Re: Chineses TCXO for 28 MHz IF 2M transverters

Robin Midgett <K4IDC@...>

Alternatively, use a LPF such as these from QRPLabs to derive the sine from the square wave. I did that for the Si570 synthesizer output to drive an old GE MASTRII transmitter chain to make a 6m beacon; works great.
Robin Midgett K4IDC

On Sat, Dec 8, 2018 at 6:11 PM John Klem <klemjf@...> wrote:

I have been interested in similar low-cost TXCOs, but concerned about what's in the package.  It would be very interesting to see an output spectrum. 

Given that you are probably driving a mixer that is basically a diode switch, it's not clear to me that a square wave would be a problem.  Even with a sine wave LO, you are creating mixing products around multiples of the LO frequency, and any decent amount of filtering downstream of your mixer takes care of that problem.  Does anyone know more about this topic?  I have considered a 222 transverter LO using a MEMS oscillator chip (square-wave output), and was thinking that LO filtering would not be necessary.

John, AA5PR

On 12/8/2018 9:22 AM, Keith Morehouse wrote:
I don't know how good these are or what the ultimate output level is, but this is the frequency you need if you want to stabilize your older DEMI (or whoever) 144 MHz transverter.  They are being sold by the pair, so you have one to break and one to use.  They shouldn't be too hard to integrate into almost any 28 MHz IF transverter.  Look up the specs of your mixer for LO power requirements, check this one and then either pad it down or, more likely use it as is or drop a 0.99$ MMIC in as a buffer amp. I am sucked in for a pair.

I've had a EBay search active for this frequency TCXO for two years and this is the first usable (hopefully) unit that has come up.  I messaged the seller to make SURE it was a sine-wave output (most of these are clock oscillators with TTL or CMOS square-wave's output) and he verified it was sine-wave.  If not, I guess I could legit return it by showing EBay his message.

I bought a TCXO advertised just like this as a drop-in for a Yaesu FT817 and it worked fine and was dead on freq, out of the package.  It was 20% the cost of a Yaesu equiv part.


Keith J Morehouse
Managing Partner
Calmesa Partners G.P.
Olathe, CO

Join to automatically receive all group messages.