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Out of Band Antenna Tuning

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Comments

  • Mystery HamMystery Ham Member
    edited August 2016
    Steve,

    There's also a significant portion of North America where the FCC has no remit, to  which I'm sure VE and XE hams will attest.  :-)

    73
    Mystery Ham
  • Bob G   W1GLVBob G W1GLV Member ✭✭
    edited December 2016
    Maybe I misinterpreted the original comment, for that I'm sorry.
  • Ned K1NJNed K1NJ Member ✭✭
    edited December 2016
       I use a noise bridge for manual tune (in or out of band) for tuning my external
    antenna tuner.  The MFJ-212 "Matchmaker" works for me.  It will pass exciter-
    level RF so you won't easily smoke it. You tune for minimum noise.
    Usually it's quite close to minimum SWR.  Doesn't produce tune-up qrm.

    Ned,  K1NJ

  • Bob G   W1GLVBob G W1GLV Member ✭✭
    edited December 2016
    The IARU does come into the picture here also. I'm sure they don't want you to spill RF all over the place to satisfy your listening pleasure. There are rules and there are rule breakers.
  • Mystery HamMystery Ham Member
    edited August 2016
    You're certainly not alone in thinking the suggestion meant transmitting out of band, Bob.

    Among the interesting things happening on this thread is that hams who have become accustomed to tuning while transmitting are being reminded of the days of first tuning for maximum noise floor to get close and then transmit for final adjustments.

    It's that first step that is helpful for listening out of the amateur bands, especially if the band's noise floor is otherwise below the receive system's noise floor.

    Cheers
    Mystery Ham
  • Ned K1NJNed K1NJ Member ✭✭
    edited December 2016
          Right you are, Paul.  I wonder if there might be a clever DSP way to
    generate noise internally.  I'm not asking for this.  Just thinking out loud.

    Ned,  K1NJ
  • Jay -- N0FBJay -- N0FB Member ✭✭
    edited December 2019
    The solution might be to go out and buy a manual tuner with the ability to bypass the tuning circuit at will.  That way when you do your antenna matching for the wavelength you are listening to without the need for transmitting to gain a match.  

    I'm not aware of any current transceiver with an internal tuner which provides manual L & C controls.   Nice idea, but not a priority in my book.

  • Mystery HamMystery Ham Member
    edited August 2016
    Jay,

    Flex has done an amazing job providing a well thought-out path to allowing separation of the operator from the shack with the Signature Series products. It seems much effort has been taken to do as much processing work as possible in the Flex hardware to minimize network bandwidth requirements to provide the opportunity for the operator to work as many as 8 receivers in the comfy chair across the shack from the radio, in the comfy house across the garden from the shack, as well as in the comfy Tahitian bungalow across the world from the house, (provided 35 or so Mb/s bandwidth, otherwise you may be limited to 4 or 2 receivers)

    So, I'm glad that you think the ability to remotely adjust inductance and capacitance in the internal Antenna Match Unit using software sliders from SSDR is a nice idea.  Because this idea allows those folks who, in the addition to the radio amateur bands, monitor the bands in between and have a need or desire to provide a better antenna match to the radio(without transmitting) to attempt get that weak signal another 5 to 10dB above the receive system's, not the frequency band's, noise floor.  And this idea keeps those operators in their comfy chair, comfy house, or comfy Tahitian bungalow, rather than trekking a well-worn path back to the shack. 

    Preamp, you say?  Save that for when the signal is 10 to 20dB below the receive systems noise floor.  An LC circuit's noise figure is much lower than a preamp's noise figure.

    So, if the S-Meter only sees S0 when the radio is turned off or when the antenna has been disconnected, and if the only place to operate SSDR is within arms reach of an Antenna Match Unit, I fully understand your "not a priority" position... Otherwise, I would be curious to know your thoughts.

    73,
    Mystery Ham
     
  • Mystery HamMystery Ham Member
    edited August 2016
    Paul & Ned,

    I've never used a noise bridge before, however clearly, based on the various schematics I've seen yesterday and today, a noise bridge does put broadband noise on the antenna. Granted it is less than a mW, but it would seem to be illegal, in most countries, to transmit across the entire HF spectrum at once.

    Mystery Ham

  • WaltWalt Member ✭✭
    edited April 2019
    For those worried about radiating energy on other-than the ham bands, you may refer to your 'FCC' regulations, that usually have a 'Part 15' and look up the rules of incidental radiators.

    All the signal levels, measurement techniques and allowable permissions are defined with ways to calculate them are there, printed up for everyone to read.

    Time to put your ham license to use and get your calculators out to see if that 1 milliwatt (or whatever your noise bridge level is) at the antenna will exceed the rules.  In whatever country your in.

    And then decide if you can use the noise device with a clear conscience.

    And then have a pint !
  • k3Timk3Tim Member ✭✭
    edited December 2016
    Having an adjustable L-C to 'pre-tune' the antenna for SWL would be a nice enhancement. 

    "Somewhere" out on the web I thought read one could xmit under a certain power level on HF. Recall the BPL (broadband over power lines) used HF frequencies.

    If this were not the case, all the VNA/Antenna Analyzers would be illegal. A web search of "DIY Antenna Analyzers" and subsequent schematic research shows they use of a DDS in the design. I stumbled on the web info after looking at some RFI problems I was having that seemed to be strongest at 13.56Mc. A search of "13.56 mhz rfid" was interesting as that is one of the ISM (aka, junk) bands.

    Am I correct in assuming a DDC - SDR is the only device that can receive both amateur and SWL bands w/o compromise? The point being, the 6Ks while fine HF amateur xcvrs also excel at double duty of SWL. 

    _..--
     Tim  - k3Tim
  • Mystery HamMystery Ham Member
    edited August 2016
    From personal experience, most modern amateur gear makes for excellent SWL gear.  Some of the better Amateur products will employ bandpass filters for the operating bands.  The 6700 has them.  However for 60m and outside the radio amateur bands, they are switched out.  Many other products will use low pass filters that switch in and out depending on the band selected.

    As far as SWL products that I own, none employed bandpass or lowpass filters.  They also did not employ antenna matching circuits.  However due to their overzealous preamps for small antennas, and weak mixers, I could frequently get interference several MHz away from local AM broadcast (MW) stations.  However, by using an outboard antenna match with adjustable L & C, I could frequently bring the desired signal out of the mud and eliminate the interference.

    The 6700 and 6700-R are both very good, no transmit on the R... However, I discovered from reading the hardware manual that, while the 6700-R has no transmit hardware, it apparently has an antenna matching unit (tuner).  That little fact has me wondering if my suggestion wasn't already in the works.

    Mystery Ham
  • Mystery HamMystery Ham Member
    edited August 2016
    Tim,

    I'll just paste this in from another posting a couple of days ago.  The Link is the result of searching for minimum power without requiring a license of some sort.   

    I've never heard of an antenna analyzer requiring a call sign to be input so it can ID itself while it's attached to an antenna. Nor have I seen an analyzer limited to the edges of the ham bands. Perhaps there is some room within the law in various countries to allow using a momentary low power signal to provide analysis and automatically match an antenna system on an otherwise receive only device.

    This may shed some light... http://transition.fcc.gov/ftp/Bureaus/Engineering_Technology/Documents/bulletins/oet63/oet63rev.pdf

    Now, perhaps, in the case of  radio amateur equipment, a signal cannot be emitted under any circumstance regardless of power due to whatever compliance testing may be required...  But that fcc document  has me wondering about the 6700-R and it's apparently transmitterless AMU.

    Mystery Ham

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