Scanner Antennas

Choosing the right antenna is important. But it might be even more important to use the right type of coax to connect your chosen antenna to your scanner. I'd been hearing this advice for years, but never really understood the impact of using the correct coaxial cable until I took the time to actually try different cables with one of my antennas designed for 800Mhz. I had been trying to monitor a particular local (digital) public safety frequency in the 800Mhz range for years without luck, and I had even gone to the length of getting a 7-element Yagi just for this frequency. When even the high-gain antenna didn't work, I just assumed that I was just in a bad location. Then I got up in my attic with that 800Mhz Yagi and a short length of good cable. Presto! 90% successful packet decoding. The same antenna connected to just 25 feet of what was advertised as "micro loss" RG58 good through 900Mhz... 5% successful packet decoding. Same antenna connected to 50 feet of LMR600 (see Time Microwave, manufacturer of LMR series cable), 90% successful packet decoding!

The moral of the story is: Even the best antenna is no good without the right coax.

aka-ramon posted 26 Nov 2005

Using CB antenna whips to create custom VHF Hi/Lo antennas for scanning.

As an long time scannist, and an avid expirimentor with antennas,
here are a few tested and workable suggestions. 
THESE ARE NOT FOR BROADCASTING ON VHF LO OR HI BAND< ONLY RECEIVING!!!

A: VHF Lo Band mag mount- Take a Radio Shack mag mount and firstly remove the entire whip/element from the base using the supplied allen wrench. Find an steel CB whip and "prune" it to approximately 40 to 42 inches in length. Inset it into the base and tighten with the allen wrench. In my experience this will give you an near perfect Lo Band scanner antenna. Personally I was able receive Lo Band base stations at distances of nearly 100 miles with NO skip, and mobiles from 15 to 20 miles with NO skip.

Of course the ultimate VHF Lo Band suggestion is to acquire an actual retired Lo Band antenna from an lea/leo. Full Ball mounted steel CB antennas also work great if you use a coax plug BNC adaptor and make sure your connection is clean and tight.

B: VHF Hi Band mag mount- As before use an RS mag mount base with elements/whips removed. Take a steel CB whip, and "prune" to approximately 28 to 32 inches in length, and insert it into the base. Personally I have received Hi band base stations from nearly 70 to 80 miles with NO ducting, and mobiles from nearly 20 to 25 miles with NO ducting, and mobile repeaters/vehicular extenders from nearly 15 to 18 miles with NO ducting.

And as before if you can acquire an actual Hi Band antenna try to do so for perfect reception.

These work for mobile use, and as a base station antenna if you have a good metallic surface to mount the mag base on like say an elevated AC box, or tin roof, or even a rain gutter.

As far as making a pole/mast mounted rig- Use a steel whip if possible, though any high quality CB antenna will work. Add an BNC adaptor and be sure your connection is clean and tight. Plug in, scan, enjoy.

Doing modifications on the Radio Shack mag mount for UHF Lo/UHF Hi.

The following are a couple of modifications to RS mm scanner ants for specific band reception in UHF, and 700/800/900 MHz.

Simple mod- Using the supplied allen wrench, remove the second coil element, and place the top whip element into the first coil and tighten appropriately. This works very good on both UHF, and 700/800/900 MHz.

Simple mod 2- Remove ALL elements. Take a CB steel whip and "prune" to 16 to 18 inches. Insert this into the base and tighten appropriately. Use on vehicle rooftop. Works great on VHF Hi for stronger signals, UHF for medium to strong signals, and excellent on 700/800/900 MHz. For 700/800/900 MHz only, "prune" to 10 to 12 inches.

Or if you have access to actual center coil UHF, UHF/VHF, or 800/900 MHz whip elements, use these in the mm base.

To prevent water leakage into the base assembly if your whip elements are smaller than available openings, install a small rubber seal in the orifice.