(I've already posted this query at the Ham-Antennas group, but it occurs to me that many in this group have tackled the same "problem")

I have a remote receive only HF site with three antennas and three receivers, each with different capabilities.  I would like to be able to connect any antenna to any receiver as desired, via remote internet control.  Rather than spend several hundred dollars on remote hardware that is built to handle full transmit power, I am planning on using some simple inexpensive wifi relay boards that are available on Amazon.  The incoming feedline is ethernet twisted pair cable, so that means there will need to be at least two relays for each of the three antennas.

The wifi controlled 4 channel relay boards (each relay is SPDT) cost about $20....but I can't quite get my mind around how many of these 4 relay boards I would need to give me the ability to connect any one of the three antennas (with twisted pair feedline) to each of the three receivers.  It certainly is do-able, but it seems like I would need 8-12 total SPDT relays to accomplish that arrangement.  Any suggestions greatly appreciated.

Hi Bruce,
All relay boards I have tested (several years ago, I must say...) introduced Ethernet related noise, carriers, etc.
As there was NO hardware, which did not introduce additional interference; I stopped to use any relay or switch between antenna feedpoint and kiwisdr.
I use professional grade outdoor RG6/RG11 with specified connectors from German Cable TV supplier WISIve

I have only tested some consumer grade products available in Europe for switching via Ethernet networks.

Since then I have never tried again to switch kiwisdr antennas - instead I use one antenna per kiwi-rx - sorry for this report. May be todays products are better, than a few years ago...

Ulli, ON5KQ

Hi

Can you live with the 1:3 loss, 4,8 dB, from a splitter? Alternatively put a pre-amp first. If so you also has no switching at all.

Bo
www.rudius.net/oz2m :: www.rfzero.net

HI Bruce,
 I am using and Elad ASA-42 active splitter. Allows 4 antennas to two receivers.
Unfortunately, It is coax fed. Perhaps you could use twisted pair transformers to covert it back to coax at ant/and rx ends?

On Mon, Oct 17, 2022 at 10:56 AM, ON5KQ wrote:

Hi Bruce,
All relay boards I have tested (several years ago, I must say...) introduced Ethernet related noise, carriers, etc.
As there was NO hardware, which did not introduce additional interference; I stopped to use any relay or switch between antenna feedpoint and kiwisdr.
I use professional grade outdoor RG6/RG11 with specified connectors from German Cable TV supplier WISIve

Ulli,  thanks for the information, yes I do fear that any relay device has the possibility of introducing noise, so at this point I have ordered just one trial board, which I can use to switch between two antennas connected to one receiver, as a starting test.

But leaving noise concerns aside, my biggest challenge remains the wiring diagram to give full connection flexibility, so on a whim I can connect antenna "A" to receiver "3" etc etc.  The Elad active splitter Tom mentioned in a later post does sound intriguing, as long as put it downstream from the ethernet to coax transformer, and if it can be controlled via a local PC that I can access remotely.  Lastly, I hadn't though about splitting each antenna three ways first, followed by switching, which might simplify the wiring diagram.

Appreciate all the thoughts - back to my whiteboard now to continue diagramming things...

Hi Bruce,

You might want to review the use of relays in a WSPR receiver application.

"Receiving connection failures are common. This problem occurs because the relay operates in near-zero current and near-zero voltage contact operation. The real problem is a very thin film, usually just a few molecules thick, builds up on contacts". Source https://www.w8ji.com/relay_cleaning_and_life.htm.

In pure receiver applications, splitters with preamplifiers are a good way to go. However the best splitters and preamplifiers do introduce noise and losses, at least 3dB per split.
In the light of experience, I removed all receiver antenna switches from my remote controlled installation. Each separate antenna now remains connected to a separate receiver.

The receive relay problem is very different to transmitter relays because RF current is normally enough to punch through the thin insulating film.

73 John
VK4CT / VK4EMM

John,

I’m wondering, if cost were not a consideration, vacuum relays may offer resilience to ohmic losses due to relay contact corrosion.

Just a thought.

Bruce,

I think what you are after is a full 3x3 RF cross point switch for your receivers and antennas.

For only LF-HF it takes quite a few parts but I think you could build one from available SS switches such as

https://www.mouser.com/ProductDetail/MACOM/MASWSS0179TR-3000?qs=3Wmz%2FrCSAaGQmf%252BaN4qHBg%3D%3D

• Low Insertion Loss: <0.5 dB @ 900 MHz
  
• Low Power Consumption: <1.0 µA @ 3 VDC
• Very High Intercept Point: 52 dBm IP3
  
• Both Positive and Negative 3 to 8 V Control

at $1 per and perhaps 6 per twisted pair, parts would run you about $36 plus an Arduino or similar perhaps with some inverters and I/O expander to get enough control lines, so maybe $75 total parts but I think that should do it. If you use an Arduino IoT33 with WiFi or similar there are lots of libraries for driving peripherals. Maybe even more in the RPI world which has similar OBCs.

Don't you want a matrix like a hashtag/octothorpe "#"  but with 3 lines in V and H directions.  With 3 of these switches you can make 1X4 mux/demux and connect each of the mux'd connections to one line of the matrix. Common of one of the 3 goes to the rx/antenna it belongs to. From there its just a logic table to avoid multiple antennas or multiple receivers from piling on to a single matrix interconnection.

You'd want to be reasonable about layout but it's only HF and not very critical.  I suspect that you can get quite a bit of isolation without breaking too much of a sweat particularly if you lay it out on multlayer PCB material. You could probably even do a full 4x4 that way with a smart autorouter !

A number of manufacturers make them at competitive prices.   I've used these parts, they are generally nice little T/R switches for cell phones which have low IL even at UHF and some can handle 10W even though you don't intend to transmit. I use them in my Kiwi Frequency Extender to switch a 2 GHz preamp in/out (DPDT) but performance is quite good.

And if you are worried about isolation for a little more money and fewer discrete parts you can get 1x3 parts and even with terminations.

https://www.mouser.com/datasheet/2/249/MASW_008955-318421.pdf     $1.74 in singles!

https://www.mouser.com/datasheet/2/249/MASW_008955-318421.pdf $10 in singles

$60 instead of $36 for the terminated switches but easier to layout a PCB.

I screwed up two ways, at least.  I sent the non-terminated link twice rather than the terminated SP3T which I meant to be:

https://www.mouser.com/datasheet/2/609/HMC245AQS16E-2955868.pdf

However that part doesn't work anyway since you don't want anything terminated for this application, something else may need to be connected.

But doesn't this work for single ended/coax with the cheaper parts?

Glenn,

Wow, many thanks for assembling such detailed responses, and also for alerting to me to the existence of RF switches like that.  This seems like the best approach, especially given the relay contact issues mentioned by John VK4CT, which I hadn't thought about before.

Alas, my time near the remote site has nearly run out, so assembling the 3 X 3 matrix using RF switches will need to be one of my winter projects.  My brother occasionally visits the remote site during the winter/spring, so that will be my remote switching "hardware" until I can assemble everything.

Bruce

Hi Tom,

Solid state switches suggested by Glenn overcome problems with relays.

In my previous reference regarding relay contact problems, Tom W8JI goes further to say:
"The source of this contamination is well-documented. It comes either from environmental air quality in open frame relays, or from contaminates out-gassing from materials used inside sealed relays."

73, John

-- TAPR has a kit that uses 1x4 modules for receiver level switching. 
Craig, W6DRZ