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Topband: PT0S TB Summary

Subject: Topband: PT0S TB Summary
From: "GeorgeWallner" <>
Date: Fri, 30 Nov 2012 10:44:03 -0500
List-post: <">>
G'Day Topbanders,

Here are some of the 160 m aspects of the PT0S operation that may of interest to those on this reflector.

Our TB TX antenna (and RX for the first 2 nights) was an inverted L located on top of a rocky outcropping that jutted into the sea, about 8 meters (25 feet) above the water at low tide. At high tide waves were crashing on and around the base of the antenna. The vertical section was 16 meters long and the horizontal section 12 meters long. The antenna was fed via a home brew automatic antenna coupler located 1 meter above the base. A large number of radials (40+) of various lengths were draped over the rocks, most of them ending in the surrounding salt-water. The rocks beneath the antenna had numerous cracks and crevices leading down to the water. There were also pools of salt-water all over the rocks. (See for pictures.) The antenna had a clear shot over open water from East to West and was somewhat obscured to the west-south-west by the peak of Belmont.

We had K3 transceivers. The main station, which handled 160 m, had a dual SG-500 amplifier with 1 kW output. Initially noise on the TX antenna was S9 + 10 dB. It was typical switch mode power supply noise. The antenna was located about 30 meters East of the main rock, Belmonte's peak, which is about 25 meters tall. The peak carries a light tower, two large satellite dishes and many scientific instruments. There are a large number of power and data cables criss-crossing the top of the peak. We suspected that the noise was coming from one or more of the scientific or communications packages on the peak. We also expected the large inverters located in the building of the scientific station to contribute to the noise. (They did not! German made, quiet as a mouse.)

The main station was ready to go by 20:00 Z and hoping that there may be some top-banders who can put a S9+10dB signal into the middle of the Atlantic, we sent out a CQ. Clive, GM3POI, responded instantly. We had real trouble copying his call through the noise, although he must have been well over S9. During that first night we made about over QSO-s, a testament to the fact that there are a lot of top-banders with great antennas (or serious QRO and decent antennas). Next night, we faced the same noisy conditions but were able to log another 100 contacts.

After the second night we located the main source of the noise (using a portable KX3 Receiver and a small loop antenna). It was one those very common switch mode lap-top power supplies, powering some of the commo gear on the peak. Once we eliminated this noise source, noise was down to a "pleasant" S6 - 7.

RX Set-up (built on days 3 and 5): We had two RX antennas. One , facing north, was a 4 m x 4 m flag, erected on the very steep north facing slope of the peak, about 2 meters above the rocks and 20 meters above the water. A second flag of similar size was erected later on top of the peak, next to the light house. This flag was facing south, LP to JA. The two RX antennas were connected to a custom built remote pre-selector and amplifier. The pre-selector had 9 sharp band-pass filters, selectable from the operating position. The pre-amp had a gain of 25 dB and a very low noise figure. (See Gary, KD9SV for info.) The pre-selector was connected, via 100 meters of RG-6, to a receiver front-end, which contained RX antenna switching, remote controls for the pre-selector, a second low noise pre-amplifier (10 dB gain) and an output splitter for feed the K3 RX input and an QS1R SDR. The SDR was running CW Skimmer. (By the way, with the pre-amplifier, the SD1R did hear a little bit better than the K3!) We used this RX set-up on all bands. The LP flag was especially useful on 40 meters when working JA-s in the morning. 0n 160 most of the time we had both pre-amps on for a total gain of 35 dB. (We did not use the K3's internal pre-amp.) I felt that we had a good RX set-up. Not like a Beverage, but given the limitations of the terrain, the best we could do.

Some observations: (Some of these are after-the-fact, but may help with the next one.)

* Propagation on most nights was very uneven. Some well known EU and NA stations were coming in very strong, while others were weak. We felt that on many nights our signal was strong in FL, weak in parts of the Midwest, and reasonable on the west coast. I would appreciate reports to verify that.

* On a few nights there were periods when 160 was like 40. We were able to operate at high speed and log a lot of contacts. Unfortunately there was also some 40-meter-like behavior. There were some persistent callers, who kept calling during exchanges or when the operator was asking for a completely different partial call. That was all visible on the SDR/Skimmer screen. You could see the persistent callers and you could tell who were just simply making a mistake calling out of sync; all with the relevant call-signs displayed on the skimmer screen! If we had decent Internet access, I may have posted some of the screen-shots. They would have been very telling.

* There were relatively few "can't-copy-the-DX" callers. (We had a lot of them on TX3A.) There were many who seemed to be like that, but they would come back on the third or fourth (or fifth) call, indicating that they were experiencing QSB.

* We had no fish-buoy QRM. Surprising, as there were some long liners operating about 300 nautical miles to the west of us. I guess they just did not have any buoys in the 1820 - 1840 range. (The boat we came on also had a number of buoys. They had pre-set frequencies between 1750 and 2200, but none in the 160 m band.)

* On several nights we had strong thunderstorm noise. The noise tended to be stronger during the earlier part of the night.

* On most nights we had strong and fast QSB. Sending at higher speed (25 +) helped some callers get their call-sings through. (At other times the high speed was a hindrance.)

* On several nights there was absolutely no propagation between our SS (around 1945 Z) and until about 2100 Z, when the band would suddenly open to EU with decent conditions. During these times, we often heard EU stations working each other but they never heard us. (HA5DM was 599+ and I must have called him 10 times. A couple of hours later, HA8DM called with a good signal and we made an easy QSO.)

* One one night we had a fantastic gray line opening starting around 1940 Z. Signals were hugely enhanced. (One of the operators asked if I was on the right band!) We turned on the speaker and enjoyed listening to the perfectly clear S9 + 30 dB signals from EU. After about 20 minutes, signal levels dropped back to normal.

* The SDR + CW Skimmer was a great tool. The skimmer helped to resolve difficult to copy call-signs about 10% of the time (we were hoping for more). Generally, the ear was better and about 1 to 2 second faster than the skimmer. The skimmer allowed us to monitor both up (for EU and NA) and down (for JA). It was very effective at showing where callers were. Importantly, it showed us where the strong callers were and where the pile-up was too dense.

* We made no JA QSO-s on 160. A big disappointment. We were heard as far KH2 on one side and we made a few UA0 contacts on the other side, but no JA-s, either via SP in the evening or LP in the morning. (At the same time, the 80 meter station was working JA-s, mostly in the morning via LP.)

We made a over 3000 QSO-s on TB. The distribution between EU and NA was about even. You can see more info on QSO counts on

Special thanks those who provided us with crucial technical support:

N4IS: RX antenna info, Filters and custom shielded enclosures.

KD9SV: pre-amplifier help

K9YC: Ferrites for noise reduction

Also thanks to those who provided financial support, and of course, thanks for the all QSO-s.


George, AA7JV
Topband reflector -

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