Friday, March 09, 2007

Highspeed design

At first glance, it would seem that the Proadlizer's or X2Y caps are worth it. More discussion is on c.a.f, which also points to the SI-list. IDC caps are another choice.

In a semi-related discussion: some have claimed that ISOLA FR408 (Dk of 3.7) rates very close to N4000-13 SI (Dk of 3.5 to 3.7, 0.009 loss @ 10G), but most discussions I've seen seem to indicate it is a noticable step below. It definitely costs less though, so it might be a decent tradeoff. Not that 13SI is ideal: it may have delam problems at RoHS soldering temperatures. PLC621, Matsushita Megtron 5 and IS620 (Dk of 3.5, Df of 0.008 @ 10G) are matches to SI and are also supposedly RoHS compatible. IS415 may be a decent 10G match as well. Also, 4000-12 might be a valid alternative to 4000-13 for Pb-free processes, if I could find the specs for it. Oh, and don't forget about moisture absorption. Lastly, avoid the use of Pure tin plated compoents if possible, otherwise try to source parts with post Sn plate annealing of the suface finish. Other good articles.

IEEE802.3ap Improved FR-4 (Mid Resolution Signal Integrity):
–100Mhz: Dk≤3.60;Df≤.0092
–1Ghz: Dk≤3.60;Df≤.0092
–2Ghz: Dk≤3.50;Df≤.0115
–5Ghz: Dk≤3.50;Df≤.0115
–10Ghz: Dk≤3.50;Df≤.0125
–20Ghz: Dk≤3.40;Df≤.0140

Temperature and Humidity Tolerance (0-55degC, 10-90% non-condensing):
–Df: +/-.001

Resin Tolerance (standard +/-2%):
–Df: +/-.0005

These slides seem to show certain no-Fr4 materials being close to the same price, but considerable improved 10G performance: Nelco 6000, TacPreg, Taconic RF35, and Rogers 4350. I'm sure there are some trade-offs though... yep, the DDI chart shows them to not be quite so good in thermal performance.

  • Td - Thermal decomposition temperature
  • Tg - Glass transition temperature
  • CTE - Coefficient of thermal expansion
  • IST - Internal Stress Test

Monday, March 05, 2007

Algorithm stuff

Reed-Solomon: There is a free implementation available here. Would it be worth implementing a KV (Koetter-Vardy) algorithm (aka soft-decision decoding) to improve RS decoders? Perhaps not. Google gives a surprising number of hits of their name combined with FPGA and Solomon.

Arbiters: Interesting idea for a very simple arbiter.

Level it

I'm on a new quest: to find the highest accuracy laser level I can. I have some top-secret leveling I want to do. How am I going to justify the purchase? Like all good top-secret programs, I'm going to buy it for an altogether different purpose: to install floor tiling. So I want it to do chalk lines as well. Of course, a hugely expensive precision laser level may not stoop so low as to do chalk lines on the ground, but if I can find one, it might be worth it.

Accuracy seems to be spec'ed at 100 feet. Ones costing MANY hundreds of dollars are accurate to 0.125 inches at 100 feet. That accuracy would probably do for me, although honestly I'd kill for 1/16".

Turns out that professionals use the CompuLevel made by Stanley Tools (New Britain, CT). It was designed by Dennis L. Vories, P.E. Of course, it's $1000. A less expensive method would be a water level - either Watrlevel, or just make one myself. They also (very honestly) list all their competitors.

Sunday, March 04, 2007

House / soil movement

Here are the resources worth reading on the topic:
(mostly found through this search on google).

Most recommendations seem to center on around:
  • Sloping soil away from foundation
  • Watering regularly to prevent huge cracks from appearing (which allows for non-standard water flow)
  • Monitor soil moisture (possibly with instruments at multiple locations around foundation?) - aka "soil resistivity" OR "soil moisture measurement"
  • Consider setting up barriers to roots and/or water movement
  • And of course, gutters

Thursday, March 01, 2007

Alternative investments

Before I get started... wikinvest seems kinda neat. Google search also.

China seems to be getting pretty risky despite this or this.

Other good links for ratio guidelines can be found here (Interest Carry Ratio = Net operating incoming / Loan Amt.... 13% great; debt service ratio = Net Operating Incoming / Debt Service... typical requirement in the 1.1 to 1.25 minimum. 1.52 would likely rate a "good investment"; default (break even) ratio = operating expenses + debt service / gross income... a .83 means 17% return on investment; capitalization rate (CAP rate)

  • "Tactical-allocation fund managers favor stocks over bonds"
  • "how to invest in wind farm" (including this)
  • "investment trust wind farm"
  • "invest rv OR motorhome OR "motor home" storage"
  • Off-shore funds
Investment companies or links:
Or do I just stay with just ever-so-slightly non-traditional stuff:
Is there a market inefficiency in the NAV vs. market pricing of closed-end or ETF's? If the YTD, 1-year, or 3-year NAV indicates that the fund is doing well, market pricing should eventually follow. For example, sorting YTD so that the largest loss is listed first, you find plenty of funds with market returns considerably larger than the NAV return. Theory would hold that you buy these and wait for market return to re-converge. This assume the fund doesn't always track with that amount of offset between market and NAV returns. Of course, ETF's may not be "better" in general. Same thing here.

And then there is Wind farm operating companies? (or equipment NEG Micon, Vestas, and Nordex) Search and Search. Operating companies: Canada companies and US companies. General news and company lists and investment site. What about partnerships like Creststreet? Or trusts. Although I guess I'm not ready for an income trust. Never heard of this before. Some way to invest in ESS?

"If you really want wind in your portfolio, you need to go overseas," said Ms. Real de Azua.

Portfolio 21 (PORTX), an SRI mutual fund managed by Portland, Oregon-based Progressive Investment Management, does just that.

"Our approach to the volatility and risk associated with such an immature industry is to identify one or two companies in the sector that we really want to bet on because we feel they are positioned well to be survivors as the industry matures," Progressive Investment Management Chair Carsten Henningsen told

"In wind, it's going to be Vestas (VWSYF.PK) and NEG Micon (NEGMF.PK)," said Mr. Henningsen.

Vestas, the world's largest wind turbine manufacturer, and NEG Micon are both based in Denmark, as is Bonus (BONU.CO).

The German wind market is by far the largest in the world and includes Enercon (ENDC.PK) and Nordex (NRDXF.PK).

Inconsistent wind-energy incentives in the U.S. have made it a challenge for foreign and domestic companies to operate in this country. However, Gamesa (GAM.MC) is expanding beyond its home market in Spain and entering the U.S. market.

Perhaps find a company that took advantage of the U.S. government established wind energy production tax credit (PTC).

Wind farm info:
  • Aggregated news site with seemingly positive and negative slants (one problem with wind: during summer, the wind typically slows down considerably)
Google for competitor OR competition to these companies?
london stock wind power OR generation OR farm
invest in wind

Hedge funds, or funds of funds of hedge funds:
Random investment sites
There's also merger, acquisition, and arbitrage: