Locating Transmitters Indoor Wide Range

[bergerb]

I am currently trying to desperately find information on how to locate different types of transmitters.
Two Topics I already found: Fox Hunting and Radio Interference Hunting.

Both are somewhat what I was looking for, but not exactly..

Fox Hunting looks like it is on a fixed frequency, so cheap Yagi antennas are working nicely.
Radio Interference Hunting looks like specialized very expensive equipment..

I am looking for something in between those two extremes.

I would like to locate 433MHz devices, but also eg. 2,4/5GHz Wifi.
What would be optimal - a directional antenna that covers the whole hackrf-range (1MHz-6GHz) but I guess thats wishful thinking
So I was thinking Log Periodic Antenna? And here also again the problem - price

Any recommendations? I would like to spend a max of 200.

But - is such a big antenna even necessary for indoor use?
Or is that even too much, and a cheap PCB LPDA could suffice?

 

[ScannerSK]

Some 433 MHz signals (such as tire pressure monitors) are fleeting, brief signals which could make locating them a real challenge. For WiFi, I would simply use a phone app that reveals signal strength which would allow a person to walk to the location of the transmission.

Others on this group will have a lot more input as to type of gear and pricing. Sometimes inexpensive Ramsey DDF1 kits appear on ebay which use audio from a receiver tuned to any desired frequency to determine location.

 

[prcguy]

A small loop antenna is better at close range. It can have useable null of just a few degrees where a Yagi or log periodic can have a 45 to 60deg beam width. The loop will not be as sensitive so they are not as good at longer ranges.

 

[bergerb]

Got the idea because we have a wireless switch (433MHz) somewhere hidden in an appartment, I know, I know, it probably won't SEND anything, but I imagine eg. Shelly or Sonoff devices could be found that way (Wifi Switch)

DDF1, alright thanks, is on the List

Small Loop Antenna - do you mean just a wire formed into a loop connecting the two ends to the coax cable? Or something fancy looking with that extra loop and some adjustable capacitors? (Sorry for the lingu, but I don't know that much about antennas, I know what a Dipole is, but thats it )
I guess I would need different size Antennas for different frequencies? Or is that not too important for receiving?
Could you recommend anything to read more about different antenna types?

 

[ScannerSK]

DDF1, alright thanks, is on the List

For indoors, a loop would be better. The DDF1 actually mounts on the roof of a vehicle.

 

[dlwtrunked]

I am currently trying to desperately find information on how to locate different types of transmitters.
Two Topics I already found: Fox Hunting and Radio Interference Hunting.

Both are somewhat what I was looking for, but not exactly..

Fox Hunting looks like it is on a fixed frequency, so cheap Yagi antennas are working nicely.
Radio Interference Hunting looks like specialized very expensive equipment..

I am looking for something in between those two extremes.

I would like to locate 433MHz devices, but also eg. 2,4/5GHz Wifi.
What would be optimal - a directional antenna that covers the whole hackrf-range (1MHz-6GHz) but I guess thats wishful thinking
So I was thinking Log Periodic Antenna? And here also again the problem - price

Any recommendations? I would like to spend a max of 200.

But - is such a big antenna even necessary for indoor use?
Or is that even too much, and a cheap PCB LPDA could suffice?

Also consider Vivaldi antennas like these:

TSA900 Ultra Wide band UWB Antenna 900 MHz - 12 GHz for UWB TX/RX SDR RADAR G... | eBay

TSA900 Ultra Wide band UWB Antenna 900 MHz - 12 GHz for UWB TX/RX SDR RADAR GPR SIGINT EMC TEST ADSB WIFI FVP DRONE VIDEO VIVALDI ANTENNA. Radio communications LTE,WIMAX,WIFI,PCS,UWB,GSM,HDTV,IoT. ADS-B reception at 1090 and 978 MHz.

www.ebay.com

High Gain Directional Antenna 1.4—10.5GHz UWB Linearly Polarized Antenna 7dBi | eBay

Rated Gain: 7dBi. Item Type:Directional Antenna. Feature: 1. The working frequency of the antenna is between 1.4~10.5Ghz. Light weight and small size make the antenna can be mounted easily. Power Capacity: 10W.

www.ebay.com

I installed these in a plactic clip board similar to these:

https://www.staples.com/Staples-Portable-Storage-Clipboard-Gray-9-1-2-x-12-Each-Pack-15786/product_741144

- Office Depot

www.officedepot.com

I removed the the metal parts including the clip and added connector to the outside. You could also put the cheap log periodics on eBay also in these.

(Loops above 1 GHz are problematical.)

 

[iMONITOR]

Lots of choices here:

log periodic antenna for sale | eBay

Get the best deals for log periodic antenna at eBay.com. We have a great online selection at the lowest prices with Fast & Free shipping on many items!

www.ebay.com

 

[PA8W]

The DDF1 -like any other pseudo doppler system- needs to have the tracked signal cleanly within its FM bandwidth to make any sense of it.
That works fine for stable, narrow band communication signals but not at all for Wifi.
Also, the 433MHz transmission are generally quite short and quite unstable in frequency, which makes them hard to track with a doppler system.
An automatic Amplitude system (somewhat like a doppler but now comparing amplitudes instead of phase) is much more tolerant fo frequency mismatches and therefore more practical on 433MHz.
And of course there's always the possibility to use a simple directional antenna and search by hand...

 

[G7RUX]

I am currently trying to desperately find information on how to locate different types of transmitters.
Two Topics I already found: Fox Hunting and Radio Interference Hunting.

Both are somewhat what I was looking for, but not exactly..

Fox Hunting looks like it is on a fixed frequency, so cheap Yagi antennas are working nicely.
Radio Interference Hunting looks like specialized very expensive equipment..

I am looking for something in between those two extremes.

I would like to locate 433MHz devices, but also eg. 2,4/5GHz Wifi.
What would be optimal - a directional antenna that covers the whole hackrf-range (1MHz-6GHz) but I guess thats wishful thinking
So I was thinking Log Periodic Antenna? And here also again the problem - price

Any recommendations? I would like to spend a max of 200.

But - is such a big antenna even necessary for indoor use?
Or is that even too much, and a cheap PCB LPDA could suffice?

Well, although these are different in effect the methods are very similar.

If you are looking for a specific frequency then use a directional antenna for that frequency...foxhunts using TDOA switching units are very effective and the actual frequency band of the antenna isn't so critical when you are close by.

For EMI/interference hunting you will need an antenna which can cover a much wider range of frequencies, possibly several. In this case you are almost always quite close to the source so coupling is more important than directionality of the antenna, although directional antennas can be very useful to determine the area to look in. For this I would suggest a set of cheap wideband (low directivity/sensitivity) antennas like Vivaldis or LPDAs, although these get quite large at low frequencies...however, as I mentioned, the raw performance of the antenna isn't actually that important and a coupling loop can be more useful in circumstances when you are wafting around units to see if they are generating the noise.

Another unit that can be useful is a LISN so you can couple in to cables, typically mains cables, and see if there is a signal carried on that cable. Crude versions of these can be made quite cheaply and would suffice for your purposes I would imagine.

 

[dlwtrunked]

The DDF1 -like any other pseudo doppler system- needs to have the tracked signal cleanly within its FM bandwidth to make any sense of it.
That works fine for stable, narrow band communication signals but not at all for Wifi.
Also, the 433MHz transmission are generally quite short and quite unstable in frequency, which makes them hard to track with a doppler system.
An automatic Amplitude system (somewhat like a doppler but now comparing amplitudes instead of phase) is much more tolerant fo frequency mismatches and therefore more practical on 433MHz.
And of course there's always the possibility to use a simple directional antenna and search by hand...

Doppler does not generally work for digital signals--it is really not a bandwidth problem.

 

[prcguy]

I would not bother with the Vivaldi antennas above as they will not be very directional at the lower frequency ranges. For the OPs needs I would recommend a fixed freq Yagi for 433MHz and a log periodic from Kent Britain to cover 2.4 and 5.8GHz WiFi. You can find cheap Yagi‘s on eBay and here is a link to Kent’s antennas. I would order a model with connector installed.

Printed Circuit Board Antennas| Commercial and Hobby Antennas

 

[Token]

The DDF1 -like any other pseudo doppler system- needs to have the tracked signal cleanly within its FM bandwidth to make any sense of it.
That works fine for stable, narrow band communication signals but not at all for Wifi.
Also, the 433MHz transmission are generally quite short and quite unstable in frequency, which makes them hard to track with a doppler system.
An automatic Amplitude system (somewhat like a doppler but now comparing amplitudes instead of phase) is much more tolerant fo frequency mismatches and therefore more practical on 433MHz.
And of course there's always the possibility to use a simple directional antenna and search by hand...

This really does not fit the OPs requirements, but I find the Kraken SDR excellent at going after 434 MHz and other short duration signals.

The video below is of the Kraken going after one specific 434 MHz signal among many others. In the video the only DOA cuts are on the desired signal, and all others are being ignored. This was just me playing around with detection filter widths and trigger levels, getting to know the system.

T!