Hi Mark,
I modeled your antenna last night, and have some comments.
There is almost as much reactance as resistance at the feedpoint of your
EWE based on your dimensions and termination resistor, but sounds like
that's typical (per the ON4UN low band DXing book). The back null is also
not as deep compared with Pennants and Flags that I work with.
Nevertheless the RDF value of your design is not much different than the
Pennants and Flags I work with.
I use 3 very small pennants on 160 meters, and their signal to noise ratio
is never worse than my 68 foot base loaded TX vertical (so you have a
reference point regarding what I would expect from your EWE, as Pennants
are considered to be part of the EWE family and they have similar RDF
values). During every QSO I make on 160 meters (as well as casual
listening) I compare signal to noise performance between my TX vertical and
my pennants, and the pennants have never lost (your situation might be
slightly different due to the horizontal section of your Inv-L, but more
times than not when working DX I would be surprised if a properly working
EWE type RX antenna was not equal or slightly better than your Inv-L).
I wonder why you went with a classical EWE versus a Flag or Pennant The
Flag and Pennant are ground independent (no connection to ground), which is
a very nice feature and makes them very easy to construct as well as easy
to rotate in the direction you desire. The Pennant is nice because you can
drop the feedline directly to ground from the feedpoint. Something else I
like about Pennants or Flags is the fact that their feedpoint impedance is
almost pure resistive when using a termination resistor that provides a
nice pattern (deep null off the back) with peak RDF performance.
I am not suggesting you abandon your classical EWE design, but I did want
to share some off the cuff comments which may or may not help you down the
road.
Here is a test I would recommend (typically I would do this during the
middle of the day when there is no skywave). Connect a 50 ohm dummy load
to your preamp in place of your EWE and its feedline, and tell us what your
S meter reading is, and then connect your EWE with its feedline to the
preamp and tell us what your S meter reading is. Hopefully the S meter
reading is much higher with the EWE versus the dummy load. If you can
repeat this same test but with the dummy load out at the EWE feedpoint
(disconnect the EWE from the end of the feedline and connect the 50 ohm
dummy load in its place), as this might also shed some light regarding your
situation.
I should also mention that I would not expect a Hugh improvement in Signal
to Noise ratio when using a EWE to work DX compared with a Vertical if the
Noise is arriving equally from all directions (versus a point source
noise). Based on my experience I only achieve 1 or 2 dB of improvement in
Signal to Noise for stations 4000 miles or more away as an example (but
this can often be the difference between a solid QSO and no QSO at all on
160 meters).
I do have Toroid Chokes installed on my pennant feedline (per the K9YC
design) to help with common mode noise, and in my installation I have never
observed common mode noise issues (I have run tests with my HF rig and
pre-amp right at the feedpoint of my pennants and operated them with a
battery to see if the noise level was much less than in the shack, and
thankfully it is not).
As others have said you may be experiencing pattern distortion which I have
not addressed above. For starters I would float your inverted L at it's
feedpoint to see what happens to your noise level, and I would also connect
it direct to ground at it's feedpoint to see what happens to your noise
level and I would do all of this while also listening to AM radio stations
as high up in the AM broadcast band as possible during the middle of the
day. I would do this listening to AM radio stations that are at various
headings from your location to see if you can detect pattern distortion on
any of them depending on the configuration of your inverted L (grounded
versus floating). If the AM radio station signals change when listening on
the EWE when changing the configuration of your inverted L (grounded versus
floating), then this might provide a clue regarding the need to detune the
inverted L when receiving on the EWE, etc.
Just some long winded thoughts from my end.
73, and Happy New Year.
Don (wd8dsb)
On Thu, Dec 31, 2015 at 10:32 AM, Mark K3MSB <mark.k3msb@gmail.com> wrote:
> Good Morning!
>
>
> Last night was the second night in a row with nice conditions between the
> east coast and Europe on 160M. I took the time to get a cup of coffee
> and spend a few hours comparing the Inverted-L and EWE, and recording my
> observations.
>
>
> All Inverted-L data was recorded with the Icom on-board preamps OFF.
>
>
> All EWE data was recorded with the 20 dB external preamp ON.
>
>
> The external preamp is an Advanced Research Receiver P1-30/20VD
>
>
> The EWE is pointed roughly 40 degrees, and the grounds are not connected
> via wire. That means the transformer end is towards Europe, and the
> resistor end is towards California -- some of you asked for clarification.
>
>
> General Noise Floor:
>
> INV-L: S2-S3 spikes above S5
>
> EWE: S4 steady, no spikes (Higher than the INV-L !!!!!)
>
>
>
> Forward reception:
>
> In the following table, (S1, S2) means S1 on the INV-L, S2 on the EWE.
>
> SP5GRM (S7, S7)
>
> OK2RJC (S9 , S6)
>
> RA2FV (S6, S4)
>
> RN3CT (S7, S4)
>
> EU3AR (S5, Below noise level)
>
> UT7NY (S5, S4)
>
> EI4KF (S5, S4)
>
> YO9HP (S5, S5)
>
> UY0ZG (S5, S4)
>
>
> Those stations that were S4 on the EWE were pretty much riding the noise
> level and I could hear them, but they were much stronger (and easily
> copied) on the INV-L!
>
>
> Conclusions (perhaps incorrect…..)
>
> A) The noise floor of the EWE can be higher than that of the INV-L.
>
> B) The EWE is NOT suitable for weak signal reception
>
>
> If A and B above are correct, what’s the point of using an EWE?
>
>
> I state my conclusions based upon my observations, knowing full well a lot
> of you successfully use the EWE antenna, so I still need to learn more, do
> more tweaking, etc.
>
>
>
> Back Rejection: I recorded some stations that should have been off the
> back of the EWE (or thereabouts….. I didn’t check them on QRZ.com, but
> just
> assumed 8,9 and 7 land stations were behind me…..)
>
> N8 (S9+10 , S7)
>
> N7: (S7, S4)
>
> N8 (S9+10, S9+10)
>
> N9 (S9, S7)
>
> N8 (S9+10, S8)
>
> N8 (S9+20, S9)
>
>
> So, I am seeing rejection off the back of the EWE. It doesn’t happen all
> the time, but as I said I didn’t do a search to see where each station was
> actually located.
>
>
> Some of you asked how I know my cable and transformer are good. I attached
> the feedline to the transformer, then used a resistance substitution box
> to put a load on the other end of the transformer. A 470 ohms resistance
> provided an SWR of 1.1. As I moved the resistance above and below 470,
> the SWR moved as expected. Since the transformer is 9:1, I felt this
> showed the coax and transformer were OKI.
>
>
> Comments welcome.
>
>
> 73 Mark K3MSB
> _________________
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