Scanner Antenna

[scanner92]

I live about 12 miles from KMIA (Miami International) and I have a scanner. (PRO-94) I can only hear pilots of course because I'm too far for line of sight. What antenna(outdoor-attaches to roof, not portable) would any one recommend that I can connect to my BCN compatible scanner.?

[martgenia]

disconne antenna 25-1300  about 49.90 USD

[KB6HLM]

I would not recommend a discone unless you plan on monitoring other frequency's outside of the aircraft VHF band as the discone offers no db gain and can sometimes make IF image problems worse !

I would recommend

#1 : (J-poll) offers about 3db gain and its easy to build or cheap to buy
#2 : (1/4 wave ground plane) not as easy to build however cheap to buy, it offers no db gain but you can cut it for the aircraft band and that's a good thing
#3 : (5/8 ground plane) not easy to build and expensive to buy but offers 3db gain
#4 : (yagi) offers the most db gain however hard to build and expensive to buy also its very directional not the best thing with planes flying all over however if you live far from the airport this would be the right choice


The one I use is the 5/8 ground plane with a active multicoupler connected to 4 radios http://wingsandwheels.com/new%20page%2014.htm

Hope that helps

Glenn KB6HLM
Las Vegas, NV


Wow I just noticed this topic is a bit old (lol) but o well

[Squawk 7700]

I've been using the DPD Productions VHF Air Vertical Outdoor Model Antenna with good results.

http://www.dpdproductions.com/page_vhf_air.html#vhfairout

I can hear SFO tower which is about 12 miles away, and for my feed setup you can hear Oakland Tower which is about 4 miles away.

Here is a snapshot of the DPD Productions antenna. It comes in PVC grey, but I painted it and dressed it up a little . http://www.flickr.com/photos/34848377@N07/3929743251/

Ken

[KB6HLM]

The DPD antenna looks nice but it's interesting to note that they list there 1/2 wave vertical antenna with a Gain: 2.6 dBi  ?

PLEASE take note as this is very MISLEADING  !  and confusing to the reader who dose not understand antennas  

Here is where it gets tricky 0 db is often considered equal to 2.15 dBi  

Now lets go back to the start they list the antenna with a Gain: 2.6 dbi  Remember 0 db is often considered equal to 2.15 dBi

To sum it up here, the antenna has 2.6dbi about = to 0.45db gain over a 1/2 wave dipole (reference) hope I didn't loose you there

Antenna gain is sometimes measured as "x dB above a dipole", which means that the antenna in question is being compared to a dipole, and has x dB more gain

So what on earth is DPD comparing there 1/2 wave vertical to ?  
    

73s
Glenn KB6HLM

[DPD1]

I believe you're making some assumptions... It's not a dipole and it doesn't say that it is on our site. The angle influences gain, and the angle on that model is about 48 degrees. Typically, the angle on a standard dipole is going to be around 65 to 70. If anything, we understate some specs. Our rail and AIS models were tested by a very reputable government contractor, and those actually showed 3.6 at the resonant freq. We list it as 3 on the site. Theory is great, but there are small variances in actual practice. We aren't comparing to theory. I myself have often been surprised while building prototypes, at how different something can actually perform 'real world', compared to the theory of what it should do. Sometimes for the better, sometimes for the worse. However, I will be the first one to admit... It is in fact a numbers game... If I had my way, I wouldn't even put up a gain number. But that is what the consumer looks for. However, I don't know who would be foolish enough to purposely lower their figures to the absolute lowest number they can calculate it to, when no other manufacture is going to do that... Unless they secretly wish their business to fail.

Dave
DPD Productions

[KB6HLM]

I believe you're making some assumptions... It's not a dipole and it doesn't say that it is on our site.

I believe your correct !!  after going over your ad again I see it dose not list a 1/2 wave Vertical Dipole at all, my bad there (sorry about that chief)

I do agree with your quote

I wouldn't even put up a gain number. But that is what the consumer looks for

However I beleave antenna gain should be listed as (dBd (decibels over dipole) not dBi

0 dBd = 2.15 dBi It is vital in expressing gain values that the reference point is included. Failure to do so can lead to confusion and error however many manufacturers continue to do so !

Anyway without getting into a long debate over antennas I would like to thank you very much Dave for your post and clearing that up for us


Glenn KB6HLM

[martgenia]

It´s an old topic, but useful since everyday someone is browsing and finds the site and learns something with discusions like this, and yes, I recommended a disconne antenna presicely because sometimes (at least here) airport becomes lazy and you hear police/fire/ambulance activity outside then you can swith on the EMERGENCY scanner to listen to that, connected to the same antenna...