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TS-530S Tuneup & RF in Shack

Discussion in '"Boat Anchor" & Classic Equipment' started by KB1RHB, Dec 10, 2019.

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  1. K7TRF

    K7TRF Premium Subscriber QRZ Page

    Well the Tune (i.e. Plate) and Load controls do constitute a limited range matching network. Yes, it allows you to match into a wider range of antenna system impedances than solid state rigs that don't have internal tuners but it's still limited to something in the 3:1 to maybe 4:1 SWR range most of the time. A decent outboard tuner will allow you to match into 10:1 or higher SWRs which means much greater mismatches than what the rig's PI network can handle.

    The Drive control is for peaking the drive circuitry and also peaking the receiver's preselector and isn't really involved in output matching but I suspect that was a typo in your post.

    Yes, the idea with an external tuner is to match whatever the antenna system gives you to something pretty close to 50 ohms. So a good tuneup procedure that also follows good operating practices (i.e. minimum QRM) is to tune up your rig into a 50 ohm dummy load. Then with a Kenwood hybrid it's easy to switch to the antenna tuner and set the rig to Tune mode which is relatively low power and safer for the final tubes in terms of working into a bad match. Don't retune the rig, just adjust the external antenna tuner controls to achieve a low SWR. Once you figure out good settings for different band segments (e.g. CW/Digi vs SSB band segments) write them down on a note card and tape it to your desk near your tuner so you can quickly get back to saved settings.

    Yes, there are so called EFHW (End Fed Half Wave) antenna systems that have become popular in recent years. They don't use traditional radial systems and with a bit of counterpoise wire or a long enough stretch of coax they just feed through a 49:1 or 64:1 RF impedance matching transformer into the end of wire that's a half wavelength long on the lowest supported band. They'll then yield fairly good match (i.e. low SWR) on the harmonically related bands. So if your end fed antenna is roughly 130 feet long and fed with an appropriate matching transformer it should yield a decent match on 80m, 40m, 20m, 15m and 10m and the SWR may not be too bad on some other bands.

    But without that matching transformer that's not really what you have. If you have 130 feet of wire fed from your coax and you add a few ground or elevated radials attached to the coax shield you have a 1/4 wavelength antenna on 160m that generally won't provide even a halfway decent match on other bands. If you don't have the radials or some kind of counterpoise wire (typically a single elevated wire that's fairly long for the frequency in use) you don't really even have a 1/4 wave monopole (aka Marconi antenna) and your home's electrical grounding is serving as the missing part of the antenna. That's not good from an RFI standpoint and can lead to both transmit problems and receive noise problems. Your tuner may or may not be able to take the impedances presented by that kind of an antenna and match it reasonably well to the rig.

    If you really want to run a single end fed wire I'd either configure it as an EFHW with an appropriate matching transformer or run the wire straight out of the single wire terminal of your tuner and add whatever you can manage as radials/counterpoise. That second suggestion (a shack tuned single wire) really isn't a great way to go as your transmitting antenna starts right in your shack so it's very common to have RFI problems doing that but yeah a lot of us did that back in the day and it certainly got us on the air and antenna tuners are still sold with single wire connection posts on the back so someone must still run this kind of antenna.

    Personally I'd run a well understood and well behaved antenna system such as:

    - Dipoles or Fan Dipoles to cover multiple HF bands
    - A shack tuned Doublet fed with balanced feed line
    - A trap or set of parallel (aka Fan) verticals with a good set of radials
    - An inverted-L run against a decent set of radials
    - An EFHW with appropriate matching transformer and either a longer coax run choked at the appropriate place or a short piece of explicit counterpoise wire at the transformer box

    Or something along those lines instead of 130 feet of wire fed with coax back to the shack. Yeah, you can probably make the single wire antenna work, but there are better antenna systems out there that are well behaved and typically work better with fewer problems than what you've described.

    Either way, play with tuning up your rig into the dummy load to get a handle on how the rig tunes into a good load and to get used to properly tuning the rig. Then figure out what you need to do with your antenna system to cover the bands you want to operate.
     
  2. AI3V

    AI3V Ham Member QRZ Page


    Also, exactly what is the plate current at the dip on 160 and 80?

    Rege
     
  3. AI3V

    AI3V Ham Member QRZ Page

    The plate and load. controls ARE a impedance matching network, they match the output impedance of the pair of final tubes to the antenna system.

    The drive control tunes the input (grid) of the final.

    Peak the drive
    Dip the plate
    Adjust the load for 225ma plate current (ip) when the plate is at the dip.

    ......

    Then, if you cannot get 225 at the dip, (usual symptom is you "run out" of load control)

    Connect dummy load, adjust for 225, then hook up the tuner, adjust it for 1:1 vswr, touch up rig for 225, should only need slight readjustment if any.

    Rege
     
  4. KB1RHB

    KB1RHB Ham Member QRZ Page

    My mistake, this is wrong -

    The Z gets translated by N^2 (N squared), 49:1 translates 50 ohms to 120K ohms, 64:1 to 200K
    ohms.


    Regards, Dana.
     
  5. KB1RHB

    KB1RHB Ham Member QRZ Page

    Thanks gentlemen, I have a lot of work and investigation to do as a result of all the
    feedback.


    Regards, Dana.
     
  6. K7TRF

    K7TRF Premium Subscriber QRZ Page

    You're right on transformers in general, but by convention RF impedance matching transformers are typically specified by impedance ratio, not by turns ratio.

    So the 49:1 matching transformers we're talking about have a 7:1 turns ratio and the 64:1 transformers have an 8:1 turns ratio. Same thing with Baluns, when we talk about a 4:1 balun we're really talking about a 2:1 turns ratio or at least a 2:1 voltage ratio depending on the balun topology.

    IOW, you had it right the first time :)
     
    Last edited: Dec 11, 2019
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Dana, unless I missed something I'm still not clear whether you're using a commercial EFHW with a matching unit or just 130' of wire fed at the end. It sounds like you're just using 130' of end-fed wire with no matching unit incorporated.

    The DRIVE control doesn't have any impact on antenna matching, it matches the driver stage to the 6146s in the rig, and also acts as a preselector for receiving; you should notice the effect on receiving if you tune in a signal and rotate the DRIVE control -- it will "peak" the received signal in about the same place as it peaks the drive to the final amplifier stage.

    With just a 130' end-fed wire, you absolutely need an antenna tuner outside of the rig, and should need that on every band except perhaps part of the 160m band. If you could get the rig to produce "full output" on 80m without using an external tuner, that's an amazing coincidence as that really shouldn't happen, and the stress on the LOAD capacitor can be rather enormous, to the point where you can arc that capacitor and cause it to fail.

    As suggested, an easy way to use the external tuner, and you really do need to use it, is to introduce lower power (CAR control turned down so output power is 10W or something), adjust the tuner for minimum SWR, which should be close to 1:1 at any given tuned frequency, and then increase power (CAR control) to full, and tune up the rig itself without re-adjusting the outboard tuner at all. The outboard tuner will require adjustment any time you change bands, or even if you change frequency by 2-3% of the operating frequency within a band.

    Attaching a good RF ground or a tuned counterpoise to the tuner GND connection can make it all work with greater stability and help eliminate RFI. Without a ground return or something to balance the system, results can be rather unpredictable and you are indeed using the rig's chassis and all connected cables as a haphazard ground system, so it can all conduct undesired RF current and radiate.
     
  8. KA9JLM

    KA9JLM Ham Member QRZ Page

    I have never had much luck using 1 half of a antenna.

    A tuner with a long wire connection may work half fast.
     
  9. N8YX

    N8YX Ham Member QRZ Page

    Plenty of us can and do make this work all the time.

    The key is a good ground/counterpoise. Also key is to get the wire as high into the air as possible.
     
  10. KA9JLM

    KA9JLM Ham Member QRZ Page

    Exactly what the OP does not have. o_O

    Near as I can tell from here, In Texas.

    The Counterpoise should not be inside of the shack.
     
    Last edited: Dec 11, 2019
    AI3V likes this.

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