Discone vs Diamond X30A on receive

[dkcorlfla]

Hi all, I found this interesting and wanted to share. I have been playing around with SDR and rtl_433 and noticed when I have the SDR hooked up to my discone scanner antenna I do not receive anything. When I hooked it up to the Diamond X30A vertical it started to pull in tons of stuff. I'm getting lots of temperature sensors, security systems, TPMS reading from cars in the area.

434 Mhz is a bit under the design for the X30A but it's still pulling in the weak sensor signals.

Really a bit surprised at the day and night difference.

 

[kb1fua]

Hi all, I found this interesting and wanted to share. I have been playing around with SDR and rtl_433 and noticed when I have the SDR hooked up to my discone scanner antenna I do not receive anything. When I hooked it up to the Diamond X30A vertical it started to pull in tons of stuff. I'm getting lots of temperature sensors, security systems, TPMS reading from cars in the area.

434 Mhz is a bit under the design for the X30A but it's still pulling in the weak sensor signals.

Really a bit surprised at the day and night difference.

I'm not sure which discone you have, but...I had one from Diamond. My mag mount 2m antenna received much better, even on the 700 & 800 freq's. I ended up using my Tram discone, and it was even better.

So...I ended up swapping out the two. So now the new (not so great) Diamond is for the 6m/2m/70cm FM local stuff, and the old abused Tram on the Home Patrol II. I couldn't be more satisfied.

 

[dkcorlfla]

I'm not sure which discone you have, but...I had one from Diamond. My mag mount 2m antenna received much better, even on the 700 & 800 freq's. I ended up using my Tram discone, and it was even better.

So...I ended up swapping out the two. So now the new (not so great) Diamond is for the 6m/2m/70cm FM local stuff, and the old abused Tram on the Home Patrol II. I couldn't be more satisfied.

Your reply had me thinking maybe there was something wrong with my discone (Tram 1410) so I did a quick check using the NOAA WX stations in the area. It's working great on the VHF WX frequencies so I'm thinking the coax and connections are fine.

I did notice when I first got the antenna and checked it with my NANO VNA the SWR was excellent on 2 meters but not so good on UHF. Maybe it just does not like UHF. It does seem to be excellent on the air band, broadcast FM and 2 meters.

 

[mmckenna]

The X30 is 2 5/8th's wave stacked on UHF, and is 1/2 wave on VHF. Not surprising it outperforms.

Discone antennas are 0dB across the board, and as the frequency goes up, the radiation pattern starts rising above the horizon.

Even with the 434 stuff being outside the design of the X30A, it's not far out. Not surprising that it works better on UHF.

I've got a Diamond at home and a Telewave discone at work. They are not impressive performers when it comes to weak signal stuff. Their strong point is that they have such wide bandwidth.

 

[kb1fua]

Your reply had me thinking maybe there was something wrong with my discone (Tram 1410) so I did a quick check using the NOAA WX stations in the area. It's working great on the VHF WX frequencies so I'm thinking the coax and connections are fine.

I did notice when I first got the antenna and checked it with my NANO VNA the SWR was excellent on 2 meters but not so good on UHF. Maybe it just does not like UHF. It does seem to be excellent on the air band, broadcast FM and 2 meters.

Well, I'm glad your coax, etc is good. Yeah, it maybe like mmckenna says.
I'm lucky enough to be in shot of the three or four tower sites for the digital public safety stuff, and analog.
Good luck!

 

[db_gain]

The disconey wiki tells you how to calculate a disconey for best performance on the freqs of interest;

Discone antenna - Wikipedia

en.wikipedia.org

 

[merlin]

You have a problem with your discone setup. If your only change is discone to diamond, you likely have a bad coax connection at the discone.
Albeit discones have little or no gain, you don't need it with any scanner I know of.
In my case, a discone, 35 foot AGL, LMR400 coax, the reception is way to hot for all but very distant TX sites.
Yea, I get TPMS also, especially trucks going by.
The Diamond being band specific, yea, it should receive better within its range as mcckenna points out.
I did check my antenna system with a Nano VNA, from 100 MHz to 950 MHz it was flat then rolled off to -20Db at 1 GHz.
A note, I also use my discone with an XG-100 on 2 meters, 70 Cm, and 33 Cm and works great for an omni.
With my UV-5K(8), it works great on 1.25 meters.