Ham Radio -- Miscellaneous Editorial Opinions

back to ham radio

600 meters 2007 June 9

The 600 meter experimental folks (WD2XSH) are working to try to open up a new emergency capability within amateur radio, communications up to 100 miles regardless of ionosphere conditions.  We don't have this now below 30 MHz, our lowest frequency being 1.8 MHz which can "go out" over this range in the middle of the night at low sunspot times.  600 meters is .505 KHz, just below the AM broadcast band.

Problem is, most of the participants seem to be more interested in DXing each other, making trans-continental and inter-continental QSOs, than developing that portable, KW class station and suitable antenna for an emergency response that could provide regional data intercommunications.

I have one data point about skipping in the 300-600 m. range. Before we were married, when Viann was in nursing school in Dallas and I was still in Waco (so this would have been winter 1978), I left Dallas to drive back to Waco at about midnight one Sunday night (Monday morning).  This was at a time when I had no mobile ham equipment and the car had only an AM radio.  Although there are several big AM stations in Dallas/Ft. Worth/Waco and further out like Houston/Lubbock, that would be broadcasting all night (WFAA 570, WBAP 820, KHOU 1070, WACO 1360, etc.), there was only one station I could hear and it was in Chicago.  I've forgotten the call/freq., but I do recall that even they were going into their weekly maintenance period so although they had a carrier on and would occasionally make announcements; there was no programming.

That was a lonely drive and I was impressed by the size of the apparent skip zone even down at those frequencies.  I was used to 80 meters going out mid-evening over a well-known 100 mile path, but this was a lot lower in frequency and larger in distance than that. True, the antennas involved were not optimized for NVIS, but there should have been some pickup nonetheless.  After all, that's how AM works during the day in some of the prime market.

So are the 600 m. guys mostly interested in demonstrating "DX" potential?  Do they have no interest in situations that are already traditionally covered by VHF?  What are the stated goal under the experimental license?


Around the World Echos  2007 May 23

In QST for June 2007, page 72, Gene, K4MOG reported on hearing his own CW signals around the world on 3524 KHz.  The delays were longer than would be expected from the earth circumference distance.  Explaining the additional distance was a problem.  I did the trig problem here:

"Thoughts on the additional delay you measure with respect to the delay time you should see if he signal follows the circumference of the earth.

"I find it more useful to think of the extra delay as a ratio rather than extra miles travelled.

"At the speed of light it would take 300,000/40,075 = 134 msec to travel right along the circumference of the earth.  You measure 165 msec so the ratio is 165 / 134 = 1.234.

"Consider the additional distance travelled by a signal making several ionospheric hops as it goes around.  The additional length of a circumscribed polygon with N sides over the circumference of the circle is given by

ratio = tan( pi / N ) / ( pi / N )

This gives:

N    ratio

4    1.273
5    1.156
6    1.103
7    1.073
8    1.055

"For F layer hops, a number like 7 or 8 is most likely, corresponding to a skip distance of 5000 km.  (Of course there is no guarantee that every skip will be the same.  Also, some might be E, some might be F, but this gives a working guess.)  The ratio corresponding to a circumscribed square (N=4) is closest to your observation, but the ionosphere is not (sqrt( 2 ) - 1 ) * Radius_earth = 2640 km high, so something else is going on.

You'd expect some media delays in the atmosphere and ionosphere.  I would be surprised if, even over this long path at 3.54 MHz, they were more than a few milliseconds.

"Another possibility you might consider, and something that it might be possible to measure directly, is the difference in delay between the CW sidetone going through your radio and an RF signal going through all the filters, mixing, and demodulations to the output you hear in the speaker.  Ten or twenty milliseconds wouldn't be surprising at all for that and it could be much more if there is any DSP involved.  That could explain the whole discrepancy right there.

"In any case, it is very valuable that amateur radio operators take an interest in these phenomena and make measurements such as you have made to qualify and quantify what they have heard.  It is from such investigations that useful discoveries continue to be made.

"Good work and keep calling CQ!"

Gene responded that they had isolated the extra delay to filter delays in the radios.


Creeping Functionality on SuitSat 2 2006 November 11

As SuitSat 2 is being developed, there is talk of putting a software defined transponder on it.

It's an interesting demographic, AMSAT.  Like me, the AMSAT guys want something complicated to work on.  This is directly opposite to the need to "make it popular and accessible."  This tension lives throughout the history of the organization.  Read the archives.  Look at the payloads.

So, what happens is that AMSAT today is very similar in makeup to what it was 35 years ago, about two dozen hard-core fanatics headed towards divorces who are surrounded by about a hundred people like me and a couple thousand dues paying members who vaguely but unrealistically wish they could be in the center of things too.

If AMSAT ever does something that is truly popular, like the "talking to astronauts" programs or "university involvement" which has become Cubesats, the efforts turn out to be split-off organizations.  ARISS has become kind of an uncomfortable Siamese Twin with AMSAT.  Anybody building and using Cubesats, is considered by traditional hams as problematic, barely licensed usurpers.  This, even though the program is so successful that a bureaucracy had to be set up to coordinate their frequencies, even when they're not aware of and don't care about the need for their frequencies being coordinated.

As for the present exhibit, good grief, let's make SuiteSat 2 into an AO-40 in a worthlessly low orbit, something that even the most obsessed devotees won't be able to utilize, even if they are at the right latitudes?  Is this "fun?"

To be really popular in a classroom, you have to stay away from what guys like us think is "fun."  It needs to be an FM quality link that just plain works.


created 2007 October 12, cbd