Indoor antenna for P25 monitoring via SDR

[thegriff]

I've recently setup my SDR system to monitor Atlanta public safety traffic. I suspect I am getting some multipath issues considering I am about 2 miles from a tower to the south and the same from a tower to the north.

Complicating things is my living situation as I'm an apartment dweller with no balcony. I have the famous RS-800 now and it works ok but I'd like to get a better decode rate.

From the sounds of it my only option will be to get a YAGI antenna though if there's something I can do to make my RS-800 "reject" signals from the north I'd be open to the idea.

All that said, I was wondering what sort of suggestions people might have. I like the looks of this model but fear the "wideband performance". For not too much more I could get something more focused but uglier.

I'm also wondering what sort of grounding, if any, I'll need to do for an in-house mounted antenna.

Thanks in advance for the suggestions and help!

 

[iMONITOR]

Consider a corner reflector antenna:

 

[Jimru]

Here is another choice from ScannerMaster:

http://www.scannermaster.com/produc...k=gdfV24250_a_7c1511_a_7c5024_a_7c01_d_541821

The corner reflector suggested might be cheaper, though!

 

[KD4YGG]

Another option

Supersonic HDTV and Digital TV Indoor Antenna 927517 - Micro Center

 

[iMONITOR]

The corner reflector suggested might be cheaper, though!

Actually no, it cost $234.26. That particular one is a commercial grade antenna, built like a tank!

PCTEL Maxrad 806-960 MHz 8.5dB Corner Reflector Antenna - WirelessUnits.com

You could probably find something cheaper,

 

[KC8ESL]

I think the bigger problem we need to discuss is why you are 2 miles from the tower and you have sloppy reception. A rubber duck antenna with -6dBi of gain should be fine. A yagi will pull in stations 20 miles+ away.

Are you on the ground floor of your apartment or in higher elevation?

 

[iMONITOR]

I think the bigger problem we need to discuss is why you are 2 miles from the tower and you have sloppy reception.

"I suspect I am getting some multipath issues considering I am about 2 miles from a tower to the south and the same from a tower to the north."

This is why he's having a problem. Simulcast systems that transmit the same signal, on the same frequency, at the same time, can be a real quagmire for the scanner listener. I know! In Macomb County, MI, the MPSCS has 9 tower/sites in the area!

 

[KC8ESL]

I live in a county where we have 5 simulcast sites and I can say that higher gain (even if it was directional) did not help issues at all.

Lower gain antennas centered in the house as low as I could get it worked best for me

 

[Jimru]

So it's better to combine a highly directional antenna with attenuating the signals?

Makes sense, actually!

 

[KC8ESL]

Well, I suppose that would work out well. If anyone tried or tries this, please advise on the results.

 

[RonnieUSA]

I use the antenna that came with my SDR, and it does very well on the 2 UHF, and 1 VHF frequencies that I listen to, but they are local.
I'm within 4 miles of the repeaters.

 

[thegriff]

Over the past couple of weeks I've tried various things including trying to make my own corner reflector. Thank you for that suggestion.

I believe it's come down to a matter o not having enough signal strength, particularly in the evenings. My big problem is I'm not sure exactly what DB level I should be looking for in SDR#. Research on that to come.

My apartment is on the fourth floor of four but there is another building of equal height in front of me and one to the side as well. These two buildings may block signal from one tower.

The other tower is behind my building by 2 miles but there are a myriad of apartments (including the majority of mine) between the antenna and the outside world.

I've ordered the new Mini2 dongle from Nooelec in hopes the higher sensitivity and better signal to noise ratio will help me. I also returned the rubber duck antenna after determining it wasn't pulling in the signal any better than the stock mag-mount that comes with the RTL dongle.

Thank you all for the replies. I've not posted because frankly all this experimentation with results has me feeling a bit down on the whole SDR concept at the moment. (Read: I wish I had the $$ for an X36 or WS1080.)

 

[quantumradio]

I have also had a lot of trouble with multi-path and multi-tower simulcast. I found i had to relearn what works with rf from simulcast. The usual "antenna a high as possible" worked great back in the day but after experimenting with several directional outdoor antennas at various heights, care to guess what works best? A high gain antenna IN MY BASEMENT aimed mostly into a block wall. Not intuitive but the key is to find that magic spot that gets a single reliable rf path. If you have tons of gain the radio's attenuator can help. I've heard also a homebuilt coffee can "cantenna" can work wonders as it provides high rejection from an adjacement tower (assuming there is a significant degree of directional differential) but mutipath relections can be a killer. Sometimes the best solution is a different geographic location :/ I've also detemined that a clean signal will make all rigs sound great and a multipath signal will make them all sound like crap. Aways focus on the signal.