QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/homebrew/940197.txt

Internet Message Format | 1994-11-13 | 11KB

Date: Sat, 16 Jul 94 04:30:27 PDT
From: Ham-Homebrew Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Homebrew Digest V94 #197
To: Ham-Homebrew


Ham-Homebrew Digest         Sat, 16 Jul 94       Volume 94 : Issue  197

Today's Topics:
                  'Who was that masked capacitor?'
           FOLLOWUP/RETRACTION:  Electronic Chemical Blues
                          INFO. ON ANTIQUE ?
                         LF Band experience?
                         type-C RF connectors

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Archives of past issues of the Ham-Homebrew Digest are available
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We trust that readers are intelligent enough to realize that all text
herein consists of personal comments and does not represent the official
policies or positions of any party.  Your mileage may vary.  So there.
----------------------------------------------------------------------

Date: Fri, 15 Jul 94 16:01:04 GMT
From: news.cerf.net!gopher.sdsc.edu!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!zip.eecs.umich.edu!newsxfer.itd.umich.edu!gatech!howland.reston.ans.net!math.@@ihnp4.ucsd.edu
Subject: 'Who was that masked capacitor?'
To: [e-mail]

In article <[e-mail]> [e-mail] writes:

  >
  >      I was wondering if any of you fine gentleman could answer a simple
  > question for me.  I'm searching for what has been coined as a 'piston
  > trimmer' capacitor.

  Quite simply, it is a glass tube (usually 1/4" in diameter) that has been
  copper plated on the outside, with a thread adjustable inner part (piston)
  that acts as the second plate of a capacitor.

  73 es GM from Jeff

 Amateur: WA6FWI@WA6FWI.#SOCA.CA.USA.NOAM | "You have a flair for adding
Internet: [e-mail]        |  a fanciful dimension to any
 US Mail: PO Box 4425 Carson, CA 90749    |  story."
   Phone: [phone]                |           Peking Noodle Co.

Hate "Green Card Lottery"? Want to help curb ignorant crossposting on Usenet?
E-mail [e-mail] for more information, or read news.groups.

------------------------------

Date: 15 Jul 1994 16:23:02 -0400
From: news.cerf.net!gopher.sdsc.edu!news.tc.cornell.edu!travelers.mail.cornell.edu!news.kei.com!MathWorks.Com!news2.near.net!bloom-beacon.mit.edu!ai-lab!bronze.lcs.mit.edu!@@ihnp4.ucsd.edu
Subject: FOLLOWUP/RETRACTION:  Electronic Chemical Blues
To: [e-mail]

Thanks to those folks who suggested alternate chemicals and methods to use,
but first, an apology:  As Henry Spencer and a few others have pointed out,
there isn't a conspiracy against individual servicers;  my experiences
were just due to some unfortunate timing on my and the EPA's part.
Henry's quite right that the CFC regulations have affected large companies
as well.  (To the guy that called me empty-headed, I'm really sorry--I forgot
about Halon.)

As Henry says, all CFC solvents are to be eliminated in a few years (1996?),
and the existing chemicals are being slowly phased out.  The current
patchwork regulations of what can be sold to whom is a cause for much
confusion and consternation for myself, others, and (I suspect) vendors such
as MCM.

I don't care to argue the ozone matter;  CFC's are going away, and I'm
just trying to find subsitutes that are safe as possible for the ozone
*and* myself.  I'm not interested in stockpiling;  I don't want to store
large quantities of *any* chemical in my house.

I'm not necessarily averse to using petroleum-based products;  as I mentioned
previously, I use acetone (yes, people, I *know* it eats plastic!  Voice
of experience?  Nah! :)) and isopropanol.  Both of these are flammable, but
I've been using them for awhile and I can (IMHO) control the risks.  I'd
like that any chemical I buy not have much more risk than the ones
I mentioned.   (I don't clean with kerosene;  why should I bear the fire
risk from a like solvent if I don't need to?)

One thing I thought of:  Except for compressed air, why do we need aerosol
cans at all?  I usually use the cans to spray short bursts with an
extension tube, or spray into a paper towel, foam swab or Q-tip.  I'd
be perfectly happy, for my purposes, with a pump-bottle.  (I'm not sure
this would work for freeze spray, but it's still one less can on my shelf.)
If it removed the risk of a flammable propellant, I'd be relieved.

I'd recommend that *anyone* on this group who buys chemicals read the fine
print on the can and ask questions, CFCs or not.  There's an interesting
article in the current issue of ELECTRONIC SERVICING AND TECHNOLOGY that
covers this very subject, quite timely. ("Electronic Servicing for Performance
and Reduced Environmental Impact", Dr. Mo Tazi, p.20)

...Dave



--
| David Moisan, N1KGH    /^\_/^\   [e-mail]      |
| 86 Essex St. Apt #204 ( o ^ o )  [e-mail]                |
| Salem. MA 01970-5225     | |     [e-mail]    |
|                                                                 |

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Date: Fri, 15 Jul 1994 22:27:49 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!gatech!nntp.msstate.edu!olivea!sgigate.sgi.com!odin!ukcsd.reading.sgi.com![e-mail]
Subject: INFO. ON ANTIQUE ?
To: [e-mail]

Some time ago, I became the proud owner of a receiver built in the 1920s
(?)
by an uncle of my father. I am told that it was built from a magazine
article
and was called  The Foreign Listeners Four because at that time it could
receive
four foreign stations - from the UK.

It's a fascinating piece of Meccano built on a wooden board and housed in
what
I think was once the case of a floor standing wind-up gramaphone. It
consists
of four pin triodes with screw terminal bases and is hooked together with
square
sectioned, rubber coated wire.

Can anyone give me any information on my fossil ? Or does anyone know a
living fossil who might of heard of it ?

What I'd really like to do is get it going again and to have a copy of the
original magazine article would be fascinating.

Please email me with replies as my access to News is only as reliable as
the
next mod I make to the bridge I'm using.

Thanks

John

--




    John Statham            [e-mail]
    Silicon Graphics
    Laser House            Tel: [phone]
    Salford Quays
    Manchester
    United Kingdom


    Yes, perhaps I have lost my mind, but I should have a backup
    on tape somewhere.

------------------------------

Date: 15 Jul 94 18:24:24 GMT
From: [e-mail]
Subject: LF Band experience?
To: [e-mail]

Running FM in the LF (LowFER) band is pretty easy...  but doing so
effectively depends on what you intend to do and how you intend to do it.

If you wish to go a short distance (a few miles at most, more likely, not
more than a block or two) then FM would be a dismal choice (I would
take it that you are talking about FM voice...) for several reasons:

- It takes up massive bandwidth.  For standard 3 KHz deviation FM voice,
expect to require about 12 KHz or so.  You can't do the old idea of "I don't
need 3 KHz deviation...  If I deviate only 1 KHz or 500 Hz, then I'll take
a LOT less bandwidth..."  If you think this will work, then re-read about
FM...
- If you FM is Ok (i.e. you can live with the wide bandwidth, the very
high noise levels (especially in urban areas...)  (Oops... I meant to say
"If for you FM is OK...") then you have to consider the matching network.
A LowFER antenna system is typically a base-loaded tophatted vertical with a
VERY good ground system.  As with any heavily-loaded antenna the loading
coil (in this example) is likely to be your primary loss factor.  A wire
coil of heavy-guage wire (14 or 12) would work, but Litz wire (remember that?)
such as 12/40 (#12 with strands of #40) will work very well if its geometry
is appropriate (i.e. a basket-weave coil to minimize its distributed capacitance
 which would spoil its Q, thereby efficiency...)
So, if you build a half-decent coil (to acheive half-decent power transfer)
then you are talking about very high Q.  I ran some SSB on the Lowfer band
for a while and using a coil that wasn't really all that great, I could hear
'sideband cutting'  as I tuned through resonance.  In fact, I had to retune
if I changed from upper to lower sideband.  The point is that an SSB signal
taking only 2.5 KHz or so *is* 'colored' by the tuning network.  Imagine
what would happen (response-wise, not to mention phase-wise to an approx.
10 KHz wide FM signal...)

If it is voice communications that you want, there are lots of reasons why
SSB (or even AM...) may be better suited than FM on this band...  That's
not saying that it can't be done, but one should keep in mind the contradicting
requirements/realities.  There *are* ways to broaden the bandwidth at these
frequencies without killing efficiency (Radio Warsaw, Poland has an LF
transmitter in the 150 KHz range and it has typical european AM/LF broadcast
bandwidth on its transmissions, about 10-12 KHz or so, at least...) but
I'll be darned if I can remember how it was done, or where I saw its
desicription.  A good book on all of this is 'VLF Radio Engineering' by Watt.
It was published in the late 60's and it is in most larger libraries...

<Clint>

Internet:    [e-mail]
Amprnet:     [e-mail]

------------------------------

Date: 15 Jul 1994 16:41:31 GMT
From: noc.near.net!sunfish.hi.com!brainiac.hi.com![e-mail]
Subject: type-C RF connectors
To: [e-mail]

In article <[e-mail]>,
[e-mail] (Fred McKenzie) wrote:
> As far as airflow is concerned, are there any active components involved?
> What generates heat?  If the multicoupler has only passive, high-Q
> components, the cooling air may have been required for very high RF power
> levels.  For low power, it may not be needed.

The receiver multicoupler has a two-transistor RF preamp per output to make
up for losses in the hybrid splitters. These transistors probably run at a
high bias current for better IMD performance. (They are TO-5 cased, and
have clip-on heatsink fins. Some have "TRW 02"markings on top.) The
mechanical design of the enclosure for this beast does not provide for
convection-cooling. It has only a small inlet slot on the right side, and a
larger outlet slot on the left side.

I expect that the power dissipation isn't all that high, but without
forced-air cooling, the transistors probably wouldn't last long.

Steve Byan                                  internet: [e-mail]
Hitachi Computer Products (America), Inc.
1601 Trapelo Road                           phone: [phone]
Waltham, MA 02154                           FAX: [phone]

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End of Ham-Homebrew Digest V94 #197
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