145.250 Repeater Status - 29 November 2014 - Back on the air!

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Luke Jenkins

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Nov 30, 2014, 12:39:36 AM11/30/14
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Tonight N7RPG and I did the final tune of the repeater cavities and got the 145.250 repeater back up on the air. We're using a 100w Motorola Spectra radio on TX, and another lighter duty spectra on receive. The APRS radio has been demoted back to RX only until we can get a second antenna up on the tower. We added a band pass cavity in line with each of the radios, tuned for the best VSWR we could tune up, which seemed to make a world of difference.

Rob took some screen shots using his awesome new spectrum analyzer, so I'll let him report back with all of the details.

John Sohl

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Nov 30, 2014, 1:01:37 AM11/30/14
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Is it still acting as an igate for APRS? 

Thank you for all the work you guys have done. 

John 

- - - -
John E. Sohl, Ph.D.
Professor of Physics
Weber State University
1415 Edvalson St., Dept 2508
Ogden, UT 84408-2508

voice: (801) 626-7907, fax: (801) 626-7445

On Sat, Nov 29, 2014 at 10:39 PM, Luke Jenkins <luke...@gmail.com> wrote:
Tonight N7RPG and I did the final tune of the repeater cavities and got the 145.250 repeater back up on the air. We're using a 100w Motorola Spectra radio on TX, and another lighter duty spectra on receive. The APRS radio has been demoted back to RX only until we can get a second antenna up on the tower. We added a band pass cavity in line with each of the radios, tuned for the best VSWR we could tune up, which seemed to make a world of difference.

Rob took some screen shots using his awesome new spectrum analyzer, so I'll let him report back with all of the details.

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Luke Jenkins

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Nov 30, 2014, 1:06:36 AM11/30/14
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Yes, but since we can't have two VHF transmitters active into the same antenna without some crazy gear, we had to put it into receive only IGate mode so you'll have to check on aprs.fi to verify that your packets have made it in. Sensitivity to the APRS radio doesn't seem to be affected, as we're still getting packets from KF6RAL-14 near Wendover and HARIN south of Burley.

At some point we'll get the second antenna mounted lower on the tower or somewhere else on campus to function as a fill-in digi.

-Luke



On Saturday, November 29, 2014 11:01:37 PM UTC-7, John Sohl wrote:
Is it still acting as an igate for APRS? 

Thank you for all the work you guys have done. 

John 

- - - -
John E. Sohl, Ph.D.
Professor of Physics
Weber State University
1415 Edvalson St., Dept 2508
Ogden, UT 84408-2508

voice: (801) 626-7907, fax: (801) 626-7445

On Sat, Nov 29, 2014 at 10:39 PM, Luke Jenkins <> wrote:
Tonight N7RPG and I did the final tune of the repeater cavities and got the 145.250 repeater back up on the air. We're using a 100w Motorola Spectra radio on TX, and another lighter duty spectra on receive. The APRS radio has been demoted back to RX only until we can get a second antenna up on the tower. We added a band pass cavity in line with each of the radios, tuned for the best VSWR we could tune up, which seemed to make a world of difference.

Rob took some screen shots using his awesome new spectrum analyzer, so I'll let him report back with all of the details.

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Rob Eckel

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Nov 30, 2014, 1:10:22 AM11/30/14
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I think google groups filtered my first message.  I'll send the images in separate emails.

Original message:

Here's a bunch of screen caps.  Some the VSWR ones that show us slightly off peak are probably not accurate anymore, since we tuned that up at the bandpass cavities but didn't take full-system captures afterwards.  Will have to update those next weekend.

On Sat, Nov 29, 2014 at 10:39 PM, Luke Jenkins <luke...@gmail.com> wrote:
Tonight N7RPG and I did the final tune of the repeater cavities and got the 145.250 repeater back up on the air. We're using a 100w Motorola Spectra radio on TX, and another lighter duty spectra on receive. The APRS radio has been demoted back to RX only until we can get a second antenna up on the tower. We added a band pass cavity in line with each of the radios, tuned for the best VSWR we could tune up, which seemed to make a world of difference.

Rob took some screen shots using his awesome new spectrum analyzer, so I'll let him report back with all of the details.

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Rob Eckel

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Nov 30, 2014, 1:11:13 AM11/30/14
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On Sat, Nov 29, 2014 at 10:39 PM, Luke Jenkins <luke...@gmail.com> wrote:
Tonight N7RPG and I did the final tune of the repeater cavities and got the 145.250 repeater back up on the air. We're using a 100w Motorola Spectra radio on TX, and another lighter duty spectra on receive. The APRS radio has been demoted back to RX only until we can get a second antenna up on the tower. We added a band pass cavity in line with each of the radios, tuned for the best VSWR we could tune up, which seemed to make a world of difference.

Rob took some screen shots using his awesome new spectrum analyzer, so I'll let him report back with all of the details.

--
from_144.39_to_144.65.bmp
from_144.39_to_tx.bmp
from_144.65_to_tx.bmp
from_ant_to_144.39.bmp
from_ant_to_144.65.bmp
from_ant_to_145.25.bmp

Rob Eckel

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Nov 30, 2014, 1:12:07 AM11/30/14
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On Sat, Nov 29, 2014 at 10:39 PM, Luke Jenkins <luke...@gmail.com> wrote:
Tonight N7RPG and I did the final tune of the repeater cavities and got the 145.250 repeater back up on the air. We're using a 100w Motorola Spectra radio on TX, and another lighter duty spectra on receive. The APRS radio has been demoted back to RX only until we can get a second antenna up on the tower. We added a band pass cavity in line with each of the radios, tuned for the best VSWR we could tune up, which seemed to make a world of difference.

Rob took some screen shots using his awesome new spectrum analyzer, so I'll let him report back with all of the details.

--
monitor_rx_local.bmp
monitor_rx_local_vs_remote.bmp
VSWR_antenna_only.bmp
VSWR_antenna_only_2m_zoom.bmp
VSWR_from_144.39_to_ant.bmp
VSWR_from_144.65_to_ant.bmp
VSWR_from_tx_to_ant.bmp

Rob Eckel

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Nov 30, 2014, 1:41:22 AM11/30/14
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Wanted to highlight this image, since it was one of the last measurements taken and gives a good picture of the overall cavity performance.


​
Yellow:   Antenna to 144.65 RX (Voice)
Magenta:  Antenna to 144.39 RX (APRS)
Blue:     Antenna to 145.25 TX (Voice)

The TX is attenuated about 10dB to the antenna, which cuts the 100W down to roughly 10W.  We measured 15W with my power meter, FWIW.
Then, looking at the two RX plots, there's about 90dB of attenuation on the TX frequency from the antenna to each RX port.  Add the 10dB from the TX port to antenna, and we have ~100dB of separation on the TX frequency.
The same can be done with the RX frequencies, which shows ~50dB of separation at those frequencies.
The two RX ports are currently around 4dB attenuation from the antenna, which should give it pretty good ears.

Some ASCII art for the cavity setup.  BP=Bandpass, N=Notch:

TX ---> 145.25BP ---> 144.65N ---> 144.39N ---> ANT

                                               /---> 144.65BP ---> RX Voice
ANT ---> 145.25N ---> 145.25N ---> 145.25N ---|
                                               \---> 144.39BP ---> RX APRS
                               

John Sohl

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Nov 30, 2014, 1:44:10 AM11/30/14
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Nice. What spectrum analyzer are you using? Is it the DSA815? 

John

- - - -
John E. Sohl, Ph.D.
Professor of Physics
Weber State University
1415 Edvalson St., Dept 2508
Ogden, UT 84408-2508

voice: (801) 626-7907, fax: (801) 626-7445

To view this discussion on the web visit https://groups.google.com/d/msgid/wsuarc/CAJ9CHdrRkULKZJTjCaraNSoGQ4SCJnO6SDZ_w3MY9%3DDj7FiBPg%40mail.gmail.com.

Rob Eckel

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Nov 30, 2014, 1:47:41 AM11/30/14
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DSA815-TG.  The tracking generator is a must-have.  Really nice analyzer for the money.  I also have a directional bridge from mini-circuits to make the VSWR measurements.

To view this discussion on the web visit https://groups.google.com/d/msgid/wsuarc/CANen_gUpL97Yp8c43GEkMeTcgkMy%3DvMEALb3iPLKK4-yrFCfBw%40mail.gmail.com.

Rob Eckel

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Nov 30, 2014, 3:27:30 AM11/30/14
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Pic of the repeater standing next to a ham.


IMG_0084.JPG
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