Modeling radio antennas and a very brief primer on the science behind the range we get.

[SteveShannon]

Every one of us at one time or another has either asked or attempted to understand the science of antennas on handheld radios.  This video, by a well known ham radio antenna manufacturer, simulates a quarter wave antenna, held at ear height and illustrates the gain. It’s a short video and doesn’t go nearly far enough, but it’s interesting and could be a starting point for more in-depth conversation.

The simulation software Callum uses is freely available here: http://gal-ana.de/basicmm/en/#180

And here is a video tutorial for how to use the simulator program:

Finally, here’s the video on small antennas:

 

[Lscott]

The other modeling software I use is EZNEC.

https://www.eznec.com/

In any case modeling antennas is a great way to get a feel for what is going on. Now testing small HT antenna is something else!

[Lscott]

This is part of another thread dealing with the possible access of a US located GMRS repeater by unlicensed GMRS users in Canada. Its another response to the following post.

https://forums.mygmrs.com/topic/5213-cross-boarder-usacanada-gmrs-communications/#comment-52029

This is the repeater in question and the approximate coverage zone.

https://mygmrs.com/repeater/6815

It got me thinking is there a simple way to do it without having to use Yagi antennas. The answer seems to be yes. I'm putting the results here since it really shows how the power of antenna modeling can be used to answer some basic, but important questions, to solve real problems.

The simplest idea is using two "phased" 1//2 wave vertical dipole antennas spaced apart on a boom and rotated to the desired angle. You get a cardioid pattern where the "null", back side of the cardioid, can be place along the US-Canada border while still covering most of the intended targeted US coverage zone. It doesn't reduce the signal to zero but likely enough it won't prove attractive to bother with unless the station is very close by.

The software used here was EZNEC.

 

[SteveShannon]

Very cool, @Lscott!  It would be great if the antenna manufacturers all provided EZNEC models of their antennas.  I’m thinking it the DB404-B and how the folded dipoles can be rotated on their mast to accomplish exactly what you’ve illustrated.

[Lscott]

22 minutes ago, Sshannon said:

Very cool, @Lscott!  It would be great if the antenna manufacturers all provided EZNEC models of their antennas.  I’m thinking it the DB404-B and how the folded dipoles can be rotated on their mast to accomplish exactly what you’ve illustrated.

Yes it would. Another poster, gman1971 I think which I haven't seen posting in a LONG while, talked about putting up a 4-bay vertical. I was curious how it looked from a coverage point of view since he said it was directional. I simulated to see. It does have some directivity but it's not huge.

 

[gortex2]

I assume it also depends on where the elements are on the dipole. All on one side will throw some RF one way. I have a mix match of them. On VHF I have one with all 4 elements to one side and it helps cover an area and put more gain in that direction. At home I have a single dipole on each bearing (N, E, S, W) so less gain but more omni. 

[Lscott]

10 hours ago, gortex2 said:

I assume it also depends on where the elements are on the dipole. All on one side will throw some RF one way. I have a mix match of them. On VHF I have one with all 4 elements to one side and it helps cover an area and put more gain in that direction. At home I have a single dipole on each bearing (N, E, S, W) so less gain but more omni. 

That’s about right. The mounting pole acts as a reflector for the elements giving a bit of directivity to the array when they are all mounted on one side. 

If someone is looking at this type of antenna they should keep the above in mind.