[MilCom] Antenna question

[Tim Cailloux]

Stavro wrote:

> I was thinking of getting this antenna 
> http://www.grove-ent.com/ANT4.html before we leave for Washington 
> state. It can be used in doors. Your thoughts?

My only hesitation (as an RF engineer) would be using it indoors -- it 
has a 20dB gain preamp built in which has the potential to pick up a lot 
of ambient noise when used indoors (there is much more RF noise present 
inside than outside), especially as it is a broad-band preamp 
(indicating that there is minimal filtering on the input).  The problem 
with this setup is that it is possible to overload the preamp with a 
nearby strong signal which would cause an overall degradation in the 
strength of the received signals.

Having said all that, it is designed for indoor use and the MT review 
claims that it has high overload immunity.  It is directional, so you 
will have to orient it in the direction of the transmitter you are 
trying to detect.  Situating it near an outside wall (or, even better, a 
window) is probably the best configuration for the antenna.  (Unless you 
live in a house with Low-E windows.  Those windows have a metal film 
that really discourages RF.)

Without knowing the full details of your particular usage needs, it 
would be hard to really say if this was the best antenna.  If you were 
near enough an air field, for instance, to see the activity but couldn't 
hear it with your stock scanner antenna, I would give it a shot.  
However, if you're on the other side of a hill or on the other side of 
the city from the transmitter in question, it may help but it would be 
hard to say without actually trying it first.

For general reception, a discone antenna is the generally preferred 
broad-band receive antenna, but it would be interesting to hear your 
results if you do decide to get this log periodic.

There's an RF answer for you -- it may work but I can't say for sure!  
(Think about how much fun when you go up in frequency to 2.4GHz and have 
to make accurate analysis of point-to-point links or coverage 
predictions for an 802.11 access point.)

tim

-- 
Tim Cailloux
tim at cailloux.com