Chase vehicle SSB receiver advice please

[Nick McCloud]

At present I'm using a hand held Yupitera MVT-9000 with a Diamond MR-77S SMA 2M/70CM magmount which works absolutely fine with line of sight, not so much when there is more than one tree along the road side between me & the balloon.

However by the time I've got it all plugged in and then on to a laptop for dl-fldigi plus a phone for internet, I'm drowning in cables so I'm looking at a more self-contained setup.

I've been chasing around for an in-car receiver/transceiver for a while but keep being outbid so I'm now thinking of SDR but can't find any comparable specs:

I'm using this: Yupitera MVT-9000 = 0.5uV at S/N 10dB

This is available at reasonable price if I can win: Yaesu FT-100 = 0.125uV at S/N 10dB

This is what I started originally looking for but can't find one at present: Yaesu FT-780R = 0.5uV at S/N 20dB

Can bid on one of these but seems a bit of a marginal improvement: Yaesu FT-817ND = 0.25 µV at S/N 10dB

I'm not licensed and have no pressing need to be, so transmitting voice isn't a priority.

I'm aware there's a wide range of possible SDR's and I know that the Raspberry Pi Skycademy portable tracker used the Airspy Mini but as I can't find comparable sensitivity measurements for SDR's, can anyone make a recommendation between an actual mobile transceiver and the various SDR's without going off in to silly investment territory. By that I mean the Yupitera handhelds that do SSB (MVT-7100 and MVT-9000) are around £100 on eBay.

The mid-range options seem to be FUNcube Dongle Pro+ (~£150), AirSpy Mini (~£120) and SDRplay RSP-1A (~£90). However as I have 3 portable Pi based LoRa trackers begging for an SDR, if well made RTL based units are going to be usefully better than the MVT-9000, I'd rather equip all three like that, or two of them with something budget and using the third one as a self-contained unit that I use with a better SDR.

As I've now got proper antenna's at home for my LoRa gateway, an additional recommendation for a desktop SSB receiver would be useful - either SDR or one with lots of buttons to keep me amused.

I can run to a mid-range SDR and an RTL one to try out the logistics, but I'm all digital so have no way of doing a scientific comparison - no kit, not enough knowledge.

Cheers for any advice,

Nick

[Mike Sharps]

Hi Nick, there is a bunch of stuff you mentioned  there that I am equally interested in so any advice on receiver setups etc much appreciated. Can I ask what you mean by ‘proper antennas’ for your gateway setup. 

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[Leo Bodnar]

Johnson noise in 3kHz BW from room temperature 50R source is 0.05µV

10dB S/N requirements makes it 0.15µV

20dB S/N is 0.5µV

//I'd keep going but run out of punch cards

//Leo

//

[Stuart Robinson]

If your prepared to accept advice from a long-timer who misses the days when you mined for tin to make your own solder and bred cats for their whiskers;

Of the receivers you mentioned I have tried these for real long distance FSK RTTY, best as in most sensitive first;

FT817ND

Funcube Dongle Pro+

El cheapo RTL SDR dongle.

All the above RXs beneffited from a decent LNA, in particular the RTL, where an LNA was almost essential. Best LNA I use is an SP7000, but it's really a masthead device. The G4DDK VLNA can be built into a box with battery and is almost as good as the SP7000.

[Steve Aerospace]

I've got or have tried:

    FT817ND and older FT817

    FT790

    Yupiteru MVT-7100

    NooElec NeSDR Smart (R820T based)

    NooElec NESDR Smart XTR (E4000 based)

    Funcube Dongle Pro+

IMO for RTTY by far the best is the FT817 (either type - I think they are identical other than coverage and output stage).   

I don't like SDRs for car use - they usually stop working when you need them most - either some form of hardware (e.g. USB connector) or software glitch requiring a re-boot - usually timed in the critical last few minutes of the flight when you are the only receiver. 

It may just be the one I had, but I didn't get on with the Yupiteru 7100 - less sensitivity and many spurious signal appearing.

I don't think Sam G4DDK's (he is a local) VLNA70 (the 70cm version of his VLNA) is available any longer.

    Steve G8KHW

On 25/08/2019 15:16, Stuart Robinson wrote:
> If your prepared to accept advice from a long-timer who misses the > days when you mined for tin to make your own solder and bred cats for > their whiskers; > > Of the receivers you mentioned I have tried these for real long > distance FSK RTTY, best as in most sensitive first; > > FT817ND Funcube Dongle Pro+ El cheapo RTL SDR dongle. > > All the above RXs beneffited from a decent LNA, in particular the > RTL, where an LNA was almost essential. Best LNA I use is an SP7000, > but it's really a masthead device. The G4DDK VLNA can be built into a > box with battery and is almost as good as the SP7000. > > > -- You received this message because you are subscribed to the Google > Groups "UKHAS" group. To unsubscribe from this group and stop > receiving emails from it, send an email to > ukhas+un...@googlegroups.com > <mailto:ukhas+un...@googlegroups.com>. To view this discussion > on the web visit > https://groups.google.com/d/msgid/ukhas/f9fda9b5-d3b5-4b21-b396-b7f5858969e6%40googlegroups.com > <https://groups.google.com/d/msgid/ukhas/f9fda9b5-d3b5-4b21-b396-b7f5858969e6%40googlegroups.com?utm_medium=email&utm_source=footer>. --

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[Stuart Robinson]

> I don't think Sam G4DDK's (he is a local) VLNA70 (the 70cm version of his VLNA) is available any longer.

I did check before posting, the Website is still quoting a price of £55, and the home page says;

"I will contunue to produce preamp kits"

[David Akerman]

Agreed re SDR in the car ... at least one chase team lost their tracker due to breaking off the USB plug on an SDR hanging from a laptop port.  Granted that that can be fixed with an extension lead, but you've still got the issue of having to run an SDR program as well as dl-fldigi at the same time, and with those and the virtual audio cable that's 3 pieces of software to go wrong instead of 1.  It's bad enough running anything on a laptop in a bouncing car (or maybe that's just my driving) so try not to complicate it.

Also, an 817 or scanner can just be picked up and taken out on foot if needed, which it might be (e.g. the flight landed on a golf course and someone has used it to adorn their trolley).

An 817 is much more sensitive than any of the scanners I've used (Yupi 7100, AOR 8200, ICOM R-10) but heavier, more expensive, and had crappy battery life and management (fixable).  I have an 817 in the car, wired for charging, and keep an R-10 in the glovebox in case I need it.

That all said, I can't remember the last time I bothered decoding RTTY in the car as I always run LoRa these days, which is a whole lot simpler to manage in the car.  The 817 is really there just so I can listen to the radio signal rather than decode it.

Dave

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[David Akerman]

Oh, and I forgot to mention, you'll probably get better results from the magmount by removing the rod and replacing with one trimmed to 1/4 wave.  Less directional and less flappy in the wind.  Remember that when chasing the balloon can be high above you, so you don't need gain in the horizontal direction.  Also, many magmounts rods are thin wire with loading loops, so they bend back in the wind (again, my driving may be a factor ....).  I've replaced all mine with brass hex spacers with brass rod soldered on, all covered in heatshrink.

Dave

[Steve Aerospace]

Oh - the product page says its "No Longer Available":

    http://www.g4ddk.com/Products.html

Its not listed on the prices page either:

    http://www.g4ddk.com/Prices.html

I felt sure I'd seen a post from him on the "Codgers" group we both belong too.

    Steve

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[Stuart Robinson]

On Sunday, August 25, 2019 at 4:47:48 PM UTC+1, G8KHW wrote:

Oh - the product page says its "No Longer Available":

    http://www.g4ddk.com/Products.html

Fair enough, I was mislead by;

• VLNA23 Covers all versions
  

Which links to the instructions including the 70cm Version.

[Mikael Dagman]

I would recommend you look into the airspy mini  (https://airspy.com/airspy-mini/) also using this setup in a car with moderate (short) antenna cable lenght a lna will not work well, most likley you will overload the radio, so just an antenna and the sdr radio, also check out the rtl-sdr blog one (V3) which you probably already have heard of, https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/

/Mikael

[Oliver de Peyer]

How about the Kenwood TH F7E?
An all-modes handheld scanner/FM handheld transceiver.
It has a lithium battery and the battery life is very good.
It is quite compact ‎and robust (I have dropped mine, spilt water on it etc and thus far is has survived).
For compactness, a TH F7E and a smartphone running the Android tracker is probably the smallest package you can get and totally hand-portable.
Using the TH F7E's rubber duck antenna alone, I could receive and decode Steve's flight from last year's conference at Cranfield, from _inside_ a train, most of the way back to London! I also received B-64 as it flew overhead in 2013 (I was on holiday in Cornwall at the time)
The main fiddly bit is connecting up the audio since like many handhelds it has one of those two pin connectors and the sleeve, pin connections etc were quite eccentric. I had to rig up a voltage divider etc.
BW
Oliver
M0LVR

[Steve Aerospace]

I've got a couple of different battery solutions to the FT817 "crappy battery life" problem -

    In one I use one of these 3000mAh Lipo Packs e.g. :- https://www.amazon.co.uk/WINDCAMP-3000mah-Polymer-Lithium-Battery-Black/dp/B01LW3X1EB

    In the other (following Stuarts previous advice about low self discharge Nickle Metal Hydrides) I use 8 x AA Duracell 2500mAh Duralock in the standard FT817 spring loaded battery pack**

Both solutions last well over 5 hours.

    Steve

** with the green wire disconnected so the batteries charge externally - but see this page for limitations of this solution: http://www.ka7oei.com/ft817_batt.html

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[Ross G6GVI]

As Stuart says, the performance of most receivers can be improved by a Low-Noise Amplifier (RF pre-amp) - particularly if you have significant cable-loss between the antenna and receiver.

But just adding gain in front of the receiver can also be detrimental, as it increases its protential for overloading.

Thus the best pre-amps include a narrow Band-Pass Filter, so that they only amplify the wanted band whilst rejecting strong out-of-band signals.

And you don't want too much gain - between 10 and 18dB should be plenty.

My home tracking station uses a 25 year-old Cirkit pre-amp kit at the mast-head: this has about 13dB gain and incorporates a tight BPF.

This unit is long-obsolete, but I see that there are some promising modern alternatives around.

Here's a little LNA with some filtering of the higher frequencies:

https://www.ebay.co.uk/itm/New-433MHz-Low-Noise-Amplifier-LNA-400MHz-470MHz/262542167831

but this still has much too wide a pass-band - however it could be followed with one of these narrow SAW filters:

https://www.ebay.co.uk/itm/433MHz-315MHZ-Bandpass-Filter-SMA-Remote-Control-Digital-Transmission-Receive/332710256942

A combination of these two could be built into a compact unit which should "liven up" any receiver.

[Stuart Robinson]

If your using LoRa then I dont see why you would need to decode the FSK RTTY in a car. The LoRa from the tracker can perform as well as or better than the FSK RTTY distance wise.

The LoRa receiving kit is cheap and easy, the FSK RTTY receiving kit is neither.

Thats not to suggest not using FSK RTTY. If the tracker fails in some way, such that its transmittting but the location is not being updated, you can get a good direction fix on the FSK RTTY signal using a directional antenna and a low cost UHF handheld like a Baofeng.     

[Steve Aerospace]

One thing I find lacking with stand alone LoRa is audible (or visual) feedback on the signal tuning - which is a disadvantage given the noticeable temperature drift of most of the modules.  Some of this can be compensated by LoRa AFC and wider modes (less so on 434MHz than 868MHz due to mode restrictions) .    There have been situations where Ive been driving along and the LoRa signal has been lost for a period and by the time its regained the frequency has shifted so much the AFC no longer locks.  

I find listening to the signal coming trough very comforting all is working OK - Its something I can do while driving without having to look at screens.  Also with RTTY you can hear the Doppler shift when the balloon bursts.   I guess you could ad some form of audible announcement for each received Lora packet but these days I find myself using both LoRa and RTTY but still listening to the RTTY.

    Steve

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[Stuart Robinson]

On Monday, August 26, 2019 at 12:52:10 PM UTC+1, G8KHW wrote:

One thing I find lacking with stand alone LoRa is audible (or visual) feedback on the signal tuning - which is a disadvantage given the noticeable temperature drift of most of the modules.  Some of this can be compensated by LoRa AFC and wider modes (less so on 434MHz than 868MHz due to mode restrictions)

These problems could be solved by using the SX1262, operation at even 7.8khz bandwidth, no AFC or tuning required for modest temperature differences. At 20.8khz bandwidth easy peasy.

Read about it here;

SX1262 – Improved LoRa Device

[David Akerman]

Actually my Android tablet app does have the option of an audible bleep for each packet, as well as speech when something significant happens (e.g. balloon has burst, signal lost or retained), but even so I agree with you that having the rtty audible in the car is very reassuring and also very informative.

Dave

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[Dave B]

Hi.

Why use VAC?  In Windows, just enable the audio out "monitor" devices,
then you can tell dlFldigi to use the "Monitor" of whatever sound output
you use..

Works well on Win7 etc.  (No, I can't remember exactly how to enable the
monitors, it's been a while since I needed to do that under Windows, but
Uncle Google will no doubt know.)

No such issues with Linux either, (Mint 19.2 and using Pulse / PAVU
control.)

73

Dave G8KBV.

PS:    SDR dongles velcro'd to the back of laptop screen with a short
USB extension lead are OK.  Just don't put it near where the backlight
driver is!  (Some are in the lid/screen, some in the main body of a
laptop.  LED and CFL types are quite noisy.)

Or, have the dongle mounted elsewhere in the vehicle, to keep the RF
path short, and use a USB extension cable to the lappy.

>><<



On 25/08/2019 16:32, David Akerman wrote:

> but you've still got the issue of having to run an SDR program as well
> as dl-fldigi at the same time, and with those and the virtual audio
> cable that's 3 pieces of software to go wrong instead of 1.

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[Nigel Worsley]

On Mon, 26 Aug 2019 at 14:14, 'Dave B' via UKHAS <uk...@googlegroups.com> wrote:
> Why use VAC? In Windows, just enable the audio out "monitor" devices

> Works well on Win7 etc. (No, I can't remember exactly how to enable the
> monitors

Google has plenty of advice on how to do this for Windows 7, but
nothing on later versions. Having done this on Windows 10 a couple of
days ago I can offer the following:
In Windows Settings select System, then Sound. Down the bottom under
Related Settings is Sound Control Panel, click on this and then go to
the Recording tab and enable Stereo Mix - and possibly set it as the
default recording input, depending on what else you use the computer
for.

Nigle

[f.michal]

Many have pointed out either LoRa or an SSB capable receiver/scanner as a go-to solution for a chase car.
And indeed these options are hard to beat when it comes to robustness and reliability.
However if you seek something more integrated, cheaper and are not affraid of some fiddling (it's a hobby after all, right?) you can take a look at habdec.
I created it exactly for this purpose: I needed a chase-car solution, or something I can take with me outside but I didn't want to buy scanner or FT-817

You can install habdec on RaspberryPI/whatever with a decent SDR (I use AirSpy, possibly with filtered preamp) and throw it into your car. You then connect to it from a tablet or mobile with any browser, here are two examples from older versions:
    https://www.youtube.com/watch?v=dli8FEFy5tM
    https://www.youtube.com/watch?v=hCXeIi8ZSyo

Mind this: I have yet to test tracking in a car, but it works OK for a base station - I often connect and track balloons while being off-home or while driving.

Extra: I have an almost working browser based app which integrates habdec, offline vector maps from OSM and GPS position, so  this has a chance to become all-in-one solution. If there's interest I can show some screenshots and publish code when it's ready.



W dniu 25.08.2019 o 12:38, Nick McCloud pisze:

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[Mark Jessop]

Interesting discussion here.

Last flight I ended up doing all the telemetry reception (4FSK, RTTY, Wenet Imagery and LoRa) headless, with zero user intervention during the flight. The various RPis were configured to start up the decoders on boot, and emit telemetry information into the network for display on my chasemapper mapping application (https://github.com/projecthorus/chasemapper ). I recently (as in, the day before the launch) added the ability to show the modem's reported Eb/N0 figure on Chasemapper's telemetry table - you can see this on a screenshot near landing here: https://photos.app.goo.gl/WgGQx4Wmh9SxYLiA9 (Yes, those SNRs are negative. I think the modem Eb/N0 calculation needs some tweaking.).

Just like Steve, I've been very used to listening to the telemetry throughout the flight, as a 'comfort' thing. However wth chasemapper all I really need to care about is that the payload data age indication doesn't go red. If it isn't red then I've had data in the last 30 seconds. If it's red, then maybe I should look more closely at the SNR figures and see if something is going wrong.

For the *entire flight*, I was receiving the 4FSK and RTTY payloads using one RTLSDR (the payload frequencies were close enough that I could do this using a single 48 kHz IQ stream from the RTLSDR). I do use filtered preamplifiers at the base of the antennas, so that does improve performance quite a lot. Also using 4FSK instead of RTTY (especially when decoding with dl-fldigi) is an instant 6dB performance improvement, and has FEC so copes *much* better with fading. Info on this modem is here: https://github.com/projecthorus/horusbinary  I believe it's been used a bit in the netherlands, but AFAIK it hasn't been used in anger in the UK yet. 

Overall, there were zero issues with the setup, so yes, a RTLSDR (*with a filtered preamp!!!*) is well and truly suitable for use in a chase car. 

73

Mark VK5QI

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[Dave B]

That's the trick.  The only difference it seems between Win7 and 10, is
how to get to the Sound control applet*.  Once there, the tricks are
much the same.  (* In W7, start, control panel, sound)

And yes, it's "Stereo Mix" (not "monitor") that is needed.  (I think
Monitor was the earlier name, back in the XP days.)

In effect, all it does is route a copy of the analogue output, round to
an analogue input for recording, so it's not (AFIK) a digital copy, but
more than good enough for HAB decoding, or decoding ShortWaveRadiogram,
from a WebSDR, or SSTV from QO100 and the BATC WebSDR at Goonhilly.  Or
anything else you can hear via a PC!  ;-)

Regards to All.

Dave G8KBV

[Nick McCloud]

Thanks for all the replies.

Mike: Watson W-50 on 6m aluminium pole so it’s got 360º view of the sky above the house. Previously it was a Diamond MR-77S duct-taped to the roof - it worked OK but now I can hear launches as far as Dave and almost as far as Elsworth.

Leo: I think you’ll find the Johnson noise has increased dramatically in the last few weeks … … and one day I’ll have enough RF knowledge to fully appreciate your reply!

Stuart: Always happy to accept advice, particularly as I live next to a tin mine and have 6 cats … I’ll decode anything and everything to keep the students engaged. I’ll get some NiceRF SX1262 modules and look to fly some over winter. 

Stuart/Steve: G4DDK appears to have the PGA432 as a build your own LNA but I’ll pencil in a winter evening to see if the parts are available for the VLNA70

Dave: Point taken about 3 points of software failure. I’m currently using sound input dongle on laptop so very aware of potential breakages. Will schedule brass mod to an antenna for winter. Aug 2nd flight ended up with me outstanding in a wheat field with my handheld & laptop after junior scientist had dropped the Pi LoRa box in his haste to get out the car, so I appreciate the utility of having a backup.

BUT, Dave, legend has it you can decode RTTY just be listening to the signal.

Oliver: Much as I’m seduced by shiny pictures of Dave’s ICOM R-10 and your suggested TH F7E, my budget doesn’t run to a new(ish) transceiver.

Ross: A pre-amp for home is on the to-do list, thanks for the recommendations.

Mark: Interesting, many keeping in car systems simple as there are many points of failure, yet you turn things up side down by having all sorts of kit running with some techniques that I for one will love to find a Sixth Former to investigate - love the use of mandrolic - curiously not in the dictionary but listed in the, erm, dictionary.

So, joining up the dots, the utility value of receiving & decoding RTTY on the move seems deprecated and as such my Yupitera appears adequate. Thanks for suggestions on the various other accessories and mods.

It feels like an SDR with LNA & SAW would be a good starting point for home so I can be a good HAB citizen and receive RTTY as well.

Given the benefit of the LNA & SAW on the home LoRa gateway (Upu dual modules on a Pi), having a go with the RTL-SDR to see what I can achieve in the first instance also means I have an SDR I can take in to schools - on an extension lead so the bugger doesn’t get snapped off.

Then I can wait for the next round of household budgetary allocations in the new year (assuming we aren’t all dead from lack of basics due to the aforementioned Johnson noise) and look at a desktop SDR or something with knobs, dials & buttons - which would then take me back 40 years when I was slowly learning morse …

[Oliver de Peyer]

‎Just one more time on this - in a way the different approaches are comparing apples and pears, in that a "proper" receiver or ham radio will cost more but will probably come with more gubbins built in.

For instance, I have a NooElec SDR dongle, more than a basic dongle in that it has been partially ‎enhanced for amateur radio use. But it doesn't have an LNA and it has an odd push fit MCX type antenna connection. Proper SMA connections etc cost more for a different model. This alone was £20 and as I said doesn't have a proper antenna or antenna connector. All that stuff needs to be homebrewed on top.

My TH-F7E cost me £90 on eBay and is capable of being used effectively standalone, particularly out in a field somewhere.

I imagine they all cost about the same once all gubbins have been included. 

(For instance both options above would benefit from a good Yagi antenna and when I tried to build one from a kit this ended up as a whole extra level of complexity)

Personally, high altitude balloons led me into Amateur radio, I sat my exams at the conference, and so ‎the choice of an actual transceiver made sense.

Bw

Ol

M0LVR

‎