Thoughts on what I created

[lexmedic157]

So I decided to make an attempt to make a scanner antenna. Went to Radioshack and bought a chassis mount, and some brass wire (couldn't find small enough single strand copper wire). I primarily use UHF and had a hard time getting a couple frequencies at the extremes of the county. So here I went.

I cut 4 six inch lengths of brass, put ring terminals on the ends of them and nut and bolted them to bolt holes on the edges of the chassis, and bent them down to 45 degrees. I then cut on six inch and one 12 inch section for the vertical. Had a little difficulty mounting the vertical (please let me know the best way to get it on the chassis). Attached it all up and it seems to work pretty well.

Question... what can I do to optimize this setup, and will I get better reception with the 6 inch vertical or the 12 (keeping the 6 inch radials)?

I also bought one of those eBay J-poles (not knowing better), and surprise, surprise it didn't work any better outside than the rubber duck antenna in the house. So I searched a bit, dissected the antenna and cut it to spec, and surprise it works pretty well for just being old school TV antenna wire.

Anyway, I am totally clueless at all the is ham radio stuff, but I think I'm slowly getting addicted!

 

[lexmedic157]

Terrible pics for reference

 

[zz0468]

The vertical element should be 1/4 wavelength long. The ground plane radials should be a little bit longer. At uhf, 1/4 wavelength is going to be approximately 6 inches.

 

[lexmedic157]

Ok, the vertical and all the radials are the same, 6 inches, correct?

 

[zz0468]

Ok, the vertical and all the radials are the same, 6 inches, correct?

Yes, and most antenna design books will tell you to make the radials about 5% longer.

 

[lexmedic157]

BTW, pay no attention to how/where it's mounted. I wanted to put it there until I was done modifying it. I have some PVC I'm going to stick in the ground and clamp the antenna to it.

 

[AlmostHandy]

Hey lex I love your work. Much nicer looking than mine. I wanted a multiband scanner antenna, and went with the groundplane design as well. You can see the first one I made here and an upgraded version here.

 

[lexmedic157]

If I were to make another antenna like the above for another freq range, would it be acceptable to put a BNC t-connector at the scanner and but up the new antenna along with the current, and not have problems?

AlmostHandy, thanks for the compliment, first attempt, I'd like to fine tune the design and the frequency span for better gain, any suggestions?

 

[zz0468]

If I were to make another antenna like the above for another freq range, would it be acceptable to put a BNC t-connector at the scanner and but up the new antenna along with the current, and not have problems?

No, it would not be acceptable. Read the sticky at the top of the antenna forum called "Running one scanner with multiple antennas". It well tell you everything wrong with that idea.

 

[lmrtek]

If you use an 18 inch radiator and the 6 inch, you will have good performance on 155 and 460mhz

 

[hoser147]

So how did it work for you so far?

 

[DELCOLHFC]

I'm not sure how you have the verticle element attached to the chassis mount center pin but a decent soldering iron would make the connection a lot more solid, just don't go crazy with the heat and damage the plastic portion around the center pin. I have a 60 watt iron that knocks out jobs like that very quickly. You may also want to add some solder to the ring terminals on the radials too (terminal to rod joint) it will help keep the connection solid over time with exposure to weather and temperature changes outside. My area uses a lot of "T-Band" UHF for public safety comms and I have built a couple of these type antennae tuned to 500MHz, they do help clean up the sound quality and improve coverage area compared to most commonly available manufactured antennae. Has your current assembly improved reception for you?