Raspberry Pi Forums

Hi;

I am starting to build DIY 70cm Antenna's for our HAB project (Base Station, Chase Car) and learning how to use the tracking software (gqrx fo Mac and dl-fldigi). Rather than waiting for other flights to transmit to test I want to go ahead and put together our own transmitting hardware which we will then use for our flight.

I am opting for a pre built PITS board but just need a little help on what else to get (just to be a able to transmit and receive at the moment) I also want to be able to download images during the flight and believe that I can do this with SSDV but could also use LORA for faster transmission as well, but what extra hardware do I need to transmit and recieve LORA?

The LORA board has one connector on it, I guess for a stubby antenna? The PITS board has two connectors are these for GPS and Radio Antenna (which ones come with the kit and what else do I need, do I need extension cables for mounting antenna outside the payload?

So can someone help with a list (most kit from UPTRONICs)? e.g.

Pi B+ https://store.uputronics.com/index.php? ... duct_id=75
PITS Board https://store.uputronics.com/index.php? ... duct_id=52
LORA Board ?
Antenna(s) / connectors for the PITS / Pi / Lora?

What do I need on the recieving end for Lora transmissions (this may negate using Lora if it is more expense?)

Sorry for all the questions but I don't want to waste money

I've answered this on the UKHAS mailing list (https://groups.google.com/forum/#!forum/ukhas), but for those who aren't members ...

Yes, SSDV works over RTTY or LoRa.

For LoRa you need one of those boards on the tracker, and another one on the ground, so that needs another Pi. See http://www.daveakerman.com/?p=1719

Each LoRa board needs connecting to a suitable aerial; at the tracker this could be another 1/4wave made from coax and single-core wire, but try to keep that and the RTTY aerial away from each other by at least 1/4 wavelength (16.4cm). On the ground you can use the same sort of aerials you're planning to use for RTTY. Or you can use a single aerial into a splitter.

Dave

daveake wrote:I've answered this on the UKHAS mailing list (https://groups.google.com/forum/#!forum/ukhas), but for those who aren't members ...

Yes, SSDV works over RTTY or LoRa.

For LoRa you need one of those boards on the tracker, and another one on the ground, so that needs another Pi. See http://www.daveakerman.com/?p=1719

Each LoRa board needs connecting to a suitable aerial; at the tracker this could be another 1/4wave made from coax and single-core wire, but try to keep that and the RTTY aerial away from each other by at least 1/4 wavelength (16.4cm). On the ground you can use the same sort of aerials you're planning to use for RTTY. Or you can use a single aerial into a splitter.

Dave

Dave thanks for the response, I am still a little unclear ref connectors etc.

If not using LORA
I'll need a Model A+ or B+ RPi
PITS Board KIT (Which comes with a GPS antenna and RG174 Tail for making into a radio antenna using this guide:
https://ukhas.org.uk/guides:payload_antenna

Do I need extra extension cables for the GPS or 1/4 Wave Antenna for the payload?

If using LORA
I'll need all the above and 2 x LORA boards (one in the payload and one on the ground). I will also need an antenna on the payload for the payload LORA board and I guess a pigtail (used as an extension) to connect the Antenna to the board so that the antenna extends outside of the payload?
I will also need another RPi with a 40 Pin header to connect the second LORA board to, this LORA board will need an antenna connected via coax.

LORA Antenna You mention a 1/4 wave antenna, all the 70cm antennas DIY build guides I have found are 1/2 wave antenna, I have built a 1/4 wave version of an RG58 design using HDF 200 (adjusted based on the different VF) but have been advised that 1/4 wave antenna's will not work, I am very confused

Sorry

Bill H

No LoRa: The PITS kit has everything you need for the tracker electronics, aside from Pi/camera/batteries. The aerial is a "pigtail" which means a short piece of cable with a plug on the end; you make this into an aerial as per the supplied instructions.

If you haven't done so, please read the PITS manual (linked to on the home page at www.pi-in-the-sky.com) as it explains all.

LoRa: The LoRa board isn't a kit, so you need to add an aerial. Easiest method is to buy a pigtail or a cable with SMA plug on both ends (cheap on ebay). I do the latter - chop it in half and you can make 2 aerials, plus have some spare cable for other uses.

When you make an aerial, just make sure it has enough cable to reach outside the payload, so you don't have to extend it.

1/4 waves are the preferred design for payloads as they are small and efficient. I don't know who told you that they don't work, but if that's actually what he said then you should ignore everything he says.

Dave

Sorry Dave I edited my response whilst you were replying.

Ref the 1/4 wave, this was referring to the receiver end? Details here:
https://groups.google.com/forum/#!topic ... HtzIfm3JBQ

I used this guide:
http://www.rason.org/Projects/collant/collant.htm

And this calculator to adjust the design specs for HDF400 instead of RG58:
http://jeroen.steeman.org/Antenna/collinear-coax

Following the advice on the calculator page (that a 1/4 wave could be made instead) I made an antenna using 8 1/4 wave segments instead of 1/2 wave. I have not really had the chance to test it (apart from trying to pick up the HERMEs flight in the week (think I had dl-fldigi setup incorrectly).

You said "have been advised that 1/4 wave antenna's will not work"

That's not what Steve said in the UKHAS conversation. That was about using 1/4 elements in a composite (colinear) antenna. That's a completely different situation to a single-element 1/4 wave antenna.

For the payload you should use a 1/4 wave antenna with ground plane.

For the ground there are many different designs that will work, including a 1/4 wave with ground plane. For more gain and therefore more range you could use a colinear or a yagi, but even a simple, easy to make and very inexpensive 1/4 wave will work fine. Any aerial with gain (colinear, yagi) achieves that by being directional, so in some circumstances (e.g. payload high above you) will perform less well than a 1/4 wave. No need to overcomplicate things.

Dave

Ah, all becoming a little clearer now.

I have seen the link on the PITS page on the Uputronics site for making a 1/4 wave antenna for the payload.
You mention that the LORA in the payload also needs a 1/4 wave antenna made using a pigtail, is this the same design as the one linked here:https://ukhas.org.uk/guides:payload_antenna or different? If its different all the 1/4 waves I have looked at seem to have radials, are you able to point out a design that works?

Just to to go an run the Barnstaple Pi Jam and I know there is at least 1 x old school HAM guy that attends so i'll have a chat with him also.

Bill H

LoRa and RTTY are just different ways of modulating data onto the radio frequency, so you use exactly the same aerials for one as for the other.

All 1/4 wave antennae are simple a transmitting element 1/4 wave long (which is 164mm for 434MHz), and something to emulate an infinite ground plane (effectively, a radio mirror). When you see aerials on a car roof, that's what the roof is doing. On payloads I've sometimes used a sheet of cooking foil on the bottom of the payload, but it can be difficult to get a good electrical connection to that. It's easier to use some wires instead - typically 4 but that's not a special number. Their length isn't special either - longer makes for a slightly stronger signal but commonly they just reach to the outside of the payload.

Dave

And the radiating element of the antenna is connected to the central core and the ground plane mirror to the outer shielding?

See the guide at https://ukhas.org.uk/guides:payload_antenna

Just received my package from Uputronics, went a bit retail mental when ordering and bought extra Antennas over £200 worth - OUCH!!
Got a stubby antenna and two whips. I will be making my own antennas for the base station for experimental and learning purposes but thought it would help getting some working antennas for testing my DIY ones. i.e test the hardware setup with a know good antenna and then plug in the DIY.

That's a large percentage of the total I've spent on aerials over the years!

For anyone else watching, all you really need is this for the chase car:

http://cpc.farnell.com/1/1/21033-watson ... tenna.html (£17)

That's the minimum spend. Next purchase should be a Yagi for the chase car, in case the signal is too weak after it lands (in a ditch):

http://www.moonraker.eu/amateur-radio/b ... gi-antenna (£40)

and if you're setting up a base station, one of these:

http://www.radioworld.co.uk/w-30_watson ... al_antenna (£50)

Total £107, and that's a nice set that's plenty good enough.

Dave

Dave;

Just re-read my post and realised I had worded it incorrectly (and I'm a teacher, tut, tut), the £200 included a PITS kit and an extra LORA board