Cross modulation, by that I assume you mean Intermodulation distortion as I think they are similar.
I have been preaching Mini-Circuits for some time now to no avail (See this thread) https://www.electro-tech-online.com/threads/shure-mike-model-444-freq-scheme-ssb.85841/
but this is a great off the shelf solution for a Rx front end mixer.
Mini-Ckts has real good specs for intermod as well as Noise figure. I think you could almost build an entire RX unit from Mini-Ckt parts. They have amps, mixers, filters, and VCO's.
For the TX modulator, Mini-Circuits does not spec their parts below 500KHz so I am not sure how well the would work at audio modulation frequencies, but I suspect they would be fine. Maybe someone could test it and report the results.
Man, this diode ring with '914s is just does a great job! I put another filter on it. But I still got problems with that oscillator.
What is your criterion for working great? What sort of test equipment have you used to verify your circuit?
This web site has a pretty good write up on mixer design.
**broken link removed**
Note this excerpt from above cited website.
4 diodes are expensive -
well first off you could save yourself a lot of angst by buying a commercially manufactured mixer. Minicircuits SBL-1 would be an example. It comes in a can with a pin out the same as an 8 pin DIP and can be bought for only a few dollars. You could shop around for suitable diodes cheaply available e.g. Hewlett Packard's HP5082-2800 or similar. In North America Dan's Small Parts seem to have a variety and I think the mixer is also available. Links to all sites mentioned appear at the end of this tutorial.
5. diodes need to be well matched -
don't even consider using 1N914 types if you want results. The HP 2800 types are pretty well matched but I'd still check a bunch for foward and back resistance.
My criteria is an attentive well trained ear and eyes. My equipment is cheap as they come. a 40MHz scope and a voltmeter and any signal generator is an oscillator built by muy and homebrew receiver.
For the price of the SLB-1 you could buy a hundred or a thousand diodes and match them.
Isn't there an IC of matched diodes?
Or an IC that has access to 4 diodes that would be acceptable?
Vermint,
I do not understand your question #1,
#2: It all depends what you decide to do. There are few possibilities. You can use seperate IF frequencies (and filters) but always the offset will be determained by simple +/- maths (of two incoming frequencies, followed by +/- math, followed by the filter set to the "+" or to the "-").
- Some TRX use just one Xtal IF filter (one filter, one offset for Tx/Rx),
- Some use 2 Xtal Filters for the same IF (the classic is the 9MHz IF and XF9A filter for Tx and XF9B filter for Rx with the better quality filter being used for RX). IF freq is the same and the offset is the same i.e. only the filter changes but the rest of IF hardware is the same for Tx/Rx.
- Some TRX may have the signal chain totally seperated with different IF freq used for Tx and Rx. Therefore, for the same principal frequency the offset will be different due to the "math" as above..
xanadunow
Alright alright...I'm not talking about in a transceiver. I'm talking in actual practice. What I am saying, is to have the actual proper beat note, if the transmitter's carrier is set 1.5KHz below the carrier, as in the carrier of the balanced modulator, then a receiving station would have to tune the BFO oscillator to the same 1.5KHz offset in order to make it appear as a normal AM signal. Is this correct? I believe I'm finding it to be so. Where before I had read that you would zero beat the signal with what would be the carrier. This works in AM but the audio intelligence is not offset as in SSB. You see, these are things taht are neglected to be cover in most all of the material I come across.
I found a recording of real ducks quacking and it sounds just like your radio except its sound is clear. But I can't attach it here. And I am a poet and don't even know it.
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