I am not in the business of selling it to hams (commercial only) but here are the prices we pay for it;

Cable LMR-400 Standard Outdoor Cable Per Foot  : 0.83
Cable LMR-400 Ultraflex Per Foot : 1.00
Cable LMR-400 DB Watertight Per Foot : 0.90

You should be able to find something comparable from suppliers. It looks like the $0.83 price is very similar to what you can get from a distributor of amateur radio feedline. I would think that UltraFlex or Watertight (gel flooded, direct burial rated) should be along the same lines.

As you can imagine we would mark it up and usually sell thousands of feet on spools. Freight is a killer.

Interesting question. The question "depends" on a few things;

You can vertically space, vertically polarized antennas as they will be in the "null" of the other antenna. Some rules of thumb vary from 1/4 to 3 wavelengths of spacing to minimize desense and overload.

For example, at 900 MHz we space vertically polarized antennas at least 6' apart (vertically). Horizontal spacing on vertically polarized antennas is much much further as omni antennas would be in the radiation pattern of the other antenna.

Conversely horizontally polarized antennas should be separated horizontally and the same 1/4 to 3 wavelength rule of thumb applies. Vertically stacking horizontally polarized antennas... the spacing should be much further.

This is for antennas operating in the same band. If you are on 20m on one antenna and 30m on another then the rules can change.

Just remember that placing any mass of metal in close proximity to another antenna is going to change the radiation pattern of both antennas. You may change the take-off angle, gain, directivity, front/back ratios. Imagine if you are 80' up in the air with stacked antennas. Will the top antenna see the earth as the ground plane or will it see the other beam that is 15' below it? What happens to the lower antenna? Will it see the upper antenna as some sort of ground plane or a capacity hat?

The possibilities could give anyone who models antennas in NEC and then decides to model "structures" or unintentional arrays the sweaty shakes at night.

Antenna gain also benefits your ability to receive signals as well. Look at some of the antenna radiation profiles to make sure that the gain is at a takeoff angle that is beneficial to your desired operation. A cloud burner with positive gain straight up in the air would not help you with DX work but you would be the big stick for a few hundred miles around.

It is weird for me to say "positive gain" but there are lots of antennas (compromise designs) that are very negative in their gain (losses?).

I have seen problems on commercial VHF/UHF systems where a customer wants to increase their coverage area so they replace the 3 dB omni with a 9 dB omni up on a tower. Suddenly they have dead spots all over the place as the new antenna does not have good "null fill" characteristics or downtilt.

With antenna gain, just realize that it too is a compromise, you do not get something for free. An antenna will get gain by changing the antenna pattern to a smaller main lobe (in elevation and/or beamwidth).

On a metal can electrolytic capacitor that should be at ground potential. If they are being used for simple power supply applications they all are probably attached to the ground rail.

When you use a bunch of caps in series (like on a high voltage power supply) the cases can be at different potentials.

I would look at the traces or get an ohmmeter and check. I bet the cases are all connected to the - pin and that goes right to ground.

Are we talking about the rosin paste or the solder/rosin mix that is sold in syringes or tiny, thumb sized containers?

Regular old-fashioned rosin (like in a shoe polish tin) seems to last forever.

the solder/rosin mixture (a gray substance) does seem to become unworkable after a few years. I think it is a problem where the solvent carrier eventually dries out.

We used to take the liquid rosin (sold in bottles) and add in a bit of solvent so it would flow better. Each workstation had a tiny squeeze bottle with a dull needle tip. We used that when clipping out old components so you could use the iron tip to just flick the component leads right out of the circuit board.

Even that Kester stuff would solidify in a few months. and get white solids in the bottom of the bottle.

Barring conditions like sub or super-refraction VHF and up frequencies are usually limited to the radio horizon between two antennas. That is a function of the height of the antennas. There is a handy calculator at http://www.qsl.net/w4sat/horizon.htm

Other factors are;

Terrain
Vegetation losses (attenuation based on vegetation type)
Fresnel zone losses/obstructions
Free Space Loss (function of distance)
Reflection and refraction of signal (this may be beneficial or harmful)
Refraction may be modeled with a 2/3, 1 or 3/4 Earth and is usually connected to atmospheric effects
To a lesser extent, temperature and precipitation (unless you are in the microwave band
Polarization

You may get much greater range than a simple calculation for radio horizon, you may also get something significantly less. Usually for EMCOMM type work you want to have the most reliable link possible so you try to be reasonable in factoring in the worst case (but not being ridiculous)

That is why it is best to tighten them with a pair of pliers until they make a squeaking noise. 

This is on par with what it cost to have a 75' Class II pole set this last summer on a project I was working on (~$1000 materials, ~$3500 install crew and equipment). The labor was only to auger a hole 10' deep (4' + 10% of pole height) and set it in place and to backfill and tamp down. We had to do all of the antenna and feedline attachment before the pole was slinged and raised to height.

There is a 9 dB 900 MHz omni attached to a 10' long 2" aluminum mast that is attached to the pole with three standoff kits. LDF4-50A Heliax, lightning rod, #6 AWG ground wire, 25' of #6 at the base of the pole in a butt-wrap and three 10' ground rods with #6 back to the base of the pole. It took four people to prep the pole (working hard and fast) while a different crew bored the hole and set it.

It is a wonderful looking installation. Here are some photographs;

http://www.picpaste.com/8cc9e8caa17eca210acc3728e6eef0eb.jpg
http://www.picpaste.com/ce7c7d9e7678894e7aee9dd2d2af1d93.jpg
http://www.picpaste.com/1408f1cb66c61e87eb9a409cea49f7bd.jpg
http://www.picpaste.com/9d233c205a6550f7f2f49c7176fe18fd.jpg
http://www.picpaste.com/ddceead546f534a32cace54a531793c8.jpg
http://www.picpaste.com/564de72e17bd73ed79eed7ba770c7fe8.jpg
http://www.picpaste.com/6fa3c7cc2a157421d61521b505a05d6b.jpg
http://www.picpaste.com/e70d22bb4c7e713544c1de75881c79f3.jpg
http://www.picpaste.com/2b3946764003ba18bd302b8704f44980.jpg  (notice how the three ground rods are 120 degrees around the pole, separated by the length of each ground rod)
http://www.picpaste.com/4733dd1acb0532ce7d9575f65a26a3a1.jpg (innovative use of an air hammer to drive those 10' ground rods)
http://www.picpaste.com/4f9401d67d11e5b8656b4fcab295e95e.jpg (bonding ground rods to base of pole, installing test wells over each rod end)
http://www.picpaste.com/b016d194854d23666024a55c60a537cc.jpg
http://www.picpaste.com/47645adfb1315d681eee0616471399bf.jpg (electrical service weatherhead to bring Heliax into building in conduit)

We had 4 electrical contractors to do the antenna prep work and 6 people to set the pole (must of been a slow day at their office or something). We started working at 9 am and were finished by 2 pm. There was allot going on at once but it was a very professionally installed setup. Amateurs could do the pole prep-work if it is delivered a few days in advance and the install crew could of probably been 2 people for setting the pole. The grounding and bonding could of been done later by amateurs.

I would discuss what to do with the equipment with your Elmer. To turn around and sell something that your Elmer gave you as part of a learning experience so you can buy the latest appliance sort of works against their intention in giving it to you.

If I was your Elmer and gave you something to help you improve your skills (becoming an extra is just incidental to that) and you sold it without talking with me it might put a strain on our friendship. They may feel that they could of sold it too and done something else with the money. The gifts they gave you had some sort of meaning to that amateur and by you shucking them off to make cash sort of diminishes the meaning.

Then again, do what you like. There is this "convertible currency" mindset to gifts people receive at Christmas, on birthdays or with weddings. If I went through the thought process to pick something out for someone and they just returned it (and asked for the receipt so they can do that) then do not expect me to go out of my way the next time.

Explain to your Elmer that you just do not have the disposable income to overhaul a rig. You may find that they have access to boxes of pieces and parts and it can be a joint experience in restoring a piece of gear.

With UL certification we are also seeing the emergence of "tri national standards" (harmonized standards) with Canada, Mexico and the US creating a single standards. (example, UL 508 transitioning to UL 60947 over the next four years). I have done design work with a company that produced UL 508 control cabinets and while it was sometimes a bit of a pain, most of the compliance can be met with careful attention paid to design. In many ways the compliance with FCC R&R is the same way. It requires good engineering practices, circuit layout, board design, attention to filtering, shielding and grounding.

We readily gripe about consumer grade electronics that creates RF hash that interferes with our ability to receive. It is important to realize that we are under the same obligation, to manufacture products that are well laid out, in compliance with emissions standards and that meets all safety requirements.

How do we know that the power will be illegal in a foreign market? That is entirely dependent upon their laws.

I can see why they could not to continue publishing if people are treating Barnes and Noble like a lending library. A 14 day return is even too generous with books, do you expect to find the binding defective and want a return?

I find it ironic that in the same posting we can be bemoaning the loss of publishers of relevant books and magazines yet we do not want those publishers and authors to earn any profit off of what they sell because we will read it and return it for full credit.

NTC thermistors are not bad for predictable, fairly low currents (1-12 amps), I use them in boat anchor receivers. They need to be sized according to current demands and the voltage drop you can tolerate. They do need space as they are tiny little heaters and if you try to run too much current through them they can get hot to the point of fire starting temperatures.

http://www.ge-mcs.com/download/temperature/920-325C-LR.pdf

If this is the way you want to go, two suppliers are Mouser and Newark. I am certain there are others.

For a transmitter or amp a Step-Start relay with some sort of time delay is a great idea. There is some debate on if you want to use them on filament transformers for power amplifier tubes. I would definitely leave the filament transformer through the step-start on smaller tubes just to minimize the thermal shock to the filaments. (remember there was a product known as light bulb savers that were little disks that you put into incandescent light fixture bases?) All that I would be trying to blunt with Step-Start is the EMF to the transformer, any sort of current peaks on power switches and to ramp up capacitor charging so the rectifier does not go up in smoke.

I am a fan of beverages but you need land to put up a good one. If they are short then they are no better than a random length of wire terminated by a 450 ohm resistor and fed with a 9:1 balun. Long means a significant portion of the wavelength, think about that at 80 or 160 meters.

Maybe just a dipole or if you wanted to get crazy a fan dipole.

Another set of choices would be a loop, magnetic loop or even an active antenna.

This is the kind of question that should be in the exam pool. How to calculate amplifier power if you know the incoming AC electrical service requirements, plate voltage/current, filament voltage/current, efficiency or RF power output. You can also apply this to solid state devices. It could be worked backwards to figure out efficiency as well.

What a way to get across that a licensee understands ohms law and efficiency.

Manufacturers have been using poetic license with specifications for decades. They get away with it because many of us are too ignorant to hold their feet to the fire. The much vaunted ARRL is in bed with the manufacturers because they are the advertisers. Nobody wants to issue a declaration on industry standard measurements, some amateurs might actually read them.