Topband: 160m LP to LP DX contacts in 2015

[Michel Spelier]

The title was changed to better describe the original question.
This topband newcomer asked what had happened to the topband conditions, given
the rare intercontinental Low Power to Low Power CW QSO’s,
even when riding upon sun propagation enhancements, as noted in this log, during
the last 6 or 7 winter topband contests.
(the last 3 years = topband newcomer)

At such distances, HP to my LP comprise the majority of the QSO’s, the amount of
LP to LP can be counted on one hand.
It is clear that LP to LP QSO’s to be very common, within eg. 3000km range (cfr.
TBDC) but once beyond, LP to LP QSO’s are exceptional
for non-exclusive callsigns.

This is with 100W and (a remotely fed ATU under) a quarterwave inv L (Tx) at
15m, down to 11m, with 50 radials of different lengths.
And with an unterminated Beverage (128m) as Rx-antenna (pointing NW/SE), on
farmers field with plenty of CM choking.

Summarizing your feedback: Two main causes seem to contribute:

1.Noise:

It would be interesting to learn by how much the noise floor has been raised
over more than half a century of topband operation…
How many dB’s were lost over time?

2.Co-channel interference:

I understand a very large concentration of NA-participants in contests to affect
their weak signal Rx-capabilities in a given bandwidth, losing a layer of weak
stations.

But even while Rx-ing (on the mid-size Beverage) during quiet (non-contest)
morning sunrise hours, signal levels (from NA) are so low and provide nowhere
the feeling,
a QSO with another similarly equipped DX-station to be possible…
As expected the log indicates, these handful LP to LP- QSO’s to have all
occurred during these timed & QTH-selective propagation enhancements.


73,

Michel, ON7EH

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Re: Topband: QRP

[Michel Spelier]

Hello,

Living in a country, where 10W has been the upper limit set by the regulator in
the early 160m days,
I have been puzzled with this question for a long time...
Given the progress on antenna and Rx-capabilities (over the years) and say
typical transceiver output power (100W),
how come it has become so rare to witness (experience) low power to low power
QSO's (over the USA to EU path)
during major topband contests (winter time on both continents) ?

What has happened to the topband conditions the last couple of decades?
IMO it is hard to believe this is due only to environmental noise increases?!

73,

Michel, ON7EH



> Op 15 december 2015 om 9:12 schreef Tom W8JI :
>
>
> > Has anyone achieved DXCC on 160 meters using QRP?
> >
> > Or is anyone even close?
> >
> > 73,
> > Art NK8X
>
> Power ratings were DC plate input power up to the early 1980's. A Heath
> SB220 was a legal input amp rated for 1 kW dc input CW, and 2 kW PEP input
> on SSB. That was 1 kW dc input all modes, or about 600 watts output on
> meters.
>
> 160 used to be 200 watts, 100 watts, or even 25 watts DC plate input at
> night because of LORAN depending on location and what 25 kHz section of the
> band you were in. That was roughly 120, 60, or 15 watts RF output depending
> on location and band segment.
>
> Many DX countries were only allowed 10 watts plate input power, or about 6
> watts RF output, on 160.
>
> That means there were many stations who had early DXCC, by today's
> standards, ran QRP. Full legal power used to be QRP.
>
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Topband: Antenna isolation measurements

[Michel Spelier]

Prior to the CQWW160, we did some (topband) antenna isolation measurements
between:
-a quarterwave inv L (top at 15m down to 11m) and
-a new unterminated beverage (0.8m high) of different lengths (via a 9:1
transformer) and 2 different locations.
The Bev used PVC-covered 0.6mm thick twisted pair telephone cable.

The power source consisted of the K3 (with its integrated wattmeter) feeding the
inv L tru a remote-fed CG 3000 ATU. The rx was a spectrum analyser connected to
 the Bev.
The very broad main lobe of the inv L was pointing to the Bev in all setups.

Setup1:
Bev length=120m  inter-ant distance=35m (distance between inv L feed and Bev
transformer)
Isolation: 33dB.
Conclusion after A/B-switching on the K3 Rx: no improved Rx noticeable (high
noise) and ext Rx input at risk. (too high input level)

Setup2:
New location
Bev length=75m  inter-ant distance= 120m
Isolation: 50dB.
Conclusion after A/B-switching on the K3 Rx: still no improved Rx noticeable but
low enough input level not to use a frontend saver.

Setup3:
Same location as above but with improved Bev grounding compared to Setup2.
(added 2nd grounding bar and longer, more ground radials over the four  5m ones)
Bev length increased to 144m  inter-ant distance again 120m.
Isolation: 43dB.
Conclusion: the S/N of the Bev is much better than the Tx/Rx inv L for the
expected heading, even signals out of the general bearing have better S/N,
others are not audible or much weaker. (expected behaviour from its radiation
pattern)

Setup3 was successfully used last weekend during the CQWW160CW. It was the first
time, a dedicated Rx antenna was put to use.
The isolation measurement on Setup3 was done 2 days after the contest without
apparent impact to the K3 ext Rx. (we expected =50dB and not 7dB less)

We hope these measurements provide sufficient detail to be of interest for
others.


73,
Michel, ON7EH
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