Soil Permittivity under Antennas

There is a lot of speculation about the electrical properties, at RF frequencies, of the soil under antennas.  Thankfully, there's an interesting data set where some probes were buried near one of the antennas at the Owens Valley Radio Observatory Long Wavelength Array (OVRO-LWA).  OVRO-LWA is an array of hundreds of dual polarization fan dipoles that is used as a radio telescope over the 27-85 MHz frequency range.

The probes measure the properties at 50 MHz, and produce data both in terms of the complex permittivity and in the more familiar relative permittivity (Epsilon) and conductivity (sigma, in Siemen/meters). The data were taken over about a 6 month time span including the wet and dry seasons.

As described in the data page, the sensors were buried 4", 14" and 21" deep next to one of the antenna stands. From the page:

 "The test pit was dug down to hardpan, which in this location is 22" below ground level. The strata is clean sand down to ~18". From there, the fraction of a green clay-like material increases with depth, reach hardpan as noted above.

The anticipated depth of the hardpan, based on Andres Rizo's experience at site was 10-20'. The actual depth at any given location will depend on river course wander over millenia and the presence of standing surface water."

Data from https://github.com/ovro-lwa/leda_docs/wiki/Soil-Permittivity-Sensors

The actual sensors https://stevenswater.com/resources/datasheets/HydraProbe%202020_draft3.pdf

And, now, on to the data: Here's all of it on one plot - the top sandy layers have low epsilon and low conductivity. The deep clay layer shows distinct clumps, related to the soil moisture. Spring is the wet season in the Owen's Valley of California (just east of the Sierra Nevada), both from rains, and from snow melt, although I don't think there's any melt-fed streams in the OVRO-LWA area.  This plot is in complex permittivity.  

All of the data
Plotted as real vs imaginary epsilon

21" deep probe

Here's the clay layer plots - first plot is complex permittivity as e' and e''. Second plot is in the more familiar epsilon/sigma terms.  Epsilon = e' + j e''; Sigma = 1/(omega e'' * e0)

  

 

14" deep probe

Moving up to the sand, you can see it varies a bit more, and more abruptly.

4" deep probe

And for the top layer of sand, it varies all over the place as the soil is damp and dries.

Take home

There are significant variations in epsilon with soil moisture content. The clay (21" measurements) is significantly higher conductivity, even during the dry season.

If you're modeling your antenna using a tool like NEC, you should model with several combinations of epsilon and sigma, and make sure you understand the performance differences.  Using the 13/.008 "good soil" may not be very representative of YOUR location. And particularly for verticals, the soil properties in the far field makes a big difference.

Award Winning Focaccia

Samin Nosrat's Ligurian Focaccia - addictive bread that's easy!

Yes, I won a first place at the Ventura County Fair with this. This is about the easiest bread recipe ever - there's no kneading, you use your hands for mixing, and it tastes amazing when it's done. All it takes is time (overnight). The recipe comes from Samin Nosrat's show and book Salt, Fat, Acid, Heat.  There's several versions of the recipe online, and there's also a clip of her Netflix show where she makes it, and a really good episode from Bon Appétit's video series.

Samin's recipe

Wet:

• 600 grams lukewarm water (2 1/2 cups)
• 1/2 tsp active dry yeast (a lot less than a packet)
• 15 grams of honey (about 2 1/2 tsp)

Dry:

• 800 grams AP flour (I'm using King Arthur, but I doubt it's critical for this.  You probably don't want to use bread flour). Weigh it don't measure it by volume, or the dough might be too wet or dry.
• 18 g Kosher salt (2 Tablespoons) (or 1 Tablespoon fine salt)
• 1/4 cup of extra virgin olive oil.

Brine:

• 1 1/2 tsp Kosher salt (5 grams)
• 1/3 cup warm water (80 grams)

Rosemary (optional) and flaky salt for sprinkling just before baking.

1. Mix the wet, and wait for bubbles. Mix the dry. Mix wet and dry to make a gloppy wet dough. 
2. Let rise in an oiled container for 12-14 hours. 
3. Pour dough into a well oiled half sheet pan. Make sure all surfaces are oily. Stretch to the corners with oiled hands and fingers repeatedly over about 30 minutes. 
4. Sprinkle with rosemary, if desired. Dimple the surface, pour on the brine. 
5. Proof for 45 minutes.
6. Sprinkle with large crystal salt (like Maldon). 
7. Bake at 450 with the pan on a pizza stone for 25-30 minutes, until bottom is browned. If top needs more browning, move up in the oven for 5-10 minutes.
8. Pour a few more tablespoons of oil on top and let soak in. 
9. Remove from pan and cool for 15-20 minutes. 
10. Eat it while it's warm.

There's really only one part of the recipe online that's a bit vague, and it has to do with the "cooking on a stone or turn a pan upside down" - If you've got a pizza stone in your oven, put the sheet pan with the bread on top of it (don't try to put the dough on the stone). If not, put another pan upside down when preheating, and put your bread pan on top of it. The important thing is that you need a heat storage to get plenty of heat to the bottom of the dough filled pan so the underside crisps up and browns nicely.

Plenty of Olive Oil

The key to this recipe is "plenty of olive oil" - You're going to need a fair amount beyond the 1/4 cup in the dough.  You need oil to cover your hands when you're mixing the really wet dough.  You need oil to coat the inside of the container the dough rises in. You need oil to pour in the sheet pan before spreading the dough. You need oil on your fingers so the dough doesn't stick to it. You need oil to pour on top of the bread before and after cooking.  Fear not - the bread does not come out like a greasy dough ball. It rises so much that just the crust is crisp and fried tasting.

I have made this with two different kinds of oil, both from Rancho Olivos (in Los Olivos, CA) - their Arbequina and their Italian Blend, and I don't know that there's a significant taste difference after cooking. They're both fairly mild flavored and they have that wonderful grassy smell when you're working with the dough.

Some pictures

Here's some pictures of the first part of the process - the two videos linked above show the essential "put it in the pan and stretch and poke it" part as well as the salt brine. It starts by mixing the dry ingredients (flour and salt), starting the yeast (warm water, honey), then mixing it all together with the oil.  I used a 8 quart Cambro container which works well for both the mixing and the overnight raise.

Dry ingredients

Yeast happily bubbling

The dough is very wet and gloppy.  Your hands work well for mixing. I'm sure people have been doing it with their hands for millenia. Some oil on your hands helps.

 
Ultimately, you're going to want to dump the dough into something else temporarily, then grease up the inside of your container, and dump the dough back in.  Put it somewhere warm (in July and August in Southern California, that's "leave it on the counter") overnight.  The recipe calls for 12-14 hours, so if you start the evening before, do the mixing, let it sit, make breakfast, then finish the proof and bake, it will be done for lunch time.  This rise is way more than doubling in volume, even though there's only 1/2 teaspoon of dry yeast (a packet is 2 1/4 teaspoons).

Starting rise

Finished rise the next morning

Then, you go through the process of oiling up your sheet pan (a raised rim half sheet pan 13x18") dumping in the dough, spreading it out (stretching it to the corners - it will shrink back, stretch it again for about 30 minutes). I sprinkle the chopped rosemary on at this point. Dimple it (see the video, it's not explainable), pour the brine on, then proof for 45 minutes.  Sprinkle on plenty of flaky salt (if you put the salt on earlier, it dissolves in the brine and dough and bake.

The final steps

Rotate the pan half way through (nobody has a perfectly even oven - you can see how mine is distinctly warmer on one of the long sides in the middle. When it looks done on top, pry up a corner to see if it's done on the bottom.  Pull it out, pour on some more oil, let it sit a bit, then turn it out on a cooling rack.







This was pretty easy, and it tastes awfully good, so I decided enter it in the Ventura County Fair in August 2019 - and it won in the Focaccia class.  I baked it early in the morning of the entry day, got it to the fairgrounds still warm, cut the required size piece, and left the rest with the ladies running the entry booth.

Sausage making - Andouille, Spicy Italian

This is a fairly long post, covering the whole process, from cutting up the meat, seasoning it, grinding, stuffing, and then final preparation.

Cutting up the shoulder and fat

The pork shoulder you get at the supermarket tends to be a bit lean - they trim the excess fat off, maybe leaving a thin fat cap (which is always on the hidden tray side).  You can ask them for the shoulder with more fat, but you're going to pay the full price for the fat, which seems a bit silly, but is an expedient solution.  Tell them you're going to be grinding it for sausage. For good sausage, though, you want more than 20% fat, so having a source of fat you can add is a good thing. I have several pounds of nice pork back fat from a CSA in the freezer, and I use that to boost the fat content.

Bone-in pork shoulder is a lot cheaper than boneless. The bone-in was $5/lb, and the boneless is $6 or $7/lb. As it happens, out of this 4.75 lb (76 ounce) roast, the bone was 10 ounces, or about an eighth of the total weight. Your mileage may vary and "retail price" for the meat tends to go in 1 dollar steps. In any case, you need to cut the bone out.  Next to the bone, you'll sometimes find a sort of gloppy soft fat, as well as the sinews that connect the muscle to the bone.  You want to trim those out of your meat - they don't help the sausage, and will gunk up the grinder.

  

After removing the bone, it's time to slice it into appropriate sized chunks. I like chunks about an inch on a side, so I start by slicing the roast into 1" slices, and then cutting up those slices. There's also a picture of some gorgeous back fat which I've cut into roughly 2" cubes and wrapped in wax paper before freezing. It's much like cutting up butter. The whole fat/meat ratio is something you sort of wind up doing by eye. It just looks right.
 



This tray goes in the freezer to chill the meat and fat. That keeps it from melting during the grinding process.

Getting the seasoning together

Up to this point, pretty much all sausage is the same - you want that same ratio of fat/meat.  For this batch, I'm making Andouille, using the recipe from Rulhman's book. I typically want it a bit spicy, but not lava - so when you see the recipe, adjust the cayenne and pepper flakes accordingly.  Andouille uses some pink salt which turns the meat a reddish color as it cures/cooks in the smoker. This andouille recipe has the dry mix plus diced onions.

 

And here we are, with the meat cut up, fat cubes added, and seasoned. Back into the freezer while the grinder gets assembled.

Preparing the grinder

I'm using my trusty Kitchen-Aid grinder, which has two grinding plate sizes. For this, we're doing a single grind through the fine plate.  Other sausages (like breakfast sausage), you might do two grinds, one through a coarse, and then a second through the fine. Or, if you want distinct chunks, the coarse might work for you. Here's all the pieces of the grinder.  The two plates are on the left, and the cross shaped thing is the actual blade that does the cutting.  I throw all the pieces in the freezer while I'm working on the meat, so that they are chilled before grinding.





Put the auger into the housing.


Blade on the end of the auger.


Put the Appropriate plate (fine, in this case) on top of the blade.


And you put the nut on the whole thing and tighten it down.

Now, were ready to grind.  I put the bowl into a bowl of ice cubes to help keep it cold.

And away we grind

You set the mixer to speed 4 (the second click) and start feeding the cold meat into the hopper. I keep a mixture of fat cubes and meat, and just keep it going.

At the end of the grinding process, I run a couple pieces of paper towel into the hopper, and that pushes the last bit of meat out.  Here's a picture of the auger after disassembly, with the paper towel wrapped at the end. 

Here's the blade  and plate - the stuff around the center of the blade is sinew and soft connective tissue.  This is why you want to try and trim it out when you're cubing the meat.


After grinding, it's important to mix the forcemeat thoroughly - this helps develop the internal structure and makes it hang together. The grinding process cuts all the muscle fibers, releasing a variety of substances, and you want things like myoglobin to make the meat stick together. That's also why you need salt.  When it's done, it has a distinct sticky feel and uniform look.  Some sausages don't need quite this much mixing - if you overdo it, you're making an emulsion, like in hot dogs or mortadella.

  

Stuffing

Stuffing the sausage has 3 steps - getting the casing ready & loading the stuffer; then actually stuffing; and finally making links.

Getting the casings ready

The casings come in roughly 10 foot lengths, with a bunch of them in a hank in a plastic bag with lots of salt. They might well be shelf stable at room temperature, there's a lot of salt on them, but I do keep them in the refrigerator.   I separate out 3 strands from the mass (which always seems to get all tangled up, like kite string), and put the remainder away.

 

You soak the casings in water for about 20 minutes, after rinsing the outer salt away. This is really important - the salt has extracted all the water from the casing (and preserving it), but you need to put that water back in, so that they are flexible and elastic again. I fill the casing with water and drain it 3 times to rinse any salt from the inside of the casing.
 

Yes, the casings are made from pig intestines (at least these casings are - you can also get sheep and beef casings which are smaller and larger respectively).  There are "non-animal" casings made of cellulose, and I started with those - they don't work well - they're not as stretchy and strong, and that's really important when you start stuffing them. I've had really good luck with the hog casings - The only time I have them break is if it's damaged, or I accidentally poke a hole in it.  They're roughly the size of your finger and will be about twice that diameter after stuffing. (somewhere I have a picture of the kids making balloon animals with inflated casings).

Preparing the stuffer

I have a nice 10 pound stuffer with a geared crank handle to run the piston down the cylinder. My largest batches are 5 pounds, so it works pretty well.  There's a whole range of spouts you can put on for the various size casings. There are also horizontal stuffers with a sort of lever arm that pushes the forcemeat through - I've not tried one, but acquaintances who have say the vertical stuffer is better and more controllable - gear drive helps.

I started trying to use the stuffer nozzle on the Kitchen Aid - that was horrible - the hopper was very small, and you can't start and stop easily. With this stuffer, you can put the entire batch into the cylinder, and all you have to worry about is cranking the piston down. A motorized stuffer is going to need a foot switch, because you need at least one hand to hold the casing as the forcemeat squirts in, and a second hand is handy. With a hand crank, you crank with one hand, and hold the casing with the other.

You start by putting the casing over the spout - I have a baking sheet with the wet, rinsed casings on it, and then, I start feeding it onto the spout, until it's all loaded.


 

And then it's crank with the right hand, hold the casing in your left. I try to make the coils neat and not kink it. The water on the pan helps things slide around.

 

Making links

"linking" is one of those things that gets easier with practice. I try to make my links about a handwidth long. You grab the filled casing, squish it with a thumb and forefinger on either side, and then sort of twirl the casing to twist the link ends. You wind up basically doing every other link this way, and the twists are opposite on each one. 

I then tie short pieces of string around some of the twists, because I'll need that to hang it in the smoker.

Chilling after smoking

After the sausage comes out of the smoker, you cut the links apart (the twisted part of the casing is all dry and hard now) and dump them into an ice bath to rapidly cool it. I would think that any pathogens inside the sausage are dead (heat and nitrite and salt), but there will still be things on the surface. And you don't want to put hot sausage into a cold refrigerator.

Spicy Italian 

I'm using the recipe from Ruhlman for this, too.  It has paprika in it to give it that distinctive red color, along with toasted coriander and fennel seeds, along with fresh oregano and basil.


 

For the Italian sausages, they're a fresh sausage, not cooked.  After stuffing, I put them in the refrigerator for a few hours so that the surface of the casing dries.  Once the casing is dried off a bit, they're ready for vacuum packing and freezing.