I am thinking of setting up a listening station for my neighboring county's P25 trunked system. With a traditional, vertical whip, it is a very "iffy" signal. This got me thinking of another type of antenna to use. As I was just messing around with a weBoost cellular booster, the idea of the directional log-periodic/yagi antenna came to mind. I was looking at the details on the the Wilson Electronic's website and see that it is supposed to cover 814-960 MHz. The frequencies I will be monitoring are between 851-854 MHz, which is inside that frequency range. My thought is that if this antenna would work, I could try to point it in the general direction of the site tower nearest me, which is only about 5.5 miles away at a bearing of 201°. My receiver is an Airspy R2. I plan on connecting this to a Linux-based computer running SDRSharp. I am also curious if this antenna would be a viable option, should I go with a 50-ohm or 75-ohm model. When it comes to two-way communications, it would generally be 50-ohm but it seems as if I've seen 75-ohms being used quite a bit for receive-only purposes. 75-ohm would also make it easier because I already have several hundreds of feet of good quality, quad-shielded RG-6 and compression F-connectors. I see relatively inexpensive F -> SMA connectors on Amazon.
Directional Log-Periodic/Yagi cellular antenna for listening to 851-854 MHz trunked radio
- Thread starter bigRoN18
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mmckenna
I ♥ Ø
The Wilson Log Periodic will work. A frequency specific Yagi will work better.
Question is, how much do you need? If the LP antenna is 'good enough' and you already have it, then it's a perfect solution.
If you don't already own the LP antenna, or it's not sufficient to give you a solid signal, a Yagi antenna specific to the 851-854 slice of spectrum will work better. More gain + more directivity = more signal into your radio.
My experience with Wilson products, especially their antennas, is that they are not super high quality. Might be perfect for what you are doing, but if you experience issues, or the antenna stops performing as well after a few years of use, replace it.
The ever so slight degradation that you might see from using 75Ω cable versus 50Ω cable probably isn't worth the cost of going out and buying new cable, connectors, etc. If you already own the RG6 and have all the parts you need, give it a try, you'll probably find it works just fine.
Question is, how much do you need? If the LP antenna is 'good enough' and you already have it, then it's a perfect solution.
If you don't already own the LP antenna, or it's not sufficient to give you a solid signal, a Yagi antenna specific to the 851-854 slice of spectrum will work better. More gain + more directivity = more signal into your radio.
My experience with Wilson products, especially their antennas, is that they are not super high quality. Might be perfect for what you are doing, but if you experience issues, or the antenna stops performing as well after a few years of use, replace it.
The ever so slight degradation that you might see from using 75Ω cable versus 50Ω cable probably isn't worth the cost of going out and buying new cable, connectors, etc. If you already own the RG6 and have all the parts you need, give it a try, you'll probably find it works just fine.
5 miles is not that far. You could probably use a much cheaper antenna and get the same results. One of the extendable whips would work just as OK.
Ubbe
Member
It's a 7dBi gain, that's not much for $90. You have more gain in a $20 yagi that can be found on Amazon. There's people here on RR that have bought a model that works fine but other models not so much. Do a search in the forum to get the working one.
/Ubbe
mmckenna
I ♥ Ø
Yeah, $90 for any Wilson antenna is overpriced.
Here's a nice Laird antenna for $56.00 https://www.theantennafarm.com/cata...fo&cPath=191_193_258_977_979&products_id=9151
Here's a nice EM Wave with more gain for $60. https://www.theantennafarm.com/cata...fo&cPath=191_193_258_977_979&products_id=9299
Here's a nice Laird antenna for $56.00 https://www.theantennafarm.com/cata...fo&cPath=191_193_258_977_979&products_id=9151
Here's a nice EM Wave with more gain for $60. https://www.theantennafarm.com/cata...fo&cPath=191_193_258_977_979&products_id=9299
Buy a couple lengths of copper tubing at home depot and some cheap pvc, for like less than 20 dollars you can have yourself a 12 element yagi that resonates at your intended frequency. Or you can make it tiny to fit your space with only a few elements. Or you can make it out of wire and make a roll up yagi to hang. You get the idea. Customize it. Plus it's a fun project. Radio is a DIY hobby, don't pay someone else to have your fun for you.
lwvmobile
DSD-FME
I took a Radio Shack/Remtronix 800Mhz BNC whip antenna I already had from many years ago, sheathed it in some 1/2 inch PVC pipe with end cap fittings and pipe straps and secured it to the overhang/fascia/whatever of the roof, bought some BNC male and female to F type adapters (ebay) and used the RG-6 cable and twist on F-type connectors I already had and ran it into my dongles to a BNC to double MCX bulkhead adapter. Total of all my hardware was $15ish (not counting the value of the RG-6 cable, antenna, and other little do-dads) and I can receive P25, EDACS, and other signals in the 850Mhz range from 20 miles or so out in various directions during normal conditions and much MUCH further out when the bands open up. I also did the same with a cheap Nagoya wide band whip and have it feeding into two more dongles and it does pretty okay for 150 Mhz and there abouts, but not so good for 450-460 Mhz.
Overall, I'd say that doing this has increased my signal and reduced the noise compared to using the outdoor TV antenna and amplifier setup I had in place prior.
Word of warning though, or maybe its just me, I don't recommend running an amplifier system (yagi might be okay, i don't know) I've had amplification kill a couple dongles of mine over the past year or so, so no more amplifier for me. I Probably shouldn't have used a TV antenna amplifier I bought at a thrift store to begin with.
Overall, I'd say that doing this has increased my signal and reduced the noise compared to using the outdoor TV antenna and amplifier setup I had in place prior.
Word of warning though, or maybe its just me, I don't recommend running an amplifier system (yagi might be okay, i don't know) I've had amplification kill a couple dongles of mine over the past year or so, so no more amplifier for me. I Probably shouldn't have used a TV antenna amplifier I bought at a thrift store to begin with.
I'd run a nooelec LNA any day. When it comes to LNAs and filters I'll go with nooelec any day, I have several. I also learned to build my own low pass and high pass filters though. That's super cool and probably the easiest electronics project I've had since soddering 2 wires together.
Since the idea of making my own Yagi has come about, I've been researching. I was looking at K7MEM's website about designing yagis. I was thinking of possibly using some 1/2" Schedule 80 PVC pipe for the boom and 1/8" silicon bronze TIG welding rod for elements. I'm trying to figure out how to do the driven element. It appears as if I could go with a folded dipole, which would make for an approximately 300-Ohm feed point. This would allow for an "old" TV transformer, a 4:1 balun, to connect an RG6 coax with an F-connector on it. The information is a bit overwhelming. With the frequencies involved, it looks as if the tolerances are fairly tight. It mentioned element lengths have a tolerance of 1.1 mm, which is pretty tight. I am also not quite sure what the bandwidth of such an antenna would be. Any ideas to help with it?
I bought a Wilson 301111 700-960 MHz 8-element yagi 13 dBi gain $52 on Amazon.
Just to test connectors I hooked it up in the basement and it worked! Suspended it from the rafters, aimed it out a window at a single tower P25 P1 system, eight miles away with 25 feet of LMR240 feeding RTL-SDR dongles. I am impressed.
Also bought the EM Wave EM-B11809 Yagi, 9.5dBi, 6 Element, 760-870 MHz $60 The Antenna Farm.
Suspended them together so I could switch the N-Connector. The Wilson for the win!
YMMV.
Just to test connectors I hooked it up in the basement and it worked! Suspended it from the rafters, aimed it out a window at a single tower P25 P1 system, eight miles away with 25 feet of LMR240 feeding RTL-SDR dongles. I am impressed.
Also bought the EM Wave EM-B11809 Yagi, 9.5dBi, 6 Element, 760-870 MHz $60 The Antenna Farm.
Suspended them together so I could switch the N-Connector. The Wilson for the win!
YMMV.
mmckenna
I ♥ Ø
It's not difficult to make your own antennas that work pretty well. I've made VHF and UHF Yagi's in the past with good results.
The tolerances do get tighter as you go up in frequency, but don't let that discourage you. Do the best you can with the resources available, it's probably going to work just fine for receiving use.
Bandwidth on something like that will easily give you the 800MHz repeater output segment of the band without trouble, and it will likely work pretty well on 700MHz.
If you are planning on doing any soldering of the coax to the driven element, you may have an easier time with copper tubing. It'll solder a lot easier.
CanesFan95
Active Member
I once had a Wilson antenna and it was deaf. I shipped it back.
Which model #?
Ubbe
Member
A UHF TV antenna can be used as a base and then modify that by moving the elements to the correct positions on the boom and cut their lengths. Try to find an antenna that seems to be easy to move the elements and look for the dipole to be 1/2 wavelength at 800MHz, they are usually longer and a folded dipole could be tricky to shorten. The cellular antennas would then be easier to use and most of them already have the proper frequency range, but get a proven and tested one as some seems to be more or less fakes, advertised as HD picture long range.
/Ubbe
CanesFan95
Active Member
301111
As far as tolerance, 1.1 mm seemed a little extreme to me, so...
This source says a folded dipole has about 6.6% bandwidth (-3dB). At 852.5 MHz, the total length of the double-half-wave driven element is 351.9 mm.
If you make the element 353.0 mm instead, it moves the center freq to 849.9 MHz, a change of only 2.6 MHz out of the 56 MHz bandwidth.
Looking at it another way, if the element is 341.3 mm long, the center freq is 879.0 MHz, with the -3 dB lower point being at 851.0 MHz. If the element is 363.2 mm, the center freq is 826.0 MHz and the -3 dB upper point is 854.0 MHz. This makes the tolerance +/- 11 mm (1.1 cm).
This source says a folded dipole has about 6.6% bandwidth (-3dB). At 852.5 MHz, the total length of the double-half-wave driven element is 351.9 mm.
If you make the element 353.0 mm instead, it moves the center freq to 849.9 MHz, a change of only 2.6 MHz out of the 56 MHz bandwidth.
Looking at it another way, if the element is 341.3 mm long, the center freq is 879.0 MHz, with the -3 dB lower point being at 851.0 MHz. If the element is 363.2 mm, the center freq is 826.0 MHz and the -3 dB upper point is 854.0 MHz. This makes the tolerance +/- 11 mm (1.1 cm).
The nice thing about the tolerances going up with frequency is that by the time you get to 800 Mhz, there is the possibility of using a cardboard box covered with aluminum foil on three sides as a corner reflector, and getting good gain and directivity.
Thanks
Joel
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