How come that you selected that particular discone antenna? It is a special version to optimize 145MHz for radio amateurs and also work well at the neighbour frequencies around it like the NOAA ones. But it will also trash reception in most other frequencies, like vhf airband, as it interferes with the discones function and the good SWR are only at multiples of that 145MHz frequency.
I would suggest that you try without that top element with the coil in the middle and see how it receives especially in the UHF and 800Mhz bands. Also remember that a discone like that also have more than a 10dB loss at 900MHz from signals at the horizon, as the direction are pointing up in the sky. Sirio's diagram show that the -3dB loob are pointing up in the sky at a 60 degree angle at the 900Mhz band.
That top element makes this discone works more like a GP antenna in the 135-160MHz band, but that might work for you if that frequency band are where you would like to focus your reception.
/Ubbe
If this was Facebook, I would give you a "heart" for your post.
That is great information.
I selected this antenna because I vaguely gathered (on my own) I needed an all purpose antenna for a scanner like the Homepatrol-II. And I read some discussion about disconne antennas. Then I went to Amazon and this antenna got good reviews and seemed like what I would need in my novice judgment. From the product description: " This antenna covers the frequency range of 100-2000 MHz and, due to its broadband concept, is suited for scanner and monitoring applications." .
At least, as a positive, I am pretty much not scanning anything over 155 Mhz - pretty much standard police and fire and forest service (since I live right on the tree line of a forest though you can't tell by the picture). But I do see there are some extender and associated frequencies in the 400, 700 and 800 range and I will give some testing without the top element (very easy to unscrew from the antenna body).
You are right about NOAA. I hardly listen to NOAA, but it really did go from one channel only and absolutely nothing else, to three channels as clear as a bell.
The VHF air band performance is there, but I think it pretty much matches what I am getting with my old Uniden BC XLT 710 with just its simple "plug in" antenna in the back. So the airband is nothing special.
In the 150 Mhz range, where I am doing a lot of listening, I would say it was as exponential leap forward. And, maybe, surprsingly, the 40 MHz (California Highway Patrol) is a lot better.
The reception has improved dramatically with the antenna though. I went from 1 NOAA weather station to 3 as a matter of objective measurement, and I am pulling in a lot more of everything else and a lot more clear. This Sirio antenna sure seems well made.
