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SDR and Computer app to measure Antenna Signal Strength and SWR??

humblegeo

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#1
Has anyone ever used an SDR and some sort of computer app that would allow a person to measure indoor antenna signal strength at a particular frequency like (774.00 mhz)? A Radio Scanner Frequency I try to listen to quite often, a control channel frequency with talkgroup TGIDs on a site or tower near me., Allowing a person to move the antenna around the room and help locate the hot spot or best location in the room for highest signal strength at that particular frequency. I don't trust the rinky dink signal strength meter on the radio. I know there is the program for aircraft frequency that can give out a signal strength meter reading at that specific aircraft frequency of 1090 mhz. I have used that one before, just wondering if there are other type programs similar to that one for measuring antenna strength at other frequencies.

Also I have a SWR meter that I use when tuning a CB Radio Antenna length trying to achieve the lowest SWR reading. Can the simple SWR meter be useful if put in series with the Scanner Radio external indoor antenna?

Newbee trying to improve indoor Police Scanner reception on P25 Phase 2 Simulcast weak signal situation. I have a 1/4 ground plane antenna cut to proper calculated length and I also have used a small Tram multi frequency mag mount antenna mounted to a 16" metal pizza pan that works pretty good too but never quite satisfied with the reception. I feel like some sort of a signal strength meter would be very useful moving forward to help fine tune and tweek location of antenna indoors.
 
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#4
Has anyone ever used an SDR and some sort of computer app that would allow a person to measure indoor antenna signal strength at a particular frequency like (774.00 mhz)?
Yes.

So, do you have an SDR? Which one?

Also I have a SWR meter that I use when tuning a CB Radio Antenna length trying to achieve the lowest SWR reading. Can the simple SWR meter be useful if put in series with the Scanner Radio external indoor antenna?
I don't see how. It's not designed for 700 MHz, is it? And it's supposed to be used in conjunction with a transmitter, no?

Newbee trying to improve indoor Police Scanner reception on P25 Phase 2 Simulcast weak signal situation. I have a 1/4 ground plane antenna cut to proper calculated length and I also have used a small Tram multi frequency mag mount antenna mounted to a 16" metal pizza pan that works pretty good too but never quite satisfied with the reception. I feel like some sort of a signal strength meter would be very useful moving forward to help fine tune and tweek location of antenna indoors.
It would be very useful.

Keep in mind signal quality will probably be more important that signal strength.
I suspect that they will go hand in hand for the OP.
 
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#5
HDSDR can give a pretty good indication of signal strength it has a meter, I use it to find the sweet spots where my indoor basement location antenna works best.
 
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#6
What I have which has proved itself quite useful is a TV field strength meter. Lots of them becoming redundant now that we have digital TV and you either get that or you don't - there's no tweaking of the antenna for max smoke. I think I paid about US$25 for this one which will run on batteries - tunes from 45MHz right up to 860MHz.

960599615.jpg
 
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#7
Keep in mind signal quality will probably be more important that signal strength.
Yes, signal/noise ratio are the one to measure and not the signal strenght of interferencies. Use SDR# in windows and you can use a laptop with the antenna on the SDR receiver and walk around while having the mouse pointer over the signal in the bandscope to read SNR.

/Ubbe
 

humblegeo

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#8
Yes.

So, do you have an SDR? Which one?


I don't see how. It's not designed for 700 MHz, is it? And it's supposed to be used in conjunction with a transmitter, no?


It would be very useful.


I suspect that they will go hand in hand for the OP.
I do have a sdr from years ago DVB-T+FM+DAB 820T2 that probably sill works. Maybe I could use it?
 

humblegeo

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What I have which has proved itself quite useful is a TV field strength meter. Lots of them becoming redundant now that we have digital TV and you either get that or you don't - there's no tweaking of the antenna for max smoke. I think I paid about US$25 for this one which will run on batteries - tunes from 45MHz right up to 860MHz.

View attachment 68531
That's a very old meter from what I can find out and I don't know if I could find one or not, maybe on ebay. will it do what I'm trying to do an find the sweet spot in the room for antenna location? 700-800mhz
 

humblegeo

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#11
Yes, signal/noise ratio are the one to measure and not the signal strenght of interferencies. Use SDR# in windows and you can use a laptop with the antenna on the SDR receiver and walk around while having the mouse pointer over the signal in the bandscope to read SNR.

/Ubbe
Do you recommend osmocom_fft utility or HDSDR or something else?
 

humblegeo

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#13
Whatever you have installed...
For me that would be osmocom_fft or op25 fft plot.
What I have installed is SDRSharp that is working and I have played around with it some just looking at signals but never tried to use it to zero in on best location in room specifically for 774.00 mhz signals or for that matter, which antenna works best. So looks like I can get a Peak, Floor and SNR reading from it.
 
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humblegeo

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#15
Ok next question SNR reading with SDRSharp. Signal to Noise ratio. The higher the reading the better...right? Is there another reading I should be looking at besides SNR?

Appreciate all the help and suggestions.
Larry G
 
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humblegeo

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#18
With Windows and sdr#, I use this plugin to find sweet spots.. And since my antenna is on the other side of the room, I set windows magnifier to zoom the meter so I can see it while adjusting my antennas..

LevelMeter: New SDR# Plugin[/QUOTE Ok, I've added LevelMeter Plugin to SDSharp and have it up and running. Looking at Peak Power VFO. Starts out as an example: meter fluctuating between S9+3 to S9+6 about -61 dB reading then there is a transmission at the control channel frequency of 774.15625 mhz meter continues to fluctuating between S9+3 to S9+6 but dB reading changes to -30 dB. The meter range is left to right -140 to 0 dB. Am I looking for the lowest reading possible on the meter towards 0 dB for the strongest signal during transmission? In other words -30 dB is a stronger signal than -61 dB.
 
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humblegeo

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#20
I don't know, good tools for comparing two different antenna SNR and Peak Power FVO dB readings but still seems like the antenna with the weaker signal preforms better on the simulcast tower I'm looking at and that may just be the nature of the beast on simulcast. I can't make heads or tails on any of it so it's back to trial and error to just see what works best. I thought there might be a scientific way to measure but seems like the little bit of difference in readings isn't enough to work with to come to any solid conclusion one way or the other.
 
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