Topband: PT0S TB Summary

[GeorgeWallner]

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 PT0S.com 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 PT0S.com.

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.

73,

George, AA7JV