[TowerTalk] 9 circle PCB update and performance

[VE6WZ_Steve]

Here is an update on my new 9 circle combiner board, and some comments about performance, and the array in general.

First, I have already made a revision to the PCB.  The latest is Ver. 3.2.
However, this board change is very minor.  I have decided to omit RFC L10 that goes from the RF out F-connector ground to the PCB ground.
The reason for the change, is if you only have a ground rod connected to the combiner, or a poor ground return connected to the ground lug, there can be an increase in system noise.
If you already have my first Ver 3.1 board, then I recommend you just omit L10, although it will still work fine with it.  Make sure you have a good DC ground return back to the shack connected to the ground lug.

So far performance has been very good although without A-B testing I can’t say the new board performs any better than the old one.
Perhaps this is to be expected since nothing has changed except having the CMCs integrated onto the board.

However, I wanted to share my thoughts about this 9 circle array in general based on my experience over the last few years.
Specifically, I have had emails from folks talking about the low output of the array, and how it seems to be insensitive to the very weak signals.
My rural, hilltop QTH is a VERY low noise location.  I have found with the 9 circle array I absolutely require a pre-amp after the combiner, and when used with the K3s, I also need the rig pre-amp.
When using, the Flex radio, I require the post combiner pre-amp and the 16 dB Flex pre-amp as well.  Without the added rig pre-amps, indeed the array at my QTH will not copy the very weak ones.

The other question I get (a LOT) is how does the array compare to my Beverages?  I have 15 Beverage wires, all between 900' and 1000’ long.
I have 3 single wires, and 6 directions with broadside phased pairs spaced 400’.  My Beverage RX system is a mostly a no-compromise installation.

So, most of the time, the 9 circle will copy equally well to the single wire Beverages, and sometimes the phased pairs will copy better, but that is only noticeable on the very weak ones that are barley above the noise.

Maybe it is best to listen yourself to a few examples?
When I am QRV on 160m, I am ALWAYS, 100% of the time, listening in stereo diversity.  I have the Beverages in the left ear, and the 9 circle in the right ear.

The following links are sound recordings in stereo.  If you listen, wear  headphones (yes they are weak DX) and maybe take the left ear off, then the right ear to compare.
I think you will notice there is not a lot of difference between the Beverages and the 9C.

Here is a CQ from Andy DL8LAS yesterday Feb 10 (before the band blew up):
https://drive.google.com/file/d/140I-RFRvaeULD89sjjgyybthgy8k2gSF/view?usp=sharing <https://drive.google.com/file/d/140I-RFRvaeULD89sjjgyybthgy8k2gSF/view?usp=sharing>

And here is our QSO from yesterday.  The QSB was very deep so this might be a better comparison for the very weak signals:
https://drive.google.com/file/d/1ywINB81E9gc9RKkaAuqLDRPwHqBj94BV/view?usp=sharing <https://drive.google.com/file/d/1ywINB81E9gc9RKkaAuqLDRPwHqBj94BV/view?usp=sharing>

The above recording were using the new combiner board.

Here is a recording from Dec 9, 2021 of Andy’s signal with the old board.
This is a very good example of how stereo diversity can modulate between your ears depending on which RX antenna is peaking:
https://drive.google.com/file/d/1YGa7PihQ2dbxfpcbfN51zqfe9vv9A4r8/view?usp=sharing <https://drive.google.com/file/d/1YGa7PihQ2dbxfpcbfN51zqfe9vv9A4r8/view?usp=sharing>

My conclusion is that the 9 circle array AT MY QTH can keep up with the Beverages.  Indeed every location will be different.
Perhaps one of the biggest advantages of the 9C array, is it gives me 8 directions of a second RX system for DXing diversity, and for contest multi direction RX.

73, de steve ve6wz