[NLRS] PSK31 on 2m SSB

[Gerald]

On Mon, 2005-08-29 at 11:34 -0500, Dan Larson wrote:
> Well, there *are* limitations to what I an attach to my camper!
> 
> First of all, I don't have a clear shot at the sky unless my mast was
> 40ft high to get *over* the tops of the oak trees, the branches of which
> spread above my camper. Not to mention, that there is not enough room
> in my "lot" to bring down guys to stabilize a mast that high. 25Ft is
> the best I can really do without the objections of my "neighbors", the
> campground owner, and my XYL ;-) A 15 element beam would hit the trees
> as it spun around. Terrain-wise, its flat.

You only need ONE direction towards MSP. You don't need to spin the
antenna for that dedicated path.

You are running horizontal polarization on both ends of the path? Cross
polarized costs up to 40 db, and there is some evidence that horizontal
polarization gets beyond the visual horizon better.
> 
> I get lots of questions already about my "TV antenna". At least they don't
> see the HF wire strung through the trees unless they stand right under it!
> 
> I am feeding the 6-element homebrew yagi with RG-8X from the "candy store"
> in Moundsview. Not the greatest stuff, but there's only 30 ft of it to
> my radio. Yeah, sure I can run some LMR400 up there instead, but the XYL 
> won't be happy with the insect life forms exploiting the 1/2 gap in the 
> window, nor the 1/2 inch hole in the side of the camper either ;-) 

You loose at least a couple dB from RG-8X with the 30' run. A
significant amount on a marginal path. Easier than running coax in a
window, get a long coax feed through and mount it in a 5/8" hole
permanently through the trailer wall. Get a cap for the outside when
traveling to keep the connector from filling with water and dirt. Don't
use RS UHF elbows. They sometimes use a coil spring to go around the
corner which introduces a great deal of loss at VHF and up.
> 
> I am using those "Made in U.S.A" silver plated teflon PL259's, and I did 
> fine job soldering. I checked the feedline with my MFJ-269 for shorts or 
> any other problems. I'm pretty picky about that part. I agonized and fretted 
> over my own design using simulation software until I could not stand it any 
> more. I built the darned thing out of 3/8 Al tube from McMaster-Carr. Its a 
> short boom design optimized for FB ratio and fed with a gamma tube. The 
> software predicts a 60 degree "view" angle of -3dB from peak gain. Its about 
> the best I could get on a 6' boom. ( < 1WL) According the the software, it 
> ought to be about 11dB of forward gain, ground and such taken into account. 

11 DB is a lot of gain for 6' and 6 elements. Is that over isotropic
over earth? Did you take into account element length effects of end
effect and boom effect? The optimizer programs never include boom effect
and sometimes are out in space on end effect. The 3/8" elements do a
nice job of increasing bandwidth and allow getting all of the elements
for a 2m beam from 6' lengths of tubing without waste. I used NBS data
to build a cross polarized yagi for my dad to use with Oscar satellites.
It worked well. I don't remember the dimensions.

How do your element lengths compare to the NBS yagis in 80s vintage ARRL
publications? Those yagis are within a half dB or a dB of the optimized
latest designs. If you get back to the NBS report (977 if I recall
correctly) you can see the adjustments needed for boom and end effects.
Many have built using the NBS designs and unless the builder ignored the
changes need for different sizes of booms and elements the gain came out
as claimed. At the same time when the element lengths for an insulated
boom were used with a metal boom the gain was way down.
> 
> The only real obstructions to the signal path are the oak trees & their 
> leaves. The elevation at my "weekend QTH" is about 300ft higher than 
> the other station I am trying to reach in Hastings. (The south part of town
> with a great view of the horizon, not the lower part of town with
> "Hollywood Hill" in the way...)
> 
> What I am *really* want to know is how much PSK31 can help in my less than 
> ideal situation.
> 
> Dan 
> KC0LUY

As others have said, 125 miles should be a reliable path for SSB. Long
ago, as Iowa Army MARS technical coordinator I tried to establish a 2m
SSB net to replace noisy and propagation clobbered 75 meter nets.
Unfortunately I never could convince any MARS members that weren't
already on 2m to get there. But at 100 miles the signals were generally
better than on 75 (at the minimum of a sunspot cycle) during the evening
hours. There were deep fades, probably a couple an hour but the rest of
the time signals were solid.

During the UHF contest, I worked 200 mile paths on 222 and 432 cross
polarized from a discone here. And there were many complaints in the
soap box about the poor conditions that weekend.

Bring your yagi to the next CSVHF or Aurora conference and see if the
computed gain matches the real world gain at the antenna measuring. Many
home built and commercial antennas have missed the claimed gains by
large amounts. Yet some do well. See how your's does. I know its been a
sobering experience to see how far theory is from real world works
sometimes. Yet some antenna makers haven't bothered to change either
their designs or their inflated gain claims despite low results at CSVHF
conferences.

-- 
73, Jerry, K0CQ
Dr. Gerald N. Johnson, electrical engineer
All content copyright, Dr. Gerald N. Johnson