Amazon.com: Bingfu 20-1300MHz Police Scanner Antenna Radio Scanner Magnetic Base Antenna HF VHF UHF Ham Radio BNC Male Antenna (2-Pack) Compatible with Uniden Bearcat Whistler Radio Shack Police Radio Scanner: Home Audio & Theater
www.amazon.com
There are many things I find highly questionable about that antenna.
An antenna that short is not going to perform at 20MHz.
Their claim of <2.0:1 SWR is completely meaningless on a receive antenna. And it's physically impossible for that antenna to give a flat SWR across the 20MHz to 1300MHz band like that unless it has a 50Ω resistor in the base (making it a useless antenna).
Claims of "compatibility" with a list of random/ancient two way radios is meaningless.
On the other hand, even a paperclip jammed in the end of the antenna jack on your scanner is going to pick up something, if the signal is strong enough.
2 antennas for $17.00 + free delivery should also be a red flag. That's $8.50 per antenna. Figuring the cost of shipping from China to the US then to your home, plus profits for everyone that touches it along the way would suggest that it's a very cheap antenna with poor coax and a crappy connector. Probably a $1 worth of materials once you figure in all the overhead and profits along the way.
I know what they claim, and can read the *one* review for the antenna. That one review is meaningless "Surprised at ability to now receive signals the stock rubber duck would not come close to. Definite dB gain, clear audio." Putting anything outside the vehicle will improve reception, even the previously mentioned paper clip. "Definite dB gain" means nothing.
Beware of cheap Chinese antennas. Yes, you'll see some improvement over the stock antenna used inside the vehicle. If your budget is tight enough that an $8.50 antenna is all you can afford, then by all means, go for it, you'll see a slight improvement. But, if your budget allows for more, you can very easily do better with a known good performer from a reliable American company that will stand behind their product.