QRZ! Ham Radio 4/QRZ Ham Radio Callsign Database - Volume 4.iso/digests/homebrew/940015.txt

Internet Message Format | 1994-11-13 | 22KB

Date: Mon, 31 Jan 94 04:30:54 PST
From: Ham-Homebrew Mailing List and Newsgroup <[e-mail]>
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Reply-To: [e-mail]
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Subject: Ham-Homebrew Digest V94 #15
To: Ham-Homebrew


Ham-Homebrew Digest         Mon, 31 Jan 94       Volume 94 : Issue   15

Today's Topics:
                    Antenna pre-amp design. Help!
                 Antenna Tuner Project Advice Needed
                      High Voltage Power Supply
                  Old Radio Elec/Pop Elec Magazines
                    Oscillators using MMIC's Amps
        PROJECT 14: THE WORLD'S SMALLEST TRANSMITTER (2 msgs)
         Reciprocal mixing at 25 kHz, ICF-2010 Help! (2 msgs)
                         spot my transistor.
                    The World's Smallest Receiver
                want to build reciever for 108-137Mhz

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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: Sat, 29 Jan 1994 19:58:22 GMT
From: sdd.hp.com!usc!elroy.jpl.nasa.gov!swrinde!emory!gatech!udel!news.intercon.com!psinntp!psinntp!psinntp!arrl.org![e-mail]
Subject: Antenna pre-amp design. Help!
To: [e-mail]

[e-mail] wrote:
: Hi,

:     Can anyone here give me some advice on building an antenna pre-amp
: for working 4 - 24 mHz? Should I go broadband or switched bands? What about
: pre-filtering?

The front end input preamplifier on page 25 of the February 1993 QST
might be a good compromise, offering 8 dB of gain and a 2 dB noise figure.
There is a good chance it will cover the entire 4 to 24 MHz spectrum as is.
A deficiency of this design is the necessity for good output matching--a
poor output match will degrade performance.

I prefer to use narrowband, fixed tuned filters, though there are
advocates of tunable filters.

:     What are the advantages of designing one around bi-polar or mosfet?
: Can anyone contribute some tried and tested circuits for me to construct?

A problem with designing low noise HF preamps is that few, if any, devices
are optimized for this task.  MOSFETs were primarily designed for use at
VHF and low UHF--specifications on HF noise figures seem non-existant.  I
suspect that were someone to invest the $$$ for a really optimized device,
sub 0.5 dB NFs are possible.  Occasionally, you can find bipolars optimized
for low VHF, such as the NEC 41603/2SC1949, touted as having a 1 dB NF at
70 MHz.  The usual problem is excessive gain, which requires some form
of lossless feedback to reduce without degrading noise figure.
Theoretically, directional couplers could be used to implement feedback, but
I've not seen published circuits to duplicate.

--
Zack Lau  KH6CP/1           2 way QRP WAS
                           8 States on 10 GHz
Internet: [e-mail]   10 grids on 2304 MHz

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

Date: 27 Jan 1994 15:34:50 GMT
From: usc!cs.utexas.edu!utah-morgan!hellgate.utah.edu!fcom.cc.utah.edu!u.cc.utah.edu!titan.wordperfect.com!xmb![e-mail]
Subject: Antenna Tuner Project Advice Needed
To: [e-mail]

Bruce Pea ([e-mail]) wrote:
: I'm getting ready to put a dipole up and use ladderline to
: feed it. I'm going to need an antenna tuner so I can tune
: this wire across 160-10m.

: I thought building a tuner would be a nice winter project.
: Do any of you have a favorite tuner project you would like
: to point me to?? My rig is an ICOM IC-740, 100 watts out.

: Thanks for the help!

: Bruce

Richard Measures, AG6K, wrote an article in the Feb. 1990 QST about a
balanced antenna tuner, made for just such an antenna system as you
describe.  The balun is at the input of the tuner (i.e., between the
transmitter and the tuner).  The tuner itself consists of two roller
inductors for the series reactances and a variable capacitor for the
shunt reactance.

         +----+
         |    v L1
         +-((((((--+-------
         |         |/
---     -+       -----
   balun         ----- C1   --> to ladder line
---     -+        /|
         |         |
         +-((((((--+-------
         |   ^ L2
         +---+

The roller inductors are mechanically ganged by a belt and pulleys on
the inductor shafts.  The idea of a balanced tuner feeding a balanced
transmission line to a balanced antenna is appealing...

--
Michael Bendio     WT7J       [e-mail]          801 222-5367
Opinions are my own and aren't necessarily shared by Wordperfect Corporation

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

Date: Sat, 29 Jan 1994 00:20:52 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!gatech!swrinde!sgiblab!sgigate.sgi.com!olivea!news.bu.edu!news.bbn.com!petra!zds-oem![e-mail] (Earl Morse)
Subject: High Voltage Power Supply
To: [e-mail]

In article <[e-mail]> [e-mail] (Jim Hollenback) writes:
>Martin Stille ([e-mail]) wrote:
>: Hi OM`s
>
>: I need a high voltage power supply for a tube PA.
>: But I can`t find the right schematic and part list.
>: The tube runs with a current of 7000V and 2Amp.
>: I hope you can help me.
>: Thank's Martin
>
>hmmm, 7kv x 2 amp, about 14kw on the plate....thats one healthy afterburner.
>You should be worried about the coax feed also.
>
Even at 50 percent efficiency that will take out just about any commercially
available ham antenna and the standard feed lines.  Serious competition for
Peter I this week though.

Earl Morse
KZ8E
[e-mail]

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

Date: 27 Jan 94 06:54:07 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!uchinews!msuinfo!harbinger.cc.monash.edu.au!bruce.cs.monash.edu.au!merlin!mel.dit.csiro.au!its.csiro.au!dmssyd.syd
Subject: Old Radio Elec/Pop Elec Magazines
To: [e-mail]

There has been some activity at around 150 kHz in Australia and
New Zealand. Circuit diagrams and construction notes has been
published in Amateur Radio, which is official WIA magazine. I don't
have any exact references at hand, but some articles has appeared
during 1993. You can get copies of this journal from WIA: Amateur Radio,
P.O.Box 300, Caulfield South, VIC 3162, Australia.

The only reference at hand is: Lloyd Butler (VK5BR, addr. 18 Ottawa Avenue,
Panorama, SA 5401, Australia) - A Bandwidth Limiting LF Up Converter
for Frequencies Around 200 kHz. Amateur Radio, December 1993, p. 4-7

In fact, this article contains references to: Butler - VLF-LF and the
Loop Aerial, (aerial is antenna here ...) Amateur Radio, Aug. 1990 and
John Adcock (VK3ACA) - The day we crossed the Tasman on Long Wave,
Amateur Radio, April 1993 (Crossing Tasman sea means contact to NZ)

I have faint idea about these US magazines. The LF articles were
quite good, but in this respect I can not help.

I hope this helps.

Sakari Mattila    [e-mail]     The University of New England
(VK2XIN, OH2AZG)  tel. [phone]           Armidale NSW 2351,  Australia
P.O.Box u13       ----------------------------------------------------------
Armidale NSW 2351
------------------

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

Date: 27 Jan 94 07:02:21 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!vixen.cso.uiuc.edu!uchinews!msuinfo!harbinger.cc.monash.edu.au!bruce.cs.monash.edu.au!merlin!mel.dit.csiro.au!its.csiro.au!dmssyd.syd
Subject: Oscillators using MMIC's Amps
To: [e-mail]

There was a series of articles about VHF - UHF crystal oscillators
build around MMIC amplifiers (Mini-Circuit, Avantek and some Japanese
ICs) in the RF Design (USA) journal about 1989 - 1992, most probably
1991. The main idea was to make the oscillator to work directly at 100
- 500 MHz. In some circuits, the author used special, low capasitance
crystals.

Sakari Mattila     [e-mail]   The University of New England
P.O.Box u13        tel. [phone]         Armidale NSW 2351,  Australia
Armidale NSW 2351  (VK2XIN, OH2AZG)           -----------------------------
Australia          ---------------------------
------------------

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

Date: Fri, 28 Jan 1994 15:13:57 GMT
From: library.ucla.edu!europa.eng.gtefsd.com!howland.reston.ans.net!usenet.ins.cwru.edu!nshore!seastar![e-mail]
Subject: PROJECT 14: THE WORLD'S SMALLEST TRANSMITTER
To: [e-mail]

As quoted from <[e-mail]> by [e-mail] (Dana Myers ):

> In article <[e-mail]> [e-mail] (Jeff Herman) writes:
> >Gang,
> >   If there was a contest to come up with a xmtr containing as few
> >parts as possible, this would be the winner: 10 parts if you include
> >the key, battery, and antenna!
>
> I can beat this.
    Me too.
> >   I built this for 80M only because I've got so many 3579 kHz crystals
> >from old TV sets, but this can be used on any HF band - just choose
> >L and C to resonant at the crystal frequency.
>
> Try using a 4049 or 74C04; use one inverter as a crystal osc (two
> caps + crystal) and the other five in parallel as a buffer.  Use a small
> cap to couple the antenna, maybe 100pF.  It'll run off 3-15V. Lessee..
> xtal+74C04+caps+battery+key+antenna = 8 parts.
>
> The 74C04 was invented in something like 1973.
    Try using a 28.322MHz oscillator (or a14 or 7 meg that I've
seen occasionally that are still in the Ham bands). Low-pass filter
this as well, and you need battery+key+oscillator+3xLPF components.
Note that these oscillators are usually not a 50% duty cycle, so a
bandpass filter would be better.
> >   For peace of mind you might want to add a bandpass filter to the
> >output.
>
> or maybe a lowpass filter; that adds at least three more components.
> The 74C04 approach would really benefit from an LPF, too.

    Of course, taking that approach to extremes, use an Alinco
DJ580.  It is all one 'piece', including the battery, key and antenna
;-)

--
John Welch, N9JZW

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

Date: 25 Jan 1994 05:58:14 GMT
From: unogate!news.service.uci.edu!usc!howland.reston.ans.net!cs.utexas.edu!swrinde!sgiblab!sgigate.sgi.com!olivea!koriel!male.EBay.Sun.COM!newscast.West.Sun.COM!abyss.West.Sun.@@mvb.saic.com
Subject: PROJECT 14: THE WORLD'S SMALLEST TRANSMITTER
To: [e-mail]

In article <[e-mail]> [e-mail] (Jeff Herman) writes:
>Gang,
>   If there was a contest to come up with a xmtr containing as few
>parts as possible, this would be the winner: 10 parts if you include
>the key, battery, and antenna!

I can beat this.

>   I built this for 80M only because I've got so many 3579 kHz crystals
>from old TV sets, but this can be used on any HF band - just choose
>L and C to resonant at the crystal frequency.

Try using a 4049 or 74C04; use one inverter as a crystal osc (two
caps + crystal) and the other five in parallel as a buffer.  Use a small
cap to couple the antenna, maybe 100pF.  It'll run off 3-15V. Lessee..
xtal+74C04+caps+battery+key+antenna = 8 parts.

The 74C04 was invented in something like 1973.

>   For peace of mind you might want to add a bandpass filter to the
>output.

or maybe a lowpass filter; that adds at least three more components.
The 74C04 approach would really benefit from an LPF, too.


Oh, is this a CW issue? :-)

--
 * Dana H. Myers KK6JQ, DoD 466    | Views expressed here are    *
 * [phone]         | mine and do not necessarily    *
 * [e-mail]    | reflect those of my employer    *
 * This Extra supports the abolition of the 13 and 20 WPM tests *

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

Date: Fri, 28 Jan 1994 23:11:03 GMT
From: ucsnews!sol.ctr.columbia.edu!howland.reston.ans.net!newsserver.jvnc.net!raffles.technet.sg!ntuix!ntuvax.ntu.ac.sg![e-mail]
Subject: Reciprocal mixing at 25 kHz, ICF-2010 Help!
To: [e-mail]

Hi,

    I am experiencing reciprocal mixing of signals on my SONY
ICF-2010/2001D at about 24 or 25 kHz above the actual signal image.
Is there something i can do to fix this? Tks.

73 de 9V Daniel

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

Date: 29 Jan 1994 15:50:53 GMT
From: library.ucla.edu!agate!usenet.ins.cwru.edu!neoucom.edu!news.ysu.edu!yfn.ysu.edu![e-mail]
Subject: Reciprocal mixing at 25 kHz, ICF-2010 Help!
To: [e-mail]

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

>Hi,
>
>    I am experiencing reciprocal mixing of signals on my SONY
>ICF-2010/2001D at about 24 or 25 kHz above the actual signal image.
>Is there something i can do to fix this? Tks.
>
>73 de 9V Daniel
>

Steve Whitt mentions a rather detailed (but simple) fix in his book
involving replacing or adding 3 or 4 capacitors in the radio's IF
section.  It DOES involve moving a shield and some pretty detailed
solder work so it isn't for the feint of heart or those with limited
soldering experience though!

  Has ANYONE reading this group done the mod to see how it performs?
I haven't yet -- and have been trying to see if anyone else has before
I tackle it to see if it really does make a difference.  I have been
getting more and more annoyed by the background "rumble" on 49 metres
in the evenings here, and would like to try the mod sometime t see
if it helps.

73  //kvz
--
kv zichi -->[e-mail]
            despite what the address above may say!

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

Date: 30 Jan 94 17:09:04 GMT
From: netnews.upenn.edu!netnews.noc.drexel.edu!dunx1.ocs.drexel.edu!dunx1![e-mail]
Subject: spot my transistor.
To: [e-mail]

hello all.
    i'm working on a variable power supply (3-15V) for my sw radios.
i've gotten my hands on what looks like a good schematic.  however, being
new at this, i can't figure out the (specific) transistors it requires.
there are two: an NPN and a HEP 232.
    the most convenient place for me to get such pieces is at a local
radio shack.  ..the catalog has alot of transistors...all marked either NPN
or PNP.  i haven't spotted a HEP 232 (?).  which one do i need?  it gives
no voltage specs or anything.  can i use just any old NPN?  any help would
be appreciated.  thanks.


______________________________________
antonio gatta
[e-mail]

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

Date: Sun, 30 Jan 1994 16:54:04 GMT
From: sdd.hp.com!usc!howland.reston.ans.net!gatech!wa4mei.ping.com!ke4zv![e-mail]
Subject: The World's Smallest Receiver
To: [e-mail]

In article <[e-mail]> [e-mail] (Bob Sivyer) writes:
>Jeff Herman's post about the world's smallest transmitter seems to have
>stirred up considerable interest.  Does anyone have a collection of simple
>receiver circuits that could be paired with Jeff's transmitters.  I would
>like to build a QRP station but have been away from building things for some
>time.

Ok, top this great low power AM reciever for parts count.

Long wire antenna  coil
--------------------)    diode    crystal earphone
                    )<----->|-------()--Gnd
                    )

Wind the coil on a toilet paper tube or a Quaker Oats box. The variable
tap is the "tuning" adjustment.  Volume is controlled by how deeply you
stick the earphone in your ear. While this receiver is optimized for
AM voice, it'll work for Morse too if the matching transmitter is spark.

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     |                     |

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

Date: 30 Jan 1994 08:01:09 GMT
From: haven.umd.edu!news.umbc.edu!europa.eng.gtefsd.com!howland.reston.ans.net!vixen.cso.uiuc.edu!uwm.edu!caen!malgudi.oar.net!infinet![e-mail]
Subject: want to build reciever for 108-137Mhz
To: [e-mail]

Chad Berthelson ([e-mail]) wrote:
: As the subject line says, I want a tunable receiver that will pick
: up Air Bands (108-137 Mhz).

You can convert any standard Broadcast FM reciever to get Aircraft. To do
so is a matter of spreading the tuning coil (a length of copper wire in a
coil, usually coated with wax) out pretty much as far as they can go.
(Evenly spaced between the coils), which raises the frequency range, then
using a small screwdriver, turn the pot (Little metal box with plastic
screw in it) that's closest to the tuning coil until the most noise is
heard on an un-used freq. That changes the mode from FM r/x to AM r/x.

You can get a cheap am/fm radio for about 10 bucks at Radio Shack.


Hope this helps!
Kristopher Hurt
[e-mail]

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

Date: Thu, 27 Jan 1994 17:23:36 GMT
From: mvb.saic.com!unogate!news.service.uci.edu!usc!howland.reston.ans.net!europa.eng.gtefsd.com!emory!wa4mei.ping.com!ke4zv![e-mail]
To: [e-mail]

References <[e-mail]>, <[e-mail]>, <2i66g2$[e-mail]>m
Reply-To : [e-mail] (Gary Coffman)
Subject : Re: Antenna pre-amp design. Help!

In article <2i66g2$[e-mail]> [e-mail] (Ignacy Misztal) writes:
>[e-mail] (Gary Coffman) writes:
>>In article <[e-mail]> [e-mail] writes:
>>>    Can anyone here give me some advice on building an antenna pre-amp
>>>for working 4 - 24 mHz? Should I go broadband or switched bands? What about
>>>pre-filtering?
>
>>Normally, a preamp is unnecessary for the HF spectrum. The usual problem
>>is inadequate rejection of strong signals. However, if you've got an old
>>deaf receiver, like say a S-28, a preamp may help. You definitely want to
>>use a selective amplifier with good sharp tuned circuits. A triple ganged
>>circuit would be a good idea. Otherwise your preamp will operate in overload
>>most of the time.
>
>A preamp may be needed for upper bands if bands are quiet and antennas
>not spectacular. A single tuned circut would cut out a mirror frequency
>pretty well. Once I build a one-transistor preamplifier with one tuned
>circuit, and it made a large difference on my SWAN 500.

SWAN 500. Well yeah, a preamp could help a SWAN. :-)

>>>    What are the advantages of designing one around bi-polar or mosfet?
>>>Can anyone contribute some tried and tested circuits for me to construct?
>
>>FETs would be the more popular choice. You can tap up on the selective
>>circuits for lighter loading, hence higher Q, with less problems with a
>>FET. The old MPF102 would work for this type of circuit, but it can
>>be driven rather easily into overload. A power VMOS FET like the VMP-4
>>may be a better choice. Run about 100 ma of standing current.
>
>MOSFETs and FETS may have too low gain to drive the coax. Large-signal
>properties of a RF amplifier are not terribly important, especially
>with the tuned front. It is usually the mixer that is more susceptible to
>overloading.

Actually, the problem with modern Mosfets is in taming the *excess*
gain they possess. Many have 15-20 db of gain well into the gigahertz
region, and gain suffers a 3 db increase for every octave frequency
decrease. So at HF they're generally hotter than firecrackers. You
don't want more than 10-15 db of gain in a preamp or you'll definitely
overdrive most HF rigs into distortion and intermod. It's also a fact
of life today that strong signal handling has become the major problem
at HF. Using either very selective networks, or amplifiers with strong
signal handling characteristics, or both, is a must. Most modern receivers
use a DBM first mixer with +8 dbm or greater LO injection, so mixers aren't
the weak link anymore.

>>In looking through my collection of ARRL Handbooks, I don't find a
>>HF preamp until I go back to the 1962 edition. They have one using
>>a 6AK5 pentode. This should give you an idea of the apparent lack
>>of need for such circuits with more modern equipment.
>
>The problem of unproper gain distrubution in various stages is still a
>problem. Look at smaller ICOMs, where you can hear plenty of noise from
>the IF stages, particularily with a CW crystal filter in the first IF.
>Intermods spoil the reception sometimes, but such a noise spoils it
>much more often. Sometimes I would like to have more RF gain
>in my IC-735 on 10-20m. Perhaps my antennas are not spectacular.

Indeed. With my IC-735, atmospheric noise dominates the quiet channel.
Of course channels are rarely quiet. A good antenna is always a must
for proper performance.

>>If the problem is that you are using a small voltage probe antenna,
>>a FET configured as an emitter follower mounted directly on the
>
>>something more to the liking of the receiver and coax. Again run
>>enough standing current to avoid overload problems.
>
>Emitter followers driving a coax are excellent oscilators.

They can be, if not properly designed. But this is more a problem
with low impedance bipolar circuits than with FETS. Adding additional
degenerative feedback in the emitter circuit will tame this problem.
The FET will have more gain than you want anyway, so this is a viable
solution.

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     |                     |

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End of Ham-Homebrew Digest V94 #15
******************************