The AM Forum

I remember seeing a diagram for connecting multiple receivers to one antenna without causing any interreaction among the receivers.  Does anyone have such a schematic or know the method for doing this?  I have several receivers connected to a single antenna and the sensitivity seems to be degraded.  Thanks! ???

I think you are referring to an active device known as a multicoupler.

Multicouplers provide isolation between N number of receivers, and some of these units include adjustable gain, from unity gain to X+ dB.

73,

Bruce

There are also passive multi-couplers, but they use resistors and inevitably, signal loss, but reduce interaction amongst the receivers.

Usually, there is excessive gain at the receiver, so the losses do not degrade s/n ration at any of the receivers.

If the background hiss (not counting local electrical noise or static crashes) increases when the antenna is connected, the receiver has all the signal it needs, and additional signal will not improve the s/n ratio.  That's why "preamps" are rarely effective on the 160, 80, 40 and even 20.

I use a passive splitter between the flex and the homebrew, and while signal levels drop a very small amount, I see no interaction or decrease in performance when using it.
Both receivers have way more gain than needed on the lower bands.
I have not tested it on the higher bands, but listen on 20 meters from time to time and don't notice problems there.
I would rather NOT have any active device to add noise, distortion or overload...

The splitter I have has one port marked dc block which I plug the flex into to prevent problems with static or whatever, the homebrew has a link input coil which looks like a DC short.
The splitter is marked .5 to 300 MHz I think, maybe something for an O scope?

Brett

Here is a manufacturer that specializes in this type of thing.

http://www.stridsberg.com/prod01.htm (http://www.stridsberg.com/prod01.htm)

It's a bit expensive but it looks like they know what's going on. You can put a watch on eBay for an HF multicoupler or multicontroller as they are sometimes called.

Jim Garland/W8ZR sold a limited run of kits to build your own and it was featured in the May 2004 QST. I built one and it's a treasure in the shack. Read more at

http://www.miami.muohio.edu/president/personal/w8zr/multicontroller/index.htm (http://www.miami.muohio.edu/president/personal/w8zr/multicontroller/index.htm)

I tried splitters and they didn't work for me at all. Even adding receiver preamps didn't fix things.

Minicircuits.com has an extensive line of passive splitters. If you only need to split 2 or 4 ways a passive splitter may be all you need. A two way splitter will have a loss of 3 db to each port (plus a small additional loss of a few tenths of a db) and offer good isolation between receivers. Here's an example of a two way 50 ohm splitter:

http://www.minicircuits.com/pdfs/ZSC-2-1+.pdf

On the lower bands the loss is negligible to split 2 or 4 ways.

You can add another pair of 1:2 splitters on each output of the first to make a 1:4. You lose a bit over 3 dB each time you add a 1:2 splitter. They are fairly easy to build. A BB transformer and a resistor or 2 depending on th econfiguration. I run a 1:4 most of the time on 160 and 75. The extra 7 or 8 dB of loss is not a problem.

Have not tried any of the splitters,  but ...

Some here have mentioned (and are implying now,  I think)  that CATV/FM splitters made for F connectors work fine from 2ish Mhz to low Ghz range.  Think that performance on 160M  should be fine based upon what has been noted.

They are dirt cheap and worth a try.  Many of us have some CATV units laying around in a drawer somewhere.  They are easy to make as well,  and a fun project ... always liked sewing,  errr winding very small toroids can be fun.  Think the Minicircuits jobs are inexpensive.        GL       Vic

Its a crapshoot with CATV splitters at least plotting them on a VNA. Some fall apart at 10 mHz and others have no directivity left at 5 mHz. The poor directivity may affect receiver performance.

The ARRL HB had a nice one, at least in the 80's, which I built using FT50 size ferrite toroids. A passive splitter will become a  combiner when reversed so its easy to build combinations for multiple Beverages (or any 50-75 Ohm antenna) to multiple receivers.


I have 7 Beverages and select those with toggle switches into an 8 port combiner all remoted 700' away and DIP relay selected. In the house the feed goes into a BCB HPF that can be bypassed with a DPDT toggle switch. That feeds a 11 dB gain, 1.5 dB NF broadband preamp (Norton lossless feedback circuit with a 2N5109) to a 4 way splitter for up to 4 radios. It still works well when 2 Beverages are selected as a pseudo vee beam or to cover rapidly changing azimuth angles as often happens on 160. The preamp is basically overload proof after years of contests and pileups attest and establishes close to unity gain while providing a low NF as I use it up to 20M at times when snow static wipes out the yagis. It also helps even on 160 when the noise is so low it defies logic.

Carl

We use the Raven boxes at work both in our antenna farm on the roof and in several systems that we ship.

http://www.multicoupler.com/

Mike WU2D

I use three receivers off Mini-Circuit splitters. No problemo.

I use both HB and Mini circuits with success. CATV splitters may not have enough inductance to work well at the low end of the HF band. I would think they would work ok but the port to port isolation would go away.

Gee! <slumps shoulders> I feel so inadequate now!
I've never had any splitters running here at all!!
And I don't have any Beveridges strung out on compass points either!!

Whaaaaaaaaa!! :-[   :'(

                     _-_-bear

Depends largely on the receivers being connected.  The problem is, in addition to impedance matching (important for modern receivers using bandpass filters and up-conversion) is suck-out.   The latter problem is evident when you have, say a HRO-50 and a AR-88 (both having front ends with multiple tuned circuits) hooked to the same antenna.  The front end in one, depending on where it's tuned, can suck out the signal on the other.  In that case you might need an active multicoupler which provides better isolation than just the passive splitter.

For modern receivers a passive multicoupler should work FBOM.

Any decent splitter should provide 30dB+ port to port isolation which will be invisible to any receiver. This is where CATV splitters fall apart real bad.

The system I described in a post above has no interaction between any boatanchor or modern ricebox. It is used most often with a TS-940 and 75A4 and the remaining ports feed a 75A3, HRO-60, NC-183D, NBS-1, SX-101A, SX-115, or whatever other radio is selected at those positions as I cycle several thru to keep them somewhat dried out.

Yep, its nice to have room for Beverages but loops, ewes, K9AY's, flags, mini 4 squares or whatever can be used on small lots. One ham I know is on a 100 x 100' lot and erected some wooden fencing on the sides and rear. Each section has a full wave of wire for 160 strung back and forth and terminated in a resistor and ground rod. This gives him 3 directions and they actually show some decent directivity.

Carl

Dunno, Carl, I used a HB resistive splitter that really had suckout problems.  Depends on the design of the passive splitter, I guess.

could be some receivers are not close to a 50 ohm input.
Splitter gets confused if the loads are not matched. I bet a 3 or 6 dB pad would balance things. A low gain high reverse isolation amp on each port would also help.

I dont mean a resistive splitter, they suck all around ;D

Carl

I built one of these also.  All the BA receivers in the shack connect through it.  Great box.

I also have a 112A Multicoupler from I.C.E.  Relatively inexpensive, works, although there isn't much information on specs (e.g, IMD) other than port isolation of 20dB.

Yeah Grant the W8ZR multicoupler is a nice box. The things that set it apart are the low noise video distribution amps and a switchable +12 dB gass fet preamp. Overload protection and up to 8 receivers, 7 of which provided with a normally open or normally closed (selectable) mute switch. Plus 50 ohm or high-Z antenna inputs.

I kinda think he only scratched the surface of interest in those kits. I think if somebody was able to get the artwork for the boards and case and the rights to put it back on the market as a kit it would sell.

Mike

If the ICs were readily available, I would like to build one as well. You could easily expand the string of chips to do as many receivers as you would like. But, I haven't been able to find the ICs at the usual places (Mouser, Digikey and Newark) either as socket or surface mount. I think they have been discontinued.

I would like to be corrected on the discontinued part if any one knows of a source.

Bill

A splitter is a passive device

Hi Bill,

I can help. I had my SMUG Flex in the multicoupler path at one time and with the TX/RX sequencing everything was fine however, I had to do a SMUG calibration with new software and forgot to take the Flex out of line. I fired 6 or so watts of RF into the multicoupler and let the smoke out of a 51 ohm resistor and one of the Maxim video distribution amps.

It was late 2008 at the time and after searching every parts house I could find I contacted Jim Garland. He didn't have any chips left and told me to contact the manufacturer. I did and found out the chip had been discontinued BUT an exact replacement, ROHAS compliant, chip was available. That part number is MAX497CPE. Contact Maxim here and good luck.

http://www.maxim-ic.com/products.cfm (http://www.maxim-ic.com/products.cfm)

Mike

Thanks Mike! I search for that one and see what I find.

Bill

bull shit

Is that something like bovine effulent Frank ;D  Man, you been on a tear lately, that Emtron thread must have you at an all time peak :o

Yep, there is nothing wrong with a splitter and active devices. The problem is the person building them without a clue.  A microwave circulator at HF....Jeez thats a new one for the Darwin award.

Carl

Carl,
You should see the sign the XYL gave me for Christmas.
Man I would love to see an HF circulator.  I wonder if it would fit in the shack.
We need a new thread. Gary could call it the most stupid advice thread.

I see, kind of like a "key hole bird"


Mr Mike, I forgot that word you taught me Saturday

no thanks my method works fine and has plenty of port to port isolation
I bet that charge pump does a number on th enoise floor

How did we get from someone whining about active devices to a 3 device noise source?

In the real world, unless you are using some POS radio without a tuned RF stage or a regen, then port to port isolation of a ferite toroid splitter will give 30-50dB of isolation. Ive yet to find a spur from any radio connected to my simple passive splitters pass thru to another radio.

Carl

Filter? Show me a filter that can remove the noise from your circulator but allow signals of interest through. Such a filter would make you a rich man. Despite your claims, deferring to magic is not making your case.

That circulator isnt the only noise source here ;D

Carl

elmer material

 " I don’t remember when the FCC started cracking down on what those levels could be, but many of the old tube receivers would never pass FCC type certification today. "

Its to stop them ruskies from finding us.

klc

When you stopped using the Ocean Hopper regen and upgraded to a S-38/SW-54 ::)


German subs could detect ships using regens and poor reverse isolation RF stage superhets. Adding a 2nd RF stage to several existing sets or adding shielding eliminated the problem, the National RAO is a good example of the added RF stage. Using a good splitter does the same if not better. A resistive splitter doesnt hack it, you need a Wilkinson style device as then the out of phase signal from the other port(s) is dumped in the terminating resistor. Same concept as used in the 4 Square vertical arrays.

Carl