Re: TV antenna...
There is no difference between a digital antenna and an analog antenna, except for marketing hype. The antennas pick up a particular set of frequencies, while digital versus analog is the waveform used for encoding and decoding the picture and sound on that frequency.
That being said, during the transition in the states, most digital TV was on UHF. During that time, most stations had two transmitters on the air. For example, analog 6 would be on VHF 6, and digital 6.1, 6.2, and 6.3 would really be on channel 35 or something. Antennas like the Phillips are high-performance UHF-only antennas. The Phillips worked great during this period (my boss brought one to work to try out) because VHF was almost completely analog.
After the transition, each station got to pick which channel to stay on. Did they want to turn off analog 6 and digital 35 and turn on digital 6, or did they just want to turn off analog 6 and keep digital 35 where it was. The UHF-only antennas suddenly became not so good when many or most stations shifted to their old frequencies.
It is important to note that all the antennas suggested in this thread have built-in preamplifiers. A good, low-noise preamplifier is crucial to fringe area reception, and is important when the antenna metal is the wrong size for naturally tuning the channel. A full-sized channel 2 antenna should have rods that extend 52 inches on either side of the boom. A channel 15 antenna would only need rods that extend 5 or 6 inches on each side. The rod length for natural tuning goes down as the channel number goes up. The preamp helps make up for the mismatch.
The antenna Smitty has is the best one to meet the parameters you described - omnidirectional, non-retracting, useful in motion.
A problem with omni-directional antennas is multipath reception. You may pick up multiple beams from the tower to your antenna. When signals are reflecting off of urban buildings or the Rockies, a beam that bounces off four or five obstructions will take longer to reach your antenna than a beam that bounces only once or twice. On an analog picture, this produces "ghosting" where the late beam will display a second head on a person to the side of the one displayed by the earlier beam. On a digital signal, late ones and zeros arriving with near equal strength may cancel out the digital information, causing the picture to freeze up or not lock in.
A directional antenna is not practical in motion, without gyro-controlled steering like the mobile satellite set-ups. But a directional antenna can be pointed to the strongest beam reaching it, and not pulling in so many weaker beams hitting it from the sides with different arrival delays. This can greatly help eliminate ghosting and loss of digital lock.
The best of both worlds would be to mount an antenna like Smitty's for in-motion use plus stops in good signal areas, and have a pre-amplified directional antenna like Griff's in a storage bay to be able to set up when parked in a fringe or multipath area. An connector can be pre-wired for the directional antenna with an A/B selector switch to pick antennas.
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.