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POW Receiver

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k6dgw

POW Receiver

Off topic, I apologize, but I want to tap the knowledge pool in this
group, and I'll continue regardless:

I'm involved with a 6th grade teacher (a ham, he bought my TS830 a few
years ago) at a local, sort of disadvantaged school. He's trying to
find ways to reach his kids, and ham radio has worked out pretty well so
far with QSO's with a class in Portland OR via 2m and IRLP. I've
offered to help him.

I know the recipe for a "POW Radio Receiver" -- some wire in an
inductor, a capacitor made from rolled up gum wrappers, and a pencil
lead on an anodized razor blade, with some stolen headphones, and as new
hams in the late 50's, my buddies and I built these and listened to KFI.
His kids and he think this would be a great project. We won't hear
the WW2 BBC, but we might hear KFBK if we can make it work.

A couple of problems:

1. Razor blades have changed from the "Gillette Blue Blades" of yore.
Can I still get them?

2. "Razor blades" and "campus" don't sound like they belong in the same
sentence. Any suggestions for substitutes that would pass the "campus
security test?"

3. Any other info anyone might have to help me to, at the beginning of
the 21st century, recreate for these kids something from the middle of
the 20th century (when their parents' hadn't yet been conceived).

There's a lot of learning to be had here ... history, reading, learning
how to sequence the steps of a project, and satisfaction in achievement,
and these kids are lacking in nearly all of these things. I wouldn't
attack this if I didn't have a Real Teacher in charge.

Thanks in advance,

Fred K6DGW
Auburn CA CM98lw

PS: We may get some young hams out of this.
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Margaret Leber

Re: POW Receiver

Fred Jensen wrote:

> 2. "Razor blades" and "campus" don't sound like they belong in the same
> sentence. Any suggestions for substitutes that would pass the "campus
> security test?"

Things sure have changed since I was on the rifle team in college. I
don't recall the men shaving much back then though. Or the women, come
to think of it.

You could always take a Dremel and dull the edge; they don't have to be
sharp to rectify.

Further resources:

http://www.midnightscience.com/
http://www.schmarder.com/radios/crystal/

Maggie K3XS K2 1641

--
-----/___. _)Margaret Stephanie Leber CCP, SCJP/"The art of progress /
----/(, /| /| http://voicenet.com/~maggie SCWCD/ is to preserve order/
---/ / | / | _ _ _ ` _ AOPA 925383/ amid change and to /
--/ ) / |/ |_(_(_(_/_(_/__(__(/_ K3XS / preserve change amid/
-/ (_/ ' .-/ .-/ ARRL 39280 /order."-A.N.Whitehead/
/________________(_/_(_/_______AMSAT 32844_/<[hidden email]>/

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David Toepfer

Re: POW Receiver

I did some reading recently about the "blue blades". Some suggested that you
could get some of the effects/benefits of the blue blade coating by simply
talking a match/lighter to a normal razor blade. The oxidation and bluing of
the blade that results is said to work well. I have not had a chance to try it
out.

dt
.

--- Margaret Leber <[hidden email]> wrote:

> Fred Jensen wrote:
>
> > 2. "Razor blades" and "campus" don't sound like they belong in the same
> > sentence. Any suggestions for substitutes that would pass the "campus
> > security test?"
>
> Things sure have changed since I was on the rifle team in college. I
> don't recall the men shaving much back then though. Or the women, come
> to think of it.
>
> You could always take a Dremel and dull the edge; they don't have to be
> sharp to rectify.
>
> Further resources:
>
> http://www.midnightscience.com/
> http://www.schmarder.com/radios/crystal/
>
> Maggie K3XS K2 1641
>
> --
> -----/___. _)Margaret Stephanie Leber CCP, SCJP/"The art of progress /
> ----/(, /| /| http://voicenet.com/~maggie SCWCD/ is to preserve order/
> ---/ / | / | _ _ _ ` _ AOPA 925383/ amid change and to /
> --/ ) / |/ |_(_(_(_/_(_/__(__(/_ K3XS / preserve change amid/
> -/ (_/ ' .-/ .-/ ARRL 39280 /order."-A.N.Whitehead/
> /________________(_/_(_/_______AMSAT 32844_/<[hidden email]>/
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>
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>

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N8LP

Re: POW Receiver

In reply to this post by Margaret Leber

To show how much things have changed, I was in the rifle club in high
school in the 60's, and it was in a suburban school... not the country !!!

Larry N8LP

Margaret Leber wrote:

> Fred Jensen wrote:
>
>> 2. "Razor blades" and "campus" don't sound like they belong in the
>> same sentence. Any suggestions for substitutes that would pass the
>> "campus security test?"
>
>
> Things sure have changed since I was on the rifle team in college. I
> don't recall the men shaving much back then though. Or the women, come
> to think of it.
>
> You could always take a Dremel and dull the edge; they don't have to
> be sharp to rectify.
>
> Further resources:
>
> http://www.midnightscience.com/
> http://www.schmarder.com/radios/crystal/
>
> Maggie K3XS K2 1641
>

Carl-N8VZ

K2 Internal Battery Voltages

I just recently replaced the battery in my K2. I ordered from Elecraft,
so this is the "approved" battery. Last week, after a lengthy QSO, I
forgot to turn the rig off, and when I noticed it the next day that
battery was completely depeleted. I charged it up for 24 hours with a
14v supply and it would only charge to about 12.1 volts. Though I don't
remember for sure, I thought this new battery when I charged it
originally started out at something like 13.2 volts or so. Does this
sound right? What should this battery registered when fully charged?
Have I damaged it significantly by letting it rundown to practically
nothing? Obviously, I goofed. I just hope that I haven't significantly
harmed by battery life.

Thanks and 73,

Carl
N8VZ
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johnny-52

Re: K2 Internal Battery Voltages

Hi Carl,

I experienced the same as you about two months ago. I took out the battery
from the rig completely and charged it with a smart charger. I eventually
got a full charge reading of 13.2v and the battery is still working now.

73

Johnny Siu VR2XMC

----- Original Message -----
From: "Carl J. Denbow" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Thursday, October 13, 2005 12:10 PM
Subject: [Elecraft] K2 Internal Battery Voltages

>I just recently replaced the battery in my K2. I ordered from Elecraft, so
>this is the "approved" battery. Last week, after a lengthy QSO, I forgot
>to turn the rig off, and when I noticed it the next day that battery was
>completely depeleted. I charged it up for 24 hours with a 14v supply and
>it would only charge to about 12.1 volts. Though I don't remember for
>sure, I thought this new battery when I charged it originally started out
>at something like 13.2 volts or so. Does this sound right? What should
>this battery registered when fully charged? Have I damaged it
>significantly by letting it rundown to practically nothing? Obviously, I
>goofed. I just hope that I haven't significantly harmed by battery life.
> Thanks and 73,
>
> Carl
> N8VZ

Dave Balla

RE: POW Receiver

In reply to this post by k6dgw

Fred, I found the type of blades your looking for on e-bay. For
reasons other than those you suggested, I don't think it's a good idea
to have razor blades around 6th graders, regardless of how good a
learning tool they may be.

73's Dave, KW4N
______________________________________________________________

From: Fred Jensen <[hidden email]>
Reply-To: [hidden email]
To: Elecraft Reflector <[hidden email]>
Subject: [Elecraft] POW Receiver
Date: Wed, 12 Oct 2005 19:22:06 -0700
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>Off topic, I apologize, but I want to tap the knowledge pool in
this
>group, and I'll continue regardless:
>
>I'm involved with a 6th grade teacher (a ham, he bought my TS830 a
>few years ago) at a local, sort of disadvantaged school. He's
>trying to find ways to reach his kids, and ham radio has worked
out
>pretty well so far with QSO's with a class in Portland OR via 2m
and
>IRLP. I've offered to help him.
>
>I know the recipe for a "POW Radio Receiver" -- some wire in an
>inductor, a capacitor made from rolled up gum wrappers, and a
pencil
>lead on an anodized razor blade, with some stolen headphones, and
as
>new hams in the late 50's, my buddies and I built these and
listened
>to KFI. His kids and he think this would be a great project. We
>won't hear the WW2 BBC, but we might hear KFBK if we can make it
>work.
>
>A couple of problems:
>
>1. Razor blades have changed from the "Gillette Blue Blades" of
>yore. Can I still get them?
>
>2. "Razor blades" and "campus" don't sound like they belong in
the
>same sentence. Any suggestions for substitutes that would pass
the
>"campus security test?"
>
>3. Any other info anyone might have to help me to, at the
beginning
>of the 21st century, recreate for these kids something from the
>middle of the 20th century (when their parents' hadn't yet been
>conceived).
>
>There's a lot of learning to be had here ... history, reading,
>learning how to sequence the steps of a project, and satisfaction
in
>achievement, and these kids are lacking in nearly all of these
>things. I wouldn't attack this if I didn't have a Real Teacher in
>charge.
>
>Thanks in advance,
>
>Fred K6DGW
>Auburn CA CM98lw
>
>PS: We may get some young hams out of this.
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>http://mailman.qth.net/mailman/listinfo/elecraft
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com
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Don Ehrlich-2

Re: K2 Internal Battery Voltages

In reply to this post by Carl-N8VZ

Carl,

I know little about the K2 battery but assume that it is nickle-cadmium or
nickle-metal-hydride and probably consists of 10 or so cells in series.

When such a battery is completely discharged the amount of charge needed by
each of the individual cells becomes unbalanced. For this condition it is
possible that what you think is a normal charge time may in fact charge most
of the cells completely but not completely charge one or more of the others.
The " charged" terminal voltage in this case will appear lower than you
expect. The cure is to continue charging at a low rate (which overcharges
those cells already charged but does not hurt them) until *all* of the cells
come up to their normal fully charged state.

It is possible to damage a battery by letting it run down to nearly nothing
but it is very unlikely if the rate of discharge is low, as it no doubt was
if the rig was on receive all of that time. When the battery is discharged
like that then the first of the cells to reach zero volts go into "reverse"
which is a condition where the cells voltage becomes reversed. Sealed Ni-Cd
cells (or their metal hydride ni-cd relatives) can tolerate a certain amount
of this if the currents involved are low.

Don K7FJ

Robert-223

Re: POW Receiver

In reply to this post by k6dgw

Galena crystals which can be used with a cat whisker to work as the detector
or go to radio shack and buy a bunch of genrmainium diodes (1N34A).

I see galena crystals for sale on ebay. Also there is a recipie for making
you own. Just search the net.

Better yet, Harry's homebrew page has a crystal radio made from coffee cans.
It's very kewl looking and working. Check it out here:
http://web.telia.com/~u85920178/

They are called cavity receivers and work on the concept of a resonant
cavity.

Robert VE3RPF

----- Original Message -----
From: "Fred Jensen" <[hidden email]>
To: "Elecraft Reflector" <[hidden email]>
Sent: Wednesday, October 12, 2005 10:22 PM
Subject: [Elecraft] POW Receiver

> Off topic, I apologize, but I want to tap the knowledge pool in this
> group, and I'll continue regardless:
>
> I'm involved with a 6th grade teacher (a ham, he bought my TS830 a few
> years ago) at a local, sort of disadvantaged school. He's trying to find
> ways to reach his kids, and ham radio has worked out pretty well so far
> with QSO's with a class in Portland OR via 2m and IRLP. I've offered to
> help him.
>
> I know the recipe for a "POW Radio Receiver" -- some wire in an inductor,
> a capacitor made from rolled up gum wrappers, and a pencil lead on an
> anodized razor blade, with some stolen headphones, and as new hams in the
> late 50's, my buddies and I built these and listened to KFI. His kids and
> he think this would be a great project. We won't hear the WW2 BBC, but we
> might hear KFBK if we can make it work.
>
> A couple of problems:
>
> 1. Razor blades have changed from the "Gillette Blue Blades" of yore. Can
> I still get them?
>
> 2. "Razor blades" and "campus" don't sound like they belong in the same
> sentence. Any suggestions for substitutes that would pass the "campus
> security test?"
>
> 3. Any other info anyone might have to help me to, at the beginning of
> the 21st century, recreate for these kids something from the middle of the
> 20th century (when their parents' hadn't yet been conceived).
>
> There's a lot of learning to be had here ... history, reading, learning
> how to sequence the steps of a project, and satisfaction in achievement,
> and these kids are lacking in nearly all of these things. I wouldn't
> attack this if I didn't have a Real Teacher in charge.
>
> Thanks in advance,
>
> Fred K6DGW
> Auburn CA CM98lw
>
> PS: We may get some young hams out of this.
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
> http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com

Stuart Rohre

Re: POW Receiver

In reply to this post by k6dgw

Frank,
There are steel blades still sold at Home Depot for painting clean up of
windows. Single edge razor blades.

Now if the school official "crazies" won't stomach those, you can simple
substitute some plated metal or even a rusty slip of steel. I wonder if a
scrap of blue banding metal tape would work?? You are looking for the
surface of the steel to be plated and that creating a dissimilar metal
junction and hence a diode. You could also simply sub a 1N34 glass diode.

I wonder if you could grind off the sharp edge of single edge blades to
still use them? They have a metal clamp piece that could be held easily by
vice grips to present the sharp blade edge to a grinder wheel. The sweet
spot on the old blades was reputed to be along the engraved logo on the
blade. I am not sure the mass produced import blades sold for paint
scraping still have an etched logo or name section.

Stuart
K5KVH

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Stuart Rohre

Re: POW Receiver

In reply to this post by David Toepfer

I wonder if the blue blades are the same steel coating procedure as bluing a
gun barrel? If so, you can get solution for treating steel at most gun
shops that cater to those restoring firearms.

Stuart
K5KVH

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John Lonigro

Re: K2 Internal Battery Voltages

In reply to this post by Don Ehrlich-2

Don:

The K2 internal battery is a gel-cell (or sealed lead-acid) battery, not
NiCd or NiMH, but much of your discussion probably still applies. It
may take a while for the "equalization" charge to get all the (6) cells
charged to full potential, which is always true, but might be more so
when the battery is totally drained, as it was in this case.

John AA0VE

Don wrote:

> Carl,
>
> I know little about the K2 battery but assume that it is
> nickle-cadmium or nickle-metal-hydride and probably consists of 10 or
> so cells in series.

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Carl-N8VZ

Re: K2 Internal Battery Voltages

Thanks, John. I wondered if Don's comments applied to lead-acid
batteries. How long should I charge it for equalization purposes, and
at what voltage? Tnxs & 73, de N8VZ (Carl)

John R. Lonigro wrote:

> Don:
>
> The K2 internal battery is a gel-cell (or sealed lead-acid) battery,
> not NiCd or NiMH, but much of your discussion probably still applies.
> It may take a while for the "equalization" charge to get all the (6)
> cells charged to full potential, which is always true, but might be
> more so when the battery is totally drained, as it was in this case.
>
> John AA0VE
>
> Don wrote:
>
>> Carl,
>>
>> I know little about the K2 battery but assume that it is
>> nickle-cadmium or nickle-metal-hydride and probably consists of 10 or
>> so cells in series.
>
>
> _______________________________________________
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>
>
>