[Milsurplus] trany to tube transplant

[Hue Miller]

> Sensitivity is the easiest thing to get when doing a solid state > "conversion". You have *way* more gain to work with using FET's than > with tubes. The problems come with the more difficult to measure > stuff like selectivity and overload immunity. Anybody who has bought > a cheap SWL radio knows exactly what to expect .....> > Bob
MOSFETs certainly have higher input and output impedances than 
bipolar transistors and are similar in a way to tetrode vacuum tubes.
Maybe better - there will NEVER be any grid current in a MOSFET.
 
If you look at the schematic for a cheapo 10-bands for $19.95 radio
you'll see that they use ONE chip most often, and some outboard parts
like coils hung on it. 
I saw one recently in an ad for some vitamins supplement, the radio was
free  for the "First 500 Responders" to the advertisement. The description
said that besides for example hearing guerilla communications, you could
hear satellites in deep space. Since they provided a postage-paid envelope,
i took the opportunity to tell them what i thought of their "gift" radio, 
their product, and the quack doctor  who was out to mine the rubes'
wallets. 
 
I think i recall reading that the performance of the 75S receiver with the
Tubesters in, was very similar, with the sensitivity slightly greater than 
before. However, much less drift. Some folks would pine for that good
old-time drift. -Hue
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/milsurplus/attachments/20070831/119d2696/attachment-0001.htm