Help with Monkey Made antenna

[jessejamesdallas]

I'm still wrestling with the difference of a 22" vs 6", and all between, for mounting on my 4.5" Breedlove top dead center of my large rooftop.
years ago I did an experiment. I won't go into that here now.

Roof mounted, I would stay away from anything shorter than 12"...Personally I think the 17" shaft is perfect for roof mounting...22 and 27" shafts will tune lower on the roof, but are also easier to get broke off the roof because you have just too much solid antenna sticking up that wont bend out of the way if it hits something like a tree limb...(By the way, when a Predator 10K breaks, it's almost always at the base of the lower shaft where the studs at that screws into the antenna mount, I have yet to see one snap any place else)

6" and 9" lower shafts I have never-ever been able to get to tune worth a flip, and even had problems getting the 12" shaft to tune very good...But, if your flexible about where you want to put your mount, then you might find the right spot to use one of the shorter shafts...I've just usually have a spot all picked out for the antenna, then have to figure out how to get the things to tune where I want them.

This is a single-coil 10K on a 27" shaft that I had on top of my Suburban, until a low hanging phone line snagged it and snapped it off the roof and sent it flying...found the antenna about 75 yards off the road up in one of my neighbors front yard.

 

[jessejamesdallas]

Yes, I also read something about that. The top of a tool box in a pick-up bed is just about the same height as the top of the bed rail. Placing the antenna in the center of the tool box would probably be more efficient than where my antenna is located.

Word of advice if you go this route...Toolbox's are not grounded! And it can be time consuming to get a good ground on one...It's almost impossible to get a good enough ground on a toolbox's lid, since the lid is just held on by some hinges with a rod running through...You would need to run ground straps off the lid to the rest of the toolbox, and also it would need straps ran to the frame to get ground...Then if the toolbox is sitting on top of a bed liner, then there's another problem to deal with....

-just some "FYI"

 

[jessejamesdallas]

there is a archived thread here where Kale explains the different shaft lengths and says that the 27" was for tool box mounts.
I'll see if I can find it again

This is true! The original idea for the 22 and 27" shafts was for guys to mount the antenna on toolbox's or behind the cab to the top of the bed rail...The taller shafts were never meant to be used on roof tops... The 22" works good on trunk lid mounts...provided you have a car that has a metal trunk lid...now days most are plastic.

Toolbox mounted 10K's with the 27" shaft can work out good..."IF" you can get a decent ground off the toolbox...most can't.

 

[jessejamesdallas]

Thanks! I went looking on the internet for replacing the shafts and did not find any info. Yes, the upper section has a 13/16" hex fitting as the lower section. I have a 1.2:1 to 1.3:1 VSWR now. Would I be gaining anything with the 27" shaft?

Mounted where you have it now? With a 27" shaft it "MIGHT" tune a bit lower, but like I said earlier, you still have almost two feet of antenna next to the cab.

One thing about all the Predator Antennas is, everything on the antenna is just screwed together... The coil section screws onto the shafts, the coil is held in place with set-screws like the stinger...the section where your 13/16 wrench fits is just screwed into a hollow aluminum tube that has been tapped on each end for the fittings...nothing is welded anywhere and all the parts can be replaced...Clays Radio Shop carries most all the parts.

 

[Recon]

Word of advice if you go this route...Toolbox's are not grounded! And it can be time consuming to get a good ground on one...It's almost impossible to get a good enough ground on a toolbox's lid, since the lid is just held on by some hinges with a rod running through...You would need to run ground straps off the lid to the rest of the toolbox, and also it would need straps ran to the frame to get ground...Then if the toolbox is sitting on top of a bed liner, then there's another problem to deal with....

-just some "FYI"

I will not install a tool box because I have a roll-up tonneau cover to keep the bed dry.

 

[Recon]

Mounted where you have it now? With a 27" shaft it "MIGHT" tune a bit lower, but like I said earlier, you still have almost two feet of antenna next to the cab.

One thing about all the Predator Antennas is, everything on the antenna is just screwed together... The coil section screws onto the shafts, the coil is held in place with set-screws like the stinger...the section where your 13/16 wrench fits is just screwed into a hollow aluminum tube that has been tapped on each end for the fittings...nothing is welded anywhere and all the parts can be replaced...Clays Radio Shop carries most all the parts.

I cancelled the order for the 27" shaft until I conduct a transmit and receive comparison test between the Predator with a 42-9/16" striker mounted on the bed rail and the Laird NMO 27-31MHz CB Antenna with a 47-1/2" striker mounted on the Third Brake Light Antenna Mount which has an average of a 1.2:1 VSWR on all channels. Both the base coil and antenna striker of the Laird antenna are above the top of the roof. It could be possible that the Laird would be better than the Predator because the bottom 22" of the predator is below the roof line. To be continued…..

 

[undertaker]

I have a 102 inch whip on the back of my tool box works just fine....

 

[jessejamesdallas]

I have a 102 inch whip on the back of my tool box works just fine....

They will...long as you have a good ground

 

[Highway Man]

They will...long as you have a good ground

With mobile it's all about the ground

 

[2NC995]

It could be possible that the Laird would be better than the Predator because the bottom 22" of the predator is below the roof line. To be continued

Curious how that works out!!

 

[Recon]

Curious how that works out!!

Ha! ha! What a coincidence you should ask. This morning I had driven to our local lake state park and parked in the middle of the wide open parking lot.
I attached the Laird coax to the Stryker 447HPC.
I established a clear and clean contact with a base station about six miles from my position. Leaving the Volume Control and RF Power Control knobs set, we chit-chatted for about three minutes, the incoming signal and voice recognition was great on both ends.
I removed the Laird antenna from the truck and disconnected the Laird coax from the radio and installed the Predator onto the Breedlove Stake Pocket Mount and attached the Predator coax to the radio.
Another three-minute chi-chat he told me that there was no noticeable difference in the incoming signal and volume on his end. At first he did not believe that I had changed antennas.
I have no doubt if the Predator was mounted on the roof, it would definitely beat-out the Laird, but I'm not going to install that monster Predator on the roof. I am staying with the Laird and leaving the Breedlove Stake Pocket Quick Release Mount on the truck and keep the Predator in a section of 3" PVC pipe in the bed of the truck.

 

[2NC995]

When I have tried comparing mobile antennas I have found the differences minuscule and hard to detect, but that was using the same mounting location.

I was one way or the other on what might work better for you in this case, a lot of it depending on directionality of the rail mount more than anything.

5’ is my magic number with antenna length...gains above that length seem very small, and losses below it seem large.

 

[Recon]

When I have tried comparing mobile antennas I have found the differences minuscule and hard to detect, but that was using the same mounting location.

I was one way or the other on what might work better for you in this case, a lot of it depending on directionality of the rail mount more than anything.

5’ is my magic number with antenna length...gains above that length seem very small, and losses below it seem large.

The Laird antenna is thin and only 43-1/2" tall and I'm staying with it because it will work well on the open turnpike.
I am exhausted from all the antenna experiments I have been doing, not to mention the expense of the antennas and antenna mounts.
I think the reason why the Laird is doing a good job is because the base coil and antenna are above the roof line.

 

[Slowmover]

When I come booming into your pickemup all the way from, “Where The West Begins”, with

El Presidente Tejas

you may change your mind.


Then, I’ll turn on the amp.

.

 

[jessejamesdallas]

When I come booming into your pickemup all the way from “Where The West Begins” with

El Presidente Tejas

you may change your mind.


Then, I’ll turn on the amp.

.

"Take no prisoners! "