K4KPN-15 I-Gate & WIDEn-n Digipeater now Operational

KYPN is happy to announce a new 2 meter APRS I-Gate & Digipeater callsign K4KPN-15 is now fully operational from EM78RP in Williamstown.

K4KPN-15 is a full 2-way I-Gate and WIDEn-n digipeater optimized for 1200 baud infrastructure use. System is transmitting pre-emphasized audio and the modem is fed flat receiver audio. This configuration helps provide improved compatibility and performance with the wide range of equipment and signal quality (wink, wink LOL) found on today’s VHF APRS network.

System is running 40w to 3db at 990′ AMSL. Performance testing with just a 5 watt tracker (Kenwood TH-D72) has shown good coverage to the west, north, and east. Coverage to the south is compromised due to both the rougher terrain south of Williamstown, terrain ridges, and some obstructions blocking a clear view to the S to SSW direction.

Low power tracker coverage around the Dry Ridge and Williamstown areas is nice although on 2m APRS I suggest 25w is going to stand a better chance against the congestion heard at your local digi’s receiver. Admittedly I had to find the “sweet spot” standing outside, but I managed to tag it from New Liberty KY (17 miles) with a TH-D72 HT on stock antenna which isn’t much of a VHF antenna to begin with.

Drive tests with the D72 on a quarter wave antenna has shown expected coverage. It hears better to the north than to the south and exhibits pretty much the same coverage of our central local public safety site when the remote receivers are not helping with the various coverage challenges our terrain creates. An interesting base-to-base coverage observation is it hears the WC8EMA gate/digi 60 miles away in Lebanon Ohio as good or better than the Edgewood digi at 24 miles.

I-75 coverage for a decent 25w tracker to an efficient antenna system should begin around the 168 mile marker southward till you get down around the 144mm. It is frequently hearing hilltop mobiles up to the 182mm. This has been verified with a 5 watt tracker to 1/4 wave roof mounted antenna. If you’re struggling to get in then either adjacent area QRM is really bad that day or you need a better antenna system.

Reference the above “better setup” note. One of the common observations of many voice/data infrastructure sysops over the last 20 years has been how often you will hear/see a ham mobile station running 25-40 watt mobiles yet have the talk out range of a HT. No joking, it’s increasingly common even on VHF where things tend to be more forgiving of poor installation practices. The graphic below is a textbook example. Here we have an unnamed 2m APRS mobile running a D710 passing through on I-75. He passes three different digipeaters and looks to only have maybe 1-2 miles of range. I’m thinking someone needs to examine his system as a 5w HT on the dash would do better than this LOL. Drastic example? Yes, but it is common to see mobiles with performance not explained by being on low power (bad idea on 2m APRS).

poor_aprs_range

Pro Tip:  Forget the fancy looking high gain multi-band VHF/UHF mobile antennas and stick to more simpler designs. Most of those overpriced things are lossy as all get out, look horrible on a vehicle, have long term durability issues, and “might” perform to 50% of their hype only if mounted in the most ideal location.  For 2 meters try a simple quality 1/4 wave antenna in a good location, fed with good coax/mount, and carefully installed connectors. You don’t need to spend big $$ to get good performance on VHF/UHF, you just have to do it right.

Okay back on topic……

Current plans are to put a higher gain antenna on it late this Fall, but for now this is working out well enough and let’s see if enough stations benefit from it. The noise floor at the location is still higher (S1-S3) than I’d prefer, but much better than the nasty S5-S7 powerline noise that used to plague the site. Some of this seems to come and go with dry/wet weather so I suspect we have another bad spot in the utility lines nearby. Being located in a commercial area with numerous offices (lots of switching PSUs, LCD monitors/TVs, cheap cell chargers, etc etc) nearby I doubt this site will ever hear as well as it could for its location.

The K4KPN-15 site has limited backup power and thus should not be counted upon for EMCOMM use. It is on a unique local city managed power grid that sometimes survives when adjacent areas are down, but generally suffers far more outages than adjacent area providers. The local joke is if a cow farts too hard in an adjacent county the power goes out in town LOL.

The Dayton Hamvention is coming up soon and that will give us a good look into K4KPN-15’s I-75 coverage. Gate/digi is not really intended to cover I-71 but I suspect it will help out some.

73
WA4ZKO

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