Radio W4KAZ

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Field Day 2018 – 1B NC de W4KAZ

The normal group of Field Day scalawags were in the wind for 2018.  N4GU was uncertain if the QTH from 2016 and 2017 would be available.  N4YDU took up N9NB’s offer for FD at Ted’s QTH in VA foothills.  I was also kindly invited, but decided that I didn’t want to drive quite that far, despite the nearly ideal location.  I do love me some VA mountains.

Photos from FD2018: http://w4kaz.com/images/fd2018/

For 2018 I took exit ramp #3, and went with the backup backup plan.  Operated 1B at a campground near Wilmington NC.  A nice easy drive, with a couple of easy on/off stops along the way to stretch out the body parts complaining loudest.  That made the drive tolerable.   Also made it into a mini-escape, leaving home QTH on Thursday with a return on Monday morning.

Weather conditions[i.e., heat] soon had me thinking I’d have been better off in the VA mountains, but after acclimatizing to “swamp butt” conditions, it was fine.  When I sweat enough to remind me of living on the South coast – its pretty darn sticky.  Usually not quite so bad in NC, but it happens enough to know to be prepared.  Lots of water and gatorade.  Thursday afternoon was the worst of it though.

Friday morning was spent doing a bit of unrelated recon.  Friday afternoon I laid out the antennas and supports, and some more unrelated area wide explorations.  WX on Saturday dryed out some, and there was a nice breeze that picked up from the start of operations though early evening.  Never a drop of rain, just temps and humidity in the 90’s.  Just like being back in good ole Bigg Swampy(SE Louisiana).

Antennas:

2018 was a time to test some antenna ideas.  I built a 2 band triangular yagi for 20m/15m, based on article by Herb,N4HA as published in June 2018 QST.  I kept to the published dimensions(mostly) but fashioned the driven element(s) from 300ohm ladder line.  For supports I used a mast from Henry, K4TMC as the support for the drive element/apex.  The tails sloped down to connect to the reflectors, and those ends were supported by 2 masts cobbled together by combining a Shakespeare Wonderpole on top of a section of 4 foot mil surplus mast.   Simple, and easier than I expected.  This antenna was fed with 300 ohm ladder line run to a tuner rather than coax.

40m was a simple inverted Vee supported by a Spiderbeam 12m telescoping mast.  Note: Simple does not mean “easy”.

10m was an afterthought.  After struggling with the 40m dipole-that-wouldn’t, I had a relaxing breakfast and gave some thought to 10m.  Had plenty of time, so may as well.  To get on 10m I made a dipole by cutting a couple of equal 8.5 foot lengths of wire and constructed a “FD style” center insulator from a pair of cable ties taped together.  Used a “composite” feedline – a ladderline drop to a 1:1 unun and a short coax run into the tent.  I had a length of ladder line about 25 feet long so the 10m dipole was up about 23 feet.   At the end of the ladder line at ground level I plugged the ladder line into a 1:1 unun, and ran the last 30 feet or so into the station with coax.  From start to finish this antenna took about 30 minutes to put up, including cutting legs and twisting it all together.

No antenna at all on 80m.  Decided I’d have enough business on 20m & 40m to keep occupied, and figured on sleep rather than a night of 80m T-storm QRN.  😮

Now, about that 40m Vee.  The antenna that would NOT.  Still not certain where the problem was, but it had an issue in one of the feedlines somewhere[update-think one of the legs has broken wire].  Far too much time was wasted raising and lowering the antenna trying to debug the issue.  Lesson1: Always have an alternative.   Lesson2:  Don’t dick around debugging when you have the alternative at hand ready to go.  Lesson3: Save debugging for down time.  Lesson4:  Read Lesson1 and Lesson2 until they really sink in.

Operating:

Once the CQ’s started, there were plenty of QSO’s to log.  Saturday was a bit slow at first, but I got a better rhythm in the evening.  Was tired though, and sacked early, including a 45 minute nap at 5pm in the nice cool breeze that came up.  Also got up early Sunday, 5am-ish.   Sunday morning was quite a bit of fun, right up until my keyer interface died around 11am.  So I finished the event with a bit of lackadaisical SSB, mostly S&P.

Camp:

The Cabelas tent goes up easily.  My only regret is not getting one of the larger sizes.  It has room for setting up a table for the station and also for a cot along the opposite side.  But it is a bit cramped.  Next time I do this I think I will use a screen tent for the station and the tent just for snoozing/bad wx.  Also, the ideal site would allow for the tent to use an overhead spike support and avoid the need for the center pole.

Overall a big win.  Keeping the ants away…..the real challenge!

 

 

2017 FD @ N4GU as AA4NC – Still No Will

The 2017 Field Day is in the bag.  Operated with the group as AA4NC at the farm of N4GU’s XYL.  Showing a surprising lack of judgement for a second year in a row, AA4NC again allowed us to use his call, despite a shoebox full of notices from last year’s operation.  Still No Will….but N4GU, N3ND, N4YDU, N9NB, W4BBT and W4KAZ all on the air.

2016’s as-yet-undocumented FD last year was done as class 2A, while for 2017 we rode with class 3A.  Given the improved conditions on 15m/10m/6m, that was quite a bit less boring than I expected.  Gave N4YDU grief for wanting to run that third station for the high bands, but they were maybe the money bands this year.  Great call on N4YDU’s part.  With so much activity on high bands through the evening and mid-watch, 80m under-performed.  Boooo.  Hoooo.

Stations:

2017 FD - 15m/10m and 6m stations

2017 FD – 15m/10m and 6m stations

2017 FD - The REAL Night Shift

2017 FD – The REAL Night Shift

2017 FD - The "40m station"

2017 FD – The “40m station”

We ran 2 stations on N4GU’s 1kw generator, and ran the third station and VHF stations on deep cycle batteries.  The two stations on generator power were Elecraft K3’s, and the battery station was a Kenwood TS-590.  VHF was run on the Kenwood until N9NB arrived with an Icom 703.  Battery power for the 590 was two deep cycle batteries paralleled and connected to a solar cell, and the 703 was on a single deep cycle battery.

Antennas were a Frankenstein ??ta33M?? tribander for 10/15/20@35′(split via triplexer), an OCF mostly for 40m@34′, an 80m dipole@~45′, a 10/15 fan dipole @ 30′,  a 20m vee dipole at 24′ and a hastily erected 40m dipole @ 40′.  VHF station used a 5 element 6m yagi @24′.  Most of the antennas were strung by late Friday afternoon, leaving time on Saturday morning for testing and a last minute wild hair(the 40m dipole.)

Operating:

Given the strange conditions on Sunday morning, the dipoles played quite well as supplements to the tribander on 15m and 20m, with good signals from New England often better on the dipoles.  The tribander won on stations out to the west of 9-land, and about equal in the middle grounds between.

For my part 15m was the best news on the subject of propagation.  20m and 10m were close behind.  All three bands were very productive.  6m even coughed up QSo’s this year, with 160+ Q’s logged.  The night shift on 80m was a bit sluggish, probably many stations stayed on 20m later than normal.

Something must have worked correctly, event with W4KAZ constantly changing the function key settings on every N1MM computer attached to an HF radio.  Despite KAZ’s  best efforts at disabling the dread “Enter Sends Mode”, almost 3500 Q’s were logged across all of the stations.

WX:

Friday afternoon the WX forecast of rain was quite thankfully incorrect.  Instead there were crystal clear blue skies and a slightly gusty wind.  The wind helped keep the insects at bay, and cooled the crew off a bit.  Saturday morning was overcast, but remained dry right up until a 6pm shift change.  As soon as the new shift sat at the stations, the wind began gusting, enough to slide the camp chairs across the cement floor as if of their own volition.  Enough wind to make ops press down on tables to keep them from tossing radios about like so much flotsam.  The rain soon came in buckets, making the nice covered carport seem like luxury FD accommodations.  The nice 30 minute storm cooled things down and brought the insects from hiding for most of the evening.  Things remained cool enough overnight that a light rain jacket was perfect for both staying warm and fending off the creepy-crawlies.

Food and other:

Many thanks to Mike’s XYL Sherry, who kept us stuffed to the gills over the weekend, and caused disputes to break out over a certain blueberry dump cake.  Also many thanks for allowing us to invade her domain for the weekend and play radio geek.  Good QTH, a good crew of ops to work with, and entirely too much fun.

Open Sleeve Dipole, Tribander Plus

Tribander Plus?  Plus what?  Friends with benefits maybe?

Back in 2002 or so, references to the “open sleeve dipole” sparked a curiosity in the topic.  Very few web references were available back then(in the internet dark ages).  The article that initially tweaked the curiosity was N6LF’s article “A Wideband 80-m Dipole”, which built upon an earlier article by K9AY from 1995. The open sleeve idea is also mentioned by Bill Orr, W6SAI.  Current ARRL Antenna books have information on this topic in Chapter 10, but that was not available in 2002.  Not much else, but there are a few engineering references going back at least as far as 1945.  None of which were readily available a decade ago.  Time marches…..

Recently Joel Hallas, W1ZR, ran a couple of articles on the subject in QST. This article on adding 6m to a tribander duplicated an idea I had myself, although I was more interested in the possibility of easily adding 17m to a tribander. W1ZR uses the term favored by K9AY, the “coupled-resonator”, from K9AY’s article “The Coupled-Resonator Principle: A Flexible Method for Multiband Antennas” in the ARRL Antenna Compendium #5.  K9AY’s “coupled-resonator” terminology is more precise and accurate as a general description of the principle for amateur uses.  Yet my own fuzzy gray matter remains wed to the term “open-sleeve”, which is really an example of the general principle in a narrow usage.

More references are available today: NQ6K with a well written treatment used as a sloper, and DK7ZB has a good page briefly explaining the concept. Plus a new ARRL Antenna book(Chapter 10.4-10.5) entry. This is the idea in general terms.  Placing another wire in parallel and “close” to another dipole allows you to feed the antenna at two different resonant frequencies.  The feedline is attached to the longer dipole only, the second(and/or third) wires are excited parasitically.  By carefully spacing the two wires, it is possible to get a 50 ohm match for both resonances.

Pretty handy idea….but….

O’course, the trick is in the details.  Getting the spacing correct can be tricky if you are intent on that 50 ohm match.  EZNEC modeling is simple enough for this gray cat, and it is easy enough to fiddle the dimensions of the second dipole and its length to get that 50 ohm match.  It turns out you can also add a third dipole too, but the spacing dimensions become a lot more critical.  Much like a fan dipole.

Generally, it seems that the higher frequency dipole winds up being slightly shorter than it would if it were a single dipole, and that is more pronounced as additional resonators are added.  Harmonic combinations also seem more sensitive to dimension changes affecting feed point impedance.  [NOTE: ARRL antenna book, chapter 10.5 contradicts my note of “slightly shorter”, indicating the dipoles might need to be slightly LONGER due to the capacitive coupling.  Hmmmmmmm.  Mayhaps wire spacing….?]

Outside the box of conventional

But what if we do NOT concentrate on the 50ohm match? What if we wish to use a balanced line feeder and a tuner, like for, oh, maybe a multi-band wire antenna for FIELD DAY?  Something with improved and predictable radiation patterns over a non-resonant doublet?

That seems to be a pretty good option.  The dipoles are resonant, even if they show an impedance that is not 50 ohms.  Resonance does not imply 50 ohms….that is just a happy convenient choice since radios are designed to have input impedances coincidental with the general impedance of a half-wave dipole fed in the center. But an end fed half wave is just as resonant even though the impedance is nowhere near 50ohms.

With resonance the radiation patterns are more predictable, and there are less likely to be odd lobes as might be the case with a generic doublet.  In the past we have used several different options for loading up a doublet on multiple bands, with mixed results.  So in April I decided to cobble an open sleeve antenna together and try it out for a few days.

Models?  We don’ neeed no steeeenkeeeng models…

No, but in this case the model was interesting.  Going for a decent compromise of performance versus convenience, a bit of EZNEC tinkering showed that a 40m/20m/10m  combination of elements might produce decent  radiation pattern results for four bands. Input impedance?  Maybe not so ideal.

The plan modeled was using 18ga ladderline for the mid-section, and attach legs on the ends for the 40m resonator.  Spacing the 10m wire at about 1.5 inches in the model produced a more stable impedance curve for 10m, so rather than just taping the 10m wire to the ladderline, small spacers are used.  Radiation patterns for 40m and 20m resemble normal dipole patterns.  The 15m pattern is normal for a 40m wire pressed into 15m service – a dipole pattern that is  breaking into two lobes with a nulled lobe perpendicular to the dipole.  The 10m pattern without the 10m element would show the same butterfly pattern.  Adding the 10m element makes a huge difference on both the radiation pattern and the feedpoint impedance in this instance.

Actual antenna

The antenna was constructed from a segment of 18ga 450 ohm ladder line and some scraps for 14ga thhn laying about.  The ladder line section was from a 20m folded dipole.  The parasitic radiators modeled best if the were slightly shorter than they would be in a single wire dipole.  So the ladderline was shortened to the model’s 20m dimensions.  Enough wire to complete the 40m legs to model dimensions was added to the fed wire. Dimensions were pulled directly from the model for all legs – no other trimming, and the pieces stitched together.  [No point in trimming since the intent is to feed the antenna with ladder line to a tuner, rather than obtain a 50 ohm match directly.] The 10m radiator was attached to the ladder line via a few sections of PVC pipe cut into 2 inch lengths for use as spacers.  These spacers were drilled and attached to the ladderline via cable ties and tape.  The 10m element then is attached to the outside of the spacers, away from the ladderline.

In hindsight, adding the 10m element with spacers is problematic for a “portable” antenna.  The spacers complicate storing and deploying the antenna.   Just taping the 10m element to the ladderline is probably worth the efficiency trade off – unless you have real reason to expect 10m to be significantly better than it has been of late.

The end result is a dipole that exhibits the radiation pattern of resonant dipoles on those three bands, and also is relatively easy to load on 15m.  The model show the 15m pattern is “butterfly” shaped, which is normal for a 40m dipole pressed into service on 15m.

Workee workee

It is now hung at almost exactly 30 feet height, and shows the expected performance on those four bands.  One of the major lobes on 15m must be favoring Europe, as the EU stations are better on this antenna than anything else in the yard.  20m and 40m are equivalent to the other dipoles.  Not much 10m activity heard yet, so no idea there.

I expect a similar fan dipole could be used in the same manner, where all of the dipoles are physically attached.  My experiments with fan dipoles was in an attempt to match to 50 ohms.  Very difficult to do for more than 2 bands.

Another caveat to be aware of is that combinations of dipoles at widely separated frequencies, i.e., more than a harmonic, will tend to have “unusual” patterns.

There were too many outside issues to allow much butt-in-chair time in one of my favorite contests, CQ WPX CW. But enough of a chance to try the antenna out, and I’ happy with the results.  The butterfly lobes on 15m must be in very favorable directions.  During the contest Europeans had huge signals, and I worked three JA stations on Sunday afternoon….which are certainly the only JA’s worked from this QTH this decade.

I’ll not leave it up permanently, because running the ladder line into the shack always raises RFI issues.  This antenna is RFI “cranky” on both 40m and 15m inside the shack, but thats probably more an issue related to the kludged feed-thru into  shack and the general in-shack rat’s nest of wiring rather than the antenna.  It is worth testing out for a bit longer though.

Maybe a few RFI issues will find resolutions during the testing.

Interesting open sleeve(coupled resonator!) ideas….

NQ6K  slopers…. http://findatlantis.com/wiki/index.php/20-15-10m_Triband_Sloper

N6LF Wideband 80m dipole:  http://rudys.typepad.com/ant/files/antenna_broadband_dipole.pdf

Dan Levin, N6BZA and Marty Levin, W6BDN: Notes on phase delays when stacking: http://www.k6if.com/c3_stack_article.html

 

The Evolution of a 160m Inverted-L with FCP(long version)

Saga of transitioning to K2AV’s FCP(folded counterpoise)

(Updated 02/28/2012 de w4kaz)

(Updated 09/26/2016 de w4kaz, current links & match network schematic)

(Updated 05/31/2018 de w4kaz, add/edit links to newer K2AV FCP page)

TopBand?  Wazzat?

A saga of switching from raised radials to a version of the K2AV FCP for a 160m inverted-L.

The whole idea of operating on 160m started as curiosity.  Before 2005 I had never operated on 160m.  Ever.  I had listened some, but never keyed the transmitter other than to experiment with arcing capacitors and high levels of SWR.  But it generally seemed like it would be fun, so give it a try to find out, right?

After looking at a couple of locations in the yard, it seemed like there just wasn’t enough room to !easily! pull up an inverted-Vee, or other crooked dipole of such unusually large size.  Tall trees out-the-wazooo in the yard, but spaced closely, so it is difficult for long pulls. So there is an emphasis on easy, because it is an important consideration.  Any antenna that is a pain in the ass to maintain is more likely to be out of service at any given moment at the KazShack qth.

There is a great spot for a vertical rise of about 70 feet, so that seemed to be the ticket.  But verticals have their own downside.  Radials – bleh!…Ick!…Ptui!  But any antenna is better than no antenna at all, so that’s where we get sucked into 160m madness.

The first preference was a top loaded “T”, but the useful supports are not arranged in a good pattern for that choice. There was just no way to stretch out the top-hat of the T.

The supports are arranged in such a way that an inverted-L is the logical choice.  So a slightly long inverted L was the winner since it 1) fit into the yard where the trees line up, and 2) lends itself to capacitive matching if made slightly long.  The result was an inv-L  with the vertical section that goes up 70′, then across 40′, and across again in a different direction for another 50′.  Approximately 155′(47m) of wire total length.

That leaves the radials.  Buried radials just were not going to happen.  Far too many tree roots and stone in the back yard, and no grass at all.  What then is the nascent TopBander to do?

The Early years

The first Inv-L install circa 2005 had four elevated radials of equal length, about 37′ each.  All were tied together and loaded via a coil at the base of the antenna.  No chokes, and no decent matching network.   In this incarnation, antenna performance was poor.  Even loud stations were difficult to work.  Heard no DX.  No surprises there.

The first “improvement”  circa 2007 was to add 12 random length radials, a 1.5:1 step down unun(W2FMI design), and a coaxial choke wound from about 70′ of rg-58 wound on a PVC garden pot.  The performance improvement, while not quantifiable was immediately noticeable.  Stations became easier to work on a single call, and I was now able to detect the whispers of DX stations.  A new K9AY for RX was also added to the mix just before these changes to the TX antenna.  It also appeared that the improved TX antenna was now hearing most of what could be heard on the K9AY, although the K9Ay has a much lower noise floor and is usually much easier on the ears.

The Intermediate

Radials were added incrementally from 2007 through mid 2010 until there was a total of about 30.  The original four 37 footers were the longest, and there were another four that were approximately 27 feet long.  Everything else was a mish-mash of random lengths, added in pairs to the available trees in the area.  Somewhere along the line(2008) I also added the capacitors required to get a good match at the base of the antenna, and have a nice low SWR both at the antenna base and at the shack-end of the feed line.  And the nice narrow SWR bandwidth that accompanies such.

Performance of the final well-matched radial version of 2010 seemed to be quite good in comparison to the earliest version.  In 2009 and 2010 it was possible to run stations(low power) in the 160m contests, and Q’s were made more often with the western US, as well as a handful of DX stations.

Before any other changes were made, I took some signal strength measurements in late 2011 using the K2 as field-strength meter, with the FT-920 as transmitter.  The test configuration was 1) transmit full power from the FT-920 on the TX antenna at its lowest SWR point, 2)RX on the K2, using a dummy load at the end of a 7 foot jumper cable.  dummy load hanging off edge of desk.  K2 attenuator on, rf gain at max.

Using that configuration:

  • 100w into the transmit antenna produces S-5 on K2 S-meter
  • 100w into separate dummy load produces audible S-zero on K2 S-meter

As poor as it is, that reading is the best actual measurement available, from what in my opinion was the best of the radial configurations.  Taken in early December 2011.

Decision Time

In 2009-2010, K2AV began discussing an idea he had for solving the small-lot-on-160m problem.  Based on his modeling and studies of ground losses, he reasoned that a single counterpoise might be a solution that would work for space limited locations.  He determined that a counterpoise that was 5/16th wavelengths might show useful current cancellations if it were strategically folded, to help with the problem of ground losses.  So evolved the “5/16th wave folded counterpoise”, now being generally referred to as  “516 FCP” or just as “an FCP” . The idea seemed to have a lot of merit, but being a serial procrastinator it took some time for me to get off my hindquarters and make the changes to try it out.

In early 2011, K2AV gave me one of his isolation transformers, as well as an inductor.  Their implementations of the FCP at K2AV’s and W0UCE’s qth required  additional inductance for matching(hence the inductor). They also discovered that the isolation transformer was a necessity to obtain good field strength results.  The transformer design is beefy enough to handle their high power operations.   The design of the FCP has gone through some evolutions/refinements, and the design K2Av is recommending was originally field tested at his own qth in the 2011 CQ160m CW contest with low power, and with excellent results.

K2AV style FCP System Installed

My own original intent was to install his isolation transformer into my original system and transition to the FCP.  Curiosity compels me to wonder what sort of improvement the isolation transformer might have provided on its own in the old system.  That test never happened, but it is really just a matter of curiosity.  It would still be good to know if the transformer would have made an improvement in signal with the radial jumble.  I expect the choking on the radial system was less than ideal,  far less than what was necessary, and the system probably was subject to higher losses because of that. That transition never happened, so I missed having the new system ready for ARRL DX. Impatience won out when an opportunity to do the work came up.

In the week after ARRL DX, the radials/coil were removed and K2AV’s folded counterpoise and isolation transformer were added to the antenna.  [NEW link: K2AV FCP home page]  A new junction box was built to house the isolation transformer and matching network.  K2AV came by with his analyzer, and we spent a morning giving the system a look-see.  As it turns out, the same value of matching capacitors were suitable for use without modification, and the inductor was not required because my inv-L is long.  Matching the system was as simple as adding capacitance until a match was found.  A large value air variable could be used to find the required match in less than five minutes, then replaced with capacitors suitable for handling the currents.

My own matching network is a group of HV ceramic caps in parallel[Obsolete, probably unavailable, 2016/09/25].  These are mounted on a board that allows switching some of the capacitance out to move the resonance up the band.  The switch board will also allow switching to a different vertical element, but that feature won’t be useful without also switching the FCP.  The FCP is a mono-band solution.

Schematic for W4KAZ 160m inverted L with K2AV FCP

Schematic for W4KAZ 160m inverted L with K2AV FCP

Picture of W4KAZ 160m junction box

Picture of W4KAZ 160m matching network and transformer junction box in use with 155 foot long inverted L and K2AV FCP

The Present….So, What of it?

The system now up is the same/original inverted-l vertical section with the K2AV folded counterpoise and isolation transformer in place of the prior elevated radial jumble.  What happened?

Using the K2 as field strength meter again, and using the exact same conditions as described above(sense antenna dummy load hanging from desk on 7 foot jumper):

  • 20w into the antenna from FT-920 now registers S5 on K2 S-meter
  • 40w into the antenna from FT-920 now registers S5 plus one bar on K2 S-meter
  • 60w into the antenna from FT-920 now registers S5 plus two bars K2 S-meter
  • 100w into the antenna from FT-920 now registers S9 (S5 plus three bars)
  • 100w into separate dummy load produces audible S-zero on K2

The S-meter on this K2 is not calibrated in real world db, but even without knowing exact values the signal is obviously stronger than it was with the previous TX antenna system.  Yes, that’s in the near field, but still it is encouraging.

The first field test was during 2011 Stew Perry.  Anecdotally, I was very happy with antenna performance.  It really seemed like I was louder, and it seemed I got fewer requests for fills.  But the time for a full effort wasn’t there, so there is just a limited amount of data.  Not too shabby for just three hours of operating.

A better sample was taken during the 2012 CQ 160m CW.  (And here.)  A total of 20 hours was operated. Terrible propagation conditions.   The first 6 or so hours were very good compared to previous 160m contests.  20 total hours of operation produced 593 QSO’s.  Even with terrible conditions, I was able to work a couple of EU stations.  Low Power.  Not as good as K2AV in 2011, but one hell of a lot better than I anticipated, especially in poor conditions.  K2AV is also a much better CW op, so I doubt I’ll ever be able to hit that 925 Q milestone.

So I’m pretty happy with the current system incorporating both the FCP and isolation transformer.  Many thanks to K2AV!

W4KAZ Construction Variance Notes

In implementing the FCP design at the KazShack, I made a few variances from the recommendations.

The FCP itself is constructed of stranded 14ga hardware store THHN.  I like the flexibility of the wire, the sturdy insulation, and most important, I have several rolls of it already bought and paid for.

The FCP insulators were cut from an unused piece of PVC electrical conduit.  That was also what happened to be at hand in the form of spreaders from an experiment with hex-beams.  From the length of PVC available for the job, I cut 16 spacers of 6 inches length(~150mm).  Each was drilled through three times, a hole in the center, and one about .5 inches from each end.  On the leg with two wires, the spacing is about 5 inches(125mm), while on the leg with three conductors the spacing is only ~2.5 inches(~60mm).  The holes are intentionally mis-aligned or drilled at offset angles.    That allows the wire  itself to place tension on the spreader to keep the spreaders in place.  This method makes it easy to do with an ordinary hand drill – being crooked is an advantage.  🙂   The mis-alignment alone is not enough to keep the spreaders from sliding, so they are also wrapped with vinyl cable ties as needed.  The distance between each spacer works out to about 4 feet(~1.3m).  Vinyl cable ties are also used as spacers  at the midpoint between each PVC spacer.

Measuring and threading the wire was the most time consuming part of the FCP construction.  Because all of the separators are of equal size and drilled the same, the side of the FCP with three conductors is more closely spaced than the side with two.  This made mechanical construction very easy, the FCP is taut and sturdy, and did not seem to have any adverse effects on performance.

The transformer and matching network is installed in a nice hamfest/surplus telco box, about 8x8x4.  This is a nice weather tight enclosure.  The transformer is exact to K2AV specs(by definition – it was wound by K2AV his-self!).  The matching network of switched parallel caps is scavenged from the old weather enclosure(a sealed PVC pipe) and re-used in the new junction box.  These components fit well enough, but there would not have been space to house the additional toroidal inductor had it been needed.

Besides the apparent  signal improvements over the rejected-random-raised-radial-rambling-razzledazzle, the FCP itself has other very practical mechanical merits and advantages over raised radials.

  • The folded counterpoise is simple to build.
  • The FCP is relatively small, 32′ per side(64′ total length)
  • The FCP is a LOT easier to deploy than 30 elevated radials, or burying a dense radial mat
  • The FCP lends itself to following contours, and models well when the FCP is not perfectly straight
  • The FCP will require a lot less maintenance.  The odds of falling branches breaking the FCP here at the home QTH are lower by a factor of 15. (2 legs of FCP vs 30+ radials in 30+ directions, all below branch shedding trees)
  • all of the above…..  !! yipeee!!
Bottom Line…..

But Kaz, is it equivalent to a full size vertical with a dense mat of radials?  Probably not, but there is absolutely zero chance that sort of system can ever be installed at this QTH, so the point is moot.  Do I care?  Nope, it “works”, and it “works” better than it’s predecessor 160m antenna systems at this QTH.  Very possible that improvement is just testimony to the poor performance of the prior system. But better is “better”.  Is it snake oil?  Probably not, at least not according to the CW skimmer robots and the results K2AV has had with his system, and more important, my own field testing during the CQ160m contest.

At this point, my only regret is an academic point – not having run the test of inserting the isolation transformer into the old system with the radial-jumble.   The sharp tuning of most 160m antennas suggests that common mode currents will often be a problem as one tunes away from the antenna’s resonance and the reactance increases.    How much benefit is gained from either the isolation transformer or the FCP individually is unknown(to me), but still of both practical and academic interest. I’d really like to know if the old system would have been improved with the isolation transformer installed. Still of interest, but not enough for me to spend time hanging the radials back up again!  😉   Together, the FCP and transformer seem to do a damn fine job here.  Certainly the best system that has been active in this location.

What next?  FCP phased verticals…..FCP foursquares…..FCP parasitic arrays….. MANY possibilities –  if only I had the room to do it!

References:

Until such time as K2AV publishes on the subject,  the available references are the basic instructions and a few message threads on the TopBand mail list on pertinent topics:

  1. K2AV NCJ article “The FCP: A 160 Meter Counterpoise for a Postage-Stamp Lot “
  2. W0UCE’s accumulation of information on K2Av’s 160m ideas, including the FCP
  3. Photos from W4KAZ FCP install
  4. K2AV discussion of the FCP
  5. Rolling your own FCP isolation transformer, IMPORTANT
  6. Topband: Where to place a preamp? Switching Beverages?
  7. Topband: K2AV 160m Folded Counterpoise (FCP), parts and winding for isolation transformer
  8. Re: Topband: K2AV 160m Folded Counterpoise Antenna (wire suggestions)
  9. Re: Topband: T-200 vs. T-300
  10. 2012-05-31, VO1HP FCP install
  11. Balun Designs commercially available FCP transformer

Other links:

  1. W1UJ : http://w1uj.net/FCP/
  2. KY6R : https://ky6r.wordpress.com/2015/04/27/160m-fcp/
  3. IV3PRK(FCP @ HC1PF) : http://www.iv3prk.it/hc1pf-tx-antenna.htm
  4. DL0WH : http://dl0wh.de/80m-vertikal-mit-gefaltetem-gegengewicht-nach-k2av/
  5. DM9EE: http://www.dm9ee.de/FCP_info.html
  6. W8TN : https://w8tn.blogspot.com/2012/07/building-k2av-fcp-160-m-antenna.html
  7. WB5NHL : http://oldcyberdude.com/sample-page/antennas/160m-folded-counterpoise?
  8. ?
  9. ?

 

10m Band Still Dead

I see the solar flux ended the day Sunday over 100 for the first time since 2005.

Yet Sunday afternoon, 10m was still just as dead as a doorknob.  Spent a few minutes several times hunting beacons, but only the local one here in FM05 was audible.  Didn’t hear much on 15m either, but there were a few CW Q’s and some RTTY signals.  One very faint SSB QSO.

Perhaps a few days of flux will help improve conditions.  What with ARRL DX CW coming, that would be a welcome change.

But the whole extended propagation drought has me re-evaluating the 160m antenna versus the 10m/15m antenna.  Its not necessarily an either/or, but the supports they occupy could probably be used for other things.  Its probably a good time to re-evaluate the available support/actual usage trade-offs again.  Most of the wires were hoisted based on what supports were unoccupied, rather than as a whole station best use plan. [ Plan?  Plan?]

There’s a three week window here where the temperatures will be moderate and the leaves are not yet budding.  Plan?  None yet occurs.

The 10/15m loop is probably in a spot that might be better used for the 160m vertical.  The 160m vertical is a bit on the long side, and the darn thing is working – kinda-sorta hate to “fix” something that works.  But there’s also K2AV’s new idea for the radial/counterpoise to consider.  Not sure what the real fun factor is in the situation.  In the end, the real plan is to maximize the fun.

So, where’s the long-term fun gonna be? 40m and 80m?  Never much cared for 20m……although it has its moments.

For the current moment, procrastination may cause the ideal antenna work window to come and go. The squirrels in the biological antenna support structures may get to enjoy spring unmolested.

Inverted-L Matching

The 160 Inverted-L is about 160 feet of wire.  To get a good match there is a series capacitor in line with the wire.  The bandwidth for any useful value of capacitance is about 40kc.  The object is to use a set of relays to switch in or out additional capacitors.  That will allow the antenna to be tunable across most of the band – from 1800kc to 1930kc.  There is also a 1.5:1 unun at the feed point, followed by a coax cable choke.  This lowers the SWR to a very nice 1.1:1 over the useful range.  The rig is very happy at resonance, and a good match will be a dial click away.

Currently the capacitance in the system gives a nice 1:1 SWR at 1825kc.  Using the autotuners, either radio [K2, FT-920] can work from 1800 to 1875.  The goal is to be able to turn off the tuners and feed the antenna directly.  Maybe I’ll pick up a few extra QSO’s with a good match on the antenna end of the feedline.

After several other projects using relays and the 3kv Panasonic capacitors for the band pass filters, enough extra parts are in the parts bin to make it happen.  So, why wait?

A handy nearby line previously shot into a nearby biological antenna support provides an opportunity for expansion.  The line seems well placed to add an INV-L element for 80m.  One additional relay for switching bands.  Judicious choices for the capacitance values may allow the sharing the capacitor banks for either antenna.  Being able to cover the CW segments is most important, so the minimum value used would ideally resonate each wire near the bottom of either band.  Hmmmmm.  Time to pull the 80m wire up and start tinkering.

Empirical Evidence On Longevity Of Bare AL Radials

Finishing up on the yearly mess of litter generated by the biological antenna supports was much more painful this year[literally]. The wet weather makes dragging large quantities of sopping wet leaves a real chore. Messy too. Using a leaf blower here is equivalet to bailing the Titanic with a teaspoon. Futile. The massive quantity ofvegetative miscreants combined with a gentle uphill slope renders the leaf blower useful only for clearing small areas. Maybe a chainsaw…..

During the process, two of the radials on the K9AY were “discovered” to be broken. [Ooops!] The radials were simple 17 ga. AL electric fence wire, purchased for a pittance in 1/4 mile quantities from the local farm supply. These radials were in direct contact with the soil. Soil testing a few years back showed the PH to be about 5, slightly acidic. No real idea of the chemical/mineral content, which I expectis probably a bigger factor than the acidity.

These radials have been in place for about four years. I broke both of them while raking leaves. A closer examination showed that the portions of the wire in direct contact had become quite brittle. It took little pressure to break them this year, although they withstood similar abuse over the past three seasons. A closer look showed the aluminum to be getting flaky in spots, and it had zero ductility. Even an easy bend was enough to break the wire in those areas of heavy oxidation.

Not too shocking a discovery, but worth documenting. Aluminum radials are good for about three or four years on the soil surface – in this yard.

Conversely, the three year old elevated radials on the inverted-L were inspected just before the 2009 ARRL 160m contest. These seemed to be in fine shape, with no visible signs of oxidation and no new breaks despite catching a few falling branches over the past year.

Sothe K9AY radials will be replaced with chunks of the equally cheap WD-1A surplus “field wire”. May as well see how long that lasts too.

Pollenating the Antennas – Crossed Dipoles on 40m and 20m

The tree pollen is really flying now. It is thick enough that it looks like a light snowfall or a misty rain when seen with the sun at the right angle. (Ahhhh-CHOOO!)

Pollen must be good for antennas. Two new ones sprouted up over the past weekend on new lines I shot into the biological supports before the kids’ spring break from skool.

I somewhat reluctantly packed up the 15m/10m nested rectangular loops. The support was just too good a height(about 15m/50 ft.) and location to leave it being used on relatively unproductive bands. In its place there is now a 40m dipole that favors the NW/SE directions. A bit of tuning around the 40m band doing A/B comparisons between the new dipole and the old NE/SW dipole showed promising results. The new dipole is much better into 8-land and 9-land. The old is better into 2-land and Europe. For some reason most of FL seems about the same on both. Interesting.

The differences on rx signal strength is more than I expected in a lot of cases. It makes little difference for strong signals, but a lot of difference on weaker signals. Hopefully this will help add Q’s to the contest logs. It also is a bit of commentary on the non-linearity of S-meters.

The antennas are at an almost perfect 90 degree angle to one another. They do not actually cross one another. Looking down from above they form an L shape with the south end of the NE/SW antenna pointing towards the eastern most tip of the NW/SE antenna. Modeling showed ther was little interaction between two dipoles in that configuration, but it seems likely they are not completely invisible to one another. I’m happy with it so far.

40m turned out so well I decided to do the same thing for 20m. The new NW/SE 20m dipole may be somewhat less productive, but maybe it will help to bag AK and NT and BC in the domestic tests. Unlike the 40m pair, these two antennas definitely show a difference in coverage into FL. Over the weekend there was one FQP station that was in the noise on the NE antenna, and peaking at S-5 on the SE antenna. (More S-meter non-linearity?)

The lesson learned here is that a single fixed dipole is leaving gaps in the coverage. The solution is simple. If it is practical to do so, adding a second dipole at 90 degrees to the original will definitely help fill in the holes. It’s not as good as a yagi, but better than a single fixed dipole. A rotatable dipole would also do the job if you remember to turn it. Note: switching between dipoles is a lot faster than a rotator, but coverage is less continuous .

Pollenating the Antennas – 80m Folded Dipole

Spring Fever, Hay Fever, and on the positive side, Antenna Fever.

The antennas are still in somewhat dis-array. But chugging right along in its 9th year of service is the trusty 80m folded dipole. The dipole serving the KazShack is cut according to the cookbook dimensions for folded dipoles outlined in the ARRL Antenna Book. In the ?? edition, the most recent available here, it is the lead off in Chapter 15, Portable Antennas. For those without the Antenna Bible, it was also re-published WITH permission from the ARRL, in the March 2002 edition of the CARC “FEEDLINE” newsletter. See pages 5 and 6.

I didn’t realize it had been in service so long. Given its construction from 300 ohm TV twinlead, I expected the wires to fail. It has required a repair, but that was due to damage from falling limbs. That is a problem with all of the antennas here.

It has occupied two seperate locations. Its first install favored the northwest, and it was really a killer into the upper Midwest, even with just 100w. It currently is oriented favoring a compass heading just to the east of due north. This improved the signals from Europe and the New England states, but is really a compromise.

The wonderful thing about folded dipoles is the hugh SWR bandwidth. The local version favors the CW/80m end, but the 2:1 SWR bandwidth is from about 3580kc to 3800kc. It is still well below 3:1 SWR at the bottom of 80m. It goes above 3:1 at around 3970kc. The internal tuners of both the FT-920 and K2 can bring the match down to 1:1. Sweet.

This antenna is a keeper. The only problem I have with it is that the construction article does not delve deep enough into the theory. I would like to reproduce the antenna using 450 ladder line, but don’t understand the methodology of the matching section well enough to scale the antenna. Hmmm. A conundrum.

One down, one fixed

The 160m-L has been “on the fritz” (i.e., broken) since the ARRL 160m contest. It went crazy when it started raining during the contest. The SWR went high, and it became deaf.

The ground was still covered with snow from our very rare in central NC five inch snowfall. Old XYL tales relate that antennas work best when installed/repaired in inclement weather, so the time seemed right.

It turns out there was a bad connection on one of the jumpers. I took a bit of time to find the problem, and only about 30 seconds to fix. To debug it I plugged the dummy load into the feedline system out at the antenna end. The high SWR into the dummy load told me the problem was in the line and not the antenna. Fixing the line solved the immediate issue.

That whole antenna system needs closer scrutiny. It was intended to be ‘temporary’ when it was hauled up three years back, and the feed line is a hodgepodge of jumpers which were available around the KazShack at the time. If it stays up, the matching network needs to be corrected. At last count, it now has 18 elevated radials. The feed point is about 8 feet off the ground mounted atop the kid’s wooden swing set. The radials are all of different lengths, tied off to trees. The distance of the tree from the antenna center determines the radial length. It seemed to be playing much better with 18 radials than it did in the original four radial configuration.

I suppose I’ll play around in CQ 160 CW, but I expect it will be an all US contest here in the KazShack. 100 watts is effectively QRP when run into a poorly matched inv-L. I’ll find out if I feel like trying to run stations.

The heavy winds from a couple of weeks back knocked loose a rather large branch, which clipped the nested rectangular loop for 15m and 10m. That simplifies the job of fixing it, something that has been much lower on the radio project list.

But without sunspots, I’m still in no rush to get 10m fixed. 15m either, unfortuneatly.