Posted: 10/20/2011 5:20:26 PM EDT
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For now our local PD/fire is still analogue so a RS Pro2021 is still meeting my scanning needs. DPS, the county and the two major cities in the county are all digital and I know this will all be digital soon. What is the best antenna that will pick up both or DIY plans for one I can cobble together. |
| I would think any wideband scanner antenna would be fine regardless of analog or digital. IIRC the digital systems are in the 800-900 mhz band so any antenna capable of recieving there would be GTG. Rat-Shak has a simple "multiband" antenna for about $20 or you could copy it using a CB mirror mount bracket and stiff copper wire. |
| I have the AntennaCraft ST2 and it works really well picking up whatever I want about 20' up |
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If for PD and FD in the 151-156 mhz range, any 2 meter antenna trimmed slightly will do.
There are many plans here: Reduce size by a ratio of 146/153, or 95% of the 2m size. http://www.hamuniverse.com/2mtrcheap.html Use 146/153 x 19" = 18.13" (18-1/8") http://www.hamuniverse.com/2metergp.html Use 146/153 x 19.31" = 18.42" (roughly 18-7/16") for "A" and 146/153 x 20.19" = 19.266" (19-1/4") There is an article in this month's QST, I think p.63, showing better construction of this antenna using parts from a barrier strip. But whatever, don't solder the radials to the socket. You can use 1/16" brazing wire, bend the ends into small loops, and attach to the socket with 4-40 screws and nuts. Check out the other 2 meter antennas, scale them down a bit as per above. A friend uses the ground plane design above reduced in size for 161 mhz to use with his scanner to listen to train communications. |
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As you may or may not know, analog or digital makes no difference at all when it comes to antennas.
If they change frequencies when they change modulation, then the antenna needs would change. The easy option for a multiband scanner if you don't need high performance would be a discone. A discone would give you similar performance to a simple 1/4 wave vertical, but it does that over a roughly 10 to 1 frequency range - so a single antenna would be effective from the VHF aviation band to all the way past the 900MHz SMR band. Electrically a discone is very simple, it's just the mechanical construction that is involved for the larger size/lower frequency versions. If you're handy though you could probably come up with a simple homebrew build. |
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Going trunked on a decent sized system, pretty much means moving up in frequency because the new system must be tested in parallel with the old. However, going digital is easily done on a channel by channel basis, and they may keep their same radios, or move from VHF to 450 MHz. Generally cities, large counties and regional systems always go trunked for economies of scale. Stand alone agencies may go digital if they aren't so big as to have all of the talk groups that a large agency wants.
Trunking can be analog or digital, and even a trunked system often has simplex frequencies loaded on individual radios. In rural areas, it's possable to assemble a small trunked system on 450 Mhz out of new space, and it may get easer due to narrow banding and more agencies going to 800 Mhz With the narrow banding mandate, lots of agencies that wouldn't otherwise change, are forced to consider new options. And users that do change, sometimes change back, or change a second time. I'd be really surprised, Rx only, if you could tell the difference at the speaker between a ham and commercial band antenna. If you need 900 Mhz, that might warrant a dedicated scanner antenna. Like Gamma7.62 said discones will work OK. I've had decent luck on Rx and they are as good as any military broadband antenna, but don't preform as well as a tuned 1/4 wave. Shoot, a 1/4 wave 2m whip might be the ticket. In most areas the radio systems are designed for hand held coverage. |
