AHE, AIS, AWF, BHZ, BJV, BOT, BPV, BRO, BTZ, CJM, COJ, COK, DNG, DTO, DZ, GO, GT, NV, ZC, ZT; W3 - AGI, ANA, AO, AQI, AQR, AUA, AXR, AZC, BIN, BLE, BMA, BNB, BOL, BXN, BYN, CDG, CEU, CGU, CLG, CNU, COZ, CUP, DIR, DR, LA, OA; W4 - ADA, AGD, AJX, APJ, ATS, AUA, AWP, BIO, BL, BOJ, BQO, DV, GI, OI, OT, QQ, UT; W5 - AAK, ABW, AOT, ATS, BBR, BED, CAI, COC, JV, LP; W6 - CTM, CXW, DOB, DZZ, USA; W8 - AFQ, AGU, AHF, AKU, APQ, AZQ, BAS, BM, BOG, BTB, CBF, CBM, CDY, CI, CIF, CIP, CSH, CTE, CTF, CXH, DHC, DIL, DJV, DMW, DWV, DYE, ECD, EEN, ELF, EYU, FBT, FGE, FNN, FQE, FXM, GCF, GFI, GFT, GTE, HEL, HII, SE; W9 - AN, ARK, AUH, BDR, BHH, BOF, CJJ, CME, CMZ, CNG, DGN, DKL, DYG, ENR, FFA, FKK, FMK, FPA, FWB, FZL, GHX, GJC, HOS, HPQ, HUZ, HWE, IMB, IPP, IZP, JBM, JBQ, JHL, JJX; AB1; K5AA; VE - 1EA, 2AW, 2BF, 2GH, 3AQ, 3TT, 9AA; CM - 2FM, 2WD, 8VE; EAR - 96, 155, 185, 224, 228; F8 - BS, OL, RJ; G - 2BM, 2OP, 2ZP, 5NF, 5OJ, 6CL; HAF3FV; HK1Z; LU3DE; OK2CM; ON4AU; PY2BN; VP2 - DB, DD; SU1EC; and the following commercials on which listening tests were made: DGG, FYL, GID, G5SW, HJO, KDKA, KFYR, KKZ, TIR, VE9GW, WAZ, WEAF, WQP, W2XAD, XDA.
From the mass of heterogeneous data submitted, involving so many variables, the problem of digesting and condensing the results so as to put them in a form for simple presentation can well be appreciated. Some of the variables encountered are time, location and extent of eclipse at transmitter, location and extent of eclipse at receiver, frequency of signal, transmission distance, power of transmitter, intensity of received signal, method of measuring intensity, and the ever present personal equation including such items as possible errors in time recording, operation of receiver at optimum sensitivity, and the estimation of intensity of signal where the R system was employed. Not the least confusing factor was the failure of many to report the system of time used.
Fig. 1 - 3500-kc. Band, 90 to 100% Totality
A - Less than 50 miles.
B - 50 to 200 miles.
C - 200 to 500 miles.
The scheme finally adopted was to show typical graphs of change in intensity of the received signal plotted against time for several conditions in each of the amateur bands. The sub-conditions are the extent of the eclipse over the transmission path, including areas having 90-100% totality, 75-90%, 50-75%, and less than 50%; and the transmission distance, including local, an intermediate distance where skip effect would be expected under night conditions, and longer distances up to the maximum range of the band.
The intensity changes are reported as decibels above or below a normal level. Where the R system was used a change in one number, such as from R8 to R7, or R5 to R6, was considered as a change in received energy of four decibels. The time ordinate shown is minutes before and after totality (or maximum extent of eclipse) considering the mean time of the maximum over the transmission path. For convenience of those desiring to compare the time with their own observations, the Greenwich Civil Time is also shown on the basis of totality occurring at 2030 G.C.T. (3:30 p.m., E.S.T.). At Douglas Hill, Maine, the computed times of the various phases of the eclipse were: first contact, 1920; second contact, 2028:47; third contact, 2030:24; and fourth contact, 2134 G.C.T.
Fig. 2 - 3500-kc. Band, 75 to 90% Totality
A - Less than 50 miles.
B - 50 to 200 miles.
C - 200 to 500 miles.
All the data were examined and found to agree very well with the typical curves shown with only scattered conflictions. A few unusual transmissions were reported but they must be considered as freaks which so often occur in short-wave work, their occurrence being increased by the greater number of stations on the air during the daytime and the extra vigilance of receiving operators.
Cosmic data supplied by "Ursigram " messages showed that the 24 hours from 1400 G.C.T., August 31st, to 1400 G.C.T., September 1st, was classed as a quiet day as far as terrestrial magnetism data was concerned. The preceding two days were days of moderate magnetic disturbances, and August 27th and 28th were classed as days of great disturbances. One sun spot, with a Wolf number of about 8 was visible on August 31st and passed from the face of the sun on September 2nd. Prior to this, two sun spot groups had crossed the face of the sun beginning on August 23rd and reaching a maximum Wolf number of about 24 on August 26th. The aurora displays for the days in proximity to August 31st were faint to moderate as observed at College, Alaska. Parenthetically it might be mentioned that the writer has observed on days when brilliant aurora were visible in New England, accompanied by violent magnetic storms, that the skip distance was greatly reduced; 15-meter signals were heard at a distance of 100 miles that under normal conditions were never heard.
The weather maps for the period of the eclipse showed a tropical storm progressing inland in the Gulf States. Rain occurred in the northeastern states, the Gulf States, and the Middle West. No pronounced isotherms were indicated for the eastern part of the country but temperatures were mostly above normal. Pressure was low in the Gulf States and high in the Middle West. There was no sharp pressure gradient in any part of the country except in the vicinity of the tropical disturbance. Scattered thunderstorms occurred over most of the eastern half of the United States on the afternoon of August 31st. The western half was mostly clear with temperatures below normal.
From these data it may be reasonably concluded that on August 31st radio transmission should have been approximately normal and that marked variations from normal could be associated with the solar eclipse. From the many local thunderstorms irregularities in QRN could be expected. Those observers who mentioned the fact confirmed that transmission was normal on August 30th, August 31st, and September 1st.
As is usual during the daytime, there was little activity on this band and too few reports were received to allow drawing any conclusions regarding any change in conditions during the eclipse.
A great many reports were received on observations in the 80-meter band and since the transmission distance was generally such as to include an area of nearly uniform solar coverage, the results are easier to interpret. Although both phone and c.w. stations were on the air with test signals, the best data received were on the c.w. signals since with the equipment usually accessible to the amateur it is more difficult to measure variations in intensity of modulated carriers. The curves shown are for c.w. signals but are equally applicable to phone transmissions.
Fig. 1 gives results in the area of 90 to 100% totality, all reports on reception of W1BZI. The A curves are typical of results at less than 50 miles, or little more than local distance. The solid line is reception reported by W1AGA at a distance of 40 miles in the zone of 99% totality, while the dotted line indicates the readings of W1AFC at 38 miles, also in the 99% zone but in a different direction from the transmitter. These show irregular "sunset" effects or fading in the early and late stages but with a general rise in level at totality. The dotted line indicates a decided peak lagging behind totality.
The B curve records the results obtained by W1ASP at a distance of 75 miles in a zone of 96% totality, and is typical of results from 50 to 200 miles. This distance, which at night would be expected to show skip on 80 meters, also shows irregular "sunset" fading but a greater rise in signal strength than the A curves. Lagging about a minute behind totality was a pronounced clip or tendency towards skip, for a short interval. This was followed by a large increase after which the signal rapidly returned to normal volume.
The C curves show results typifying distances greater than 200 miles which is about the maximum distance possible within the limit of 90% totality which was set for Fig. 1. The full line is the data reported by W3DZ and W3CL, the dotted line those of W3QL, all in zone of 93% totality and about 225 miles from the transmitter. Tendency towards skip is shown in the early phases and after totality. Signal strength was considerably raised over normal, in this case peaking about three minutes before totality without a corresponding peak following. The observations for the dotted line were not taken at as frequent intervals as for the other curves and hence show less irregularity.
Fig. 2 indicates results in the area of 75 to 90% totality for the 80-meter band. Curve A was submitted by W9BN on reception of W9AN at a distance of 44 miles with the eclipse about 76% total. Irregular fading is shown with peaks of increased signal before and after the maximum of eclipse and a pronounced dip between the two peaks, all lagging behind the visible eclipse.
Curve B is a composite of several reports at distances of 50 to 200 miles. It appears to be somewhat parallel to A. Curve C was submitted by W3AAJ on reception of W1APJ at a distance of 390 miles and the eclipse about 90% mean totality over the path. Signal strength is well above normal and peaks about seven minutes after the maximum coverage of the sun. In addition to this curve C, in the 75 to 90% zone R6 signals were reported at 600 miles, R3 at 800 miles, and DX of 1000 miles at the greatest extent of the eclipse.
In the area of 50 to 75% totality, insufficient data were obtained to admit of plotting, but the individual reports showed results similar to the 75-90% zone but to a lesser degree. On the Pacific coast where the eclipse was about 15% total conditions on the 80 meter band were reported as normal.
On the 40-meter band skip distance was such that very few stations at distances less than 200 miles came through at any time of the day. W1EKL could not be heard at W1EAO a distance of 200 miles at the beginning of their schedule at 1400 G.C.T. (9 a.m. E.S.T.) with the aid of a frequency meter set on 7150 kc. After listening 3 hours, W1ATW (220 miles) heard W1EKL for five minutes at 1700 G.C.T., when he was lost and heard no more. In areas of greater than 75% totality what few stations that were heard at distances up to about 200 miles fell out completely near the maximum of the eclipse.
In Fig. 3 is shown results obtained in the range of 200 to 1000 miles for various degrees of eclipse. These curves are composite averaged results from a great many observers and show general tendencies omitting specific fading irregularities. Curve A shows that near the path of totality signal strength was reduced, the maximum reduction peaking approximately with totality. As indicated in curve B for regions of 75 to 90% totality, signals at first increased and then decreased rapidly at the maximum eclipse coverage. Reverse effects were observed as the eclipse receded.
In regions of 50 to 75% eclipse, curve C, there was at first a slight increase in signal strength as the eclipse came on. This was followed by a dip to somewhat below normal and then a maximum increase was observed lagging somewhat behind the maximum of the visible eclipse. On the Pacific coast with 15% totality, curve D, signals gradually increased with the partial eclipse and then slowly decreased again to normal.
Fig. 3 - 7000 kc. Band, 200 to 1000 Miles
A - 90 to 100% totality.
B - 75 to 90% totality.
C - 50 to 75% totality.
D - 15% totality.
Distance reception of greater than 1000 miles was also reported in the region of about 50% totality at various times throughout the progress of the eclipse.
The distance of transmission on the 20-meter band is such that widely different extent of eclipse was present at the transmitter and receiver. In addition, contacts with European stations were over a sunset area as well as the path of the eclipse. No attempt has been made to differentiate between the results secured depending upon whether the transmitter or receiver was at the location of maximum eclipse effect. Undoubtedly a difference does exist, but there was insufficient data to make comparisons.
Many reported on reception of high-powered commercial stations with varying results. W1AFC at 99% totality reported no change in DGG on 22 meters from 1830 to 2125 G.C.T. (1:30-4:25 p.m. E.S.T.). W1VF at 100% totality reported a noticeable increase in signals from GID on 24 meters during totality. In the region of 70% totality W9ABS kept watch on WAZ, XDA, WQP, KKZ and HJO. From 1400 to 1800 G.C.T. the eastern stations were R5-R7 with marked variations, west coast stations R6 and steady. At 1800 the east coast stations rose to R8 very steady, but at 1900 dropped out altogether. The west coast stations increased to a very loud signal. From other sources we learn that the Canadian Marconi Company found no definite change in 22- to 37-meter transatlantic reception.
Fig. 4, curve A, shows the variation in reception of XDA (about 20% totality) on 20.7 meters by Charles E. Dewey, Jr., in Jefferson City, Mo. (71% totality), at a distance of about 1400 miles. Between these two points there was a time difference of about 20 minutes in the phases of the eclipse. It would have been interesting if these observations had been continued for at least an additional hour, as in all probability another peak intensity would have been found.
Fig. 4 - 14,000 kc. Band
A - 71/20% totality, 1400 miles.
B - Night/95% totality, 4000 miles.
C - 96/50% totality, 2000-3000 miles.
D - 99/65% totality, 1230 miles.
E - 79% totality, 1 mile.
It should be pointed out that the commercial channels are operated at a high power level and at a frequency that will give reliable communication under the prevailing conditions. On the other hand, amateur contacts on this band (and quite often in other bands) are with comparatively low power, and more often than not are in the "fringe" zone of possible contact. It is to be expected then that small differences in the transmission path would produce a much greater change on amateur transmissions than upon commercial channels.
European observers of American amateur signals, as well as observations from midatlantic ocean reported rapid irregular fading together with mushiness of note caused by high-speed fading during the period at and near totality. Curve B of Fig. 4 shows reception of W2CJM by ON4AU, a distance of about 4000 miles from darkness to a region of 95% totality and crossing the path of totality. A general reduction in signal strength peaking with the eclipse is noted.
Curve C indicates composite results of observations taken by G2JA at sea, 1560 miles east southeast of New York and in a region of about 96% totality on the opposite side of the path of totality from the United States. At this point sunset occurred at about 2120 G.C.T. Stations received were at distances of 2000 to 3000 miles down to about 50% totality. This curve shows a regular decrease in signal strength peaking with the visual eclipse. Results toward the end of the period were partially obscured by twilight effects, and this part of the curve is given as a dotted line.
In the United States, W1AZQ, in the path of totality, reported European signals fading out and 6th district coming in at 2000 G.C.T. During totality at 2030 G.C.T., only the 5th district could be heard and with diminished strength. From 2105 to 2145 G.C.T. only 4th, 5th districts and Cuba were audible. At 2200 G.C.T. reception was again near normal with the return of European signals until they disappeared for the night at 2215 G.C.T.
Curve D shows reception of W1HE (99% totality) by W9AOG (65% totality) at a distance of 1230 miles. Signals entirely disappeared for about one hour, the center of this effect lagging about five minutes behind the visible eclipse.
The results, curve E, obtained by W9RS and W9EGE are quite interesting and show that even in the region of 79% totality the reception of a one-watt oscillator over a distance of one mile was considerably reduced.
On the broadcast band reports indicated that at distances less than 100 miles night conditions of mushiness and fading were found during the maximum of the eclipse. At distances of 200 miles near the path of totality, no changes were observed. Reception of broadcast stations from four to five hundred miles distant faded completely or nearly out in various parts of the country, the maximum effect peaking with the time of totality.
W1AFC found no change in the intensity of FYL on 19,000 meters other than the normal daily change.
A great many amateurs reported changes in QRN and were led to the belief that the eclipse had left a high static level. A few reported no QRN for the entire period.
As mentioned earlier, during the period of the eclipse, there were a great many areas of scattered thunderstorms throughout the country, most of which occurred on the afternoon of eclipse day. Analysis of the QRN reports show that without exception those who reported bad QRN were near a local thunderstorm area, and those who reported no QRN were at a considerable distance from one. Of course the greater transmission range during the eclipse also carried the static disturbances over greater distances. So it appears that the eclipse can not be blamed for QRN conditions on August 31st.
Since the eclipse, the results of some other observation parties have become available and should be mentioned briefly in passing.
The Bureau of Standards reported that measurements made near Washington, D.C., showed that the critical frequency for the E region of the Kennelly-Heavyside Layer decreased about 1000 kc. during the eclipse, lagging behind phases of the eclipse by approximately five minutes.
Observations made in Canada under the direction of Drs. Henderson and Rose showed distinct losses in ionization of both reflecting layers E and F regions during the period of the ideal eclipse and no indications of a corpuscular eclipse.
Fig. 5 - Disturbance in F region of Kennelly-Heavyside Layer during eclipse, 3942 and 4540kc.
Messrs. Kenrick, Mimno, Pickard, and Wang gave a preliminary report to the Boston Section of the I.R.E. on results of automatic photographic records of echo lag behind ground signals. On 1640 kc. no echoes were observed until ten minutes after totality (2040 G.C.T.), when the E layer appeared at about 110 km. height. This persisted until 2110, when it disappeared and the F layer came in at 250 km. and remained until 2130. No reflections were then observed until 2145 when the E layer returned until 2200, when it vanished and was replaced by the F layer which remained until sunset. On 3942 and 4542 kc. no E layer reflections were observed, but there was an F layer disturbance of double-humped character coinciding with the visible eclipse. Because of its close resemblance to some of the amateur results of reception, the curve showing this disturbance is reproduced in Fig. 5.
And now after complete absence of any indication of a corpuscular eclipse, there appears an article in the public press stating that Dr. E.F W. Alexanderson of the General Electric, by using a frequency of 8655 kc. between Schenectady, N.Y., and Conway, N.H., had observed almost complete disappearance of signals two hours previous to the optical eclipse, and attributes it to a corpuscular eclipse. Although at this writing complete information on his tests are not available, and full comment must be withheld, it is difficult to accept his conclusions when it is remembered that his tests were conducted in a region supposedly outside the zone of a corpuscular eclipse.
The transmitter used at W1EKL, located at Douglas Hill, ME, with Sid McCuskey, W8DRP, in charge.
The output stage used an 860 with 300 watts input. Although 3500 kc. operation was first contemplated,
a frequency of 7150 kc. gave better signal strength at Cleveland both day and night.
At the outset it was stated that one of the questions which it was hoped to settle by means of radio observations during the eclipse was whether the ionization of the upper atmosphere was caused by ultra-violet radiation from the sun or by neutral particles shot off at a much slower velocity.
Amateur transmission was most certainly effected during the eclipse, the maximum effect in general coinciding with totality of visible eclipse or lagging a few minutes behind it. In all cases conditions approached those of night, the nearness of approach depending upon the extent of the eclipse in the region. The return to normal conditions seemed to be somewhat slower than the onset of the disturbance. On 40 and 80 meters, double humped intensity curves were observed similar in shape to the variation in the F layer height found by the Harvard group of observers.
This would seem to prove definitely that ultra-violet light, or some radiation travelling with the speed of light, is mainly responsible for the ionization of the upper atmosphere. The findings of scientific observers show that there were changes in the E and F regions of the Kennelly-Heavyside Layer coincident with the optical eclipse.
As regards a corpuscular eclipse, and the acceptance of the opposing theory, very few observations were taken by amateurs which could be used as a basis for a definite conclusion. What observations were made over a sufficient length of time and over the probable path of the corpuscular eclipse failed to show any effect of such an eclipse, if there was one, on transmissions in the amateur bands or on commercial frequencies close to amateur assignments.
On the other hand, if Dr. Alexanderson's results are accepted then it would appear that the effect of the corpuscular eclipse was quite small as compared to the optical eclipse and that the stream of corpuscles or neutral electrons from the sun exert only a small influence on the ionization of the upper atmosphere. So, for the time being, at least, we still have the two theories with us.
Fig. 6 - The graphical recording of W1EKL's 7150 kc. signals made at Case School shows a tremendous rise in signal strength between first contact and totality, the recorder pen going clear off the sheet at totality.
A few seconds later the signal dropped down to the background level and was inaudible for some 15 minutes. Then it gradually built up and reached a second peak just before the moon's shadow passed away, the pen again going off the sheet, with the second peak lasting somewhat longer than the first. The signals then gradually dropped to the normal level. The eclipse was over.
Many amateurs expressed a regret that it would be a long time before they could experience the enjoyment of noting the effects of solar eclipses on radio transmission. The results reported here show quite well that it is not necessary to be in the path of totality to observe a "radio eclipse." Wherever the eclipse may be, the ever resourceful amateur can select frequencies and stations upon which he can make satisfactory and convincing observations. Let's continue to make radio studies of coming eclipses.
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