Windom Antenna Analysis With The MR100.

[gil]

Hello,

This is the analysis of my 80m Windom antenna using the MR100 el cheapo Chinese antenna analyzer. Note that I am not quite sure the calibration was entirely successful... So take these results with a grain of salt, since some are somewhat puzzling... The length of the antenna is approximate since I made it a bit longer than calculated and later cut off about a foot... Coax length is 20m of RG-174. A bit thin but I needed something that would not pull down the radiating wire and go through a window.

The description of the antenna is somewhere in this thread: http://radiopreppers.com/index.php/topic,1096.0.html



















The 80m results aren't good but it seems a longer coax cable brings the SWR down, which suggests I still have some common mode currents on the cable even though I am using a dual-core Guanella BALUN.

The 40m graph suggests I might have shortened the antenna too much, though the SWR is still acceptable.

No surprise on 30m, it's not supposed to be resonant there.

The other graphs look weird. I think I need to do a proper calibration to verify these results. The plots look different depending on how the coax lays on the floor.

The graphs looked actually saner before I calibrated the gizmo. Anyway, It's fun to experiment.

Gil.

[Lamewolf]

Gil,

Looking at your 80 meter swr curve here and it looks like your antenna could benefit from adding the capacitor between the balun and longer wire, but if you do be sure and put the 1 meg 3 watt non inductive resistor across the cap to protect it from static damage.

[gil]

Well, in France 80m covers 3500 to 3800kHz. It seems only a longer coax lowers the SWR.. Do you think a capacitor would help? I won't take it down unless it falls, which could happen given the wind around here, but if it does I might try it!

Gil

[Lamewolf]

3.5 to 3.8 ?  I doubt it would help as it moves the resonant frequency up the band which would probably put it out of your privileges.  Didn't realize you could only cover the lower end of the band.

[gil]

Yep, same with 40m which only goes up to 7200kHz.

Gil

[Lamewolf]

Gil,

How do you interface the MR100 with a computer to get those nice looking graphs and what program do you use to do it with ?

[gil]

Hello. Connection is through a simple USB cable. I'll attach the software to this post.

I find myself using it all the time... Very useful piece of gear...

Gil

[oz123colin]

* WinPCC-Sark100.exe.7z  Downloaded this file but my Winrar is reporting the file is corrupt.:( Anybody having the same issue.???

[Sparks]

* WinPCC-Sark100.exe.7z  Downloaded this file but my Winrar is reporting the file is corrupt. :( Anybody having the same issue. ???

I am on a Mac and cannot really do much to help. The file downloaded OK, but cannot be opened on a Mac. Try removing the suffix ".7z" before opening, so your PC understands it's a .exe file may help.

[Sparks]

For what it's worth I found some links through Google:

http://www.sm6why.n.nu/sark-100
http://www.die-jetzis.de/sark100.htm
https://sark100-swr-analyzer.soft112.com/
https://sourceforge.net/projects/sark100swranaly/files/
http://ok1rp.blogspot.no/2015/12/60-mr100-antenna-analyzer-pc-interface.html
http://www.jh4vaj.com/archives/2537

[C-ya]

I just received my MR100 analyzer.  I found this site searching for it's use after I saw it on ebay.  I'm glad I did, as I have found some interesting topics on this forum.  You have even gotten me to download a CW app for learning and even going to the LCWO page.  I haven't signed up, but I plan to.

I'll try to post a few plots of my 80-40-20 OCF.  I'm having issues tuning it since I went from twin lead feed to coax and balun due to space restrictions at my current QTH.  With 100 feet of 300 ohm twin lead, it was pretty much "no tune".  With the balun and 50 feet of coax, 80 is tough for the LDG tuner, 40 is great, and 20 is not perfect.

Thanks for the forum and hopefully I can contribute a bit as well as learn a lot.  I have been lurker for about a month but I registered tonight to post in this thread and a Slim Jim thread.

[gil]

Awesome. I'll tell you, I came back from anything not fed at the center or at the end. Too much trouble with stray currents...
Gil



Sent from my SM-G928F using Tapatalk

[C-ya]

OK, I finally got some readings with the MR100.  My antenna is right on at 80 - imagine that!  40 and 20 are very high and require a tuner.  I haven't hooked it up yet and gotten scans with it but I'll try to do that soon.

I used two different programs.  Slightly different measurements but they tell me the same thing.  I only scanned the voice portion of the band for my privilege.

WinPCC plots







SM6WHY program

[gil]

Interesting...

I have almost given up on the Windom. The asymmetry creates a lot of stray current problems... I also had trouble with my MR100 after I calibrated it. I should have left it as it came. I plan on making a box with resistors and switches to calibrate again...

Gil.

[C-ya]

I have a "decade box" of sorts to use when I attempt calibration, should I actually do it.  We have a club event coming up on the 21st of April that I can compare it to better quality analyzers at the location we are doing the event.  There are 8-10 antennas on site, so I can compare the MR100 back to back with another analyzer on the same antenna.  If it looks similar, I won't calibrate it.