Catching Up

We’re WAYYYYYYY overdue for an update!  It has been a very busy summer; I’ve been doing my best to enjoy it, and that has meant less time for writing blog posts.  Maybe it also means less time for READING them!  At any rate, I’ll get back to the duplexer story in the next post.  But for today, let’s take a moment and review where we stand:

REPEATER USE

I’m very happy that so many have used the repeater, and have been experimenting with antennas and rigs.  We have maybe a dozen regular users, another dozen who show up every once in a while, and an unknown number that listen regularly but don’t transmit.  There is always room for more, please join in!  Everyone is welcome.  The repeater doesn’t “belong” to any one group or person; it is there for all hams to use and enjoy. 

NETS

I have often been asked whether we will host a net on this repeater.  I’m open to the idea, but I don’t have any plans to start a new net.  Rather, I would like to simulcast (link) to an existing net, such as the Wednesday night 7:30pm LARC net on 146.91.  The repeater’s hardware doesn’t provide a way to do this, but an upgrade is planned soon.  When we’re ready to turn on a link to that net (or others), readers of this blog will be the first to know!

RANGE

We’re getting a feel for the repeater’s range.  By all accounts, the transmit range of the repeater is VERY good, even when receiving cross-polarity.  Adirondacks.  Catskills.  Watertown.  Binghamton.  Rochester.  Ontario, Canada.  Northern Pennsylvania.  Western NY hills.  Vermont.  Some of the signal reports from these areas run anywhere from S1 to S9+.  However, one common thread is that some people (especially more distant stations) can hear it, but not bring it up.  We would wish that anyone who can hear it could work it, so it puts our minds to thinking: Why can’t they?

I can think of a few reasons why this might happen:

  • Not enough power.  If you’re on the fringe of the repeater’s reach, generally speaking you would need about as much power as the repeater (approximately 100 watts).
  • Poor antenna performance.  Situations can arise where an antenna performs better on receive than it does on transmit.
  • CTCSS tone.  Some hams have had difficulty getting their radio programmed properly for transmitting the PL tone, so we have to consider that as one possibility.  Also, one ham says the repeater’s receiver is too sensitive to tone level on the received signal, and that he had to increase his rig’s tone deviation before he could open the repeater’s squelch.  So far, he is the only one to contact me with this report.
  • 4 – Polarity.  This point gets a LOT of discussion.  Yes, this is a horizontally polarized repeater, and using vertical antennas will reduce your range.  But, a polarity mismatch theoretically reduces your range in BOTH directions equally.  When it comes to hearing the repeater but not being able to work it, I don’t think this is a significant factor.
  • Repeater sensitivity.  This may be the biggest reason.  And I’m not talking about simple bench sensitiviy.  It is a sad fact of two-way radio life that repeater sites are usually very noisy.  This would be a great topic for a future, in-depth post, because it is one of the biggest factors affecting repeater performance.  In short, the collection of broadcast stations typically found at prime hilltop locations produce some amount of wideband noise in addition to their intended signal.  It is kind of like the hiss you hear if you put your ear right up to a speaker on your home theater system.  Such noise from high power transmitters is very low in comparison to their main output signal, but it can, and does impact the ability of a repeater receiver to hear weak signals.  At our location, I’ve measured this RF hash at about 15 dBm above the background noise of the test instrument, or -110 dBm, which is around .7 uV.  Chances are that your receiver isn’t seeing anywhere near that amount of noise, so you have a much better effective sensitivity than the repeater.  In addition to site noise, tests have confirmed that we’re getting an additional 6 dBm of desense from intermod involving the transmitter.  If all of these numbers (and my math) are correct, that’s around 20 dBm (in round figures) of desense.  20 dBm is the difference between 100 watts and 1 watt.  Look at it this way: If you can now work the repeater with 100 watts from a distant location, you could do it with just 1 watt if we could magically remove all the desense.  Think of what THAT could do for the repeater’s range!

Combine some mix of all of these things, and you can easily see why we are getting some reports of an alligator repeater (all mouth and no ears).  The GOOD news is, some of these things can be fixed.  That’s a topic for future posts.

DX

July 17 brought us a fabulous gift in the form of a strong sporadic E skip opening on 6 meters.  I heard reports of great DX on SSB and FM simplex.  If you turned off your rig’s tone encode (to avoid bringing up K2INH 53.05 in Auburn) and kerchunked 53.05, you could hear at least three repeaters coming back!

I worked Kentucky on a repeater on 53.11 (not sure where the repeater actually was).  And, several locals had a rather lengthy QSO on 53.67 with a ham from Daytona Beach, Florida!  It was very exciting to see what 6 meters can do, and why they call it the “Magic Band!”

Aside from that great day, we’ve heard various other reports during this repeater’s first four months.  A ham from Windsor, Ontario (near Detroit) has reported hearing us on several occasions.  One local reported hearing a brief signal on the repeater from Hudson Bay, Canada.  We all look forward to the next big opening! 

UPGRADES

GE Mastr II Low Band RadioThanks to a generous local ham, I have another complete GE Mastr II repeater!  At first I thought it would just go in to storage and be used for parts, but before long I decided to completely refurbish it to become the “new” KD2SL repeater.  We’ll give it a spiffy new controller that will allow for linking and/or a remote base.  The receiver and transmitter will be thoroughly rehabbed to squeeze out every last ounce of performance. 

The rush to get the original repeater on the air back in May did not allow the luxury of time to make these performance modifications, so I’m enjoying the opportunity to do them now, and learn more about the Mastr II in the process.  A low band Mastr II typically is designed to cover approximately 6 MHz of spectrum.  If you want to operate below or above the original design range, it might work, or it might not.  Many of the tuning adjustments in the receiver and exciter can’t tune far enough (i.e., the ferrite slugs won’t go far enough without falling out of the coil) for proper setup in the 6m band unless certain components (capacitors, mostly) are changed.  Again, I’ll have more about this in a future post.

Another important upgrade is the new repeater controller I alluded to earlier.  This will open up various linking opportunities, easier control of various features, and provide more options for identifications and announcements.

Is EchoLink or AllStar in the repeater’s future?  Maybe.

FUTURE EXPERIMENTS

I have obtained a couple of commercial low band antennas – a dipole, and a ground plane.  I intend to install one or both of them at the repeater site, and conduct some experiments to compare their performance to the TV broadcast antenna.  How much difference does antenna polarity make?  How high above ground does a 6m antenna need to be?  Will a different antenna, or split TX-RX antennas provide better repeater performance?  Less crackle?  We’ll experiment and find out!

CONCLUSION

Thanks again to all who have been taken time to use the repeater!  More posts are coming, with information about future upgrade plans, as well as the conclusion of the story of how the current repeater was built.  Until next time, 73 and I hope to hear you on the repeater!

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About kd2sl

I'm a lifelong geek, interested in anything electronic, but especially ham radio, radio and TV broadcasting, and computers. Employed as Chief Engineer for WSTM-TV 3 (NBC), WSTQ-LP 14 (CW), and WTVH-TV 5 (CBS) in Syracuse, NY.
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One Response to Catching Up

  1. Soemann, Clint says:

    Hi Kevin,
    One thing to consider on the repeater as far as sensitivity is the CTCSS level required to trigger the repeater. Depending on the decoder you are using there are some modifications that can be made to make the decoder more sensitive and require less level to access the decoder. When you’re ready to address this give me a call and I can go over the mod’s.
    Clint N2FMM

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