Antennas in the end may extend your transmit but your device may not have enough umph to get back to your antenna.
Wifi bridge modems like wrt54gl on a cable gives the most reliable extension with less lowering of bandwidth.

My experience is that an alternative dongle at the device is more likely to increase range.
Dongle
ALFA dongles... Good Value

Power lookup

To start off we can look at the range vs rate test, which is designed to see how the device performs in response to fading base station transmit power. In the case of the iPad Pro, at 15 dBm transmit power the device reported -33 dBm RSSI (received signal strength indicator). It's important to note that the IEEE 802.11 standard doesn't really define RSSI beyond a unitless value, but in the cases we're interested in RSSI is really more a reference to received power, where dBm is the unit of power rather than watts due to the huge differences in power from good to poor reception. However, in the interest of focusing on the rate at which throughput decreases the test sweep in transmit power was 0 dBm to -50 dBm with a 5 dBm step. With this sort of data, we can actually see the kind of throughput that the device sustains for a given RSSI level and for a given transmit power. Of course, there are a number of other statistics that can be examined here as previously discussed, but basically the main takeaway is that the iPad Pro is capable of sustaining 600 Mbps and approaches 0 Mbps at -45 dBm transmit power. Given that we’re looking at a ~47 dB path loss from the transmitter to the receiver, this basically means that the iPad Pro is capable of sustaining non-zero throughput all the way out to roughly -90-95 dBm RSSI.

If you think back to the explanation of the physical layer of Wi-Fi, the reason why this is important is because received power is not quite the same thing as signal to noise ratio. While having high received power does improve your signal to noise ratio, if your receiver has a great deal of phase noise to begin with from poor amplifier design or some other issue in the chain, your through.

Maximum Transmit Output Power in the ISM bands

Several of the FCC part 15 rules govern the transmit power permitted
 in the ISM bands.  Here is a summary of those rules:

1. 1. Maximum transmitter output power, fed into the antenna, is 30 dBm (1 watt).

   2. Maximum Effective Isotropic Radiated Power (EIRP) is 36 dBm (4 watt).
      You can obtain the EIRP by simply adding the transmit output power, in dBm, to the antenna gain in dBi  (if there is loss in the cable feeding the antenna you may subtract that loss).

   3. If your equipment is used in a fixed point-to-point link, there are two exceptions to the maximum EIRP rule above:

      • In the 5.8 GHz band the rule is less restrictive. The maximum EIRP allowed is 53 dBm (30 dBm plus 23 dBi of antenna gain).
      • In the 2.4 GHz band you can increase the antenna gain to get an EIRP above 36 dBm but for every 3dBi increase
      •  of antenna gain you must reduce the transmit power by 1 dBm. The table below shows the combinations
        
      • of allowed transmit power / antenna gain and the resulting EIRP.

https://www.fcc.gov/oet/ea/fccid

16dbm is .0398 watts.