Hi Garey, Many thanks for that insight...
There's obviously more afoot here than I first reckoned on---a LOT more! Hi Hi. I must say, though, I DO like your idea of actually monitoring my own on-the-air signal through the R-4---and you're oh-so-right, the receiver has incredible AVC that "tames" the signal without need of any sort of "extra" input from me (as in crankin' down the RF gain control to prevent ear drum fracture!)... I think I'll do just exactly that from now on...in fact, I got a good taste of this very thing the other night when a fellow I was working on 160 CW said that my transmitted signal was "jumpy" by times: sure enough, monitoring myself confirmed this to yours truly (and that very contrast in tone is probably what highlighted the high pitch of V9 in the first place!). The fix...? A couple of rapid rotations of the band, mode selector, and crystal selector switches, of the T-4X! Thanks so very much again, Garey---your wisdom re. "...things Drake" is greatly appreciated by all who frequent this Reflector... ~73!~ de Eddy VE3CUI - VE3XZ ********************************* ----- Original Message ----- From: "Garey Barrell" <k4...@mindspring.com> To: "drakelist" <Drakelist@zerobeat.net> Sent: Tuesday, October 12, 2010 4:25 PM Subject: Re: [Drakelist] T-4X CW Sidetone Oscillator > Eddy - > > Yes, you can change the sidetone frequency that way. However, (there's > always a 'however',) the sidetone frequency is set to approximately the > same frequency as the CO is offset for CW. This is so if you set the > incoming CW signal for approximately the same tone as the sidetone, your > transmitter will be close to the other station's frequency. The > frequency is typically around 800-900 Hz, and a secondary problem is > that it is more 'sawtooth' than 'sinusoidal'. There are a couple of > assumptions in this scheme that no longer necessarily hold true, but > that's another 'however'. > > This tone is ALSO used in the TUNE mode, the electronic equivalent of > 'whistling into the microphone', to produce a single tone SSB signal to > tune up with. The lower edge of the filters in the T-4X is not as steep > as the later models, so moving down to 450 - 500 Hz _probably_ would > be ok. But obviously the tone generated must be within the passband of > the LSB crystal filter. > > The resistors and capacitors are selected to produce a 90 degree phase > shift at the desired frequency to set the tone that is generated. All > Rs and Cs must be the same value. Someone made up a chart of the values > for each frequency, I'll see if I can find it. When you look at where > those components are located, you might be more interested in the > following suggestions. :-) > > I just set the receiver to ON, so that it stays on all the time, so I > can hear my OWN signal. The AVC does a terrific job of minimizing the > loudness, which I help by just pushing the phones forward rather than > right over the ears. This works great, I know exactly where my > transmitter is with regard to the other signals, and am listening to a > nice clean audio tone. > > The other 'recommended' fix is to just use a keyer with it's own > sidetone, and put the receiver in STANDBY. You can either turn the > SIDETONE control all the way down, or just don't connect the cable, as > long as you don't need VOX! > > Another way would be to use the ~-60VDC level on the key in the UP > position to turn off an external audio oscillator that comes on when the > key is DOWN. > > If you use a straight key or bug, then do what we used to do and just > listen to the transformer hum!! :-) > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-B, C-Line& > TR-4/C Service Supplement CDs > <www.k4oah.com> > > > Edward Swynar wrote: > > */Hi Guys,/* > > My poor old tinitus-rattled ears find the internal CW sidetone > > oscillator frequency of the T-4X to be very fatiguing after > > awhile...it's /too high/ in pitch for my liking in extended operating > > sessions... > > Has anyone ever /lowered/ the sidetone monitor frequency in their > > T-4X...? Would any such change simply entail increased values of one > > (or all) of the resistors R70, R71, & R72 (330K ohms stock each), as > > well as increased capacitances for one (or all) of the > > capacitors C129, C130, & C131 (180-pfd. stock each), at sidetone > > oscillator V9a (12AX7A)...? > > Many thanks for any & all feedback in this regard... > > */~73~ de Eddy VE3CUI - VE3XZ/* > > > > > > _______________________________________________ > > Drakelist mailing list > > Drakelist@zerobeat.net > > http://mailman.zerobeat.net/mailman/listinfo/drakelist > > > > _______________________________________________ > Drakelist mailing list > Drakelist@zerobeat.net > http://mailman.zerobeat.net/mailman/listinfo/drakelist > _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
