More than high-power, more than big antennas, more than tall towers – what I likes is some good VHF propagation… I’ve been hearing some distant repeaters during the morning drive this last week, and had hopes to catch me some decent signals during a good band opening. This weekend the propagation indicator map (you can see the current image below, on the right) had some good red paint over the south eastern US. I don’t know if the big HF contest event had folks distracted, or as Craig – K4XR suggested – a microwave conference in Texas; but there sure weren’t many folks on 144.200 this weekend…

I did catch one good contact Sunday evening tho; about 0150Z I worked Clayton – W4KVW in EM80, just west of Jacksonville, Florida. That distance is ~406 miles. I always like to point out that I’m only running 30 watts, with an omni-directional antenna in the attic. Shortly after that I heard Jimmy – W4ZRZ working Drew – KO4MA (also in Florida), but I couldn’t hear Drew… Maybe we’ll have some more good conditions like this before the winter cold settles in. These big cold fronts really spice up the bands.

Good VHF conditions for southeast US this weekend.

Good DX and 73 for now /;^)

In case you have not heard this rumbling on the horizon, you probably want to watch this for future development. Everyone that has connection to Amateur Radio is familiar with the FCC’s requirement that ham radio not be used for business purpose (specifically Part 97.113). Most of us recognize the obvious situations where that would be an issue, but recently a gray area has come to be in the spotlight. What if someone who is employed by a local Emergency Management Organization happens to also have a ham license, and is participating in a training exercise sponsored by that EMA… Unfortunately the FCC is taking the position that it would not be appropriate for that EMA employee to use the ham radio as part of that exercise. Another example given by the FCC points out the difference between a Red Cross employee transmitting health & welfare traffic on behalf of an individual that has been relocated to a shelter, and a Red Cross employee using ham radio to manage Red Cross resources (read as ‘Red Cross Business’).

Whether you agree with this interpretation or not – you need to know the background facts, and stay informed as to how this is playing out. Even while rule-making proposals are being worked, the fact remains that the FCC has stated their position on this, and we all need to be aware of how to stay out of trouble with the laws as they are currently interpreted. Especially if you are a paid employee of ANY emergency relief or response unit, and hold an amateur radio license – you NEED to read carefully on this subject and understand what all this means, and how it effects you. If you are a volunteer, you need to help ensure that others are not inadvertently mis-interpreted as being in violation.

For those who are only just now learning of this issue, here is a brief time-line (with links following): I first became aware of this issue in June 2009, while reading blog entries(1) by David Coursey – N5FDL, an Emergency Coordinator in California. He indicated that he had received a request for guidance from a volunteer, and that he had been in contact with the FCC. Based upon the FCC response, he further indicated that a Rule Making Proposal needed to be in the works. In August several of us collaborated in the construction of a White Paper(2), with background information and FCC responses. On Sept 1st, the ARRL issued their view of this situation in QST magazine’s “It Seems to Us”(3). On Sept 18, Alabama ARES members received this update(4) from the Section EC regarding the weekly regional HF net. N5FDL also posted his ‘Don’t panic’ updated guidance(5) on 97.113 compliance. Apparently groups around the country are considering their response to this issue as well.

There will be more on this touchy subject going forward, and you can follow along via http://n5fdl.com/97113-blog-and-forum/ . To be sure, there are other valid reference sites, and you are welcome to post comments here (or on N5FDL.com) with any additional relevant information.

Be sure to help spread the word among your fellow hams and emergency workers. This IS important…

Thanks /;^)

(1) Update on Business Communications – June 17 2009
http://n5fdl.com/davids-blog/2009/6/17/important-update-on-business-communications.html

(2) N5FDL White Paper with background and FCC responses.
http://n5fdl.com/97113

(3) ARRL issues their insight in September QST
http://www.arrl.org/news/features/2009/09/01/10982/

(4) Alabama Section ARES responds
http://www.hmcraces.org/BB/viewtopic.php?f=3&t=238

(5) Updated 97.113 Guidance from N5FDL on 18 September
http://n5fdl.com/davids-blog/2009/9/18/dont-panic-97113a-can-be-dealt-with.html

We all know that the only radio contesting I ever participate in is the VHF contests… and even then it is only to see if I can beat my previous score. It certainly is not to impress my wife. With ‘in-attic‘ antennas I’m about the only one I can beat. I’m actually pretty pleased with these antennas tho, because I don’t have to twist a rotator back and forth, and I can work just about anyone that I can hear. Sometimes I hear things the other guys don’t, cause they are pointed off to the side or something. Often omni-directional antennas get a bad rap, but they do have their advantages. I had some preamps on there last year, but then I could hear folks that can’t hear me. I do rely on other folks that have big antennas on tall towers with serious power for my DX. Still tho I really enjoy having so many stations on for a good weekend of VHF. Again this contest, we had a local ARES Simplex Exercise Saturday afternoon, to bring out a few more operators, and introduce them to the world of VHF without repeaters. Pretty good participation !

I don’t have a lot of space in my shack, and share the desk with my computer stuff.

the Radio side of my desk

N3FJP's VHF Contest Log

Anyway, having the laptop near the radios is useful not only for logging, but with so many new digital modes available now – my laptop is still my fastest computer, and has the most memory – so it works out well having a shared desk. I have enough wires running back and forth all around the room. I’ll keep the ones between the radios and the computers fairly short.

Computer lab / Ham Shack @ WB5RMG

73 for now. Thanks /;^)

Don’t forget the annual September VHF QSO Party runs from 1pm Saturday to 10pm Sunday (CDT) this weekend. Lots of fun meeting up with old and new friends in the region. Check the rules and other details on the ARRL website. The Alabama ARES group is also conducting a Simplex Exercise Saturday from 2-6 pm CDT, so don’t forget to listen on those FM frequencies as well for some extra contacts. Maybe we’ll get some new VHF contesters. If you scroll down further, you can see an example from the propagation map that NG0E generates from the APRS-IS beacon data-base. This is helpful to recognize where the signals might be strongest. Even if you are not into the contest for competition, it is a valuable exercise to see how well your equipment is operating. The rest of us will appreciate the additional contacts – so join in !
Enjoy /;^)

Tonight I managed to catch the International Space Station and the Discovery orbiter about 6 hours after they separated. I caught them in this two minute exposure with a Nikon D-40 as they drew a line in the sky from Texas to Michigan. It doesn’t take long at 17,500 miles per hour. You can’t tell from this time exposure photo, but Discovery was about 5 seconds ahead of ISS, and not nearly as bright. You may have gone outside to watch about 8:15 CDT… It is always very special to me to see them playing chase so far above. It seems so far away, but they are only about 200 miles above the surface of the earth.

ISS & Discovery leave streak across the sky.

Sample image of ISS groundtrack

An error correction method employed in amateur digital communication is known as Automatic Repeat reQuest (ARQ). I won’t get into those details here, but this mode can be used to ensure error-free delivery of simple messages over weak signal radio links as we often encounter in ham radio. In particular this method is available in the flarq program as part of the Narrow Band Emergency Messaging System (NBEMS) package. NBEMS provides amateur operators with the tools to operate several digital modes, regardless of whether they prefer Linux or Windows…

I follow a discussion group for NBEMS, and in response to some confusion over how much time it actually takes to transfer messages of various lengths using such error-correction, Dave – W1HKJ posted this nicely detailed summary of what all goes into the bit-stream. (I don’t expect everyone to fully appreciate this, but this is mostly for me and a few other hard-core bit-slippers) …

> — In NBEMSham@yahoogroups.com, “woodtownuk” wrote:
>
>> ‘When Image File is selected, Flarq can send a color, passport photo sized picture, in about 10 minutes using PSK250.’
>>
>> Am I reading this correctly? 10-minutes? Passport size picture?
>>
>> !
>>
>> Angus – UKCF DataNet Manager
>>

Assume that the passport photo is 200 x 250 pixels x 3 colors . This would typically be a compressed JPEG image with a file size of 10800 bytes.

That data must be formated using base64 encoding. Base64 encoding typically increases the data size by about 1.4. We are now at 15,120 bytes to transfer.

Lets say that you are using a block size of 64. The data is divided up into approximately 236 blocks of 64 bytes each. Each block requires both leading and trailing ARQ info.

bits in frame

Each data block transfer thus requires 8 + 64 + 1 = 73 bytes. 8 blocks are transmitted followed by a poll request. Each poll request can be up to 28 bytes long.
The receiving end responds with a status block report which again be as much as 28 bytes long.

A base64 encoded data file is a fairly uniformly distributed data set over the 64 allowable characters and averages about 9 symbols per byte.

Use this formula to estimate the transfer time using ARQ.

For an image:

Total ARQ Data = TQ = S * 1.4 * (1 + 16 / B))

Total ARQ transfer time = TQ / (60 * C)

where
S = file size in bytes
B = block size
C = average bytes / sec

C is dependent upon the encoding mechanism used for the modem in use. PSK, MFSK and others all use a VARICODE based upon the frequency with which each ASCII character is used in English documents.

Measured values of C for a 1024 byte uniformly distributed file:

PSK31 – 3.2 per second
PSK64 – 6.4 per second
PSK125 – 12.8 per second
PSK250 – 25.6 per second
MT63/1000 – 9 per second
MT63/2000 – 18 per second
MFSK-16 – 4.05 per second
THOR-22 – 5.6 per second

Transfer time = 12.3 minutes

You can use the TQ formula to estimate how long it would take to transfer a data file that is pure ASCII text (no base 64 encoding).

A 1 K text file transferred using 64 byte blocks takes :

sample transfer times

I hope this helps to explain some of the ARQ transfer time questions.

73, Dave, W1HKJ

::::::::::(re-posted with permission from W1HKJ):::::::::::::
This is obviously presented without context, but you can learn LOTs more from the website http://www.w1hkj.com/NBEMS/index.html as well as from the Yahoo Discussion group NBEMSham. Hopefully I’ll be posting more about this digital communications package in the future. Maybe this is enough of a taste to make you want more…
Thanks /;^)

Looks like some good VHF propogation for the eastern US coast this morning. Wish I was at home listening for some on 6 meters. This time of year is known for enhanced propogation at VHF frequencies. You can check this map for an overview of conditions based upon analysis of beacons heard via the APRS-IS network on 144.390 MHz. Here is the link : http://www.mountainlake.k12.mn.us/ham/aprs/path.cgi?map=na

VHF propogation indicator

I managed to spend a few hours in the ham radio room at the HMCEMA’s EOC Friday afternoon. The antique Kenwood radio we are using for the APRS station was in need of some adjustments to the setup, so I took the opportunity to clean up a bit and re-arrange some of the station components. There are still a few things to fix up, and possibly a ‘newer’ used computer to replace the old Windows98 system that is currently providing the APRS software (we are using UI-View32). Look for W4HMC-1 on a map near you. See all APRS stations in the area via http://aprs.fi.

Amateur Radio station @ HMC EMA