Discone vs Yagi vs X30A on 856 Mhz

[dkcorlfla]

Hi all, I thought some might find this interesting. I wanted to try and improve my 856Mhz reception in an effort to try and receive the Seminole County P25 system.

I purchased one of the cheap yagi antennas intended for improving cell phones but the frequency range was stated to be good for my target of 856 Mhz It had a female SMA connector on it so the hookup was simple.

Used my Windows 10 computer running SDRpp and DSP+ for the test. Not changes made when changing the antennas and I had the gain cranked up quite a lot. I think the results are quite stunning. From left to right: Tram 1410 Discone, Diamond X30A ham - not designed for 856Mhz and the 698-894Mhz Yagi Antenna ($25 on Amazon)

UniTrunker is now logging lots of P25 on the Seminole system but I'm getting a lot of simulcast distortion. I think I will use the logs to pull some TG and program my scanner and see it does any better. Looks like I'm real close to being able to pull it in.

 

[AB5ID]

Thanks for taking the the time to share, love to see real world experiences.

 

[bharvey2]

That doesn't surprise me. I use and SDR and SDR Trunk to monitor my local public services radio system. I started with a home brewed quarter wave ground plane but fought simulcast distortion. I switched to a yagi it it provided a vast improvement even while set up temporarily inside the house near my computer. Do you know the direction of the closest antenna site on your county's system? Rotating the antenna may provide some improvement in your reception.

 

[mdevoe]

Nice, I got one of those yagi can't wait to get it in the air. I tested mine at ground level compared to Larsen triband 25 ft up and it's pulling better. The tower is about 20 miles away. IM using sds100

 

[Enforcer52]

Discone's just do not perform well on the 700-800 band. I never recommend them to anyone wanting to monitor the 700-800 band, especially if more than 5 miles from a tower. The cell phone antennas work ok, but prefer the Omni X, the Wilson 30111 (8 element) or an 18 element 800mhz yagi.

 

[mdevoe]

Wish there were more test like this. Now I'm wondering about a yagi for 150 to 174 with a rotor

 

[dkcorlfla]

That doesn't surprise me. I use and SDR and SDR Trunk to monitor my local public services radio system. I started with a home brewed quarter wave ground plane but fought simulcast distortion. I switched to a yagi it it provided a vast improvement even while set up temporarily inside the house near my computer. Do you know the direction of the closest antenna site on your county's system? Rotating the antenna may provide some improvement in your reception.

The Seminole County should simply be to my North. Right now I'm playing around with the new yagi on the Orlando Simulcast system. I thought the control channel was to my east but after some experiments I'm getting great results with the yagi pointing south. The yagi antennas do have a deep null off the sides so perhaps I'm nulling out some of the other transmitters and getting better reception.

 

[bharvey2]

The Seminole County should simply be to my North. Right now I'm playing around with the new yagi on the Orlando Simulcast system. I thought the control channel was to my east but after some experiments I'm getting great results with the yagi pointing south. The yagi antennas do have a deep null off the sides so perhaps I'm nulling out some of the other transmitters and getting better reception.

Depending upon the size of the system and the orientation of the individual sites, you might have two sites within the same reception window of your yagi so simulcast distortion can still present a problem. If that's the case and the sites are far enough away from one another, you might be able to point your antenna in such a way that you picking up one site but the other is outside of the main reception lobe of the antenna's pattern.

 

[dkcorlfla]

Wish there were more test like this. Now I'm wondering about a yagi for 150 to 174 with a rotor

I played around a bit years ago with a 2 meters VHF ham 3 element yagi with a low cost TV rotor and found it made a big difference. The 2 meter ham band is just under the 150 to 174Mhz range.

Been thinking about making one for the railroad stuff around 160Mhz. They are not all that hard to make but do require at least a NanoVNA to test and tune. PVC, aluminium rod sections cut to exact length and a hairpin match.

I made one recently for 186Mhz and point it up to receive TV station carrier signal from a TV station near Tampa that bounce off the bottom of aircraft flying overhead (poor mans passive radar). Fun stuff!

 

[dkcorlfla]

Update: after playing around with the antennas this morning I have found the yagi is trying to work on the Seminole County system but I'm getting too much simulcast distortion for solid copy (maybe 50 % copy or so) Seminole County is 15 miles + to my north and I need all the gain the yagi offers to begin to receive it.

Then I tried the yagi on the local Orlando simulcast system and found the gain the yagi has causes a lot more simulcast distortion. I tried moving the directional antenna around many times but was not able to tame the distortion any.

The Diamond X30A even though it's not designed for 856Mhz has a nice clean signal and it works much better on the closer Orlando system. The Discone also works better then the yagi on the Orlando system.

So I guess as far as trying to receive the simulcast systems less might be more as far as gain goes.

I think my next plan will be to try and make a j-pole for 856Mhz and see how it does. I would like to get my X30A back for it's intended use but I'm running out of places to install another antenna so I will be taking the yagi down and trying the J-poll in a stealth flag poll mount.

 

[bharvey2]

Update: after playing around with the antennas this morning I have found the yagi is trying to work on the Seminole County system but I'm getting too much simulcast distortion for solid copy (maybe 50 % copy or so) Seminole County is 15 miles + to my north and I need all the gain the yagi offers to begin to receive it.

Then I tried the yagi on the local Orlando simulcast system and found the gain the yagi has causes a lot more simulcast distortion. I tried moving the directional antenna around many times but was not able to tame the distortion any.

The Diamond X30A even though it's not designed for 856Mhz has a nice clean signal and it works much better on the closer Orlando system. The Discone also works better then the yagi on the Orlando system.

So I guess as far as trying to receive the simulcast systems less might be more as far as gain goes.

I think my next plan will be to try and make a j-pole for 856Mhz and see how it does. I would like to get my X30A back for it's intended use but I'm running out of places to install another antenna so I will be taking the yagi down and trying the J-poll in a stealth flag poll mount.

If you haven't done so already, try turning down the gain setting on your SDR while using the yagi.

 

[dkcorlfla]

If you haven't done so already, try turning down the gain setting on your SDR while using the yagi.

I was just getting ready to try the Seminole County system again and will look for any gain settings in Unitrunker.

Good idea and I will see if if might help with the strong local Orlando system.

 

[dkcorlfla]

Update 2: I ended up giving up on the Seminole County system as it is just too far away. Decided to try the Orlando system again but this time I lower the yagi about 10 feet. Now instead of being over the top of the roof line with 360 degrees view it is now under the roof eve with the south blocked by the house. It made a huge difference! Now I'm getting 100% copy.