Sparks31 has a brief article up on Covert and Hidden Antennas.
Whether you are setting up a field radio station for communications or a monitoring post for SIGINT operation, the antenna is the linchpin of your setup. The best radio in the world is useless without a decent antenna.
Let’s take a look at a common antenna design, one I’ve used with much success over the years:
This is a discone antenna. I have one at my eastern QTH. For a first antenna it’s not bad. It makes an adequate wideband receive and transmit antenna for the VHF and UHF bands. It’s a unity gain antenna, but its advantage is that you can get on the air with multiple VHF and UHF bands with a single antenna. For permissive urban and suburban environments it’s a good choice.
However, it sticks out like a cow in church. Anyone with a modicum of RF knowledge will know what you’re doing when they see one on your roof. Not a problem in permissive environments like the U.S. today, unless you live in place that has a H.O.A. which restricts antennas, or for whatever reason(s) you want to keep your RF activity under wraps.
Antennas are one of those things that you can easily roll your own out of whatever stuff you have lying around your workshop, homestead, or wherever.
Marconi spins in his grave every time a ham buys an aerial instead of building it.
– Joe W1GFH
With that said I’ll state up front that buying a bunch of stuff and putting it in a bag or box and then never using it does you no good. You have to use your gear, whatever it is. Everything I own is used hard and heavy- not abused, mind you, responsible people care for their equipment– but used. I know the ins and outs of what I own, and you can be darn sure that if I suggest it, I not only use it, but I can show you the results. So for the folks that buy a case of Baofengs on Alibaba and then never take them out of the box, you’re doing yourself a disservice. Whether you’re buying a $20 Baofeng, a $200 Yaesu, or something somewhere in between, use your stuff and if it fails, you’ll know its limits. The next thing I’ll say is I definitely don’t require anyone to ‘be a ham’ or have any prior knowledge before coming to class. But having people to talk to is the most important part of the learning process, and like land navigation, marksmanship, and basically anything else, its very much a perishable skill. There is a learning curve to communications, especially emergency and field expedient uses, so having stuff just sitting around ain’t doing much for anyone.
…[O]ne of the common questions I get is regarding the length of the reports when they’re sent. If interception is a concern, and it always is, how do we shorten this up or obscure it to the point of being useless to listen to? There’s a few answers to this question, including going high tech/more complicated/more expensive with equipment, more efficient antenna construction for directivity, and finally, creating a BREVMAT.
Tactical BREVMATs are created and included in your Signals Operating Index (SOI), they are recycled each time the SOI changes (which is usually a set period of time, and for missions, mission-specific). This information can then be encoded into a 
Lower Valley Assembly 