Figure 1: The Vanguard 260
Posted 06/21/2016: (This article is continued from part one)
The Arduino looks to be the best bet. I want to run this satellite receiver in conjunction with one of my homemade tablet computers. But, the receiver board is too big to fit into any of them (including the rather large original homemade tablet). Because of these size restrictions, the sat receiver will have to be outboard from the tablets, and it’ll be better to use an Arduino to control the Xtal replacer circuit (so as not to need to run coaxial cabling from the tablet to the receiver for the DDS signals). An additional benefit to putting an Arduino inside of the satellite receiver is that I can then use it with any of the tablets I have in my possession. The new plan does add a little cost to the project though (probably another $20, approximately, for the Arduino board).
The *bargain* part of this project is slowly fading. A new commercial weather satellite receiver is in the area of $250 – $300 dollars. Given that I paid only $20 for the Vanguard, we have a ways to go, before we admit defeat. 🙂
Figure 2: The gPredict software shows the three satellites moving towards my position. Until the shaded area encompasses my little blue dot, I have no reception. NOAA #19 is shown two hours away (click to enlarge).
Figure 3: NOAA #18 missed me this time around! (click to enlarge).
For those interested in the AD9851A, here’s the data link:
http://www.analog.com/media/en/technical-documentation/…/AD9851.pdf
It’s a very interesting chip. With a 30 MHz reference clock, and 180 MHz system clock, it’s said to be good for within .4 Hz. Awesome! Actually the AD9851 is a DDS chip, in the category of “Direct Digital Synthesis.” This is awesome, but a little off-track for my way of thinking. Vistors will notice that I like discrete electronics technology (i.e. mostly 60s/70s/80s circuitry with individual transisors, or very simple ICs. In this way, I can have a bag of general purpose parts, and fix anything I have (in a pinch), even by raiding some other equipment (say, an old transistor radio or stereo) – for parts. It makes my setups self-sufficient, whereas all the new equipment depends on (often) narrow niche special purpose integrated circuits. So, the DDS is a downgrade in that way, unless I decide to pack a few extras in my toolkit.
The Vanguard has very little in the way of integrated circuits. I have yet to draw a schematic for it (maybe that will tell me exactly what’s going on with the crystals) – but I see only three ICs, and one of them is an NE565A. The NE565A is a PLL/FM detector IC that was introduced in the the sixties (which is incredible, IMO). So, it’ll be found in a LOT of older equipment, and that part should be scavengable.
The two others (CA3035 wide band amplifier), and CA3028 RF amplifier) – are products of a decade later (70’s/80’s) – and so should also be scavengable items.
The screenshot in figures 2,3 of this page is of a program that has been released under a free software license (gpredict, located at gpredict.oz9aec.net). As a derivative work of that program, this screenshot falls under the same license. Details about the license are to be found at:
Note that this webpage and its author have no connection whatsoever to the gpredict software, or its authors.
WB8LZR 