Hi Paul-
Thanks for reaching out. I'll try to give a brief summary.
Indoor antennas generally do not work well. YMMV based on building construction, window treatments, and other factors. One of those other factors, and it applies to both indoor and outdoor antennas, is RF noise. RF noise can come from many sources, and I won't go into all of them here. But generally you don't want an indoor antenna near computer devices and appliances. Again, YMMV and every situation is unique.
For a receive antenna a basic VHF antenna that meets any aesthetic requirements will be OK as long as you are within 5 miles of an airport surface area without any major obstructions. It is always better to have a "close to resonant" antenna - one that is cut for the frequency range in question. But not required and good results can be had with many types of antennas.
Goal 1: Hear the controllers.
Goal 1A (nice to have): Hear aircraft on the ground. Sometimes this can be difficult depending on airport/ramp construction and the receiver's physical location. Being up high is good for this.
Hearing airborne traffic is easy, unless your building blocks you in a certain direction.
For Approach controllers in this case, most of those radio transmitters are at DCA. There are other PCT (Potomac TRACON) transmitters in other locations (like ADW) but most of them are at DCA.
Hope this helps.
Dave
Hi firstly a shout-out to Dave and everyone providing these feeds, a lot goes into making this happen. Easy to take for granted a crystal clear tower feed to your cell phone in real-time until it disappears 
With the current gap on KDCA I wanted to experiment myself with a basic setup, got a Uniden BC355N, able to pick up DCA tower/ground/app/dep etc with the basic antenna indoors, but most of the transmissions are not very clear and have a lot of noise (adjusted squelch).
Any advice on a basic external antenna I can try. I was looking on Amazon and see a lot specifying frequency ranges such as 136-174MHz, isn't that outside aircraft band?
I am about 3 miles from DCA on the 16th floor of a building but may have some interference from my building and other tower blocks in the area.
Also interested in what location/factors result in the best reception - is it proximity to the airport, or to other transmission aerials in the area. I assume frequencies such as ground may be more localized to an airport but the Potomac approach/dep frequencies are being more broadly transmitted.
Sorry for the novice questions - any advice/pointers appreciated.
Thanks
Paul
