CHU @ 7335?

Discussion in 'Ham Radio Discussions' started by NM7L, May 23, 2020.

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  1. NM7L

    NM7L Ham Member QRZ Page

    So I was playing around with a recently acquired Drake 2-C receiver on 40 meters. Around 7330 kHz [remember, Drake 2-C receivers are 1) old; 2) analog; and 3) tube-based] I am picking up CHU from Canada. They moved back in the early 2010s to 7850 khz, but any online documentation acquired has their 7 MHz operating frequency as 7850 kHz. Did I miss the memo here ... or has CHU reverted back to 7335 kHz? Or, has this 2-C developed the knack for playing nostalgia programming?

    Perspiring minds would like to know ...
    N1VAU likes this.
  2. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Easy to research:


    K4AGO likes this.
  3. K1APJ

    K1APJ XML Subscriber QRZ Page

    Well, I believe your observations are more or less accurate, but your conclusion is not perfectly correct.

    The 2-C is a 3.5 - 4.0 MHz receiver with crystal-controlled converters for the other bands. When set to the 40 meter band, an 11.00 MHz crystal is used, so, for example 7.335 MHz is converted to 11.000-7.335 = 3.665 MHz, which is where the receiver is truly tuned. You read 7.335 on the dial (the black scale.)

    Now, lets suppose that the incoming signal is CHU at 14.670. The same 11.00 MHz crystal converter would give an output at 14.670 - 11.000 = 3.670 MHz. very nearly equal to the 3.665 setting when the receiver is tuned to 7.335! If you look at the 2-C preselector tables (attached,) it is entirely possible to tune the preselector to 14.670 MHz when the bandswitch is in the 40 meter position.

    So, it is indeed possible to receive CHU on 14.670 (if the tuning dial is set to 3.670 (which looks like 7.330 if you read the 40 meter scale.) The preselector also needs to be set up to about 9.5.

    FWIW, the same technique will receive WWV on 15.000 if the tuning dial is set to 4.0/7.0 MHz

    Attached Files:

    Last edited: May 23, 2020
    WA6OSX and W0PV like this.
  4. NM7L

    NM7L Ham Member QRZ Page

    Thank you very much for that insight. I knew there had to be some rational explanation for what I was witnessing short of stating that "CHU moved on us & no one told us", or I was personally reliving the "Static" episode of The Twilight Zone (using CHU as the vintage station heard instead of station WPDA as portrayed on TTZ).

    Now that chart in the 2-C manual makes more sense now ...
  5. WA4ILH

    WA4ILH Subscriber QRZ Page

    When I was stationed on a Navy ship in the Mediterranean back in the early 70s, we had Collins S line in the ham shack. The Collins S line was ham band only with just a slight slop over at band edges. The trick was, if you tuned the receiver perselector way off band, you could sometime pick up another band. I discovered this quite by accident one day when tuning the (20 meter?) ham band and I slid the preselector way down toward the 80 meter band and low and behold, I was picking up Armed Forces Radio on 6030 KHz.
    Tom WA4ILH

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