SolderSmoke Podcast #177 is available:
13 June 2015
-- PETE JULIANO INDUCTED INTO THE QRP HALL OF FAME
-- Bench Reports: Bicoastal Bilateral Success: A Tale of Two Tias
Only 3 TIA rigs in the world? It depends...
Relay improvements in the BITX Builds
Straightening out amp problems
The many uses of copper foil
No phase noise or bleed-over troubles
Plug-in filters
Adjusting TIA amp gain on RX and TX (too much is not good!)
Getting the BITX to work with the CCI amp
Allison wisely prescribes 3 db pads
Curing hum by moving the power supply (duh!)
-- Farhan's New Minima -- Crying out for an Si5351?
-- Mike KL7R's Web Site is Back (thanks to W8NSA)
-- SolderLex: Rigs or Radios? We go with Rigs
-- A ham rite of passage: Build a Dipole!
-- What does your shack look like at the end of a project?
-- MAILBAG
The CORRECT pronunciation of Belthorn
Multiplication and Division by 4
W8NSA, Vietnam, a Transoceanic and a 9V Battery
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20
The pile of rigs that didn't work... was always small because
ReplyDeleteI'd work to make them work. The result is everything in the
didn't work pile was so chronically bad to be labeled as failed in every way.
Packaging... I start with one of two things, the box, or an idea. Usually the idea leads to a box then a build. Result
was a radio that was built up one side and down the other
to fit the available space. But when it comes to heat (finals)
is space and heatsinks are a must.
MMICS, not all are termination insensitive. As me how I know. People have used them to build rigs and parts of rigs.
Resistance is futile. Except when its constructive. ;)
TIA, and impedance matching... There might be a story there. In one case the amplifier will present impedances
that are known to facilitate designing for coupling. The other
case the impedance is unknown or divergent but we still need to match or as we all know we waste power or worse
suffer instability.
The digi-tia and other bands...any shoudl be possible but
in general avoid bands that are not twice the filter frequency.
The other is keep the operating filter at about no mor ethan 10x the filter frequency and if simple bandpass or low pass are to be used stay at 5x so a heath 3395khz filter is used
that means about 15-18mhz. You can go higher but the band pass filters need to be better. Why? Image responses. You want the IF-LO and IF+LO to be easily filtered and avoid frequencies where known strong signals might occur like the 41 and 49M SW band.
Phase noise. Its the random change in frequency (FM)
that occurs. If you divide a signal by N the phase noise will
reduce by the 10log(N)dB. The classic proof of this is the HP8640 signal generator which is know for low phase
noise.
The Si5351, its phase noise is greater than Si570 BUT its not near horrible as the si570 is very good to start with. The problem of comparing to a near golden standard. If I were building a seriously high performance radio the 5351 is not a consideration then again maybe even the si570. However compared to the average commercial radio the 5351 is still good. The cross talk is a layout problem and with care can be down at the good enough level.
Building a dipole. One must as its a standard. Everything else will be better or worse so having a standard is an important starting point. Open wire line, the old ones understood signal loss and material cost.
One thing about radio, its all about the antenna.
FYI: my shack is a total disaster area. I do clear out waste and useless bits like solder splashes and all but its still chaos. I'm convinced a clean bench is a sign of far from enough projects.
Have a good one.
Allison
The Heathkit DX-100 used 1625 tubes for the modulator and not 811A tubes.
ReplyDeleteLee, w0vt