On Jan 25, 2011, at 11:12 PM, Garey Barrell wrote: > Kevin - > > A scope can be used, although I find it easier to just listen to the receiver. > > Think of the two filter passbands as the letter "M" as depicted on Page 29 of > the TR-4 Manual. The goal is to adjust C130 so that it sits in the valley > between the two filters. If you turn on the CALibrator and tune through it > in either direction in receive mode, you'll see the S-Meter go from noise > level up to 10 over S-9 or so for a couple of kHz, then down to noise again, > back up to 10 over S-9 for a couple of kHz, and then back down to noise > level. If you get this pattern, then C130 is close. Fine adjustment is to > listen to the receiver noise (no antenna, high band, no signals) and switch > back and forth between USB and LSB. The 'pitch' of sound should be similar > in both positions. If one sounds low or 'bassy' and the other side sounds > high and 'hissy', then adjust C130 slightly until they sound about the same. > They will NOT sound EXACTLY the same due to anomalies in the filter > passbands, but they should sound similar. > > Just in case you are 'really' asking about nulling the Carrier in the > Balanced Modulator, in this case you can clip the ground lead of the scope to > the chassis and then just lay the probe tip near the Driver tube socket. Set > the SIDEBAND switch to "X", key the transmitter in X-CW with the GAIN at full > CCW, and adjust C127 and R85 for MINIMUM signal. Again, it's easier to > listen on an external receiver if you have one available, and do the above, > adjusting for minimum signal in the receiver. > > 73, Garey - K4OAH > Glen Allen, VA > > Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line > and TR-4/C Service Supplement CDs > <www.k4oah.com> > > > Kevin Elliott wrote: >> I have been reading all of the posts in the new Drake archive and the old >> Drake archive trying to learn as much as I can about my TR4. To you old >> pros this will be a rookie question, but I am of the belief that if you >> don't ask you don't learn. Okay I have read where it has been said that you >> can use a couple of different ways to set C130 correctly. One being use a >> digital receiver and listening for the matching null and the one that I want >> to ask about is using a scope to adjust them. Where will the scope probe be >> connected to read this information or is it indirectly connected with a loop >> of wire around the oscillator tube to see the nulls. >> I got the Great service CD and I love it and will be going through it and >> digesting all I can. >> Thanks >> Kevin _ KG0MN >> >> > > _______________________________________________ > Drakelist mailing list > [email protected] > http://mailman.zerobeat.net/mailman/listinfo/drakelist
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