Nope. It became nice and quiet again. Objective accomplished, I'd say.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
In a similar way I wonder if you could make a dual or N section PI filter with transductors, say drive some inductors into saturation to lower the inductance.
DC
Current dependent inductance. Sure.. (I know next to nothing about saturation.) ..it just costs a lot more power than biasing a cap.
George H.
someone=20
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In a word "ignorance", or perhaps laziness. There is soo much good freeware just for bothering to search.
someone=20
news=20
provider=20
better=20
I ran a comparison between APN and astraweb. Astraweb won by a clear margin. Thus i use astraweb.
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would
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at DC
someone
Do it George.
Yes, sign up with a real news server. I am using news.individual.de which costs 10 Euros per year. AFAIK you can pay up for more than one year to cut down on the wire fees. It's a server of the university in Berlin, Germany. Works nicely, used it while on the road this week.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Yeah, that's a known technique. Wenzel published a wide-range VCO using that method waayyy back in RF Design magazine.
Hey, it's on the web!
-- Cheers, James Arthur
On a sunny day (Sat, 14 Nov 2009 13:04:56 -0800 (PST)) it happened snipped-for-privacy@yahoo.com wrote in :
Hey, that is a nice paper, sure 20MHz to 150MHz with +-0.04 dB flatness is impressive. I will keep that diagram in mind, you never know :-) Thanks!
impressive.
You bet. Sharing fun stuff--that's why we're all here.
-- Cheers, James Arthur
Wow, it has a core reactor in there. That could get those anti-nuclear protesters all riled up :-)
I wonder why they don't just send DC through the aux winding on the core. Ok, causes some non-linearities but in an oscillator that rarely matters.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
The radioactive reactor core (Ferroxcube) just has 7 turns of #30. Dey ain't no 2nd winding to energize. So they scavenged a relay coil. Pretty cute, eh?
-- Cheers, James Arthur
Oh, and of course the control winding has to be outside the RF magnetic circuit, to avoid loading the oscillator.
--James
Except that it could become tough to find those Wabash relays some day.
Not really. You can just place an inductor in series, done it a few times.
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
Ahh, an isolating inductor does take it out of both the magnetic and RF circuit, as I said you must, but Joerg, Joerg, Joerg--that's one extra part. That's 5 cents wasted!
(And, of course, with just 7 turns on it you'll need _amps_ to saturate that Ferroxcube core, versus 100mA for the relay coil.)
-- Cheers, James Arthur
Yeah, but what's the relay going to cost?
Just put on a lot more turns. Should still be cheaper than the special production process of removing the switch of a relay and placing an iron rod there (in a way that it doesn't fly off during rough shipment). Plus the switch needs to be chucked and the local authorities might not let you do that via the usual waste containers :-)
-- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
t DC
Cool, External magnetic field rather than just bias current through the inductor??
sorry for dissing your idea Jan.
George H.
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at DC
Right. At Wenzel's operating frequency the inductor doesn't have enough turns to saturate easily--you might need 10A or more. Hence the relay coil with lots of turns + soft iron magnetic conductor / concentrator.
Another way is to wrap the control winding around the entire toroid (i.e., not through the hole), but, at 400MHz it's impossible to do that without coupling to the resonant winding, wrecking havoc on stability.
Diss? No, you were right--this takes a lot more power. Each technique has its uses.
-- Cheers, James Arthur
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srk at DC
"> Diss? " dis is slang for disrespect. As in "don't be dissing my wheels".
But perhaps I shouldn=92t use slang with such an erudite group?
Say, speaking of the voltage controlled low pass. I was trying to draw a circuit to do this. The best I could come up with, (And I'm not happy with it), is the following.
Vcontrol---R1R1---+ | || | || Vsignal---||-R2R2-+----||---Vout || | || C1 | C1 C(v) C(v) | GND
Where R1 is a bias resistor R1>>R2, R2 is part of the low pass. The C1's are for blocking the control voltage. [C1>>C(v)] And C(v) is the voltage dependent capacitor.
George H.
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I O hDriving home today I realized what a silly circuit that is=85
A few opamps could give=85
|\\ +------------------| \\ | |\\ |- >--Vout Vcontrol-+-| \\ +-| / |+ >--RRR--+---+ |/ Vin--------| / C |/ C | GND
Exactly how to do the addition and subtraction is a bit of a detail.. I also didn=92t want to draw all the other resistors.
Say if you drive both sides hard, you could use the distortion to make a mixer. (I think.)
George H.
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