Given this situation, you could still build up a rough picture of what the world looks like by sweeping your straw in a regular pattern and recording your impression of the brightness at each point in the sweep. The amount of detail you could create in your picture would be related to the diameter of the straw and your ability to discern small changes in brightness. In a radiotelescope, these parameters would correspond to the telescope beamwidth and sensitivity, respectively. Radio astronomy theoretically concerns cosmic signals at any frequency less than the frequencies of light. A wavelength is the distance traveled through space by the wave during of a single oscillatory cycle.
Higher frequencies translate to shorter wavelengths.
The relationship between the two measurements is set by the speed of light. You will often, for example, hear the molecular hydrogen line frequency region of 1,420 megahertz referred to as the 21 centimeter band. There are practical limitations to our ability to receive many of these frequencies, especially from our protected position beneath the shield of the earth's atmosphere. Frequencies below 15 Mhz or so, are rarely used due to absorption of these waves by the ionosphere. At the upper end of the frequency range, limitations are imposed by the technology needed to receive signals with such tiny wavelengths.