[time-nuts] Difference in antennas

[Taka Kamiya]

I have been looking antennas.  Prices seem to range less than 30 dollars to more than 500 dollars.  Some are 20db gain and some are 40 db gain.  Some are specified as marine use only.  Some are specified as timing use.  Some doesn't say anything at all.  Power supplies are different.
Other than obvious, antenna is an antenna, isn't it?  It captures L1 signal, amplify it and send it down the coax.  What makes one more costly than others?  What makes one timing antenna and one navigation antenna?  It doesn't make sense to me.  

I did some simple experiment with 26db, 40db, and magnetic stick on type.  I didn't really see significant difference.  Signal level itself even wasn't all that different.  I have nearly a clear sky view 360 degrees above 30 degrees above horizon.  In some directions, clear view to horizon.  My feed is Timewave type.  So It may not be the best but nearly ideal.  

Can someone shed light on this topic?  (of course, I know some antenna has integrated receiver.  I am not talking about those)

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(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG