I don't know. I forgot. Got to think. But you don't need upper & lower sideband crystals. There's another way to do it without. It's been a while.
Yeah that's true. Well, I am working within my means. Unfortunately that's not allot...lol. But if you use crystal for upper and lower sideband, they have to match your filter. See, I will be building the crystal filter from crystals. So I know I will have to leave that part variable but is the BFO is not a nifty drifty I can get away with it being very close and should be able to adjust it right in. My main concern is the center frequency. I want that to be right on so that the BFO is all I will be concerned with.
If I use the same crystal frequency filter as the 1st IF in the receiver, that should work right? I'm concerned about the picking up the carrier frequency in the ballanced modulator, because I could build a crystal oscillator and I would be locked right on other than stray capacitances and temperature effects on the crystal. What scares me is the filter picking up the crystal oscillator and drowning out the modulated signal. What do you think? Should I be concerned with that? Maybe I need allot of shielding. I would like to put the modulator in one small, well you know, cat food can...lol.
Also, does anyone know the impedance of these Shure mikes? If it is low Z then I need to take advantage of that. I need to avoid rf pick-up.
Again, I'm baffled by your concerns - presumably it's a comms mike?, it designed for that use - and your mike preamp should be well screened and suitably filtered, both to tailor the speech bandwidth, and to completely reject any RF.
To answer the first question, the filter will be after the ballanced modulator so I am concerned with pich up through the air.
On the second question, I can't find any amplifier designs you don't pay for, for the Shure mikes. If it is low Z then that will give additional rf rejection. I should probably assume it is but would like to know because if it is high Z then I want to efficiently get it into an OP Amp.
I'm gonna sling up a 40 meter "inverted V" antenna tonight and I got two amplifiers I built a while back. The final is an MRF454 80 watt amp. So just trying to get their quickly. As soon as I get the antenna up I could start using CW. I have a 40 meter PLL and the pre-amp is 0 t0 10 watts adjustable with wave shaping for key clicks. But want to get the SSB going ASAP.
The datasheet for the Shure 444 mic is linked in Google.
It is unbalanced, "high impedance" and the recommended load is 100k ohms.
It cuts off frequencies below 300Hz and above 3kHz. It has a 10dB peak at 3kHz.
The newer Shure 522 mic is completely different from the old Shure 444 that you are talking about. **broken link removed**
I would seriously suggest you get the receiver redesigned properly first - there's nothing in that design that's going to help in a transmitter, and a lot that's going to make it badly wrong.
But I want to know what in particular you find just totally unacceptable? Let's talk turkey. It appears you got something to say.
Does it bear any resemblance to the parts you've posted?.
If so, it has far too many audio stages, almost none of which are required, and almost none of which have supply decoupling - these are adding instability, noise, and distortion - and nothing of any use. The stages appear to be thrown together, with no concept of design or calculating values - and with random darlington pairs appearing for no good reason. There also appears to be no sensible audio filtering, just odd capacitors here and there.
Likewise the rest of the stages are poorly, or not at all, decoupled (and mostly badly designed).
All you need for the audio stages is:
Detector.
One amplifier stage (optional).
Bandpass filter (simple opamp would be handy).
Power amplifier.
Just checked the two ARRL designs I mentioned earlier, one use a passive low-pass filter followed by a 741, driving headphones. The second uses a passive low-pass filter directly driving a power amp IC to a speaker.
Perhaps you would care to go through the design of one of the stages?, it's reasons for been there, and how (and why) you calculated the values.
Sorry, but it's truely the worst radio design I've ever seen, even beating the super-regen fisaco's of a year or two ago.
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