1-12-2013

Bill's (K9YDO) 900 Mhz Repeater
Information Corner

 

Since we are presently undergoing extensive changes in our 900 Mhz repeater systems here in Indianapolis, IN, this page is to help keep users informed as to the current ongoing changes and testing taking place at this time.  Bill & Mike (WA9FDO) have been taking lead on this project ... so below you will find Bill's postings as to their progress !

At the present time we have 4 sites that are available to us that are equipped with antennas that are being utilized to develop the complete 900 Mhz repeater system.  

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Start at the bottom of the page and read up if you want to see how we got here !!

1-20-2012

On Friday afternoon,   the last major piece of the puzzle was put into place with the changing of the receiver input frequency of the 927.4875  repeater system.   After about three months of work to determine what input frequencies to use and then change to,  the job is now complete.   I think the majority of users wondered from the beginning,  how much of an improvement  could there possibly be.   Now, the difference is incredible with both systems now linked together and sharing the remote receivers,  the two repeater systems  appear to be working very well.   With the system linked the way it is,  It could be considered as a poor man’s voting system.   

I want to thank Mike,  WA9FDO  for all of his help and support with this ongoing project.   We will need to follow up with final adjustments to all the audio levels within the linking system.

If you have any questions please let me know.

73,
Bill,  K9YDO
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1-17-2012

Below you will find a map showing the locations of remote receivers and repeaters and how the system is linked together via the 443.900 repeater. 

 

 

 

Any questions,   let me know ............

 

73,

Bill
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1-5-2012

The 900 remote receiver is up and working at the Boone County site.   The 902.0625  with 179.9 pl   and the 902.0375 on 179.9 pl are both working well.

The crystal for the 927.4875 primary receiver input frequency has been ordered and should be here by late next week.   To use the Harding Street repeater, either Noblesville or Boone County will get you into that system at this time.

73,
Bill
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1-4-2012

Weds.  was a good day.  Mike WA9FDO and myself were able to finish the installation of the former Kokomo system,  927.4875 at the South Harding Street site.    The primary receiver input of that system has not been  changed as of this time.  We are waiting on the replacement crystal for the crystal element to change the receiver from 902.4875  to 902.0375.  The pl tone on that system is 131.8 pl.   

Both  systems  are now linked together with the Noblesville receiver site on the 902.0375 and 902.0625  input frequencies,   using 100.0 pl tone.   On Thursday afternoon the Boone County site will become available with the remote receiver for both systems available using the 179.9 pl tone on both system input frequencies.

Bill
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12-23-2011

Today, Thursday the 22nd,   I was able to get to the other two tower sites to remove the other  scanned channels in the scan list to match what we have at the South Harding Street site.   All receivers are presently scanning 902.0375 and 902.0625.   After conducting the input frequency test,  we have decided on the two inputs listed.

The PL tone issue has been solved,   the 131.8 tone can now be used for the main receiver on the  927.4875 system when it is put back on the air.   

As discussed previously,  the remote receiver at the south site presently is running 179.9 pl tone on both scanned frequencies.    It will probably be relocated to the Boone County site in the next several weeks.   

Any question please let me know.

73,
Bill
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12-19-2011

Today,  Monday the 19th,   Mike, WA9FDO and I went to the South Harding Street tower site to check on  and determine if the remote receiver was off frequency and the 131.8 pl tone,   false decode issue.

Well,   the receiver did not appear to be off freq when checking it with a service monitor today.   The pl tone false decode issue does not appear to be at the Harding Street site.

It will take a trip to the Main site to verify,  of the two remaining sites,  which one is causing the decode issue.    While we were at the Harding Street site,  we took all but two of the programmed receiver frequencies out of the scan list.  We have narrowed the five frequencies  down to two freq’s now.   They are 902.0375  and 902.0625 for the south site.  Both freq’s at the Harding site are presently set for decode on 179.9 tone.     The two freq’s  seem to be hearing very well and there is no indication of Part 15 interference.     I will get back to the Main site this week to check on the pl tone decode issue and set the main receiver for the same two frequencies as the south site is set up for.  

It will probably be another couple of weeks  before the 927.4875 is back on the air.    

That is all the info as of this time.

73,
Bill

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12-15-2011

On Weds, the 14th,  Mike, WA9FDO and myself made changes at both the Noblesville and South Harding Street tower sites.   At Noblesville,  we loaded the 927.4875 repeater rack cabinet into my vehicle and it was hauled to the Harding Street tower site where it is not connected at this time.   The remote receiver was connected at the Noblesville site with the five test frequencies using 100.0 pl tone.    The test frequencies are 902.0250, 902.0375,  902.0500, 902.0625  and 902.0750  .         At the Harding Street site  the 927.4875 system is not connected at this time as we spent time trying to resolve an issue with the remote receiver pl decode,   the remote receiver that will eventually be taken to the Boone County tower site is still connected at Harding Street.   The receiver was intended to be programmed with the five test frequencies as listed above using 131.8 pl tone.  There seems to be some issue yet to be determined,  the 131.8 tone seemed to allow two sites to be keyed up at the same time.  To sort out what is going on,   we changed the tone at Harding Street to 179.8 pl tone at this time and may change it back to the 131.8 at a later time.    Checking the Harding Street receiver on Weds night,  all of the programmed test frequencies are 3-4 Khz low in center frequency.  The reference oscillator needs to be adjusted on frequency and should resolve the issue.    In the next several weeks,  we will be getting the 927.4875 repeater system connected with the remote base transceiver and it will then be connected at the Harding Street site in place of the remote receiver there now.    We will keep everyone advised as we get the systems in service. 

73,
Bill
K9YDO

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12-10-2011

 

For those of you that are fairly new to the 900 Mhz amateur band and those that have struggled with us for the past ten years,   you should read some history about the band concepts.  This is a great tutorial and resource for getting up to speed.    http://www.qsl.net/kb9mwr/ projects/900mhz/plan.html     I suggest you print the info for future reference.    With the new Alinco DJ-G29T handheld available in January,   there will probably be more interest.   It has been delayed because of the Tsunami in Thai.

 

Handheld coverage is great now,   when the leaves are back on the trees we will see how it effects the coverage we are now experiencing.   Since W9ICE  is  “the only game in town”  on 900 Mhz at this time,  it will be interesting to see what the expansion of users there may be.   If the new Alinco sells as expected,  my guess is that other manufacturers will follow suit.  

 

73,

Bill

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12-9-2011

 

I did a check this evening on the receiver input frequency and it appears the receiver center is high in freq by 2-3  Khz.   The transmitter was showing on my service monitor of 850 Hz high.  

 

The receiver seems to track both high and low of  6 to 8 Khz like it has  AFC.  I could step the generator up that far either side of the apparent center freq.  and hold the repeater up.

 

The receiver has tremendous sensitivity,  I can use just the service monitor with the output of  -20 db to bring up the system and with a -13 db output from the generator,   the quieting sounds about 12 db.   

 

What a system!!!!!

 

73,

Bill

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12-8-2011

Here are the photos taken yesterday,  of the spectrum analyzer display at the Walnut Road tower site antenna.  You can see why we have had such a struggle to avoid all of the Part 15 junk.  We have now found the place for the input frequencies to reside.     Last night I did a short coverage check north of Noblesville along Hwy 37 in a low area north of the Duke Energy generator plant.  Just great !!!!  Take a look at each of the photos taken,    using Mike’s, WA9FDO’s storage display  analyzer,  it tells the story.  A picture is worth a thousand words.       As Greg,  KJ6KO says,   “welcome to the bottom feeders” .  

73,
Bill

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12-7-2011

 

Today was an eventful day for resolving the problems we have been fighting for many years.   Mike, WA9FDO and myself went to the main repeater site for the 927.9875 system today.   We did some looking once again with the spectrum analyzer connected to the 900 antenna.   The spectrum was verified,   that it is fairly clear down below 902.100 Mhz.   We then proceeded to change the receiver input frequency of the main repeater receiver.   We have temporarily programmed five input frequencies into the receiver,   902.0125,  902.0250, 902.0375, 902.0500, 902.0625.   It required retuning the duplexer and cavity filters.    The system is running 75 watts to the feedline.   

 

The first freq.,  902.0125 has some unknown source carrier above the frequency a few Khz that can produce a heterodyne if the input signal is not strong enough to saturate the receiver.    At this time, the 902.0375 is not in the scan list to be used at the main receiver because of it having the same 77.0 pl tone as the remote receiver on South Harding Street at this time.   When we get back to the Harding Street remote receive site next week,  we will reprogram that receiver with all of the same inputs using 131.8 pl tone.  That remote receiver will eventually be relocated back to the Boone County tower site.    The third remote receiver will have all the same input frequencies as the main receiver,    except it will be using the 100.0  pl tone.    It will be connected at Noblesville tower site next week.

 

 

There is no comparison with the quality of the repeater being able to receive now,    from previous input frequencies.   What a difference!!!    After we see how each input frequency performs with the five test frequencies being scanned now,  we can then set the main receiver on a specific permanent  frequency.     The main repeater receiver has tremendous sensitivity,  something like  .1 uv  to open the squelch on all of the scanned frequencies.   

 

The former Kokomo repeater system ( 927.4875 )  will be getting it’s input frequency changed as well,  it requires a replacement crystal channel element,   since it is not programmable,  the frequency is a bit more problematic.    We have not decided as to what input frequency it will be on at this time.   After the testing with the 927.9875 with the five input frequencies,  we will pick a frequency for the 927.4875 system.   Output frequencies may need to  be changed later because of programming issues with some Motorola radios not allowing odd split inputs.     I hope I have clarified some of the changes that are being made and why they are necessary.    If you have any questions please let me know.  

 

We hope to get all of the changes finalized very soon.  

 

73,

 

Bill

K9YDO

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12-1-2011

 

I have good news,  the test completed today proved very worth while.   Mike,  WA9FDO and myself  checked five input frequencies at the south Harding Ave. tower site on Weds afternoon,  with amazing results.  That site,   just like our main repeater site experiences the same type interference from various Part 15 interference.  Dick, KC9AY programmed 902.0250,  902.0375,  902.0500, 902.0625, and 902.0750  into his TK981 to provide a real test signal for us.   He was just about full quieting without any Part 15 noise on all of the frequencies received on my ICOM 91 AD handheld with a filter and GasFet preamp between the feedline and handheld.     We then reprogrammed the remote  MaxTrac receiver to the 902.0375 frequency.   The MaxTrac receiver has both the 902.9875 using  131.8 tone decode  and the 902.0375 using 77.0 tone decode,   scanning for either frequency to link back to the system.   The difference between the two frequencies is like night and day difference.   We will run this arrangement for a while,   as the second remote receiver setup is put together for the Noblesville or Boone County site.    This is going to take some time to get to the final plan configured,  but it will be just wonderful not having to deal with all the noise we have been fighting for ever,    since the system was put together about ten years ago.     I now can get into the Harding Ave site,   from my mobile here at my house,    better than the main receiver site that is closer to my location.    If you can get the test input frequency programmed into a radio for participating with the testing,  I suggest you do so.  

 

All of those that dislike having to get their equipment reprogrammed will realize what a great improvement in the end.    It’s too bad we did not pursue these changes a long time ago.    If you have comments, please let me know. 

 

I want to thank,  Mike, WA9FDO, and Dick,  KC9AY  for helping with this project.   Dale, WB9YCZ  and Frank, WB9OPR  have provided information needed for programming the MaxTrac  receiver,   and Greg,  KJ6KO in California for some good information on looking at the bottom of the 900 spectrum for a clear input frequency.      The ARRL band plan adopted in 1989 is no longer usable in most areas of the country because of Part 15 stuff ( junk ).  

 

73,

 

Bill

K9YDO

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11-17-2011

 

Today,  Mike, WA9FDO and myself relocated the 927.9875 system back to the Walnut Road tower site from the Boone County site after completing the test at that  site..     It was a very interesting and successful day.  We spent considerable time and performed a lot of testing and learned a lot about the Part 15 interference we have had to deal with for over the past ten years now.   Our testing today confirmed what I had been told about the Part 15 equipment use,  the bottom 200 Khz of the 900 band does not have much in the way of Part 15 interference.  It is kind of a guard band of Part 15 equipment.    I had exchanged emails with Greg, KJ6KO in California,  he stated they typically do not have the interference issues,    if they use inputs between 902.000 and 902.200.   Greg specifically suggested we look at 902.0125,  the first 12.5 Khz channel above the lower band edge.    We spent quite a long time looking with the analyzer down at the bottom 200 Khz today and conducted a test with Dick,  KC9AY.  Dick had programmed his Kenwood TK981 with the proposed new repeater pair,  902.0125 input  and the output frequency of 927.0125 using the 77.0 ctcss tone.  Dick made a test transmission on the new input frequency and we listened with my ICOM 91AD  using a cavity filter between the handheld  and the 900 antenna at the tower site,  it sounded like it was  on the 442.65 system, no noise and full quieting.    What a difference in quality of the received transmission.  Then we made a test transmission back to him using the signal generator into a ten watt amplifier, he stated it was a solid signal on his Kenwood TK981 receiver.    That was the convincing reason why we need to change frequencies.    So,  over the next few weeks,  we will be getting ready to do the change.  There is not a fixed time table for completing the change at this time.   I will keep everyone advised as to when we can get it done.   After this system is changed,  then the other system presently on 927.4875 will also be changed to a new frequency.  It is not known at this time what frequency it will be going on.   It may be going on 902.0625 or 902.0750.   All of this we will run by the frequency coordinator.   

 

Temporarily,   we have retuned the duplexer, cavity filters on the 927.9875,  the system should be performing as well as possible at this time.   The 927.4875 is still temporarily at Noblesville with the intent of relocating it back to Boone County site  over the next week or so.

 

I know having to reprogram frequencies in the various types of equipment is an issue,  but after you hear the difference in the quality of the transmission you will be pleased.

 

If you have questions, please let me know.

 

73,

 

Bill

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11-17-2011

 

Here are photos that was done at Mike’s QTH,  it kind of looks like what we saw today at the 79th & Walnut Rd tower site.   Take a look at the first 100 Khz.   We are going to go back and collect some long storage spectrum photos form the Walnut Rd site.

 



 

 

Bill

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11-16-2011

 

The current  frequencies are going to be changing soon because of Part 15 interference.   We just completed extensive testing today at one of the tower sites.  The present frequencies are  927.9875 output with the main receiver 915.9875 input , using 77.0 ctcss tone.  We have a remote receiver on 902.9875,   it will decode either 77.0 or 131.8 tone.   The remote receiver is presently at South Harding Street near I-465.    The system we acquired from Kokomo is 927.4875 output with the input on 902.4875,    using the 131.8 tone.    But,  these frequencies will be changing over the next several weeks based on our results from testing today.   We have determined,  looking at the spectrum and information I recently received from a 900 system owner in California,   there is a Part 15 guard band at the bottom of the 900 amateur allocation that is clear of the Part 15 interference,    we have struggled with Part 15 interference over the past ten years of operation.      The first change will be the 927.9875 system,  it will probably be going to 927.0125 output with the input being 902.0125.  The tone will remain 77.0 ctcss.   The remote receiver will change to 902.0125 with a tone of 131.8.   We do not know at this time what frequency the 927.4875 will be changing to, it will may be 927.0625 output with the input of 902.0625 ,  we will probably keep the 131.8 ctcss tone.

 

73,

Bill,  K9YDO

 

 

 

Interesting 900 Mhz Websites

http://users.innercite.com/kj6ko/page8.html

https://dl.dropbox.com/u/97484437/927 MHz FM July 2012.pdf

 

 

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