External Antenna Advice Needed

General questions on scanning from 30 to 3000Mhz. Not sure what you can receive in your area? Here's the place to ask!

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roland985
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External Antenna Advice Needed

Post by roland985 » Fri Feb 06, 2015 3:24 pm

Can anyone recommend a semi-permanent gutter mount solution?

I was looking at purchasing the following antenna to use with my Uniden UBC355XLT scanner:
http://www.prestigecom.net.au/axis-scan ... base-cable

But I need to know the following:

1) How can I feed the cable through the ceiling without doing much damage (ie small hole that I can plaster up)?

2) I need a longer run of Co-axial than what is provided with the antenna, where can I get co-axial that has a female BNC connector on one end, and a male BNC on the other?


Thanks for your time.
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vk6hgr
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Re: External Antenna Advice Needed

Post by vk6hgr » Fri Feb 06, 2015 6:46 pm

That antenna is not going to work well gutter mounted as it's not ground independent - it needs to be bolted into a large metal surface like a car or pergola roof.

On my mobile so can't link, but have a look at some of the base station scanner antennas made by Mobile One. Australian made, good quality and they can provide a custom length of coax.

For a really neat installation, I actually use RG-6 quad shield TV coax. The parts needed to make it feed neatly through a wall nicely, like wall plates, are readily available at Bunnings. You do get a little bit of.loss due to the impedence difference - 75 vs 50 ohms but that's more than made up for in the dramatically lower loss of RG-6 instead of the rubbish RG-58 the antenna comes with.

For scanning myself, I use dedicated antennas for each band - for FRS for example, I use marine VHF antennas.
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rustynswrail
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Re: External Antenna Advice Needed

Post by rustynswrail » Sat Feb 07, 2015 9:56 am

roland985 wrote:Can anyone recommend a semi-permanent gutter mount solution?
I was looking at purchasing the following antenna to use with my Uniden UBC355XLT scanner:
http://www.prestigecom.net.au/axis-scan ... base-cable
But I need to know the following:
1) How can I feed the cable through the ceiling without doing much damage (ie small hole that I can plaster up)?
2) I need a longer run of Co-axial than what is provided with the antenna, where can I get co-axial that has a female BNC connector on one end, and a male BNC on the other?
Thanks for your time.
Generally speaking for receive only applications that aerial will work fine attached to your gutter, assuming the gutter is metal. The gutter will form enough of a ground plain so as to not make that much of a difference. Transmit is a different story.

If possible, assuming you mount the aerial on the gutter, drill a small hole under the eaves of the house, route the cable through the wall cavity and bring it out through a blank plate, like those used to blank off power point and light terminations. Saves on plastering. The down side, the cable may not be long enough and you have to cut a hole, fit the gang plate (fits inside the wall cavity to hold the cover in place) and blank cover.

R

roland985
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Re: External Antenna Advice Needed

Post by roland985 » Sat Feb 07, 2015 10:52 am

Thankyou all for your advice.

I'm setting this up as a receive-only application. Any transmitting antennas will be ground - independent (I already have a 3 Dbi spare mobileone).

As rusty said, I'll route the cable under the eaves and through the wall, into a blank plate. That should really help.
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vk6hgr
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Re: External Antenna Advice Needed

Post by vk6hgr » Sat Feb 07, 2015 11:37 am

Ground planes do matter on receive. On strong signals using a roof gutter won't really matter, but on weak signals, the antenna will be noticeably directional.
Gavin Rogers; VK6HGR
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rustynswrail
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Re: External Antenna Advice Needed

Post by rustynswrail » Sat Feb 07, 2015 3:34 pm

vk6hgr wrote:Ground planes do matter on receive. On strong signals using a roof gutter won't really matter, but on weak signals, the antenna will be noticeably directional.
That's the theory and theory is a fine thing. But practice dictates otherwise, after many years in the 'industry' I can say with certainty that it will make very little to no difference. If you believe otherwise then so be it. I dare say the OP will no doubt post his results.

R

roland985
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Re: External Antenna Advice Needed

Post by roland985 » Sat Feb 07, 2015 4:45 pm

rustynswrail wrote:
vk6hgr wrote:Ground planes do matter on receive. On strong signals using a roof gutter won't really matter, but on weak signals, the antenna will be noticeably directional.
That's the theory and theory is a fine thing. But practice dictates otherwise, after many years in the 'industry' I can say with certainty that it will make very little to no difference. If you believe otherwise then so be it. I dare say the OP will no doubt post his results.

R
I'll order it, it is advertised as not needed a ground plane, but I assume I can always put the antenna on the tin roof of our patio if a grounded area is needed.

Also, this is not a perfect environment, we do not have spherical cows or perfect vacuums, if there is a little bit of bias in the directionality of my omnidirectional antenna, I'm okay with it. I live in the suburbs, have a budget, and am not relying on this radio for any life-critical use.

I'm happy with minor imperfections.
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Raptor
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Re: External Antenna Advice Needed

Post by Raptor » Sun Feb 08, 2015 1:08 am

rustynswrail wrote:If possible, assuming you mount the aerial on the gutter, drill a small hole under the eaves of the house, route the cable through the wall cavity and bring it out through a blank plate, like those used to blank off power point and light terminations. Saves on plastering. The down side, the cable may not be long enough and you have to cut a hole, fit the gang plate (fits inside the wall cavity to hold the cover in place) and blank cover.

R
I agree with Rusty on his recommendation HOWEVER, before drilling through your eaves or wall, ensure that you are not drilling through asbestos sheeting. If you have a older house, you should assume that the eaves contain asbestos.

If your really want to do it, get a sample of the sheeting tested for a minimal cost.

roland985
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Posts: 190
Joined: Thu Aug 28, 2014 8:23 pm
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Re: External Antenna Advice Needed

Post by roland985 » Sun Feb 08, 2015 8:17 am

This house was partially burned down in 2009. A lot of external materials were replaced. Thanks your your concern though.
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