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Re: Measuring Resonant Frequency of Traps
Some newer transceivers, like the Icom IC-7300, include a graphical SWR plot function. Put a dummy load on the other end of the trap and have the radio show you the swr plot. That might help some.
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Michael Maiorana
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#491
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Re: Measuring Resonant Frequency of Traps
Did we miss the part where William explains they are FNG Baofeng techs? Eric KE6US
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Eric KE6US <eric.csuf@...>
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#490
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Re: Measuring Resonant Frequency of Traps
Or, obviously, just a transmitter with an SWR meter (perhaps Diz's tandem match). But the single number representing SWR into an assumed 50 ohm antenna system is not nearly as informative as the two
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Jerry Gaffke
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#489
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Re: Measuring Resonant Frequency of Traps
Might not be a good idea to test the traps in isolation. The remainder of the antenna system can affect resonance.
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Jerry Gaffke
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#488
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Re: Measuring Resonant Frequency of Traps
Google "nanoVNA",? $50 for a vna good from khz to ghz. Display is teensy and thumbswitch is cranky, but performance is exceptional. Newer versions are coming out. Non-trivial for the neophyte, but
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Jerry Gaffke
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#487
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Re: Measuring Resonant Frequency of Traps
Connect the parallel resonant circuit in line with their transceiver input and tune for a null or connect it across the input and tune for a peak. You could also have them reconfigure it as a series
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Eric KE6US <eric.csuf@...>
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#486
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Re: Measuring Resonant Frequency of Traps
Although it may qualify as "fancy" equipment for the "desert island" scenario, an antenna analyzer can easily show you the SWR of a filter at a given frequency, and you can manually plot a curve if
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Ryan Flowers
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#485
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Measuring Resonant Frequency of Traps
Thought I'd throw this out for the group. I got trapped [sorry!] into schooling some "Baofeng Techs" (FNGs) who are interested in getting into HF about building trap antennas. Of course, being new,
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k6whp
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#484
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Re: Si5351 output power
If the load is of high enough impedance, you might get by without the push-pull pair. So I might try first without Q72,Q73, drive your tube rig over a twisted wire pair (or coax) from the junction
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Jerry Gaffke
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#483
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Re: Si5351 output power
Jerry I like the idea of the ubitx audio stage. I should have all the parts on hand to give that a try. Thanks! 73 Don ve3ids [email protected]> wrote:
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Don VE3IDS
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#482
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Re: Si5351 output power
I like the notion of two 74ACT04 gates in push pull. But wonder what kind of trouble you could get into using that to drive a transformer. Whenever I see a full description of the design process for a
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Jerry Gaffke
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#481
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Re: Si5351 output power
It is sobering to think how they got by with such simple gear in say, the late 1920's. Amazing that a single tube regenerative receiver works at all, let alone well enough to use on the ham bands. A
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Jerry Gaffke
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#480
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Re: Si5351 output power
It would work fine. I used my K2 as a VFO for a Drake 2NT until I could get something built for it. We might overthink things in the digital age. They used to be a lot simpler, and the still could be.
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Eric KE6US <eric.csuf@...>
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#479
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Re: Si5351 output power
Something to keep in mind in circuits that use multiple power supplies is power sequencing: It is important that the 5V comes on before the 3.3V and turns off after the 3.3V when the 3.3V turns off.
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Steven Dick, K1RF
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#478
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Re: Si5351 output power
Hi all Loading an Si5351A output at 50-ohms also affects phase noise. I did a study of Si5351A phase noise, particularly in relation to the QCX CW transceiver http://qrp-labs.com/qcx . One of the
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Hans Summers
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#477
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Re: Si5351 output power
If you read the datasheet, the Si5351 claims to have a 50 ohm output. But yes, it is primarily designed to replace cheap 4 pin crystal oscillators. Jerry
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Jerry Gaffke
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#476
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Re: What level math is in the RF design books?
Good news: Algebra for designing and biasing bipolar circuits. Not so good news: Partial differential equations for biasing FET circuits, though I¡¯d probably just copy an oscillator circuit rather
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Bob N1RC
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#475
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Re: Si5351 output power
It¡¯s a clock generator and was designed to drive a logical load, that is, a CMOS or TTL input, and definitely not a 50 ohm resistance. The first rule in a situation like this is to *read* the data
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Bob N1RC
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#474
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Re: 7 MHz Oscillator Ideas
I¡¯d grab a 40 meter tank circuit from one of the older handbooks for a cheap and cheerful solution. Or a DDS circuit like this
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Bob N1RC
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#473
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Re: 7 MHz Oscillator Ideas
Thanks for all the ideas gents, I need to get some parts from Diz and Rex and start experimenting. Hopefully after Christmas.
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JT Croteau <jt.tobit@...>
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#472
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