Three years later and a mini-review ....
I just picked up the Apex 700DTA and am very happy with it. I apparently got the earlier production model with light-colored knobs and not the latest black knobs.
However, I am only using it with higher-end receivers like a Commradio CR1a, and for now a Kenwood TS590s transceiver (rx only of course!)
At first I was hesitant about the lack of a gain control, but the Apex seems very well under control. The 20db of amplification to the supplied 2-foot whip is about as efficient as my 18-foot non-resonant vertical fed with a 4:1 unun. Note that the top bnc connector is designed to attach to a small whip, and NOT a low-impedance piece of coax. Yes, one could change the size of the whip, but at some point, you are building something very different from a small amplified antenna.
So - no overload issues. Basically the unit is acting similarly to about 15-20 feet of tuned wire. Outside of course. Inside near a window, there is a bit of attenuation inside the house, but not as bad as I thought it would be. 20 feet of wire to a portable *may* be a bit too much, but I cannot really comment on that since I have given up on most portables.
The construction is superb and there are some thoughtful touches. The case is gasketed with a dedicated channel. Screws to allow access for the 9v battery don't fall out into the grass or carpet. It comes with about 10 feet of what appears to be quality RG-174 coax and bnc connectors. Portable ops are very nice, but of course this unit is NOT rated to be outdoors in rain or moisture.
One of my major concerns was making sure that the coax itself isn't the antenna. I notice no difference in reception when handling the coax, nor any change when I put some heavy ferrite choking on it. Touching the metallic power switch did not change things at all. Good!
The unit is very high-q. That is, aside from choosing the proper preselector band, the tuning control is VERY touchy. It is manageable, and if a portable WAS getting overloaded, you could detune it slightly to act like an rf attenuator I suppose. Once you tune it, you can go across a band without having to tweak it again, unless you are very low in frequency, like below 4 mhz where you'll want to touch up when making large frequency excursions. But, having to tune it may be an inconvenience if you have this on the window-sill, and your operating position is 10 feet away.
I have not noticed any weird squeals or other bad noises when placed close to, or even on top of the receivers.
While I have not finished full evaluation of it, so far so good. I need to take it into a contest to see how it handles massive rf exposure. At the end of the day though, one has to figure out if using the equivalent of about 20 feet of wire with a 2 foot whip is worth it. Under certain circumstances, the small footprint of the 700DTA may be more convenient than stringing 20 feet indoors - and much easier to find a noise-free "hotspot" with.
So if one was expecting the equivalent of 120 feet of tuned wire antenna - this is not it. And thankfully so.
Note that this unit is NOT something to transmit into, yet after about a minute of playing around, I accidentally hit an auto-tune function on the Kenwood transceiver and thought that even at 5 watts, I just kissed $180 down the toilet. Don't ask me how, but it survived! This is not a recommended procedure of course!
I like the 700DTA so far - it is exactly what it is and built very well it seems. Could you do the same with 20 feet of wire, a tuner, supports, and making sure that the wire doesn't cross through some noise zones indoors? Sure. But the Apex's small footprint makes it easier. Choices .....