Subsonic Radio View Topic

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Hello, Does anyone else have one of these? This is the system from the early 1950s that has 3 pieces: 1101A 100kc oscillator, 1102A Multivib/pwr supply, and 1103A Synchronometer. I got it at a hamfest in 1981, basically the guy had it for $200 and I came back at 4 pm and took it off his hands for $35! I really only wanted the Synchronometer since I already had one that needed a few parts, but ended up with the whole shebang. Last time I had it all going was about 10 years ago - when you fire it up it makes the electric meter turn fast!

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Anyhow I was talking to someone at the Charlotte meet and somehow the subject came up, and he said these are like hen's teeth and in high demand, especially the 1103A. I had no clue, I thought they were not rare at all. Was he right, are people on the lookout for these?

Since they do take a lot of real estate and suck power, I would think not so much. But GenRad did make a good product and these are no exception. Cheers, Dave.

I realize that. What I don't understand is how this other station can do it. I can download every ride and show in Disneyland and/or the audio. Even shows can be. I downloaded the subsonic TV pro channel, configured it to my site address, and I can see the files from it on the tv. However, when I hit play, it says 'retrieving' but then returns to the menu rather than playing the video.

Corby: Not looking to sell (yet!), trying to confirm/refute any desirability. I guess I want to make sure my heirs now know not to put it out with the trash! The synchronometer is very cool, though! The 1 kHz whine as it runs is very distinctive.

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And the backlit dial is the best! When I had it all running a while back, I was able to get it to settle out after a couple weeks to an error of between 10^-7 and 10^-8, checking it with the microdial and WWV twice a day. Specs are about 10^-9 but I think those days for my unit are long past. And I had to make a couple of repairs to the oven after I got it and saw the 100 kHz crystal in the spring mount.

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That thing is really a small bar! After being used to the FT243s it was quite interesting to see it.

Cheers, Dave.

Subsonic Radio View Topic We May Be Different

:: Author Message K.Haroon Site Admin Joined: 11 Dec 2005 Posts: 1318 Posted: Thu Oct 13, 2011 3:19 pm Post subject: Questions on Transonic Flight The regime of flight from the critical Mach number upto M = 1.3 is called Transonic Range. Reducing the thickness/chord ratio on a wing will reduce the transonic variations in lift and drag coefficient and delay the onset of shockwave formation. The Mach cone semi-angle decreases with increasing speed. At mach numbers below the critical Mach number 'Dutch Roll' phenomenon can happen. Dutch Roll phenomenon 'can exist' at low Mach numbers. The two areas of speed instability in transonic aircraft are below 'VDmin' and from 'M 0.89 to 0.98' As an aircraft accelerates through the transonic speed range the coefficient of drag increases then decreases. This drag increase encountered at these high speeds is called wave drag.

The drag of the airplane wing, or for that matter, any part of the airplane rises sharply, and large increases in thrust are necessary to obtain further increases in speed. This wave drag is due to the unstable formation of shock waves that transforms a considerable part of the available propulsive energy into heat, and to the induced separation of the flow from the airplane surfaces.

Throughout the transonic range, the drag coefficient of the airplane is greater than in the supersonic range because of the erratic shock formation and general flow instabilities. Once a supersonic flow has been established, however, the flow stabilizes and the drag coefficient is reduced. Source: (Shock stall is separation of the boundary layer behind the shock wave. The Mach trim system, depending on the Mach Number, will adjust the 'Stabilizer' not the elevator trim tab. On a typical symmetrical airfoil, as the free stream Mach number approaches M 1.0 the centre of pressure will move aft to about 45% chord. On a typical transonic airfoil the transonic rearward shift of the CP occurs at about M 0.75 to M 0.98 On an example wing (Symmetrical at 2 deg alpha with MCrit at M0.75) At MFS (free stream Mach) of M0.75: - Mini shockwaves form on upper surface of wing.

CP 20% MFS between M0.75 and M0.81: - As Mach number increases the shock waves join up and move aft. At MFS of M0.81: - A single clearly defined shockwave is formed at 70% chord. CP moves aft to 30% - Bottom flow (not so fast at 2 deg alpha) is not yet sonic. Its just below it. At MFS of M0.89: - Top shockwave is stuck at 70% chord (high pressure behind it).

Bottom shockwave is at the trailing edge. CP moves forward to 15% At MFS of M0.98: - Both shockwaves at trailing edge. CP moves back to 45% (in the transition from M0.89 to M0.98 ) At MFS of M1.4: - Bow shock attaches (MDet) - Trailing edge shocks become oblique. CP 50% To be able to predict compressibility effects you have to determine the Mach No. Transonic speed is a speed at which locally around the aeroplane both supersonic and subsonic speeds exist.

Speed of sound varies with the square root of the 'ABSOLUTE' temperature. Because the speed of sound and the TAS both increase with the square root of the absolute temperature of the air, the mach number will 'remain constant' with an increase in OAT for an aircraft flying at a constant flight level and CAS. Vmo can be exceeded in a descent at a constant mach number because Vmo is an IAS and descending at a constant mach will require an increase in TAS which will increase dynamic pressure. Just to visualize: TAS / Local Speed of Sound = Mach No e.g. 20/2 = 10 Descending means getting into warmer air i.e. Speed of sound increases. Lets say the speed of sound becomes 5 The eqauation then becomes 20/5 = 4 This is incorrect because our mach number had to be constant at 10.

The equation then has to be: 50/5 = 10 Thus TAS has to increase. Its the opposite in a climb, since we are getting into colder air where the speed of sound will be decreasing.

Thus to maintain a constant mach number with decreasing speed of sound the TAS will decrease. Assuming ISA conditions, climbing at a constant Mach Number up the tropopause the TAS will 'Decrease'. In ISA conditions as you climb up 'To' the tropopause but 'Not Above' the tropopause, temperature reduces. Thus local speed of sound reduces and at constant Mach number TAS also reduces.

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Sketch 51 3 for macui application. However above the tropopause tempearture remains constant so local speed of sound remains same and thus TAS is same at constant Mach. On a non-swept wing, when the aerofoil is accelerated from subsonic to supersonic speeds, the aerodynamic centre shifts from 25% to about 50% of the aerofoil chord. Aerodynamic Center is a sationary point only when the airflow is subsonic. When airflow over a wing becomes supersonic, the pressure pattern over the surface will become 'Rectangular'. During acceleration from subsonic to supersonic speed the centre of pressure movement will be irregular, forward and aft, but overall rearward to 50% of the chord.

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Movement of the Aerodynamic Center from subsonic to supersonic is from 25 to 50% Display posts from previous: - All times are GMT Page 1 of 1 Jump to: You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum.