State of the art -radio

woodelf bfranchuk at jetnet.ab.ca
Sat Sep 24 01:25:05 CDT 2005


Allison wrote:

> Then you'd like the 5 tube 75/80m RX I've built. Or maybe the 6m SSB
> transceiver using analog phasing techniques.
I guess I might.

> 
> However..
> 
> Thermionic diodes are noisy, much more so than silicon.  Tubes at RF
> cannot approach the noise figured that cheap transistors can.  
My mistake here, I was thinking DC offset rather than noise.

Though
> a 3CX1000 amp is still cheaper than a transistor one and far more
> tolerent of mishandling.
That is quite true.

> Crystal sets could not eliminate WGSM (740am) 3000W and 1 mile
> away and allow me to hear WABC 770khz 40 miles away.  

Well add another Crystal -- Filter that is -- :)
I agree that DSP is great for brick wall filters but you might want
to check up on Crystal Sets on the internet because I read a
few people saying that the design of the radios in the past
are based on incorrect theory.

> Non-linearity it's bad design for some things but useful where 
> efficientcy counts.  Look at Class E trannsmitters and switchmode 
> power supplies for efficientcy.

That is only because you need a sine wave out of the transmiter
something that is easy to restore with a tuned circuit. You had better
not look at what I consider a state of the art HI-Fi amp to be, the
one I built from plans I found on the web. A whole 1.25? watts RMS
per channel. I consider it state of the art because 1) It has a
regulated power supply ( Zener diode - 800 volt 6.5 amp  FET pass
tranistor ) 2) Single ended ultra-linear ( 50%) operation.
A 6SL7 driver and 6V6GT for the power amp.


> I have a tranceiver for 6M/2M that uses IF dsp and it's frontend is
> very sophisticated and hears as good as any.  To beat that took me
> a year using some very good analog technology and it's limited to
> 6M and needs a digital display for the analog VFO.  Great radio BUT,
> not significantly better than the commercial one save for a few narrow
> things I only care about.
> 
> What you should check out is Softrock, uses the soundard and CPU
> to do the back end stuff and it's frontend is a 29$ kit.
> 
> www.amqrp.org/kits/softrock40/index.html  (it's sold out but the 
> details are there).
>

But is it open source? I don't like CLOSED equipment or ideas.

> So whats this got to do with computers.  Well as cpu cycles get cheaper,
> DSP can do things that analog had to do but not as well.  Things like 
> brick wall filters that don't ring and phase delays that are frequency 
> invarient are very hard to do with analog.  Right now a sound card
> and a leftover 30-400mhz PC is a pretty cheap way to do dsp but, 
> there are chips out there that coming in cheaper and only require 
> programming. The difference is the computer can also deliver the 
> user interface or as pilots call them the "glass cockpit" rather than
> a box of knobs and dials.

Some day I might want to break the glass and look inside.
Still if you have the PC it a good use for it, since it
too new to be a classic computer. :)
> 
> Allison

PS. I consider state of the art for personal computers
to a GOOD 6809 OS/9 system but not a with a COCO.







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