The amplifier, made up of Q1 (Assuming beta = 200) and it's associated components, improves the input impedance of the OpAmp circuit from 47KΩ to slightly less than 43KΩ. It also adds much needed noise to the high performance 741.I would recommend not running your op amp Vcc supply from your Q1 collector.
Hey, I do appreciate you guys
Anyway I found out that my driver amp I had built years ago is a class C.....
So I found an old linear I built and it is the worst piece of junk. I mean it was built years back. Anyway it's got some nice transistors so guess what I got to do now?
But I am very surprized that when I turn on the modulator, it comes up right on freq. I sealed it up. All I need is this linear and I will give you some signal reports.
Back to work......
Well one big deficiency in your drawing is the output of your balanced mixer is wired directly to your crystal filter. A passive diode mixer must have it's output matched to a wide band 50 ohm load. This can be done with either passive or active circuits, but is a requirement for decent performance. A mini-circuits application notes for balanced mixer goes into this subject extensively. The input of your crystal filter is going to be a very complex value and be very frequency dependent, anything but being a good wideband 50ohm match.
Lefty
I do like most (ok.. ALL) of your comments "lefty" but.. it also makes me feel very "retro".. and.. "mike" does always have his watchfull eye about itPlese - let us enjoy this Xmas..
Sorry Xanu, not quite sure I follow what your trying to say. Hope you do not think I was trying to nitpick. Lefty and I just added our 2 cents as it seems SV would not post if he did not want a comment.
I hope you have a LPF before your antenna.
Well one big deficiency in your drawing is the output of your balanced mixer is wired directly to your crystal filter. A passive diode mixer must have it's output matched to a wide band 50 ohm load. This can be done with either passive or active circuits, but is a requirement for decent performance. A mini-circuits application notes for balanced mixer goes into this subject extensively. The input of your crystal filter is going to be a very complex impedeance and be very frequency dependent, anything but being a good wideband 50ohm match.
Lefty
Holy Komoly! That just reminded me of something. If anybody knows anything about PLL then you know that a broader resolution is easier to filter off the phase sidebands. In turn you get a harder lock and even broader bandwidth. I like working with about 10K resolution. I found that by changing the resolution to like 11KHz and 12 and even 9KHz and using a processors internal timer as the reference frequency and jam loading the timer I can achieve multiple frequencies inside the 10KHz steps still using 10KHz reference of 9 thru 12 or 13 which is even cleaner and better. But there are some freqs that are not possible to derive even using this combination of schemes. Well, I like using a Hartley as the VCO in my PLLs so I could place a varactor in place of one of the variable caps to warp the frequency in a VXO and use this as the processors clock, since the internal timer is reference from the uProc clock and use it as an external clock source. What that would do would allow me to achieve every square inch (figuratively speaking) of bandwidth in a sigle loop PLL!!!
Awesome!
Yes, that is not a method often seen (VXOing the reference) in commerical useage but for ham homebrew it certainly simplifies a PLL system. I've not played with PLL much, the post phase detection filtering requirement calculations always scared me
If ever get around to building my 'holy grail' HF receiver I would most likely go with a DDS generator for the LO, I need something that goes from 40.455mhz to 70.455mhz. Just wish those Analog Devices's DDS chips came in packages that I could actually solder and work with
Lefty
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?
We use cookies and similar technologies for the following purposes:
Do you accept cookies and these technologies?