Most of the stuff on this guy's youtube channel is worth it.

http://www.youtube.com/watch?v=M-FZP1U2dkM

EEVblog #84 - High Energy Multimeter Destruction
From: EEVblog | May 04, 2010 | 20,037 views

    Let's destroy some multimeters and shoot some metal
    with Doug's high energy 4KV capacitor discharge unit.

Recently a family member was about to drop Sprint because they had no coverage in their new house.

Sprint sent them a femtocell device - it is basically a mini cell site that looks like a wireless router.  It uplinks to Sprint via your internet connection and covers your house with a cell signal.

Perhaps your carrier can provide one?

Frankly I don't understand how these boosters work.

Cellphones are full-duplex with widely separated rx and tx bands which are themselves broad.

Cellsite  ->  Band X  ->  Handset
Cellsite  <-  Band Y  <-  Handset

Do they purportedly receive the entire band X or Y and retransmit it on the same X or Y? .... How is that supposed to work? Wouldn't this thing just hear itself?

The cellsite doesn't have receivers on the X and the handset doesn't on Y... Additionally, the digital protocol tells the radios what channel to use, so you can't really just move the signal without the knowledge of the two ends.

CDMA systems also use precise power control of the transmitter to allow overlapping signals to be separately decoded .... certainly such a "booster" does not participate in the power control loop...

Maybe someone who has used one can enlighten me.

Info I can find at http://www.continentalsatellite.com/ku_and_ka_band_satellite.html says DirectWay / HughesNet uses Ku band downlink at ~12GHz and uplink at ~14GHz.

The included LNB and transmitter are probably not easily convertible to 10GHz.  But the waveguide system, isolator, etc... are potentialy usable by bolting on 10GHz gear.  I doubt the small waveguides would be effective at 2.4GHz.


At a basic level the parabolic dish is usable and effective for many purposes if you can place an appropriate antenna at the focus.  Right now the Ku-band feedhorn would be located at the focus, so you'd have to remove it and place your 2.4GHz feed there (as in http://www.jrmiller.demon.co.uk/products/patch.html).   The "offset-fed" dish will aim pretty high in the sky and will look like it's pointed "at the ground" when it's actually pointed at the horizon... But it will work!

http://people.wallawalla.edu/~rob.frohne/Airport/Primestar/Primestar.html is using an old DSS dish as a 2.4GHz Wifi antenna

http://www.qsl.net/n1bwt/chap5.pdf shows the geometry and explains usage of these dishes.

http://www.w1ghz.org/10g/10g_home.htm 10GHz amateur radio site

Also check out the "FTA" or "Free To Air" satellite forums - there is a large market in custom, hobby, and retrofit satellite gear, as it turns out parts are mostly standarized.  This guy for example mounted several LNBs on his HughesNet dish to receive multiple satellites simultaneously: http://www.abadss.com/forum/29-fta-accessory-talk/104269-hughesnet-lnb-fta-setup.html

KF6QEX: The improvements apply to both sets of forums.  After using stackoverflow, forums like this feel so "90s".... "I can't upvote???" "How much reputation does this poster have?" "I can't comment on this answer?"


And actually, stackoverflow is explicitly not about servers. It's about programming, and very much "what is the best way to go about tackling this abstract problem..."

Both communities are very similar, they have well established and very knowledgeable senior members who participate. They have newbs who just want to learn. They have heels who just want to stir up a ruckus.  The same moderation needs apply to both, and the same recognition

For starting random discussion threads that ramble wildly for 100 pages, maybe it's not the best model.  But to get any kind of technical answers or discussion where valuable and correct input gets recognized, while also building a knowledge base to feed to newbs... it works.   Don't let the content blind you.

There simply might not be propagation between you and the other station.

There can be a path from A to B, and A to U, without a path from B to U.


When you yourself start making contacts - the other station will simply either hear you or not.   If you don't hear them, you aren't making a contact!


And that may change rapidly as the atmosphere changes - just like it can be sunny one moment and shady the next.

Mandatory? haven't heard of that.

As far as CFLs go, I am concerned the things are a disaster ....  I wonder just how much energy is used to manufacture their ballast and housing and mine the phosphors and mercury....  Given their lower energy consumption, how long do I have to burn them before their manufacture is "paid off"?  If they fail after a month of use because they heat up and die (seems like I have had few last beyond 3 months).... then there is additional energy required to recycle them due to toxic content.   And their only supposed benefit is their lower consumption. Where do the lines cross making them a net savings?  Compared to the simple materials in a tungsten bulb I really wonder if it's worth it.

Now LED's on the other hand.... I am ready to buy lots of those.  Rugged, long natural life, easy to drive, high efficiency..

See stackoverflow.com for the current best-of-breed.  It's amazing how awesome this website is.

"Forums" need moderation and metamoderation. (Self-moderation).  Good contributions need to rise to the top. 

Make sure the signalink is set as the output device for DM780.

Make sure the signalink output gain is turned up

Make sure the radio input gain is turned up.

Make sure the radio is in DIG mode (input from data jack) and not USB mode (input from mic jack)

Listen on another radio. If you don't have another SSB radio, you can flip it to PKT mode on e.g. 146.56 and listen on a more common FM radio. The levels will be different than in sideband mode of course.

The telescoping antenna is a good idea.... Easy multiband groundplane!

The hobby shop nearest to me also sells brass and aluminum tubing in 3 foot lengths in small sizes... From K&S Engineering (http://www.ksmetals.com/retail.html  "Tube & Wire Center - Stock Number 4800")

Great for small 2m and 70cm beams assembled on 1 x ½ " wood.  And any typical tubing cutter will quickly cut this with millimeter precision. 


Also, brazing rods. (http://www.amazon.com/gp/bestsellers/hi/2225082011/ref=pd_ts_hi_nav)

I highly suggest 10 AWG.

14 AWG is just too thin to support itself well. It does, but just barely.

I just scavenged line isolation transformers from old 2400 bps modems, and used a 5k pot for level control on the radio input.

Soundcard output directly to transformer, other side having 5k pot across it with the wiper and one side tied to the radio data jack.

Soundcard input directly to transformer, other side directly to radio data jack.

Optoisolator between RTS/DTR and key input - but you can leave this out and use the radio's Digital VOX.


Modems or burnt up PBX/Phone System cards are a good place to find these... and the optoisolators as well.

I have seen it mean everything from 100mv to 2.0v/pk-pk.  Thus the reason for the input gain control.

Usually the "front L/R" output (previously just called the "output" before 6- and 8-channel cards) is a low-impedance output of about 32 ohms to drive headphones.  The remaining channels usually have around a 600 - 1000 ohm output impedance.

Input impedances are on the order of 10k ohms.  Modern audio equipment detects voltage, not power, and the goal is to have the source lightly loaded, so impedance matching is generally unnecessary as the source impedance is way less than the load impedance.  Most people who put a resistor across the input to "match impedances" are really just creating a resistive voltage divider that drops the signal level.

Most sound card outputs are run from a split 5v rail, so they can provide up to about a 2v swing.

It would be interesting to put a DVM on the sound output and drive it with a 60hz sine wave, to see what the DVM measures as the AC voltage. (RMS vs peak-reading is an important distinction here)

Alternatively, putting an o-scope across the input, with a variable-level sine wave source, to see just how many volts pk-pk produces a full-scale digital reading at 100% input gain.  This is what really defines "line level" for your particular sound card input.


Connector type isn't really relevant.  Line level is found in XLR connectors in balanced equipment (+/- 2v across the differential pair), RCA connectors and 3.5mm jacks in unbalanced equipment (1v to ground).

And Mic-level (10-100mv 5k ohm input) is also found on XLR and 3.5mm connectors, and phono-level (10mv 50kohm input with equalization) on RCA jacks.

With my recent experience having the EEPROM trim values in the service menu randomly change, I am wondering if these problems are a result of this corruption.

They might be fine at the factory, then the EEPROM data gets corrupted and they are out of spec for bias or whatever.

Still a problem, even if that's the cause.

I suggest the "LyX" frontend for LaTeX, it allows easy composition and inline inclusion of the fancy LaTeX math.