Robi,
Thanks for providing the information. You did not specify if both stations
were using the same receiving/transmitting equipment.
73,
Henry - K4TMC
On Tue, Feb 25, 2025 at 8:25 PM s53ww <s53ww@hamradio.si> wrote:
> Last week, for the ARRL DX CW contest, Sine/s53rm and I set for an
> experiment - results might be of interest to a wider contesting community.
>
> The main idea was to verify performance of the VDA antenna at the sea
> front (Vertical Dipole with Reflector) in direct comparison with the
> "regular BIG GUN setup" - at the same time and same micro location. Our
> TeamC (TK0C) has almost 10 years of experience with VDAs (using them as
> in-band antenna), but there is never enough time to make quality
> performance comparison. So Sine/s53rm and I set for a direct competition
> on a 10m band as SOSB10hp. S53RM operated station with two stacked
> 5el.yagis on top of the 400m a.s.l. hill with sloping terrain toward the
> US. And where the terain hit the sea (7km from the hill top), I installed
> a single VDA antenna at the sea shore (having wet feet during the high
> tide). It was a field day style operation in a camp, working from a van,
> 50m coax to the antenna, SSPA outputting 1450W.
>
> For the VDA at the sea front the radiation pattern is without unknowns;
> 10dBi of gain down to zero elevation. The 5-over-5 stack on the hill top
> is not that straightforward as the sloping terrain is far from the model
> used by the Terain Analayzer - in fact, the vertical radiation pattern
> changes significantly when simulated between, let say, 310 and 315
> azimuth
> angle. Nevertheless, 8dB higher gain as compared to the VDA was expected.
>
> The result is confusing at best. S50C made only 41 QSOs and one
> multiplier
> more than me (836 vs. 795 QSO). For the first day we agreed to operate
> "big gun" style (grab a QRG and call CQ). S50C finished with 491 QSOs (80
> more than me), where first 40 were gained during the band opening, and
> the
> second 40 during the band closing. We had the same number of multipliers
> (49), but different were missing and jointy we logged 655 different
> stations. I was monitoring the RBN reports all the time and S50C was
> always 6dB to 16dB stronger (reports would come from the same skimmer at
> the same time, so no fading contribution here). On Sunday, the conditions
> improved, still the QSO difference diminished from 81 to 41. On Sunday
> s53rm was mainly calling CQ (24 S&P QSOs), while I spent more time S&P as
> no one would come to my CQ for minutes (61 S&P QSOs). The final QSO
> difference was made on the west coast (Zone 3) stations (71 vs. 35). In a
> joint LOG we have 1107 different calls (85 from Zone 3).
>
> Now, 200km inland to the east and south east, another two stations
> operated as SOUSB10hp, 9A3TR(@9A7A) and E70T(@E7DX). Both with similar
> setup as S50C (7/7 and 5/5) over flat land. RBN reports show similar
> signal strengths as for S50C (but different fading conditions - as
> expected). If their S&P QSOs are removed, the total QSO count is 868 for
> 9A3TR and 905 for E70T. So if all of us would be just calling CQ, we
> would
> made approximately the same number of QSOs (800-900).
>
> But the 4 of us collectively worked 1529 different US stations! The
> largest difference between the VDA and the stacks is on the Zone 3 calls.
> While s50c/9a3tr/e70t worked 71/73/63 of them, I only logged 35 (but(!)
> there were 132 different Zone 3 calls in our logs).
>
> I need to state, that none of us was stressed not for a minute with a
> pile-up (max. rate was around 130 Q/h and just for one hour). There was
> plenty of time to work stations and the band was wide open (when it was).
> Maybe one more detail, while s53rm had many signals with strong QSB (fast
> and deep fading), all the signals on the VDA were very stable.
>
> So few questions popped up:
> - is 10dB signal strength (on TX and RX!) really worth only about 10% on
> the QSO count?
> - if I would operate VDA style from a "high callsign gain" DXCC (being
> red
> on the everyones bandmap), would I log 1500 QSOs?
> - 10dB gain does show a difference for the west coast stations, but
> almost
> no difference to Zone 4 and 5 - how come?
> - is operating style of "calling CQ, no S&P" with a zero "callsign gain"
> worth 10dB of antenna gain (i.e. callsign gain = -10dB)?
> - would better conditions result in higher QSO difference?
> - would self-spotting be of any help (none of us used it - each of us was
> spotted only 18-22 times)
>
>
> I would like to hear your thoughts.
>
>
> Robi/s53ww
>
>
>
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