[OZAPRS] Considerations For Setting Up an igate (RasPi)

Fri Jan 17 13:21:04 AEDT 2020

Just a follow up on this, I obviously didn't set up an igate, but I think I
might make it a small project for myself to make it happen. And thanks for
the input so far. Current ETA would be Q4 this year.

I have modified my plan slightly. I'm going to work on getting it onto the
roof of the house, this will give me a height of roughly 7m. The house is
an older house and has a high roof and brick chimneys, and means I will
need to source a tall enough ladder. Hey What's That gives it spotty
coverage short of Gunbower to Koondrook, falls well short of Kerang and may
make it to some parts of Pyramid Hill as the land starts to get lumpy down
there.

I'll work on running off mains, and put the Pi as close to the antenna as
possible without being out of reach for maintenance. Running off mains
means the difference of quite a few dollars to the project.

As per suggestions, I'll make it a two-way igate, which means I will look
at getting something with a few more watts output. I'm open to suggestions
for a good transceiver, but I might stick to 5W as more power probably
isn't going to give me significantly more coverage, and just adds to the
cost in a non-linear direction.

I'm also going to look into ways to remote login or execute remote
commands, this might mean a reverse shell to a VPS online somewhere as I
can't guarantee the internet at the location will not be NAT'd multiple
times.

73,
vk5wtf/4, vk3tst/4

On Wed, 18 Dec 2019 at 12:10, Matthew Cook <vk5zm at bistre.net> wrote:

> Dang it I missed the charge efficiency of the VRLA battery below,
> increases the size of the solar panel a bit more;
>
> *"So based on the number of cloudy days vs sunny days and we assume 5 days
> cloudy is worst case, then you need to recharge the battery (from flat) in
> two days.   So in two days you need 96Wh to power the system and you need
> 360Wh to recharge the battery (240Wh * 1.5), so call it 460Wh in round
> numbers.   Here we re-introduce the loss from the PWM controller, so
> generation wise you need size your panels to generate 658Wh (460/.7).*
>
>
> *So working this backwards you need a 165W solar panel (658Wh / 2 days / 2
> hrs) and at least a 55Ah battery (685Wh  / 12.7) with a simple PWM charge
> controller for a 2W continuous load.  A little bigger than you first
> predicted."*
>
> 73
>
> Matt
> VK5ZM
>
> On Wed, 18 Dec 2019 at 12:20, Matthew Cook <vk5zm at bistre.net> wrote:
>
>> Marcus,
>>
>> With 2W continuous, your right it will be 48Wh/day.    It is wise to ask
>> someone how many days without sun they get at that location during the
>> middle of winter, usual answer is 3-5 days (for most of Australia ) then
>> work your Wh calculations on this... so 12-24Ah and a 18W solar panel I
>> think you'll find is light on, read on.
>>
>> When calculating the size of the solar panel you have missed a couple of
>> factors.   Solar panel output is specified at the MPTT point, with a basic
>> ON-OFF (bang bang) charger you lose 30%.   You also need to take into
>> account charge efficiency of the battery technology, so with a VRLA/SLA
>> battery you need to give them 35-50% more charge than you take out.
>>
>> So in the case of your 12Ah battery it is roughly 144Wh (DoD 100%) so to
>> recharge it this increases to 216Wh (144 x 1.5).    Now the Depth of
>> Discharge (DoD) of 100% in the above scenario will flog the batteries and
>> kill them in less than 12 months, you want to decrease this to something
>> like 50% (1.5 -3 years), 35% (3-5 years) or 20% (5-7 years).  Each battery
>> and manufacturer is different and obtaining info can be tricky but those
>> rough rules of thumb will do for this discussion.    It should be clear
>> this means the size of the battery will scale with how long you want it to
>> ultimately last.
>>
>> The major factor now is the effective number of days with no sun in your
>> chosen location.  Assuming 5 days of no sun we know our minimum battery
>> size is 240Wh (100% DoD), 480Wh (50% DoD), 685Wh (35% DoD) or 1200Wh
>> (20%).   To be honest 35% DoD is about the right balance (bang for buck),
>> so we know the battery will need ot be 55Ah or bigger (assume 12.7V
>> terminal voltage to 35%).
>>
>> Now in the middle of winter here in SA (S35-40deg lattitude) you receive
>> 2hrs equivalent of full sun, it's up to 7hrs in summer.  Where you are is
>> not that much further north, so times should be close to if not the same.
>>  So based on the number of cloudy days vs sunny days and we assume 5 days
>> cloudy is worst case, then you need to recharge the battery (from flat) in
>> two days.   So in two days you need 96Wh to power the system and you need
>> 240Wh to recharge the battery, so call it 340Wh in round numbers.   Here we
>> re-introduce the loss from the PWM controller, so generation wise you need
>> size your panels to generate 485Wh (340/.7).
>>
>> So working this backwards you need a 120W solar panel (485Wh / 2 days / 2
>> hrs) and at least a 55Ah battery (685Wh  / 12.7) with a simple PWM charge
>> controller for a 2W continuous load.  A little bigger than you first
>> predicted.
>>
>> With this solar configuration however you can expect 3-5 years out of the
>> battery, run for 5 full days of no sun with a recharge period of 2 days.
>>  You can expect an up time of greater than 95% in this situation.  You will
>> still need to use any low voltage cut out on your charge controller set to
>> 11.5V to prevent the DoD going too low on those rare events of 7 days of no
>> sun.
>>
>> Where you can tweak this down is by using a MPTT charger you can get away
>> with a 85W solar panel, you can flog your batteries and increase the DOD to
>> 50% and get away with a 40Ah battery (12V terminal voltage).   As you tweak
>> the DoD up you need to bring the terminal voltage down to get the effective
>> Ah.
>>
>> I've often thought about placing solar powered ARPS nodes along the
>> highway between Tailem Bend and Keith here in VK5, seeing as I know a lot
>> of the land holders in that region.  However when you put together what you
>> need to buy it gets a little pricey fast.    If you are seriously thinking
>> of putting those dorji modules on air take the time to protect them from
>> out of band signals and clean up their output, they aren't pretty.   I've
>> got a board you can tweak if interested here...
>> https://zedm.net/archives/97.
>>
>> Hope the above helps with your solar Analysis, I've done this a time or
>> two.  YMMV.
>>
>> 73
>>
>> Matt
>> VK5ZM
>>
>>
>> On Mon, 16 Dec 2019 at 20:20, Marcus B <mrmabs at gmail.com> wrote:
>>
>>> Yeah, I think a WIDE1-1 might be good, but the transceiver board may not
>>> be great at modulating audio.
>>>
>>> I might see if I can get a ladder onto the roof and mount it next to the
>>> TV antenna mast. That would also resolve the power issue as well, but at
>>> this stage I think roof access is unlikely. It's also a very old house, so
>>> there are safety issues as well.
>>>
>>> Raspberry Pi Zero W power consumption is a little over 0.5W (running
>>> direwolf may raise this slightly), the dorji board is about 0.2W on RX &
>>> 2.5W at 1W RF TX and that's about it. This is from datasheets and people
>>> who have measured these online. So all up, average should about 1W or
>>> 24Wh/day, or 2W max or 48Wh/day. 12A 12V is about 144Wh, let's say 72 hours
>>> to be conservative, and fixed 18W solar and minimum 9.75 hours of sunlight
>>> in winter should get in the region of 50Wh/day. In really bad weather for a
>>> few weeks, brownouts or blackouts are possible and without proper circuitry
>>> to manage power state, the pi could go into an unknown state. To partially
>>> tackle that, I would consider only having the SD card in read-only mode.
>>>
>>> And install, I would have to install it about the 2nd / 3rd Jan if I was
>>> going to do it, I'm moving to VK4 and it'll be on my trip up to there.
>>>
>>> 73,
>>> vk3tst / vk5wtf
>>>
>>> On Mon, 16 Dec 2019 at 06:30, Warren_Brown <warbn at telstra.com> wrote:
>>>
>>>> Hi Marcus,
>>>>
>>>> Yes I would have it transmit to VHF, you never know where it may get
>>>> heard.
>>>>
>>>> I would consider a Wide1-1 Digi also, just to provide local feedback to
>>>> anyone travelling through.
>>>>
>>>>
>>>>
>>>> As for antennas, any sort of gain would be good, whilst no real height
>>>> gain a roof top mount may be more study than a telescopic mast that you’re
>>>> only going to visit once in a blue moon.
>>>>
>>>>
>>>>
>>>> As for 12v power, the real killer will be the standby current, how much
>>>> does the gear use when Idle?
>>>>
>>>>
>>>>
>>>> How long before you plan to install it?
>>>>
>>>>
>>>>
>>>> Another option would be a satellite APRS Gateway
>>>>
>>>>
>>>>
>>>> 73,
>>>>
>>>> Warren vk3byd
>>>>
>>>>
>>>>
>>>> *From:* OZAPRS [mailto:ozaprs-bounces at aprs.net.au] *On Behalf Of *Jack
>>>> Schultz
>>>> *Sent:* Monday, 16 December 2019 09:26
>>>> *To:* Australian APRS Users
>>>> *Subject:* Re: [OZAPRS] Considerations For Setting Up an igate (RasPi)
>>>>
>>>>
>>>>
>>>> I won't comment on the hardware/operating environment considerations -
>>>> but my 2c is TX capability is much preferred - especially given its
>>>> location away from existing network coverage. The secondary benefit is
>>>> another tropo indicator.
>>>>
>>>>
>>>>
>>>> Another thing I will note is that VK3RMK-1 is not the most reliable
>>>> indicator of traffic - at a guess it is down most of the time. VK3RCU-1 may
>>>> be a better indicator but most of your traffic will be Murray Valley
>>>> Highway, so no source of data that picks up those who might travel out to
>>>> Cohuna. I drive to Kyabram (from Geelong) quite regularly and lose reliable
>>>> digipeater coverage around Nagambie, so if I travelled up to Swan Hill from
>>>> there (for example) I wouldn't get a single ping out under normal
>>>> conditions. So there may be more traffic passing through than you might
>>>> guess. Similarly VK3REG-1 in East Gippsland has significant downtime, so
>>>> misses a lot of the would-be traffic through the area.
>>>>
>>>>
>>>>
>>>> On Sun, Dec 15, 2019 at 11:58 PM Marcus B <mrmabs at gmail.com> wrote:
>>>>
>>>> Hey all,
>>>>
>>>>
>>>>
>>>> I had a thought bubble, probably unlikely to have time to pull this
>>>> off, but you never know. So right now we'll treat this as an intellectual
>>>> exercise, with a chance it might actually happen.
>>>>
>>>>
>>>>
>>>> A couple of months ago travelling through northern Victoria I noticed a
>>>> lack of coverage (between Robinvale & Shepparton), and thought about
>>>> setting up a small igate at a relative's place in Cohuna. If I did this I
>>>> would be doing it just after the new year, and I won't be able to visit to
>>>> maintain it potentially for 10 to 24 months. It's also unlikely that I
>>>> would go to the trouble to open a remote port to ssh in, so must be
>>>> reliable hardware and software wise. I have access to WiFi.
>>>>
>>>>
>>>>
>>>> What I have today: Pi Zero W with a protoboard to connect TTL serial to
>>>> a dorji board + LDO regulator, and a usb sound card. Also have 4.5m Jaycar
>>>> telescopic mast and I could put a DIY 1/4 wave on top. Also, the further
>>>> away from the house, the better, so that means, if possible, run off its
>>>> own power. Maybe a 12V 12A SLA & 10W or 18W solar panel will do the job?
>>>>
>>>>
>>>>
>>>> I have not done much TX testing, RX seems to work fine.
>>>>
>>>>
>>>>
>>>> It's pretty flat out there, so at 4.5m above ground, I may expect about
>>>> 5-10km coverage (running on HeyWhatsThat.com confirms that it would be a
>>>> very patchy to the west, and then there's the trees, and house roofs), and
>>>> unlikely to hear anything on 145.175 unless some serious tropo comes in. I
>>>> can also look up how to get up an igate with direwolf easy enough. In
>>>> reality I might be lucky to hear one station a month given the reports I
>>>> have seen for VK3RMK-1.
>>>>
>>>>
>>>>
>>>> How should I set this up, purely as an RX only igate? I have also
>>>> considered just getting it to TX occasionally (30mins?) just to say hello,
>>>> but at 1W eh... At this location in about 1996 I was able to have a
>>>> scratchy QSO on VK3RMM on 5W (HT) using a CFA 160MHz 1/4 wave at 10m; so
>>>> it's not all doom and gloom. That 10m was a solid steel pipe and it is
>>>> looooong gone.
>>>>
>>>>
>>>>
>>>> With all that, what could I do to make this set up better? Best bang
>>>> for buck? (Obviously the dorji modules are pretty low quality.) Location is
>>>> pretty much fixed. What about to improve reliability? Best ways to protect
>>>> from heat (does it need it)? What sort of protection (power, temperature,
>>>> etc...) should I consider?
>>>>
>>>>
>>>>
>>>> What else am I not thinking about?
>>>>
>>>>
>>>>
>>>> Maybe, alternatively, I could make a 2m WSPR beacon on a Pi with filter
>>>> and attach a GPS :P
>>>>
>>>>
>>>> 73,
>>>>
>>>> vk3tst / vk5wtf
>>>>
>>>> _______________________________________________
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>>>>
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> VK3FJTS
>>>>
>>>> Jack Schultz
>>>> _______________________________________________
>>>> OZAPRS mailing list
>>>> OZAPRS at aprs.net.au
>>>> http://lists.aprs.net.au/mailman/listinfo/ozaprs
>>>>
>>>
>>>
>>> --
>>> "The universe is an intelligence test." -- Timothy Leary
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-- 
"The universe is an intelligence test." -- Timothy Leary
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