Re: Chineses TCXO for 28 MHz IF 2M transverters

John Klem

Someone has already done spectral testing of similar units (link below).  It's a long read, but the bottom line is that at least some of these are very likely to be (cheap!) synthesizers, with spurs and higher phase noise than you will find in a good TXCO.  The article documents degraded receiver performance. 

At least those of us in "rich" RF environments might be better off avoiding them.  On the transmit side, it might also be kinder to our nearby amateur friends.  Still, in some cases (like Keith's transverter LO) there may not be better options.

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

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