Topband: Polarization on 160m
herbert.schoenbohm at gmail.com
Wed Nov 28 14:41:08 EST 2018
So is the 70-year-old Collins 74A4 with its mechanic filters and single
conversion method. Many times you could just roll the IX into a deep hole
with the bandpass control and the signal would pop out of nowhere. Wish I
still had mine to run comparisons. I have now a modern (expensive) Flex
6600M that allows true dual diversity with 2 RX antennas with separate RX
audio in each ear. I will try it out in the ARRL 160 contest although the
ARRL has the VI as non-DX which is always has been a real bummer.
Herb Schoneobhm, KV4FZ
On Wed, Nov 28, 2018 at 1:13 PM Yuri Blanarovich <k3bu at optimum.net> wrote:
> Speaking of "two ears"
> Going back to using two Drake R4B receivers, two antennas, one on each
> ear, there would be times when "two ears" heard the signal, while
> switching to each other there would be nil. I think that was some DSP
> going on in the head.
> BTW Drake R4B is still one of the best receivers for weak signals
> reception, no crystal filters in the path to fuzzy the signals. LC in IF
> chain. DSRs are now very close.
> Yuri, K3BU
> On Wed, Nov 28, 2018 at 12:04 PM, Tree wrote:
> > WIll add my two cents to this discussion.
> > One thing I have experience with is diversity reception both on 160
> > and 80
> > meters. Often - I would be using my TX antenna in one ear and a
> > beverage
> > in another. On 80 meters, the TX antenna was a 4 square. On 160,
> > either a
> > vertical or two element phased array.
> > I found on 80 meters - when running JAs in a contest - if I only used
> > one
> > antenna - I would almost always miss one letter of the JA's callsign
> > and
> > have to ask for a repeat... but with diversity - the signal would
> > float
> > around in my head and I could almost always get the whole call the
> > first
> > time.
> > I can hear this effect on 160 as well as signals float around. I
> > can't
> > prove this is just polarization - as it could be different angles of
> > signal
> > arrival - but it sure re-enforces the point that having different
> > kinds of
> > RX antennas for different situations is never a bad thing.
> > I have experienced some sunrise openings where a low dipole has worked
> > well. There are times when my directive receive antennas seem to be
> > broken
> > - which is another indication of high angles.
> > Tree N6TR
> > On Wed, Nov 28, 2018 at 8:51 AM Yuri Blanarovich wrote:
> >> Not knowing about "gyros", but when operating and having vertical and
> >> horizontal antennas available, I remember times when QSB was
> >> happening
> >> on one antenna, switching to the "other" polarization antenna would
> >> bring the signals up.
> >> My conclusion was that at the times the signal's polarization was
> >> rolling around, especially when far DX.
> >> Yuri, K3BU, VE3BMV, VE1BY
> >> On Wed, Nov 28, 2018 at 09:22 AM, Robert Parkes via Topband wrote:
> >>> Polarization on 160m
> >>> Interesting discussion and one I suspect we wish could fully
> >>> comprehend !
> >>> When the wave front meets the ionosphere and the wave splits the
> >>> critical frequency is different for the two waves, commonly known as
> >>> foc and fxc.
> >>> This difference (from memory) is half the gyrofrequency and can
> >>> often
> >>> be seen on Ionosonde plots with two sets of reflections. The gyro
> >>> frequency depends on the strength of the magnetic field at that
> >>> point
> >>> of the ionosphere so can vary from 700kHz to 1.4MHz where the
> >>> radiated
> >>> wave interacts with the Ionosphere Layer be it, E layer or F layer.
> >>> Being radio amateurs and pushing the envelope we are trying to make
> >>> that illusive QSO so we need to excite a propagation path which is
> >>> normally at the limit in order to chase the DX.
> >>> Assuming conditions are favourable, and if the angle of arrival and
> >>> critical frequency is such that it favours both wave fronts then for
> >>> a
> >>> single and multi-hop transmission both the O-wave and the X-wave
> >>> will
> >>> be propagated.
> >>> The higher frequency of the two wave fronts, the X-wave may
> >>> propagate
> >>> which could result in a QSO whilst those around us may not have
> >>> quite
> >>> the same favourable conditions and only the O-wave is propagated on
> >>> a
> >>> differeing path while the X-Wavecould fall by the wayside and not be
> >>> propagated.
> >>> One result of all this variability could result in what has been
> >>> called spotlight or torchlight propagation. I recall Eric K3NA
> >>> giving
> >>> a talk along these lines when referring to 3B7C 160m operations and
> >>> how that spotlight moved across North America during the course of
> >>> his
> >>> opening to the US.
> >>> There is a possibility that Circular Polarisation would assist
> >>> with both the O and X wave modes of propagation and it could be
> >>> argued
> >>> that a "compromise" Inv-L antenna provides this with its Vertical
> >>> and
> >>> Horizontal elements making up the antenna and resulting mixed
> >>> polarisation.After all a number of amateurs have had good success
> >>> with
> >>> an Inv-L.
> >>> 73sBob ParkesG3REP(ex - S21YP, 4S7RPG, A45XF, VS5RP, P29PR)
> >>> _________________
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> >>> Reflector
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