[TenTec] Receive 17m on Omni ,Tritons, etc.

[Dr. Gerald N. Johnson]

On Thu, 2007-05-24 at 10:34 -0700, Kevin Purcell wrote:
> Interesting tip.
> 
> In the Omni series C (TT 546 Series C) I not that design was rather  
> cobbled together to add the WARC bands.
> 
> They had decided on low side LO so they used that for 17m too. So  
> 4MHz crystal osc mixing with the 5.0 to 5.5 MHz so the LO tunes from  
> 9.0 to 9.5MHz.
> 
> Brilliant!
> 
> With a 9MHz IF you have leakage through the discrete PN diode ring  
> mixer at the bottom of the band of perhaps -30dBm or worse 68kHz away  
> from IF. It gets better as you tune up the band.
> 
> With a commercial ring mixer this isolation (assuming no other  
> leakage (that's a big if)) you should be able to push this to better  
> than 60dB so the leakage would be around -40dBm.
> 
> One possibility to fix this is to mix with a 27068 to 27168kHz from  
> the 5000 to 5500kHz VFO and 22000kHz crystal osc to get high side LO  
> injection. The tuning direction is the same (if I got the math right).

That's how 17m is done in the Corsair II with the annoyance that the
natural sideband is lower, contrary to common usage.

72, Jerry, K0CQ
> 
> I suspect the counter will still work fine (just counting the LO)  
> though it might show gibberish for the MHz digits (preload will be  
> wrong) though it might be limited on top the counting speed (was that  
> why they didn't do it this way?).
> 
> Not tried it yet. Not sure if the stock xtal osc will actually do  
> this. The top crystal is 15.49MHz so it may or may not work at 22MHz  
> (fundamental versus overtone). Or an extra separate xtal oscillator.
> 
> OH, well it works on the other bands :-)
> 
> Or perhaps later drive it with a DDS/tracking PLL to replace the LO  
> generator.
> 
> On May 23, 2007, at 10:31 AM, duane eaton wrote:
> 
> > I receive 17m on my Omni D ser.B Thusly.
> > Set band to 20m.
> > Use SB-R, Tune from 14414 to 14434.
> > Tune resonator near 21m until noise increases and tune for signals.
> > I estimate the mixer is using the 5th harmonic of the PTO
> > which for the 17m band is at 27.068 minus 9 MHz is 18.068.
> > On 20m the PTO tunes from 5.0 to 5.5 MHz.
> > This worked on my 315 Rx and suppose it will work on any of the  
> > similar
> > 9 MHz rigs, Triton, Argos.
> > Best regards, el Rob
> > KI6FZF
> > rabbueche at dslextreme.com
> >