This is a "stacked" antenna array. A short lesson in antenna arrays follows:
It consists of 4 separate antennas, each with 7 elements (the short horizontal things), mounted specific distances apart, and fed with power dividers and very carefully cut and assembled lengths of coaxial cable. An old "Rule of Thumb" for Yagi antennas is that doubling the number of elements gives you a 3dB increase in antenna gain. 3dB equates to a doubling of the "Effective Radiated Power". Since a 7 element antenna like this has roughly 10dBd of gain on it's own, doubling to two antennas gives you 13dBd gain, and doubling the two antennas to four antennas gets you 3 more dBd, for a total 16dBd of gain compared to a Dipole like I'm using. 16dB is a factor of 40, so if he were running 1000 Watts of power, the antenna would focus it by a factor of 40, making it act like he was running 40,000 Watts to a dipole like mine.
My dipole would probably disappear in a cloud of smoke if I ran 40kW to it! The coax would probably pop like a fuse.....
This array belongs to the fellow up North of me on I-25, the first Ham antenna I saw in Colorado on our first trip out here. An antenna system like this is what a "Super Station" would run. They get extremely large at "Shortwave" frequencies, but on 6 Meters, where the elements are only 5' long on each side, you can build some pretty outrageous antennas.
Anyway.....As I was listening to the SSB frequencies, I would also flip over to the "Digital" frequencies every 30 minutes or so to see what was happening. Where I could barely make out the voice contacts, my monitoring software showed the band was alive with signals.
Here's my "Control Panel" for the WSJTX/FT8 software:
The leftside box shows the activity on the band, and the rightside box is a real-time spectrum/waterfall display.
The vertical stripes in the right box are stations transmitting, and this display shows at least 10 that I can see. And this is at 10PM local time, on six meters. This is the result of the "Sporadic E" propagation mode, something I won't go into here.
I still feel a bit "remote" using the WSJTX/FT8 software, but geesh...you sure can rack up the contacts with it.
I've made over 70 contacts today, and I haven't looked at the how many "Grid Squares" or states I've contacted.
Update.....
This is what a "dead" band (no propagation) looks like. The two strong signals (the patches of red) you can see are local guys. Otherwise, ain't nobody coming in.....
Sunday Update.....
The band was completely dead (NO stripes on the right hand box) until about 45 minutes ago.
Now it's wide-open, and blazin' hot.....
.JPG)
That's pretty amazing with the new digital modes. I'm with you and am old school, preferring to do it the old weak signal way with SSB and CW. Congrats on getting on six meters again.
ReplyDeleteYep, you can decode things you can't hear, and can barely see on the waterfall.
ReplyDeleteBut yow, is it ever DEAD today. Maybe things will pick up later.
From my limited experience with this, they signals on the digital waterfall display have to be quite strong before you can make contacts on SSB, so you can make contacts on a fairly "dead" band, and then when the signals are wall-to-wall on the digital frequencies you can switch to SSB and make contacts the Olde Skool way!
drjim, have you ever considered using a magnetic loop? from my understanding, the null on either side of the loop would block a lot of the noise and interference from the sides and boost reception without going all “antenna farm(ish)” with that stacked array like your nearby ham person did with his array.
ReplyDeleteMag Loops are used more on HF than 6 Meters, which is VHF. Their primary advantage is that they pack a big bang for the amount of space they take up. A VHF-sized one would be rather small and might be harder to build, but I've never looked into using one.
DeleteMy dipole also has a null off the ends that I could probably use to "Put A Null On The Noise", but I'm limited in where I can site it in our lot.
If I made a "rigid" dipole from tubing it would be easier to rotate, same as a mag loop, but then I'd need another support structure, and some way to be able to rotate it 180*.
The guy with the stacked array lives on 7 or 8 acres, and has three other towers. I just grabbed the picture from his QRZ website.
I worked him the other day with FT8, but have yet to meet him.
After my talking up the VHF contest this weekend, it has been mostly lame around here. In the couple of hours before the contest, I worked six western European countries, and while I usually get reciprocal signal levels out of FT8 that are higher than or equal to the numbers I receive the other guy, this time I got reports quite a bit lower. I suspect some of them had antennas like your local big gun.
ReplyDeleteAs the day wore on, it quickly died down to only Florida grids coming in. Today, it wasn't Europe but Canada - especially VE2 and 3. Some New England. A few minutes ago, it was all Florida grids coming in and fewer than yesterday.
We still have a few hours to listen.
The band was open and shut at least twice that I saw. The waterfall would be full of signals, then they'd all fade out in a 20 minute period.
DeleteThe last screenshot was taken a couple of hours before the contest ended, and the band was wide open.
Looks like a busy set of channels there! :-)
ReplyDeleteYeah, it got pretty crowded the last 4 hours or so. The band was still open after the contest, but activity dropped to about nothing.
DeleteYour last few hours were like mine. Sunday afternoon was more dead than Saturday. Saturday I could hear pretty much all of peninsula Florida. Sunday I heard my grid and sometimes the one to the west of us.
ReplyDeleteI left the shack for a couple of hours and went back around 7:30 PM. It was wide open. Originally just the Northeast US grid squares (FN), New England and into Canada. As the evening went on, the opening moved farther west into the EN grids, then the "low number" EN grids, Minnesota then north and south Dakota, finally into DM and DN grids. Not as far as California, but SW Arizona and into Nevada (Western Nevada). I heard like four or five guys in Winnipeg.
I worked a few Canadians, several Kailifornians, a few Mexican stations, and a bunch in the Midwest. I had around 200 contacts total. Looking at the map, typical distance was 800~1100 miles, so I think it was "single hop", just like the books say. Some of the Super Stations out here were working JA's, and I think a (very) few contacts into Europe.
ReplyDeleteI could see one side of a QSO where the station I could hear was working somebody who was "two hops" away from me, so there was probably more than just one Es cloud out there.
There's a "Front Range 6 Meters" group on groups.io, and I've "met" a few people there who's antennas I've seen in the area.