Monday, April 29, 2019

FT8 Is Not a Low Power Mode

Early this year I gave a talk on 6 meter DXing with FT8. It was well enough received that I was twice asked to repeat my performance to two other clubs. If the interest shown is any indication expect to hear a few new DX seekers from FN25 and nearby grids on 6 meter FT8 this year.

I will not echo that presentation on the blog since many of the ideas therein were covered in 2018 blog articles. Instead I will dig deeper into one topic: power. How much is enough? Does it make a difference? Is it the right thing to do with FT8? With the summer Es (sporadic E) season on the doorstep and FT8 the go-to mode for 6 meters (personal preferences aside) this is a good time to review this sometimes controversial subject.

There is a widely held view that FT8 is a low power mode. I will state right up front that this is not true, or at least no more true than for other modes. Most of the time we all use more power than is necessary to complete a QSO, whether it is with CW, SSB, RTTY, FM or other modes.

We do this most often because it is a bother to fuss with power level and we don't really know how little is enough since we don't know the listening conditions at the other end of the QSO. Many hams contend with EMI in our dense urban areas in addition to QRM and QRN. Of course there are those who run QRO for no better reason than they can and want to do so.

Those are very general statements and I want to restrict this discussion to the unique propagation conditions on 6 meters. Operating FT8 on 6 meters is not the same as on HF, and we need to do it differently to increase DXing success. Es is particularly challenging and most of the time that is the propagation by which we work DX.

Es propagation for DX

Es openings tend to be spotlight openings in which, for example, your neighbour hears the DX but you do not. This is because the area of E layer ionization that supports 50 MHz refraction back to Earth is typically small and both stations need that ionosphere patch to be between them and "visible". Extend this to lengthy multi-hop path and the effect is accentuated.

The sample plot of 6 meters QSOs in a randomly selected opening is illustrative of this effect. Don't despair if you are not on one of these lines since the area and position of ionization patches that support 6 meter propagation constantly change. Like the aurora it is not the ionized patches that are moving but rather that the pattern of E layer ionization varies.

This variability is a part of the challenge of 6 meter DXing. When your neighbour has propagation, or someone midway along the wished for DX path, you need to keep monitoring since your turn may come next.

With a big enough station you don't always have to wait. It is possible to work DX when the MUF (maximum usable frequency) between you and the DX hovers below 50 MHz. This is due to forward scatter, a diffuse refraction of signals downward from the main signal path, which itself doesn't bend downward enough to be usable. Unfortunately the signal level of scattered signals is well below that of signals below the MUF. The lower the MUF the weaker the scatter.

Power and big antennas are needed to exploit forward scatter. This is an important advantage the big guns have over everyone else. With an amplifier you will have more success with forward scatter by increasing the duration of DX openings. Of course the other station must be sufficiently equipped or although they will hear the big gun they are not able to be heard. This is often my fate when calling the big guns.

Fitting FT8 into brief openings

The following fictional sequence is the shortest possible FT8 QSO with a DX station. Counting the first CQ it is 60 seconds long. It is reasonable to add the 15 seconds for the second CQ since it confirms that the other station believes the QSO is complete. Add another 15 seconds if you don't omit Message #1 (grid square). Real 6 meter DX QSOs rarely go so fast, often requiring 2 minutes or more.
  QQ8ABC VE3VN -10
This has implications since DX openings are typically marginal and brief. Frequently QSOs are not completed due to QSB. Another signal peak may occur but often doesn't, and even if it does the other station may be busy working someone else. With 6 meter DX Es there is no tomorrow: you might not get a second chance.

Power plays a role in this, or more precisely ERP (effective radiated power). This is a measure of the flux in the direction of the opening (azimuth and elevation), which is a combination of power delivered to the antenna and antenna pattern. For example, the ERP of a 100 watt transmitter through a transmission line with -3 db loss and an antenna gain of 11 dbi in the (ionospherically determined) DX path's azimuth and elevation angles would be a little over 600 watts.

Power helps the other station hear you but doesn't help you on receive. The antenna and transmission line gain and loss apply to both transmit and receive.

Now let's look at a fictitious but representative DX opening in diagram form. The horizontal axis is time, 15 seconds (FT8 interval) per vertical bar. The vertical axis is received signal strength with an arbitrary scale. The labelled lines are the noise floors for a variety of stations. The blue curve is the signal strength of the DX station.

Station A never hears the DX. This can be due to antenna, topography, noise or all these reasons. The better equipped B has just enough time to complete a 60 second FT8 QSO requiring a large dollop of good luck.

As the station capability improves you can see that there is more time to complete the QSO, and a reduced risk of decode failures and the necessity of repeated messages. We may aspire to be E but few stations are at that level. They are the 6 meter big guns.

Power and asymmetry

At right is a screen capture of my attempted QSO with 4X4DK last summer. I copied him quite well for several minutes yet he decoded me just once. Notice how the trend line of his signal strength mirrors the arc in the above diagram. Also notice the difference in reported signal strengths: it is more than 20 db.

This is a classic asymmetry. If it were due to power alone it would imply his transmit power was ~20 kW in comparison to my 100 watts. It's unlikely he was running more than 1 kW, leaving an unexplained 13 db difference. It may be due to noise at his end. WSJT-X uses his higher noise floor to calculate my signal strength. For me this situation is quite common since I live in a quiet rural setting whereas most hams are in noisy urban areas.

No matter the reason I need more ERP to be reliably heard. Either that or I wait for a better opening which may never come. I estimate that I missed about 20 DXCC countries last year, ones that were heard but not worked. Although 56 countries on 6 meter FT8 last year is pretty good, 75 would have been very welcome indeed.

"You can't work them if they can't hear you"

The immediately preceding example turns on its head the classic saying: "you can't work them if you can't hear them." More precisely said, the wording of the cliche depends on which side of the QSO you are on. To complete a QSO both stations must copy each other. However you can only improve your own station, and that means ERP must be considered.

There are a limited number of ways to improve your ERP. One or two of these should be attainable by anyone:
  • Power
  • Transmission line
  • Antenna gain and height
  • Move to a hilltop or the tropics
The last is not an option for the majority other than by portable operation or international travel. Moving is rarely feasible when DXing is the sole justification.

Single hop Es propagation can have a relatively high elevation angle. In contrast DX paths require multiple hops and perhaps ionospheric ducting, and sometimes joining the ends together with TE (trans-equatorial) propagation across the equator. These paths are most often at low elevation angles and that requires height or a hilltop.

Since going higher incurs more transmission line loss it is worthwhile to use the lowest loss coax you can acquire. Stacking yagis for gain is far easier on 6 meters than on HF. If you go this route I recommend vertical stacking for 2 or 3 yagis so that the gain comes from narrowing the vertical beam width rather than the azimuth beam width. It will make aiming less challenging and ensure your beam covers the maximum population possible.

Antenna selection in a stack can help you deal with elevation pattern nulls between all those minor lobes. The EZNEC elevation pattern above is for my A50-6 (optimized) up 24 meters. The lowest lobe is very good at below 5° but there are many nulls due to its being 4λ above ground. It is the ionosphere that determines the elevation angle, not your antenna, so if you have a null in the wrong place you'll attenuate the DX signals. Nulls in a stack are far less deep, or you can move the nulls by selecting just one of the yagis in the stack.

An amplifier is the easiest path to a bigger signal. By all means do so whether on its own or in combination with better antennas. Since you may cause AGC derived receiver desense to your ham neighbours within the FT8 window be judicious in your use of the amplifier. It is especially important to transmit a clean signal when you are QRO so adjust it for maximum linearity and have a friend check your signal for distortion products.
My preparation for Es season

I have no time for 6 meter antenna work in this year's busy schedule. A 6 meter amplifier is also low priority. My sole improvement has been to replace the transmission line. Following re-cabling work last fall the transmission lines to the outdoor switching system from both operating positions are LMR400 in the house, LDF5-50 underground and short LMR400 jumpers to the antenna switch.

The 40 meter long run of 35 year old RG213 I used the last two years has been removed and given to a friend for use on the low bands where its loss is low. A new run of LMR400 goes from the antenna switch at the base of the 21 meter tower up to the rotation loop. The small loss in the total run should be ~2 db better than before. Eventually I intend to use Heliax end-to-end. But not this year.

Every decibel counts on the marginal openings found on the longest DX paths. While I cannot guaranty a modest 2 db improvement will help it surely won't hurt. QRO would be even better, as would bigger and higher antennas. Perhaps in the future as time and interest permit.

A development I will be following this year is the emergence of FT4 since it promises shorter QSO times. This could be a good fit for 6 meter DXing. The price of lower sensitivity than FT8 may be well worth paying to best exploit signal peaks. Lower sensitivity can, in part, be solved with QRO.

Monday, April 22, 2019

Going QRO

It's finally happened: I purchased a kilowatt amplifier for my station. This checks off one more item on my plan for this year. It won't stop here since I need a second one for SO2R and multi-op. That may wait a while longer until I have sufficient filtering protection in my station to deal with high power.

I'm starting simple, with an old style amplifier of an earlier generation: the Drake L7. This amp is capable of over 1000 watts CW and several hundred watts more on SSB peaks (PEP). It is a grounded grid class AB (linear) amplifier utilizing a pair of 3-500Z tubes with a combined plate dissipation of 1000 watts. Initial checks show the power and electrode currents are within spec and power output is as it should be. With a stiffer power supply it could do more but it already reaches the legal limit in Canada.

An amplifier like this is not entirely straight-forward to install and use. There are many considerations to get the best from it during contests. I have not decided how far to pursue these objectives with this amplifier and may instead make this a temporary resident in my shack. For my present purposes it is acceptable. A more modern amplifier is in my future.

The limited use it has seen in the short time it's been here has been positive, both in operation and on air results. Because it has been many years since I've run QRO there are things to relearn. There is no rush and I am not easily seduced by transmit power as my ongoing use of QRP should impress. For me QRO is about entering contest categories where I will compete with the big guns to discover how much my antennas (and the operator!) can accomplish against the best. Successful QRO contesting requires a different style of operating to be competitive.

In this article I'll briefly cover what I believe are the most important aspects of integrating an amplifier into a contest station. There is more to it than finding room on the shack desk and plugging it in.

Electrical service

An amplifier that puts out 1000 watts of RF consumes substantially more than this. Going by amplifier efficiency alone the heat generated is ~800 watts. For amplifiers utilizing vacuum tubes count on ~150 watts for the filament(s). Since power supplies are not 100% efficient there is at least another 100 watts of heat generated. The rest of the circuitry consumes comparatively little power and can be ignored for this calculation.
My favourite electrician: Geoff VE3KID

The total power consumption is ~2200 watts. That's approximately 9 amps for a 240 VAC mains branch circuit. Peak consumption is higher on SSB but the amperage impact depends on power supply design.

Let's assume that we need 12 amps at 240 VAC. The branch circuit should be capable of 20 amps to allow a safety margin and to avoid inadvertently tripping the circuit breaker. I put two branch circuits into the shack. Receptacles are on the floor behind the operating desk to avoid fussing with fishing wire and punching holes in the wall.

My friend Geoff VE3KID, a retired electrician, did the hookup and installation of a 50 amp sub-panel and branch circuits for the amplifiers. He previously installed the service into my garage and workshop (shown in the picture). Running cables and putting in boxes was my job, which he inspected before doing the panel work and hookup. Geoff is also the fellow who installed the circuit for my 30S1 way back in 1985 when we were both much younger.

Although many hams are comfortable working with lethal voltage and current, hiring an electrician is strongly recommended. Where required have your utility inspect and approve the work. Aside from the immediate risk there is potential for future electrical failure or fire and a declined insurance claim.


Here I am referring to audible noise, not RF, although that too can be a problem (see below). Audible noise sources include fans, open-frame relays and power supply hum. Some can be managed by positioning the equipment. In other cases the amplifier may need modification.

L7 fan noise is modest. The stock L7 antenna relay is very loud and the power supply (a separate unit) hums when in SSB mode (high setting of the plate voltage). Neither is unusual with "classic" equipment of this vintage. Both can be cured with some work. I have not decided what I will do or if I will do anything. Since the amplifier may not be here for the long term I may let it be.

Headphones that totally enclose the ears reduce the noise to a barely acceptable level. This was never a problem with QRP! It takes some getting used to, or in my case re-acclimatizing myself to what I experienced many years ago when I had a Collins 30S1. It, too, was quite loud.


Since urban and suburban properties are small most hams have their antennas close to the house. The antennas may be directly above the house and shack. Should you have RFI problems with low power it will only get worse with high power. A previously RFI free shack can easily sprout many problems when you install an amplifier. Be prepared for it.

Your computer and peripherals are especially susceptible, exhibiting faults that can be difficult to identify and isolate. Keep a supply of RFI suppressing toroids and use then on unshielded (and even shielded) Ethernet and USB cables, power cords, video cables and so forth. RFI in appliances outside the shack can cause greater grief since your family will exert pressure on you to fix it or QRT.

RFI problems in the house and with neighbours have happily diminished over the years due to changes in technology. The ones that do appear can be more difficult to deal with since they involve digital technology. Proceed with caution.

My major RFI fear is with respect to SO2R and multi-op contesting. Until I have band pass filters and automated band switching the impact of 1000 watts on an adjacent receiver is not to be contemplated. Until then my QRO operating will be strictly SO1R.


An idling tube amplifier dissipates in excess of 200 watts. Waste heat increases to well over 1000 watts during operation. Although solid state amplifiers have much lower idling power because they have no filaments their operating heat dissipation is approximately the same.

Heat fills the shack and can make it uncomfortable in warm weather. An open window or air conditioning can remove the heat. In winter the shack can be made cozier by the additional warmth, and can also make you drowsy. These problems are exacerbated during contests since high power stations tend to run all the time, resulting in more on time for the amplifier(s).

If you live in a rural area like I do the cost of the electricity can be a burden. Less so in winter when the heat removes load from the furnace, even if electricity as fuel is typically more expensive than what is used by the furnace: mostly fossil fuels in Canada. My house has a ground source heat pump that runs on electricity but with a 5:1 ratio of heat output versus input. Space heaters and amplifiers produce heat at a 1:1 ratio.


Amplifiers are large and heavy. This can make them difficult to place on the operating desk. As you can see in the above picture I put the L7 on top of the FTdx5000MP. I can do this because the transceiver is structurally robust and the power supply is in a separate enclosure under the desk. A thick cable interconnects them, including a heavily insulated lead for the 3000 VDC plate supply.

The less weighty RF deck of the L7 is an easy reach for tuning and monitoring and has lots of space around the cabinet for forced air ventilation. For smaller, more fragile rigs the amplifier is best placed on the desk outboard of the rig. There is more reaching involved but then the rig is typically narrower (e.g. K3) or entirely absent (e.g. FlexRadio).

Broadband amplifiers with automated switching can be hidden away from the operating position, taking up none of the valuable desktop. You might notice this in pictures of big gun stations where there is no more than LCD displays, keyboards, VFO knobs and paddles. That's very nice but also very expensive, at least at present.


Have you checked the prices of high power RF tubes lately? They're high and getting higher. One reason I chose an amplifier with glass envelope tubes is that they are less dear than their metal-ceramic cousins. However they're larger, requiring a larger cabinet, and more fragile.

When run properly both styles of tube can last for many years, but one mistake can be costly. Tetrodes in particular are very sensitive to abuse since the screen grid is typically unable to dissipate any heat at all. That's unfortunate since tetrodes typically have lower distortion. Over-driving grounded grid triodes is also a recipe for early failure. Too many hams push their amplifiers hard, reducing lifetime and polluting the bands with distortion products. Many learn their lesson the hard way when they need to replace an 8877.

Suffice to say it is important to operate amplifiers with care, retuning as necessary when changing frequency, band or antenna. Diligence can ensure that you'll never have to replace those expensive tubes. Solid state amplifiers are no panacea since they have other concerns, such as intolerance of mismatch and, in many cases, greater distortion products. On the positive side these newer solid state amplifiers have safety features to protect you from faults and operator error.

Ceramic tubes such as 8877, 4CX1500B and many others require a 2 to 3 minutes warm up before they can used. This can be aggravating for DXers. Don't bypass the safety feature that enforces the delay or you'll face a drastically reduced tube lifetime.


Speaking of tuning, it is worth mentioning a few of the challenges involved. Most hams are accustomed to broadband transceivers that handle frequency, band and antenna changes without operator intervention, including an ATU with memory. That is rarely the case with a kilowatt amplifier. The impact on contesters such as myself can be significant.

Tube amplifiers in particular almost always require manual tuning of the output tuned circuit. The output impedance of a tube or FET amplifier is higher than 50 Ω, while bipolar transistor amplifiers have a lower impedance. In all cases impedance transformation is required. Broadband transformers can be effective for most solid state amplifiers, but these can be large and expensive at the kilowatt level, and are usually impractical for tube amplifiers due to the large impedance ratio.

Broadband transformers also require that antennas be close to 50 Ω if they are to perform well. Manual tuning of tube amplifiers can match a wider impedance range at the price of operator effort. Having your antennas exhibit low SWR makes operating any amplifier much easier and safer.

Contesters and other active hams will happily deface their amplifiers with stick on labels for penning marks for various antennas and frequencies so that tuning can be accomplished quickly. Fewer contest QSOs are lost and DXers are less likely to miss out on rare DXpeditions. It can also help to avoid tuning errors. If you do use labels try to find those that are easy to remove and do not leave a permanent mark on the panel, otherwise you will have an eyesore with a lower resale value.

We can't forget the amplifier input which must also be tuned since the input port is rarely 50 Ω. Untuned amplifier inputs are found on lower end equipment and may require use of an ATU on the transceiver. Even with tuned inputs it may be necessary to use an ATU on the WARC bands, depending on amplifier vintage and quality. Since my amplifier has tuned inputs I have to turn off the rig ATU when I go via the amplifier to an antenna with a poor SWR. That's one more detail to worry about until all my antennas are good 50 Ω matches.

You may notice that if the rig and amplifier could be integrated that the transmitter output network and amplifier input network could be collapsed into one. Since that it rarely the case, and indeed the rig is often operated alone, an impedance of 50 Ω between the units is sensible.

Another thing: did you ever notice that many modern rigs don't have a button to transmit a carrier for adjusting an external tuner or amplifier? Something needs to be rigged up to implement this feature. On my FTdx5000 there is a jack on the rear panel (Tx Req) that you supposedly ground to do this, but mine doesn't doing anything. I'm working on it.


Although not often thought about in the typical ham's station, once you add an amplifier there may be a need to deal with sequencing. For our purposes the only signal of significance is when you go key down. Problems can arise depending on where the signal comes from: keyer, computer, transceiver or other peripheral controller, and the speed of the switching circuitry in the rig and amplifier.

Most high power amplifiers use relays at the input and output to switch the amp in and out of the circuit; during receive the amp is bypassed. The output relay tends to be of the large and slow type to handle the power. If RF appears at the input port before the relays fully engage hot switching can occur. This can damage the relays, cause arcing in the amp and truncate the first transmitted symbol. This is mostly a problem on CW, on that first dit or dah, and on digital modes, but typically not on SSB unless VOX is used.

When using a "smart" keyer such as a Winkeyer or contest software the sequencing problem can be mitigated with some experimentation. When playing memories -- these are the majority of contest transmissions -- delay can be added between assertion of PTT (Tx enable) and the first message symbol. On SSB it is even easier since it is unlikely that the message begins at full volume. The trouble is with VOX on SSB but especially with CW sent with paddles. In the latter case there is no way to advance PTT assertion, and delaying symbol transmission will adversely affect the operator since audible feedback will be out of sync with the fingers.

In initial testing of the L7 the serial assertion of PTT from Winkeyer to rig to amplifier does not affect the initial CW symbol. Monitor the bands during a contest and you will find instances where the first symbol is short or entirely lost. The problem gets worse as CW speed increases. If you have any instances of arcing in the amp (relays, capacitors, etc.) stop immediately and deal with it.

There are two alternatives to serial chaining of PTT. One is to key the rig and amp in parallel from the computer or Winkeyer. Before trying this ensure that the voltage and current are within the capability of the Winkeyer or computer circuit you are using. Those big relays in older amplifiers can draw more current than you expect.

The second alternative is to modify amplifiers with electronic switches and fast relays. These are far quieter as well (see 'Noise' above). Vacuum relays at the output port of the amplifier may be required. The best systems are QSK compatible.

What all of this means to me

From the foregoing discussion you may appreciate why I have been slow to include an amplifier in my station. Aside from trying it out on the bands during ordinary DXing I have yet to put it to the test in a contest. I am in no rush since the contest season is winding down with the arrival of spring. Good thing, too, since my antennas are in rough shape.

Soon enough I will try it out in a minor contest. That will give the amp a good workout and will force me to exercise my QRO contesting skills and tactics. It is very different in comparison to low power and QRP contesting. I will also have to practice rapid band changes.

With the arrival of spring and sporadic E season it is a shame that this amplifier does not work on 6 meters. At some point I will need more power on that band for optimum DXing performance. That will shortly be the subject of another article for the blog.

That I now have an amplifier does not mean I will no longer operate low power or QRP. I enjoy all power levels and will continue to be flexible in my operating choices. I prefer to delay QRO contesting until I have made more progress on low band receive antennas. Otherwise I will not be able to copy many of the smaller stations who will call me. I do not want to be an alligator.

My second amplifier, when I get one, will likely be more modern than the L7. I would like one with better operating features, in respect to many of the considerations raised in this article. Broadband tuning would be especially welcome. When a suitable amplifier becomes available I will make my move. I can afford to wait.

Tuesday, April 9, 2019

Quality Matters

Last week while doing ground work on an antenna I needed a clamp to set a mechanical stop on a ⅜" steel rod. A 5/16" cable clamp is a good fit so that's what I used. I keep a variety of new and lightly used clamps of all types in my junk box for just this kind of occasion.

As I tightened the nuts on the clamp one of them suddenly went slack. I looked down at it and discovered that the saddle had snapped. This was a brand new, never used clamp that still had the label on it. Torque on the nut was very light at no more than ~3 ft-lb since that's all that was necessary for my purpose.

The picture does not show microscopic detail so I'll describe the break. There was no audible sound when it broke. The broken pieces fit together so well that the seam between them is almost invisible. There is no distortion of the steel at the failure surface. The break went right through the ridges in the saddles, so that stress riser was not the problem. The interior metal is clean and crystalline in appearance.

On the basis of this visual evidence I suspect that there was a manufacturing error during the forging process. But that is not at all certain; it's an educated guess. I have never had a failure with this brand of wire rope clamp in the past.

Yet clamps do fail. They fail often enough that just one clamp should never to be used to secure a cable. Two is the minimum and three is considered best practice. Not only must you use this many clamps there is a procedure on clamp placement and tightening sequence in order to achieve the rated holding strength. Of course many people are not aware of the proper procedure or choose not to follow it. In my experience this includes the majority of hams who use cable clamps.

You may be interested to learn what the fine print on that label says, in three languages:
"Do not use where disengagement could cause property damage or serious bodily injury."
A catchall similar to this one is quite common across all industries and products. How well it protects the manufacturer or retailer in case of injury or property damage I cannot say. It is so common that its presence tells us little about the quality of a product, or lack of it.

Like most sensible hams I only use cable clamps for light duty guying and other mechanical applications for tower and antenna work. I always use at least two, even for a brief one time use. Examples include the rigging for lifting tower sections and antenna tram lines. If you must use clamps on EHS guys be sure to use the clamps made for this application, not clamps designed for wire rope and aircraft cable which are more compressible and therefore most tolerant of clamp type.

Of course one should use guy grips for EHS tower guys which are far more reliable. If you shop around you'll also discover that it's cheaper to use a grip than 3 cable clamps designed for EHS. They're also far easier to put on, and to put on properly.

On critical installations never choose false economy over safety. Quality matters. As for that broken clamp? I may take it back to the retailer (a reputable company with many commercial clients) to see what they say. I don't want my money back but they ought to follow up with their supplier.

For another example of a faulty clamp witness the one immediately above. These specialty items have a stainless threaded stud welded to a stainless hose clamp. They are used to secure devices to round masts and yagi booms. This one was supplied with a balun from Balun Designs, which uses two of them to attach the flat balun mounting plate to the boom.

I really don't like breakage like this at the top of a 150' tower. It appears that the welding of the stud weakened the clamp strap. I am left to wonder whether this is a design flaw in which welding heat weakens the stainless steel strap. That would be a pity since they are very useful for antenna work. None of the others in my possession have broken and I replaced the broken one with another from the same company. Time will tell.

As always: be safe out there.

Saturday, April 6, 2019

Spying From Above

A few weeks ago I needed to study the local area using satellite imagery. When I expanded the view centred on my place I was pleasantly surprised. Sometime during the past year Google updated the images for this area. For the first time I have a picture that is almost up to date with construction of my antenna farm. You can click on the image to see it in full resolution -- caption link takes you directly to the source. Indeed, you'll have to to see the finer detail I'll be discussing.

Extracted from Google Maps

Before going into radio stuff I should explain the peculiar patterns. The satellite image was captured during haying season when my neighbour had started on my land after finishing with his own. That dates the image to late July or early August, and the shadows indicate mid-morning. Notice how he deals with the tower base, guys and wire antenna anchors. He's very considerate and careful; after all, he's a guest on my land.

Notice the mind-bending perspective: everything leans right at a 95° bearing. The exact position of the satellite is not known from this, apart from saying that it was a little north of west. A few moments with a ruler and calculator converts the projected linear length of the tower lean to determine the satellite's elevation angle: approximately 63° above the horizon. Algorithmic processing transforms the curved quasi-trapezoidal perspective to rectilinear coordinates. Since the details of objects are unknown their shapes are not corrected. Hence the peculiar image.

With that interesting if irrelevant detail out of the way let's see what we can learn from spying on my antenna farm circa last summer, before the new big tower was planted. One is that you can see that the scars of the cable trenches have not healed. I believe that the trench to the 80 meter vertical array had not yet been back filled, explaining its prominence.

Staying with the 80 meter yagi you can see its orientation by the trench scars running from the central tower -- driven element -- to the 4 parasitic wire elements. Notice that they are not at right angles, allowing me to optimize array directions, which is not possible with a 4-square. As a result the radial field shape is oblong. The radial field is staked and mowed; haying is banned.

Turning to the yagis, you'll notice that some elements are highly visible while others are difficult to pick out or are not visible at all. This is due to the illumination angle, yagi orientation and the resolution limit of the satellite image. Where there is specular reflection very narrow aluminum tubes are prominent despite being well below the image resolution limit. In other cases similarly sized elements are not at all visible.

On the Trylon tower near the house the TH7 elements are quite visible but only the boom of the 6 meter yagi above it is clearly visible. On the 150' tower the largest elements of the top yagis are visible. Their direction appears to have reduced the level of specular reflection and therefore visibility.

The long European (northeast) Beverage in the northeast bush area is of course invisible. Yet there are some short sections along its path that appear fuzzily. My guess is that periodic inspection and service walks along the antenna route create visible scars in the vegetation. On the ground my walking path is only noticable when there is snow. Since I detour around trees the path is not entirely straight.

A curiosity regarding resolution is the central tower of the 80 meter array. Due to the perspective it leans in the same manner as the other towers yet the tower is just a fuzzy smudge. The weathered galvanizing is far less reflective than the white paint on the big tower. The Trylon is a slightly less fuzzy since most of the galvanizing is less weathered and the structural members are wider. The two unpainted galvanized sections in the 150' tower look like gaps for the same reason.

If geology is your interest there is something for you as well. Notice the brown tint in the hay west of the 80 meter array, adjacent to a treed area. This is usually a sign that the topsoil is thin where the bedrock approaches ground level. To protect farm equipment such as plows it is common to leave these areas wild. There are places such as the patch north of the array the bedrock pierces the surface. I have been lucky that none of my tower excavations hit bedrock.

Is any of this useful? As I've written before this can be a good way to satisfy your curiosity or to spy on your competition. For non-contesters it can be informative to study the layout of others' towers and antennas.

Monday, April 1, 2019

Does the Sun Have an Off Switch?

Excerpted from chart 14 of Tapping 2010
The 10.7 cm solar flux has long been used as more scientifically reliable measurement of solar activity than the sunspot number (SSN). The two are roughly correlated, permitting continuity of data going back centuries to when the only relevant observable was SSN.

However the true measure of solar activity can range significantly higher, and lower, than what the SSN indicates. A simple correlation implies that when the SSN is zero the 10.7 cm solar flux is ~65, and would therefore represent the lowest possible level of solar activity. This is not quite true, and as the NOAA says the 10.7 cm solar flux can dip below 50.

A star core is a thermonuclear furnace with the outer layers behaving in accord with thermodynamics as it transports heat from fusion to surface by convection. Aside from magnetic turbulence and other episodic and periodic phenomena it is exceeding difficult to shift the sun from thermodynamic equilibrium. More precisely, the probability of deviation from the equilibrium point declines rapidly with distance and deviation duration becomes increasingly brief.

This brings us to the puzzle of NOAA's latest forecast of solar activity beyond the demise of cycle 24.

Here we see the smoothed solar flux not only dipping below 66 but going far lower and remaining there for the foreseeable future. Calling this exceedingly atypical is an understatement of the first order. Indeed, it is alarming. What is going on here? Are there hitherto undiscovered periodic or secular dynamics within the sun's interior? Inquiring minds want to know.

Now we must acknowledge that not everyone is on side with the NOAA forecast. One reviewer calls it "fatally flawed and an embarrassment to NOAA's scientists." While this may be true these same scientists have held to the published forecast for quite some time in the face of pointed criticism. There must be something to it, something they have yet to disclose. Whatever it is it has to be big, really big. Is it in fact possible to upset the thermal equilibrium of the photosphere for years?

Numerous scientists have been hard at work to develop the theoretical framework to explain the latest forecast. These have ranged from the mundane to the sublime, from the finding of errors in current models to new physics. While some of them delve into the unknown with unbridled enthusiasm they may be worthy of consideration since the impacts could be dire. After all, the health of the star at the centre of our solar system determines the fate of humanity and even the Earth.

One of these novel theories was recently proposed by Dr. Lance Boyle, an astrophysicist and accordion aficionado. He has some intriguing insights into the coming plunge in solar activity. But don't worry, he doesn't think the decline is permanent. He likens what is going on to a temperature inversion in our own atmosphere.

"There is tremendous turbulence in the sun below the photosphere," he explains, "that is driven by high-energy photons that are too far below the surface to radiate into space. This is much like our own atmosphere, but with heat from the nuclear furnace coming from below rather than from above. Sometimes convection cells deliver so much hot gas near the surface that they form a barrier preventing the cooler regions associated with sunspots from reaching the surface."

Cutting through the technical jargon he goes on to say that the sunspots are still there but are below the surface and unable to influence solar radiation. With a knowing look he claims, "the sunspot cycle is doing just fine even if we can't observe it directly. Cycle 26 will probably bring a return to normality once the turbulence, sub-solar storms if you will, break up the inversion."

A more radical theory, an outlandish one in the view of many solar astronomers, is credited to Dr. Suzy Sunshine -- an unexpectedly appropriate name for a scientist in the field -- who is a post-doctoral fellow studying stellar dynamics. Her theory relies on the fundamentals underlying the laws of thermodynamics. "The sun is mostly hydrogen, but it is only in the core where the temperature and pressure are just right for hydrogen fusion to take place."

She says there are countless collisions every second between hydrogen atoms in the sun's core, due to their high density and temperature. It's a thermal engine in an exquisite balance. "Too much fusion and the core expands to reduce collisions, while too little fusion and the core contracts to increase collisions. The sun's nuclear core is regulated by the balance between outward photonic pressure and inward gravitational pressure."

Thermodynamics is driven by probabilities, not by certainties. Those countless atoms of hydrogen have degrees of freedom in their seemingly random movements that can upset the balance. "Very few of those collisions between protons, the hydrogen nuclei, actually result in fusion. Too much helium in the mix or anything else and fusion rate will decelerate. From time to time it may be that helium, the waste product, needs to be cycled out of the core. But this can only happen if the production rate declines. That is, less fusion and less solar activity."

But like Dr. Boyle she believes it should be a temporary event. "Eventually the surplus helium is cycled out of the core and fusion returns to its former rate." For how long? "A few years, I think. We don't know for sure. The calculation is difficult." Dr. Sunshine has asked for two of the neutrino experiments to resume measurement of the solar neutrino flux, but to no avail. "This would give us a direct view of what is going on in the core right now. They're just not convinced that this is urgent."

Wandering off the mainstream there are more outlandish theories about what's going on. Outlandish, yes, but then so is the solar activity forecast. Perhaps among these mavericks the truth can be found.

A professor who uses his tenure as a shield against his critics to repeatedly push at the boundaries of science is Dr. Hernando Cojo. His hypothesis brings us face to face with one of the more profound and puzzling aspects of thermodynamics. The hydrogen atoms could, all at once, jump out of the core leaving only helium behind. "It's a rare thing but it's quite possible," he points out. "Thermal equilibrium is nothing more than the most probable arrangement of hydrogen nuclei. Think of it as the equivalent of that old joke about suffocating because all the air molecules simultaneously jump to the other side of the room."

Physicists we consulted dismissed his hypothesis: it's just too improbable, unlikely to happen over the lifetime of our solar system. But, Dr. Cojo claims, there are 8.9 × 1056 hydrogen atoms in the sun and we only need a small fraction to do this. "That's a lot of material and improbable states are happening all the time somewhere in the sun. And keep in mind there may be 1024 stars in the universe, and vastly more than this in some versions of cosmic inflation. The universe is big, really big. It's nearly a certainty that it will happen somewhere. So why not here, now!"

He likens it to a lottery. Your chance of winning is minuscule, as is everyone else's. Leaning forward he emphasizes the point with some heat. "Yet, someone does win."

A more peculiar proposal comes courtesy of Dr. Constance Boltzmann. Hydrogen in the core exists as a plasma, having been stripped of its electrons. She asks questions about those missing electrons. "It's a plasma because the high energy conditions prevent electrons from binding to protons. But the electrons have to go somewhere. They aren't lost."

In her theory the heat of the fusion furnace pushes them to the periphery of the core where they form a layer of highly negative charge. The core, full of hydrogen and helium nuclei, is positively charged. "It is sustainable for awhile," she claims, "but eventually something has to give." That something is what she coolly refers to as the mother of all lightning strikes. "The plasma fractures and the electrons rejoin the protons."

The charge neutralization is brief since the core is too hot and the electrons are stripped out again. This takes time. "Until then fusion is reduced because the electron partial pressure increases the distance between hydrogen nuclei. It's probably what caused the Maunder Minimum. The core goes through these cycles, but an irregular one that is difficult to forecast."

Drs. Sunshine and Boyle, at least, have submitted papers to high profile scientific journals for peer review in an attempt to reach out to the broader astrophysics community. More minds on this important problem should bring us closer to the truth. It might also serve to free up resources to gather data, such as the solar neutrino flux that Dr. Sunshine is so keen on. Time will tell.

There have been more alarming theories proposed than the ones presented in this article. We have chosen to leave those aside for now because they are indeed quite worrisome. We can hope that NOAA's ghastly solar activity forecast is mistaken and that cooler heads will prevail. Many of the experts we consulted for this article do not think that the worst is likely to come to pass. We can only wait for NOAA to issue their next forecast and hope for the best.

Don't worry and have a happy April 1st.