There are only four ways to increase the received signal.
Increase sending power (more powerful router signal)
Increase receiver sensitivity
Use a better transmit aerial
Use a better receive aerial
Or a combination of any two, three or all four of the above.
Making sure the upper and lower aerials are both vertical might help, or at least ensuring that they are aligned in the same fashion, as cross-polarisation also reduces signal pickup.
Cheers
Billy 8-{)



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