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KB0TXC

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receiving question
« on: November 08, 2020, 08:54:15 AM »

Hi All,

I have a question for the collective wisdom of the forum readers... I soon will have two general coverage receivers, an  Icom R-71 that I have had for years and just had converted to 12 Volt operation as well as being recapped, and a soon to be acquired Low HF-150. I have a random length long wire antenna with a 9:1 balun that works reasonably well. It is possible to use one antenna for two different receivers at the same time? I am sure that I will need a matching network, but do not know where to start researching this idea. Thank you all in advance!

7s

Joe KB0TXC

NNNN
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W6MK

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Re: receiving question
« Reply #1 on: November 08, 2020, 10:25:07 AM »

Bonito makes an active RX signal splitter. Cost is about $300.
MFJ makes a passive splitter for about $20.

A switch will be simpler and cheaper.
« Last Edit: November 08, 2020, 10:29:40 AM by W6MK »
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K6AER

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Re: receiving question
« Reply #2 on: November 08, 2020, 10:47:50 AM »

A CATV spliter  ($3.00) will work fine.
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VA3VF

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Re: receiving question
« Reply #3 on: November 08, 2020, 12:29:39 PM »

I had some money burning holes in my pocket and got this one:

http://www.crosscountrywireless.net/multicoupler.htm
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KL7CW

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Re: receiving question
« Reply #4 on: November 08, 2020, 08:54:50 PM »

I was surprised my inexpensive CATV splitter from one of the box stores had significant port to port isolation in the VHF range.  I never did an exact measurement, and have no idea how much the port to port isolation is down at the I believe 5 MHz lower limit, but I would just try one.  The loss at VHF was close to the 3 dB you would expect, and some loss at SW frequencies is not usually a problem at all. Later, if really necessary, you can always upgrade to an active splitter or amp.  The splitters I have are 75 ohm, which will probably work fine with typical receivers.  You can get some screw on type F connectors at a box store. Most likely it will work fine below 5 MHz even with a bit more loss down there.   Rick  KL7CW
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N8YX

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Re: receiving question
« Reply #5 on: November 10, 2020, 08:17:22 AM »

Mini Circuits makes a 2-port, 50-ohm splitter (ZSC-2-4) that's good from 0.5 to roughly 30MHz and has very good port isolation. I have a couple which I use when running my IC-720A/R-70 or IC-751A/R-71 combos. They can be found on eBay for around $10, give or take.
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W6UV

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Re: receiving question
« Reply #6 on: November 13, 2020, 02:30:14 PM »

A passive splitter is going to result in a 3dB signal loss to each receiver. On HF, that's not usually much of an issue, so give it a try. If the 3dB loss makes a difference, you can turn on the rig's preamp (if it has one), or spring for an active splitter, which will be much more expensive.
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KM1H

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Re: receiving question
« Reply #7 on: November 22, 2020, 03:33:46 PM »

A passive splitter is going to result in a 3dB signal loss to each receiver. On HF, that's not usually much of an issue, so give it a try. If the 3dB loss makes a difference, you can turn on the rig's preamp (if it has one), or spring for an active splitter, which will be much more expensive.

Closer to 4dB when all losses considered. The CATV ones have more loss at low HF and less port to port isolation, coupling is mostly strays at those frequencies; take one apart and look!  I built my own in one of those boxes.                                                             
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