Hammarlund HQ-140-X

Discussion in 'Amplitude Modulation' started by KA4KOE, Jul 17, 2019.

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  1. K4KYV

    K4KYV Subscriber QRZ Page

    Many AMers don't think that's important, and you hear QSO roundtables with stations 1, 2 and sometimes more kc/s off frequency from each other. Not only does that make the QSO take up unnecessary band space, those receiving with a synchronous detector sometimes have to switch to envelope mode because it may take a second or more for the BFO to re-synchronise with the off-frequency carrier; an off-frequency breaker may not even be heard because his brief transmission is over before the detector has locked in. With a fast-break QSO, receiving with a synchronous detector is usually impossible because inevitably stations in the group won't all be on the same frequency.

    Those using modern day transceivers with digital display shouldn't have any problem zero'ing. All they have to do is adjust the transmit frequency to line up with the VFO in receive mode.
     
  2. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    Even with CW filters at 500 Hz, many operators definitely have a problem zero-beating on CW. The filter is wide enough that tuning to the exact center is not that easy. Also, the shape of the filter plays a very important role in how easy it is to get the signal centered. It is much easier to get the transmitted signal close to a true zero-beat with like a 200 Hz filter with steep sides.

    For CW, I still prefer not transceiving but controlling the transmitter with a separate VFO. That way, a true zero-beat is possible. In fact, such is recommended in the receiver manuals for the Collins 75S-3- series equipment. The 32S-3 / 32S-3A have a CW spotting switch that is active when the transmitter PTO is controlling the transmit frequency. A single switch allows the receiver to control the transmit frequency or the transmitter PTO to control the transmit frequency.

    When an SSB receiving filter is used for CW operation, a lot of operators don't even get within 1 kHz of true zero-beat and when the other station is running a very narrow filter, the signal will just not be heard!

    Glen, K9STH
     
  3. W8KHK

    W8KHK Ham Member QRZ Page

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    Last edited: Aug 11, 2019

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