MMANA Antenna Modeling - My 160m inverted L

Had some quiet time over the holidays so I have successfully used MMANA Software to model my 160m Inverted L.   I can see that there is a huge advantage to building ,  optimizing and using an Antenna before building the model.  MMANA is fantastic but finicky for the casual user,  More then anything its just takes a bit of familiarity to be successful at it. 

So  here is my antenna.  The radials all slope away with the exception of the one that runs along the X axis ....more or less straight North.   The radiating element more or less runs along this axis too!














In reality the radials have not been tuned each one is 45.7 m long.  The program was told to optimize for VSWR and below is the recommendations for the radials. 


















The vertical component or if you prefer radiator started at 45.7 m.  Took at least a meter off tuning the antenna so its really very close to 44.7 m.   

The optimized length is 44.48 m. 

Performance...optimized to the above dimensions...

The data was all done using free space.   The radials are at a around are around -30 degrees off  level all but one sloping away from the antenna.   The antenna is sitting at the apex of a gravel hill and is connected via 500' of LDF4. 

Here is the same antenna not optimized .....the real deal.  Each radial is 45.7 m and the radiator is close to 44.7 m. 

The VSWR is quite a bit different.  In reality its around 1.5 to 2.0 at 1.85 MHz but the program does not have 500' of LDF4 connected to the antenna!   So the numbers are close enough to the reality to believe the model,  That being said I will have to try tuning certain radials to optimize performance.

BELOW is the model built with the actual dimensions.....

At 1.85 MHz ...

At resonance ...

At 1.85 MHz

Here is where the antenna is actually resonant....

At 1.85 MHz

At resonance ...

I really did find this antenna to be resonant 100 KHz lower in frequency around 1.7 MHz.   I brought it much closer to 1.8 MHz taking a meter or so off the radiator but did not touch the radials.   It truly is quite dramatic what a difference the modem show in  SOME of the radials to get it to resonate at 1.8 MHz. 

Regardless of the resonance one thing that remains constant is the deep null at 90 and 270 degrees  10 to 15 db is HUGE!!!!!   Planning on playing around with the model moving the AZ of the radiator ....this is something I can do in the real world too but before I do anything I would like to try tuning 4 of the radials particularly the ones that run east west. 

Late fall antenna tweaking...

Wasn't real happy with a few of my antennas so I decided to attempt to improve the match. 

20m 1/4 Vert ...just behind the house. 

Took some length off the Vertical element SWR is now

Freq        VSWR
14.0          1:1
14.5          1:1
14.1          1:1
14.15        1:1
14.2          1:2
14.25        1.3
14.3          1.4

Super happy with that ,  worked an RU this morning CW.  Tried to work a guy in Bulgaria but wasn't successful switched to the 160m vert at the top of the hill and was successful. 

80m inverted L ( 1/4 vert ) 

Took a wee bit off this antenna too but its not nearly as broadband as the 20m antenna.  Suspect a tweak of the radials might help that out but its not happening until the snow goes which may be April.

Freq      VSWR
3.45        1.9:1
3.5          1.45:1
3.55        1.4:1
3.6          1.5:1
3.65        1.8:1
3.7          2.2:1

So yeah,  I am mostly CW and FT8 on 80m so its great there however go up and not so much.   Think I may try a low dipole cut to 3750 for SSB. 

160m inverted L ( 1/4 vert )

Same this goes took a foot off the vert radiator

Freq        VSWR
1.7            2.1 :1
1.75          1.4:1
1.8            1.4:1
1.85          1.7:1
1.9            2.1:1

Again great for CW and FT8 but not so much for SSB.   This is my " magic " antenna that loads up on 40,  30,  20,  17, 15,  12, 10, 6 meters with just the antenna tuner in the radio!     I have had success on 6m meteor scatter running 100 watts into this antenna.   A while back ( in the blog somewhere ) I compared the 20m 1/4 behind the house with the 160m L up the hill and the big guy performed better! 


Here is how the 160m loads ...no antenna tuner!

Freq   VSWR
80m NO WAY ,  does not work
40m    3.6:1
30m    3:1:1
20m    2:1:1
17m    2.1:1
15m    1.5:1
12m    1.6:1
10m ( 28 MHz ) 1.4:1
10m ( 29 MHz ) 2.1:1
6m    (50 MHz ) 1.5:1
6m    (51 MHZ ) 1.3:1
6m    ( 52 MHz ) 2.1:1

From 50.6 to 50.9 MHz its a dead flat 1:1 VSWR...go figure

I use the 160 antenna when work FT8 remotely ,   no antenna switching required and I can flip around between bands super easy. 

Diggin a Hole

Late 2019 project is underway trying to get my 6m Yagi to the top of the hill!

Step 1 - DIG a hole ,  a really big hole.     Its  glacial deposits ,  about a foot of topsoil and rocks then a sandy gravel ,  rock dirt and root mix.

Step 2 -  Drop tower sections in the hole

Step 3 - Put all the rocks back in the hole.

Step 4  - admire the result

The rocks are as good as setting it in concrete.  The tower below was put up 20 years ago.  I use it to discharge the hill to cut down on lightening damage ... it works!

6m Amp

Picked up a 6m 600W amp a year ago!  It was sold as working but didn't work and is in the process of being brought back to life by VE3RIP... me an HV don't get along.  

Below is the Amp...

Lightneing Maps and 6m

Had some local lightening out over Lake Huron.   It shows up on the spectrum as well as on lightening maps .  Its cool to correlate where the strike that I am observing with the radio.

Lightening Induced Sporadic E

Being heard in Oklahoma as a result of lightening induced sporadic E.  

Its not meteor scatter and its a very short lived path so I deduce that its probably lightening induced sporadic E.

Hat Trick

Thought this was unique ,  worked VK Land 3 consecutive times on 20, 30 and 40 meters all using the same antenna the 160m inverted L.