Does admob fillrate depend on the first ad request?

my application is designed in such a way that new AdView is created in my java code each time before the ad is to be shown. In other words I don't have admob AdView element in my xml layout but call this code periodicaly after a certain timeout:

AdView adMob = new AdView(activity);
    adMob.setAdListener(this);
    adMob.setRequestInterval(0);

and in the on开发者_Go百科Received callback of the AdView I add the received ad to the layout via the handler:

public void onReceiveAd(AdView adView) {
    Log.d(AdHandlerUtils.TAG, "AdMob success");

   myActivity.handler.post(new ViewAdRunnable(adContainer, adView));

}

I am able to observer test ads and sometimes real ads. Moreover admob statistics shows the figures for both requests and fillrate columns. But the problem is very low, about 15-20% with my refresh rate set to 30 seconds. I have about 100k requests and 20k impressions.

The question is, could the call to new AdView(activity); be the reason for low fillrate? Does admob send some sort of config(any hashcodes?) info in the first request so that real ads are not always returned from server?

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Unfortunately, part of it is the fact that adMob is terrible. A lot of people consistently complain about admob's fillrate - personally each day is its own roller coaster, i get as high as 90% and as low as 10%.