QRZ! Ham Radio 5/QRZ Ham Radio Callsign Database - Volume 5.iso/digests/homebrew/940192.txt

Internet Message Format | 1994-11-13 | 16KB

Date: Wed, 13 Jul 94 04:30:42 PDT
From: Ham-Homebrew Mailing List and Newsgroup <[e-mail]>
Errors-To: [e-mail]
Reply-To: [e-mail]
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Subject: Ham-Homebrew Digest V94 #192
To: Ham-Homebrew


Ham-Homebrew Digest         Wed, 13 Jul 94       Volume 94 : Issue  192

Today's Topics:
              'Who was that masked capacitor?' (4 msgs)
               Beware of RADIOKIT kits (IMHO) (2 msgs)
                       DISTRIBUTED CAPACITANCE
                Frequency conversion - non-linear mode
                     Help-Remote Control circuits
                     RDF kit order lost (2 msgs)
          SELL/Filter Capacitor for BIG Linear applications
                     Source for Crystal filters?

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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: Mon, 11 Jul 1994 23:37:37
From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!news.umbc.edu!hookup!nic.ott.hookup.net!tallath.ott.hookup.net![e-mail]
Subject: 'Who was that masked capacitor?'
To: [e-mail]

     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.  From what I know it is a variable capacitor but when I ask for it
at Wackid's, Radio Shack, and electronics stores they either don't know what
I'm asking for or have a vague idea what I'm talking about but can't seem to
convey a good description of it to me.

    This problem is compounded by the fact that I don't know what it looks
like and don't know where I should look for one.  I've checked the FAQ with no
success.  Could someone explain what it is, what it would probably look like,
and since no one here - where I am, not in this newsgroup - knows what I'm
asking for, could someone give an order number or suggest a good place to
mail-order from that might have some.

    Thanks

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

Date: 12 Jul 94 14:23:03 GMT
From: ihnp4.ucsd.edu!library.ucla.edu!agate!howland.reston.ans.net!vixen.cso.uiuc.edu!aries![e-mail]
Subject: 'Who was that masked capacitor?'
To: [e-mail]

[e-mail] (Gordon R Beatty) 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.  From what I know it is a variable capacitor but when I ask for it
>at Wackid's, Radio Shack, and electronics stores they either don't know what
>I'm asking for or have a vague idea what I'm talking about but can't seem to
>convey a good description of it to me.

>    This problem is compounded by the fact that I don't know what it looks
>like and don't know where I should look for one.  I've checked the FAQ with no
>success.  Could someone explain what it is, what it would probably look like,
>and since no one here - where I am, not in this newsgroup - knows what I'm
>asking for, could someone give an order number or suggest a good place to
>mail-order from that might have some.

It's round, made out of glass or ceramic, and the capacity is between the
metal on the outside of the round tubular glass and the round tubular metal
cylinder that moves to and fro inside the glass tube. The glass or ceramic
is the dielectric. The end of the glass tube has a cap made out of metal
with a threaded hole in it, and the movable cylinder has a threaded rod
attached to it. Turning the threaded rod gives a precise movement of the
cylinder within the tube. Try Digi-Key 1-800-344-4539 (only one kind offered)
or Newark (many branches around the country but $25 minimum) 1-312-784-5100


Chuck Hawley, KE9UW in Urbana, Illinois
[e-mail]
School of Chemical Sciences, Electronic Services
University of Illinois, Urbana-Champaign

>    Thanks

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

Date: Tue, 12 Jul 1994 14:50:45 GMT
From: tandem!mustang![e-mail]
Subject: 'Who was that masked capacitor?'
To: [e-mail]

In article [e-mail], [e-mail] (Gordon R Beatty) writes:
> ... I'm searching for what has been coined as a 'piston trimmer'
> capacitor.  From what I know it is a variable capacitor.  ....

-Correct

>  ... This problem is compounded by the fact that I don't know what it looks
> like and don't know where I should look for one. ...

A piston trimmer capacitor physically looks like an insulative tube with an
electrode on the outside (plated or foil wrapped) and an adjustable element
that looks like a slug that slides in and out of the tube.  The amount of
capacitance, as you might guess, varies relative to the amount of the two
conductive parts that are adjacent to one another (overlap?).  Works just like
any other variable cap, but normally uses the tube as dielectric instead of
air (standard rotary variable) or air and mylar insulator (compression trimmer)

They used to be available from Allied, etc (years ago), and at all the surplus
places.  I haven't seen one in years, but that doesn't mean theyre not still
available, just that I've not been looking for any.  Typical size of the ones
I've played with was around 1/4" in diameter and 1" long or less.   I'd imagine
you could use any trimmer _with_sufficient_voltage_rating_  and capacitance as
a substitute.

--good hunting---

--Rick         KD6QZD           [e-mail]

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

Date: Tue, 12 Jul 1994 23:23:17 GMT
From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!convex!news.duke.edu!eff!news.kei.com!ddsw1!indep1![e-mail]
Subject: 'Who was that masked capacitor?'
To: [e-mail]

In article <[e-mail]> [e-mail] (Gordon R Beatty) 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'

They're like a little white tube with a lead off each end and a screw going
into one end.  Some are maybe 3/4" long by 1/8" diameter.  Also called
multiturn trimmers.  If you have the July-Aug 1994 DigiKey catalog, look
at the bottom of page 205 for pictures.

--
                Optimists say, "The glass is half full."
   Cliff Sharp            Pessimists say, "It's half empty."
     WA9PDM            We realists say, "Before I decide,
  [e-mail]     tell me what's in the glass."

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

Date: 11 Jul 1994 21:52:02 -0400
From: newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: Beware of RADIOKIT kits (IMHO)
To: [e-mail]

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

You go that right I ran into the same problems with their QRP 17. Never
again
though. I still cant get the thing to work right. I only get about 1 to
1.5 watts
output on mine.
                                     Pete

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

Date: 12 Jul 94 00:32:13 EST
From: csusys.ctstateu.edu![e-mail]
Subject: Beware of RADIOKIT kits (IMHO)
To: [e-mail]

I still agree. Radiokit needs to get their act together. The QRP-20 kit
has taken its rightful place in my ham career: as my first failure.
Every solder joint checked, schematic traced, coils verified and
turns recounted, etc. etc. They should *at least* tell you that the
kit is for advanced builders or EEs :)
It was also missing 7 parts though they did mail the parts promptly.The
manual is a joke, and would be just as worthless to the builder of the
QRP-15, which is the manual supplied with the QRP-20.
C'est la vie. We learn.
73 de N1QVE
Harry

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

Date: Tue, 12 Jul 94 21:04:33 EDT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!darwin.sura.net!opusc!UNIVSCVM.CSD.SCAROLINA.EDU![e-mail]
Subject: DISTRIBUTED CAPACITANCE
To: [e-mail]

Someone MUST know the answer to this question:
  How does one CALCULATE the distributed capacitance of a long,
  single-layer solenoid? I cannot find this calculation anywhere. I have
  posted on science groups, even MENSA, and no one can help me. I know how to g
  get it from a existing coil, but I want to be able to design them for a
  specific value and not have to do it all empirically. I someone has the a
  answer, could you mail me what it is? This is all that is stopping me from
  finishing a book. You will be mentioned if the thing is ever published...
My e-mail address is: [e-mail]

Please start with "Attention Dan"

Thanks tremendously!

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

Date: Tue, 12 Jul 1994 16:51:51 GMT
From: ftpbox!mothost!pts-nntp!sun32![e-mail]
Subject: Frequency conversion - non-linear mode
To: [e-mail]

In article [e-mail], [e-mail] (Steve Byan) writes:
>> Dr. Ulrich Rohde has had several article in QEX on modeling receiver
>> front ends and other RF circuits.
>>
>[...]
>>
>> It's all above me, but it looks like he can get noise figure and
>> dynamic range out of a software package called Microwave Harmonica.
>
>I dunno about Microwave Harmonica, but it seems to me that a good part of
>Rohde's articles deal with calculating the system 3rd-order intercept given
>the 3rd-order intercept of the pieces. This is well and good, but it leaves
>me wondering how to predict the 3rd-order intercept of the pieces. I
>suppose one measures it in the lab. (Lab? What's that? :-) Since I'm
>lab-equipment-poor, I'm interested in good models that predict 3rd-order
>intercept reasonably well.
>
>Steve Byan                                  internet: [e-mail]
>Hitachi Computer Products (America), Inc.
>1601 Trapelo Road                           phone: [phone]
>Waltham, MA 02154                           FAX: [phone]

If you'd like to spend a bunch of cash on a recent non-linear simulator, MDS
has been working well for me. Microwave Harmonica will also work. The problem with
simulating IP3 is that you ned models that represent the reality of the device
fairly closely. What I have been doing is to do modeling and banchwork in parallel,
so that I can confirm both sets of results independently.
As far as measuring IP3, all you need is 2 signal generators and a spectrum analyzer.
(Motorola paid for mine !) . A lot depends on the frequency band you are working in.


---
David Bengtson            407-364-3806
Motorola            No, I'm not speaking for Motorola
Mail Stop 98            If I was, I'd be making more money!
1500 NW 22nd Ave
Boynton Beach, FL 33626

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

Date: 12 Jul 1994 01:00:55 GMT
From: ihnp4.ucsd.edu!swrinde!gatech!udel!news2.sprintlink.net!news.sprintlink.net!tequesta.gate.net!inca.gate.net![e-mail]
Subject: Help-Remote Control circuits
To: [e-mail]

I am Newbie2be Tech amateur looking for any info on small RF remote
control circuits for hand held use, like for activating / deactivating
mobile alarms and such.  Would this fall under the 50 Mhz. "model craft"
section?  I am interested in building / learning about RF control, please
point me and I shall run in that direction.  Thanks,

Bob Bronson   [e-mail]

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

Date: 12 Jul 94 00:39:15 -0800
From: ihnp4.ucsd.edu!usc!nic-nac.CSU.net!vax.sonoma.edu![e-mail]
Subject: RDF kit order lost
To: [e-mail]

In article <[e-mail]>, [e-mail] () writes:
> At the Dayton Hamfest there was a fellow selling RDF kits
> based on the May 93 article in QST on the "Handi-Finder."
>
> I bought a kit and it works fine.
>
> I then followed up with an order for 25 kits for our
> local ham radio club and RACES group.


Just what type of RDF kits were these?  I never saw the article...

73,
Ken Harrison
N6MHG
email:  [e-mail]

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

Date: Tue, 12 Jul 1994 12:33:44 GMT
From: pacbell.com!att-out!nntpa![e-mail]
Subject: RDF kit order lost
To: [e-mail]

The article is
"Build the HANDI-Finder!"
May 1993 QST, page 35
author: Bob Leskovec, K8DTS

Joe Wilkes

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

Date: 11 Jul 1994 18:08:38 -0500
From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!uwm.edu!omnifest.uwm.edu!omnifest.uwm.edu![e-mail]
Subject: SELL/Filter Capacitor for BIG Linear applications
To: [e-mail]

Hi,
    I have a Cornell Dubilier Mod. LPC 102-1 Filter Capacitor rated at:
8KVDC @ 16MFD. It is in new unused condition.  Physical dimensions are:
12" high (including terminals) X 8" wide X 6" deep.
Price: $50.00 plus shipping (weight approx 30#
Contact: [e-mail]
###

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

Date: 12 Jul 1994 21:09:11 -0400
From: newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: Source for Crystal filters?
To: [e-mail]

Does anyone know where one can buy various crystal filters in small
quantities?

Can you get then at different frequencies?

Also most filters I have ever seen were band pass in the QST reciever
article by
Dr Rhode he mentions a Crystal Roofing filter, I get the impression he
means a
crystal low pass filter with a steep skirt. I have never seen a crystal
lowpass filter?
How is one constructed????

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

Date: 12 Jul 94 06:36:45 GMT
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!europa.eng.gtefsd.com!MathWorks.Com!noc.near.net!news.delphi.com!BIX.com![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>Γ
Subject : Re: Frequency conversion - non-linear mode

[e-mail] (Steve Byan) writes:

>> Dr. Ulrich Rohde has had several article in QEX on modeling receiver
>> front ends and other RF circuits.
>>
>[...]
>>
>> It's all above me, but it looks like he can get noise figure and
>> dynamic range out of a software package called Microwave Harmonica.

>I dunno about Microwave Harmonica, but it seems to me that a good part of
>Rohde's articles deal with calculating the system 3rd-order intercept given
>the 3rd-order intercept of the pieces. This is well and good, but it leaves
>me wondering how to predict the 3rd-order intercept of the pieces. I
>suppose one measures it in the lab. (Lab? What's that? :-) Since I'm
>lab-equipment-poor, I'm interested in good models that predict 3rd-order
>intercept reasonably well.

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

If you can get one point on the IMD curve you can calculate the intercept
point. So if your modeling SW provides "two interfering signals of -27dBm
each produce an IMD product of -107dBm" or even "100dB dynamic range relative
to sensitivity of -117dBm" etc you can work backwards to the intercept point.

Taking the first cited data, -107dBm birdy for two -27dBm signals, we can work
backwards. For every 1dB we increase the signal levels the birdy goes up three
or the difference drops by 2db. Since the difference is 80dB as cited we have
to reduce the difference by 80dB to get signal equal to spur, in the method
used with military projects when I was doing them. Hence we must change the
individual signals by half the 80dB. -27dBm + 40dB gives an intercept point
of +13dBm. (Which ain't all that bad.)
{^_^}    [e-mail]

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

End of Ham-Homebrew Digest V94 #192
******************************