Mark Conrad wrote in :

Wonder if any hams are experimenting with liquid nitrogen cooled
RF front ends to their rigs, to reduce thermal noise.

With the high background noise floor already present on Earth, would he
few tenths of a dB or so of thermal noise reduction from cryocooling
make any perceptible or significant difference? Above HFis a different
story, I think, but the noise floor on HF -- at least around here -- is
really rottenly high.

--
Mike Andrews, W5EGO

Tired old sysadmin

Mark Conrad wrote:


If one rig stands out head and shoulders above others for CW work,
then I would be strongly tempted to favor that rig.

(assuming of course diversity antennas to minimize fading)

Playing with CW is just a personal choice, in my case.

Mark

That would be the K3.

http://www.sherweng.com/table.html

Stuart Longland VK4MSL wrote:

My only gripe is that Yaesu for some reason decided that it would use
NiMH cells in its battery packs... Li-ion would have been lighter and
higher density. Heaven forbid, gel-cell batteries would do better
than NiMH! But that's the choice they went with, and we all have to
live with it.

It's because lithium cells are a disaster waiting to happen. If you charge
them improperly they will catch fire. If you discharge them to "empty" they
are permanently dead.

They also die after around 300 charge cycles. ANY power put in is a charge
cycle, so laptops made in the last couple of years will no longer "float"
a lithium battery. They let it discharge to at least 95% left before
recharging it.

The latest NiMH batteries will go through 1000 cycles. Compared to litium
batteries they are bulletproof. They are also a lot cheaper.

The main reason they are so common is that people don't understand their
problems and like them because they are so light in comparison to
NiMH cells. The lightness disapears when you find out a 450mAH battery will
be trash if you use it anywhere near that amount.

BTW, they are dangerous corosive trash, much worse than NiMH cells.

Companies like them because they can claim the device has a long battery
life, low weight and in 6 months to a year be back buying a new battery.
Since the battery is proprietary at best and permanently installed at worst
it's a win win for them either way.

The bigest problem I have with NiMH batteries is that they no longer sell
large size batteries to the general public. Yes you can get real C or D cells
from battery specialists (which are rare here), but generally all you can get
is AA batteries or C or D cells which are just sleeved AA cells (with the
corresponding capacity).

I would not mind if I could get the sleeves, but no one carries them here. :-(

After all, in my 290RII which takes a lot of C cells, sleeved AA batteries
with 2700mAh capacity would far out last the NiCad ones I had in it.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation.
i.e possessing less facts or information than can be found in the Wikipedia.

On Mar 21, 3:54*pm, "Geoffrey S. Mendelson"
wrote:
Stuart Longland VK4MSL wrote:
My only gripe is that Yaesu for some reason decided that it would use
NiMH cells in its battery packs... Li-ion would have been lighter and
higher density. *Heaven forbid, gel-cell batteries would do better
than NiMH! *But that's the choice they went with, and we all have to
live with it.

It's because lithium cells are a disaster waiting to happen. If you charge
them improperly they will catch fire. If you discharge them to "empty" they
are permanently dead.

Well, there are several types of Lithium ion battery. Some are
chemically unstable, such as Lithium-Cobalt, and are prone to taking
off thermally. Then there are others which are far more inert, such
as LiFePO4.

Any battery will die or explode if abused, lithiums and NiMH cells are
not immune to this.

They also die after around 300 charge cycles. ANY power put in is a charge
cycle, so laptops made in the last couple of years will no longer "float"
a lithium battery. They let it discharge to at least 95% left before
recharging it.

The latest NiMH batteries will go through 1000 cycles. Compared to litium
batteries they are bulletproof. They are also a lot cheaper.

Many of the cells on the market are well past the 1000 cycles.
Particularly in the electric vehicle sector (which is where I'm
employed at present).

The main reason they are so common is that people don't understand their
problems and like them because they are so light in comparison to
NiMH cells. The lightness disapears when you find out a 450mAH battery will
be trash if you use it anywhere near that amount.

BTW, they are dangerous corosive trash, much worse than NiMH cells.

Companies like them because they can claim the device has a long battery
life, low weight and in 6 months to a year be back buying a new battery.
Since the battery is proprietary at best and permanently installed at worst
it's a win win for them either way.

Again, I see these batteries used in far more demanding environments
than portable HF radios, and see them outliving that 6 month
boundary. Indeed, my netbook, which runs about 15W off a 3-cell Li-
ion pack, had about 1.5 hours battery life when I bought it about 2
years ago... and still has much the same capacity now.

In the case of the FT-897... the battery packs are proprietary in
nature, and I've found NiMH cells don't last as long for me as Li-
ion. So I'll probably find myself coming back to Yaesu for more when
the two I have sign their resignation letters.

The bigest problem I have with NiMH batteries is that they no longer sell
large size batteries to the general public. Yes you can get real C or D cells
from battery specialists (which are rare here), but generally all you can get
is AA batteries or C or D cells which are just sleeved AA cells (with the
corresponding capacity).

I would not mind if I could get the sleeves, but no one carries them here.. :-(

After all, in my 290RII which takes a lot of C cells, sleeved AA batteries
with 2700mAh capacity would far out last the NiCad ones I had in it.

Yeah, I guess they don't see a market for the C/D cells in your
area... which is a shame. Interestingly...
http://www.jaycar.com.au/productView...SUBCAT ID=583
http://www.jaycar.com.au/productView...SUBCAT ID=583
http://www.dse.com.au/cgi-bin/dse.st...uct/View/S3163
http://www.dse.com.au/cgi-bin/dse.st...uct/View/S3169

The latter two being from a mob run by the supermarket giant,
Woolworths. (Dick Smith Electronics is pretty much useless these
days. My FT-290RII was originally bought from DSE many moons ago,
these days they barely sell CB gear. Woolworths ruined both them, and
Tandy Electronics.) I think they still sell them in their
supermarkets too. So they're still in the "easily obtainable"
category here in Australia. I understand the situation could be quite
different in the US.

In article writes:

It's because lithium cells are a disaster waiting to happen. If you charge
them improperly they will catch fire. If you discharge them to "empty" they
are permanently dead.

Fortunately there are new Li chemistry designs that don't seem to catch
fire/explode.



They also die after around 300 charge cycles. ANY power put in is a charge
cycle, so laptops made in the last couple of years will no longer "float"
a lithium battery. They let it discharge to at least 95% left before
recharging it.

Hmmm. My cellphones (with Li batteries) have somewhere in the 1000 cycle
range on them now, and are still going strong.


The last laptop I bought (3 months ago), charges when connected to power,
without waiting for a discharge. Waiting for a discharge just leaves you
dead if you disconnect at the wrong time in the cycle.




The bigest problem I have with NiMH batteries is that they no longer sell
large size batteries to the general public. Yes you can get real C or D cells
from battery specialists (which are rare here), but generally all you can get
is AA batteries or C or D cells which are just sleeved AA cells (with the
corresponding capacity).

I would not mind if I could get the sleeves, but no one carries them here. :-(

After all, in my 290RII which takes a lot of C cells, sleeved AA batteries
with 2700mAh capacity would far out last the NiCad ones I had in it.


Actually, C and D size NiMH seem pretty rare here, except by mail order.
Presumably, mail order works there.

Alan
wa6azp