Hey all, recently I’ve been really digging into SDR and am having a lot of fun with it. That said, I’ve finally figured out trunking and am able to pick it up and decode, but the nearest system is almost all encrypted. The city closest to me that actually has anything on their trunking system is about 20 or 25 miles away. Is there any way to get an antenna that can pick up their signal? I was looking at making a yagi and trying that, but am getting some conflicting information. Thanks so much!
I’m still foggy with antennas and would love some help!
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Yagi is directional and pretty much band specific. What conflicting info did you get?
Get an outdoor antenna, preferably a directional yagi as suggested by Dave and point it in the direction of the closest tower to you. Not everyone's situation is the same (RF environment, elevation, topography, etc) so there's no clear cut answer on whether or not you'll acquire a signal, particularly on 700 & 800mhz (you didn't specifiy band) which traditionally doesn't propagate as far as VHF & UHF. You'll never know until you experiment. Welcome to the RR forums!
Well, My scanner picks up sites 30 miles away with that cheap telescoping antenna right here on the desk.
SDRs are cool, and work, but they are different hardware.
That $30 dongle has no filtering or preamplification in the front end.
They were designed for TV tuners and very broadband. (70 to 1000 Mhz)
What selectivity there is, is the IF stage and it is over 6 Mhz wide.
The solution is a preselector which covers the band you want.
A bandpass filter followed with a low noise preamp and attenuator.
(Most scanners come with something like that)
VHF and UHF antenna 101: you are talking line of sight so range is proportional
to antenna height.
The antenna can be broadband, (TV antenna- discone-etc.) OR they can be band specific
(Omnidirectional-groundplane-mobile whip-etc.)
They can be directional and provide some gain such as the Yagi or array.
Feeding the antenna. Most common is coax but all are not made equal.
Cheap is cable TV coax like RG-6. under 75 foot, it works great.
RG-58 about the same.
LMR-214 has less loss but starts getting pricy
LMR-400, RG-8, RG-213 the bigger stuff, has even less loss even 100 foot, but gets quite expensive with connectors.
ALL of the above works as a system like a chain, no better than the weakest link.
Hope this is enlightening.
SDRs are cool, and work, but they are different hardware.
That $30 dongle has no filtering or preamplification in the front end.
They were designed for TV tuners and very broadband. (70 to 1000 Mhz)
What selectivity there is, is the IF stage and it is over 6 Mhz wide.
The solution is a preselector which covers the band you want.
A bandpass filter followed with a low noise preamp and attenuator.
(Most scanners come with something like that)
VHF and UHF antenna 101: you are talking line of sight so range is proportional
to antenna height.
The antenna can be broadband, (TV antenna- discone-etc.) OR they can be band specific
(Omnidirectional-groundplane-mobile whip-etc.)
They can be directional and provide some gain such as the Yagi or array.
Feeding the antenna. Most common is coax but all are not made equal.
Cheap is cable TV coax like RG-6. under 75 foot, it works great.
RG-58 about the same.
LMR-214 has less loss but starts getting pricy
LMR-400, RG-8, RG-213 the bigger stuff, has even less loss even 100 foot, but gets quite expensive with connectors.
ALL of the above works as a system like a chain, no better than the weakest link.
Hope this is enlightening.
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Straight line distance is only one consideration, but radio waves are also affected by terrain and specific frequencies. Twenty five miles over flat ground isn't a major challenge, but throw in some hills between you and the transmitter makes the equation more difficult.
A Yagi antenna up high enough and good quality feedline is a reasonable solution, but I'd advise buying a pre-built model rather than building your own.
One can certainly make a Yagi, but sourcing the materials , construction and tuning methods may make this option not worth the trouble, especially for a new user.
Essentially no agreeing source of the range you can get from certain antenna types.
Simple comparison. Have signals all around you and fairly strong. Discone covers the bill. Gets rf in all directions but no gain.
Like a fisheye lens for a camera. Lie on your back and look at the sky. If the sun is the brightest thing there, you see it the best.
Yagi. Pulls in a limited frequency range if frequencies in one general direction. More elements (directors) in front, more gain.
Like a telephoto lens, or rifle scope. Aim it at what you want to concentrate on and focus. Narrow field of view. Don't aim it at the sun and you don't see it.
Log periodic. Directional but wide frequency range. Not as sensitive as a yagi in general. But not too bad.
Sort of like a zoom lens that you can point at a squirrel in a tree. Stop it down (close the iris, or f stop) a bit and you can see the butterfly in front and the flower in back of the squirrel. Kind of...
Like a fisheye lens for a camera. Lie on your back and look at the sky. If the sun is the brightest thing there, you see it the best.
Yagi. Pulls in a limited frequency range if frequencies in one general direction. More elements (directors) in front, more gain.
Like a telephoto lens, or rifle scope. Aim it at what you want to concentrate on and focus. Narrow field of view. Don't aim it at the sun and you don't see it.
Log periodic. Directional but wide frequency range. Not as sensitive as a yagi in general. But not too bad.
Sort of like a zoom lens that you can point at a squirrel in a tree. Stop it down (close the iris, or f stop) a bit and you can see the butterfly in front and the flower in back of the squirrel. Kind of...
Very, thank you!
25 miles isn't that far, Most business repeater sites are located on tall buildings or towers. This gives them pretty good range. With no major hills between you... A simple vertical antenna on your roof should do fine.
I live in a bedroom community 30 miles from a large city. I can hear a lot of land mobile traffic in my car just using a simple antenna on the roof. I can also access several amateur repeaters 30+ miles away from the car as well.
I live in a bedroom community 30 miles from a large city. I can hear a lot of land mobile traffic in my car just using a simple antenna on the roof. I can also access several amateur repeaters 30+ miles away from the car as well.
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