coax stub summary (part 2)
N0bsh at aol.com
N0bsh at aol.com
Sun Sep 25 23:49:13 EDT 1994
Due to limitations with my system I had to do this in two parts.
Mike N0BSH
n0bsh at aol.com
Onward...
-----------------------------------------------------------
RG-142BU which is that fancy, teflon-on-the-outside, the-size-
of-RG58-but-takes-5KW stuff that you find at swapmeets. Using
small coax has it's drawbacks, however, becacause of it's higher
loss. One thing to remember about coax stubs is: The greater the
loss, the sloppier the skirts of the filter, and the shallower the
null as you sweep it. In other words, hardline makes fabulous coax
stub filters, and RG58 makes ones that only work so-so. RG213 or
RG8 (same thing, really) have been found by practical experience
to represent the best all around compromise.
-----------------------------------------------------------
Noise bridge: Start with the coax a little longer than you expect it
to be after you've measured it to a 1/4 wave including the velocity
factor, then you use this noise bridge gizmo and sweep the coax
with your receiver. Where the hiss goes away is where the stub is
cut for. It was one of those technical marvel things where
everyone else in the room dropped their jaws and gasped with
amazement.
-----------------------------------------------------------
We use 2 sets of ICE filters. They are cheap ($30) and work well.
there are some buts:
...1 physical filter per band= a lot of filter switching (we built all
of them in a box)
...everywhere I went, someone always blew up the 20m filter. get a
spare
...200w only.
... we tested them in a lab, they DO filter, but only if the SWR is
good. The higher the swr, the worse the filtering
-----------------------------------------------------------
A comical note. At a multi/multi I know well, they did not follow
my advise and insisted in making their own 2Kw band pass filters.
They tested the filters with the boxes still open and they
performed well. They filled the filters with foam and closed the
boxes. First minutes of the contest: everyone blew the filters up:
the foam did not dry!
-----------------------------------------------------------
1) All the stubs I have used are 1/4 wave in length...if you leave
the end open, the other end will appear to be closed. If the end is
closed, the other end will appear open. So for example, to put a
20m null on you 40 antenna, put on a 1/4 wave 20m stub, and leave
the end open. Or you can put a 1/4 wave stub on your 20m antenna,
and leave the end closed. One trick that I have used for open stubs
is to put a small air-variable cap on the end, and make the stub
just slightly shorter than 1/4 wave...then you can set the null
exactly by twiddling the cap while listening to the receiver.
2) Don't use RG58...the better the coax, the deeper nulls you will
get.
3) Doesn't matter...I'm currently using 75 ohm double-shielded RG-
11 that was made for computer networks.
4) Yes, that is what I do...put a T connector on top of the switch. Be
sure to account for the switch changing the length of the stub (use
something like a noise bridge to cut them to length).
5) My current setup...I have 4 1/4 wave stubs on a coax switch to
use with an all-band dipole. The stubs are closed on the end, so I
switch in the one that is 1/4 wave on the band I'm operating on.
There is some improvement, but not that impressive (my antennas
are very close together). We played around with some of the ICE
band filters at FD, and they seemed much more effective. Probably
would also be lighter to take filters than lots of coax stubs on a
dxpedition!
-----------------------------------------------------------
If you wanna really do it right, you need bandpass filters and
stubs!
-----------------------------------------------------------
1) Length is critical. Use a network analyser or other device to
tune the stubs. Stubs are very frequency sensitive... you'll need
one for SSB, and another for CW if you are trying to squeek out
evry last dB.
2) Power was not the problem. RG58/RG8X did not (in my case)
provide nearly the same attenuation per null as the RG8/213 did.
3) Suspect you can use 75 ohm. You will already have a small
impeadence bump when you tap for the stub.
4) Yep. Be careful, for the coax switch adds enough length to the
effective length of the stub to change the null outside your
desired band segment!
5) Good question. All depends if you want to do the filtering
before or after the amps. Amps are known for suprious emmisions.
The stubs will help cure that, Dunstar/ICE won't. If you buy new
RG213 for 160 thru 10, you come out about even with a set of
ICE's.
-----------------------------------------------------------
Thanks again to all for the good info. CU from PJ8Z in CQ WW SSB!
>From Robert Wood <w5robert at blkbox.COM> Mon Sep 26 04:52:36 1994
From: Robert Wood <w5robert at blkbox.COM> (Robert Wood)
Date: Sun, 25 Sep 1994 22:52:36 -0500 (CDT)
Subject: w9gr dsp summary
Message-ID: <9409252252.aa01105 at blkbox.COM>
Hi Robert,
I built the original version of the WG9R DSP on the basis of the QST
article (Sep 92, I think). I liked it well enough that I recently
purchased a commercial version. 'Nuff said?
Harry Herr HL9HH/KJ6YR hherr at emh.osan.af.mil
-------------------
I have the W9GR unit -- a second generation version of the one written up
in QST. I am very pleased with noise
reduction and heterodyne killing features of the unit, and less pleased
with the CW audio passband filtering. In the CW modes there is quite a
bit of ringing, etc. And although the recent issue of QRP Journal has an
article with mods to cure some of the problems, I have not gotten around
to it yet.
[<Alan Kaul, W6RCL>] kaul at netcom.com
--------------------
Robert the W9GR unit is excellent on noise reduction....would put it on
the same level as my DSP-9+. The only short coming I have seen is the
lack of flexibility with selecting bandwidths etc.
73, de K0JPJ ex-W5PVX ...-.- fgilmore at ozarks.sgcl.lib.mo.us
---------------------
HI there Robert....I have a W9GR DSP, built from the kit as
it appeared in the QST.....It is GREAT, but:
It needs several improvements...(the commercially assembled unit
incorporates many of these ideas)
First, independantly selecting each filter, an AGC, CW sidetone, better QSK
recovery, more outputs, headphone jack, better audio...the list goes on...
but I love mine and I was able to work Peter I on 80m cw with no problem!
It made the diff!....Gotta run now, but if you want more technically
related
discussion, let me know...73 steve
-----------------------
I have not compared it side by side with the other high-end DSP units (I
built
one of the semi-kits to save the $), but I would be unlikely to give it
up
without a fight.
Sometimes I think that the audio out sounds really crummy on phone -
distorted
but not too noisy, and I switch the noise filter out to hear the signal
into
the unit and am amazed at how inteligible the filtered signal was
because the
voice turns out to be mostly in the noise and hardly copyable at all!
The big problem
with tune ups changes from earsplitting tones to loss of volume because
the
tuneup still triggers AGC in the radio.
Darrel, KI6VY
darrel at dii.com
------------------------
When I first got it, I was thrilled with it. It works very well on
white
noise, pretty much making 20-10 meters sound like FM when there was no
signal present. The autonotch is very effective too. Havent really
used
the bandpass filters.
After using it for a while, I got tired of the sound of the
audio. The pocessed audio, while using the white noise filter, makes
every signal sound like an aurora/over-the-pole signal, with that
wasy/fluttery sound.
73 Barry
Barry N. Kutner, W2UP Usenet/Internet: barry at w2up.wells.com
------------------------
Yes, I am still making DSP kits. My advertising is entirely "word of
mouth."
their denoiser is not quite as effective as mine. At first I thought my
impressions were due to my own bias, but I heard of a ham club up in
Nova Scotia that did a BLIND test of all the DSPs (except the MFJ,
which
was not available at that time). They played the same tape through all
the DSPs, and everyone voted on which one sounded the best, not knowing
which was which. Well, mine won. And I've heard the same comments from
others. .....But if you work
mainly SSB, I would recommend my own DSP, because I think it is the
best
of the lot at noise reduction.
That's my $0.02!
73 Dave W9GR
-------------------------
I had the opportunity to test one last year against my NIR-10. It was
the assembled version, not the kit.
The noise reduction at first appeared to be dramatic, but upon close
testing it appeared to provide dramatic improvement only on signals
that
were already pretty well above the noise. That is of questionable
importance.
The filters did not sound so hot. FIR (finite impulse response) filters
should not "ring" but the narrow filters did not sound ring-free.
Examination
of the frequency responses on the bench revealed several filters that
did not
show the claimed bandwidth (e.g. the 30Hz "mounbounce" filter was
>100Hz).
Others did not have monotonically rolled-off passbands, but showed
"horns" at
the passband edges: these are definitely NOT FIR and would ring. Looked
like
coding errors to this observer.
I have owned the NIR-10 for a long time (the filters are useless and
cannot be
used simultaneoulsly with the noise reduction) and have had a DSP9+
more
recently. The latter is not the millenium arrived, but is probably the
best of
the three.
I basically thought the W9GR sucked.
NI6T
----------------------------
I have built (and used) the W9GR (kit as in QST) and it worked OK ...
my
son now has it and likes it. I own a TIMEWORKS DSP-9+ which is
certainly
as good in all respects and perhaps a wee bit better (uses a faster
u-processor) that I'm very pleased with.
73! de Ken Kopp/K0PP
K0PP at MCImail.com
-----------------------
Hi, in answer to your query as to how good the w9gr dsp audio filter is
on noise, I would reply, tht its pretty good, in my experience. I've
been using one for about 9 months or so, almost exclusively for cw on
hf. I bought it to help drag out RS10 signals on 10 m, since I have a
noisy downtown qth. The optimized noise reduction certainly helps
considerably
in hearing weak cw on 10 m. One caution i should add is that while it
works
very well on rather random noise, it has little effect on repetitive
sources - so for example an electric motor nearby may hardly be
affected at
all by the noise reduction. I have only used it a little for ssb, but
find
that it is quite effective there also.
......the only problem that I had was some audio
noise (highish frequency digital whine) on the output. This was cured
by
adding a bypass capacitor across the bias resistor on one of the output
op-amps. My only complaint would be that the method of mode-switching
is not very efficient.
73, Dave VE2HJT, G4HJT, david at medcor.mcgill.ca
-------------------------
The DSP kit, as received from W9GR was excellent. The circuit board
of very good quality, well labeled, etc. Don't know if the kit is
still available though.
73! de Ken K0PP
K0PP at MCImail.com
-------------------------
Summary of the comments I received. Some where edited.
-- 73
Robert Wood
WB5CRG
w5robert at blkbox.com (blkbox is NOT blackbox, inc.!)
w5robert at blkbox.com@menudo.uh.edu
>From Kurszewski Chad" <kurszewski_chad at macmail1.csg.mot.com Mon Sep 26 09:43:19 1994
From: Kurszewski Chad" <kurszewski_chad at macmail1.csg.mot.com (Kurszewski Chad)
Date: 26 Sep 1994 08:43:19 U
Subject: WE9V RTTY Score
Message-ID: <199409261343.AA29376 at pobox.mot.com>
Well, considering my first RTTY QSO was just two weeks ago, I feel I did pretty
well in the contest. Can't believe in one weekend I was just short of working
RTTY DXCC (92 worked).
WF1B's RTTY software makes working the RTTY contest almost effortless.
Call Used: WE9V
Station Used: KS9K
Operator: WE9V
Single-Op Unassisted All-Band High Power
Hours of operation: about 36
Qs Qpts St CTY Zn
80 98 112 42 4 5
40 144 225 41 28 15
20 424 1010 41 67 24
15 288 754 24 67 25
10 4 4 3 1 2
_______________________________
958 2105 151 167 71
Score: 818,845
Thanks to Paul, KS9K, for letting me use his station (and keeping me well
fed!).
Chad WE9V
Member: Sultans of Shwing
Loud is Cool....yeah, heh, heh, heh, LOUD IS COOL!
kurszewski_chad at macmaiL1.csg.mot.com
>From Jay Townsend" <jayt at comtch.iea.com Mon Sep 26 16:07:33 1994
From: Jay Townsend" <jayt at comtch.iea.com (Jay Townsend)
Date: Mon, 26 Sep 1994 08:07:33 -0700 (PDT)
Subject: CQWW RTTY High Claimed
Message-ID: <m0qpHeP-0003cFC at comtch.iea.com>
Here's what has come in so far.
1994 CQWW RTTY High Claimed Scores
From 14.088 and 7.088
Single High Power
HH2PK 1,300,578 1,252 Q
VY2SS 1,028,970 1,122 Q
WE9V 800,000 958 Q (KS9K STA)
N9ITX/7 661,000 1054 Q
K2TW 556,000 817 Q
K0RC 432,768 789 Q
NI6T 187,400 382 Q
KK6PD 157,373 438 Q
W6MTJ 180 Q
Single Low Power
AA5AU 580,400 400 Q
TY1PS 380,000 585 Q
KA4RRU 375,560 560 Q
N9BHH 141,000 303 Q
NY2U 87,969
W8AKS/6 14,800 88 Q
Single Assisted
N9CKC 311,000 594 Q
WS7I 65,121 213 Q
Multi-Single High
W9KDX 1,050,000 1142 Q
Single Band
K7WUW 40M 16,401
N2AA 20M 160,000 499 Q
K4HSF 20M 110,000 475 Q
W6/G0ATZ 20M 49,830 238 Q
K8UNP 15M 112,000
---
WS7I jayt at comtch.iea.com
>From Mr. Brett Graham" <bagraham at HK.Super.NET Mon Sep 26 17:00:13 1994
From: Mr. Brett Graham" <bagraham at HK.Super.NET (Mr. Brett Graham)
Date: Tue, 27 Sep 1994 00:00:13 +0800
Subject: CQ WW 2-point Qs
Message-ID: <199409261600.AA14348 at hk.super.net>
I couldn't resist commenting after K4XU's posting. After breaking the CQ WW
CW 10m Asian record in '88 & breaking JA5DQH's formidable record a year or two
later on 15m, all I can say is that unless things are changed, I probably will
never put in a major effort again.
>From here, you have to work your butt off running JAs & struggle something
fierce to bag mults at the peak of the cycle, then watch in the next year or
so as some bloody 4X4 works EU at a pedestrian pace, bagging African mults
like shooting fish in a barrel, making you look like a clueless mouthbreather.
High population 3-point land is a long haul from some parts of Asia. From
other parts it's not. Admittedly it's hard to avoid some form of geographical
advantage - nothing can be perfect. But something isn't right if there's such
a strong skew in continental records as there has been in Asia.
Contrary to Dick's comment, I don't think that juicy Asian activity will
change too much if the 2-point rule is made global. The biggest result of the
NA-to-NA 2-point rule is to increase expedition activity in the Caribbean. If
JAs were 2-pointers from SE Asia, I can't see JAs migrating down here like the
Ws do come October/November. It may make a trip to XX9 more interesting for
me, but I must admit the emphasis would still be on partying with my mates
over there than working you blokes on the bands. Or JAs, no matter how many
points they're worth - I'd rather get plastered on Black Label than by
somebody who could almost throw rocks to 3-point land...
73, VS6BrettGraham aka VR2BG bagraham at hk.super.net
>From Trey Garlough <GARLOUGH at TGV.COM> Mon Sep 26 17:04:00 1994
From: Trey Garlough <GARLOUGH at TGV.COM> (Trey Garlough)
Date: Mon, 26 Sep 1994 09:04:00 -0700 (PDT)
Subject: CT9
Message-ID: <780595440.421999.GARLOUGH at TGV.COM>
> CT9 is getting close to the big October mailing. If you have a particular
> contest, category, radio or anything any special combination, please
> try it before I freeze the code. Pick up a copy off CT-BBS and test
> your favorite configuration. I'll be watching both the BBS and the
> reflectors for feedback. Thanks.
And (obviously) please follow up with your comments directly to Ken,
and *not* to the CQ-Contest mailing list.
--Trey, WN4KKN/6
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