Usually all portable routers do not have an external antenna. :-(
Remember: Sending out a strong signal does not mean that you can reach a broad audience. It is like shouting in a canyon. The people below may hear you, but you can't hear the answer. This also applies to wifi signals. The communication partner needs to send back in the same strength for a reliable connection.
Up to a certain level you can get a farer range, because -especially with directional antennas- you have a clearer inbound signal, but it still may not work well.
Remember: Sending out a strong signal does not mean that you can reach a broad audience. It is like shouting in a canyon. The people below may hear you, but you can't hear the answer. This also applies to wifi signals. The communication partner needs to send back in the same strength for a reliable connection.
Up to a certain level you can get a farer range, because -especially with directional antennas- you have a clearer inbound signal, but it still may not work well.