[Microwave] Rigs that have all mixer injectionfrequencies derived from a master oscillator

[Dr. Gerald N. Johnson]

On Tue, 2009-04-14 at 22:47 +1200, Dave Brown wrote:
> ----- Original Message ----- 
> From: "Dr. Gerald N. Johnson" <geraldj at storm.weather.net>
> To: <microwave at mailman.qth.net>
> Sent: Tuesday, April 14, 2009 3:32 AM
> Subject: Re: [Microwave] Rigs that have all mixer injectionfrequencies 
> derived from a master oscillator
> 
> 
> > On Mon, 2009-04-13 at 22:57 +1200, Dave Brown wrote:
> >>  I've been looking hard at the Icom 706 recently as it has 1 Hz 
> >> dial
> >> resolution and all mixing frequencies are locked/derived from a 30 
> >> MHz
> >> master oscillator that can be externally sourced and GPS referenced
> >> etc very easily.
> >>  See this-
> >>
> >> http://g4hup.com/FC/DFS30/DFS30.htm
> >>
> >> The 706 also has the advantage it is getting cheaper all the time 
> >> as
> >> its now no longer current at Icom-although I expect there's still a
> >> few new ones available.
> >
> > I like the FT-857(D). The DSP isn't great though. The optional
> > mechanical filter for CW enhances weak signals, the DSP doesn't. It 
> > also
> > derives most all frequencies from a single module that is available 
> > as a
> > TCXO to give about 0.1 ppm, enough to meet US federal regulations 
> > for
> > CAP, MARS and other such services. I don't recall that the frequency 
> > is
> > one convenient to lock to a 10 MHz standard, but a synthesizer can 
> > take
> > care of that. Its not all that great a benefit to have the IF 
> > controlled
> > to 1 Hz when the transverter is wandering about kiloHertz or more.
> >
> > I really like the way I can run CW with it in SSB mode, no stupid
> > frequency shifts, no mode shifts, just start sending (hard on 
> > sequencers
> > though), and the way that its noise blanker works. I've heard the 
> > 706
> > noise blanker is deficient.
> >
> > And for two bands, it will compute the frequency offset and hold the
> > power down to under 4 watts, in transverter mode. Unfortunately 
> > reached
> > by a menu, not a front panel switch.
> >
> > 73, Jerry, K0CQ
> 
> Tks for the input Jerry, the intention is to  have BOTH the 
> transverter AND the transceiver referenced to a common frequency std- 
> as you said, there's not a lot of point having one without the other. 
> It's just that knowing what rigs are capable of being totally 
> referenced to a master frequency is the tricky part as the makers 
> don't consider this a selling point worth including in the usual data 
> sheets. And there seems to be a common tendency to use really oddball 
> frequencies for those rigs that DO have a master osc for all mixers. 
> Binary v. decimal, I guess.
> 
> Will check out the FT-857-I may have a copy of the service manual 
> here.
> 
> 73
> Dave, ZL3FJ
> 
> 
I misspoke about the stability of the 857. Its only 0.5 ppm. Still good
enough for an IF. The oscillator is a little plug in board. The standard
oscillator is a discrete transistor with trimmer cap and buffer stage.
It would not be hard to add a varicap to phase lock that oscillator. The
TCXO is a package oscillator on a similar board with less adjustment as
I recall. Neither would be difficult to replace with a buffer and cable
to an external source. The frequency is inconvenient, 22.625 MHz.

Another feature of the 857 (and the 897 uses the same circuits mostly)
is that it has a band output on an 8 pin min din plug. I've worked out a
circuit to make it have separate outputs for VHF band select and for
transmit PTT output. It takes a 4514, and 4030 and a half dozen logic
level MOSFETs. I may write it up for CSVHF or MUD soon as I prove it
works. It may also apply to the 817. The 857 and 897 has a normally
unused pin on the power connector that when grounded converts them to
lower power battery mode. That's not well documented.

I bought an 857 trading in a TS-130, and a TS-440. I liked it so well, I
bought another at a hamfest. Unfortunately the second one had been reset
one level too far taking out the software alignment that I need to
restore. It will probably get more use as IF for microwave operation.

73, Jerry, K0CQ