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IV3PRK Pierluigi “Luis” Mansutti

160 Meters: DXing on the Edge

My two years in Ecuador as HC1PF - part 1

In January 2014, with my wife Luisa, I moved to Ecuador, where our son is living, and we bougth a lot for our new house. It was at the corner of an urbanization - the largest one, 1900 sq. maters - with the possibility to install 160 m. antennas, hopefully also Beverages, in the external wild nature.

This is the Google Earth map of my new location in Puembo, about 20 km. from Quito, at 8.000 feet altitude, on a valley ridge, right on the equator. Location is: 0°10’31” South – 78°22’33” West – Grid Loc. FI09tt

By December, the house was completed and me and my wife were already living here for a new adventure. On top of the living room, a big picture of my birthplace taken 40 years ago from top of the IV3PRK antenna!

In the mean time, I got all the documents for our regular residence in Ecuador, and also the membership of the “Quito Radio Club”. Thanks to the president, Gustavo HC1BG, I received very quicly and without difficulties or examinations, my definitive ten years license HC1PF.

At last, by Christmas, after completing the garden with palms, orange and avogado trees, and the entrance with equatorial flowers, also my radio shack was ready, and I could seriously dedicate myself to the antennas.

All my equipment has been safely carried here and the shack is exactly the same as it was for IV3PRK in Italy.

I carried also a lot of cables, spare parts and all the stuff required to build and test every kind of 160m. antennas, including my heavy General Radio GR916 - Impedance bridge.

In designing my new house, all possible details were programmed for efficient and safe radio activity. This is the entrance panel for all TX and RX coax and control cables. Two Poliphaser protectors are used and all the station chassis are connected here to the same ground rod and to the house grounding system through a large copper sheet as recommended by W8JI .

Polarization and the choice of trasmitting antenna.

Usually, polarization of the signals is not an issue on the higher HF bands and for stations of the most crowded areas (Europe, North America and Japan), all located at mid-latitudes above +45 degrees magnetic dip angle, or below -45 degrees (Australia, New Zealand and South Africa).

But at low-latitudes, between +30 and -30 dip angle degrees, 160m. sigs can be heavily absorbed by coupling losses with the ionosphere. And that’s depending on the angle and polarization of the signal and the angle of Earth’s magnetic field. This is an azimuth DX Atlas map showing the magnetic dip angles: it’s clear that in my new location in Ecuador, polarization is going to be an issue on 160 meters!

With references and thanks to Prof. Bob Brown, NM7M (SK), and Carl Luetzelschwab, K9LA, I put together a short paper downloadable here as PDF file.

So, in December 2012, when I was still in Italy, but planning to move in Ecuador, I studied the problem and performed many EZNEC runs on several Inverted L and Vertical T models “at the search of the best TX antenna for a low latitude location”. All the results, summarized in Excel graphs, and EZNEC pattern scheenshots, are put together in this downloadable PDF file.

Arrived here, I had a clear idea about what to do.

Building and raising the Inverted L antenna.

Without any doub, my antenna had to be the Inverted L, favouring an high angle radiation.

But the realty, unfortunately, was a bit different from what expected, with some new constraints and difficulties for 160 m. antennas. First of all, it was impossible to put down a full ground radial system under the lawn. Than – we are in South America – it has been necessary to install an electric fence on top of the 2.5 m. high brick wall. The tuned elevated radials, as I had in Italy, should had coupled with these 180 m. long wires for sure – as it will be demonstrated – and thus my choice was to try the K2AV FCP system.

I bought and carried from Italy the planned aluminium tubes, from 65x5 mm. to 22x1.5 mm., but the original design had to be modified, due to the feeding point rised at the eigth of the wall, where the FCP wires are extended. Thus, the phisical length of 21 m. of the vertical, less 2.50, resulted in a real radiating length 18.50 m.

So, I began piercing the tubes and putting them together. The lowest thick tube - 65 outside and 55 mm. inside diam. - was cut at 2.50 m. as the base section, and inserted a piece of 60 mm. Delrin isolator (turned up and down to 55 mm.). This is the point where the vertical radiator starts, and the FCP counterpoise is connected. Than, I installed the base, built in my son's workshop in Quito, with a gear winch and a 6 m. gin pole for smooth raising.

As expected, on Saturday we were ready to raise it with the help of my good friend Rafael, HC1TCD, and his father. In the pictures down here, that’s me with Rafael’s dad, on the left. But, on the rigth, we see tha, as on all great occasions, also the help of my wife Luisa was needed and, finally, the vertical section went up..

The K2AV FCP counterpoise.

Lastly, I installed the FCP counterpoise ( 50 m. of 2 mm. solid copper wire folded back on itself ) for a total length of 20 meters at 2.50 m. height, without any other radial or ground connection.

Yes, that's true: only one folded wire, instead of radial system, neither buried, nor elevated! The heart of FCP system is the big toroid sold by Guy, K2AV, shown inserted in the matching box. I provided a lightning protection with two pieces of copper sheet with 1 mm. separation across the isolator. Inside the matching box I put a series/parallel combination of 24 ½ watts resistors of 10 Megaohm as static discharge.

Tuning and pruning the horizontal wire.

This has been the most difficult and time consuming process!

I started with the horizontal wire of 28 m., for a total inverted L length of 47 meters, enough for shortening in search of the resonance as designed with EZNEC. I built the L-Network as calculated with TLW and checked with the .EZ model, but what a mess ! …quite far from any kind of results.

So I had to ask for help to K2AV, the originator of the FCP system, and Guy has been really helpful. At first he said to forget all the EZ files, because the results of a real antenna over an FCP are very different from the models and the only way to find a resonance is to look at the point where R is 50 ohms, and than tune out the reactance. But my readings were so far from the target: the antenna seemed to find a 50 ohm point below 1.500 khz or above 1.900 so I had to lengthen the horizontal wire to 32 m.; now the 50 ohm point went down around 1.850 and I began trying to tune out the reactance

For two days I tried adding and subtracting mica capacitors with all the wide range of a Jennings 7-1000 pF vacuum capacitor, but no way to get rid of very odd reactance values.

So I decided to give up with the FCP and go back to the old tuned elevated radials. I cut two 42 m. radials and connected instead of the FCP. Even worse: the resistance value decreased around 20 and the reactance jumped higher. The elevated radials, much longer than the FCP were coupling much more with the electric fence. By the way, Guy recommended me to make all the measurements directly at the antenna base, but that was impossible here due to strong BC nearby stations on 1.510 , 1.580 and 1.590 KHz ( 9+50 dB signals) which upset the readings of my AEA CIA HF analyzer. So all readings were made in the shack, taking into consideration the feed line length, and they appeared quite stable and reliable.

The next day I reconnected the FCP and began again with lower capacity values. The 50 ohm R point was where I wanted, on 1.825, but no way to tune out the reactance. After many other variations I came to the decision to further lengthen the horizontal wire and, after adding, cutting and trying, I came out to 34.3 m., which means a total length of 52.8 meters, about ten meters longer than the expected quarter wave. And longer than the distante between the vertical section and the house roof support for the termination point, so the last 2.30 m. of horizontal wire had to be bended vertically.

The pattern shown by EZNEC indicated much high angle radiation than desired, but the performance “on the air” was outstanding: in a couple of days I worked a lot of stations from NA and Europe, and was unable to pull out many more calling me!

I was not aiming at such an high angle radiator, but the realty and local constraints took me there. Probably this kind of antenna works well only in this particular location, surrounded by a 183 m. electric fence, at 2.400 meter of altitude on the equator. In any case the K2AV FCP system works great and gives everyone the possibility to put, also in a small lot, a very efficient antenna on 160 meters, thanks Guy!

Yesterday a direct strike destroyed the mica capacitor in parallel with the vacuum variable one. I substituted it with a close enough one, but had to retune the whole system by lengthening also the horizontal wire until I reached a perfect match. ====>>

Quito - March 24, 2015

But in the following months the antenna collapsed three times due to sudden huge winds - even in a sunny day - always promptly fixed and reinforced with what available.

The rotatable Flag at HC1PF.

In the mean time, I installed also the first receiving antenna, as far as possible from the transmitting one, but within my wall. I carried here the original W7IUV rotatable flag, that has been used in Italy for many years, but it could not fit where I wanted to install, far enough from the TX antenna.

So I decided to reduce the size and the weight. As said several times, pennants and flags “want to work” and their dimensions are not critical at all, provided we keep, more or less, the same relation between the sides. The lobe and the F/B are still the same but, of course, the smaller capture area produces a reduction in gain or, better to say, increases the negative gain by 5 dB: going from -30 to -35 dB is not a problem with good KD9SV preamplifiers.

These are the reduced dimensions: Horizontal wires: 6.63 m.; Vertcal wires: 3.21 m.; Load resistor: 900 ohm;

Transformer: 2/8 turns on a binocular BN73-202. These pictures show me, to the left, installing the flag, and to the right, my south point reference: the Cotopaxi volcan, 5.897 m. high, at 50 km. distance.

Several tests made with my usual 1.843 oscillator on the SDR-IQ receiver indicated about 20 dB of Front to Back, not bad at all, but with a noise level rather high, and that's going to be the most difficult problem to solve here.

This is the rotatable flag completed, 6 meters high, and above the electric fence, but not far enough from it: five turns of wire, each 183 m. long – like been inside a 5 turn coil at 10 kV pulsing voltage !

Anyway, this is the only receiving antenna that will survive and I'll keep as a reference until the end of my HC1PF activity.

The Pennants system.

After the first days of activity I realized that the TX antenna was very efficient and I could not pull out of the noise all the stations calling me. No way to listen on the inverted L, due to the high noise, the rotatable flag was doing its job honestly, but I needed some alternatives. So it was the time to install some of the pennants I carried from Italy. IV3PRK was using two groups of three pennants, with 90 meters of separation and phased in a broadside configurations, but not enough space here.

On the other side, I promised the XYL to keep a low profile with the least impact of antennas, so I stuck four 3 m. timber poles on the corners of the vegetable garden and on them I tied the pennants to cover four directions. One of the nice features of pennants and flags is their independence from ground, so no nuisance to gardening and foot traffic with low wires. Fortunately I had already provided buried coax and control lines to reach the central box in that area.

I modified one of my old switching boxes to accommodate the fourth position and carefully checked everything. Before rising the pennants in the final position I tested the system from the shack with the AEA CIA analyzer and it was evident something wrong. Checking at the base, the antennas were switching and working correctly, so the issue was in the feed line and found the culprit in a buried common mode choke (CMC) connector. I changed it with another one, wound on the new FT240-31core, and things went ok.

On the side, we see the pennant central box at 4 meters height. All the system has been raised above the brick wall and the electric fence.

In the picture below, the pennants as seen by the TX antenna and its FCP counterpoise, which is only 10 meters long on one side, and does not interfere too much with them as the ¼ elevated radials should have done.

Anyway these pennants perform exactly as well as the rotatable flag: no difference by switching them or turning the other ….so next plans are to take them down and substitute with an horizontal loop. As demonstrated by the performance of the “long” inverted L my signal couples well with the ionosphere at high angles, so it would be worth trying a high angle antenna also on reception.

Quito, February 15, 2015 Luis HC1PF ex IV3PRK

Trying an Horizontal Loop: a waste of time?

The outstanding performance of my Inverted L antenna with a “long” horizontal wire, radiating for sure at high angles, confirmed that the dominant polarization – in this location, high on the equator - is horizontal, rather than vertical as usually happens at middle and high latitudes. I am always and everywhere heard better than I can hear the stations calling me, so I’m aware I must equalize my situation, trying to get down the signals from the ionosphere with the same angle I am sending in. The easiest solutions should be to receive on the same TX antenna, but the noise level is prohibitive, so I decided to try an horizontal loop. With AutoEz , the beautiful program by Dan McGuire AC6LA, I performed some modeling and found these results for a square loop of 9 meters side and 6 m. height:

Most of the radiation is at 60 degrees with low directivity, while at lower angles (15 deg.) there is some moderate front to back. The elevation plot shows max radiation at 63° and the great difference between horizontal (green) and vertical (bleu) components. ===>>

The source data indicate that a load resistor of 1.050 ohms is needed to get an easy restive match, without reactance.

Thus my choice was to use a Cat5 twisted pair, which is balanced and very light, from the loop to the coax cable, and to use two binocular BN73-202 transformers:

The first one with 9/3 turns (7/2 is also ok) to go to 100 ohms and the second one with 4 and 3 turns to go to the 50 ohms coax line.

The impedance readings on th antenna analyzer were correct, and this is the loop installed on the 6 m. fiberglass poles which were used for the pennants. But the results “on the air” are quite disappointing: the noise is lower, but also ALL the signals are 10 to 20 dB LOWER than on the flag, so they are NOT arriving at high angles as supposed….. in any case, more time is needed for further tests under different conditions.

February 20, 2015 Luis HC1PF

The K6STI Loop at HC1PF.

One of my oldest friends and most successful Topbander, John G3PQA, was complaining about noise growing even in his UK location, and he was taking into consideration the K6STI loop.

This is a specialized receiving antenna, omni directional - and thus, with a low RDF - but with low sensitivity to vertical polarized noise and - my worst problem - to local AM broadcasting signals. This loop has been fully described in two articles on QST, Sep. 1995 by Brian Beezley, K6STI and Edwin Andress, W6KUT. After deeply reading these articles, I went to EZNEC and, with the cooperation of G3PQA, modeled my own loop with the real possible dimensions: a perfect square with 9.25 meters per side and 6 m. high, to substitute the previous horizontal, resistance loaded, loop. The innovative two feed points 180 degrees out of phase produce two 44 degr. elevation lobes with horizontal polarization, as desired at my location.

The source data at the 450 lines junction indicated the impedance as R = 3.5 + j 370 ohms and thus I calculated the matching system: a capacitor of 235 pF to null out the reactance followed by a 4:1 transformer (only one turn on the antenna side and four turns on the coax side) of a binocular BN73-202, as advised by John G3PQA, who tested back to back several transformers.

The Eznec SWR function, after the insertion of the feed system, produced this graph ===>> which shows a critical tuning with an extremely sharp BW.

Going to the practice, the most boring work was the ladder line construction: from the smallest available electrical raceways I cut and drilled 100 insulators - 5 cm. each - and placed every 15 cm. to get the 450 ohms impedance (#14 wire).

John was a bit ahead of me with the project and, after blowing his analyzer during the first measurements, suggested me to add a 5/50 Kohm resistor between the loop and the earth for static discharge.

So I put a 10 K ohm 4 watt resistor across the transformer, connecting the loop to the earth via the coax shield. With the antenna analyzer I made some measurements on a surplus ceramic compression trimmer (marked ZA2009) and found its range from 125 pf to 580 pF with 4 turns; fixed at 235 pF – according to Eznec – and put in the box as a starting point. Like him, I began the readings with my AEA CIA analyzer on the ladder line junction: they were unreliable and not stable, but in the range of R 600 - 800 ohms and X around j500. Than, I measured between the capacitor and the xfmr: R = 7 X = j10. At the coax connector: R = 126 X = j212 . So, I said, it must be necessary to better null out the reactance and a less transformer ratio. I reduced the primary from 4 to 3 turns: it should be ok to go from 7 to 50 ohms, but not enough. Now the best achieved on 1.825 was R = 88 and X = j60. Back to measure between capacitor and xfmr: R = 8 and X =j15 With such a low impedance everything is sharp and critical and a few ohms of reactance, which usually do not care on the high impedance loops, like flags and pennants, in this case produce unexpected transformations and results. As it was impossible to completely null out the reactance by means of the 125-580 pF compression trimmer, I put in parallel another small one 3-20 pF and with its smooth adjustment immediately got X = 0.

But now the reading of the resistive component grew up to 14.5 ohms. At the coax connector, after the 3:1 transformer, the reading worsened at R = 118 and X = j185. So the xfmr had to be calculated again, and I reduced a further turn on the secondary. Now the definitive turns are: ONE turn on the primary and only TWO turns on the secondary (coax side) on a binocular BN73-202. PERFECT: now the readings at the coax socket were: R = 47 and X = 0 on 1.850 KHz; by smooth regulation of the second trimmer the null was carried down where wanted on 1.825.

For sure it was a good exercise on antenna’s tuning and matching, but now let’s see if it was worth and really works on the air!

The first night of tests was quite disappointing: the only usable antenna was still the rotatable Flag. The K6STI loop seems to produce only noise like all the other antennas. These are the noise graphs taken around noon on the SDR-IQ receiver:

K6STI Loop: - 105 dB; Rot. Flag: - 119 dB

Inverted L: - 72 dB; NO antennas: - 126 dB.

So, noise level on K6STI loop is 33 dB lower than on Tx antenna, but the rot. Flag is still 14 dB better!

All the feed lines are deep buried with common mode chokes and ground rods.

I disconnected and checked the 96 m. coax going to the K6STI loop and it appears to be ok:

Loop feedline (96 m. old RG213): -122 dB; NO antenna and NO feedline: -126 dB;

The same feedline w. shield disconnected: -79 dB

Now, I will keep this loop under test for some more time to verify if I will take any advantage on the high angles supposed to be dominant at these low latitudes, but I’m afraid it has been a waste of time…once more!

Quito, March 13 2015 Luis HC1PF ex IV3PRK