Amateur (Ham) Radio BS and Callsign Thread!

Yeah, thank you. I am aware of that bracket but I'm wondering how bad my signal would be if I mounted one the way I described. One reason is that i don't want to have a huge antenna visible.

 

It's shit. We had them on patrol cars way back when...

First thing that came up when I googled.


"I've had quite a bit of experience with glass-mount mobile antennas.

Don't do it.

Some modern automotive glass has metal incorporated into the mix. This will
attenuate the signal passing through the glass. Further losses happen in
the coupling box.

Our shop was tasked to install this type of antenna on a fleet of identical cars
at the insistance of the fleet manager. Even though the antennas were
mounted in exactly the same place on each car (we had made a template)
they were all different in tuning. Sometimes it took hours to get the tuning
to come out right. Since the coupling box and the antenna mount were
"permanently" adhered to the window, you could not swap them out.

In the end, they were all removed and replaced with covered "skate"
antennas which were less awful.

These things are difficult to tune. A tiny adjustment on the inside coupling
box produces a large change in VSWR. Once adjusted, these things are
difficult to keep tuned. Heat in the car's interior (sitting in the sun in the
summer) affects the tuning.

Car washes tend to snag on the outside whip and suddenly detach it. This can
be a problem with mag-mount antennas as well if you fail to remove them
before entering the car washing facility.

...

(Edit: TNcR makes a good point about seeing these on the rear window of
pickup trucks. The near-vertical orientation of the rear window is about the
worst place on a pickup to mount these as the proximity of the cab roof near
the bottom of the antenna screws up the pattern.)

RF energy can leak from the feedline and cause all manner of trouble with the
entertainment system, engine control and the host of sensors that tell modern
automobiles what to do and when/how much to do it.
If you install this kind of antenna, please consult with the auto maker to determine
how to route the cable so as to keep interference with the auto's electronics to a
minimum.

These antennas are almost always end-fed, half-wavelength. There is a current
fad in the amateur radio community attributing all sorts of benefits to this type
of antenna. The behavior and quirks of this type of antenna are either not
known to the proponents or intentionally omitted.

Also, if you run high power on 2m, you will let all the smoke out of the coupling
box. In my experience, 50w out is the limit

For the amateur radio operator - railfan, there is an additional disadvantage
in that when you finally get the thing tuned for 2 meters, it is so narrow-banded
that it will be nearly deaf on the RR frequencies "

 

Thank you. Very helpful. Still considering options. One concern is that my work sometimes takes me to some shady areas where i have to leave the truck parked and i would rather not have to remember to take off a mag mount (i know i would forget to do it). Rather not advertise that there is an expensive radio inside. so, looking for something with a bit more stealth.

 

Shit.... That sux. Have you considered a lip mount for your hood? That might make it look more like an OEM antenna? I wouldn't want to drill holes in my roof... I'm not that committed to anything in my life.

 

The lip mounts that i have seen have no "stealth." i might have to get creative.

 

That's kinda what I'm doing right now, except I pulled cable through the window. Just trying to avoid potential adverse reactions of a magnet on the roof, and pick more permanent mounting location

 

I still haven't done the math, but a legally powered CB antenna on a ditch light mount doesn't scare me at all. Unlike squirting 50w into a 2m gain antenna, which does scare me.

That being said, a top loaded antenna is putting out more energy at the base then at the top. Assuming its designed to be a 1/4 wave. The high current / low voltage point is at the base. Which is where most of the power is leaving the antenna. With less power leaving the antenna as you approach the tip where you have low current and high voltage.

 

As others have pointed out, this seems like it would be annoying when trying to mount anything else to the bed rack. You certainly don't want to mount anything else conductive anywhere near the antenna.

From an RF perspective, it should work fine for 2m / 70cm. Many people mount on those Back-Racks rear window guards. They work fine. As long as you have a good electrical connection from the coax shield to the rack, and the center conductor well insulated.

Drill that hole in the roof! Lol. I understand that it's not for everyone. But when you're ready to drill, check out breedlove mounts. They're top notch.

 

Someone in another thread proposed he was manufacturing an NMO mount tab, that screwed in behind the 3rd brake light. He dropped the ball on it. Someone else liked the idea, and fabricated one for himself.

I think it's a great concept for those that want an NMO, and aren't willing to drill.

https://www.tacomaworld.com/threads/3rd-brake-light-antenna-mount.530201/

How do we get these in production?

 

https://www.evilmanufacturing.com/lights/2005-toyota-tacoma-third-brake-light-baja-designs

 

Thanks for your input. I figured it would be a better idea to remove a mag mount from the roof, and since I'm still reluctant of drilling my roof *, this would be a next best thing. Since the rack is not really being used to carry big things on it, the antenna should be safe there. Rack sits a few inches below the roof line, so I'd bend a steel bracket to raise the antenna a bit (radiation). I was just trying to figure out how would that whole idea affect performance.

@BenMara Thanks for info

Yeah, I think I'll pass... It will be way better cheaper to bend a steel bracket and slap it onto the rack.




* also, if one would drill and install antenna on the roof, how bad of an idea would it be to put up a Prinsu style rack, and essentially surround bottom of antenna with aluminum cross sections?

 

I made my own. Sandwiches between the cab and the 3rd brake light. I still had to drill into the cab to better secure the bracket. My 1/4 wave has a spring and this mounting point allows me to pull into the garage. Yes, the antenna hits but it would tip over with the mag mount. Now it stays in place. The area of the cab is strong so I haven't flexed the cab enough to dent it from the forces of the antenna spring.

 

When you do drill a hole, make sure you also use a large diameter fender washer on the inside or something that distributes the load of the antenna since our sheet metal is very thin. I have two antennas on my roof. I took out the headliner, tacked in some 2.5” washers. While I was there, I insulated some polystyrene.

 

https://www.breedlovemounts.com/nmo-mounts.html

 

Serious hardware there.

 

I have purchased a few NMO's from Breedlove. Serious hardware indeed. Quality stuff. I have the model #504 on my 2015 DCLB. I regularly run a 2m/70cm dual band, that fits under my garage door. But I also have a CR8900 for the occasional ventures onto 6m repeaters in the area. I've also installed a few Model #503's as well on other vehicles. I felt the sheet metal was too thin on the Taco to support the cr8900 on either a conventional NMO or the #503.

 

Finally got my radio installed.

 

Agreed, when I did my NMO mount in the top of my cab, I used a 1/4inch × 4 inch diameter piece of mild steel as a "washer" underneath the metal of the cab. I used JB weld though. It has held up great! And I have dang near did DOT's job for them with my antenna on some streets in regards to branches.

 

Sweet. What radio / antenna did you go with?