QRZ! Ham Radio 5/QRZ Ham Radio Callsign Database - Volume 5.iso/digests/homebrew/940148.txt

Internet Message Format | 1994-11-13 | 15KB

Date: Thu,  2 Jun 94 04:30:28 PDT
From: Ham-Homebrew Mailing List and Newsgroup <[e-mail]>
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Subject: Ham-Homebrew Digest V94 #148
To: Ham-Homebrew


Ham-Homebrew Digest         Thu,  2 Jun 94       Volume 94 : Issue  148

Today's Topics:
     Getting a VFO on-frequency (W1FB Design NB p. 111) (3 msgs)
           Phase noise floor of Motorola CMOS PLL dividers
                      QRP mailing list? (3 msgs)
         Schematics for Luxor 1909530, Magnum Microwave c24-3
                simple SSB receiving methods (2 msgs)
                          Techno Whizzy DDS

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

Date: 1 Jun 1994 12:09:34 GMT
From: ihnp4.ucsd.edu!usc!howland.reston.ans.net!usenet.ins.cwru.edu!po.cwru.edu![e-mail]
Subject: Getting a VFO on-frequency (W1FB Design NB p. 111)
To: [e-mail]

I'm working on the DC receiver on page 111 of _W1FB's Design Notebook_
as a first homebrew project.  It sure has been educational...  :-)
The current problem is that the VFO insists on operating around 5.5 MHz.
I need it up around 7 MHz if this is going to be a 40m receiver.  It's
a JFET Hartley VFO with a 4.8 uH inductor tapped 1/4 of the way up for
feedback, 100-125 pF of tank capacitance, and a 100 pF capacitor coupling
the top of the tank circuit to the JFET gate.  I'm using an MPF102 for
the JFET.  The circuit is built dead bug style.

The values shown for the oscillator work out to 6.5 MHz to 7.25 MHz if I
ignore the 100 pF gate capacitor.  How much is that capacitor going to
pull the frequency?

Does the design look sound, in general?  I double-checked my wiring
and component values several times.  Any other suggestions for things I
should check?

          Stephen

--
Stephen Trier
[e-mail]
KG8IF

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

Date: 1 Jun 1994 17:00:39 -0700
From: nntp.crl.com!crl.crl.com![e-mail]
Subject: Getting a VFO on-frequency (W1FB Design NB p. 111)
To: [e-mail]

In article <2shtpu$[e-mail]> [e-mail] (Stephen C. Trier) writes:
>The current problem is that the VFO insists on operating around 5.5 MHz.
>I need it up around 7 MHz if this is going to be a 40m receiver.  It's
>a JFET Hartley VFO with a 4.8 uH inductor tapped 1/4 of the way up for
>feedback, 100-125 pF of tank capacitance, and a 100 pF capacitor coupling
>the top of the tank circuit to the JFET gate.  I'm using an MPF102 for
>the JFET.  The circuit is built dead bug style.
>The values shown for the oscillator work out to 6.5 MHz to 7.25 MHz if I
>ignore the 100 pF gate capacitor.  How much is that capacitor going to
>pull the frequency?

Have you tried spreading or squeezing the wires together on the inductor?
I think he mentions somewhere in his book that you might have to do that.
Hope this helps!

Jeff

--
Jeff Jones AB6MB
[e-mail]

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

Date: 2 Jun 1994 07:13:07 -0400
From: newstf01.cr1.aol.com!search01.news.aol.com![e-mail]
Subject: Getting a VFO on-frequency (W1FB Design NB p. 111)
To: [e-mail]

In article <2sj7f7$[e-mail]>, [e-mail] (Jeff Jones)
writes:

>The current problem is that the VFO insists on operating around 5.5
MHz.
>I need it up around 7 MHz if this is going to be a 40m receiver.
It's
>a JFET Hartley VFO with a 4.8 uH inductor tapped 1/4 of the way up
for
>feedback, 100-125 pF of tank capacitance, and a 100 pF capacitor
coupling
>the top of the tank circuit to the JFET gate.  I'm using an MPF102
for
>the JFET.  The circuit is built dead bug style.
>The values shown for the oscillator work out to 6.5 MHz to 7.25 MHz
if I
>ignore the 100 pF gate capacitor.  How much is that capacitor going
to
>pull the frequency?


It has been my experience that you'll need to play with either
squeezing the inductor windings closer together (or moving them
farther apart), or try some different caps to get resonance at the
correct freq.  You also might try a small trimmer at the gate (rather
than the 100 pF) to find  a value that doesn't pull the freq, but
allows reliable start up.  Stray capacitance and inductance is
probably the culprit here.   This is what experimenting is all about.
Don't get frustrated (I did, it doesn't help)--just play with it
until it works!

Good Luck


72 (+/- 1) Jim N0OCT

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

Date: 1 Jun 1994 21:43:40 GMT
From: ihnp4.ucsd.edu!usc!elroy.jpl.nasa.gov!lll-winken.llnl.gov!koriel!newsworthy.West.Sun.COM!abyss.West.Sun.COM!sunspot![e-mail]
Subject: Phase noise floor of Motorola CMOS PLL dividers
To: [e-mail]

Does anyone have empirical information on the phase noise floor of the
dividers in the Motorola CMOS PLL chips, such as the MC145157 and MC145170?
I'm tending to guess towards -150dBc, a number I've seen published for
CMOS dividers, but is this accurate?

This is of particular interest with respect to the on-chip reference
divider in the Motorola CMOS PLLs.  I would guess the phase noise
level of the reference frequency, when driven with the on-chip oscillator
using a crystal, is going to be primarily determined by the divider.

Any comments?

---
 * Dana H. Myers KK6JQ, DoD#: j    | 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: Wed, 1 Jun 1994 19:28:20 GMT
From: ihnp4.ucsd.edu!swrinde!cs.utexas.edu!wotan.compaq.com!twisto.eng.hou.compaq.com![e-mail]
Subject: QRP mailing list?
To: [e-mail]

Is the QRP mailing list still around?

73,

Brad
[e-mail]

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

Date: Wed, 1 Jun 1994 22:19:47 GMT
From: ihnp4.ucsd.edu!usc!nic-nac.CSU.net!charnel.ecst.csuchico.edu!yeshua.marcam.com!news.kei.com!uhog.mit.edu!news.mtholyoke.edu!news.unomaha.edu!cwis![e-mail]
Subject: QRP mailing list?
To: [e-mail]

In <77049530034n12@131.168.114.12> Brad=Staff%PC=SW%PCPD=[e-mail] writes:

>Is the QRP mailing list still around?

>73,

>Brad
>[e-mail]

As far as I know it is.  Check my Elmers Directory (just posted to
rec.radio.info) for more info.

73, Paul W. Schleck, KD3FU

[e-mail]

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

Date: 1 Jun 1994 16:55:37 -0700
From: nntp.crl.com!crl.crl.com![e-mail]
Subject: QRP mailing list?
To: [e-mail]

>In <77049530034n12@131.168.114.12> Brad=Staff%PC=SW%PCPD=[e-mail] writes:
>
>>Is the QRP mailing list still around?
>
>>73,
>
>>Brad
>>[e-mail]

To subscribe to the QRP mailing list do the following;

email to [e-mail]

Subject: You can leave it blank

subscribe qrp or unsubscribe qrp to quit receiving it.

It is automated so you will receive an reply telling you that they got it.
Then shortly there after and sometimes along with it you will receive
the QRP mailing list. There are new messages constantly being sent as it
is very active.

Jeff
--
Jeff Jones AB6MB
[e-mail]

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

Date: 1 Jun 1994 21:35:08 GMT
From: ihnp4.ucsd.edu!dog.ee.lbl.gov!overload.lbl.gov!agate!uclink2.berkeley.edu![e-mail]
Subject: Schematics for Luxor 1909530, Magnum Microwave c24-3
To: [e-mail]

I'm looking for some documentation on a Luxor receiver (1909350) and
Magnum Microwave downconverter (c24-3) to assist with repair. I've
already contacted Magnum and found out they've shredded all their
schematics, but if anyone has experience of useful information on
these historical pieces I'd appreciate it.
  Thanks in advance,
                   james   ab6yh
/ [e-mail]

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

Date: 1 Jun 1994 11:25:53 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!pipex!sunic!EU.net!sun4nl!fwi.uva.nl![e-mail]
Subject: simple SSB receiving methods
To: [e-mail]

Currently I'm planning to build a receiver, who doesn't.
However, my intension is NOT to use Xtal filters and NOT
to use a large number of OPAMPS to create sharp lowpass
filters. My plan is to use a phasing method instead.
The basic setup is as follows:

                       +-----(*)---[Audio LP]-------+
                       |      |                     |
\|/                    |  [+45 deg shift]   [+45 deg shift]
 |                     |      |                     |
 +---(*)--[70 MHz BP]--+  [70 MHz ocs]            (+/-)--> Audio
      |                |      |                     |
 [70-100 Mhz osc]      | [-45 deg shift]   [+45 deg shift]
                       |      |                     |
                       +-----(*)---[Audio LP]-------+

The 70 MHz BandPass and Audio Lowpass filters will be of a
(passive) LC type (width bandwidth).  My problem then is:

The audio phase shifters of +- 45 degree do have to be precise
and do have to have a bandwidth of 20 kHz or more.
At the moment this seems to be difficult without OPAMPS or a large
number of resistors and capacitors.

Can anyone give me some advice on how to solve the phase shift
problem. Does a simple and inexpensive method exist to phase
shift a wide spectrum of, lets say, 100 kHz by 45 degrees ?

Thanks in advance, Dirk.  e-mail: [e-mail]

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

Date: Wed, 1 Jun 1994 19:23:11 GMT
From: ihnp4.ucsd.edu!agate!howland.reston.ans.net!math.ohio-state.edu!magnus.acs.ohio-state.edu!csn!col.hp.com!srgenprp![e-mail]
Subject: simple SSB receiving methods
To: [e-mail]

Dirk-Jan Agterkamp (I89) ([e-mail]) wrote:
: Currently I'm planning to build a receiver, ...
: My plan is to use a phasing method instead.  ...

: The audio phase shifters of +- 45 degree do have to be precise
: and do have to have a bandwidth of 20 kHz or more.
: At the moment this seems to be difficult without OPAMPS or a large
: number of resistors and capacitors.

: Can anyone give me some advice on how to solve the phase shift
: problem. Does a simple and inexpensive method exist to phase
: shift a wide spectrum of, lets say, 100 kHz by 45 degrees ?

You could use the Weaver ("Third method" of SSB generation).
I believe it is covered in the ARRL Handbook.  Briefly, you
replace the audio phase shift networks with a pair of mixers,
fed with 90-degree-out-of-phase oscillators with a frequency
in the middle of the audio passband.  When you sum the mixer
outputs, you get USB or LSB, depending on whether it's a
+ or - 90 degree phase relationship.  Oh, by the way, the
low-pass audio filters at the mixer inputs have a cut-off
frequency of 1/2 the audio bandwidth (just below the
oscillator freq).

AL N1AL

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

Date: Wed, 1 Jun 1994 18:43:53 GMT
From: ihnp4.ucsd.edu!library.ucla.edu!europa.eng.gtefsd.com!howland.reston.ans.net!newsserver.jvnc.net!panasonic.com!atvl6![e-mail]
Subject: Techno Whizzy DDS
To: [e-mail]

I purchased a Novatech DD3 kit for about $100.  This kit is based around a
32 MHz. Qualcomm chip, and is meant as a sort of demo board.  I modified the
input by placing latches there to create a PC parallel port interface.  I
use this board in my homebrew 80m transceiver with an IF of 4.9152 MHz.  In
this application, several spurs are noticable, for the reasons given by one
of the previous posters.  They are not really objectionable, as they are
at the LSB resolution (2 Hz) and can be easily tuned around.  My present
software is keyboard controlled - I use the up/down keys to give me a
large frequency change, and the left/right keys to give me a small change.
My preference is 1000 and 100 Hz, respectively, but this is also programmable.

A second set of latches contains the transmit frequency, which is switched on
when I depress my key.  The software automatically updates this transmit
register whenever I change frequency in the receiver so that the correct offset
is maintained.  As was correctly stated previously, the deficiencies of the
DDS as a receiver LO are not noted in my transmitter, due to filtering and
the fact that I am using a class C amplifier on the output.  My lab's spectrum
analyzer shows that all harmonics are at least 45 dB down from the carrier,
even with the DDS being used as a "direct drive".

Some noise reduction on the Novatech board will allow better performance.
For example, the clock driver design allows a fair amount of 32 MHz to come
out the back door (verified with a spectrum analyzer).  I modified this
circuit and replaced the rather cheap PCB trace with coax to help reduce this.
Also, to save money they use an 8-bit DAC, even though the Qualcomm output is
10-bits.  I'm in the process of replacing this one as the quantization noise
is very high with only 8 bits.

Overall, quite interesting to play with, and certainly more stable than any
analog LO that I have built.  It also makes a good direct drive CW transmitter
source.  Future work here will involve a nice, user friendly GUI for the PC...

John
KA5WTO

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

Date: 1 Jun 1994 05:53:09 GMT
From: ihnp4.ucsd.edu!agate!usenet.ins.cwru.edu!eff!news.kei.com!hookup!news2.sprintlink.net!news.sprintlink.net!indirect.com![e-mail]
To: [e-mail]

References <2sd787$[e-mail]>, <2se6pi$[e-mail]>, <2sfmnc$[e-mail]>t
Subject : Re: Techno Whizzy DDS

Jeff Jones ([e-mail]) wrote:
: I really hope that you don't keep this all to yourself! 8-)  I have wanted to
: do one of those for quite a while. What has your costs been so far? How much
: is the Qualcomm DDS and where did you get it? Thanks for any info you can
: give me!

I got the Qualcomm Q2334 dual dds from Cain Technology, [phone]
FAX [phone].  It comes in 3 speeds - 20 ksps $69 in onesies -
30 ksps for $79 and 50 ksps for $209.

I am using two TRW TDC1012 12 bit 20 msps DACs for the two outputs.
(Can we spell quadrature spread spectrum? :>)  I can not remember what I
paid for them but they were not real cheap.  Invest in a PC proto board, if
that is the route you want to build around, that has the interface
electronics built into the board.  It sure simplifies life.  They run about
$70 for a 16 bit board.

My crystal is an Anderson Electronics model 601 20 MHz.  Their number is
[phone].

Hope you find the parts you need!  The Qualcomm literature has most of the
info you need for building a spread spectrum setup.

Pat

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

End of Ham-Homebrew Digest V94 #148
******************************