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7376RE: [BCD396XT] Re: A better understanding of P25 decoding

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  • Michael Hopkins
    Feb 12, 2013
    • 0 Attachment
      Sorry, but I have to take issue with John Stark’s comments about grounding a Yagi. Any Yagi will work with a scanner or hand held tranciever without being grounded. What IS important is that you use good quality coax as John suggests and that the coax braid is properly connected to the yagi and the scanner.



      That said, grounding an outdoor Yagi via the mast or a large diameter ground cable should be done for lightning protection, but it won’t affect the Yagi’s performance.



      Ground below a Yagi becomes important when the Yagi is close to ground in terms of wavelength. Since scanners are typically working in the VHF/UHF range, ground is typically multiple wavelengths below the antenna so it doesn’t really play a role.



      It does become an issue at HF frequencies since the wavelengths are very long and unless one has a very tall tower, antennas are likely to be within a wavelength of ground. Ground reflections and ground absorption then become issues. In any case grounding the Yagi itself isn’t the issue, but the distance above ground.







      Mike Hopkins K1VLB

      <mailto:Mhopkins735@...> Mhopkins735@...



      From: <mailto:BCD396XT@yahoogroups.com> BCD396XT@yahoogroups.com [ <mailto:BCD396XT@yahoogroups.com> mailto:BCD396XT@yahoogroups.com] On Behalf Of John Stark
      Sent: Monday, February 11, 2013 3:43 PM
      To: <mailto:BCD396XT@yahoogroups.com> BCD396XT@yahoogroups.com
      Subject: Re: [BCD396XT] Re: A better understanding of P25 decoding





      Directional beams as you put it work great IF installed and used properly. A Yagi antenna is exactly what is called for in the OP's case since they are right between two sites. Using a proper Yagi antenna and coax will get the right results. A lot of people will not properly ground the antenna and or use cheap coax, both of which defeat the purpose of using the yagi antenna. Poor or improper grounding lowers the antennas ability to receive signals and block unwanted signals as much as using poor quality coax affects reception.
      I use a yagi and being east of Indianapolis I still am able to receive some I'll Star com sites as well as many Ohio MARCS sites in addition to most of Indiana SAFET sites using the yagi. Some frequencies I can receive three or four different systems on. The antenna is only 25 feet up but it has proper grounding and 50 feet of LMR400 coax. On one frequency If I move the antenna one direction I pick up one site and then turn it 180 degrees I will get a different site yet both sites are almost the exact same distance from me and using the same power. Take the ground off and I don't get much of anything. Put the ground back and the site I am aimed at is nice and clear with no interference from the other site. If I used cheap coax with lousy shielding I'd get the same bad results as signals get through the shield from both sites as well as other signals degrading everything.
      In addition I am less than 1/4 mile from a cell tower and have four other cell towers within five miles. Three can be seen from my house. Add in an Indiana SAFET site five miles away that can also be seen from home yet even with all of that I can find the Control Channels for 150+ trunked systems and sites in good conditions using the yagi.
      The point being proper installation will do the job the OP needs to hear the site he wants to hear.

      Sent from my Verizon Wireless 4G LTE DROID

      dataman60435 <mailto:dataman60435%40yahoo.com> dataman60435@...> wrote:

      >Its really experimental, digital is rough, not like regular freqys...I have had people send me email that directional beams did not work....I have a RS 25-1.3 grnd plane think its # 25-173 $29.00 with 35' RG6u in the attic and it receives three towers very well....I have the Channel Master 5094A (disc) up 25' with LMR400 and it works very well on same towers T102,126,113, and T125....Im too far south for T101-Dupage...I can also hear Chicago FD new 476-478 non trunked digital stuf...Took me awhile to figure out what to use....My own city joined Starcom and uses T113-Will Co but there "ENC" !....
      >
      >--- In <mailto:BCD396XT%40yahoogroups.com> BCD396XT@yahoogroups.com, Dan Simon wrote:
      >>
      >> Ok. Yes, I have gotten the feeling from some stuff I have read that I am right between towers. What is the best solution for that overall? Or is there one?
      >>
      >> Thanks!
      >> -Dan
      >> On Feb 10, 2013, at 2:01 PM, dataman60435 wrote:
      >>
      >> > I noticed ur in Geneva, im in Joliet, using outdoor antennas i monitor T113,102,126, the last one T126-Aurora u should be able to hear...T101-Dupage is very difficult to hear in alot of places...Even tho there is a new firmware upgrade if you don't hear the "CC" well ur not gonna hear Starcom Digital....My daughter is in Elgin, in the mobile going thru your town using the RS800 rubber duck T101-Lisle and in some spots i hear T115-Lake Co.....Your town is kind of in between towers.....
      >> >
      >> > --- In <mailto:BCD396XT%40yahoogroups.com> BCD396XT@yahoogroups.com, Dan Simon wrote:
      >> > >
      >> > > Yes I have. I am running 1.11.01, the newest firmware version.
      >> > >
      >> > > Thanks,
      >> > >
      >> > > -Dan
      >> > > On Feb 9, 2013, at 10:06 PM, Milton Engle wrote:
      >> > >
      >> > > > Have you installed the latest version firmware 1.11.something (requires
      >> > > > Updater version 3)?
      >> > > >
      >> > > > ----- Original Message -----
      >> > > > From: "kc9vzv" kc9vzv@>
      >> > > > To: <mailto:BCD396XT%40yahoogroups.com> BCD396XT@yahoogroups.com>
      >> > > > Sent: Saturday, February 09, 2013 10:13 PM
      >> > > > Subject: [BCD396XT] A better understanding of P25 decoding
      >> > > >
      >> > > > >I am trying to monitor StarCom21 in ILL but I am still (after about 3
      >> > > > >months of playing with settings) having issues with my scanner decoding the
      >> > > > >system. I upgraded my firmware and read through this
      >> > > > > <http://wiki.radioreference.com/index.php/P25_audio_decode_level_adjustment,> http://wiki.radioreference.com/index.php/P25_audio_decode_level_adjustment,
      >> > > > >but I feel like I am missing something obvious because a lot of the
      >> > > > >transmissions are still garbled. Any thoughts?
      >> > > > >
      >> > > > > Thanks!
      >> > > > >
      >> > > > > -Dan, KC9VZV
      >> > > > >
      >> > > > >
      >> > > > >
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      >> > > > > Yahoo! Groups Links
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