[600MRG] Fwd: Re: Testing new Transmit downconverter

[Edward R Cole]

Dave,

Thanks for the information.  I read the Elecraft temp comp procedure 
and it seems clear enough.  I am a bit confused that the low temp 
cited is 20C (68F) as a refrigerator typically runs about 4C or 
40F.  I suppose either it is expected the radio temp raises this high 
during the time to reconnect and set it up, or the radio is not in 
the refrigerator long enough to reach 4C (40F).

As far as an accurate 50-MHz source, I will use the +10 dBm output of 
my OCXO at 10 MHz (+/-0.5 E-12).  At 50-MHz the fifth harmonic is 
+/-2.5 E-12.  I can also check the KX3 with my counter (EIP-538) 
which is as good as my Rubidium at 10-MHz.  I have some schottky 
diodes for making harmonics.  Output should be better than 0 dBm.

I wonder if you have measured the KX3 xmit frequency directly?  If it 
holds within 10-Hz on 28-MHz it is usable with eme transverters and 
mw transverters.  A 10-GHz transverter using a 1136 MHz PLL will hold 
to 9-Hz and adding up to 10-Hz keeps the drift just inside the 20-Hz 
decoder filter in JT65.

Of course most mw transverters use a 144-MHz IF so this question will 
have to be repeated once the 2 meter transverter is available for the 
KX3.  Since the 2m LO will also run from the KX3 master oscillator, 
it may not be that bad.  Guess we will wait to measure it.

I am hoping the KX3-2M is stabile enough for use with mw 
transverters.  If so, it will challenge the FT-817 for being the 
"best" mw IF radio (whose requirements exceed 600m standard).

73, Ed - KL7UW

At 05:28 AM 4/27/2013, Dave wrote:
>I also have the KX3 and initially it wasn't even stable enough for 40m wspr,
>see
>
>http://g4fre.blogspot.com/2012/07/kx3-on-qrss.html
>
>At one point Elecraft,  as you say were looking at locking to an external
>reference but its very hard to do that with the SI570DDS so they went for a
>calibration table correction lookup procedure on there web site that needs a
>fridge and a hairdrier
>
>http://g4fre.blogspot.com/2012/12/why-is-kx3-in-fridge-and-whats.html
>
>after I did this the kx3 its stable enough for wspr and qrss decodes on 40m
>so it should be good enough for LF
>
>Dave
>
>Ww2r, g4fre
>
>-----Original Message-----
>From: Edward R Cole [mailto:kl7uw at acsalaska.net]
>Sent: Friday, April 26, 2013 2:33 AM
>To: Dave; 'pat bunn'; 600MRG at w7ekb.com
>Subject: Re: [600MRG] Fwd: Re: Testing new Transmit downconverter
>
>Dave,
>
>This is the mixing approach I favor as one can utilize high precision
>10-MHz references as the LO.  However the IF radio has to be capable
>of transmitting on 10.470-10.480 MHz.  This is outside the amateur
>30m band.  The K3 is able to run there with no issue, but might be
>challenging for other radios (without modification).
>
>I have the K3's little brother, the KX3.  But it is not as versatile
>and also does not exhibit as good frequency stability.  I understand
>an external reference ckt is under consideration at Elecraft which
>may fix that.  Still one might have to design a transverter that
>utilizes a standard ham band as IF.  This may require finding an
>adequate oven controlled oscillator to provide a super-stable LO.  A
>TCXO at 3.0 MHz with 0.5-ppm might suffice (3000 kHz x 0.5 E-6 = 1.5-Hz).
>
>73, Ed - KL7UW
>
>At 04:50 PM 4/25/2013, Dave wrote:
> >I built a true transverter (ie tx and rx converter) for 474.2khz in my uk
> >station and I have been very pleased with it
> >
> >I use the k3 as the IF at 30m and use the K3 10MHz reference as the local
> >oscillator
> >
> >I did use it for a while with a good 10MHz oscillator as the LO and still
> >got decodes
> >
> >To reduce the size of the LF station I have used the FT817 as the IF on
>30m,
> >but mine definitely needed the onboard histab oscillator to get reliable
> >decodes
> >
> >Dave
> >
> >Ww2r, g4fre
> >
>
>
>
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