Is it possible to enhance the APRS and AIS sensitivity ?

[Waycco]

Describe the enhance request.

APRS and AIS decoding.

I have had difficulties to get AIS / APRS function working on MAYHEM/H4M. I Have not been able to receive/decode APRS message even that I'm sure that I live near area where is a lot of APRS traffic all the time. I can hear the APRS bursts but the APRS app does not decode it for some reason?

AIS works only if you are next to the ship. I have experienced that normally AIS decoding should work from much longer distances.

Is there something that could be done to improve the sensitivity of the receiving and decoding of these applications?

ADS-B works very well but APRS and AIS not that well even if correct length antennas are used for the frequency (SWR<1.4)

Reproduction

Could people test APRS and AIS receiving and
decoding functionalities and give impressions and reports how these functions work?

Expected behavior

APRS and AIS signals normally should be received from many miles distance.

Environment/versions

At sea shore close to active vessel traffic, H4M, latest stable FW.

Anything else?

Maybe the problem is related to user error, or faulty device, but it would be nice if other people would also test these functions and give reports of the results.

[f1ghy]

I agree with that. I have noticed this too since a long time too. It works, but realy unsensitive.

[gullradriel]

I don't know. Last time I got an AIS was from more than 20 km away.

What antenna are you using ? What LNA, VGA, AMP ?

Are these apps really tested enough?

Your tone is a bit rude, isn't it ?

Do you think we are paid or that we owe you anything ?

Please clone the repository, find a better way and push a PR, if you are able to :-)

[f1ghy]

I wood like to compare BW... to the right one dble pressing DFU swich during "Audio app" but it move away too fast !
Ais show:
Rx BW: 1 750 000
Rx SampR: 2 457 600
Modulatn: 1
AM cfg: 0
NBFM cfg:same for APRS exept Rx SampR: 3 072 000
same as POCSAG

[Waycco]

I don't know. Last time I got an AIS was from more than 20 km away.

What antenna are you using ? What LNA, VGA, AMP ?

Are these apps really tested enough?

Your tone is a bit rude, isn't it ?

Do you think we are paid or that we owe you anything ?

Please clone the repository, find a better way and push a PR, if you are able to :-)

Sorry, maybe the tone might sound a bit rude but I think it is the fact that these mentioned "apps" don't work as well compared to ADS-B app for example. Just saying that it is not ideal to release "apps" with functional status if they don't work well.

For example in many Youtube videos HackRF users talk about the AIS function but most of them say that I'm inside of the house or I don't live near the sea so I haven't tested the function. Maybe the APRS or AIS function is not that interested and that's why no one have noticed that they work quite poorly??

This works: https://www.wimo.com/en/picoaprs?srsltid=AfmBOopbBysz2gFZ_v1V_qjPxfW7nENm_YXndVcxXOCIl_ZnIa17sAA6

What antenna are you using ? What LNA, VGA, AMP ? Answer: normal whip antenna connected to H4M sma tuned to 161-162MHz..

I tested years ago some usb dvb-t dongle with AIS decoder and it worked much better compared to HackRF AIS app.

Yes and nobody owe anything to anyone, but I just can't sit silent in home and hope that it starts to work by itself...

Software develops when there is coders, users, testers and people who find problems and report about them...

[ToxxikHalo]

Apologies for jumping in like this but I feel it's justified...
I myself can neither code nor am I adept at even using the PP/HRF1 yet BUT one of the first things I learned and respected and are still in awes of is the incredible work done by a small group of rockstars in the community for the benefit of everyone! These people have full time jobs and full time families and lives of their own in between and STILL force 30 hours into a day to create something unique and awesome for strangers that too often don't appreciate the time and effort and frustration based into any one of the many projects going on in the mayhem community.....
I don't believe you sir were intentionally being rude and don't mean to highjack this thread but the peeps who only benefit without contributing should respectfully take a step back to see the whole picture before question the quality or integrity of something gifted to the mayhem project by an extremely talented individual that usually goes unrecognized...

Again this was more of a general pitch and not towards you Wayyco, plz don't take it as such...

I'm sure every one of the people who create the apps and programs are more than open to constructive criticism and opinion but you'll get nothing without giving them the deserved respect for what they've given already....

My apologies gullradriel, I lnow this isn't the place but I'm at work and had to be fast, lol... feel free to delete if it's inappropriate...

[gullradriel]

Okay, @Waycco. Let me help you a bit, and answer all your things step by step.

APRS and AIS decoding not implemented well?

They are implemented. Well or not, it's already a good start.

APRS works very poorly. Not even one APRS message has been received and I live in area where is a lot of APRS traffic. I can hear the APRS bursts but the APRS app can not decode it.

Is the external TCXO disabled ? What Mayhem version are you using ? What are the LNA / VGA / AMP parameters you used ? What 'whip' antenna ? Have you tested that antenna using a VNA to know if it fits the need ? Have you tried to swap antenna ?

AIS works only if you are next to the ship. Normally AIS decoding should work from much longer distances.

At least it works. Maybe it's the ship antenna, maybe yours. But they are not supposed to cover long ranges like ADSB.

Are these apps really tested enough?

We test what we can, and mostly each dev is testing what he is implementing. Else we are waiting for wonderful and gentle users to test and report. We are not paid company workers.
APRS RX was implemented by Jared Boone and Furrtek, and AIS by Jared Boone alone. Both are not active at all on the Mayhem fork. No one touched these apps since HAVOK.

ADS-B works well, Why APRS and AIS not?

The range of AIS (Automatic Identification System) and ADS-B (Automatic Dependent Surveillance-Broadcast) beacons can vary significantly due to differences in transmission frequency, power, antenna setup, and environmental conditions.

AIS Beacons: Frequency: 161.975 MHz and 162.025 MHz (VHF band)

• Range: Typically 10-20 nautical miles (~18-37 km) for standard AIS transceivers on ships. With higher antennas and favorable conditions, this can extend to 40-50 nautical miles (~74-93 km).

Factors affecting range

• VHF limitations: VHF signals are line-of-sight, so the range depends heavily on the height of both the transmitting and receiving antennas.
• Obstructions: Buildings, terrain, and other objects can block VHF signals.
• Interference: Urban environments or congested frequency bands may degrade reception.

ADS-B Beacons: Frequency: 1090 MHz (Mode S) and 978 MHz (UAT in the U.S.)

• Range: Typically 150-250 nautical miles (~278-463 km) for aircraft at cruising altitudes (30,000 feet / ~9,000 meters).

Factors aiding range:

• Aircraft altitude: The high altitude of ADS-B transmitters (airplanes) means fewer obstructions and a much greater line-of-sight range.
• High transmission power: Aircraft transmit with relatively high power to ensure reliable detection by ground stations and other aircraft.

Why is ADS-B Easier to Receive than AIS?

• Altitude Advantage: ADS-B signals come from airplanes at high altitudes, eliminating ground obstructions. AIS signals are primarily from ships near or on the surface, where terrain and buildings can obstruct signals.
• Frequency Differences: VHF frequencies (AIS) are more affected by obstacles than the UHF frequencies used by ADS-B, which have better propagation characteristics over long distances in open air.
• Power Output: Aircraft ADS-B transmitters often have higher power compared to AIS transceivers on ships, which are designed for shorter-range communication within maritime environments.
• Density of Sources: ADS-B has a higher density of sources (aircraft) that are visible across a wide area compared to the density of ships transmitting AIS signals, particularly if you are inland or far from maritime traffic.
• Antenna Positioning: The success of receiving both signals depends on the height and quality of your antenna. If your AIS antenna is not positioned optimally (e.g., blocked by obstacles), reception will be poor.

Improving AIS Reception

• Antenna Height: Increase the height of your AIS antenna to reduce obstructions.
• Antenna Type: Use a high-gain VHF antenna tuned to the AIS frequencies.
• Pre-amplifier: Install a low-noise amplifier near the antenna to boost weak signals.
• Location: Try placing your AIS receiver near the coast or in open areas with a clear view of the horizon.

If you're far inland, receiving AIS may remain challenging due to its limited range, whereas ADS-B will still work well because of its higher-altitude transmissions.

Test APRS and AIS receiving and
decoding your self do they work?

Yes, but I can't say if they are perfectly working or not. Or maybe I'm not as exigent as you.

Expected behavior
APRS and AIS signals should be received many miles distance.

That is only if all the conditions are here. APRS and AIS are using VHF, so their range depends on antenna height and terrain / obstacles.

Environment/versions
At sea shore close to active vessel traffic

Nice, was the weather good ? It can also be a factor.

Anything else?
Mayhem apps should be tested very well before they are put
to stable FW releases.

That have nothing to do here. It's rude, it's not helping, and it only shows that you're a spoiled one. Plus like I stated before, these apps were here since HAVOC. Their original authors marked them as 'working'. It's the opposite, you should be happy to have apps. Maybe we should make a stable version with only Audio, Capture and Replay, so you would have nothing to complain about ? X-D

Sorry, maybe the tone might sound a bit rude but I think it is the fact that these mentioned "apps" don't work as well compared to ADS-B app for example. Just saying that it is not ideal to release "apps" with functional status if they don't work well.

A lot of things are not going to work as good as ADSB, since it's generally coming literally from the sky, without any kind of obstacle between the emitter and the receiver. Because apps are not working well for you is not a sign that they are not working for others.

For example in many Youtube videos HackRF users talk about the AIS function but most of them say that I'm inside of the house or I don't live near the sea so I haven't tested the function. Maybe the APRS or AIS function is not that interested and that's why no one have noticed that they work quite poorly??

Maybe because when they tested, the apps were providing them enough satisfaction ?
AIS was working for sn0ren when he was on a ferry, justa few weeks ago:

Jeremiah of all trades is showing APRS RX in a video here:
https://www.youtube.com/watch?v=eMlHDwDGr3E

See, others reported it working: https://www.youtube.com/results?search_query=APRS+portapack

Conclusion

• The mentioned apps are working. They are not the most sensitive ones, but they are not 'buggy'
• You do not know how to ask things, you are having an offending tone.
  Please read https://github.com/portapack-mayhem/mayhem-firmware/wiki/How-to-ask-questions-in-correct-way
• I'm still waiting for your LNA/VGA/AMP settings, Mayhem version, channel / frequencies used when trying the apps
• The issue will stay open, as an enhancement request, because it's what it is
• Next time use a better, simple tone. Just report your thing without the unnecessary critics. We do not need them to try to help you
• It's usually a good thing to open one issue per question
• It's usually a good thing to give the antenna used, the Mayhem version, used channels or frequencies, LNA / VGA / AMP values
• Have a good day

[f1ghy]

Hello.

And verify that internal LNA amp give gain and not atténuation (it may burn). "Looking glass" app with waterfall is a quick an easy way to verify that.

Maybe, It must also be said that HackRF is a wonderfull general-purpose receiver, wideband, without filter stage, and ONLY 8 BITS.
Like everything that does a lot of things... it does it less well than a specialized device (which would not fit in our pocket).
But... It does quite well what we ask of it... (because it has a magnificent PortaPack team, helpful, efficient, H24 because all around the globe.... makes it live, of course ;0) )

Thanks to them !
😘

[Waycco]

Hello.

Ok, I got the point. Sorry about the too direct comments. Have to be more careful next time.

Edited the initial request text to be a bit more polite.

[Waycco]

Hello.

And verify that internal LNA amp give gain and not atténuation (it may burn). "Looking glass" app with waterfall is a quick an easy way to verify that.

Maybe, It must also be said that HackRF is a wonderfull general-purpose receiver, wideband, without filter stage, and ONLY 8 BITS. Like everything that does a lot of things... it does it less well than a specialized device (which would not fit in our pocket). But... It does quite well what we ask of it... (because it has a magnificent PortaPack team, helpful, efficient, H24 because all around the globe.... makes it live, of course ;0) )

Thanks to them ! 😘

Hi,

• Yes LNA gives gain and it is working.
• My "whip antenna is a dipole" tuned to wave length using Nano VNA.
• LNA AMP set to 1 = ON

[f1ghy]

Hi, I spend time to do test APRS for you.

I have nice results here, in the north of the France, with AMP on (1) and LNA 32 and VGA 40 (on an hackrf clifford edition) and AMP 1 LNA 24 VGA 32 on an regular r9.

Some stations may have a bandwidth larger than the 8,5khz. So you can try to increase your reception bandwidth in a file named rx_aprs.ini , in the setting folder. There, there is a line: nbfm_config_index. it should be 0 for 8.5kHz, 1 for 11kHz and 2 for 16kHz. you can try to change the 0 to 1.

Most station have 8.5Khz bandwidth, and a too large bandwidth may down the sensivity. But i have nice result with nbfm_config_index to 1, too. It maybe more tolerant in case of less tcxo/frequency stability but too large bandwidth may down the sensivity...

I am not at home, and too far from any boat to make AIS test. There is also an rx_ais.ini

A way to modify these files is in "settings menu" then "app setting"

Make try and test, then tell us to participate.
Thanks.
;o)

[Waycco]

Hi, I spend time to do test APRS for you.

I have nice results here, in the north of the France, with AMP on (1) and LNA 32 and VGA 40 (on an hackrf clifford edition) and AMP 1 LNA 24 VGA 32 on an regular r9.

Some stations may have a bandwidth larger than the 8,5khz. So you can try to increase your reception bandwidth in a file named rx_aprs.ini , in the setting folder. There, there is a line: nbfm_config_index. it should be 0 for 8.5kHz, 1 for 11kHz and 2 for 16kHz. you can try to change the 0 to 1.

Most station have 8.5Khz bandwidth, and a too large bandwidth may down the sensivity. But i have nice result with nbfm_config_index to 1, too. It maybe more tolerant in case of less tcxo/frequency stability but too large bandwidth may down the sensivity...

I am not at home, and too far from any boat to make AIS test. There is also an rx_ais.ini

A way to modify these files is in "settings menu" then "app setting"

Make try and test, then tell us to participate. Thanks. ;o)

Hi, thank you very much. I'll do that. Do you use full length antenna or 1/2 or 1/4?

Waycco

[gullradriel]

@f1ghy thanks for the tests. Do you think adding a bandwidth control in the app is worth it, or should we leave it at the default ? It may be difficult to add as the GUI is already a bit full. Maybe in a third tab, if it works.

I will edit the APRS RX wiki page to reflect that it may need AMP 1 to have good results, and that you can tune the settings tuning if default is not enough.

[gullradriel]

Edited the page to add the comments, in a new "Important Notes" section:
https://github.com/portapack-mayhem/mayhem-firmware/wiki/APRS-RX#important-notes

[f1ghy]

Hi, thank you very much. I'll do that. Do you use full length antenna or 1/2 or 1/4?

Waycco

My advice is that a 1/4 or a dipole of 2x 1/4 work fine, may be vertical or horizontal polarization (AIS, and APRS should be vertical polarisation). Dipole antena of 2 1/4 wave length may be done with télescopics antenas for diferents frequencies or with simples wires to put on the roof...
So it could be nice antenas easy to use, and easy to make yourself ;o)
(Others 1/2 or full lenght antenas need impedance matching or phase matching of diferents part)

[f1ghy]

@f1ghy thanks for the tests. Do you think adding a bandwidth control in the app is worth it, or should we leave it at the default ? It may be difficult to add as the GUI is already a bit full. Maybe in a third tab, if it works.

It may be an idee... wait and see différents advices and test. An others way is to down the sample rate to make CPU work easyer if necessary (Remember there was questions about it for "pocsag app" some month ago, one year ago maybe).

[f1ghy]

Hi, thank you very much. I'll do that. Do you use full length antenna or 1/2 or 1/4?

Waycco

My advice is that a 1/4 or a dipole of 2x 1/4 work fine, may be vertical or horizontal polarization (AIS, and APRS should be vertical polarisation). Dipole antena of 2 1/4 wave length may be done with télescopics antenas for diferents frequencies or with simples wires to put on the roof...
So it could be nice antenas easy to use, and easy to make yourself ;o)
(Others 1/2 or full lenght antenas need impedance matching or phase matching of diferents part)

You are welcome on discord mayhem too, if you need other or more information or help.
https://discord.gg/BjGyaKfB
;o)