Question 1

What's the gain of this antenna?

Accepted Answer

As far as I know the manufacturer has not published any gain figures. One does not get this kind of antenna to achieve gain. Its purpose is to provide a good signal in a compact package for mobile use. Also, its automatic tuning function only works with certain Yeasu products (e.g. the FT857). The ATAS 120A might theoretically have a slight dBi or even dBd gain on UHF and VHF depending on the quality of the counterpoise (grounding). However on HF amateur bands (7/14/21/28/50 mhz) it should have negative (less) gain compared to a halfwave dipole as it is essentially a compromise vertical that is shorter than 5/8ths or a quarterwave, with loading coils to compensate for the lack of electrical length. However with a good counterpoise (groundplane provided by bonding connections to the vehicle) reports indicate that it gives excellent mobile results (compared to other mobile verticals) when used in a vehicle.

Question 2

I'm reading that the radio tunes the antenna. I'm about to buy the 857d BUT!! do you need to but the antenna tuner made by yaesu for this To work

Accepted Answer

Most of the below answers are confusing. FT857D DOES NOT have a built in tuner. If you have a good resonant antenna no tuner is needed. There are some antennas that can tune themselves via various methods and resonance is obtained at the antenna not the radio. Almost any antenna tuner at the radio can tune many non-resonant antennas. Yaesu specifically makes a tuner that attaches to the outside of the radio but almost any automatic (I recommend) tuner will work. Ground your radio and have a good counterpoise for your antenna. Most of my antennas are resonant at frequency (most efficient) but an auto tuner is wonderful for mobile HF operation especially at the lower frequencies (ie. 160-80M) and you keep your eye on the road. JUst remember to initially tune at 5-20 watts. The yaesu antenna is not an efficient antenna but it is convenient. N8LB

Question 3

Will the atas-120a tune 80 meters

Accepted Answer

No, only down to 40 meter band. Google ATAS-120a to get the one-page operating guide in pdf format. It includes the operating range in the specs section.

Question 4

Tough question: I intend to use this antenna as base station on my 5th floor condo HOA (inside of window) will the inside house ground be sufficient ?

Accepted Answer

As a DC ground, yes it will work. You may want to add the ATBK-100 radial kit to improve the ground plane or add homemade radials to expand the ground plane. Hope this helps - 73s de KC5AJS

ASIN	B004UM9UL4
AntennaDescription	Radio
Best Sellers Rank	#1,157 in Radio Antennas
Brand	YAESU
Color	Black
Customer Reviews	4.4 4.4 out of 5 stars (85)
Impedance	120 ohm
Item Weight	0.27 g
Manufacturer	Yaesu
Maximum Range	40 meters
Mfr Part Number	ATAS-120A
Model Number	ATAS-120A
Number of Channels	7
Number of Items	1
Number of Packs	1
UPC	788026098729
Unit Count	1 Count

Yaesu ATAS-120A 40 Meter through 70cm Auto Tune Motorized HF/VHF/UHF Antenna For FT-857D, FT-450DandFT-897D ATAS-120

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