Cascode triodes in T-R switch

Discussion in '"Boat Anchor" & Classic Equipment' started by K1APJ, Jun 3, 2021.

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  1. KE0ZU

    KE0ZU Ham Member QRZ Page

    If you want an inexpensive solution, use a simple, cheap open frame 120VAC 3 pole double throw relay that can be driven/switched directly by your Ranger. The crystal socket on the rear panel of the transmitter is the switched 120VAC power.

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    Any of these solutions for your single station setup is fine, however, keep in mind that using anything other than a 120VAC relay will require an additional switch and power supply.
     
    Last edited: Jul 6, 2021
    W3SLK likes this.
  2. KI4ZNV

    KI4ZNV Ham Member QRZ Page

    The problem with the open frame relay is that it's comparatively slow... full break-in turns into almost-full-break-in if you aren't careful. But I have used them for years and they have been fine.
    --scott
     
  3. K1APJ

    K1APJ Premium Subscriber QRZ Page

    Well, if you think about it, ALL ac relays are slow - intentionally so....

    I used a B&W TR switch when I first started, but it was kind of silly, I still needed a relay for muting, and at the low power levels and 50 ohms a second contact on the relay would have worked as well. Break-in operation was not a consideration.

    But also, back then there were plenty of transmitters and receivers working into tuned feeders/high impedance antennas. The T-R problem is different then, that is probably why the knife switch was popular.
     
    Last edited: Jul 6, 2021
  4. K4KYV

    K4KYV Premium Subscriber Volunteer Moderator QRZ Page

    And it will hurt the dynamic range of the receiver. You want as few active stages as possible between the antenna and the selective i.f. filter. No tube or transistor is noise free or perfectly linear. The active T/R switch is inherently a compromise between convenience (of QSK) and performance (of the receiver).
     
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