[Antennaware] Antennaware Digest, Vol 117, Issue 1

Tue Feb 5 13:57:15 EST 2019

There are other products.
ARRL reviewed the Array Solutions RX-FEP  front end protector and found it
excellent.
https://www.arraysolutions.com/as-rxfep

Try it out if it doesn't do the job send it back for a refund. No kidding.
Jay, WX0B

Jay Terleski
Array Solutions
214 954 7140

On Tue, Feb 5, 2019 at 12:42 PM Joe via Antennaware <
antennaware at contesting.com> wrote:

> Thanks Brent
>
>
> -----Original Message-----
> From: Robert Scott <wr5o at icloud.com>
> To: k8mp <k8mp at aol.com>
> Cc: hwardsil <hwardsil at gmail.com>; antennaware <antennaware at contesting.com
> >
> Sent: Tue, Feb 5, 2019 12:58 pm
> Subject: Re: [Antennaware] Antennaware Digest, Vol 117, Issue 1
>
> There are products to protect your receiver that are available from DX
> Engineering however,depending on your radio,it might have the option to
> switch between antennas automatically.  The big issue is the passive
> coupling between the two. The transmit antenna is receiving noise and when
> coupled to the BOG will transfer this noise to it.  That being said you
> need at least a wavelength of separation to avoid this. I know that is not
> possible in most situations including mine so I live with it. The benefits
> of the beverage are still good even in this situation.  Here is my BOG on
> 160 last night.  This beverage is approximately an eighth of a wavelength
> separated from my inverted L and lays  across the street and into a
> neighbors yard when I have it deployed.
>
> Brent Scott
> WR5O
>
>
>
> > On Feb 5, 2019, at 9:45 AM, Joe via Antennaware <
> antennaware at contesting.com> wrote:
> >
> > Hey Ward, et al,
> > This is not related to the original topic but you mentioned BOG antennas
> and I have a question.Is installing a BOG near the ground system of an
> Inverted-L dangerous for a receiver? Separation between them would be about
> 1/8 wavelength, perhaps less, from the nearest radial.
> > In my situation, there would be radials and the BOG(s) in the same body
> of water. I have no clue how much RF current and voltage would be in there.
> > Thanks, Joe, K8MP
> >
> > -----Original Message-----
> > From: Ward Silver <hwardsil at gmail.com>
> > Cc: antennaware <antennaware at contesting.com>
> > Sent: Tue, Feb 5, 2019 09:57 AM
> > Subject: Re: [Antennaware] Antennaware Digest, Vol 117, Issue 1
> >
> >
> > I would suggest that you contact K9AY directly about the impedance
> mismatch
> > - k9ay at k9ay.com
> >
> > From my experience and in reviewing a lot of literature, unless the loop
> is
> > *really* small, preamplifier noise figure is not significant on the lower
> > HF and MF bands.  I suppose it might be an issue for desktop rotatable
> > loops or "Beverage on Ground".
> >
> > 73, Ward N0AX
> >
> > On Tue, Feb 5, 2019 at 5:43 AM Andrew Ikin <andrew.ikin at btopenworld.com>
> > wrote:
> >
> >> Hello Ward,
> >>
> >> I think I need to rephrase my email. What I am trying to say is, a small
> >> terminated antenna e.g. a Flag or a Waller Flag is noise limited by the
> >> termination resistor. This is because the resistor has a 3dB noise
> figure.
> >> The antenna loss or low radiation resistance doesn't matter so much as
> this
> >> loss can be made up with an LNA. The issue is made worse because most
> >> practical
> >> designs have the matching transformer z that is the same as the
> termination
> >> resistor. Now if we use amplifier with high input z of say 30k Ohms;
> using
> >> chemandy.com Return loss and mismatch loss calculator
> >> the resistor noise is miss-matched to the amp. by approx. 10dB.
> >>
> >> Thus the antenna noise floor should be lower. However, I am assuming
> that
> >> the LNA has negligible noise when terminated with the antenna. This
> could
> >> be
> >> a design issue to get the noise figure down to less that 0.5dB!!!
> >>
> >> The example I gave using a high z amp. with the K9AY suggests that
> there is
> >> no loss in gain by using increasing the input z.
> >>
> >> 73
> >>
> >> Andrew  G8LUG
> >>
> >> -----Original Message-----
> >> From: Ward Silver
> >> Sent: Monday, February 4, 2019 7:50 PM
> >> To: antennaware at contesting.com
> >> Subject: Re: [Antennaware] Antennaware Digest, Vol 117, Issue 1
> >>
> >> A flux-coupled transformer with separate windings provides galvanic
> >> isolation between the feed line shield's outer surface and the loop.
> >> Coupling from the loop to the feed line can upset the pattern and couple
> >> noise on the feed line into the antenna.
> >>
> >> It is also a good idea to add a choke of several thousand ohms on the
> feed
> >> line at the antenna to prevent common-mode current on the outside of the
> >> feed line shield from getting into the cable and becoming
> differential-mode
> >> signals.  Same concern at the receiving end although most receivers are
> >> well-shielded.
> >>
> >> 73, Ward N0AX
> >>
> >> On Mon, Feb 4, 2019 at 11:00 AM <antennaware-request at contesting.com>
> >> wrote:
> >>
> >>> Send Antennaware mailing list submissions to
> >>>        antennaware at contesting.com
> >>>
> >>> To subscribe or unsubscribe via the World Wide Web, visit
> >>>        http://lists.contesting.com/mailman/listinfo/antennaware
> >>> or, via email, send a message with subject or body 'help' to
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> >>>
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> >>>        antennaware-owner at contesting.com
> >>>
> >>> When replying, please edit your Subject line so it is more specific
> >>> than "Re: Contents of Antennaware digest..."
> >>>
> >>>
> >>> Today's Topics:
> >>>
> >>>    1. Fw: source impedance of resistor terminated antennas (Andrew
> Ikin)
> >>>
> >>>
> >>> ----------------------------------------------------------------------
> >>>
> >>> Message: 1
> >>> Date: Sun, 3 Feb 2019 23:04:32 -0000
> >>> From: "Andrew Ikin" <andrew.ikin at btopenworld.com>
> >>> To: <antennaware at contesting.com>
> >>> Subject: [Antennaware] Fw: source impedance of resistor terminated
> >>>        antennas
> >>> Message-ID: <2E4939776E6344ECB4242B584629630C at DESKTOPCPQEP29>
> >>> Content-Type: text/plain;      charset="UTF-8"
> >>>
> >>>
> >>>
> >>> From: Andrew Ikin
> >>> Sent: Sunday, February 3, 2019 10:38 PM
> >>> To: antennaware at contesting.com
> >>> Subject: source impedance of resistor terminated antennas
> >>>
> >>> Is there any reason why most resistor terminated antennas like the K9AY
> >>> and the Flag use a matching transformer to the Rx feed line that has
> the
> >>> same impedance as the termination resistance. The reason for the
> question
> >>> is, such antennas have a ideal match to the 3dB noise generated by the
> >>> termination resistor and this resistor has no radiation resistance.
> >> Hence,
> >>> for antennas like a small size Flag, the performance could be limited
> by
> >>> the resistor noise.
> >>>
> >>> However, if the antenna is connected to a high zin amp., then the
> >> resistor
> >>> noise should be reduced by the miss-match and if the amp. noise figure
> is
> >>> very low, then it may be possible improve the antenna performance?
> >>>
> >>> Winding the clock back 20 years I noticed that the K9AY  Rx matching
> >>> transformer could be replaced by a high zin  amp. with a voltage gain
> of
> >>> 11dB. The overall gain increase compared to using 9:1 z transformer was
> >>> 20dB. This increase in gain is what would be expected (11dB amp. plus
> 9dB
> >>> by replacing the 9:1 transformer). Thus, the antenna gain compared to
> one
> >>> without the amp. had not been degraded by using high zin amp.. However,
> >>> then I didn?t consider the effect of resistor noise, but this wouldn?t
> be
> >>> an issue with the K9AY.
> >>>
> >>> Is there something else I need to consider?
> >>>
> >>> 73
> >>>
> >>> Andrew Ikin
> >>> G8LUG
> >>>
> >>> ------------------------------
> >>>
> >>> Subject: Digest Footer
> >>>
> >>> _______________________________________________
> >>> Antennaware mailing list
> >>> Antennaware at contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/antennaware
> >>>
> >>>
> >>> ------------------------------
> >>>
> >>> End of Antennaware Digest, Vol 117, Issue 1
> >>> *******************************************
> >>>
> >> _______________________________________________
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> >>
> >>
> >>
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