K4KPN-6 6 Meter APRS Digi / I-Gate Full Availability

August 10, 2018

Observing a need for a 6 meter APRS I-Gate in this region, KYPN realized the K4KPN-4 BPQ32 node could probably meet this need without any additional hardware investment. Recent versions of the BPQ32 node software have considerable built-in APRS digi/gate capabilities that only need to be configured and enabled.

The past few months showed that the past trend of most activity on the node being on the UHF 9.6k, 220 1.2k, and 10m RP ports was still holding true today. Thus we pondered could the APRS features on the 6m port be enabled and would they coexist with the existing Node and its BBS, Chat, and RMS functions? If both could coexist then it was frankly a no-brainer to do it.  The 6m port puts out a stout signal that penetrates well into the valleys and hilly terrain common to the area.

The 6 meter APRS scene has seen bursts of activity over the years, but good 24x7x365 digi/gate infrastructure is very rare outside of a few pockets of activity. The rest has been more of  what I’d call seasonal activity of folks firing up on frequency to listen for packet/APRS DX during the late Spring and Summer e-skip seasons. Others use it as a less congested alternative to the mess that 2m APRS can be in some areas.

At one time there was a push to build up packet infrastructure on 50.620 across the country for the PropNet network. The WSPR mode and network came on the scene and its many advantages stagnated PropNET growth. What remains of PropNet seems mostly focused on PSK31 operations on HF. No PropNET packet operations have been noted on 50.620 for over a decade now. This means 50.6200 MHz is an underutilized frequency begging to be put to good uses.

Testing showed both APRS and conventional packet should coexist fine on the Jonesville BPQ32 node’s 6m port. Thus on the afternoon of July 9, 2018 KYPN spun up K4KPN-6 on 50.6200 MHz 1200 baud AFSK packet mode. K4KPN-6 offers both full WIDEn-n compliant digipeating and basic R-I-R (2-way) I-Gate messaging functions.

The current plans are to run K4KPN-6 24×7. The 6m port beacons an APRS compatible beacon every 5 minutes to help detect DX openings. Beaconing faster would provide a better chance of catching meteor burns, but 5 minutes was felt to be a good compromise value for a mixed use port.

The advanced APRS digipeater functions available in BPQ32 are downright slick and one can tell John gave them some thought. The I-Gate side has some cosmetic issues, but it is plenty usable from a functionality standpoint. I’ll try to run some changes/improvements past John (G8BPQ) this winter. He is busy sailing/traveling during the Summer months. Thus I avoid bugging him with non-critical feature requests and minor bug reports that can wait. John should be deemed a Saint for his patience with his user base and his willingness to continually improve BPQ32/LinBPQ.

So far K4KPN-6 looks like a valuable asset both locally and for the 6m APRS DX folks. Best of all with our existing 6m port on the Jonesville BPQ32 system there was no need to buy anything else. Just enable and configure the functions you want in the bpq32 config file and restart the node. Obviously you’ll need an APRS-IS login and password if you want to use the I-Gate functionality.

Node and application stack (BBS, Chat, RMS) remain available on the 6m port. The APRS functions are just another application running on the node.

 

6m APRS Path Recommendations?

Making use of the K4KPN-6 6m APRS digi/I-gate functions is no different than operating on 2m APRS. Paths of WIDE1-1 or WIDE1-1,WIDE2-1 are good choices for 1-hop and 2-hop paths.

 

6m APRS Beacon Rate Recommendations?

The 6 meter APRS frequency is not overloaded like the 2m APRS is in so many areas of the country. There is plenty of spare airtime on the channel. Thus the use of aggressive beacon rates is unlikely to be an issue. 5 or 10 minute rates for infrastructure sites should be fine in most areas.

Temporary use of even faster rates for testing or during meteor shower peak times should not be an issue and would increase the odds of snagging a burn. Mobiles can probably dial things down to 1 or 2 minute rates.

 

6m APRS Biggest Range Challenge? Noise Floor

The 50 MHz band propagates locally just like the 30-50 MHz VHF-Low band that you may be familiar with. Not so great in a pure urban environment. So so in a suburban environment, but ultimately best suited to rural environments where its range and terrain penetration qualities can shine.

Note:  There’s a reason why a surprising number of users remain active in the VHF-Low Band spectrum even though it doesn’t get much press. Current marketing/sales efforts are geared towards selling more expensive and complex systems on the higher bands. The range and simplicity of VHF-Low systems are still a good fit for some users.

Don’t laugh at Low band. VHF….  I know of a 46 MHz system installed in the early 1980’s that is still in use. Now that’s serious ROI. Also note that the VHF/UHF Part 90 narrowbanding mandate did NOT apply to VHF-Low systems.

Back on topic….

All things being equal 6 meters has more range potential than 2m. Problem is in the real world of RF all things are rarely equal. On 6m you are probably using a lower gain base antenna and most likely a less efficient mobile antenna system compared to say 2 meters. In most real world installs some of this will be offset by higher standard transmit powers, less free space losses, lower feedline losses, and better terrain penetration. All that aside, the main range limiter for 6m operators today is the higher local noise floor (NF) compared to the higher bands.

The old enemy of power line noise remains, but it is now joined by a wide variety of noise spewing consumer electronics clobbering both HF and the lower VHF spectrum. Sadly this is a problem that will only get worse unless the FCC cracks down on a lot of the cheap poorly designed/filtered junk behind so much of the problem. Even then it would take ages for device attrition to clean up the spectrum much. Plus we’ve become a society that expects everything to be super cheap versus paying for higher quality equipment.

Where you live and operate can make a huge difference and must be factored in unless you like surprises. I was stunned at the NF differences between the old KY QTH and our temp place here. Living out in farm country most of my life definitely spoiled me. I wouldn’t call this “urban” by any means, but having several neighbors nearby = a lot more noise on the bands. I was initially worried about the big power distribution lines a few hundred yards away out back. Turns out they are actually the least of the NF problems here LOL.

Every amateur radio band has it’s pros, cons, and unique propagation characteristics. Six meters is no exception to that rule. It remains a local workhorse of a band that also offers some fun DXing at times. It is called the Magic Band for a good reason.

WA4ZKO /7