Q5 Signal (Corey, N4NGZ), the firm that is now building and servicing DEMI 50,
144, 222 and 432 Transverters, offers a device similar to the N5AC, Apollo 32.
It’s the digiLO and is based on the MAX2870ETJ+ device. It includes a decent
onboard 10MHz OCXO that automatically switches in if the 10MHz ref input drops
below 0 dbm. The phase noise characteristics in the documentation appear to be
a bit better than the A32….but still 10db or more worse than a disciplined
VCXO. Details on the Q5 Signal site. Mounted in a box with a DIP switch it
would make a good signal source.
I use an older version DEMI 1296-28 transverter in my Rover. It has the OCXO
on the XVTR board and I’ve never had an issue with being way off freq or
drifting during a QSO. Once it has been powered up for 5-10 minutes it doesn’t
move around much. I think it’s fine for SSB/CW. Digital modes probably
require something better. I’m building a DEMI 2304-144 XVTR kit. The A32 is
standard now.
73,
Pat, W5VY
Sent from Mail for Windows 10
From: Steve(K1IIG)
Sent: Wednesday, April 25, 2018 6:47 AM
To: VHF Contesting; N1BUG
Subject: Re: [VHFcontesting] What separates a decent transverter from anawesome
transverter?
PAUL,
The Demi Micro-Lo is notorious for drift which of course they have a Syn
board you can replace that requires 10mhz to lock it. You can buy an 10mhz
OCXO for $10 on the internet that will work fine to lock it.
Take a look at this site https://zl2bkc.com/ which also has a replacement
board for the Micro-Lo.
73
Steve
--------------------------------------------------
From: "N1BUG" <paul@n1bug.com>
Sent: Wednesday, April 25, 2018 3:20 AM
To: "VHF Contesting" <vhfcontesting@contesting.com>
Subject: Re: [VHFcontesting] What separates a decent transverter from an
awesome transverter?
> 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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