Re: SB II build project


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

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