Hi Brian, On Tue, 05 Jul 2011 13:26:33 -0400, bjon...@mindspring.com wrote:
>Finally I >remembered my freq counter (keeps track of my 10Mhz frequency standard) >so I hooked the drake up to it directly and threw a 1W cw tone at it and >was off by 1Khz (i.e the DR7 displayed 14.2140, but the counter showed >14.2150) (flipping over to the RV75 results in the same result) A subtle, but important, distinction is that the TR-7 shifts the *transmit* frequency from what the dial reads on CW. It seems that the majority of the import rigs shift the recieve frequency. Thus, the DR-7 readout will be around 800 Hz off from your frequency counter in CW transmit. IIRC, this is not true for AM, so try an carrier in AM mode. >So my first question is: >When trying to use WWV to determine receive frequency, what is the best >way to do so? Apparently how I have been doing it for years is >incorrect! What I usually do is set the PBT to center, RIT off, and adjust for zero beat with WWV's carrier in SSB mode. This is easier if done during the periods when WWV does not transmit audio tones. You will need to turn the volume up as you approach zero beat in order to hear the beat note better. Use the strongest WWV you can find. I'm curious as to how you were doing it that you think is incorrect? >Question number two: >If both my transmit and receive frequency are off the same amount (1Khz) >is there an adjustment on the DR-7 that will allow it to display >correctly (My first glance through the service manual did not reveal any >way, but I thought I would ask the experts here) or is that something >that would have to be fixed through an alignment of the TR7? (or at >1Khz off is it better to just tape a sticky note to the table reminding >me to add +1?) The only adjustment that could possibly cause a TX/RX shift problem here is the RIT center pot on the parent board. Otherwise, your RX and TX are the same as the signals come from the same source. There is no seperate reference for the DR-7. You rig may need to have the RIT center adjusted, and/or a frequency alignment of the oscillators. This is not a hard thing to do, but you do need a sensitive counter to read the oscillator signals. First, check the +10v adjustment; if it's too far off, it will need to be set to 10V and you may need to touch up the AGC/S-Meter adjustment. Then you will adjust the 40 MHz, 13.695 MHz, and 8.05 MHz, in that order. That should get you there, but it's a good idea to check the fixed passband adjustments while you are at it. They are almost always off a little. Follow the adjustment procedure in the service manual, without skipping any steps, and you should be fine. I've found that it's a good idea to isolate the counter probe from the signal under test with an as high in value (carbon) resistor as you can use and still get a stable reading, as the load of the counter can shift the oscillators a tiny but (probably not enough to be concerned, but I'm picky). This seems to be most apparent on the 40 MHz. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
