QRZ! Ham Radio 5/QRZ Ham Radio Callsign Database - Volume 5.iso/digests/homebrew/940281.txt

Internet Message Format | 1994-11-13 | 9KB

Date: Thu, 22 Sep 94 04:30:30 PDT
From: Ham-Homebrew Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Homebrew Digest V94 #281
To: Ham-Homebrew


Ham-Homebrew Digest         Thu, 22 Sep 94       Volume 94 : Issue  281

Today's Topics:
                    Hi Z Probe 50 mhz Freq Counter
                      New walkmans have AM-Wide
                       Overtone crytal filters
                  Plans for 2m 50W solid state amp?

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

Date: 21 Sep 94 21:45:55 GMT
From: [e-mail]
Subject: Hi Z Probe 50 mhz Freq Counter
To: [e-mail]

>bob.berlyn.303@chowda:com writes: (50 mhz frequency Counter)
>I have found plans for a 50 Mhz autograging frequency counter....
>
>...The circuit's sensitivity is about 100 mV RMS
>at frequencies from 100 Hz to 2 Mhz, and decreasing to about
>800 mv RMS at 50 Mhz.

>>"John F. Woods" <[e-mail]> answers: (re: 50 mhz frequency counter)

>>at 800mV sensitivity, it's probably good enough to check out VFOs and
>>such.  If you need more sensitivity, an MAR amplifier will run about
>> $1? in your next order to your favorite surplus shop.

====
Can someone give a few more details about using a counter
with a 50 ohm input Z and an add-on MAR to measure
smaller RF signals such as an NE-602 LO on pin 3 or 4, using
the internal transistor in a parallel tuned Colpitts (46 mhz)?
My counter has <1mv rms 10 - 600 mhz sensitivity, so adding a
MAR amp may not be necessry. My counter already has 4 MAR-6's
at the 50 ohm input. I suspect a (wide band) Hi-Impedance
probe is what is needed for this measurement. Please comment.

I've not been able to use the 50 ohm input of my counter
to measure the NE-602 LO frequency or the LO on similar mixer IC's.
I assume the RF levels are too small or that the
LO stalls due to the low impedance, or both.

Can someone suggestion a probe scheme to add to my 50 ohm
input counter to help measure applications like this NE-602 LO?
The counter is capable of measuring to 2.4 ghz. So, the
added circuit(s) need to match most of that frequency range.

Another Counter
---------------
I would appreciate recommendations for a good USED freq counter,
for use in my home workshop and ham station. Please include
brand names and models that have worked well for you folks.
Prefer instrument that WILL NOT display when input signal
is too low for stable readings.

Must be able to check timebase against WWV.
I want .2 ppm timebase but small budget says I'll settle for looser.
Want 2 ghz upper limit and 10 digits display if possible.

73 and thanks,
Dave w6mik

--
Internet : [e-mail]
AMPR.ORG :lp.w6mik.ampr.org [44.16.0.29]
AMPR.ORG :w6mik.ampr.org [44.16.0.26]
7833 Cantaloupe Ave. Van Nuys, CA 91402

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

Date: Thu, 15 Sep 1994 16:32:07 GMT
From: (null)@[e-mail]
Subject: New walkmans have AM-Wide
To: [e-mail]

The reason the radio covers 1.7Mhz and beyond is because they were made
for the Japanese home market and the MW / AM band is extended to 1.7MHz
or possibly even higher there.

Amazing but true!

[e-mail]

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

Date: 21 Sep 94 14:56:59 GMT
From: [e-mail]
Subject: Overtone crytal filters
To: [e-mail]

     Ian:
        I ran a quick check on the equivalent circuit of a microprocessor
     crystal in overtone mode.  It was a 2.457 MHz crystal.  The equivalent
     circuit at 2.45 MHz showed an equivalent series R of about 4 ohms.  At
     7.3 MHz it showed an equivalent R of 3K ohms.  The overtone resonance
     is measurable in this crystal but probably not very useful.

        Perhaps Zack Lau has some experience with typical equivalent
     circuits for overtone crystals.  I would assume that a crystal
     specifically intended for overtone work would have better responses.
     I called Jan Crystal and the very helpful lady said that a 45 MHz
     crystal would typically have about 40 Ohms of series resistance.  This
     value would probably allow building a filter with reasonable insertion
     loss if about a 100 to 200 Ohm impedance is selected.  The problem
     here of course is that you would have to special order the crystals,
     and by the time you purchased enough crystals for reasonable response,
     you could probably purchase a commercial filter for the same cost.

       At $3 (US) fairly high frequency microprocessor crystals are the
     only ones that make any sense to me for this kind of application.
     This allows you to buy enough of them to get a matched set.  The
     highest frequency I have tried is 16 MHz.


     Ray Mack
     WD5IFS
     [e-mail]

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

Date: 21 Sep 1994 17:11 CST
From: dog.ee.lbl.gov!overload.lbl.gov!dancer.ca.sandia.gov!cronkite.nersc.gov!fastrac.llnl.gov!lll-winken.llnl.gov!uwm.edu!psuvax1!news.pop.psu.edu!news.cac.psu.edu!howland.@@ihnp4.ucsd.edu
Subject: Plans for 2m 50W solid state amp?
To: [e-mail]

I am looking for information or plans for building a 50W solid state
amp for use in the 2m or 2m/440 bands.  I am interested both in complete
circuit diagrams or suggestions for power transistors that I can use to
build these amps.  Any information would be appreciated.  Thanks.


Jay Porter
Texas A&M University
[e-mail]

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

Date: Wed, 21 Sep 1994 14:42:51 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!cs.utexas.edu!utnut!nott!cunews!freenet.carleton.ca!FreeNet.Carleton.CA![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>e
Reply-To : [e-mail] (Russ Renaud)
Subject : Re: Reuse surface mount parts?


In a previous article, [e-mail] (Charlos Potma) says:

>I believe it was in RadCom that I saw a simple method to remove surface
>mounted IC's. If you can push a thin wire under the IC, fix one end
>somewhere on the board (solder...) and the pull the wire against the inner
>side of the IC legs while at the same time applying your soldering iron
>to each successive leg. As the solder melts you pull the wire through thus
>loosening the leg from the board. I have not tried this myself but perhaps
>it is worth a try if you want to exchange one or more IC's on the board.
>You >have< to be able to slide the wire under the IC though...

Heat guns sold at the hardware store to strip paint, etc are generally hot
enough to melt solder.  On old single sided boards, I lever up the IC with
a very thin screwdriver, heat the trace side of the board up with the heat
gun, and can usually strip an entire board in half an hour.

I wouldn't want to try this method on boards with components on both
sides, however.  8^)

73 de va3rr/aa8lu

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

Date: Wed, 21 Sep 1994 09:33:25 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!agate!howland.reston.ans.net!EU.net!sun4nl!rivm![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>
Subject : Re: Reuse surface mount parts?

chuck adams ([e-mail]) wrote:
: In article <[e-mail]>, [e-mail] (Zack Lau (KH6CP)) writes:
: ...stuff deleted...
: |> No, this isn't the way to remove them.  You want lots of heat and solder

: Reminds me of an article in V1#1 of Byte Magazine on salvaging computer
: parts from old computers.  This was in the 1975 timeframe.  The author
: used a torch on the bottom side of the board until the IC dropped or
: used channel-lock (tm?) pliars to hold IC until it would come out.  :-)
: ...more stuff deleted...

I believe it was in RadCom that I saw a simple method to remove surface
mounted IC's. If you can push a thin wire under the IC, fix one end
somewhere on the board (solder...) and the pull the wire against the inner
side of the IC legs while at the same time applying your soldering iron
to each successive leg. As the solder melts you pull the wire through thus
loosening the leg from the board. I have not tried this myself but perhaps
it is worth a try if you want to exchange one or more IC's on the board.
You >have< to be able to slide the wire under the IC though...

I don't know if this description makes any sense, English is not
what I speak daily.

73 from PA3CKR
Charlos Potma
[e-mail]

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End of Ham-Homebrew Digest V94 #281
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