[VHFcontesting] What separates a decent transverter from an awesome transverter?

[David Olean]

LO drift is a big problem. One of the underlying reasons for the results 
you have seen is the quality of the crystals that are being supplied to 
the transverter manufacturers. Parts that were tested and specified 
originally are showing up in later deliveries with just awful 
performance.  It is hard for small companies with small production runs 
to get anything resulting in repeatable characteristics without 
unmanageable lead times. Note that just about every US quartz crystal 
manufacturer is no longer in business.  I was given a small frequency 
counter as a Christmas present. After a few months, I noticed that the 
timebase had shifted by 4 kHz when measuring a signal at 2 MHz. I 
thought a jump like that was impossible with Quartz.  No telling what 
was left inside the crystal housing to cause it.  My suspicion is that 
it was the General Tso's Chicken option.  I just read the book _Crystal 
Clear. _It is the story about ramping up to produce crystals for WW2 
radios and how the Govt and manufacturers did it.  There were many 
pitfalls to overcome and quality issues to address.  Almost all those 
companies are now gone.

73

Dave K1WHS


On 4/25/2018 7:20 AM, N1BUG wrote:
> One thing I didn't see on your list that always concerns me is LO
> drift. Drift can be a problem for any weak signal work, say a long
> haul CW sked during a contest. If you want to do some of the digital
> modes it can become a critical issue, even a show stopper.
>
> Since I can neither afford nor get my head around the complexities
> of GPSDO locking, I am always concerned about crystal oscillator
> drift in transverters. Usually I do the best I can to build and
> install some type of crystal heater... with mixed results over the
> years.
>
> Sometimes I find things that surprise me. Last summer I measured
> drift on two 1296 transverters: a relatively ancient UHF Units and a
> relatively newer but not current generation DEMI, both as yet
> unmodified. Over a temperature range that caused the DEMI to drift
> over 6 kHz, the UHF Units moved just a bit over 200 Hz! I know which
> one I will be using if I ever get the rest of the stuff together for
> 1296.
>
> Paul N1BUG
>
>
> On 04/24/2018 10:31 PM, Patrick Thomas wrote:
>> Hey all,
>>
>> Subject more or less says it all... I guess better sensitivity,
>> lower noise, better selectivity, and better linearity are the
>> essentials in vague and relative terms, but what attributes do
>> you look for in a REALLY GOOD transverter?
>>
>> Or for those who have gone further into making them... what
>> components, construction techniques, etc., make a difference?
>>
>> Partly this is a question I hear a lot and only have a vague
>> notion of how to answer other than "obviously the expensive ones
>> are better... somehow." :)
>>
>> And partly it is a request for topics for self-guided
>> study/experimentation as I attempt my own homebrew projects.
>>
>> Many thanks,
>>
>> Patrick - KB8DGC
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