Extender Antenna Placement

[KK6ZTE]

Good evening all,

I'm trying to determine the best place to locate the antenna for my SVR-250U. It is interfaced with a Kenwood TK-7180 that is colocated with a TK-8180. Center of roof is a VHF antenna for the 7180. 19" forward of center is a UHF antenna for the 8180.

My vehicle is a small SUV, so no trunk lid (very few flat surfaces). I'm kind of lost for ideas. Right now the SVR antenna is on a mag mount on the front cowl (but it's making me twitch).

I'd love to hear some tips or experience about the extender antenna placement that will prevent damage from the other UHF radio on the truck.

Thanks!

 

[madrabbitt]

Good evening all,

I'm trying to determine the best place to locate the antenna for my SVR-250U. It is interfaced with a Kenwood TK-7180 that is colocated with a TK-8180. Center of roof is a VHF antenna for the 7180. 19" forward of center is a UHF antenna for the 8180.

My vehicle is a small SUV, so no trunk lid (very few flat surfaces). I'm kind of lost for ideas. Right now the SVR antenna is on a mag mount on the front cowl (but it's making me twitch).

I'd love to hear some tips or experience about the extender antenna placement that will prevent damage from the other UHF radio on the truck.

Thanks!

If the VHF is center-of-roof, and the 8180's antenna is centerline and in front, do you have anything thats centerline towards the rear?
What type of SUV, and is the OEM am/fm/sat antenna in that position?

With the accepted "1/4 wave of separation" concept, you've got that between the VHF and first UHF. Putting the second UHF 19 inches behind the VHF would work. Figure 19-20 inches is a quarter wave for VHF.

In addition, since its a low wattage repeater/extender, i'd think getting the antenna as high as possible would be more important then getting a perfectly centered ground plane. With the 1/4 wave of UHF being in the 6 inch range, you could probably offset the antenna to either side of the roof if you needed to.

 

[AI7PM]

Mount it off center. I have four on top of mine. Two down the middle, and two either side to keep the spacing.

 

[com501]

Patrol vehicles always get the SVR antenna mounted under the hood, usually on a bracket in front of the radiator. The SVR needs to be isolated from the other radios as much as possible.

 

[KK6ZTE]

My vehicle is as far from a patrol vehicle as possible.

It's used as a scout when entering active fire situations to guide the trucks with horse trailers. We use it to recon addresses we're picking horses up from to make sure there's enough room to turn around and the area is safe for the truck and trailer. Being small and maneuverable is key for that. Most of the time, we're in valleys and canyons with little handheld coverage. The SVR is intended to fix that.

It's a 1991 Isuzu Trooper. See attachment. The UHF antenna isn't too visible like the VHF whip is but it's forward on center.

 

[W8VFD]

I have a VHF Pyramid extender and the antenna is on an L bracket on the front fender of my pickup truck and it works well there for me.

 

[com501]

My vehicle is as far from a patrol vehicle as possible.

It's used as a scout when entering active fire situations to guide the trucks with horse trailers. We use it to recon addresses we're picking horses up from to make sure there's enough room to turn around and the area is safe for the truck and trailer. Being small and maneuverable is key for that. Most of the time, we're in valleys and canyons with little handheld coverage. The SVR is intended to fix that.

It's a 1991 Isuzu Trooper. See attachment. The UHF antenna isn't too visible like the VHF whip is but it's forward on center.

Please reread my post. I was giving you guidance on what WE do, hundreds of times per year. My post stands. Try to keep that SVR far away from high power radios, even if you put the Pyramid filter on it.

 

[KK6ZTE]

Please reread my post. I was giving you guidance on what WE do, hundreds of times per year. My post stands. Try to keep that SVR far away from high power radios, even if you put the Pyramid filter on it.

I'm sorry, I did not intend to offend. I just made the comment to make it clear I'm no whacker.

I do value your input. What do you think of a front bumper mount?

 

[com501]

Eh, meh. The bumper is not typically part of the vehicle. The disguise antenna we do for TLA's have a counterpoise to the license plate antenna instead of a ground. It might work OK for you if you don't wish to clutter your view with a lip mount on the hood rail. The 'can' antennas seem to work well enough for SVRs.

 

[KK6ZTE]

Okay thanks. The only reason I considered it was because I have a metal bumper

 

[KK6ZTE]

com501, when you put the antennas on an angle bracket under the hood, did you do anything for a groundplane? Were you just using 1/4 wave antennas?


Pyramid Tech Support suggests having them as far apart as possible on different vertical planes. I'm wondering if mounting on the windshield cowl will work. Right now it's on a magmount mounted there and it works fine but I haven't used my UHF mobile.

 

[com501]

We use the 'can' antenna, which is about 4 inches in diameter and 4 inches tall. The SWR isn't the best but they work OK in this application.

 

[KK6ZTE]

Thank you! Have one on order.

J

 

[KK6ZTE]

Eh, meh. The bumper is not typically part of the vehicle. The disguise antenna we do for TLA's have a counterpoise to the license plate antenna instead of a ground. It might work OK for you if you don't wish to clutter your view with a lip mount on the hood rail. The 'can' antennas seem to work well enough for SVRs.

What if I just mount on the hood itself instead of a lip mount?

I think that would be more aesthetically pleasing vs the lip mount and it could get a full ground plane if I put it in the right rear corner. I'm not concerned with the RF exposure from 1.5W

 

[Project25_MASTR]

This almost seems like a better application for the Wireless Pacific X10DR.

The real issue seems to be attempting to perform in-band repeating since two high power mobiles are being used.

 

[KK6ZTE]

This almost seems like a better application for the Wireless Pacific X10DR.

The real issue seems to be attempting to perform in-band repeating since two high power mobiles are being used.

No, there is no in-band repeater. As I described in the initial post, the UHF Pyramid is connected to a VHF mobile. The concern I have (and thus the point of the post) is to protect the Pyramid from the occasional TX on the UHF mobile (not attached to the Pyramid).

 

[Project25_MASTR]

No, there is no in-band repeater. As I described in the initial post, the UHF Pyramid is connected to a VHF mobile. The concern I have (and thus the point of the post) is to protect the Pyramid from the occasional TX on the UHF mobile (not attached to the Pyramid).

I was referring to the UHF mobile and he UHF pyramid. I thought I read you had the two Kenwoods in a dual radio single head configuration.

As I understand, part of the issue is keeping he UHF mobile from destroying the front end on the pyramid.


Sent from my iPhone using Tapatalk

 

[KK6ZTE]

Exactly. I have mounted the can antenna to the cowl on the passenger side. It's in line with the windshield wiper protrusions so it's aesthetically OK. I'll be installing a pass cavity on the SVR just to add a little extra isolation. There will be only one channel (very rarely used) that's relatively close to the SVR frequency.