Wasn't me.
I couldn't remember who had said it, but you're right Artisan it wasn't you, it was Robert Chryfasis who once upon a time used to frequent here. No wonder I couldn't find the post here, it was on Facebook which I seldom comment on but someone was looking for Rangemaster crystals and I told him where to get them (thanks to our own Rugster here letting us know). Anyway, this is how that little discussion on Facebook went:
Richard Powers: I recently bought three crystals for a Rangemaster from https://www.surplussales.com/categories/3006-crystals-1-mhz-to-399-mhz/ I bought two 1600 and also on a whim a 1710 just because it was there. It's a limited selection but was glad to find anything.
Robert P Chryfasis: Don't forget that the crystal on rangemasters needs to be 6x the broadcast frequency for that type of crystal. I think for the programmable crystals they can be on the fundamental frequency or if its a pll board it replaces the divide x 6 counter chip.
Richard Powers: @Robert P Chrysafis Needs to be x 6 what???
Robert P Chryfasis: 6x the broadcast frequency. So if you want 1200 kHz you will need a 7.2 MHz crystal. At least that is what i recall with the old crystal design. It is run through a cd4004 dive by 6 ic iirc.
Richard Powers: @Robert P Chrysafis Ok. I have no idea what your talking about. I Rangemaster came with a 1700 and a 1620 crystal and stamped as such appropriately.. I've never tried using any other crystals and this is the first I've ever heard of getting for example a 7.2mhz if you want to broadcast on 1200khz. I haven't tried the ones I just got yet, wasn't planning on it anytime soon, only got them for future use, but now you got me worried...
Robert P Chryfasis: @Richard Powers better ask Keith. They usually come stamped from Keith that way to avoid confusion but I believe they are actually 6x the fundamental frequency.
Oh, on Facebook I had said I had bought 2 1600 crystals, but that's not correct, it was actually 2:1400 crystals and a 1710. I've been thinking about experimenting with broadcast below the expanded band because it seems a shame that most antique radios would not be able to receive 1700. I was thinking that maybe with a salt water ground that 1400 might be able to achieve an acceptable range.
Wow, that's a new one on me @richpowers. I had always assumed that the crystals for the older Rangemasters were on the fundamental frequency, with no division or multiplication required to get to the final operating frequency.
Maybe (just maybe) I'll send an email to Keith to ask him. Not sure if he'll want to give up what he might consider proprietary information, but it's worth a try - especially as he stopped selling that older version of the Rangemaster years ago.
I bought HC6/U crystals for 1600, 1610, 1400, and 1370 a few years ago, in case I want to experiment with building a simple crystal-controlled Part 15 transmitter. I assumed that they would also work in older Rangemasters, but perhaps not. If I had an older Rangemaster I could take a look, to see if I could reverse-engineer it, but my unit is a newer one.
If I find anything out, I'll post it here.
@rugster I think I found out what he may have been talking about.. I think he was confusing it with how the frequency agile works. I was asking Google AI about Crystal vs Frequency Agile units and something it said made me interrupt:
Me: "Wait, are you saying that today's frequency agile units do still utilize a physical crystal?"
- Ultimate stability and accuracy: The quartz crystal remains the most reliable and stable timing source available for a variety of electronic applications. It provides a consistent "heartbeat" or reference frequency that is far less susceptible to temperature changes, aging, and other factors than simple LC oscillators.
- The reference for frequency synthesis: Modern frequency synthesizers like Phase-Locked Loops (PLLs) and Direct Digital Synthesis (DDS) use the crystal oscillator's stable output as a master reference signal. The PLL or DDS then multiplies, divides, and manipulates this single, stable reference frequency to create a broad range of other frequencies with the same stability.
- Not a one-to-one relationship: The core innovation of frequency-agile circuitry is that the relationship between the crystal's fixed frequency and the device's output frequency is no longer one-to-one. This frees the device to operate across multiple bands without requiring a unique, bulky, and expensive crystal for each channel.
No, I don't think he was @richpowers. Yes, a frequency agile unit, whether it's some kind of PLL system, or a clock generator/DDS arrangement, needs a stable frequency reference, which is almost always a quartz crystal. I think Robert was talking about the crystals that Keith used to sell for operation on a single frequency. He was saying that the older Rangemasters used to take crystals on 6 x the operating frequency, and a divider circuit divided that frequency down to the operating frequency on the AM band.
In other words, if you wanted a crystal for operation on 1400KHz, it wouldn't be a 1400 KHz crystal - it would be an 8400 KHz crystal (1400 x 6) which the transmitter circuitry would divide down to 1400 KHz. Whether that is how the Rangemaster circuitry actually operated, I don't know. It seems a bit unnecessary to me, but that was Robert's belief.
@rugster Well you know me, I don't really know, I haven't contacted Keith about it nor have I tried slipping one of the crystals I bought from a different supplier into my Rangemaster (the one you had found), but I will try it sometimes in the reasonably near future and see what happens with the these other 1400 crystals I bought (I just want to experiment with lower frequencies, most likely I'll stick with the 1700 crystal I have always used anyway). Presently I don't even have my Rangemaster installed, it's all just talking points.
Anyway, I didn't realize the frequency agile units still involved use of a crystal, which surprised me because I thought it was some kind of software based thing.
@richpowers - if you want to generate an accurate and stable frequency, you need a reliable reference. That's where the crystal comes in. In some cases, the frequency generated by the crystal is multiplied and/or divided to reach the final desired frequency or, in the case of a PLL circuit, the frequency of a free-running VCO is compared to a stable frequency that comes from - yes you guessed it - a crystal, and corrections applied to keep the VCO on-frequency.
The big benefit of systems like this is that a wide range of frequencies can be generated from just one crystal. You still need a crystal though.
.. The big benefit of systems like this is that a wide range of frequencies can be generated from just one crystal. You still need a crystal though.
So, are frequency agile units as stable as the crystal controlled units? I realize now they both are crystal based, but the frequency agile units introduces additional circuitry, as you point out, to multiply that crystals frequency to whatever frequency desired. So there's a potential of introduce some interference into the signal that the older models would not. Would you say that's accurate? Also are frequency agile units any less stable in regard to changes in temperatures (weather) than a non-agile unit would be?