[Lowfer] A couple of crude Antenna Matching techniques - will either one work

[Douglas Williams]

I wonder how close attaching an NE-2 to the hot end of the coil and tuning
for maximum brightness would get you?

On Fri, Dec 1, 2017 at 10:54 AM, Brian, WA1ZMS <wa1zms at att.net> wrote:

> My 2 cents on this.....
>
> 1) Andy may be suprised how well his HF SWR bridge will work on 630m. The
> Pout readings may be off, but the null for lowest SWR will be there even if
> incorrect in magnitude.
>
> 2) Tuning under TX power could be an issue for some TXs based on the class
> of operation the PA uses: Class A, B, C, D, E. Switch modes amps can act
> strange under active load pull. Any amp can too though.
>
> 3) An ideal meathod for live tuning under TX power (for me) has been to
> place a 6 to 10dB power attenuator in the PA output path. The PA will run
> with a "reasonsble" load while you go outside and tune away for max antenna
> current. The RF power and current at the antenna will be much lower, but
> also less chance of getting RF burns as you tune and poke around. An
> attenuator might be cheaper (homebrew) than an antenna analyzer.
>
> 4) I've done all the above for 2200m & 630m myself.
>
> -Brian, WA1ZMS
>
> > On Dec 1, 2017, at 10:14 AM, John Bruce McCreath <weazle at hurontel.on.ca>
> wrote:
> >
> >
> >
> > Hi Andy….can you clarify a few things for me.  Is the bottom end of your
> coil grounded, is the capacitor
> > in parallel with the coil, are you tapping the feed line inner conductor
> near the bottom end of the loading
> > coil, and is its shield connected to the bottom of the coil/cap?  If
> that’s the case, you should be able to
> > bring it all to resonance with the meters you have.  I wouldn’t put an
> RF ammeter at the top end of the
> > loading coil, as it could really throw things off because of the high
> voltage there.  The antenna current
> > should be the same, regardless of whether it’s measured at the “cold” or
> “hot” ends of the coil.  Do you
> > have a means of measuring the transmitter final current?
> >
> > By comparison, here is how I resonated EAR’s antenna.  The loading coil
> has a built-in variometer for
> > adjusting resonance.  I put a current-transformer type RF ammeter on the
> ground end of the coil and
> > watched for a peak while I rotated the inner coil of the variometer.  To
> match the final to the loading
> > coil/variometer, I used a three turn link coil wound over the very
> bottom turns and moved it around
> > while watching for a dip in the final current.
> >
> > 73, J.B., VE3EAR
> >
> > LowFER Beacon "EAR"
> > 188.830 kHz. QRSS30
> > EN93dr
> >
> >
> >
> >
> >
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