6 Meter APRS Lives

June 21, 2018

Update:  Dale N0KQX has joined in from SW Kansas as of June 24th. N0KQX-6 has already been heard several times at K4KPN-4 in KY.  The K7BC-6 Virginia I-gate appears offline since the 21st. A few more I-gates on frequency would be nice. I believe I can enable gating on K4KPN-4’s 6m port (ah the flexibility of BPQ32) without impacting general packet operations on that port. I plan to test that option on my next trip back thru 4-land.

It’s not every day you hear and “digi” off the 50 MHz APRS digipeater at the Pentagon.

K4AF-6_20180619_6m_APRS_map_pent

Map showing location of the K4AF-6 six meter digipeater at the Pentagon. I believe this is part of the MARS radio station located there. Frequency is 50.620 MHz using 1200 baud AFSK packet.

 

June 19th 2018 a nice strong opening into NE Virginia revealed that the 50.6200 MHz 1200 baud 6 meter APRS and long time 6m packet “calling” frequency still has some action on it.

K4AF-6_20180619_6m_APRS_KYRDG_Terminal

The monitor for the 6m (50.620 1.2k) and 10m packet/robust packet ports at the K4KPN-4 N. Kentucky node. K4AF-6 is at the Pentagon. K7BC-6 is a few miles to the SW. Both are just over 400 miles away. Opening was very brief. June 20th would produce a stronger opening. Times are UTC.

 

On June 20th things would liven up even more with the Conway AR node “CON50” W5AUU-6 (likely bleed-over from 50.615 MHz) coming in. There was also an extended and strong e-skip opening to Wash DC with APRS packets bouncing around and being digipeated like it was 2m APRS at times. Several K4KPN-4’s beacons were getting digipeated and I-gated into APRS-IS via K7BC-6 in Springfield VA.

 

6m_aprs_raw_pkts_20180620

The June 20th 6 meter APRS opening into the Wash DC area lasted for over an hour. K4AF-6 was even audible at times on a HT (Yaesu VX-8DR) setting on my desk. Gotta love the Magic Band of 50 MHz!

Distances involved where about 410 miles from Kentucky to DC. So I wouldn’t call it really short skip, but definitely shorter than normal. General rule of thumb is when 6 meter e-skip shortens up to 250-300 miles then it’s time to start checking 144 MHz for possible e-skip on that band.

Good to see there is still some life on 6m APRS. Band openings can make things interesting, even on VHF packet. Also nice to see there is some packet radio gear at the Pentagon MARS / AR station(s).

K4KPN-4’s 10m port beacons every 10 minutes and the 6m port beacons every 5 minutes with APRS compatible beacons to help detect band openings. The 50.620 MHz 1200 baud port on K4KPN-4 also supports WIDE1-1 digipeating in addition to normal packet radio connects.

 

WA4ZKO

 


K4KPN-10 Robust Packet I-Gate / Digipeater Update and APRS-IS Gotchas

May 26, 2018

K4KPN-10 has clearly benefited from the combination of antenna system repairs and noise floor (NF) reduction work at the site last Fall. Performance is back to what one would expect from it.

For those that ask why Robust Packet? One word….performance. Below is a screencap of what the 30m RP APRS world looks like from the Kentucky gate’s perspective over a few days.

RPR_K4KPN-10_20180519

K4KPN-10’s view of the 30m Robust Packet APRS world. Why RP? One word….Performance.

Around 25 to 30 of those stations on there have been heard direct on RF at some point. Single hop stateside coverage is easy. Europe is in to some degree nearly every evening and EU mobiles are often heard. Even the challenging polar path over to RT9K-15 is in there at times.

I’m hesitant to use APRS-IS for serious coverage analysis since it doesn’t begin to reflect everything heard on RF, especially on HF. Regardless K4KPN-10’s “heard” and “heard by” data is interesting:

RPR_K4KPN-10_heard_201805

APRS-IS perspective on RP HF APRS stations heard by K4KPN-10 so far this month.

RPR_K4KPN-10_heard_by_201805

APRS-IS perspective on RP HF APRS stations that have heard K4KPN-10 direct so far this month.

Yes some of the soundcard modems will do good work on 300 baud AFSK for single hop HF APRS and some occasional DX can get through. Some can do even better with bit fixing. The problem with bit fixing (guessing) is it breaks spec and can easily cause corruption if done too aggressively even on APRS. Thus why we so often trace corruption on the VHF APRS feeds back to soundcard modem equipped gates. Even with bit fixing the limitations of 300 baud AFSK become apparent over long haul DX paths.

Where Robust Packet shines is it uses Pactor-III like modulation that allows error correction without breaking spec. RP offers good noise immunity and deals with the multi-path on long haul DX packets better than a typical AFSK modem can.  Since RP uses space and power efficient dedicated hardware it is also well suited to stand-alone portable/mobile tracker uses without the need for a PC/laptop.

Robust packet is a mode and hardware built from the ground up for improved performance on HF and well suited to HF APRS. DX reception is not occasional, it is commonplace. I admit to sort of taking 4,000+ mile APRS DX as NBD till one of the HF AFSK guys sent me a “holy $#@$ what are you using that hears across the pond nightly” email LOL.

For those asking “where is K4KPN-10 hearing RT9K-15? Oh it is in there on RF, but due to his gate configuration it’s going to be difficult for stations other than a few lucky EU gates to ever get credit (APRS-IS perspective) for hearing him.

RT9K-15_at_K4KPN-10

RT9K-15 being heard direct at K4KPN-10.

Well here is an opportunity for a good lesson on the flaws of assuming APRS-IS gives a complete picture of what is going on at the RF level.

It is important to realize that APRS-IS does dupe checking. If I-Gate A and I-Gate B hear the same packet only one of them can get credit for it from the APRS-IS perspective. Which one gets credit? The first one that gets that packet to APRS-IS. The one with the lowest latency to the APRS-IS system.

If you run an I-Gate or home APRS system on both IP and RF you can easily screw yourself with bad timing values. The RT9K-15 I-gate is doing something that will make it very hard for coverage analysis via APRS-IS. It appears to be aggressively beaconing to APRS-IS every few minutes? I’m told that it is heard often in EU, but rarely does an EU gate get credit for it in the eyes of APRS-IS. This tells me it is probably making the 2nd mistake of beaconing to APRS-IS and RF at the same time. This means even if another gate hears his packet on RF then it’s unlikely outside of internet congestion on his link that another gate can decode that packet off RF and inject it into APRS-IS before his internet beacon gets into APRS-IS.

Another problem this creates for APRS-IS analysis is it throws the packet counts off on the above pages. A good example is it shows a monthly total of 5 packets for DF1CHB /AM.  He was in direct on the eastern USA I-gates for hours earlier this morning, but also hitting EU gates so NOAM will only get occasional credit for gating him even after dozens of packets gated in. Tonight he is airborne over Serbia and K4KPN-10 is hearing him direct like clockwork on 30 meters:

DF1CHB_30m_rpr_aprs_20180526

DF1CHB /AM over Serbia and coming in on 30m robust packet almost as if he’s a local on VHF LOL.

Don’t get me wrong, this is not a complaint towards APRS-IS. It’s just how the system works and how it has to work. It’s just important for APRS operators to understand that APRS-IS doesn’t give you the full RF picture due to the necessary dupe checking going on. This is especially true on HF where the same packet can easily be heard by multiple I-Gates hundreds or thousands of miles apart.

Also noteworthy that some stations run beacons marked “RFONLY” or “NOGATE” paths. A properly configured I-Gate will not gate those beacons into APRS-IS. This is another gotcha if you’re trying to get a full picture of RF level activity via APRS-IS based systems and apps.

Recommendations based upon lessons learned here if you are interested in getting decent coverage analysis via APRS-IS?

  1. There is normally no need for an APRS station to position beacon on their internet port (APRS-IS) more than once or twice an hour unless it is moving. Serves no useful purpose for fixed stations and it only adds to the cumulative load on the APRS-IS system.
  2.  I-gates should consider beaconing on their internet port at a rate of just under 60 minutes.
  3.  Avoid beaconing via RF and internet ports at the same time.
  4.  If you are not moving, then you don’t need to be pounding the heck out of the RF side either. 2-3 RF beacons an hour from a fixed station is more than enough to keep you on most maps and fresh in APRS-IS for messaging/gating purposes if you are in range of an I-Gate.

WA4ZKO


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

May 8, 2018

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


Stay Tuned

April 22, 2018

Well after two weekends worth of discussion and debate, some Kentucky Packet Systems will be returning to the airwaves soon. Not everything is returning and a lot of what is returning will only remain if it sees enough usage to justify it. This week’s projects have been tower climbs to re-feed the VHF/UHF antennas on my personal tower and tweaking the microwave links between the sites that will be used.

Our utility company recently replaced a pole next to the Williamstown building where I still maintain a minimal office/storage site. When they scheduled that I pressured for new hardware (vs just swapping it to a new pole) and better grounding. This has helped some with the nasty 6m/2m noise floor at that location. As such I’m going to see if it will be useful to have a low profile APRS I-gate there. With the loss of the KB9GYO digi last Fall, Edgewood’s limited coverage down this way, and the reduction in coverage from the Lexington digi, the area’s local 2m digi coverage is very poor now. I’m not certain how much a low profile I-gate/Wide1-1 digi in Williamstown will help, but we shall see what T&E reveals this week.

Do note that this I-Gate site will not be permanent, it will eventually be turned off.  I’m leasing that site and seriously doubt I’ll still have any need for it in a few years. The proper fix for the APRS network is a much better I-gate location and a local medium profile digipeater. Sorry but I can’t provide either and others are going to have to step up and provide better 2m APRS infrastructure. Sorry, it is what it is.

Yes the local APRS scene is in near shambles. My inbox since last summer makes it clear that I’m not the only one that has noticed. My initial monitoring of the 2m APRS network from a medium profile location quickly revealed many problems.  A lot of stuff with poor signals, misconfigured software, and of course the usual congestion from abuse/silliness on the channel from adjacent areas. My my what a mess the 144.3900 APRS frequency is anymore. I can’t imagine why I prefer the HF APRS network over the 2m APRS network for my needs LOL.

Some have asked about K4KPN-10’s future? Well I just signed a 3 year contract on two very nice fiber runs into that site and invested in a new HF radio for it last Fall. Safe to say KYPN remains committed to keeping that on the air. Plans to eventually move it to Wyoming? No plans to move it out there since it is not wise to place another HF gate there that close to Bill’s excellent gate in Montana. With VE7OI’s new gate coming online and the excellent observed performance of K4KPN-10 out that way by myself and Randy (K7LNR) it seems clear that the N. American 30m RP APRS network is best served by K4KPN-10’s current location.

With the solid internet (both fiber and dialup) at that site now, it’s proving relatively easy to properly monitor, control. and keep secure from afar which has been one of my top control op concerns. When you run stuff under the automated & remote control rules you have an obligation to monitor and keep control over anything putting RF into the air. Obviously there are no guarantees – it’s a hobby, we provide it for free – but currently KYPN has no plans to change K4KPN-10 for the foreseeable future.

Not sure how much of the local packet gear will be back online before we head back west in a few weeks. Dad’s health and my day job project list will have at least myself coming back to 4-land fairly often this summer. Plenty of opportunities to finish whatever is not completed this time around.

Last but not least, no I’m not back to stay. We will be very “bi-coastal” for a few more years for work/play and helping care for an elderly parent. That said our retirement is coming sooner or later. I like southern Idaho just as much (same quality of life and a heck of a lot cheaper) but the XYL fell in love with NW Wyoming. She recently switched the car registration, moved her business, and made herself an official Wyomingite. You can guess how our WY vs ID homestead planning conversations go….Wyoming it is LOL.

I will do another post soon detailing what is coming back permanently, some background, what is coming back conditionally, and what will be turned off in a few years.

Stay tuned!

Jeff
WA4ZKO


K4KPN-10 Antenna Upgrades Completed

October 8, 2017

After a few tower climbs to repair some lightning damage to the feedpoint the K4KPN-10 30m Robust Packet I-Gate/Digipeater is back on its primary antenna.

Thanks to a client that gave me some old LDF after we did a tower upgrade, the 9913F coax has been replaced with LDF that is much better suited to that environment. I also replaced the radio whose PA had failed so the gate is back in full TX/RX mode with much improved transmit and receive performance.  Seems to be getting out as expected and some HF noise floor reduction work at the site has yielded some serious receive SNR performance improvements.

Jeff
WA4ZKO


K4KPN-10 I-Gate Now Receive Only

June 21, 2017

As of June 20, 2017 the KYPN sponsored K4KPN-10 30 meter Robust Packet APRS I-Gate is now a RX only I-Gate.

During recent maintenance at the site, the PA in the Yaesu FT-100D radio there was found to have failed. This is the 2nd Yaesu FT-100 of mine that has suffered PA failure and I gather this is very common failure for that radio. You would think it was a post-2001 era ICOM radio LOL. In fairness this radio was purchased used and with unknown TX hours/treatment in the past. I did do the fan modification to it and it was in a cool climate controlled environment, but again I have no idea of how it was treated in the past.

I obtained this radio cheap off the used market due to a damaged display so I’m not shedding any tears over it. Since it is remote operated via CAT control the display was a non-issue. It was well suited to a “tower site” 24x7x365 radio versus putting a more expensive HF radio at a tower site that takes a few lightning hits each year.

Even if replacement parts can be found I don’t plan to fix it for several reasons. We can’t run much more than single digit power at that site and it has always suffered from “big ears, tiny mouth” syndrome (RX range far exceeded its TX range).  I’m gone from the area most of the time and a friend has been helping me keep an eye on it since transmitters operating under the “automatic” rules need to be closely monitored. There has been some past concerns with digi/beacon rate abuse on the 30m channel from 2-land and we had recently discussed just running it as a receive only I-gate. Guess you could say this event has sealed the deal on that particular discussion.

I’m not a huge fan of RX only I-Gates, but given the increasingly sparse 24×7 gate coverage here in North America the pros outweigh the cons. Maybe some dedicated soul will put up a 24×7 30m RP I-Gate in the southeast sometime. If that happens I’ll probably pull the plug on this gate or run it on another band for tinkering. We have had it on 80/40/17/6m briefly a few times for tests, but I feel the HF RP APRS network is best served by NOT “fragmenting” all over the HF bands.

 

73
Jeff
WA4ZKO