Antenna switches
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Off topic. Sorry. What are the functional disadvantages that make it
apparently undesirable to build an antenna switch that is a crossover 2 radios x 2 antennas? What if you only used one path at a time but could switch them easily? Crosstalk? Is it so strong as to damage the other radio? Is it not possible to achieve acceptable compatibility with 2 radios and 2 antennas? Or to swap amplifiers between two radios and two antennas by placing one on the input and another on the output of the amplifiers? Or to swap in the better antenna for a short contact that you just can't seem to make on the current one? I don't relish placing a switch on each antenna and another switch on every radio in order to connect anything to anything. How do you do it? It would take 4 1x2 switches on the input of the amplifiers and 4 more on the output to do what could be done with 2 switches of 2x2. Thanks, Jim KG0KP ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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Jim,
The most important factor when talking about connecting multiple transceivers to antennas is isolation. The real question is just how much RF energy will leak back into the non-transmit transceiver. Yes, there is the possibility of damage to the receiving circuits and T/R switch of the receive transceive that is just supposed to be listening if it gets too much RF at its receive input. That is what the real discussion is all about. The amount of isolation required in the switch depends on the power level. If you are talking about 100 watts power from the transmitter, 40 dB isolation is likely OK, but at higher powers, you will need more isolation. 73, Don W3FPR On 1/2/2017 9:53 PM, Jim Miller wrote: > Off topic. Sorry. What are the functional disadvantages that make it > apparently undesirable to build an antenna switch that is a crossover 2 > radios x 2 antennas? What if you only used one path at a time but could > switch them easily? Crosstalk? Is it so strong as to damage the other > radio? Is it not possible to achieve acceptable compatibility with 2 radios > and 2 antennas? Or to swap amplifiers between two radios and two antennas > by placing one on the input and another on the output of the amplifiers? Or > to swap in the better antenna for a short contact that you just can't seem > to make on the current one? ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I agree, isolation is the most important factor for antenna switches. However, I wouldn’t use a switch unless it had at least 60dB of isolation in the HF band, even with Tx power of 100-watts.
73, Bob Nobis [hidden email] > On Jan 2, 2017, at 20:23, Don Wilhelm <[hidden email]> wrote: > > Jim, > > The most important factor when talking about connecting multiple transceivers to antennas is isolation. > The real question is just how much RF energy will leak back into the non-transmit transceiver. > Yes, there is the possibility of damage to the receiving circuits and T/R switch of the receive transceive that is just supposed to be listening if it gets too much RF at its receive input. > > That is what the real discussion is all about. The amount of isolation required in the switch depends on the power level. If you are talking about 100 watts power from the transmitter, 40 dB isolation is likely OK, but at higher powers, you will need more isolation. > > 73, > Don W3FPR > > On 1/2/2017 9:53 PM, Jim Miller wrote: >> Off topic. Sorry. What are the functional disadvantages that make it >> apparently undesirable to build an antenna switch that is a crossover 2 >> radios x 2 antennas? What if you only used one path at a time but could >> switch them easily? Crosstalk? Is it so strong as to damage the other >> radio? Is it not possible to achieve acceptable compatibility with 2 radios >> and 2 antennas? Or to swap amplifiers between two radios and two antennas >> by placing one on the input and another on the output of the amplifiers? Or >> to swap in the better antenna for a short contact that you just can't seem >> to make on the current one? > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Don Wilhelm
Let's add some real numbers.
I have a mechanical A/B switch DIAWA Model CS-201. Fairly inexpensive. Internally, it has a cavity design to provide isolation between the ports. Using an HP signal generator and an HP-3586C selective level meter the isolation of the switch was measured. The used port was terminated in a 50 ohm dummy load. The "open" port went into the selective level meter which had a input Z of 50 ohms. The HP-3586C can measure RF power levels accurately within a few tenths of a dBm. Differences are at least as accurate. Here are some numbers: 160M/80M 80 dB isolation 20M 69 dB isolation 10M 60 dB isolation 6M (by extrapolation) 46 dB. YMMV Note the frequency dependence. This switch provides the 40 dB isolation necessary. I have no connection with DIAWA but was interested in this topic. I suspect there is some real junk out there. Obtaining 60+ dB isolation isn't easy. The slide switch "designs" described by some are likely in that junk category. If in doubt measure. You have two rigs and an S meter. Input .1 or 1 watt to the switch terminated as above and look at the S meter for the rig on the open port. Scale the results to 100 W. If it shows S9+80 dB or less, you are likely OK. Keep in mind many S meters are horribly inaccurate. They tend to be too generous at around S9. Not knowing could be expensive. 73 de Brian/K3KO P.S. In the past, I did the same measurements with coax relays. My recollection: Obtaining 40 dB isolation at 10M was not possible with some of them. Their internal design was not as good from an isolation standpoint. Lower power coax relays provided better isolation (smaller contact size?) than high power relays. So be careful with coax relays. On 1/3/2017 3:23 AM, Don Wilhelm wrote: > Jim, > > The most important factor when talking about connecting multiple > transceivers to antennas is isolation. > The real question is just how much RF energy will leak back into the > non-transmit transceiver. > Yes, there is the possibility of damage to the receiving circuits and > T/R switch of the receive transceive that is just supposed to be > listening if it gets too much RF at its receive input. > > That is what the real discussion is all about. The amount of isolation > required in the switch depends on the power level. If you are talking > about 100 watts power from the transmitter, >40 dB isolation is likely > OK, but at higher powers, you will need more isolation. > > 73, > Don W3FPR > > On 1/2/2017 9:53 PM, Jim Miller wrote: >> Off topic. Sorry. What are the functional disadvantages that make it >> apparently undesirable to build an antenna switch that is a crossover 2 >> radios x 2 antennas? What if you only used one path at a time but could >> switch them easily? Crosstalk? Is it so strong as to damage the other >> radio? Is it not possible to achieve acceptable compatibility with 2 >> radios >> and 2 antennas? Or to swap amplifiers between two radios and two >> antennas >> by placing one on the input and another on the output of the >> amplifiers? Or >> to swap in the better antenna for a short contact that you just can't >> seem >> to make on the current one? > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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That switch is rated at 2500W PEP but only 1000W CW. Has anyone used them
at 1500W CW or RTTY? 73, Jim N7US -----Original Message----- Let's add some real numbers. I have a mechanical A/B switch DIAWA Model CS-201. Fairly inexpensive. Internally, it has a cavity design to provide isolation between the ports. Using an HP signal generator and an HP-3586C selective level meter the isolation of the switch was measured. The used port was terminated in a 50 ohm dummy load. The "open" port went into the selective level meter which had a input Z of 50 ohms. The HP-3586C can measure RF power levels accurately within a few tenths of a dBm. Differences are at least as accurate. Here are some numbers: 160M/80M 80 dB isolation 20M 69 dB isolation 10M 60 dB isolation 6M (by extrapolation) 46 dB. YMMV Note the frequency dependence. This switch provides the 40 dB isolation necessary. I have no connection with DIAWA but was interested in this topic. I suspect there is some real junk out there. Obtaining 60+ dB isolation isn't easy. The slide switch "designs" described by some are likely in that junk category. If in doubt measure. You have two rigs and an S meter. Input .1 or 1 watt to the switch terminated as above and look at the S meter for the rig on the open port. Scale the results to 100 W. If it shows S9+80 dB or less, you are likely OK. Keep in mind many S meters are horribly inaccurate. They tend to be too generous at around S9. Not knowing could be expensive. 73 de Brian/K3KO ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Don Wilhelm
I use Diamond Antenna Switches originally purchased in Japan with good results.
See http://www.diamond-ant.co.jp/english/amateur/equipment/equipment5_swi.html <http://www.diamondantenna.net/cx210a.html>. The claimed isolation up to 200MHz for the two-port CX210A switch is 70dB. I have not actually measured the ones I have. These are available form DX Engineering for about $50.00 Oh, I do not have any connection with either Diamond Antennas or DX Engineering. Bob Nobis [hidden email] > On Jan 2, 2017, at 20:23, Don Wilhelm <[hidden email]> wrote: > > Jim, > > The most important factor when talking about connecting multiple transceivers to antennas is isolation. > The real question is just how much RF energy will leak back into the non-transmit transceiver. > Yes, there is the possibility of damage to the receiving circuits and T/R switch of the receive transceive that is just supposed to be listening if it gets too much RF at its receive input. > > That is what the real discussion is all about. The amount of isolation required in the switch depends on the power level. If you are talking about 100 watts power from the transmitter, 40 dB isolation is likely OK, but at higher powers, you will need more isolation. > > 73, > Don W3FPR > > On 1/2/2017 9:53 PM, Jim Miller wrote: >> Off topic. Sorry. What are the functional disadvantages that make it >> apparently undesirable to build an antenna switch that is a crossover 2 >> radios x 2 antennas? What if you only used one path at a time but could >> switch them easily? Crosstalk? Is it so strong as to damage the other >> radio? Is it not possible to achieve acceptable compatibility with 2 radios >> and 2 antennas? Or to swap amplifiers between two radios and two antennas >> by placing one on the input and another on the output of the amplifiers? Or >> to swap in the better antenna for a short contact that you just can't seem >> to make on the current one? > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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