[Fourlanders] EME contest

Sun Nov 4 17:34:30 EST 2018

Hats off to all of you guys for working the contest.
I was out of the country in Terroristan working on a military EMI problem.

HDMI has harmonics smack dab in the 70cm band.
And, one of the LTE bands.
I've had numerous EMI contracts to solve HDMI problems.
In a nutshell, the problem is almost always the quality of the cable.
Not price, just quality, in terms of proper shielding and bonding of the
shield to the connector shell.
If the shield has a pigtail, you can bet it will be a high impedance node
that will produce common-mode radiation like a som-beach.  And a ferrite
clamp will not suppress CM radiation!

But unless you dissect and X-Ray the cables (I've done so on dozens) you
can't predict the performance.
In my practice, I order 10 or 15 different cables (Monoprice is a great
source) and swap cables until the spectrum analyzer shows a reduction in
amplitude of the offending frequencies.

I've found that one-meter HDMI cables in the $6-17 dollar range have wildly
different response to the HDMI edge rates also.  But as you might guess, a
little capacitance and rounding of the edges is tolerated by the drivers
and receivers and the video quality is never affected.
But that capacitance and slight slowing of edge rates, combined with
low-impedance shield termination can have a dramatic effect on radiated
emissions from the cables.

73
Tom
W4SDR

On Sun, Nov 4, 2018 at 2:11 PM Bob Lear <w4zst at windstream.net> wrote:

> We have done the first weekend of the ARRL EME contest for 6m through
> 1296.  This was October 27th and 28th.  For the first time, we've had
> three stations on the air:  2m, 222 and 432.  Johnny's station was up on
> 2m and using his call K4SQC, made 33 QSO's. Brian's 222 station was on
> and he made his first 222 EME QSO during the contest.  Unfortunately, he
> and the other station were the only two stations active on 222 for the
> weekend.  My W4ZST 432 station was on and I made 21 QSO's.  In all
> cases, we did better for the weekend on all the bands than any other
> contest weekend that we have been on.   The other highlight is that we
> didn't have any major equipment problems.  That's got to be a first for
> a contest here. We even had good tracking with computer control which
> was very helpful since it was completely overcast on Friday night, but
> since we could hear signals, we knew we were on target.  It's the first
> time I had set antennas up without Johnny's help and I also set up the
> 222 and 432 stations.  I built a new relay box for 432 because I had
> relegated the first one I built to Brian's station back in June for the
> VHF contest.  Johnny did suffer from some digital interference from the
> HDMI TV/monitor on 2m but we think we have identified and solved that.
> He did have high SWR on vertical polarization Friday night and Saturday
> afternoon we checked the feed lines and found water in both ends of the
> 2m vertical drop.  Dried them out and solved that problem.  We had had 2
> inches of rain on Thursday and Friday before the contest started.  This
> is the first time we've had water in the coax connectors and will be
> more aware of that in the future if we see any changes in our SWR that
> causes the amplifier to automatically shut down.  Can't have that!
>
> Ron WW8RR also was with us on Friday night for moral support.  We were
> operating single operator stations under the rules.  It helped to have
> someone else around to help keep us awake.  It was a long night and if
> you aren't busy enough on the radio, it's pretty easy to nod off!!  Our
> eyes were pretty bleary in the wee hours.  The moon was up for us from 8
> PM on Friday night until 10 on Saturday morning.  We slept the rest of
> the day, had supper and started over on Saturday night from moonrise at
> 8:30 until almost 11 on Sunday. Not as many Q's on the second night.  We
> can only work any station one time for the four nights total of the
> contest.  We hope there will be some more new ones to work on the second
> weekend at the end of this month.
>
> It took some time and extra sleep on Sunday and Monday for me to
> recover.  I'm sure the others did too.
>
> Johnny's 2m station consists of a nice Windows 7 computer, a Flex 1500
> SDR radio (operating on 10m QRP), driving a DownEastMicrowave 2m
> transverter which drives an M-squared 2M-1K2 amp running about 800W out
> on WSJT.  He is also running an M2 preamp and relay/sequencer box.  The
> antennas are a pair of M2 two meter cross-polarized antennas on an Az-El
> rotator with 20 elements on each polarity.  These antennas play very
> well off the moon.  He runs Power SDR software to control the 1500,
> MoonSked to control the rotator and WSJT V10 to copy and send the
> digital signals.
>
> Brian's 222 station uses one of the Fourlanders W7 computers, a Yaesu
> FT-1000MP (also QRP 10m out), driving a DEMI 222 transverter which
> drives his Lunar Link Amplifier putting out about 750 watts for the
> contest.  I built the relay/polarity control box which has a DEMI preamp
> in it.  His antennas are a pair of M2 30 element X-pol antennas.
> MoonSked and WSJT10 again.  These antennas were used for the regular VHF
> contest in June and will remain set up for the January VHF contest.  We
> are hoping that there will be a scheduled 222 EME activity weekend
> sometime later this year that may get some more folks on for that band.
> Many stations do also have 222 capability but not all can easily change
> their feedpoints during a contest.  Most share more of their station
> equipment than we do with our completely separate stations.  They tend
> to stay on the bands with the most activity.
>
> My 432 station was previously identical to Brian's with the exception
> that all the transverter and amp were for 432.  I  had used that station
> for the past three years for the EME contests That's the only times I
> have done 432 EME.  I did however this time change over to a Flex 1500
> for the radio and was quite pleased with the SDR and it's panadaptor.
> Same software setup as Johnny's station and I built another relay box
> for this contest.  I ran my Lunar Link amp at only 500W out.  I was
> using a pair of K1FO 25 element yagis with Vertical Polarization only.
> I do plan to make them into X-pol antennas sometime.  That should help
> my RX since I would be able to hear someone with the other polarity
> better.  But I have so far done best with V-pol.  My set up of four
> antennas with left and right polarization last year did not work well.
> In principle it should have but it turns out the antennas were not well
> matched.  It shouldn't have mattered that they were in an "X"
> configuration rather than a "+" configuration, but it just didn't work
> well.  Real, single boom cross pole will be better, regardless of x or +
> set up.
>
> We are also discussing changing back over to WSJT-x version.  We started
> to do this early this year and ran into some problems as it was quite
> new then.  The WSJT JT65B mode that we use for EME on the VHF bands is
> the same in both versions.  Go Figure!  The x-version has the new FT8
> and MSK144 modes that we use for terrestrial contacts and contesting but
> the EME modes are supposedly the same in both versions.  That's not what
> we and some others are experiencing.  Some folks are running both JT10
> and JT-x simultaneously to see which decodes better.  Johnny is going to
> try to get that set up for the second half of the contest this month.
> His computer is capable of running all those programs simultaneously.
>
> I fixed breakfasts both days, pancakes and sausage on Saturday and
> scrambled eggs, sausage and English Muffins on Sunday.  We ate at
> Hickory Prime BBQ on Friday night and the new 19 North steak and seafood
> place on the square on Saturday night.  Snacks and Junk Food overnight
> and plenty of coffee.
>
> Looking forward to the second weekend of the contest on November 24th
> and 25th.  If we have time and things go right, we are going to also try
> to have a 1296 EME station set up for the contest.  We've got the stuff,
> just need to make the time and get it all put together.  Good thing I
> don't have anything to do around here!
>
> 73, Bob
>
>
>
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