QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/homebrew/940201.txt

Internet Message Format | 1994-11-13 | 25KB

Date: Tue, 19 Jul 94 04:30:28 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 #201
To: Ham-Homebrew


Ham-Homebrew Digest         Tue, 19 Jul 94       Volume 94 : Issue  201

Today's Topics:
                  a High Dymnic range Mixer (2 msgs)
                       Dummy Load Oil (3 msgs)
                            J-Pole Antenna
                          JOHANSON TRIMMERS?
                         Kenwood TR2500 mods
             QRP Mail List (was: Building an HW-9: HALP!)
                            reply to N6MHG
                           reply to several
                  Rolling my own Transformer (LONG)

Send Replies or notes for publication to: <[e-mail]>
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Problems you can't solve otherwise to [e-mail].

Archives of past issues of the Ham-Homebrew Digest are available
(by FTP only) from UCSD.Edu in directory "mailarchives/ham-homebrew".

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: 18 Jul 1994 18:28:05 -0400
From: newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: a High Dymnic range Mixer
To: [e-mail]

In my origional post I said I wanted any information of IC mixers
that would be good for use on the HF bands with a preamp.
(That was I stupid request!!!! On the HF bands Dynamic range is more
important
than noise figure!!!! so no preamp.)
That was a typeo I ment with out a preamp. Like the block diagram in the
QST recieveier article.

Has anyone used the new mixer from analog devices?
It has a SSB noise figure of 20dB and a dynamic range of 100+ dB
Is this noise figure of 20dB Good enough for 10 and 15M?

Also how do you convert from or between noise figures specified as:
SSB dB
nv/Root Hz
and Temperature???

Thanks in advance
Paul Breed KL7JG

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

Date: 19 Jul 94 08:45:49 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!noc.near.net!news2.near.net!news.delphi.com!BIX.com![e-mail]
Subject: a High Dymnic range Mixer
To: [e-mail]

[e-mail] (PaulBreed) writes:

>In my origional post I said I wanted any information of IC mixers
>that would be good for use on the HF bands with a preamp.
>(That was I stupid request!!!! On the HF bands Dynamic range is more
>important
>than noise figure!!!! so no preamp.)
>That was a typeo I ment with out a preamp. Like the block diagram in the
>QST recieveier article.

>Has anyone used the new mixer from analog devices?
>It has a SSB noise figure of 20dB and a dynamic range of 100+ dB
>Is this noise figure of 20dB Good enough for 10 and 15M?

>Also how do you convert from or between noise figures specified as:
>SSB dB
>nv/Root Hz
>and Temperature???

>Thanks in advance
>Paul Breed KL7JG

SSB dB is nonsense salesjargon, IMHO.

nv/Root Hz and temperature are related by the Boltzmann equation.
Essentially noise power = kTB, which at room temperture is about -173.85dBm/Hz.
Once you have that value you can calculate all the other values you want by
playing with absolute temperature ratios and things like power = E^2/R
relations.

The noise temperature of a receiver is related to how much noise you get out
of the receiver with a standard "physics class" noiseless source the same
impedance as it usually connected. The noise figure is related to the sum
of the source resistor noise plus the excess receiver noise divided by
the source resistor noise. A noiseless receiver has a VERY low noise
temperature and a noise figure very close to unity.
So lemme see here.... 10^-20.385 (to make it watts) ~= 4*10^-21 = E^2/50.
This means E^2 = 50*4*10^-21 = 2*10^-19 volts squared. Thus a bare room temp
50 ohm resistor generates about .4nV/Root Hz noise. In a 2400Hz SSB bandwidth
this means about .022uV of noise in a 0dB noise figure receiver. In a 3dB NF
receiver that'd be maybe .031uV of noise. For all the good that will do.
(I suppose it means you can place a 50 ohm signal generator witl attenuators
on the receiver input and enjoy a 20dB SNR on a CW signal in the SSB passband
with a 0.3uV signal. All of which is meaningless for SSB usage and also
meaningless for normal usages on HF. For HF usage with dipoles or gain antennas
you want a frequency sensitive attenuator in front of the receiver with
perhaps the 3dB corner at 30MHz and attenuation rising about 6dB per octave
as the frequency goes down. And even THAT may be underkill in most urban
locations. That attenuator will do WONDERS for practical IMD performance on
any receiver, by the way.)
{^_^}    Joanne Dow, Editor Amiga Exchange, BIX
    [e-mail]

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

Date: 18 Jul 94 15:00:00 GMT
From: [e-mail]
Subject: Dummy Load Oil
To: [e-mail]

In digest 199, Ken (N6MHG) writes:


>What sort of oil is used in the paint can variety of dummy load?  I've seen
an
>article that said mineral oil would work pretty well but was prohibitively
>expensive.  While at Wal-mart the other night I checked the prices of their
>mineral oil.  $1.62 per 16oz. bottle.  That doesn't seem to be
prohibitively
>expensive to me at about $13 for a full gallon.  Am I missing something?
>
>Ken Harrison
>N6MHG
>email:  [e-mail]

Yes, mineral oil is a little expensive and is probably the
safest to use in a dummy load.  Don't try anything like motor
oil, it has many different types of lubricants that have
different volatility.  The 'best' type of oil is "turbine oil."
You can get it at many farm and ranch supply stores.  One of the
easiest to find is sold by TEXACO distributors, Regal Oil R&O  Number
46.  You can usually find it in 5 gallon cans sold as "turbine oil."
I don't know how easy it will be for you to find where you are.  Just
go out to one of the small towns in your area.

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

Date: Mon, 18 Jul 1994 16:16:28 GMT
From: spsgate!mogate!newsgate![e-mail]
Subject: Dummy Load Oil
To: [e-mail]

I used mineral oil in mine. I got it at K-Mart at about $1/pint. The check-out
person gave me a funny look when I bought 8 bottles. Then I realized what it's
often used for (constipation:-).

Be aware that you have to de-rate the dummy load if you use drug-store mineral
oil. The transformer oil (be sure it's non-PCB) or the Texaco Turbine Oil is a
better choice if you're going to run a lot of power into the dummy load. The
Heath Cantenna has different rating curves for the different types of oil. For
your basic 100W transceiver, the K-Mart stuff is fine but for tuning your kW
linear, get the other stuff.

73...    Mark   AA7TA

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

Date: 19 Jul 1994 09:48:57 +0200
From: ihnp4.ucsd.edu!usc!math.ohio-state.edu!howland.reston.ans.net!ee.und.ac.za!ticsa.com!cstatd.cstat.co.za![e-mail]
Subject: Dummy Load Oil
To: [e-mail]

In article <[e-mail]>, Muenzler, Kevin wrote:
> Yes, mineral oil is a little expensive and is probably the
> safest to use in a dummy load.  Don't try anything like motor
> oil, it has many different types of lubricants that have
> different volatility.  The 'best' type of oil is "turbine oil."
> You can get it at many farm and ranch supply stores.  One of the
> easiest to find is sold by TEXACO distributors, Regal Oil R&O  Number
> 46.  You can usually find it in 5 gallon cans sold as "turbine oil."
> I don't know how easy it will be for you to find where you are.  Just
> go out to one of the small towns in your area.

My experience with dummy loads has shown that the cheapest and most
efficient oil to to use is Transformer oil. This is the oil used in
distribution transformers, as used by your power utility companies in the
USA. This is the same oil that we use in our oil-cooled welders here in
South Africa. I am sure you must have the same critter over there!

The oil in the dummy load is ostensibly used for cooling/heat dissapation,
and this what the oil in transformers and welders is there for.

Hope this info is useful to someone!!

Cheerio,

Brian  ZR5DTS                        Voice: ++27-31-7011201 (06:00-14:30 UTC)
Internet: [e-mail]          Fax:   ++27-31-7090813
VHF Packet: [e-mail]     ICBM's: 29:51:05 S  30:53:59 E
    *********************************************************************
I am glad I don't know everything, that way life isn't boring - Brian Ellse 94
    *********************************************************************

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

Date: Mon, 18 Jul 1994 14:26:58 GMT
From: ihnp4.ucsd.edu!swrinde!emory!cs.utk.edu!stc06.CTD.ORNL.GOV!xdepc.eng.ornl.gov![e-mail]
Subject: J-Pole Antenna
To: [e-mail]

In article <30cr0s$[e-mail]> [e-mail] (Jeffery L. Stutzman) writes:


>        Looking for information on building a J-pole antenna to cover the 80-10m
>bands. Recently bought a Kenwood TS-430, and want to try my hand at antenna
>making. Also any other suggestions for a vertical type antenna that can
>be made relatively easily/inexpensively. Very limited on space, so anything
>other than vertical is out.

>Thanks,
>        Jeff Stutzman (N1LUY)

Jeff,
      The classic J-pole design is a monobander.  Most trapped multiband
verticals, I have had experience with work slightly better than a Cantenna
(dummy load).  Most monoband verticals (full 1/4 wave or longer) verticals
with lots of ground radials (more than 20) have worked well for me.  I
have not tried the Cushcraft R5 or R7 but these seem to get mixed reviews
(rec.radio.amateur.antennas).

Unfortunately this probably does not solve your limited space problem.  Have
you considered a short G5RV or an inverted vee fed with open wire (450 ohm)
ladder line and a balanced line tuner?

73,
C. C. (Clay) Wynn N4AOX
[e-mail]

=========================================================================
= Cooperation requires participation.  Competition teaches cooperation. =
=========================================================================
       ..._  .. ..._  ._   _ . ._.. . __. ._. ._ .__. .... _.__

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

Date: Mon, 18 Jul 1994 16:28:00 GMT
From: newsflash.concordia.ca!pavo.concordia.ca![e-mail]
Subject: JOHANSON TRIMMERS?
To: [e-mail]

In article <[e-mail]>, Mike Lyon <[e-mail]> writes...
>i have been looking for a .3-3.5 pf trimmer that is made by johanson, or
>was at one time. i can not find any trimmer capacitor that tunes in this
>range. i need the type where it's a cylinder and it tunes in and out of
>the metal casing or ceramic what ever it is. if anyone knows where i
>could find such a beast it would be greatly appreciated.

That would be a type 5800 Johanson cap. They are available from Electrosonic
in Toronto, Canada. BUT...(there is ALWAYS a but) Their latest catalog lists
them at $16.34 for 1-24 quantity. Thats roughly $11.60 in Yankee dollars. If
you can stomach that kind of price tag, their number is [phone], ask
for the order desk. BTW the price has almost certainly risen slightly :-)

Good luck,

Mark

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

Date: 18 Jul 94 18:42:42 GMT
From: [e-mail]
Subject: Kenwood TR2500 mods
To: [e-mail]

     Does anyone have a manual for a Kenwood TR2500 2meter FM rig?

     This is an old rig that was set up for 15KHz channels.  I have
     modified it for 10 Khz spacing with a new crystal, but it needs new
     programming for the PLL.  Unfortunately, when my new (then) wife and I
     cleaned up the shack we must have thrown out the repair manual I had
     for it, so I dont know what the pin outs are on the PLL board.

     Thanks in advance

     Ray
     WD5IFS
     [e-mail]

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

Date: Mon, 18 Jul 1994 08:53:22 GMT
From: news.Hawaii.Edu!kahuna![e-mail]
Subject: QRP Mail List (was: Building an HW-9: HALP!)
To: [e-mail]

In article <30d70k$[e-mail]> [e-mail] (Mike Cummings) writes:
>
>Also, I keeo hearing mention of either a QRP mailing list or newsgroup;
>Could someone direct me there?  Thanks!

The QRP email list is a wonderful forum. To subscribe send an email to:
               [e-mail]
and only write:
               subscribe qrp
or:
               subscribe qrp-digest
and within a few minutes you'll receive an email from think.com
welcoming you to the net. Note that the digest will consist of
all the day's articles sent in bulk; otherwise you'll receive
each article as a seperate email. Expect about 20 articles
per day. There's some famous folks on the list - plenty of
help available for any problem you might have regarding:
antennas, homebrew, kits, and any other qrp-related items.

.73,
Jeff NH6IL

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

Date: 18 Jul 94 18:32:25 GMT
From: [e-mail]
Subject: reply to N6MHG
To: [e-mail]

     Ken:
        On rewinding power transformers:  You might look seriously at some
     of the power toroids for ease of rewinding.  I have never tried it but
     at the local surplus place they usually have several varieties of
     power toroids.  If the secondary is on top of the primary it should be
     fairly easy to get to the secondaries to rewind them.  The other
     advantage (as these are usually high voltage secondaries) is that you
     can rewind them with much larger wire with a more manageable number of
     turns.  The biggest problem will probably be getting the old secondary
     off.


     Ray
     WD5IFS
     [e-mail]

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

Date: 18 Jul 94 18:37:30 GMT
From: [e-mail]
Subject: reply to several
To: [e-mail]

     To N6MHG:

     Ken:
        I am using wal-mart mineral oil in my Heath dummy load.  So far it
     is still 50 ohms and still dissipating energy!


     To The chemical thread:

        Iso-butane is butane that is "twisted" .  It is different from
     regular butane only in its physical structure.  You should be aware
     that the propellant in a lot of aerosols these days is butane!  I
     believe that this is true for hair spray.  That is one reason it burns
     so well ( in addition to the laquer in it).

     To Joe Landis:

        Why not just remove the preformed contacts from coin cell sockets
     and modify them for your use.  The pressure exerting surface is
     already what you need!


     Ray
     WD5IFS
     [e-mail]

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

Date: 18 Jul 1994 15:05:29 -0400
From: ihnp4.ucsd.edu!swrinde!howland.reston.ans.net!news.intercon.com!news1.digex.net!digex.net![e-mail]
Subject: Rolling my own Transformer (LONG)
To: [e-mail]

>Could someone point me the right direction to finding information about
>"rolling my own" power transformer?  Seeing as how I don't really have $95 to
>plunk down for a transformer and I do have a couple of pretty good surplus
>electronics stores nearby, I was wondering what might be involved with
>purchasing a hefty transformer on a goofy voltage and "playing".  I've seen
>some big 'uns down at these stores for much, much less than $95 (say $15 - $20)
>and I'm sure I would have no problem removing their present windings...  It
>would give me that much more "home grown" stuff to brag about. :-)
>
>Thanks in advance--
>Ken Harrison
>N6MHG
>email:  [e-mail]
>

I have modified transformers at times with good results. Maybe some
knowledgeable person can shed more light on the subject.  The following
relates my experience only. Your mileage may vary 8). All disclaimers
apply. I am assuming you have related knowledge and feel competent
doing something like that...


Assumptions:
 0) You are not trying to put together a transformer from scratch!
    The most difficult part of doing is finding out about the core material
    (magnetic properties ) which seems impossible to find for an old
    transformer.

 1) What you intend to modify, is an ordinary non-saturating core xformer
    with its primary being fed from an AC outlet (110 and/or 220 volt
    household supply), and you don't intend to mess with the primary.

 2) It is not an "autotransformer" - i.e., its primary winding(s) are
    separate from its secondary winding(s), there is no electrical
    connection between the two.

 3) The intent is to vary the secondary voltage *somewhat*, for example ,
    you are not trying to have a 40 volt secondary put out 800 volts.
    (not only that may be physically impossible for a given geometry,
    it may have repercussions regarding breakdown voltages, heat
    dissipation and such.)

 4) You *know* the power rating of the transformer's secondary (BTW, I'm
    theoretically not inclined, or challenged depending on how you look at it.)
    You know for example that the secondary supplies say 12 volts at 2.5
    amps max. (AC, RMS, given Frequency, pure sinusoid, constant phase,
    etc. etc.)

Opening up a transformer is best left as an exercise for the reader!
If it is dipped in tar(!?), I'd say forget it.
Don't scratch or bend the strips. They are laminated for a reason.
If you pry them off carelessly and damage the lamination/coating or bend them,
you are likely to affect the power handling, cause the core to heat up more
than it is supposed to, and/or make the xformer "buzz". A
practice run on a small low-power transformer maybe worthwhile.

The basic idea is to get what is called "turns per volt" for the secondary
(# of turns that give 1 volt at the secondary.) The reverse (i.e., voltage
per single turn) will also work but I think is less accurate unless you're
in a lab environment.)
It may involve some guessing initially, and the more experience you
have, the better your guess will be. Try to estimate, by looking at the
secondary winding how many turns it has.
A rough guess is fine. Divide that by the secondary's voltage.
Then wrap *neatly* the number of turns that you calculate, to produce say
a couple of volts or so. Another method that's more accurate, is
to unwind (a) secondary completely, and count the number of turns,
and then do the division. I am almost sure there are some nonlinearities
in practice, but for the most part, the relationship is linear and
gives a good approximation. If you wrap n turns, you get m volts.

Using the information, you can wrap your experimental winding, preferably
for a few volts. Write down your exact # of turns. Then put back the whole
thing (carefully). All of the strips should be put back. And the whole
thing should  be neat and tidy. I have used electrical tape to hold the
temporary secondary (experimental) winding. If you left the original
secondary winding in place, your experimental secondary could
be wrapped on top of it (space permitting). Then connect the primary and
measure with a good voltmeter, the voltage of your experimental winding.
A high valued resistor as a load on the secondary to draw a few milliamps may
be good idea too. Get a second estimate of the turns per volt by dividing
the # of turns by voltage. Then, calculate the number of turns you need to wrap
for your new secondary (# turns= turns per volt value * desired voltage.)
Keep in mind the space limitations for winding extra wire if that's what's
needed. Open up the thing again, remove the experimental winding.


If you intend to increase the voltage, you must derate the current the
secondary can supply. Moving too much above or below what the transformer
was designed for is in my opinion not a good idea, and it's kind of hard
to tell what those limits are when no data is available. Another concern
is the space you have for re-wrapping the wire. The most important
thing, however, is to keep the power rating of the xformer the same. Example:

 Originally: secondary 10 volts, with max current 2.5 amps.
 New desired secondary voltage: 17 volts.
 P orig = 10 * 2.5 (RMS values)  = 25 watts.
 (or maybe we should talk about Volt-Amperes instead of watts -:) -:))
 New max secondary current = 25 / 17 = about 1.4 amps.
 So at 17 volts you should not expect to draw more than about 1.4 amps.

 [ This space is left for theoretical gurus. Please go ahead. ]


The estimated max current gives you an idea of the wire gauge you need.
Use fresh wire of a diameter that can handle the current you need the
secondary to supply. Look at tables (for example in the arrl handbook) that
show the values for various gauges of copper wire, and be as conservative
as possible (i.e., use larger diameter wire - if there is enough space for
the whole winding).

footnote: There is an iterative process here if you want to determine the
limits, because you can increase the voltage (when not demanding high
current) and use thinner wire and that in turn may buy more winding space.)
The inverse is also true. (Sometimes there are tables that can be used to
estimate how many strands of wire of a given gauge can be put side-by-side in
a given cross-sectional area.)

Of course if you intend to lower the voltage, your max current capacity goes
up, and if that's what you want, you need larger gauge wire. There is a
limit as to how much current can be drawn with a given xformer before
saturating the core material, overheating and the associated anomalies.
Deviating with a few percent of the rating may be ok.

Wrap the winding tight and with care, so as *not to nick the lamination of
the wire*. Put Q-dope or use a good quality insulating varnish over each
layer. For higher voltages, it is essential to use a varnish with high
dielectric properties (high breakdown voltage) or else one layer may arc
over to another. You may even have to have "varnished paper" insulation
between layers. Put back the final wrapping insulating "papers", etc.
BTW: can someone point to a source of that paper/wrapping material ?

After a couple of times, you can skip the trial winding too.
I usually wrap a few more turns, put the thing together, measure the voltage,
and trim as necessary before finishing up.

All comments and corrections welcome - I don't rewind transformers that often!!!

** Be careful and use applicable precautions and good judgment when around
   lethal voltages (or should I say currents,... or power -:)) **


Good Luck,

/siamack


--
Siamack Navabpour    [e-mail]
73 de wj1q

"He who bends to himself a joy, Will the winged life destroy
 But he who kisses the joy as it flies, Will live in eternity's sunrise"
 -- Willy Shakespeare

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

Date: Mon, 18 Jul 1994 13:49:29 GMT
From: ihnp4.ucsd.edu!swrinde!emory!rsiatl!ke4zv![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <[e-mail]>
Reply-To : [e-mail] (Gary Coffman)
Subject : Re: RSGB BOOK

In article <[e-mail]> [e-mail] (Zack Lau (KH6CP)) writes:
>Gary Coffman KE4ZV ([e-mail]) wrote:
>
>: While I agree that the general literacy level in this country is
>: low, bad writing is not so much the technical innovator's fault
>: as it is the technical *editor's* fault. It's his job to work with
>: the author to put the manuscript into a coherent and literate form.
>
>But, what if there is *no* technical editor?  One of the best places
>to find out about the latest innovative projects is conference
>proceedings, which don't have the lead times associated with
>editing.

Then we suffer through the bad writing. That's a different thing
than the Handbooks we were discussing where there *is* an editor
responsible for the book.

Note I'm not trying to slam ARRL book editors here. It's a thankless
enough job already. I suspect that the ARRL editors are no less
skilled than their RSGB counterparts, but the raw material they
have to work with may be less polished.

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     |

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

End of Ham-Homebrew Digest V94 #201
******************************