Topics

SB II build project

John VA7JBE
 

As I eagerly await the delivery of a shiny new Slop Bucket kit I've been imagining the specifics of how I'd like to box it up.  I'll be using it almost exclusively portable for SOTA, which helps to clarify some of my design goals, and on that note I have a few thoughts/questions I'd like to run by the group.

Power Supply
I plan on using 4x 18650 lithium cells as the power source, if I swap out the 16v electrolytic capacitors for 25v versions would it be appropriate to use an input voltage of 16.8v?  I'm also planning to change the protection diode for a P-channel mosfet (see fig 5 https://www.maximintegrated.com/en/app-notes/index.mvp/id/636) in order to avoid any voltage drop.  The extra RF output would probably be quite small, but it would extend operating time slightly which would be beneficial while trying to activate in cooler weather. 

In regards to the batteries, is it worth picking up one of the many inexpensive BMS boards I see on various Chinese marketplace sites?  Also, would I need a separate balanced charger module if I wanted to charge the batteries internally?  I'm hoping to wind up with a transceiver that could be used for a while without opening it up.

Enclosure
I found a neat 44x100x100mm enclosure that should reduce volume a bit compared to the 50x100x100mm cases and also have enough space for the SB II and four 18650 lithium batteries.  I had looked at using a 30x100x100mm case with some flat lithium cells I found on battery space, but it would have been a tight squeeze and frankly I'm more comfortable with cylindrical cells that are already inside a metal case.  Here's the link to the enclosure:  https://www.aliexpress.com/item/1-piece-szomk-electrical-aluminum-instrument-enclosure-project-case-for-pcb-broad-44-100-100mm/32574589643.html

While we're at it, any advice on how to weatherproof something like this would be greatly appreciated.  I don't expect it to be water tight, but I'd like it to withstand a bit of rain and damp weather.

Voice compression
I have a few small voice compression modules kicking around based on the SSM2167 and thought I might try to integrate one into this kit for a bit of extra punch.  These are the next generation of the same chips used in some popular compression modules made for the FT-817, though those ones follow up the compressor with a basic amplifier.  At this point I'm not sure if I'd have to do the same with the slop bucket, though I imagine I'll find out while determining the correct compression ratio (not too much!)

SWR meter/Antenna tuner
If there's any space left over it would be nice to include something like the TinySWR board designed by DK3IT (https://github.com/mfhepp/tinyswr).  It would also be nice to have some sort of tuner for high impedance antennas, though I strongly doubt there would be any room with all the other stuff that's crammed in there.  This will definitely have to be a 'wait and see' addition once everything else is in there.

Cheers,
John VA7JBE

ajparent1/kb1gmx
 

John,

Looking forward to getting mine.  My 20M SB-I gets a lot of use.
I like that there is a simple agc, makes tuning around the band less painful.

I  run the SB 1 on 3S1P (2800mah) or 3S2P (5000mah) pack of Lipo 18650s
as that hits the working range and easily nets 7-8W at 20M.   Teh SB-I was
designed very much similar to SBII for 14V max.  I also considered more
voltage but for most usage the advantage is near negligible and not worth
the stress and weight.

Note the assumption is LiPO at 4.2V full charge and 3.7V nominal at discharge.
The extra voltage is a stress factor.   The A123 and LiFePo types that is more
like 3.75 and 3.2V and not a concern.

So changing a few caps will not only be needed it may require a dropping resistor
for U1 so it does not overheat.  Its also rated to a max input of 18V so you pushing
close to the design limit.  So pushing the voltage 2.8V (at full charge) over max is 
not a good thing for a lot of the circuitry exposed to unregulated voltage.

I've used the SSM2167 and if  the levels are right and the compression reasonable
it works well without undue distortion.  I found the radio was plenty effective without it.
I left it out as then it was just one more piece that needed power.  I may include it in
a Mic and set it to the same levels are a standard electret mic would put out.

The use of Pmos diode will buy milliwatts maybe and will not buy operating time over
the schottky diode.  This is not the FT817 as it doesn't suck down 400mA on RX. 
The 40-50ma RX makes 10 AA 2200mah NiMh practical.   Running 3S LiPo you
will get 50-60% of the battery before you get under 11V and for 4S LiPo you will
run the battery to cutoff (very bad thing to do) before the radio quits.  That would
also be the same case for 4S A123 or LifePo.  The power consumption for this will
be unlike the  FT817 if that is why your doing this.

Package I've used is a wood (copper foil lined), craft box with decent latches and hinges 
large enough that the radio is half the box and everything (Mic, antenna (EFHW 20M), 
battery, small Key) fits with space to spare.   Packaging it that way and shoulder strap 
its grab and go portable and complete.  Its not the smallest possible case but convenient
and cheap and durable.

For SWR indication I went with the KITSANDPARTS.com SWR detector and a real
100uA (tiny) edgewise panel meter.  SWR is just for a check and also monitoring
power. No tuner as the antenna is tuned already.  If needed a Zmatch or my T1
does the trick.  All that in its own pouch for use with any radio I have.

I have a larger assortament of QRP radios including FT817, SB-I, KNQ7A,
Tentec 505 (QRP 5W), and 5 others SSB of my design for HF.  

Allison

John VA7JBE
 

Thanks Alison, that's very helpful! 

Since I'll definitely be using this transceiver outside during the winter I'm tempted to stick with a 4S configuration for the sake of not getting caught short on power in the event that I can't keep the batteries warm overnight (this has happened to me before: https://summitsandradios.wordpress.com/2018/04/11/return-to-garibaldi-ve7-sl-009/).  Instead of shoving the full 16.8v into it, however, given your advice it seems prudent to leave the protection diode in place and maybe use a regulator, or even a second diode, to protect the radio.  Arguably I'll only need an hour or two of operating time out of it, facilitated greatly by the 50mA receive current, so maybe I can get by with 60% of a 3S battery pack.  I'll have to do some testing on this.  Maybe there's a 'winterized' configuration that I could use for half the year. 

Cheers,

John VA7JBE

ajparent1/kb1gmx
 

Mine should be here sometime today...  YEA!

The SB-1 was a fun build and looking to enjoy the SB-II.

As soon as I read Garibaldi I knew cold was the issue.

The big issue is the cold.  Radios don't like it and batteries of any type rebel.
Keeping the batteries warm or warming them works.  Even the dead appearing
ones if fully charge will come right back once warm.  So capacity is not the issue
but managing temperature.  To that cylinder cells (AA, 18650) are best choice
and thermal bag with a hand warmer I keep them on the body and that makes
a huge difference.  Seems the threshold for batteries going to sleep is in the
low 40s (F) getting them to mid 50s or warmer seems to make them happier.

The upside with cold batteries is they are not dead just cold and the self discharge
when cold is not an issue.  So warm them and they are 100% again.

Keeping a 3S or 4S pack inside my coat is not problem.  Even my larger 3S4P
(11AH) for the FT817  only weighs under 3 pounds and fits in pants or coat
pockets.

The radio needs to be kept warm as sharp temperature transitions can be hard
on components internally and soldering in general.  Plastics tend to shatter
when extremely cold (below about 20F).  LCD displays many quit working
when that cold and colder can destroy them.  The sun can be helpful so a
black outside is a plus.

Allison

John VA7JBE
 

Thanks Allison!

Yes!  The cold absolutely changes the game.  I had a chance to ponder this yesterday while I was operating on Columnar Peak in -17C (1,100m vertical gain/loss, 28km round trip, strong winds on the summit.)  It's an environment where taking care of yourself is a priority over taking care of the radio and practicality dictates some unusual operating practices.  For example, doing everything while wearing heavy winter gloves or just throwing half the dipole on the snow when you can't get one of the end supports to stay up.  Getting the operating time down to <30 minutes also helps to limit the exposure, so simplifying the set-up/tear-down process is vital.  I'm encouraged that the Nokia 5110 display is already rated down to -20C (-4 F), though there are a couple of other components I worry about that I'll discuss below.  So with that in mind here are a few of the things I came up with in regards to the new build:

Power
I'm happy to hear that cylindrical cells are the right decision for batteries.  As much as I'd love to be able to reliably keep a battery pack warm for these things it's often not practical, especially on 6-hour approaches or multi-day trips.  To that end I'd like to experiment with a starter-battery approach to this and just overbuild the power source.  For an internal battery (which I prefer to an external battery to reduce setup time on the summit) I'll start out with 4S 18650 lithium cells through a 14v regulator.  This should give me enough power in cold weather to do some transmitting and get the unit to start self-warming without being too hard on the radio components.  If things get really bad I might think about adding a small resistive heating element around the battery that I can just turn on in the parking lot.

Connectors/Buttons/Knobs
Heavy gloves are a must in extreme temperatures, especially considering my history of cold-related injuries in the past (I'm still waiting for all the feeling to come back in the fingertips of my left hand.)  BNC connectors are definitely easier than others, but I'm now revisiting the idea of including an EFHW tuner internally and then using a banana or RCA connector.  This might be useful in parallel with a BNC connector for added flexibility in other situations. 

The button and knob will also need to be easily manipulated with gloves while also being at least somewhat weatherproof.  I'm still looking for the right parts, but they'll need to be able to withstand some light rain or melting snow. 

Frequency Drift
In the interests of reducing the amount of time exposed to summit conditions I'm considering using a TCXO with the Si5351.  With any luck this would eliminate the warm-up period and make it easier for other stations to receive the signal from a (very) compromised antenna.  This is a problem I encountered with my FT817 in temperatures as mild as 5C (41f), where the receiving stations were constantly having to adjust to match my drift.  Ever since I added a TCXO module I haven't had that problem again. 

Recording
Due to the high winds and cold temperatures I couldn't get my logbook out to make any records.  Fortunately I was able to enlist a local operator who could hear me on 20m and was able to copy down my QSO details for me (big thanks to Keith VE7GDH!)  It did cause me to consider adding a tiny MP3 recording module internally so that I can retrieve the information later.  There is a module like this that is also Arduino compatible, the only downside is that it would pull more than 20mA from the power supply.  However, given the already low power consumption of the radio in receive, I might be able to live with it. 

MP3 Module: http://www.electronics123.com/shop/product/fn-rm01-high-quality-mp3-audio-recorder-and-player-module-8227


Case Color/Insulation
Thanks to Allison for the advice on painting the case a dark color to facilitate some warming by the sun (at least when it's sunny!)  I may also try to stitch up a transceiver cozy (or soft-case, if you will) for non-sunny days.


If anyone else has any thoughts on these topics (or others) then please feel free to jump in!  I'm always looking for new ideas.

Cheers,

John VA7JBE

Joe Street
 

What I have found very useful is a pair of thin neoprene gloves that give dexterity and extend the working time without the overmitts.  It is really just a case of extending the layering approch to the hands.  Also the neoprene acts as a vapour barrier and helps keep your insulating layer dry.  For overmitts I generally go with a low adsorbent type like polar fleece and then a gore-tex outer shell mitt.  For a key I srink wrapped a microswitch to the end of a popsicle stick which allows one to hold the stick with mitts and tap the switch actuator on any hard surface for keying but you are building an SSB rig so that is probably irrelevant but I thought I'd mention it as food for thought.


On Mon, Feb 11, 2019 at 1:34 PM John VA7JBE via Groups.Io <va7jbe=yahoo.com@groups.io> wrote:

Thanks Allison!

Yes!  The cold absolutely changes the game.  I had a chance to ponder this yesterday while I was operating on Columnar Peak in -17C (1,100m vertical gain/loss, 28km round trip, strong winds on the summit.)  It's an environment where taking care of yourself is a priority over taking care of the radio and practicality dictates some unusual operating practices.  For example, doing everything while wearing heavy winter gloves or just throwing half the dipole on the snow when you can't get one of the end supports to stay up.  Getting the operating time down to <30 minutes also helps to limit the exposure, so simplifying the set-up/tear-down process is vital.  I'm encouraged that the Nokia 5110 display is already rated down to -20C (-4 F), though there are a couple of other components I worry about that I'll discuss below.  So with that in mind here are a few of the things I came up with in regards to the new build:

Power
I'm happy to hear that cylindrical cells are the right decision for batteries.  As much as I'd love to be able to reliably keep a battery pack warm for these things it's often not practical, especially on 6-hour approaches or multi-day trips.  To that end I'd like to experiment with a starter-battery approach to this and just overbuild the power source.  For an internal battery (which I prefer to an external battery to reduce setup time on the summit) I'll start out with 4S 18650 lithium cells through a 14v regulator.  This should give me enough power in cold weather to do some transmitting and get the unit to start self-warming without being too hard on the radio components.  If things get really bad I might think about adding a small resistive heating element around the battery that I can just turn on in the parking lot.

Connectors/Buttons/Knobs
Heavy gloves are a must in extreme temperatures, especially considering my history of cold-related injuries in the past (I'm still waiting for all the feeling to come back in the fingertips of my left hand.)  BNC connectors are definitely easier than others, but I'm now revisiting the idea of including an EFHW tuner internally and then using a banana or RCA connector.  This might be useful in parallel with a BNC connector for added flexibility in other situations. 

The button and knob will also need to be easily manipulated with gloves while also being at least somewhat weatherproof.  I'm still looking for the right parts, but they'll need to be able to withstand some light rain or melting snow. 

Frequency Drift
In the interests of reducing the amount of time exposed to summit conditions I'm considering using a TCXO with the Si5351.  With any luck this would eliminate the warm-up period and make it easier for other stations to receive the signal from a (very) compromised antenna.  This is a problem I encountered with my FT817 in temperatures as mild as 5C (41f), where the receiving stations were constantly having to adjust to match my drift.  Ever since I added a TCXO module I haven't had that problem again. 

Recording
Due to the high winds and cold temperatures I couldn't get my logbook out to make any records.  Fortunately I was able to enlist a local operator who could hear me on 20m and was able to copy down my QSO details for me (big thanks to Keith VE7GDH!)  It did cause me to consider adding a tiny MP3 recording module internally so that I can retrieve the information later.  There is a module like this that is also Arduino compatible, the only downside is that it would pull more than 20mA from the power supply.  However, given the already low power consumption of the radio in receive, I might be able to live with it. 

MP3 Module: http://www.electronics123.com/shop/product/fn-rm01-high-quality-mp3-audio-recorder-and-player-module-8227


Case Color/Insulation
Thanks to Allison for the advice on painting the case a dark color to facilitate some warming by the sun (at least when it's sunny!)  I may also try to stitch up a transceiver cozy (or soft-case, if you will) for non-sunny days.


If anyone else has any thoughts on these topics (or others) then please feel free to jump in!  I'm always looking for new ideas.

Cheers,

John VA7JBE

John AE5X
 

ajparent1/kb1gmx
 

Here big hills are rare her and most plain unsafe in winter.  We have
Mt Washington for that and it has a history as well.

Winter in the Poconos at 1500ft and -20F was enough cold for me.
Things break that not thought fragile and other things glue together
like tires to mud.  I've had things like the grease used on radio
switches and controls get so stiff things break ir at least don''t turn.  

Not a big fan of the cold but New England does that occasionally.

So dry runs in the cold but not hours out in the field to test things are advised..
I've tossed gear out in the cold to soak overnight to see what they do... or don't do.
We only got to -3F last week so its a good test. 

Look into what batteries work best when cold: Battery University:  https://batteryuniversity.com/
Experience with the expensive but very good when cold lithium primay cells (NOT rechargeable)
has been good to below 0F.  LIpo and NiMh are ok to 0F if you can keep them that warm.

TCXO will marginally help with drift.  They have limits too.  Drift is
not like a old school VFO.  The FT817 has a much more involved
PLL system and multiple conversions (one an up conversion to VHF)
so drift in actually much much more pronounced.  That and the
oscillator for the FT817 is where it could be put, and near the outer
edge of the case near the power amp mans it also sees greater
temperature changes.   That helped thermally cripple it making
a TCXO more important even for room temp.  Try QCX it first
without TCXO.  

The cozy has the function of keeping the wind and possible moisture off the
unit.  A case or a sack works.  If its big enough it can be a mitt or muff
with the radio inside, your hand or both hands are not directly exposed
and helps warm the radio.

Still the inside pockets of my parka or jacket has been the prime spot for 
gear needed to work when cold as I have this bio-heater (my bod)
that radiates heat like mad.  To a radio or battery -5F is warm compared
to -20F.

To keep buttons from getting wet, plastic film that doesn't get brittle or stiff.
Tall order but it can be done.  

Antenna, you already have height and likely a wire on the ground if long
enough is a winner.  Having played with a wire earth without deep snow
I know its viable and not that terrible.   Snow is an odd material as its
an insulator mostly.  The trick at best is not to use a shortened antenna
for example a 20ft wire on 40M where a 66ft with a tuner might be better
even if stretched out on snow.   Again test at local ground level and find
out what can be heard best 50 miles or more away.  FYI the best easy
install antenna tried was 150ft of wire on top of 4-5ft of snow one winter
for 160M, it loaded well and was a full S unit better locally then when it
was on the dirt literally.  For 80M a 100ft wire on the snow made a good
NVIS antenna.  For higher than about 5mhz forget NVIS the ionosphere
is a bit thin this part of the cycle.

In the end do everything you can from near the back door to test without
frostbite, then when on the hill, your already set and have tried it, maybe
several different ways.

Allison

John VA7JBE
 

Thank you Alison, John, and Joe!

 

I've been away working for the last few weeks and unfortunately won't get a chance to start building for a few more.  The upside is that I get to obsess over details in my free time!

Joe, good advice on layering the gloves/mitts.  I have a similar approach, though I tend to have dedicated gloves for getting sweaty going up and then getting colder skiing down.  Making the micro switch glove friendly is an excellent idea, I might have to try that once i get more comfortable with morse.  I'm new enough that I need a comfortable, low-pressure environment to send/receive comfortably and that means summer.  I have a QCX that I've been playing with just for that purpose.  I even modified it to draw 75 mA on receive!

 

John, thanks for the link!  I went with the 100x100x44mm box for the extra depth (not much, admittedly, but enough to provide a bit of wiggle room with the batteries.)  It's arrived from China already and it looks like it will be small and light enough to be worth bringing on multi-day trips, which I'm very excited about!  I really like this idea of designing boards to fit inside these enclosures and there seems to be enough variety that designers have don't feel too much pressure to conform to any one standard.

Alison, informative as ever!  Thanks so much for the information about the TCXO and also the 817, that had been bothering me for a while.  There's an old trick SOTA operators in the UK have been doing for years to keep their radios splash proof, and that's to use a clear disposable shower cap placed over top of the radio while operating.  I might start there.  This enclosure seems small enough to fit in my jacket pocket so I'll be able to add that to my list of ways to keep the batteries warm. 

Through some extensive, and somewhat random, browsing on wikipedia I discovered Lithium-Titanate batteries, which have a temperature operating range down to -30C in addition to higher charge/discharge rates, greater cycle life, and being much more environmentally friendly than other lithium chemistries.  The downside is that they have a lower energy density and inherent voltage (2.4v/cell) than lithium ion cells, though still better than nickle chemistries.   They are also more expensive at $13 for a 1300mAh 18650 cell from battery space (link: https://www.batteryspace.com/Lithium-Titanate-Battery.aspx ).  I may or may not explore this option at a later date.  For now it's just fun to think about. 

 

Thanks again to everyone, I'll keep posting developments as they happen!

Cheers,
John VA7JBE

 

#127 is finished and fully functional!  6 1/2 watts and receives well.  Housed in a cut down Hammond 1455P160 case. I'm a happy camper!
Your mileage may vary,
Jim W0CHL

Roy Appleton
 

Looks really nice!

Roy
WA0YMH

On Wed, Mar 6, 2019, 8:42 AM Jim Reagan <jimreagans@...> wrote:
#127 is finished and fully functional!  6 1/2 watts and receives well.  Housed in a cut down Hammond 1455P160 case. I'm a happy camper!
Your mileage may vary,
Jim W0CHL

John AE5X
 

Looks absolutely professional. I applied power to mine for the first time today and now the troubleshooting begins ;-(

John VA7JBE
 

Nice build, Jim, very clean!

cheers,
John VA7JBE 

John VA7JBE
 

Quick update, I now have all the ICs on the board!  I was hoping to have the whole thing together by the time I left for a 10 day expedition at the beginning of April that would put me near some fairly remote SOTA summits, but unfortunately life got in the way and my activator dreams were cut short.  Not to worry, thought, mountaineering season is right around the corner and I have a bit of spare time coming up!

 

Cheers,

John VA7JBE

John VA7JBE
 

Nearly all of the surface mount parts are on the board!  I accidentally sent one of the 4.7 uH inductors flying and it has now been sacrificed to the god of missing components.  The missing spot is at L5, which is a shunt inductor, so I should be able to get the rest of the board working while I wait for a new one from digikey.  Speaking of, any guidelines on which part I should order?  Tolerance, current rating, shielding, etc? 

I'm going to try and do the through hole components this evening and then I'll apply some power and see what happens!

Cheers,
John VA7JBE     

Don, ND6T
 

Totally non-critical. It's just an RF choke for the audio. No supply current.

John VA7JBE
 

Thanks Don!

I got the through hole components done tonight and applied some power.  The screen backlight flashed briefly and then nothing was displayed.  I haven't pulled out the DMM to really get into it, but I suspect that I may need to check the solder bridge between Q22 and ground.  Either way I'll have a look at it in the morning.  Otherwise it looks like a pretty clean build!

Cheers,
John VA7JBE

Don, ND6T
 

John,
Lotta help that I am! My bleary eyes must have been looking elsewhere, sorry! I was referring to L6 obviously. L5 is one of the tuning inductors for the receive band pass! My documentation shows it to be 10 uH. No shielding or current rating needed but it really needs to be 10 uH (if I'm reading correctly). You could temporarily use the L6 inductor (same rating) and just jumper where L6 is until you get things working.

That, of course, doesn't help your power problem. Check that 3.3 volt bus and the rest of the voltage points for that.

Again, I am so sorry. The "shunt" statement should have given it away. No excuse for my inattention, John.

John VA7JBE
 

No worries, Don.  I'm building the 20m version and the manual lists the 4.7uH values for L1-5 for that band, so that's what's in the mail!

Cheers,
John VA7JBE

John VA7JBE
 

The screen lives!  Turns out I had it installed upside down (oops!). A friend of mine with a frequency counter (an old Heathkit IM-2420) helped me calibrate the crystal, which was only 87Hz off, but I'm encountering something interesting when I try to adjust the PA bias.  Maybe it's because I'm just shorting Mic/Gnd/PTT but I only see 110 mA on the DCC with the bias pot all the way CCW.  When i adjust it, it climbs very slowly to 122 mA then shoots up to more than 300 mA suddenly.  I'm not entirely sure what to make of that, has anyone else encountered anything like this? 

Otherwise I'm pretty stoked with the progress so far!

Cheers,
John VA7JBE