Scanner antenna

[Rawkee1]

Thanks for all that important info. I was leaning towards the 7/8 wave, but after what you said about Laird B1360WS, it would be much smaller and easier to work with. It will be up about 40'. Do you think the Laird ground plane setup would work as good as the Tram 7/8 side by side?

 

[mmckenna]

Do you think the Laird ground plane setup would work as good as the Tram 7/8 side by side?

The Laird has less gain, so if you are trying to listen to really weak/far off radio systems, the Tram would work a bit better.
However, if you are getting this 40 feet up, the Laird will be lighter, less wind resistance, and easier to install. It'll probably outlast the Tram, also.

Not a fan of the Tram/Browning products.

 

[Ubbe]

Theoretically, a 7/8 wave antenna would have a bit more gain.

A 5/8 or 7/8 both have some 3dB gain but he has tried a Diamond F23 that are three stacked 5/8 with an almost 8dB gain and that didn't turn out well for him. So it's probably not the actual antenna that are the problem.

/Ubbe

 

[Rawkee1]

I agree. The Laird is good quality and being up that high probably the difference would be marginal. I have LMR 240 now and contemplating to bump up to LMR 400 while changing it over. LMR400 is very pricey.

A 5/8 or 7/8 both have some 3dB gain but he has tried a Diamond F23 that are three stacked 5/8 with an almost 8dB gain and that didn't turn out well for him. So it's probably not the actual antenna that are the problem.

/Ubbe

Good point Ubbe! Other than the cable, could it be the Radio Shack Pro2067? The other radio is the bearcat 996 P2. All the railroad stuff is banked in the RS 2067. I should probably try to enter some RR frequencies and see how the Bearcat receives them....

 

[mmckenna]

I agree. The Laird is good quality and being up that high probably the difference would be marginal. I have LMR 240 now and contemplating to bump up to LMR 400 while changing it over. LMR400 is very pricey.

I may have pointed this out earlier,
70 feet of LMR-240 will lose 2.3db at 160MHz. That's about 40% of the received signal that never makes it to your radio. It's just lost in the coax.
70 feet of LMR-400 will lose 1.17db at 160MHz. That's about 24% of the received signal.
While the LMR-400 might cost more, you may see better performance.

Good point Ubbe! Other than the cable, could it be the Radio Shack Pro2067? The other radio is the bearcat 996 P2. All the railroad stuff is banked in the RS 2067. I should probably try to enter some RR frequencies and see how the Bearcat receives them....

Try the NOAA frequencies. They are close enough to the railroad frequencies that it'll be a good comparison. They transmit constantly, so you can try different settings, radios, etc. and compare the results.

It could also be your coax. If it wasn't properly weatherproofed when you installed it, there could be moisture in the cable/connectors. That will severely impact performance.

 

[Ubbe]

The other radio is the bearcat 996 P2.

That's a solid radio with a good receiver. If you have a telescope antenna for it then try and listen to NOAA whit the scanner at a window. Pick out the weakest channel and note the signal strength. Adjust the antennas length for best signal. Then compare with your roof antenna, I guess it's the discone, that should be considerable stronger and some of the NOAA channels where dead with the telescope but should come alive with the roof antenna. If you only hear one NOAA channel then you must be in a bad location. That 40ft height difference should have a major impact on signal strength.

If it's just a moderate improvement, or none at all, then there's some coax or connector problem. That 996P2 shouldn't be affected by any interference.

/Ubbe

 

[Rawkee1]

Ubbe, I have to add one caveat to the scenario. The F23 is mounted low on the mast so the vertical radial rides along side the mast. Could that be deflecting the signal in any way and creating less signal?

 

[mmckenna]

Ubbe, I have to add one caveat to the scenario. The F23 is mounted low on the mast so the vertical radial rides along side the mast. Could that be deflecting the signal in any way and creating less signal?

Yes, absolutely. You have to either have it stood off from the mast or above it.

 

[Rawkee1]

I guess I should relocate the F23 to the top of the mast (about 8' more) and see if it make a noticeable difference.

 

[mmckenna]

I guess I should relocate the F23 to the top of the mast (about 8' more) and see if it make a noticeable difference.

Absolutely. I suspect you'll see a difference.

 

[Ubbe]

Could that be deflecting the signal in any way and creating less signal?

It's very sensitive to any object close to it. It is impossible to measure the antenna when it's laying on the ground and even when resting on two wooden chairs it makes a big impact on the measurements.

When you have a vertical antenna close to a metallic mast it will change the directive lobe in different ways dependent of the distance between the two. 0,25 wavelength at 150MHz are 50cm and 0,5 are 100cm, 1 meter.

/Ubbe

 

[Rawkee1]

Thanks, it looks like my next move is to move the antenna up and see the difference. It's going to be a PITA but hopefully it will be worth while.

 

[Ubbe]

You can have your current installation work to your advantage, if you do not need coverage in certain directions. What you loose in one direction will be added as gain in another direction. Professional installations often install antennas using a 0,25 wavelength distance to the mast to add some gain, especially if there's a building behind that anyhow obstructs the coverage. But going closer than 0,25 will just throw the tuning off and change the impedance of the antenna.

/Ubbe

 

[WRQS621]

I use one of those cheap flat HDTV antennas. Works better than anything else I have tried.

 

[Rawkee1]

You can have your current installation work to your advantage, if you do not need coverage in certain directions. What you loose in one direction will be added as gain in another direction. Professional installations often install antennas using a 0,25 wavelength distance to the mast to add some gain, especially if there's a building behind that anyhow obstructs the coverage. But going closer than 0,25 will just throw the tuning off and change the impedance of the antenna.

/Ubbe

Ubbe, I am thinking of buying a 2 or 3 foot offset bracket to separate the vertical radial from the mast. Should that be a sufficient distance from the mast? It would make my life a lot simpler. KY4OA, what do you use that flat HDTV antenna for? We’re not talking bringing in TV signals.

 

[mmckenna]

Ubbe, I am thinking of buying a 2 or 3 foot offset bracket to separate the vertical radial from the mast. Should that be a sufficient distance from the mast? It would make my life a lot simpler.

It would be sufficient.
If your mast will support the weight of the antenna and the mount hung off to the side like that, then it's an option.

KY4OA, what do you use that flat HDTV antenna for? We’re not talking bringing in TV signals.

Some use them for scanner antennas. They work on 7-800MHz pretty well, and have some performance on UHF. Would likely be directional, and not good for all installations.

 

[Rawkee1]

The mast is heavy gauge galvanized steel. It will definitely support it. It will be interesting to see if the signal improves.

 

[WRQS621]

Ubbe, I am thinking of buying a 2 or 3 foot offset bracket to separate the vertical radial from the mast. Should that be a sufficient distance from the mast? It would make my life a lot simpler. KY4OA, what do you use that flat HDTV antenna for? We’re not talking bringing in TV signals.

I use the antennas for both mobile and base installation. I can go over all the testing I have done, but trust me, for the money you cant beat them. The old saying goes, "any antenna is better than no antenna". Now would I used it for pulling out DX stations, of course not. I use for general local scanning, it works great. I recommend the store brand from Best Buy, look at the spec's and you will see then work well in most scanner bands. They are essentially multiband dipole antennas, remember rabbit ears?

 

[Ubbe]

If your mast will support the weight of the antenna and the mount hung off to the side like that, then it's an option.

The antenna are 5 meters long but only weight 2 kilos and are slim so it has minimal wind drag. I carried mine below the radials in my left hand and listened in a scanner while checking different locations on the roof.

/Ubbe

 

[Rawkee1]

The antenna are 5 meters long but only weight 2 kilos and are slim so it has minimal wind drag. I carried mine below the radials in my left hand and listened in a scanner while checking different locations on the roof.

/Ubbe

Now the other big question is, should you wire tie your coax to the mast? If not, what is the best way to run your coax for less line interference?