[CQ-Contest] ARRL-DX SSB (CQ WPX) : How were condx ?

Yannick (XV4Y) yannick.devos at online.fr
Tue Mar 27 20:00:31 PDT 2012


Just a follow-up about my antenna and the path to NA.

During last CQ WPX SSB I had only a few hours that I spend on 15m exclusively.
Saturday morning I had 30 minutes around 8am local time (01.00z) when condx should be good to NA.
Condx were Ok but not great.
Signals were down 1-2 points on the 2elts Moxon heading 15° compared to the vertical.
I was unable to find a good beam turning the antenna 15 degrees more or less.

Sunday evening (13-17z) I spend nearly 4 hours on 15m and the band was really hot.
The Moxon (at 330°) was 2 S-point better on european signals compared to the vertical.
I had plenty of S9+10db signals all over the band but it was tough to make QSOs!
I think my signal (with 100w) was arriving S7-9 but the band was full of QRM in Europe so many time I had to wait the frequency to be clear (not hearing the other stations) and at one time had an easy QSO.

More surprising later in the night, signals from NA were good also, around 1S even if slightly off-bearing.

I have two (temporary) conclusions from this :
- On the morning perhaps the path is not fully SP or LP and usually NA stations are bearing to JA, not me, making things harder to understand.
- Around 1 meter under my antenna I have a roof which frame is in metal. Length is around 10m... If heading 330°the main dimension is parallel to the antenna. Heading 015° perhaps the frame act as a parasitic element and modify the radiation pattern...

Ok, now I will bot bother you anymore with my (perhaps off-topic) antenna stories.
Hope to see you in the contest with more spare time next time!

Yannick DEVOS - XV4Y

Le 9 mars 2012 à 14:19, Yannick (XV4Y) a écrit :

> Hi Tom,
> Sorry for the delayed answer.
> Gain is over "real ground" as MMana computes it.
> The Moxon is around 11dBi when at the exact goal frequency, you quickly loose 1dB when going far from it.
> It is a Moxon on 15m but just a dipole on 10m. I got it working on 12m "by luck" with my TS-590s internal ATU doing its job.
> I was not expecting high gain on 12m and 10m so 1 S-point compared to the vertical is matching the predictions.
> I will soon try to add another reflector element on 10m to have it working like a jungle-job (G4ZU).
> The problem is that the modeling don't show a great improvement in gain while I loose all the back lobe.
> The reflector element characteristics seem also really touchy and while it will not make the antenna worst in some cases there is no gain at all in adding the element...
> We are going a bit out of topic for the "contest" list so I will not tell much more about the antenna.
> The truth is also that I am planning to write an article about that and want to keep the detailed undisclosed until it is published...
> Thanks for your help.
> 73,
> Yan.
> ---
> Yannick DEVOS - XV4Y
> http://xv4y.radioclub.asia/
> http://varc.radioclub.asia/
> http://www.qslwatch.com/
> Le 7 mars 2012 à 22:18, Tom W8JI a écrit :
>> <<<Yes I agree with you that condx can vary greatly with only hundred of miles, especially when condx are tricky. That's why I needed several opinions because it only has a statistical value. I was not asking for a definitive judgement over my antenna choice but more to know if I had to worry or not.>>>>
>> They especially vary when the distance is long and the path over or near earth's magnetic poles. :-)
>> <<<On 12m and 10m my beam is acting more like an "improved dipole" (8dBi gain calculated) and in practice I only see 1 S-point difference with the GP. Again that's coherent.>>
>> Over earth or freespace gain? A dipole should be about 8 dBi over earth, but only about 2.1 dBi freespace. Shouldn't the Moxon be 11 dBi or so over earth, and about 6 dBi freespace? Aren't they around 3 or 4 dBd typically?
>> 73 Tom 

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