Antenna planning for a wideband scanner

[dlwtrunked]

OK. Not sure what they use in the UK, but two antennas could be a mesh network system or cellular.

At one time there were a lot of analog video linking products that used 900MHz, so it was easy to dial them up and see what they saw.



Got it. I do the same thing, occasionally. I've got a remote receiver that will cover from 40KHz to 3.5GHz and it's fun to tune around and see what you can find, even if it's not something you want to listen to. I have a "frequency selective volt meter" designed for testing really old telecom circuits. It'll work as a receiver from 0Hz up to 3.5KHz. With a decent antenna, there's all kinds of weird signals way down in the 30KHz range. Up past 1000MHz, there's some stuff, but mostly wide band data that is using point to point directional links, or is pretty low power.

I can identify all the signals I receive here in the VLF range. If you want to ID something around 30 kHz, let me know the frequency. I got rid of the frequency voltmeter I had when the battery failed--I have good SDR receive capability down to about 1 kHz anyway. For GHz range, I go portable/mobile or use my L-band dish/feed if it is space. By the way. my lowest frequency received was 30 Hz and leakage from the power line from the TWACS device (only would transmit a series of pulses a couple times a day. I had them remove the TWAC receiver they installed on my water heater due to inference from its CPU clock on the local 2-meter repeater (But the pulses on the power line of course remained).

Aclara Demand Response Product Offers More Data, Greater Control

ST. LOUIS – September 8, 2008 – TWACS® (Two-Way Automatic Communication System) technology from Aclaraâ„¢, St. Louis, is known for its ability to perform demand response by controlling...

www.tdworld.com

My highest received frequency (not including when I had direct TV or cell phone stuff) is up close listening to and waterfall displays of 5 GHz airport terminal doppler weather radar in the 5 GHz range. I can go to 12.4 GHz but have not really had time to explore up that range. ( I guess I could test my receive setup using my radar gun.)

 

[MUTNAV]

At around that time our police helicopters where said to use a video link somewhere in the 5GHz band that they had a special permit to use as it was assigned for military use. When the video monitor at the police HQ could be seen in a TV program or news cast I could see that when the signal strength where weak it behaved as an analog signal.

When the helicopters used their video equipment they also sent a datasignal in the 400Mhz band. I guess it was a gps and height info from the heli as there where three receive stations around the city that used directional antennas, and those antennas had to be controlled in some way to point at the helicopter. The datasignal could be heard for maybe 5 years and then it died.

Our police had 4 Bell Huey helicopters for the whole country and they bought 4 new Eurocopters and when they where installed with advanced video equipment and in their test phase they where stored in a hangar where a fire broke out. They only manage to save one helicopter so they had to continue to use their old helis for another 2-3 years until they had gotten their new eurocopters delivered and tested.

/Ubbe

these things exist....

https://www.amazon.com/Wireless-Transmitter-Receiver-Transfer-Casting/dp/B09QS4RQY5?pd_rd_w=4DF6Q&content-id=amzn1.sym.c9b3a448-7c3c-4399-ac60-2bdc98844f72&pf_rd_p=c9b3a448-7c3c-4399-ac60-2bdc98844f72&pf_rd_r=CRYF9CS1XJT7B727T6WA&pd_rd_wg=PbjPI&pd_rd_r=69bd8064-f19f-4dde-8cbe-a7d89f379f6a&ref_=sspa_dk_rhf_detail_pt_sub_0&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExSTBMN0VJNFpaOVJEJmVuY3J5cHRlZElkPUEwNjAyMjU0UEQ2NEZXSkc4SU5ZJmVuY3J5cHRlZEFkSWQ9QTAwMDQzMTAxVlVOVDg5UTQ1VDZZJndpZGdldE5hbWU9c3BfcmhmX2RldGFpbCZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05vdExvZ0NsaWNrPXRydWU&th=1

and I think some security cameras work on the same idea.. There were actually video scanners in the past to look for wireless cameras to see what they see...

Some backup car cameras also can work in this range.

Thanks
Joel

 

[mmckenna]

I can identify all the signals I receive here in the VLF range. If you want to ID something around 30 kHz, let me know the frequency.

At one point I'd identified most of it. It's all well established VLF stuff for sub communications, time signals (WWVB) and the like. Fun to play with, but I haven't had time recently. Original plan was to take it out into BFE and set up a l-o-n-g beverage antenna (along with a c-o-l-d beverage for the operator) and see what I could find.

I got rid of the frequency voltmeter I had when the battery failed--I have good SDR receive capability down to about 1 kHz anyway. For GHz range, I go portable/mobile or use my L-band dish/feed if it is space. By the way. my lowest frequency received was 30 Hz and leakage from the power line from the TWACS device (only would transmit a series of pulses a couple times a day. I had them remove the TWAC receiver they installed on my water heater due to inference from its CPU clock on the local 2-meter repeater (But the pulses on the power line of course remained).

Aclara Demand Response Product Offers More Data, Greater Control

ST. LOUIS – September 8, 2008 – TWACS® (Two-Way Automatic Communication System) technology from Aclaraâ„¢, St. Louis, is known for its ability to perform demand response by controlling...

www.tdworld.com

My highest received frequency (not including when I had direct TV or cell phone stuff) is up close listening to and waterfall displays of 5 GHz airport terminal doppler weather radar in the 5 GHz range. I can go to 12.4 GHz but have not really had time to explore up that range. ( I guess I could test my receive setup using my radar gun.)

As part of a project at work about 10 years back, I installed an AOR AR-2300 with the ARL-2300 network adapter at one of my high sites. I put up a really nice Telewave discone that's good from 100MHz to something 3GHz, and a end fed long wire. It's handy for checking some of my systems without having to drive into work. It's also handy when I have some free time to surf the spectrum. Used to do a lot of NDB's with it. From the west coast I was able to pick up an NDB from Hawaii, which was pretty good considering the crappy antenna. Nailed most of the NDB's up and down the west coast, including quite a few in Canada and Alaska.

Some day I'll get my FSVM out again and play with it. The bandwidth was too narrow for AM broadcast, but it worked well enough. It was a really hot receiver and almost made it too easy to yank in some of the lower power AM stations.

 

[merlin]

In my day, I played with stuf up to 25 Ghz. Waveguide, LNBs and dishes.
While these newer modules do work, there is one thing missing.
Filters, and you can't skimp or get cheapies.
An antenna is a system and you kill it breaking into anything upstream.
Start with discone. Unless you are looking to monitor broadcast, those strong signals
must be notched out and before any amplification. This applies to strong LMR signals as well. LNA: 15 to 20 Db gain is suitable. noise figure must be less than 1 Db.
Feed line should be quality coax. RG-6, LMR124 or better
That system will be good from 100 to 1000 Mhz. that can run to a switch or diplexer.
Now the PCB antenna. Probably fine to monitor bluetooth, WiFi, Wlan within 1 Km
or you will need to mount it to the focal point of a dish. You still need an LNA.
LNB would be better as baseband is much easier to work with. Something good from 2 to 10 Ghz. that system will cover some amateur, WLAN etc. Again, a quality feed line.
Note you are getting into true line of sight here, if you can't see the other antenna with a telescope, you may not get much of a signal
Not much above 10 Ghz some telemetry, Iot relay, and STL up around 25 Ghz.
Some dopler radar in the lot.
Now you can switch systems but before a receiver, you are going to need attenuation.
Perhaps step attenuator in 5 Db steps to -30 Db.
What you receive in the end is up to your receiver or equipment you plug this into.

 

[dlwtrunked]

At one point I'd identified most of it. It's all well established VLF stuff for sub communications, time signals (WWVB) and the like. Fun to play with, but I haven't had time recently. Original plan was to take it out into BFE and set up a l-o-n-g beverage antenna (along with a c-o-l-d beverage for the operator) and see what I could find.



As part of a project at work about 10 years back, I installed an AOR AR-2300 with the ARL-2300 network adapter at one of my high sites. I put up a really nice Telewave discone that's good from 100MHz to something 3GHz, and a end fed long wire. It's handy for checking some of my systems without having to drive into work. It's also handy when I have some free time to surf the spectrum. Used to do a lot of NDB's with it. From the west coast I was able to pick up an NDB from Hawaii, which was pretty good considering the crappy antenna. Nailed most of the NDB's up and down the west coast, including quite a few in Canada and Alaska.

Some day I'll get my FSVM out again and play with it. The bandwidth was too narrow for AM broadcast, but it worked well enough. It was a really hot receiver and almost made it too easy to yank in some of the lower power AM stations.

I have had an AR-2300 for years but have never actually used it even once--I cannot even recall why.

 

[seans1212]

Man, you guys have worked some extreme frequencies with some exotic gear. My best gear was AR5000 +3 and its handheld brother the 8600. The 5000 is a fantastic receiver but living in a flat, I could never set up low freq. antennas but still worked well down to 2Mhz with all kinds of antennas.
Back in early 90s was a long wire that went out of first-floor window and ran on/along the trees for about 30 meters, back then plugged into a sony ICF-2010, as crapy an antenna that was, I was pulling in live Iraq war comms. that radio is an amazing shortwave radio. At one point I had an old marine receiver that weighed 27kg, amazing radio too. Used to surf the spectrum so much and find so many freq. the you shouldn't both on low freq and high, but its not much out there now days so my main monitoring is Air/Mil Air on couple of scanners including an Icom anf Hack RF One for hacking!

@merlin, thanks for the advice, appreciate it. The discone will be delivered in a couple of days. Need to figure out the mounting pole and bracket stuff and the cable will be an RG6, looking for the 3GHz type as I have been converted from going low loss 50 Ohm.
The cable run is most likely just under 50 meters, I am guessing LNA is a must? I have an LNA For All link here:
LNA for all on its I have made an SMD band II (FM radio) notch filter which is very effective. Unfortunately too at the bottom of the Air Band, but I still get the tower 12 miles away. As for the attenuator, I guess it can be set up just before the receiver, so I will make some kind of a step or variable.
I think I may just start with the discone and see how that works as a pure uncluttered setup and see how it is as a reference and then if I come up with a good effective other plans, then I will take it from there, though I would at least would like a 1.090GHz antenna and filter but that may have to wait for now.

@MUTNAV, yes interesting TX/RX, you never know it may be something like that...

 

[seans1212]

By the way the dis one has an N connection. I will be using RG6, have never made an N connection but many BNCs. Google tells me RG6 has a 6.90mm diameter. I can get an N connector:
N Type Male Plug for RG58 RG223 LMR195, Clamp Type Compression Connector | eBay
for the following cables:

• RG58
• RG223
• LMR195
• RG142
• URM76

They all seem to be in the 5mm range. Or I can get an N to BNC adaptor and use BNC. I know N type is supposed to be better especially at higher frequency. Is the any disadvantages of using an adapter type?

 

[seans1212]

Also does it make much of difference if the inner core is solid copper as opposed to copper clad steel? I think I read solid copper was better and has less voltage loss if power is being fed up to an LNA or such.

 

[Ubbe]

Also does it make much of difference if the inner core is solid copper as opposed to copper clad steel? I think I read solid copper was better and has less voltage loss if power is being fed up to an LNA or such.

But do you really need low voltage loss? Usually you feed a LNA with much higher voltage than needed, perhaps 12V, and then stabilize it down to 5V and filter it so there will be no feedback, oscillation or other strange things happening. The pure copper core are better for less voltage drop but there's a huge price different to the steel core with just a thin copper clad for RF purposes.

Good quality adapters are no problem but will always add one more point of failure. I usually buy cheap chinese adapters and test by wiggling them and have to throw away 3 or 4 of them as in a certain angle they attenuate too much.

/Ubbe

 

[mmckenna]

Also does it make much of difference if the inner core is solid copper as opposed to copper clad steel? I think I read solid copper was better and has less voltage loss if power is being fed up to an LNA or such.

It really depends on what you are doing, but I doubt you will exceed the capabilities of a copper clad steel conductor. The copper clad steel will probably be less expensive.

As Ubbe said, you should not have any issues with voltage loss. RF signal loss should not be an issue when comparing the two:

Skin effect - Wikipedia

en.wikipedia.org

 

[seans1212]

Thank you both, understood. My concern wasn't so much voltage drop/loss, I wondered if that equated to loss of RF too but mmckenna just confirmed it doesn't.
And yes it's quite a bit cheaper.
I have some N connector to BNC adapter, they from Farnell, I will give them a try also will put the spacial tape on the whole connector that insulates it completely, can't remember what it's called now.

 

[seans1212]

Hi All,
I just wanted to give helpful folks here who helped with suggestions for my setup earlier this year some updates on my scanner antenna setup.

I have finally installed the Scanking Royal discone antenna on a 3-meter pole bolted on the roof of the 3rd-floor building. The discone has an N connector to an SMA patch cable 4 meters long. this feeds into a waterproof case that is bolted to the wall next to the antenna which contains an RTL SDR FM broadcast band stop filter which comes in a tiny little aluminium case, a very short SMA terminated patch cable feeds the output of the filter to the low noise 0.6dB noise - 17dB gain LNA. the LNA housing is built using double sided PCB and terminated with SMA in/out. Output from LNA is SMA to F adapter which feeds the downlink coax PF100. I am guessing the entire length of the cable to the antenna is about 40 meters max. The LNA power is fed using a Biase Tee currently not in a metal casing yet but it works well, I will fit it into one eventually.

I am in central London under the flight path of Heathrow ILS landing so the strongest signals are the actual plane above me (1800ft) transmitting. The RTLSDR filter literally obliterates the broadcast band, so it works well. I tested 3 other stopband filters but none was as good as this. The others came from ALiexpress with varying claims. Most of the issue was that firstly, they didn't quite get rid of the FM band broadcast properly, but worse was that most also wiped the civil airband which is what I monitor mostly. One of the filters wiped everything from 70MHz to 140MHz! I used a spectrum analyzer with a tracking generator to check the filter responses. The best was the RTLSDR at £23, it just about touched the lower airband making 118.5 & 118.7MHz tower tx somewhat unreliable and at times difficult to hear which is a shame but a small sacrifice.

According to my rough calculations, I lose about 17-18dB in the length of the coax cable which is compensated by the LNA gain of around 17 dB. I only occasionally get LNA overload when a plane is transmitting overhead. Otherwise, the whole system seems to work well, the antenna pulls in signals well throughout the airband and all the way up to 2.5GHz. I did not fit the vertical rod atop the Discone as I heard it degrades the upper-frequency range.

Currently, one radio at a time is connected to the antenna however, I plan a 2 or 3-way splitter, I also have a variable gain LNA which I may use if the splitter degrades the signal too much.

Thank you to all who contributed.

Tested using:
Scanking Royal Discone 2000
RTLSDR FMBB Stop filter
LNA 50-4000MHz SPF5189
PF100 coaxial
HACKRF One
Icom IC-R20
AOR AR8200
Realistic Pro-2006

 

[prcguy]

Also does it make much of difference if the inner core is solid copper as opposed to copper clad steel? I think I read solid copper was better and has less voltage loss if power is being fed up to an LNA or such.

This is true in the satellite industry when powering complex LNBs with accys that can draw 400ma and they recommend solid copper center conductor RG-6 for up to about 200ft runs. For hobby use with an LNA that might draw only 50ma its not a big deal and the RF losses between solid copper and copper clad steel center conductor are basically the same.

 

[seans1212]

Yes, the cable is RG-6 PF100 all copper. Also, the LNA is running at 3.3V with a cable feed of 12V, so, the voltage drop is not an issue.

 

[Ubbe]

the entire length of the cable to the antenna is about 40 meters max.

According to my rough calculations, I lose about 17-18dB in the length of the coax cable which is compensated by the LNA gain of around 17 dB

I took a look at PF100 and it's very similar to RG6. A length of 40 meter PF100 has a 3dB attenuation in VHF and 6dB in the 400Mhz band.
You can use a 1-8 splitter and still have gain to spare. If you use a 1-2 or 1-4 splitter I suggest to open up the splitter and insert a small capacitor in series with its input, something like 2.7pF or 3.3pF, that will produce the same signal level independent of frequency and will also attenuate the signal down to more realistic levels. You can instead insert that capacitor in series with the output to the splitter in the bias-T.
When using external antennas there's always a good idea to use a variable attenuator to really dial in the best sensitivity for a receiver. They cost something like £5 to £10. F Connector Coaxial Cable Variable Attenuator 0 20dB Coax RF Digital TV Freeview 5055538187773 | eBay

/Ubbe

 

[seans1212]

Thanks, Ubbe. My rough calculation was for the 1GHz and above, so you are right at VHF there should be plenty of gain and yes there seems to be. Although, plenty of gain also has the following settings on my device HACKRF - Amp ticked, LNA Gain set to 32dB and VGA Gain set to 10dB. signal peaks in the display in the airband range from -35 to -20, some higher and some lower. I think 32dB LNA setting is too high, but it generates solid strong signals. It also can overload the LNA and cause reflections of stronger signals (intermodulation) strangely enough 121MHz range generates lower strength reflections in the upper 100MHz... also raise the noise floor at the same time create many smaller peaks.

But I am just being a perfectionist, it all sounds good the IM isnt that bad and the suggested attenuator will be very useful.
Your link for the variable attenuator is great and low cost, on my shopping list.

 

[Ubbe]

With that capacitor in series you will EQ the gain so that 1GHz have no attenuation, full gain, and at VHF it will be something like a 10dB attenuation. It will be better suited to compensate for coax attenuation and you can usually set a higher gain up in the GHz range compared to VHF that overloads more easily. For ADS-B I can use a preamps full 15dB gain to a RTL-SDR dongle if I use a SAW 1090MHz bandpass filter to get rid of cellular and TV signals.

/Ubbe

 

[seans1212]

Sounds like a perfect plan. A SAW 1090MHz filter or a complete filter is on my shopping list too.
I have an F-type 2-way splitter used for TV & Sat I tried to use thinking it was resistive, but it's not as I placed it between Ant and the Bias Tee and the LNA wasn't getting any power so internally it must have a cap. Also no continuity between in and out of the splitter when checked with a meter. But, it cannot be opened, it's completely sealed. I need to get some patch coax cable like F to SMA to try to fit it between Rx and Bias Tee and see what I get.

 

[MUTNAV]

With that capacitor in series you will EQ the gain so that 1GHz have no attenuation, full gain, and at VHF it will be something like a 10dB attenuation. It will be better suited to compensate for coax attenuation and you can usually set a higher gain up in the GHz range compared to VHF that overloads more easily. For ADS-B I can use a preamps full 15dB gain to a RTL-SDR dongle if I use a SAW 1090MHz bandpass filter to get rid of cellular and TV signals.

/Ubbe

I think 1090 MHZ is the reply frequency for aircraft interrogations.

Thanks
Joel

 

[Ubbe]

I have an F-type 2-way splitter used for TV & Sat I tried to use thinking it was resistive, but it's not as I placed it between Ant and the Bias Tee and the LNA wasn't getting any power so internally it must have a cap.

That's strange as almost all splitters I've seen has at least one port marked "power pass" or all ports are if none are marked. It's just a small choke coil between ports to pass DC and block RF. CATV splitter are usually a cast metal form where the electronic circuit board are install and then it's sealed by a thin metal plate that can be removed fairly easy by drilling a little hole in it to be used to insert a screwdriver or something to lift the plate.

/Ubbe