Of Course I Model! I Am A Ham For Crying Out Loud!

I am never satisfied anymore. I remember not long ago when simply walking up a hill was enough for me. “To get to the top!” blah, blah, blah… Then I discovered amateur radio and SOTA, and then it was “to get the top, BUT! Just with 15 extra pounds of radio gear, the pressure to make 4 contacts in order to get a point, and oh yeah, you only need ONE THOUSAND points!” blah, blah, blah… And now? Go ahead and add in that, well, lets just say, I am trying to figure out ye ‘ole antenna. I mean *really* figure it out. So c’mon and walk through this analysis with me. It’s interesting(-ish), and if you have anything to say about it, say it. I mean it. I want the critical feedback so I can really understand this stuff.

AA1F and I set out to scale Mount Wachusett in Princeton, Massachusetts for both a Parks-on-the-Air activation (K-4368) and Summits-on-the-Air activation (W1/CR-001). It was a perfect 70 degree day. We walked up the Administration Road to the Harrington Trail to the Jack Frost Trail. We ran into a grandmother who had gotten lost with her two young grandsons. Don’t fret, we helped them get out! Round trip, it was 3.3 miles with a vertical gain of 802 feet, and we only walked for 1 hour and 40 minutes.

Ok, the radio part: We both operated from the a wide path extending from the summit parking lot. The rig was my Yaesu 891 with a bioenno 15ah lifepo battery. My tuner had a dead battery pack, and therefore was unused. The antenna was the Radiowavz 20M endfed half-wave which I presume has a 9:1 unun (but am not sure). The end insulator of the radiator was erected at 20′ high into a tree, up a 7′ slope from the unun, for a total height difference of 12′ (see sketch below to understand this). The end insulator was pointed in a northwest direction, whereas the unun was in a southeast direction. The 50′ RG8X coax dropped from the unun to the ground and then circled around a bit to connect to the transceiver.

Below you will see the EZNEC model of this antenna (green) with transformer and feedline at one end (blue bullseye. The 3-D model is shown as well. The far field azimuth plot has a dbi of 1.57 in the outer band. Overall the antenna model predicts omnidirectionality (which is hard to assess practically when you abut an ocean on the east!) The photos show AA1F in the actual operating position with the antenna location above his head in parallel with the path.

The antenna modeling pattern is superimposed over a google earth depiction of Mount Wachusett. North is directly into the screen, whereas south would be coming out of the screen. The pink line in the inset shows the location of the antenna radiator. North is toward the top of the inset. The charts show the actual values added to EZNEC. I DO NOT THINK I MODELED THIS ANTENNA CORRECTLY. The feedline does not appear correct to me.

Finally, the maps below show AA1F’s (blue pins) and my (red pins) contacts. AA1F made 26 contacts between 3:52PM and 4:15PM eastern time (19:52 to 20:15 utc). I made 25 contacts between 4:26PM and 4:53PM eastern time (4:26PM to 4:53PM). The second map excludes the one dx contact (France) that AA1F made just to show better detail.

The graph shows the number of contacts (y-axis) plotted against the range in miles of the contact (x-axis). Approximately half of the contacts had a distance range between 1000-1249 miles. The chart shows descriptive statistics for the distances (in miles) of AA1F’s, mine, and total contacts. It is striking that we did not get any Canadian contacts.

The striking band of contacts situated approximately 1000 miles in a west and southern sweep from our operating location on the summit of Mount Wachusett in Princeton MA (Elevation 2003′) is interesting. It greatly appears that the propagation is broadside in this configuration of a 20M half-wave endfed radiated with 100 watts SSB. This seems to be somewhat against the conventional wisdom that the propagation is parallel and somewhat toward the insulator end of an EFHW antenna. Time of day of course may play a role, and eastern propagation (due to the ocean) is not particularly assessible.

Thanks and 73s!
KM1NDY

A Little History: The Gates House

The OlIve Gates House of the South Druim Tract of the Wachusett Mountain reservation as it appears today and as it did in 2006. The gates family bequeathed 211 acres to the Commonwealth of massachusetts in 1969. it is part of a late 18th century farm.

I want to operate from the porch of this dwelling before it is too late.

(photo left from: PRINCETON RECONNAISSANCE REPORT, FREEDOM’S WAY LANDSCAPE INVENTORY, MASSACHUSETTS HERITAGE LANDSCAPE INVENTORY PROGRAM. https://www.mass.gov/doc/princeton/download)