At 07:56 AM 6/11/2003 +0200, you wrote:
" Your pupil's difficulty with oscillators, have you never tried them with
the Franklin? I built one in the early '60's using a 12AT7 double triode
minimum external components, using a high quality component L/C circuit, I
think from a BC458 or suchlike. The stability checked professionally was
exceptional, comparing easily with Colpitts or Hartley types."
Yes, I am familiar with all of these oscillators even the
Armstrong ( often misnamed) and Franklin.
The problem is with the beginning students' construction skills at the
beginning.
I have a demo with an Hartley Oscillator where I demonstrate all
the various problems with oscillators. Along with the oscillator I have a
crystal clock oscillator, mixer (diode) and audio amplifier. This also is
used as a frequency mixing demo later in the workshop.
The tank coil is air wound with on no form (spring) for
microphonic effects. There is no electrostatic shielding initially to
demonstrate stray capacitance effect on the oscillator. A variable power
supply to demonstrate Vdd variation effects, a keyed circuit with some RC
on the power supply for chirp and two fixed capacitors ( one Z5U and one
silver mica). I can touch the ceramic capacitor and remove my hand a
listen to the slow change in frequency as it cools down to room temperature
and do the same with the mica for comparison.
Then I tell the students about a guy that built an oscillator that by
everyone standards would be worthless. He became famous and made a good
deal of money off of it, well, up until he returned to Russia
("Theremin" Lev Sergeivitch Termen) . And we play with some of sound
effects on the demonstration instrument. The young students get a real kick
out of it.
It was intended for a phasing type SSB rig using the wonderful octal
plug-in B & W
350 audio phase shift network..
Sounds kind of like a CE 10A.
73
Malcolm GM3UIN now F5VBU
73
Bill wa4lav
NNN
----- Original Message -----
From: "Bill L. Fuqua" <wlfuqu00@uky.edu>
To: <tentec@contesting.com>
Sent: Wednesday, June 11, 2003 6:52 AM
Subject: Re: Re: [TenTec] great RX320 review
>
> I do not need an an Argonaut V. I was was interested in a very basic
(primitive)low cost receiver that would take advantage of the existing
processing capability that most people have. Something better than the
cheapest kits that TT has at the present.
> I teach classes on radio theory and construction. My students learn the
basics of radio and build not only kits but their own projects that they
design. Good VFOs are difficult for beginners. An inexpensive package with
the local oscillators (PC controlled) mixers and some simple filters are all
they need to bread board a number of different instruments. And using their
home PC as a low frequency IF processor helps keep it within their budgets.
>
> 73
> Bill wa4lav
> -----Original Message-----
> From: "WILLIAM MANSEY" <wa2pvk@msn.com>
> To: <tentec@contesting.com>
> Date: Tue, 10 Jun 2003 21:28:29 -0400
> Subject: Re: [TenTec] great RX320 review
>
> Why not save yourself a lot of time and effort by purchasing an Argonaut
V? Combine that with Carl's, or similar control, software and your laptop
computer and you are good to go. The Argonaut has a very good receiver. I
have not compared the specs but based on my observations and recollections I
would say the Argo has a better receiver than the RX-320. Just my opinion
on the matter. Good luck with whatever you decide to do. 73, Bill
> wa2pvk@msn.com
>
> Please visit my home page:
> http://mysite.verizon.net/wa2pvk
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>
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