Jump to content
  • 0

Slim Jim Antenna vs 1/4 Wave Ground Plane Results


cdesigns
 Share

Question

I currently have a 1/4 wave antenna up in a tree 22' feet high, it works great, but I'm still unable to reach some local repeaters or reach certain areas "Home to Car" around my area. So I have been looking at high gain base antennas but they are all to tall,  so I decided to make a Slim Jim and do some testing with some of my toys.

 

Both antennas were designed using online calculators and tuned to 462mhz

 

I tested the antennas with a:

138mhz-4.4ghz USB Spektrum analyzer

Digital VHF/UHF SWR meter 

Radio used on the test Baofeng UV82

Both antennas used 30' of rg8x coax and altitude of 7' from the ground

 

I was using a steady transmission close by as my reference:

The ground plane had 1-2db gain over the Slim jim when the antennas were inside the garage with the door open, the ground plane could pick up the "reference" signal better, I was a little disappointing, BUT once I moved the antennas outside the slim jim gain 2-3db over the ground plane. My current ground plane installed 22' from the ground had the same gain the slim jim installed only at 7'.

 

This Slim Jim likes altitude, playing around the higher it went the more gain it had over the ground plane both at the same altitude, I could only datalog the 7' altitude gain wich is about 2-3 db more than the ground plane, can't wait to test it at 22' .

 

So far I recommend the Slim Jim over the 1/4 wave ground plane, but I still need to do some testing at 22' and compare. hopefully tomorrow if it stops raining , hurricane Mathew is entering FL tonight lol.

 

Antennas:

 

Antenna1.jpg

 

Antenna2.jpg

 

 

 

Link to comment
Share on other sites

12 answers to this question

Recommended Posts

  • 0

The RG8X may be fine for 27 Mhz. CB frequencies, but the attenuation rating at 462 mhz is substantial.  It just is not designed to operate well at UHF frequencies.  If you want better performance, and your budget will allow, upgrade to a 25 watt type certified radio and 3/8 inch hardline.  You can build a 5 db antenna system using a center loaded mobile antenna and an NMO mount radial kit. 

 

Antenna: http://www.theantennafarm.com/catalog/pctel-asp76551-827.html

 

Radial Kit: http://www.theantennafarm.com/catalog/pctel-maxrad-mbsuhf-1651.html

 

Best of luck with your project...

Link to comment
Share on other sites

  • 0

The RG8X may be fine for 27 Mhz. CB frequencies, but the attenuation rating at 462 mhz is substantial.  It just is not designed to operate well at UHF frequencies.  If you want better performance, and your budget will allow, upgrade to a 25 watt type certified radio and 3/8 inch hardline.  You can build a 5 db antenna system using a center loaded mobile antenna and an NMO mount radial kit. 

 

Antenna: http://www.theantennafarm.com/catalog/pctel-asp76551-827.html

 

Radial Kit: http://www.theantennafarm.com/catalog/pctel-maxrad-mbsuhf-1651.html

 

Best of luck with your project...

 

I'm going to use this antenna with a Vertex Standard VX-2500 UHF 25watts. The antenna you posted  I saw it before but it will not work on my "hidden from HOA" install. I do plan to upgrade the coax to LMR400 soon

 

This is my current setup

 

Radio and hidden tree antenna, the new antenna has to be hidden on the tree.

IMG_1797.jpg

 

IMG_1794_1.jpg

 

tree.jpg

Link to comment
Share on other sites

  • 0

What about an Ed Fong style dual band antenna? I'm planning on building one for Ham use, and I think it should work for GMRS as well.

I love his antennas! I've ordered lots. I'm looking into making my own for the fun and learning of it. 

 

I couldn't hit a GMRS Repeater about 15 miles away with a 25 watt base unit with an antenna about 8 foot up, but when I got Ed Fong's antenna, I put that up in a tree about the same height as the other antenna, and with 4 watts, I could hit it and receive it clear as day.. And nothing was wrong with the base or antennas, I tried 2 different radios and 3 different antennas, and 3 different locations, Ed's antenna worked great, and I appreciate the hours he spent with me on the phone talking about repeaters and the process of building his and everything. 

Link to comment
Share on other sites

  • 0

I love his antennas! I've ordered lots. I'm looking into making my own for the fun and learning of it. 

 

I couldn't hit a GMRS Repeater about 15 miles away with a 25 watt base unit with an antenna about 8 foot up, but when I got Ed Fong's antenna, I put that up in a tree about the same height as the other antenna, and with 4 watts, I could hit it and receive it clear as day.. And nothing was wrong with the base or antennas, I tried 2 different radios and 3 different antennas, and 3 different locations, Ed's antenna worked great, and I appreciate the hours he spent with me on the phone talking about repeaters and the process of building his and everything.

 

I used the wrong materials on mine, thats why it didnt work to well, but Im pretty sure is an excellent antenna.

Link to comment
Share on other sites

  • 0

Another test, here I tested 3 of my antennas:

 

DIY 1/4 wave ground plane antenna

DIY slim jim antenna

Arrow (MURS/GMRS) antenna

 

numbers don't lie, the Slim Jim claims to have 6dB and I believe it was measured against a 1/4 wave ground plane, well I did the same test and my gain was 6.69dB over the 1/4 wave ground plane and 3.44dB over a nice Jpole.

 

I also did a test putting the Slim Jim only 12' high and I got better signal than my 1/4 wave mounted at 22' feet high.

 

Highly recommended 

 

antennatest.jpg

 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Answer this question...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use and Guidelines.