Can't agree. If you're going to use a dehumidifier only, you won't get any results.
The condensation of moisture on the interior surface of RV windows is a function of the temperature of the window and the amount of moisture in the air inside the RV. To reduce the condensation you must raise the temperature of the window
and reduce the amount of moisture in the air.
The temperature of the windows may be increased by installing dual panes or
storm windows (easy to DIY), or turning up the thermostat for the furnace.
The amount of moisture in the air may be reduced by ventilation when operating the furnace, operating the air conditioner, or operating a
dehumidifier (domestic one, rv dehumidifier, crystal one... whichever you like the most). If ambient temps allow for operation of the furnace, then ventilation via an open window etc can be effective at moisture removal (
here's a good thread on topic). Also, ventilation will bring fresh air into the space. Leave vents open to let moisture escape - especially so whenever cooking and showering.