Thursday, October 26, 2023

New Rig: Icom 7610

For several years I've had a new transceiver in my annual plan. This year was no different. What is different this year is that I finally did it. The spur was the upcoming CQ WW SSB contest. Since this will be the first multi-op contest from my station, I was uncomfortable asking others to put up with the relatively ancient Yaesu FT950. It was only marginally acceptable when it was just me using it, and then only during contests when I operated SO2R.

The FT950 is not that bad of a rig, for its time. It is unsuitable for a modern contest station where I want ultimate performance. I've had it for years and it did what I asked of it, and it is now set aside. For the time being it will be a backup rig. It will eventually be sold. Due to the march of technology, perfectly good rigs of an earlier generation fetch increasingly lower resale prices. It is almost not worth selling.

The IC7610 is a complex rig and there is much to learn. I have to learn quickly because the contest is almost here. I moved slowly while setting it up and integrating it into the station to avoid mistakes. For now it is a drop in substite for the second operating position. When the contest is behind me it will be become the rig for the main station. The Yaesu FTdx5000MP will be demoted to the second operating position. It has been my primary rig for more than 6 years, but it's time for it to be set aside.

As I said, it's an expensive item and I did not spend the money without due consideration. Is it worth the money? Many hams would never spend that much on a transceiver; I know that I am reluctant to do so. Needs and means are different for each of us, and for me this was the right choice.

Here's how it looks in the shack, as it has been rearranged for two-position multi-op in CQ WW.

It's small and light, and hardly looks as if it is worth the price. The FTdx5000MP is nearly 3× its weight. When the contest is behind me, I will get deeper into its features and capability. For the next few days I am solely focussed on the features needed during the contest. I am likely to have more to say about the 7610 in the future.

The following is a quick take based on my first impressions. Bear in mind that first impressions can be wrong. Do not interpret this article as a review because it isn't.


The FTdx5000 has almost every operator feature on the front panel. The panel is large, the buttons many, and the buttons are small. It has to be this way because the features are many and the text-based menu system is slow and difficult to navigate. This high end rig predates the adoption of touch screens. It is one of the last of the "big iron" transceivers. 

Buttons have their good and bad points. The majority of the features are not used or rarely used. That's a waste of panel real estate. They are small and hard to read, especially in dim lighting. You remember the buttons you regularly use and mostly ignore the others. Another point that is rarely considered is that cleaning the multitude of tiny buttons and knobs with their textured rubbery surfaces is difficult. But it must be done. A years long buildup of dirt, grime and skin oil is a subject best avoided in polite company.

The OLED displays age poorly and, as you can see, the ones on the lower right are in dire need of replacement. This is a well known flaw of the '5000. Their replacement will be a winter project. 

Another problem with many closely space buttons and knobs is that it's easy to grab the wrong one while you're operating. Often you will accidentally bump the ones nearby with unpredictable results. If it's a feature you rarely use it can take some time to figure out what happened and to correct it.

There are few buttons on the IC7610 front panel. A large fraction of the space is taken by a touchscreen where many features can be directly accessed or accessed via the menus. Whether the physical buttons are assigned to the right features is debatable. Operators will have different opinions depending on their individual needs and interests. It's too soon to have developed a solid opinion of my own.

Menu maze

The number of transceiver features increases with every generation of technology. Buttons and knobs for all of them is impractical. Of course there are many rigs that are designed to have a small feature set and don't need more than a few buttons and knobs. But those are usually smaller or special purpose products that take a minimalist approach for specific purposes such as portable operation. High end rigs are feature rich and need menus.

Although they many be necessary, menus are not always better than buttons. For a sophisticated rig like the IC7610 the menu system is a deep tree with many branches. It can be difficult to reach many features or even to know where to look in the menu system. 

The names of novel features can be so unfamiliar that you can easily pass by the one you want. Reading manuals is tedious, and there are two of them for the IC7610, the basic and the advanced. Both are large and from my reading the descriptions are occasionally puzzling or incomplete.

That said, the menu system for the IC7610 isn't that bad considering its extensive feature set. Pressing the Multi key (upper right) displays a context sensitive list of only a few features. For example, transmitter power and mic gain. There are several context sensitive features on the left side of the touchscreen that can be directly accessed by a short or long press.

It took me several days to become reasonably comfortable with the menu system. Every modern rig has a learning curve and each manufacturer has their own ideas for menu design. There are many critics of the FTdx101's menu system. I tried it for myself in Dayton last year. That is one reason I favoured Icom for this purchase.

Menus are a necessary modern evil, so I live with it. I escape a lot of the tedium of operating feature use, like with RIT and XIT, using the keyboard commands of N1MM+. I preferentially do that whether or not I'm in a contest. There's less to learn because the N1MM+ keyboard shortcuts for common features are the same for most every rig.

Connector standards

The simplest things can cause a lot of grief. The most basic interconnection needs are the microphone, headphones, keyer and PTT (in and out). At least headphone and keyer jacks are almost always ¼" or 3.5 mm. I'd prefer they all were 3.5 mm but I can deal with it using the adaptors I've accumulated over the years.

But...microphones? Dynamic vs. electret, 3.5 mm vs 8-pin Foster, and different pin outs for the same physical connector. This must be quite the revenue generator going by the extortionate prices they charge for their branded lines of microphones, complete with their unique mic connectors and features. One of my first jobs was to make an adaptor for the 8-pin Foster connector to allow connection of a 3.5 mm electret mic almost universally used for PC headsets. A USB headset connector would be even better. The connectors are right there on the 7610 just above the mic connector.

PTT was easier in one respect. Unlike so many transceivers, the PTT line (that they call Send for some reason or other -- see my thoughts further below) is a simple phono connector. I have loads of phono-to-phono cables. However, there is nothing simple about connecting a foot switch and keyer for PTT control (that they confusingly also call Send). There's an 8-pin DIN (ACC1) where that resides. 

The rig does not include the DIN connector. In fact, the only connector they include with a multi-thousand dollar piece of equipment is a ¼" stereo plug. Typical of most transceivers, the interconnecting cables are included with the other equipment that they sell. In most cases it's their amplifiers.

By some miracle I found one of these connectors lying at the bottom of a box full of orphan connectors and cables that I've accumulated over the decades. I soldered on a phone jack and plugged a splitter into that. I could finally connect the foot switch and keyer.


The USB connection to the PC removes clutter from the back of the rig. One cable replaces several. Since it provides both CAT and a sound card, there are no separate audio cables. 

There is a prescribed installation process to properly install the driver so that Windows doesn't substitute its preferred driver with which the interface will not work. I appear to have done it correctly since everything works as it should.

One way in which Icom is deficient in comparison to other manufacturers is that not every function on the rig is accessible or completely controllable by the PC. I knew this in advance. There are a few peculiarities when using N1MM+ despite the development team's best effort to overcome those deficiencies. I can live with it.

One day soon I hope we can eliminate the cables entirely when the PC connection evolves to wireless and TCP/IP. Some rigs have already done so and I expect the rest to eventually follow. But for now this style of PC interface is good enough.

It's different

Equipment manufacturers have most of the same features as all the others in the same price class. Of course they also have unique features, and those can be very useful. Competition is good! What annoys me is that for the common features they too often use unique terminology and methods to manipulate those features. This has proved to be an obstacle since I've never owned an Icom HF rig before. I had to figure out their names for the features that I am familiar with.

For example, what most hams call RIT and XIT is called the Clarifier by Yaesu. Icom uses the more common terms so this was easy and welcome. The Twin PBT feature of the 7610 is very nice, but only once I figured out the relationship between the high/low cutoffs, filter selection and width controls and their relationship to the CW pitch control. Okay, maybe that isn't too difficult a difference.

There is a prominent button above the VFO knob labelled Change. Change what? So I pressed it and discovered it's what most other rigs call the A⟺B feature to swap the contents of the two VFOs. I'm still trying to figure out what the XFC button symbolizes but I did finally figure out what it's used for. The bizarre name does not make it intuitive. I'm still puzzling out split and dual watch which we need for 40 meters in the contest.

I was surprised to find that the AF Gain also controls the volume of the CW side tone monitor. That's very odd. It was disconcerting when I first encountered it when, after turning down the gain, I had difficulty hearing what I was sending when I next transmitted.  

Speaking of CW, why can't there be a common usage for normal and reverse CW reception? CW (normal) on this rig is the opposite of what I expect (USB reception), and was pretty well the standard decades ago when tubes ruled the airwaves. At least I could reverse the default behavior of CW and CW-R deep within the menu maze.

One thing I really liked was the speed of the ATU. Compared to previous rigs I've owned or used it's wonderful. Not only that, the tuner setting hold over 100 kHz. This is far better than the 10 kHz typical of so many other rigs. Unless you use a small magnetic loop antenna there is no need to tune every few kilohertz.

Well, there's lots more I won't bore readers with. You get the idea. Like connectors, I wish rig manufacturers would standardize more of their terminology for common features. They have no particular incentive to do so since their customers don't base their purchasing decisions on it.

Contest priority

I am trying to understand this rig in time for CQ WW SSB this weekend. When the team arrives I have to be able to explain to them how the rig works. I'm getting closer so we'll have to see how it goes.

After the contest I'll have a better understanding. Expect to hear more about the rig and other contest matters after the weekend is in the rear view mirror. When there's a long enough break between contests and DXpeditions I'll swap the IC7610 and FTdx5000MP to make the former my main rig.

Tuesday, October 17, 2023

Belated 6 Meter Season Report

Each year I report on my 6 meter experiences after the end of the sporadic E season. It usually comes out in mid-August. This year I'm 2 months late; it is not because I've been putting it off. The season was not the greatest and with the increasing solar flux and the approach of the fall equinox I hoped that I would have more of interest to say by waiting. 

I regret to say that I was disappointed with both sporadic E and equinox north-south propagation (TEP). That makes the year interesting in some respects and less so with regard to my (and others') achievements this year. 

Despite the disappointments, let's go ahead and recap the year. We can learn from mediocre results, often more than with spectacular results. Many may therefore find this article uninteresting. Since I find it educational, I'll press on regardless. Read on if you will.

Perspectives on propagation

Reports of the sporadic E season have varied. In this part of the world the experience seems to have been mostly poor. Others had greater success. Propagation is not the same for everyone. If you're an ARRL member, please read the VHF column in the October QST which contrasted the differences among locations. A lucky few had great propagation this year.

Antennas matter. The more marginal the propagation the more the antennas matter. It is common for those stations to have openings that others nearby do not. I frequently notice this since my 6 meter antenna is higher and bigger than many of my friends. There are many bigger stations and in better locations who do far better than I ever will.

TEP to the southern hemisphere has been productive though not as good as I had hoped. The fall equinox season had one good opening and many "teasers" in which little could be worked. However the spring equinox season was good. It delivered numerous openings to South America which netted two new countries (more on that below).

Europe, the usual stalwart, delivered only a handful of good openings during the sporadic E season. When it was in it was pretty good, covering every corner of the continent. There is a lot of activity in Europe so that when there is a path we know it on this side of the Atlantic. Unfortunately I failed to work any new European countries. That said, there are only a few European countries that I have yet to work!

F2 paths that rely on a sustained high solar flux have been absent in 2023. Our geomagnetic latitude is higher than the geographic latitude due to the position of the geomagnetic pole. The average flux is rising at a steady and slow pace so there is hope for better next year. I say next year because as daylight fades with the approach of winter so do our prospects for F2 openings over the next several months.

Perhaps my disappointment is due to having experienced several good years of sporadic E propagation. Although 2023 has been poor, it was not worse than the worst I've seen since I returned to 6 meters in 2017. Propagation has its ups and downs, sporadic E is sporadic and sunspots come and go. 6 meters is the magic band and magic is fickle. The long anticipation of yet-to-arrived DX openings requiring a sustained solar flux of 200 tries our patience.

As I often say, if it was easy what would be the point? A challenge is what motivates station and skills improvement. It's us against nature and the laws of physics. Technical advances have made predicting and finding DX openings easier, but technology cannot manufacture openings. We learn, improve and measure our progress by our successes and our failures.

There was one very good aurora session this year. That netted contacts stretching across the northern US as far as Idaho. Although not DX, it was exciting to do well on aurora. That's one of the rare times I shut down WSJT-X and put the paddles to work. FTx modes are not compatible with aurora Doppler. We can expect more aurora propagation as the solar cycle peaks and then slides down the other side.

My log tells me that I made about 350 contacts on 6 meters this year. Most was via sporadic E. The total could have been much higher but I am not very interested in non-DX. I monitor most openings, scan the DX spotting networks and I will occasionally CQ into a seemingly dead band. Catching those brief and weak DX openings takes effort. Many times I am out of the shack when the band opens and I miss out.

New countries

My count of DXCC countries increased from 120 to 131. That's worked, not confirmed. On LoTW (the only way I confirm contacts) I have 120 confirmed. While I do operate CW and SSB when conditions warrant, all of my new countries are on FT8.

11 countries isn't much. A higher annual increment is unlikely until the solar flux increases enough to sustain F2 openings at this high geomagnetic latitude. As I said at the end of the 2022 season, I've reached the point on diminishing returns: each new one takes more effort than those that came before.

The most noteworthy new country I worked this year was New Zealand. I've heard ZL before but previous openings were too fleeting to make a QSO. Back in June, ZL1RS was not only workable, I was able to copy him pretty well for more than 20 minutes. I briefly heard but could not work two other ZL stations that evening. 

The other new one in the Pacific direction was FK8. They were in fairly consistently for several days in the spring. Then they were gone and they haven't been heard since. The solar flux hasn't risen too high for several months. On one of the days FK8 was heard, several strong Hawaii stations were rolling in but none that I haven't work before.

Another interesting new country was Angola. D2UY has been heard here and elsewhere in eastern NA quite regularly early in the year. On one day, and one day only, his signal was in for long enough to allow a QSO. There is not a lot of activity in Africa so every new country from there is an accomplishment. I heard and was heard in V5 and ZS but, again, there wasn't enough sustained propagation for a contact. Southern Africa was a common opening during the 1989-1990 solar maximum so there is reason to hope for better next year.

The rest of the new countries were in many respects uninteresting yet challenging in their own way. There was J8, V2, V4, FJ, OA and other Caribbean, South America and Central America countries that found their way in my log this summer. It should be an easy shot from here but, like for many parts of the world, there is limited activity on 6 meters from many of those countries and few have big antennas or pay close attention to the band.

For TEP-enhanced equinox propagation to the south, the new ones this year were OA and VP8 in March. The latter was a difficult contact since he had difficulty copying stations. Perhaps the local noise was high. I am running out of unworked countries in South America other than the rare islands. Galapagos Island (HC8) was worked by many locals. My attention was elsewhere and I missed it.

The final notable country was CY0S. That one was done on MSK144 meteor scatter. These were random meteors so it was very tough for everyone. A lucky few got through. We had no good sporadic E openings on this short path during the DXpedition.

Other stations heard and worked

Although not a new country, I was pleased to work OX3LX on a grid-pedition to northern Greenland. We don't often hear arctic stations on 6 meters. Although I don't enthusiastically chase grids and islands, working these unusual locations is always a pleasure.

There were numerous brief openings on long DX paths. Few delivered results but it was nice to hear them. These included:

  • Japan: only two stations worked. This year was similar to the first time I briefly heard Japan but didn't work them. This time I was watching but this was all I could accomplish. There were other evenings with a few signals form JA netted no QSOs. Nothing else was heard from east Asia.
  • Central Asia: We had one fleeting opening to UN. That's typical for us. Last year's bounty of UN stations was very unusual. Two stations called me but signals faded before we could complete the contacts. PSK Reporter told me that I was heard in another country in the region but I didn't hear them if they called me.
  • Indian Ocean: Early in the year I heard 3B8, 3B9 and FR, and had a partial QSO with FR4OO. I was being heard, as seen on PSK Reporter, but I wasn't always hearing them. It is likely due to a power difference.
  • A scattering of other DX: 9K, Z6, TR, among others. The only one of these worked was 9K.
  • W6: We had many openings to California this year. That's unusual. W6 isn't DX but a long path nonetheless. I worked some though most were stations I'd worked before. I pay close attention when I hear the southwest US and northern XE because they can herald openings to the Pacific, which are on the same western bearing.

How can I do better? 

We are all at the mercy of propagation. We can monitor, let others know what we hear or toss a CQ into the aether. Bigger antennas and higher power can help. However, the several decibels you can glean that way pales in comparison to the far greater range of propagated signal levels. On the HF bands you can see results every day with a superior station because the propagation is more consistent.

That does not mean station improvements are pointless. I already run the legal limit on 6 meters so all I can do is improve the antenna. I can replace the optimized A50-6 with a bigger (longer boom) yagi or put another antenna higher up on one of my two big towers, and I may do so, even though that'll get me 1 or perhaps 2 db. 

To go further I'd need a stack, both for gain and for a variety of elevation angles. That would require a new tower since I'm out of room on the ones I have. My priority is HF contests so VHF and other antennas must be placed wherever I can find room left for them. A new tower is unlikely since I'm not getting any younger and station maintenance will eventually become a burden.

I continue to consider the possibilities despite the obstacles. Since I'll soon sate my HF station objectives there will be time to devote to other projects. A long boom yagi in 2024 is a possibility. That's about all I can say at this point while I ponder the alternatives.

Closing note

I think this will be the last of my annual 6 meter reports. I've had a lot to report on for the past 6 years, and many seem to have enjoyed those articles. The rise of FT8 and FT4 was partly responsible due to its novelty and how it drew many hams to the magic band.

The diminishing returns I spoke about in the 2022 report about DXCC countries can now also be applied to these articles. There will continue to be individual articles on select topics about 6 meters, including notable propagation, new technology and station improvement, but not annual reports.

Update Oct.20, 2023:

My gloomy report about DX for the remainder of the year proves that my belated report ought to have been belated a little longer. I got an email alert on October 19 from the newest member of our local 6 meter buddy group (VE3KG) that stations from the Indian Ocean were rolling in.

Frantic activity followed, with most of us working 3B8FA, 3B8CW and 3B9FR. A few hours later I worked 7Q7EMH. But that wasn't all! That evening saw an excellent TEP opening to South American. I worked a number of Brazilian stations while my friends chased ZP9HTL, who I worked last year. Then today, October 20, VP8LP was worked by many stations in this corner of North America. 

I guess the magic band still has a few surprises in store for us this year! It is remarkable considering that the solar flux index is hovering around 130. The key factor appears to be a rare October sporadic E opening bridging to TEP. Both days saw strong signals from VO1 and VY2, and later from W4.

It's a good thing someone in our group was checking 6 meters or I'd have missed all of it. The buddy system works.

3B8, 3B9 and 7Q are new DXCC countries for me, bringing my total to 134. My 2023 increment is now 14 countries. TO8FH (Mayotte) was heard by others nearby but not by me. That would have been a fine catch. I am no longer quite so gloomy about 6 meter prospects in the coming days and weeks.

Tuesday, October 10, 2023

Inspecting a Bencher Skyhawk

This is not a typical product review. Indeed, it is really not a review at all. But as I inspected, cleaned, reassembled and installed the Bencher Skyhawk tri-band yagi I recently purchased secondhand I thought that it might be instructive to look at how an antenna ages and how it is designed. Nothing lasts forever, and problems crop up in the best antennas. They are totally exposed high up on a tower and endure everything nature can throw at them. 

Mine is an approximately 12-year old Bencher Skyhawk, a product which has since been transferred to DX Engineering. The new owners have made only a few small changes so that the antenna you can buy today is substantially the same as the original. My observations are mostly applicable to both. 

The electrical and mechanical design of this no-trap tri-bander is very good and reviews are almost all very positive. This is a fine antenna. That's why I bought it. But a 12-year old antenna is not a new antenna and time has taken its toll. That's one good reason you don't pay new prices for old merchandise. The resale prices of many products fall precipitously because they age poorly.

The Skyhawk is now on the air at VE3VN. Raising of the antenna was described in a previous article.

This article contains my notes and observations. As already said, this is not a review but a collection of my impressions from inspecting, assembling and raising the antenna. It was an interesting study.

Electrical design

A multi-band yagi is very difficult to design and optimize. This is true with or without traps. All the elements interact, so that even non-resonant elements, and even the tips beyond the traps, have induced current and their fields add to those of the resonant elements. There are no analytical solutions except in the most trivial of cases. 

An iterative numerical process is needed to solve the design problem. Before computer modelling, trap yagis had to be refined with great time and expense on a test range. Many manufacturers didn't even bother trying. I've done manual iterations using EZNEC to optimize small yagis but large ones like the Skyhawk require automated algorithms. For my own antennas, I most often take an already optimized design, whether one band or more, which I may tweak to meet my personal performance objectives.

Measurement notes: The SWR plots were made with a RigExpert AA54 in the shack, through about 40 meters of low-loss coax (except 2.5 m of RG213) and a 2×8 antenna switch. I checked the SWR at the feed point after it was raised but the measured impedance is affected by body proximity. The effect increases with frequency: little change on 20 but noticable on 10 meters.

The Skyhawk is optimized and it is a good design. Although I have not developed a computer model of the antenna, nor have I read an engineering review of it, it appears from its behaviour that some gain may have been sacrificed in favour of an excellent match across all three bands.

There's nothing wrong with that and it may be better for the majority. I tend to favour a little more gain. But that's a nitpick.

12 years of wear

Nothing lasts forever, and that includes antennas. Exposure to the elements takes its toll no matter how good the antenna's mechanical design. An inspection found problems, both small and large. These were corrected before it was reassembled and raised.

  • Rivets
  • Driven element spacer
  • Grease

I laid out the pieces of the antenna on the deck to do the inspection and element assembly. Rivets had to be removed from several elements to break into sections that would fit on the truck. 

It was an excellent opportunity to inspect how rivets perform over time. I was interested because I've never owned a yagi that used rivets and I didn't use them on my many home brew antennas.


Rivets have always struck me as inadequate for joining the sections of tapered element since they are quite small. I wondered if they were strong enough to last and whether the longitudinal stress on the element would accelerate failure of the softer aluminum alloy tubes. Disassembly of the antenna for transport gave me an opportunity to inspect their long term behaviour.

On the left is an improperly seated rivet head. I drilled out several of these to inspect the holes and insert new rivets. There was no obvious damage to the tubes or rivets in most cases so the protruding heads were likely due to mishandling of the rivet tool. The heads of all the rivets protrude around most of their circumference since it's flat and the tube is cylindrical. That isn't ideal but it seems to work.

On the upper right is a damaged hole where rivets were drilled out to disassemble the element. The sides of the hole are clean so it is possible that it was due to careless application of the drill. I left it as is and inserted a new rivet. The resulting bond was good since the rivet head is larger than the hole in the outer tube and the inner tube wasn't damaged.

Close inspection of the inner tube of one telescoping joint was enlightening. The hole is longitudinally elongated and the inside hole rim is roughly bevelled. The elongation is slight, probably no more than 0.020", and it is sometimes less (my calipers didn't fit very well for accuracy). This is what I expected since mechanical stress on the element is primarily longitudinal. 

The ⅛" diameter of the stainless rivets is a small, hard surface that can amplify the stress and push the softer aluminum aside. However, it isn't enough to be of concern so I inserted new rivets and continued.

The outer diameter (OD) of the smaller telescoping tube is less than the larger tube's inner diameter (ID). In both cases the wall thickness is 0.058", which is the most common US made aerospace alloy tubes used for telescoping yagi elements in ⅛" steps. For a press fit the wall would have to be 0.0625". That leaves a maximum gap of 0.009" when the tubes touch on one side. The tubes thus slide together very easily. Please note that the gap is less than it appears in the pic due to shadowing.

The antenna obviously works well despite the gap, although it bothers me a little. A press fit a poor choice for antennas since if you could insert the smaller tube it'll probably never come out again! Oxidation, stress and galling take their toll. For full circumference contact the outer tube must be slit and a gear clamp used to squeeze them together. That introduces two points of failure: the slit and the clamp. High quality stainless clamps are essential for reliability.

There are other ways of bonding telescoping tubes. A few of those which are applicable to element tubes were described in the blog when I was building my many yagis. Each method has its pros and cons, including rivets. Perhaps rivets aren't so bad after all.

There are many online resources that explain rivets and how they work, and how to use them. High tensile strength stainless rivets are inexpensive and widely available. It's well worth wasting a few to practice using the rivet tool. I drilled a few ⅛" holes in scrap aluminum and practiced until I was sure of what I was doing. The rivet tool came with the antenna.

It takes a lot of force to seat the rivet and break the narrow neck. I found it easiest to place the element and tool on a solid surface and press the upper handle with one hand while using my other hand to align the tool head with the tubes and to ensure contact between the rivet head and the tool tip. Inset is a closeup of properly seated rivets that were drilled out. You can see how the rivet bulb expands the shank upward to squeeze the tubes together against the rivet head.

All conductive joints in a yagi should be coated to prevent oxidation, prevent binding of telescoped tubes and assure conduction. Many hams skip this step and they should not. I've taken apart many "dry" antennas that required restoration. Some use dielectric grease, and it can work well if it doesn't dry out. A better choice is a conductive grease, which is essentially dielectric grease with a suspension of microscopic metal particles.

The manual states that the Bencher product was shipped with a product called Butter-It's-Not. The name is familiar but I've never seen it and I had difficulty searching for it online -- searches favour links to margarine sites! In any case there are many products. Whatever was used on my Skyhawk, all the grease had dried, leaving a residue of the suspended metal and whatever else. From the residue at least two different products were used.

I lightly sanded the exposed joints to renew them and greased them. Rivetted joints were left as is. The product I use is Noalox. I've had good success with it. The joints remain slippery after many years. I know there are better products that I have less experience with so don't take this as a firm recommendation. My squeeze bottle is so old that the plastic is cracked and repaired with clear packing tape. I've greases joints in countless antennas over the years. A small amount goes a long way. It's cheap insurance so don't skimp.

Driven element spacer

Feeding multiple elements directly from a common feed point puts them in close proximity. Without one or more spacers along their lengths the driven elements would strike one another when the wind is more than a light breeze. That would be catastrophic since the transmitter would fault due to SWR when they make contact.

The Skyhawk uses one spacer on each side of the boom to hold the three driven elements. Only the 15 and 20 meter elements are at risk of touching, and that's very unlikely unless the tubes are severely stressed. If wind or ice of such severity were to occur, you'd likely have bigger worries!

A common complaint in many online review of the antenna is that over time the bundle of driven elements develops an S curve. The reason is that the spacer gradually slides sideways on the 10 and 15 meter driven elements while waving in the wind. When it slides it tends to stay in its new position because the tube fit is tight. Only on the 20 meter element is the spacer trapped so that it can't move.

The plastic spacer is very tough but not indestructible. Apart from the unsightliness of twisted elements, the spacer and tubes are placed under increased stress. You can see where one of the spacers cracked, not surprisingly on the 20 meter element where the hole in the spacer is largest. I'm surprised that this product flaw has not been resolved.

My solution was to fix the spacer position on the 10 and 15 meter elements. A combination of small hose clamps and UV-resistant cable ties are lightweight and get the job done. It takes very little resistance to prevent the spacer from creeping.

I ventured to repair the cracked spacer rather than order a replacement. I drilled a hole and threaded a heavy duty cable tie through it. The tie braces against the element to bind the sides of the crack. 

When kept in the correct position, the radial stress ought to be low. The plastic itself is quite tough (it survived the crack). Time will tell whether my repair is effective.

Element-to-Boom clamps

The element-to-boom clamps have no way to fix the element centre to coincide with the boom. All the elements are insulated from the boom with bonded plastic sleeves and you simply judge by eye (or a ruler) as you tighten the clamp bolts. Perfect centering is irrelevant to performance but I do it anyway.

The driven element clamp alignment is more critical (picture is from the DXE manual). These three elements are split for feeding. Rather than one long plastic sleeve, there's a short one on each side of centre. The straps for feeding the elements in parallel are wide and carelessness can cause a short between the strap and the element clamp (which contacts the boom). I made sure the clamps were properly tightened to prevent the elements from creeping due to wind stress. 

I wish the design of the feed and clamps were better. However, I haven't heard any complaints on various fora of shorts developing over time. It must happen but perhaps it's rare. A raised lip or rim on the inner side of the sleeve would reduce the risk.

Another peculiarity (or benefit) of the clamp design is that there is no way to position or align the elements along the boom. There is a bolt that run through the upper half of the clamp and the boom. In a few cases the bolt does double duty to bond the boom sections and the boom compensator.

Alignment was excellent except for the driven elements. They are less than 2° askew. It isn't noticable except when you sight along the boom. The PVC element compensator doesn't age well so it is no longer straight. That isn't the fault of the clamp, and it doesn't matter.

Boom attachments

The antenna has no boom truss despite its 24' length and with the longest (heaviest) 20 meter elements mounted at each end. Despite that lack the boom is pretty hefty and sags very little. You can get an idea from the view along the boom towards the reflector end.

You really don't notice it from the ground. Aside from aesthetics there is a question of how much severe weather load the boom and mast clamp can tolerate without the truss. The antenna is engineered for high winds and some ice so I am not especially concerned. But I do wonder how it'll fare in our harsh winters and occasional severe ice storms. On the other hand, elimination of the truss keeps the mast free of obstructions.

When I removed the antenna from its previous owner's tower I was unfamiliar with the design of the mast clamp. I automatically loosened the saddle clamps and sent the antenna into the hands of the ground crew below. The u-bolts don't pierce the saddles so it isn't difficult to drop the loose saddles.

I later came to understand the two-part design. The mast side of the assembly can be left on the mast for both raising and lowering. The upper nuts on the boom side of the clamp fit into the keyholes of the mast plate and drop into the slots below. When that's done the antenna is secure. The lower nuts can be threaded on and all 4 bolts tightened. The reverse procedure is performed for removal of the yagi.

Keyhole mounts are found on all types of hardware, but this is the first time I've seen it on a yagi. I like it. 

When we raised the antenna onto my tower, the mast clamp was already installed and all I had to do was direct the nuts into the slots and have the crew lower the antenna an inch. There was no fussing with multiple saddle clamps (often with short u-bolt legs that require near perfect alignment) to secure the load. 

Balun and coax

The balun supplied by Bencher is more compact than the one included by DX Engineering. It appears to have weathered well. I can't say how well the PVC electrical box for DX Engineering's common mode choke will survive other than to note my poor experience with the same enclosure used by Balun Designs.

The balun fits snugly under the boom using special brackets to keep it centred and with adequate space for fitting and weather proofing the coax. I tested it with a dummy load on the workbench and it tested fine, with inductive reactance gradually increasing with frequency due to the pigtails. I do not have a fixture for testing common mode rejection. The quantity and type of ferrite beads determine its performance.

The location of the feed point is not convenient for attaching the coax and rotation loop. The Skyhawk includes a boom bracket to support the coax and thus reduce stress on the connector and balun. Unfortunately, that puts the coax even further out. It isn't very far but you must be comfortable leaning out from the tower to do the work.

Since the feed system is below the boom the coax is routed above the boom. The rotation loop is located on the opposite side of the mast and paired with coax dropping down from the 6 meter yagi at the top of the mast. It is possible to put the rotation loop on the same side of the mast by routing it down on the outside of the driven elements, except that the coax has to be kept rigid as it passes the balun to avoid jostling during rotation. A few more feet of coax makes a cleaner rotation loop on the far side of the mast, so that's what I did.

Tube caps

The antenna comes equipped with plastic caps for the boom and element tips. Only a few of the elements had caps on my Skyhawk. I prefer no element caps so that water can freely flow out should any get in. 

I have the boom caps and I put them on. Insects are a greater risk in booms since they are large. It's a trade off. Depending on local conditions it maybe sensible to cap all of the tube ends, or none of them.

So far...

I'm happy with the Skyhawk. The first contact was with VK9LAA and I have made many other DX contacts since, including several of the current DXpeditions. It's easier and quicker to turn this antenna than the prop pitch driven big yagis. Although it is not my best antenna on the high bands, it is usually sufficient to make the contact. The agility it brings to my contesting is very welcom. 

For most hams it would be a fine antenna on its own. Just make sure the tower and rotator are up to the job. There are many elements and that adds up to a high wind and ice load. 

Another consideration is the price. There are few antennas I would buy new and this one is no exception. Material prices have skyrocketed over the past few years and that makes up a substantial portion of the manufacturing cost. The Skyhawk is not out of line with the prices of similar antennas. I don't see many available on the used market. I buy my antennas used or I build my own, with infrequent exceptions.

Direct comparison with the TH6 hasn't yet been done since their gains will be close and the confounding factors many. 1 to 2 db of difference is difficult to reliably discern by ear or S-meter on receive. On transmit it's a different matter: the extra gain of a no-trap design will be noticed. This is often also true when comparing my stacks to smaller yagis. The contest pile ups are deeper and they last longer.

Most hams are fortunate to have one yagi for the HF bands, and two is uncommon. Easy comparisons are impossible. Hence the reliance by some hams on myth and lore, unreliable opinions and advertising. We do have a tendency to convince ourselves that whatever choice we make is the best choice because it is our choice. Physics begs to disagree.

Thursday, October 5, 2023

Rearranging Yagis

No long ago, I described that during this fall's antenna work several yagis would be moving or removed. You can see a graphic of the plan in that August article. Here it is in words:

  • Remove the TH6 from the rotatable side mount halfway up the 150' tower
  • Move the XM240 from the Trylon to the position vacated by the TH6
  • Raise the recently acquired Bencher Skyhawk onto the Trylon

Later in the article I'll discuss why I'm doing this. But first I'll describe what was done.

Not including preparation and cleanup, the latter two items were accomplished in one day with the help of Alan VE3KAE and Dave VE3KG. I had hoped for one more helper but we made for it with mechanical muscle.

Since making my annual plan, I had a change of heart and the TH6 was moved rather than removed. I spent a couple of hours in the workshop to make a fixed bracket for the big tower. I installed it a little above the rotatable side mount. With Alan's help a week earlier we lifted the TH6 the short distance to its new perch. It is fixed to the south (170°). It's been here before. That freed the rotatable side mount for the XM240.

I have written so much in this blog about the various methods for raising yagis that I won't repeat myself. Do a search of the blog and you can read all about tram lines, tag lines, pulleys, vehicle power and much more. One picture will suffice for this article, of Alan posing with the XM240 at the tram line's launch point.

The only significant difficulty was on the smaller tower, the 70' Trylon. Being close to the house rather than in the middle of a hay field like most of my towers, there are obstacles. The yard area of my large property is very pretty with many trees, but they pose a challenge for raising and lowering antennas. For one thing, they grow! The challenge increases every time I lift or lower a yagi.

The XM240 and Skyhawk are quite large. Each weighs about 75 lb; the original XM240 is lighter but this one has been strengthened per W6NL. The antennas must land or be lifted a distance from the tower so that the elements and boom clear the overhead cables and several large and growing larger trees. Steering with tag lines is critically important. Finesse is needed more than brute strength, however the latter is needed when the yagi is close to the ground and far from the tower base.

I will emphasize one very important lesson about tag lines. Steering a yagi requires two tag lines, one on either side of boom centre. They are either attached outside an element clamp or prevented from sliding with a clamp or other means, and be easy to remove once the yagi is attached to the mast. 

Two tag lines sounds like a job for two hams. Wrong! No matter how many times I have tried it over the years with two people, it is almost always impossible for them to perfectly coordinate their actions and intentions. If you don't believe me, try it. But try it with your yagi and not mine! Element tips are fragile.

Instead we divided the work. One person drove the vehicle for lifting and lowering power, one controlled both tag lines and the third person relayed communications between the driver and the handler of the tag lines. 

The latter job went to me since I have the most experience with the delicate matter of steering yagis. I was also highly motivated since it would be my own yagis at risk! Communications was key since the vehicle was in the driveway and out of sight of us, and the driver could not see the tower or the yagi (trees and house blocked the view). 

It was entertaining and tense at times but we got it done without damaging the antennas. For added excitement, we had to avoid bumping the wireless internet radio mounted near the top of the tower. Knocking it out of position would involve a costly service call. 

I climbed the tower once to uncouple the XM240 from the mast and again to attach the Skyhawk to the mast, all while the vehicle was holding the yagi's weight. I won't get into the rigging details since, even with pictures, it is likely to be more confusing than enlightening. The rigging allowed the vehicle (my lawn tractor to lower the XM240 and a car to raise the Skyhawk) to move in a wide compass of directions while the line going up the tower stayed in a fixed position where it was clear of trees, tower and internet radio.

The pictures show the successful results. The antennas checked out and I reconfigured my software to reflect the changes. To my chagrin, that uncovered a couple of bugs that I tracked down and successfully fixed that same evening. 

Over the next several days I finished the job of boom trusses, dressing cables and weatherproofing. Late September and the first days of October were unusually warm and sunny. Temperatures soared to 30° C. That's record breaking for our northern climate at this time of year. 

As I write this, the one outstanding task is hooking up the TH6. The Heliax is connected by I still have to reconfigure the antenna switches to free a port for it. Other than that, the XM240 and Skyhawk are fully operational and being used on the air. It's auspicious that my first QSO with the Skyhawk was VK9LAA.

In a forthcoming article I will talk about the Skyhawk in depth since I found the antenna design to be quite intriguing. It is well worth a close look. The XM240 I've owned for quite some time, from before I moved to this QTH. I bought it when it became available during the planning stage while I continued to live in the city. After the move to this QTH, it has been on a variety of towers:

  • Onto the Trylon when it first went up the first winter
  • Moved from the Trylon to the top of the 150' tower when it was built the next year
  • Removed from the big tower and put back on the Trylon
  • Now it has moved from the Trylon back to the big tower, but side mounted

This is all fine, but by this point many readers must be thinking: why? Why keep moving these large yagis from one tower to another? Surely it's better to decide what I want or need, put them up and keep them there. 

There is a method to my madness. I am not intimidated by big antennas and towers, and I have the experience (and time) to undertake these frequent changes. I choose where I want an antenna based on the state of station construction and my operating objectives. The latter is primarily contests. For daily operating there is no great need for so many towers and antennas. Of course many non-contesters do it anyway, just because they can and it can be a lot of fun. 

I'll take you through my thinking so you can better understand why I've taken the trouble to do all this work. While you read, keep in mind that my primary operating activity is contests. Several of these points were documented in the 2023 station plan that I published in January.

Traps: Traps in yagi elements have loss and narrow the SWR bandwidth. I have long yearned to free myself of them but the reality was that I had them and they filled a need. I've reached the point where I can mostly eliminate them. The Explorer 14 was sold last year and the TH7 sold this year. As I explain below, I decided to keep the TH6 to fill an ongoing need.

Solar maximum requires more high bands agility: 10 and 15 meters conditions are great and they're going to get even better. With only so many hams and hours in a day, it is no surprise to find increased activity on 10 and 15 meters, and less on 20 and below. For the next few years it is valuable to have more antenna options on 10, 15 and 20 meters. For the coming contests there are now 3 antenna choices on those bands, and the ability to split the stacks.

Rapid access to W4, Caribbean, South America and Central American: Several years ago, before building the rotatable side mount, I fixed the TH6 south. It's back but a few feet higher. Skip is shorter when the solar flux climbs and there are more southern US stations available to be worked on the high bands. It isn't a high traffic path so it typically isn't desirable to point the better antennas in that direction. With a click of the mouse, the TH6 provides instant access to the south for DX multipliers and the southeast US. Once the targetted station is worked, another click returns the operator to where they were.

Prop pitch motors are slow: The upper yagis of the 20, 15 and 10 meter stacks and the 3-element 40 meter yagi are turned by prop pitch rotators. They are poor choices for rapidly working multipliers. It is more profitable to use them for running and long DX openings. I turn them to a direction and leave them there for a long time. The smaller and lower yagis are used for less productive paths, shorter paths (e.g. US) and multiplier hunting.

Unfortunately, the changes I've made are not all positive. Trade offs were unavoidable. These are the most notable cons of the new arrangement:

  • Reduced capability on 40: Pre-sunset and post-sunrise the DX elevation angles tend to be higher than during the night due to D-layer absorption. The XM240 at half the height of the 3-element yagi often outperforms its big brother at those times. Since the side mount only allows 130° coverage from southeast through west, I may suffer a deficit to, for example, Europe in the late afternoon. It can still be used effectively in the morning towards the Pacific and South America. I plan to replace the XM240 next year with an antenna that has more complete compass coverage and that has no loading coils. I can live with the XM240 for one more year.
  • Potential interference on 20: With so many yagis there is the ever present risk of destructive interactions. The 3-element 40 meter yagi was expressly designed to avoid pattern degradation of the 15 meter stack. I have not modelled the interaction between the tri-banders and the stacks, however I know the TH6 and Skyhawk won't interact because the TH6 points south and the Skyhawk is to the west of it. Due to the respective heights of all the yagis, I suspect the only significant issue may be on 20 meters with the lower yagi of the stack. Modelling the scenarios will have to wait for inclement winter weather when I'll have more free time.

I believe the negatives are far outweighed by the positives. At least for my style of operating. The 40 meter issue is short term since I plan to replace the XM240 with a better antenna, hopefully in 2024. Coil loaded elements, like traps, increase loss and decrease SWR bandwidth. Yagis suffer more than single element antenna because they are inherently high Q antennas and the radiation resistance is low.

The agility I've gained on the high bands is worth the risk of yagi interactions. Pattern degradation depends on where the yagis are pointed so it will occur only some of the time. In any case, I don't require ultimate performance from the tri-band yagis since they will be mostly used for rapid multiplier hunting.

With this big job out of the way I can focus on several other antenna projects. I'll write about each of them as those projects come to fruition.