Radio W4KAZ

Thanks for stopping by the virtual KazShack. Feel free to comment - I often approve them.

Experimenting With Trap Dipoles- Part 2

see: Experimenting With Trap Dipoles – Part 1

Those coil and cap experiments described in part #1 eventually led me to the ‘best’ compromise solution for my situation. In the end I chose to build traps that were resonant below the higher band. I also chose to use cap values on the smaller end of the capacitance value range.

Sadly the Panasonic capacitors are no longer available. Possible TDK replacement are being tested. These TDK caps are physically smaller, and only 2Kv rated. I intend to use these in series/parallel groups once I determine the best values to stockpile. (TIP#x: leaning to several caps in series to extend the voltage rating) (TIP#x: Also decided to mount the caps in slivers of PCB, and use generous solder on the pads as well as not clipping the leads short, all in a hope to have that function as heat sinking).

Antenna Experiments:   In testing, these capacitors worked well on xmit for the first 20m/40m trap dipole, but I ran into problems with a 10m/15m trap. Using 33pf with an inductor of about .92uH I had failure of the capacitors while testing the antenna. 

As an alternative on 10m I used a bit larger inductance and a piece of rg8x coax as the tuning capacitor(low value approx 8-9pf). No final verdict on this solution yet, but the antenna functioned for light usage in 2019 WPX cw contest. Antennas will be used at 100w levels, so these cap variations should also prove suitable for this project. If weight is not an issue, gimmick caps from coax are viable choices, though I’d not use them with the traps resonant close to the operating frequency.

Alternatively the 20m/40m dipole has now been used in two different contests with success. A second 20m/40m dipole was constructed, using smaller coils and increased capacitance. This second experiment was less stable than the first, with the 20m SWR increasing slowly. Presumably the capacitors were heating and having the same problems as the 15m/10m model.

What Did NOT Work:  In the end, the experiments using larger values of capacitance proved to be poor choices for practical reasons. In the case of 10m, the caps failed outright. In the 20m case, the caps showed instability in the form of rising SWR, likely because they were heating. A revised 20m dipole with traps using a larger coil and smaller values of capacitance proved to be stable. Tip#1….Marginal caps can maybe stand the abuse in a trap if the coil is larger.

At this time I also chose to move the resonant frequency of traps a bit farther away(lower) from the operating frequency on new construction. This resulted in :

  1. the dipole legs being shortened,
  2. the impedance on 20m seemed more stable,
  3. The bandwidth on the lower band(40m) was decreased
  4. Precision in component selection becomes less critical

That set of compromises suit me, as the capacitance values are readily available, and the overall antenna length is reduced slightly, without any serious performance compromises as compared to an ordinary single band inverted V.  The antennas will be tuned to favor the CW segments, and if needed I will use the radio internal antenna tuner(at the home station) to find a match for SSB if required for 40m.  The tuner would likely only be required at the upper band edge if at all.

What worked well enough – Final Versions Constructed:  RBN testing of the trap dipole versus a normal 20m dipole showed enough uniformity in results that I am not concerned with trap losses.  The end result was a set of dipoles both for permanent use at home and several variations made as light weight as possible for portable operating.  The final 20m/40m dipole for the home station was constructed with the traps resonant at 12.650Mhz.  A coil with 14 turns close wound on the 1.5″ form was used with a capacitor constructed of several ceramics in series giving a value of 23pf. 

A 40m/80m antenna was also constructed.  These traps used a coil of 12 turns on the 1.5″ form and capacitors in series parallel for a value of 100pf.  Resonant frequency was 6.65Mhz.  For future construction this design will likely be modified to move the trap resonant frequency down to the 6Mhz range by increasing the number of turns on the coils while using the same 100pf capacitance value.

A practical benefit of having the resonant frequency away from the operating frequency is that component selection becomes less critical.  By selecting a resonant point below the band rather than on or near the band, it is not required to have values to resonate at an exact frequency.  Instead, it is only required that each trap resonates at close to the same frequency.   This is easier to tweak by adjusting the coil, and it becomes fairly simple to have traps that can be adjusted to within 100hz of one another.  The caveat here is that the dipole legs are different based on the trap frequency – but these need to be trimmed to length anyway.  [It is possible to easily replicate antennas if the traps are easy to replicate. ]  So for a 20m/40m dipole, it makes little difference whether the trap is resonant at 12.5Mhz, 12Mhz, or 13Mhz, so long as the antenna legs are trimmed properly for each.

My experiments show that having the capacitive reactance at the higher operating frequency be in the order of 400-750 ohms seems to reduce the current flow through the caps.   Probably this is enough to allow otherwise marginal caps to survive without heating and/or exhibiting SWR variations on xmit.  The voltage rating needs to be sufficient, and this can be aided by using several caps in series.  The caps in use here are all 2kv or 3kv, and used in series to increase voltage ratings.  This is sufficient for 100w levels, but unlikely to survive at 1kw or 1.5kw.   I have also mounted them on bits of circuit board to keep the leads short and provide a tiny bit of additional heat sinking.  Again, good enough for 100w, but QRO – probably not.

Experimenting With Trap Dipoles- Part Numero Uno

The Project and Situation: After quite a bit of trying over the past 15 years to find the best way to pull dipoles up into the closely packed trees in the yard it is clear the options are limited. Having the dipoles favor the NE/SW directions are the goal, but the arrangement of the best supports make this difficult. To beat this problem a combination of single band and multi band fan dipoles were used. [No, the “chainsaw solution” is not an option – yet.]

The primary supports are now occupied with supporting a 160m inverted L and another with a vee dipole for 80m. These are not high enough for direction to make much difference, but are in convenient locations. So everything else needs to fit around those two primary constraints.

The current problem is that there is really only one support that easily allows stretching out the legs of a 40m dipole in the desired directions while also achieving a good height for 40m(almost 50′). The other high supports will only allow the antenna to be deployed favoring a N/S direction(i.e., legs are stretched out E/W).

Using fan dipoles has come with its own practical problems. The dense tree branch coverage tends to tangle in the multiple wires of the legs. Then the fan legs have become entangled in heavy winds. So it is both a problem deploying the antennas, but also the SWR issues when legs are entangled after bad WX. An ongoing maintenance issue.

Alternate solution: trap dipoles. With dual band trap dipoles, it seems like it may be easier to arrange the antennas in favorable directions AND at good heights. The traps are relatively small compared to the mess of multiple wires on a fan, so also maybe it will be a bit easier to navigate dense branch cover of the biological deciduous antenna support structures. The downside is in the extra effort required in constructing the traps, tuning them to desired frequencies, and tuning the antenna legs for each desired band.

What’s the frequency, Kenneth?!? Using EzNEC 6 I ran models with trap data. Based on those results I initially decided to use traps tuned for just above the top frequencies of any given band(e.g., on 20m tuned for 14.400). I’m willing to live with the trap losses for the advantage of maintenance simplicity. Models showed tuning traps for the top end resulted in wire lengths that are the same as a single band dipole, or slightly longer. I then chose to build antennas with traps above the high end of the band based on the following.

  1. A trap resonant frequency above the band results in the dipole wires being the same length or slightly longer than the single band dipole at the trap frequency
  2. A trap resonant frequency below the band requires the dipole wires to be shorter than a dipole for that band. This might be worth pursuing if trying to reduce the antenna length.
  3. there were already a few spare dipoles laying about, and if the traps project flopped they would still be usable mostly intact if traps designed above band,
  4. I’ll probably be mostly using them on CW so maybe a tad less loss with trap rez at opposite end
  5. the gut feeling that a 20m trap resonated at 13.900 would maybe have more loss than the trap at 14.4 when used at 14.025.
  6. NOTE: SEE Part 2 for notes on how these initial assumptions changed!

Research: The traps will inevitably add unwanted weight to the antennas, and I wished to keep them as lightweight as possible. The reasoning for light weight was to extend the project to portable dipoles deployable on telescoping fiberglass masts. So I ruled out using one of the many coaxial trap designs simply to save weight where possible. For coil forms I chose to use small pieces of 1.5″ plumbing waste pipe cut from small sections of what is sold in the US as a “drain tail piece”. This is thin wall pipe, and much lighter than ordinary schedule 40 PVC. The second form material tried AND ABANDONED is 3.4 inch PVC sched 40.

Excluding the coax trap articles, there are relatively few trap dipole projects written up or documented in places accessible via internet searches. The best[most relevant] source is an ARRL antenna book article on a 2 band trap dipole. W8JI also has some interesting trap info published. Although it does not cover the specifics on the options I chose, it led me to the final result. My choices were made based on materials already on hand(wire, capacitors, and coil form material). Engineer the possible.

Initial Trap Construction: The available values of capacitors also drove the selection of trap resonant frequencies. On this point I made an effort to follow W8JI’s information and make the traps resonant off of the desired operating frequencies to minimize trap losses. Beyond this guideline I could locate nowhere any info to indicate if certain values of inductance vs capacitance were better or worse. A larger inductor will allow the antenna to be shorter overall, but the length of the dipole legs was not a restricting parameter for my project. This was merely about having the dipole resonant on 2 bands. Also, the capacitors are 2KV and 3KV 5% tolerance ceramics from Panasonic that I have used previously in band pass filter projects with great success. (NOTE: MORE ON THIS LATER!!!)

Coil Guidelines????: Guidelines for winding the coils are also a bit of guesswork, beyond W8JI’s testing results that show the highest losses occur on the resonant frequency of the trap. I simply started with the inductors, targeting a value of 6uh, initial turns counts generated by a random calculator found via internet search. Then trial and error on actual coil winding. Calculated inductances are based on trap resonant frequency measurements recorded and on the assumption the 5% caps were the most accurate component. Inductances are then calculated from cap face values and resonant frequency.

Test coils for the traps were close wound with #14 THHN stranded housing wire. They were close wound by hand as tightly as possible onto the forms. Coil Q is probably lower than it could be, but the close winding was a compromise accepted for ease of construction and ease of replication. Four inch lengths of 1.5″ waste pipe and three inch lengths of 3/4 inch PVC were tried. The latter were discarded as unsuitable.

Experimenting With the Coils and Caps: The 5% Panasonic caps on hand typically measure very close to the marked nominal values, much better than any 5% or 10% silver mica caps I have used in similar projects. I found that coils wound with similar technique and the same number of turns would reliably resonate within a range of +/-100 to 200hz. Generally the accuracy and reproducibility is better at 7 and 14 Mhz than at 28Mhz. The coils at the higher frequencies have fewer turns, and smaller differences in inductance and capacitance have a larger effect on resonance.

A group of several capacitor values were used along with an MFJ-259C as a grid dip meter to find the resonant frequencies. Pickup coupling coil was a coax jumper terminated on the business end with gator clips and a short length of #14 wire formed into an adjustable sized loop.

Some initial experimenting with the number of turns on the inductors was based on these available values of fixed capacitors. The first inductor was 12 turns on the 1.5″ forms, then resonance was tested with the values of capacitance that were on hand, or able to be easily derived using series and parallel pairs. It was then relatively simple to find the number of turns needed to be able to produce a trap resonant at a given frequency. I also wound coils on the same form material using 7 and 9 turns, and measured resonance for these.

Experimenting With Trap Dipoles- Part 2

 

Field Day 2019 – 1B NC de W4KAZ

2019 Field Day was once again a solo effort vacation camping at Carolina Beach. 

WX: 2019 WX was for the most part much better than 2018’s trip to the same location.  Temps were cooler, but the rain played a game of cat-n-mouse for the duration Saturday and Sunday.  Lessons learned in 2018 led me to use a picnic table and a tarp cover for the station, and limit the tent to sleeping and dry storage.  This worked very well, and is the plan for all future outings of this nature.

CAMP: Arriving on site Thursday afternoon, setting up the camp was not rushed by anything besides the chance of rain.  So the tent went in first, and the shade tarp was set up over the table for a rain refuge.  The shade tarp/screen tent is the NoBugZone, an idea I got from a vid by youtube channel “Outdoors On the Air”,   ordered from a sporting goods company in Canada. 

It turns out the NoBugZone was very nearly ideal for the way I chose to use it  in “spike camp” manner over a campsite picnic table.  That turned out to be useful soon after setup, as the rain came in about 5pm.   Friday was clear and warm, but the clear WX gave way to scattered storms on Saturday.  Set up Friday afternoon went well enough, deploying three telescoping masts for the antennas.

Antennas, Station, and Operating Condx.:  Decided to play with alternative antenna ideas this go around.  The recent projects at home prior to FD were some experiments with trap dipoles (in-progress-post coming late August 2019) in an effort to get a physically easier and more reliable method of multiband antennas than the previous fan dipoles.  So for this FD I chose to us an 80m/40m dipole and a 40m/20m dipole at 90 degrees to each other.  For 10m/15m I went with a fan dipole as a quick solution.

The station was once again battery powered, this year augmented by an extra solar cell to help with the mostly-shaded location charging.  The rig was an Elecraft K2.  Station & antenna set up Friday afternoon was fairly smooth, with the only problem being the fan dipole, which was difficult to trim to resonance.  

20m gave up the most Q’s.  40m would have been good were it not for high local QRN which was a tremendous problem, limiting 40m to S&P.  80m condx were better than expected given the local storms.  Operating was interrupted at least three times Saturday by passing storms tossing lightning around.  One of the breaks was prolonged by prolonged rumbles in the distance.  Not a big believer in staying on the air in bad wx, so erred on side of caution.  O’course, more cigar breaks that way was not a problem. 

Lessons?   The biggest lesson was probably related to tuning the 15m/10m fan.  Should have had that task handled before showing up on site.  10m didn’t show itself, so the time wasted was pointless.  The next lesson was finding out a cigar lighter makes an excellent pocket sized soldering torch if and when the connections are arranged for torch work.  The screw-in mast bases are champs.  The Spiderbeam 12m mast is too flexible for most of my intended uses.  The NoBugZone was really simple to set up using a tree support on one end and a pole on the second end, and not much more difficult to set up using two poles and guy lines.  It was also easy to adjust the sides for inclement wx.  Suited my intended uses perfectly.  The antenna plan was valid, as the two 40m antennas showed good results in different directions, but that was restricted by the QRN and the storms.

 

Telescoping Fiberglass Mast – Variations On A Theme

I have been using a telescoping fiberglass mast of one sort or another since 2005 or so. Most folks seem to be using these masts mostly as designed, i.e. relying on the friction fit, or using tape or hose clamps to keep the mast extended under load. None of those seemed ideal for my plans to use them with dipoles(inverted V config).

The first pole I obtained was from Henry, K4TMC (tmastco.com).(FWIW, I am acquainted with Henry via our membership in PVRC. Henry also sold me a very nice Elecraft K2 when he upgraded to the K3, and other assorted sections of surplus mast.)

This is the 32 foot pole, which results in about 29-30 foot of usable length once extended. Relying on friction fit, I ran into a couple of problems I think common to ALL of these similar type masts. The first problem is the amount of friction required to keep the poles from collapsing was also enough to make them difficult to collapse in very hot or very cold weather.(38C/98F or 0C/32F) Tape and hose clamps are usually enough to resolve that, but bring their own issues.

Tape tends to leave a lot of residue at the joint at 38C(i.e., ‘sticky mess’), which is a problem on sandy beaches. Sand does not enhance the experience of using one of these masts when it sticks to the joints. I also did not like the amount of pressure hose clamps required, nor the amount of time needed to install them in correct order(at 98F oceanside), or to fasten them without crushing the fiberglass accidentally. Because of “spontaneous collapsing” under certain types of pressure, the friction fit is not ideal for use with dipoles, my preferred antenna for portable ops.

The solution I chose was to drill the mast and use 1/8 or 3/32 cotter pins at the bottom of sections just above where they rest when extended. The pin rests on top of the next lower section, so no problems trying to align holes through two sections. Saving another 1000 words……

A section of mast extended showing position of pin, which goes through only the base of the single section.

Over the past 10 years or so I have acquired a few additional masts. Primarily to have the ability to deploy more than a single antenna, but also as redundant or spare masts. [Two is one, one is none.] These additional masts include the 12m Spiderbeam pole, both a 28 and 32 foot mast from Jackite, a 22 foot mast that was marketed as a flagpole, and several Shakespeare 20 foot Wonderpoles. The Wonderpoles are used mostly to elevate the ends of the dipole legs when it seems appropriate(mostly constricted spaces).

The mast from K4TMC has seen the most use over the last decade. It has a good combination of stiffness and flexibility for its length. I had my doubts about drilling holes for the cotter pins, but the mast has been deployed for extended periods with little signs of anything more than minor cosmetic damage. The Spiderbeam mast seems to be much more flexible, which tends to negate is useful length as a center support for dipoles. Both Jackite masts seem to be the most rigid of the group, but I have used these less than any of the others – they are relatively new buys.

The disappointment of the group for me is the Spiderbeam mast. Its flexibility requires guying to keep it from noodling with the weight of a very light weight 40m dipole made of 18ga wire. Best practice seems to be best to attach the feedline to the mast for any of these type masts, but absolutely essential with the Spiderbeam. My Spiderbeam pole also becomes difficult to extend to its full length the more it bends, although that does help keep it from spontaneous collapse. Also more difficult to deploy in heavy wind at the beach due to flexibility, common to all but more pronounced on the Spiderbeam. The other masts are more self supporting when used with the auger bases. This may indeed have more to do with their overall shorter length, and the spiderbeam masts are indeed intended to be guyed by the manufacturer. I would prefer not to use guys to save time, but in several excursions I was unable to use the full length of the Spiderbeam mast sans guy lines. Even with guys the Spiderbeam pole had excessive droop in high winds oceanside, so the additional time required did not seem worth the effort. Taken all together the Spiderbeam mast was not taking my dipole significantly higher than shorter masts.

Auger Bases? Why didn’t I think of that? : The other divergence from the norm is my use of these auger bases. These auger bases are items I have scrounged from different sources. The first pair of them I obtained from Harbor Freight in the early 2000’s, where they were being marketed as beach umbrella stands. That source disappeared soon after my purchase. A second group of smaller augers[NOT pictured below] are marketed as “Aussie Augers”, but needed modification to use with the fiberglass masts(unless you don’t mind removing the end caps from the bottom).

These augers pictured below were available via Amazon in the US in 2019. They work extremely well in sand. They are heavier gauge material than the Harbor Freight versions. The larger tapered base is my first choice for sand and seems to be the strongest. It would also work anywhere with a deep layer of loam or sandy topsoil. The base with the narrow welded on auger is more useful where the soil is less friendly, with stone or tree roots. I use the narrow base in my home yard, which is chock full of quartz stones and tree roots. It sometimes requires multiple placement attempts, but seldom takes more than a few minutes to install. For areas with no topsoil, shallow stone, or mountains, this solution might be less than ideal. The other caveat is leaving a hole in the deployment area.

Both bases are about 60cm in length(22 inches) and have a 60-61mm throat width(approx 2-3/8 inches). This is just barely wide enough for the Spiderbeam mast to fit without removing the base cap. All of the other masts are a bit smaller at the base and fit in easily. The large base has a depth about 178mm(7 inches) and the larger a depth of 127mm(5 inches). FWIW, with the smaller diameter masts I often insert a section of 2″ PVC into the base as a bushing sleeve, and the mast into the PVC bushing section.
Large tapered base at Amazon [American Ground Screw Model 2]
Narrow welded base at Amazon [American Ground Screw Model 1 with Cap ]

I don’t expect I have been the first to go down this less traveled path but have not seen it documented elsewhere. So some photos above for reference. I drilled 9/64 holes in the bottom of each nested section, just ABOVE the joints, and use 1/8 cotter pins.

My 10+ year old mast from K4TMC has been deployed numerous times. There is still only minor wear to the drilled holes, and zero cracking or vertical splits. YMMV. Caveat Emptor. An additional tip would be to have spare pins, and pins in at least two lengths. The bits of wire are used to keep the pins from vibrating loose in the ocean breeze. The also are used with coax to keep the feedline close to the mast. Generally I tape the feedline when using twinlead.

The choice of feedline is made on deployment depending on the distance from the antenna to the operating position. I use LMR240/RFC240 for the feedline drops when the operating position is close to the antenna, and 300 ohm ladderline from DX engineering for long runs.

FD 2018 with masts deployed

FD 2018 photos

2018 IOTA using single K4TMC mast

2018 IOTA K4Z photos

2018 IOTA K4Z time lapse mast deployment video

Mast Hoisting and IOTA Pages

2015 IOTA W4O at Okracoke with N4YDU

??more??

2018 RSGB IOTA as K4Z from Cape Lookout

Operating IOTA for 2018 solo again.  Once again from the cabins at Cape Lookout, IOTA NA067.  Original plan was to use wire yagi from June 2018 QST article.  Weather changed plans….

As it turns out, lots of things were different.

Original plan:

The original plan was to operate on batteries at 100w using the K2 as the station.  Original antenna plan was to set up wire yagi’s for 40/20/15 using three telescoping fiberglass masts at ~30 feet height.  The wire yagis were to be based on design from 2018 June QST article(ref?).  An additional mast was going to be set up for 10m/80m, using a 10m dipole that I would base load for 80m with a K2AV style folded counterpoise.

Revised Plan:

The weather took a prolonged turn for the wet and nasty about 10 days before the event, and forecasts for IOTA weekend were maybe even a bit worse.  On the drive down to the dock the on Friday I hit light rain a couple of times.  Also a short shower as I exited the ferry onto the Island.   No lightning, but radar showed active storms offshore.  So the original antenna plan was trimmed to bare minimum – a single mast with multiple dipoles.  And a plan for quick disconnects if things got worse.

Time Lapse video, mast deployment–>  https://youtu.be/hy2bE-N47tI

After setting up the antennas and station, quite a bit of time was burned debugging a couple of mistakes, a mixup with the feedlines and a 40m dipole with a bad connection.  Temps were about 30C, with a continuous ocean breeze.  So it was a long hot day, but not as uncomfortable as either 2017 of Field Day 2018.  But tiring, so not much radio play.

Operating Conditions:

1200Z Saturday morning – Scarf up some breakfast after a restless night of broken sleep.  A quick trip outside to tension the dipoles and eyeball local WX conditions.  Lots of cloud cover, brisk wind, but no rain or lightning.  Nice.   Turning on the radio – “OK – what’s wrong?”  Very few signals heard, all very weak.  Spent time checking to see if something was broken.   Eventually worked a few, but not having fun.  This was a real discouragement, as I had a lot of success with essentially the same set up just a month earlier for ARRL Field Day.  Was not counting on not hearing any EU stations in the morning.  Was also not counting on having such difficulty working US stations.

Spent some of the down time scouting some of the other cabins as potential sites for future trips, and a good bit of time on the beach.    Tried a couple of times in the mid/late afternoon to get runs with domestic stations, but zero success.    Starting to seem like a S&P affair.   Tuning the bands at around 1630Z it was starting to seem like there was more activity, so finally settled in for a short run on 20m CW.  WX was starting to look bad so I decided to take a break for a short siesta.  Decided I’d make a decision after getting some rest and food.  Another 20m run from 2030-2130Z and only 30 or so Q’s.  Bleh.  Unable to run on SSB after several attempts over the late afternoon.

2400Z and the WX is OK overhead, but storms over the mainland and radar looking worse.  Forecast is calling for major storms overnight and in morning.  Here is where a bit of bad planning caught up with reality.  The return trip on the ferry was scheduled for 1300z Sunday, which would have been a bit rushed in good weather.

So I decided to pull the mast down and yanked the plug on the operation.   This turned out to be a Very Good Thing.  Sunday morning brought a heavy storm with lots of lightning.  Better to watch it from inside than try to fool with antennas in that.

What Worked:

The plan for setting up the yagi’s would have been workable in this cabin area.  There was enough room for everything needed.  Batteries and station equipment, all FB.  The ‘basic’ food plan was fine.

What Broke:

The trip reservations – not nailed down far enough in advance.  The 40m dipole – must have a break in one of the wire legs.  The operator – Poor CW skills, and not sleeping sucks!

_____________CW          __                     PHONE

BAND      QSOs      Point      Mults  QSOs      Points      Mults

80            0             0               0               0           0            0

40            0             0               0               1           5             0

20           57          415           10             19         155          6

15            4             30             2               1             5             0

10            2             10             0               1             5             0

625          X             18 =          11250

points                     multipliers  score

Red Pitaya SDR as Core of CW Skimmer – Part 2, Notes and Updates

Additional Red Pitaya CW skimmer notes, last update 2018-08-22
for original detailed post see:  Red Pitaya SDR as Core of CW Skimmer – Part 1
Notes and Updates
2019-02-01

Note 4, RX Antenna:  The skimmer system is now using the 3.8 wave inverted L as its RX antenna full time.  The only anticipated interruptions will be occasional 160m contests.

2018-08-22:

Note 1:  Skimmer station outage in mid July 2018, cause appears to be rx antenna related.

Note 2, Transformer:  N6TV identified a mini circuits 14:1 transformer that is suitable for use with the Red Pitaya on RX.  Expect the transformer to be available from Red Pitaya, or occasionally N6TV.  Available from mini-circuits vendors, but may be expensive in quantity 1.

Note 3, RX antenna:  Some what by accident I discovered that the 160m L I use for transmit seems to make a fine all-band rx antenna for the Red Pitaya skimmer set up.  FWIW, the antenna is about 140 feet of wire.  About 60-70 feet vertical, with the remainder making a dog-leg turn from top of vertical section.  From there it runs horizontally  NW to second support about 40 feet away, and a second sharper turn to the east, horizontally and slightly downward for the remainder which runs west to east.  The radial system is the K2AV type folded counterpoise system described in more detail at link.

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!

 

 

NT4D Estate Items For Sale

This page will be used to list photos of items for sale from NT4D, SK late 2016.

The following items are for sale from  NT4D.

Alpha 87A – $3400

Good condition Alpha 87A

Good condition Alpha 87A

Drake MN-2000 #1  – $200

Drake MN-2000 #1

Drake MN-2000 #1

Drake MN-2000 #2 – $200

Drake MN-2000 #3 – $200

Drake MN-2000 #2 and #3

Drake MN-2000 #2 and #3

RBN Spot Counts, CQ WPX CW 2017

To get an idea of the efficacy of the Red Pitaya skimmer set-up, I pulled spot counts from the RBN via screen grabs off of the ‘Spots Analysis Tool’.  During the 2016 contest the skimmer station at W4KAZ was run with softrocks as the skimmer SDR, skimming only 160m/80m/40m/20m.  15m was better during 2016 than 2017, but the softrock for 15m was not reliable enough to run during a contest.

With that caveat, the W4KAZ spot  counts from 2017 are quite a bit better than those from 2016.  This reflects skimming 6 bands in 2017 as well as improvements  due to Red Pitaya vs Softrocks(2016 skimming was for only 160/80/40/20)

Spot counts from RBN for the CQ WPX CW of 2016/2017.  They are grouped by continent and sorted from high to low spot counts.

There are 4,489,640 total RBN spots for the period of the 2016 contest.

There are 4,431,759 total RBN spots for the period of the 2017 contest.

http://w4kaz.com/images/pages/skimmer_spot_counts_wpx_saturday.htm

http://w4kaz.com/images/pages/skimmer_spot_counts_wpx_sunday.htm

Despite a similarity in the total number of spots, the spot distribution shows the counts for Europe significantly higher in 2017 vs 2016.  In North America, the spot counts on

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.