Mike wrote:
...snip...
I built a couple of the push-pull amps in 1996 using the pcb design as in
the article you cited. I used one in Dallas's phasing unit and If I recall
correctly, I setup the other for a loop. I didn't have any problem with
them. I don't have any way to measure any spec's, so I have to go with
Dallas's numbers. I'm inclined to believe what he says, he seems to be very
meticulous and conservative.
As for the hi-mu, these will work at AM broadcast and below, maybe to get
the proper inductance he needed a hi-mu. Note the one turn feedback winding.
The small size fit the 2.5" x 2.5" pcb.
I seem to recall he built a smt board at one time.
Mike
*************************
Mike, and others...
I've been following this thread and took a look at Dallas Lankford's
article. It looks interesting. And although "...he seems to be very
meticulous and conservative," he also boast of the magical 2N5109 preamp as
having an IP2 of +80dBm to +100dBm based on single versus P-P design (top of
page 7). I can absolutely, positively, beyond any reasonable doubt, assert
that this is an absolute impossibility. That's so fantastic I had to
re-read it an actually ponder how big a signal that really is...
1W is +30dBm
1KW is +60dBm
1MW is +90dBm
I can absolutely assert that anything looking like a 'circuit' in the signal
path of 10 MegaWatts of RF will absolutely vaporize in a spectacular blue
flame instantly.
So I don't understand what he's talking about in terms of IP2 or IP3,
because his claims are non-sensical. You certainly cannot measure such
power in the basement of your house. Ignoring all that, the gain figures he
is boasting are typical of many designs. 12dB? Nothing special about 12dB.
And the so-called "Noiseless" amplifier is never actually evaluated for
noise. There seems to be overwhelming details about bias, transformer
construction, and how to lay out the circuit board, but very little in the
form of meaningful measurements.
Figure 7 on page 11 is equally puzzling. A +60dBm "improvement in
intercepts" makes absolutely no sense to me. And putting in a preamp to
bring that up to +100dBm is even more ridiculous. You would need your own
power plant facility to generate enough power to drive such a beast! Even
if he meant +60dB improvement, instead of +60dBm, it's still fantasy. Sure
sounds good though doesn't it?
I'm no RF guy, but I can recognize an article written on April 1 from one
that's not... I'm not saying it doesn't work, and quite possibly work very
well. It's just the measurements are a bit twisted.
Ford-N0FP
ford@cmgate.com
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