Transmitting while listening in diversity mode
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Transmitting while listening in diversity mode
 
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Nobody commented on my question last night, but I'd still like to hear from
your collective wisdom, so here's a repeat: I set up my sub-rx to listen on transmit antenna B while the main is listening and transmitting on A, and to listen on A while main is listening and transmitting on B. This allows for diversity reception. "...here's my question: My two antennas are located so each is in the other's null, but they are not far apart, maybe 50 feet at most. When I transmit, I don't hear any carrier-operated relays or see any adverse reactions, but I'm still not sure that it's okay. The manual sez "well isolated," but what I'm looking for is some objective way to test or measure. Can anyone tell me how I can establish for sure that I can, or cannot, transmit on A when the sub is connected to B, and vice versa? " Any info (especially first-hand knowledge) would be much appreciated. 73, Tony KT0NY ______________________________________________________________ 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 |
Re: Transmitting while listening in diversity mode
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Tony,
The SubRX is protected by a COR in all cases, so if you do not hear the COR relay kick in, you are probably OK. If the two antennas are located in each other's null, then you may have the "best of all worlds" situation regardless of the physical separation. There is more to "isolation" than physical separation. 73, Don W3FPR On 1/6/2011 7:27 PM, Tony Estep wrote: > Nobody commented on my question last night, but I'd still like to hear from > your collective wisdom, so here's a repeat: I set up my sub-rx to listen on > transmit antenna B while the main is listening and transmitting on A, and to > listen on A while main is listening and transmitting on B. This allows for > diversity reception. > > "...here's my question: My two antennas are located so each is in the > other's null, but they are not far apart, maybe 50 feet at most. When I > transmit, I don't hear any carrier-operated relays or see any adverse > reactions, but I'm still not sure that it's okay. The manual sez "well > isolated," but what I'm looking for is some objective way to test or > measure. Can anyone tell me how I can establish for sure that I can, or > cannot, transmit on A when the sub is connected to B, and vice versa? " > > Any info (especially first-hand knowledge) would be much appreciated. > > 73, > Tony KT0NY > ______________________________________________________________ > 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 > 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 |
Re: Transmitting while listening in diversity mode
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Thanks, Don.
The nulls of my antennas are not very deep, but I guess it's sufficient. The antennas are just rudimentary wire arrays strung up in the back-yard trees. My previous wire-in-a-tree setup was described in Mar 2006 QST. Then we moved to this QTH, and I had to rethink it. This setup is better than what's depicted in that article, but still not great. The directivity one can achieve this way is limited, obviously. Still, I hear no COR clicking, and all seems well, and it is fun to play with diversity reception. In certain cases it really makes a big difference. 73, Tony KT0NY On Thu, Jan 6, 2011 at 6:47 PM, Don Wilhelm <[hidden email]> wrote: > ....If the two antennas are located in each other's null, then you may > have the "best of all worlds" situation... ______________________________________________________________ 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 |
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In reply to this post by Tony Estep
Tony Estep wrote:
>Nobody commented on my question last night, but I'd still like to hear from >your collective wisdom, so here's a repeat: I set up my sub-rx to listen on >transmit antenna B while the main is listening and transmitting on A, and to >listen on A while main is listening and transmitting on B. This allows for >diversity reception. > >"...here's my question: My two antennas are located so each is in the >other's null, but they are not far apart, maybe 50 feet at most. When I >transmit, I don't hear any carrier-operated relays or see any adverse >reactions, but I'm still not sure that it's okay. The manual sez "well >isolated," but what I'm looking for is some objective way to test or >measure. Can anyone tell me how I can establish for sure that I can, or >cannot, transmit on A when the sub is connected to B, and vice versa? " > >Any info (especially first-hand knowledge) would be much appreciated. Connect a simple diode milliwattmeter to the feed from the RX antenna. All it needs is a 47 ohm resistor, a 1N914/4148 diode, a .01uF ceramic cap and your DVM. (This is truly a "Construction 101" project - can anyone supply a suitable web reference, please?) Gently ramp up the power to the TX antenna, and see how much power is coming back on the RX input. Repeat with every combination of bands and antennas. Also read "Managing Interstation Interference" by George Cutsogeorge W2VJN: <http://www.inrad.net/product.php?productid=248&cat=148&page=1> The first chapter is available as a free download and contains key information about power levels for receiver front-end damage. The K3 can protect itself... but as you say, you should make sure it doesn't have to. For diversity I am using an active antenna based on a small horizontal dipole, which works very well in combination with the low-band verticals. Checking with the milliwattmeter and gradually ramping up to full TX power, both the active antenna and the K3 are well enough protected by the cross-polarization. But the 20-10m beam is horizontal and also much closer, so additional protection is needed on those bands. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________________________________________________________ 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 |
Re: Transmitting while listening in diversity mode
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I've written about simple diode RF detectors at
http://www.cliftonlaboratories.com/diodes_for_rf_probes.htm These are not 50 ohm terminated, so it would be a matter of adding a 51 ohm resistor (nearest 5% value) across the RF port). Jack K8ZOA On 1/7/2011 4:37 AM, Ian White GM3SEK wrote: > Tony Estep wrote: >> Nobody commented on my question last night, but I'd still like to hear from >> your collective wisdom, so here's a repeat: I set up my sub-rx to listen on >> transmit antenna B while the main is listening and transmitting on A, and to >> listen on A while main is listening and transmitting on B. This allows for >> diversity reception. >> >> "...here's my question: My two antennas are located so each is in the >> other's null, but they are not far apart, maybe 50 feet at most. When I >> transmit, I don't hear any carrier-operated relays or see any adverse >> reactions, but I'm still not sure that it's okay. The manual sez "well >> isolated," but what I'm looking for is some objective way to test or >> measure. Can anyone tell me how I can establish for sure that I can, or >> cannot, transmit on A when the sub is connected to B, and vice versa? " >> >> Any info (especially first-hand knowledge) would be much appreciated. > Connect a simple diode milliwattmeter to the feed from the RX antenna. > All it needs is a 47 ohm resistor, a 1N914/4148 diode, a .01uF ceramic > cap and your DVM. (This is truly a "Construction 101" project - can > anyone supply a suitable web reference, please?) > > Gently ramp up the power to the TX antenna, and see how much power is > coming back on the RX input. Repeat with every combination of bands and > antennas. > > Also read "Managing Interstation Interference" by George Cutsogeorge > W2VJN: > <http://www.inrad.net/product.php?productid=248&cat=148&page=1> > > The first chapter is available as a free download and contains key > information about power levels for receiver front-end damage. The K3 can > protect itself... but as you say, you should make sure it doesn't have > to. > > For diversity I am using an active antenna based on a small horizontal > dipole, which works very well in combination with the low-band > verticals. Checking with the milliwattmeter and gradually ramping up to > full TX power, both the active antenna and the K3 are well enough > protected by the cross-polarization. But the 20-10m beam is horizontal > and also much closer, so additional protection is needed on those bands. > > > 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 |
Re: Transmitting while listening in diversity mode
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In reply to this post by gm3sek
Ian:
I've written about simple diode RF detectors at http://www.cliftonlaboratories.com/diodes_for_rf_probes.htm These are not 50 ohm terminated, so it would be a matter of adding a 51 ohm resistor (nearest 5% value) across the RF port). Or a 47 ohm would be fine for this purpose. Jack K8ZOA On 1/7/2011 4:37 AM, Ian White GM3SEK wrote: > Tony Estep wrote: >> Nobody commented on my question last night, but I'd still like to hear from >> your collective wisdom, so here's a repeat: I set up my sub-rx to listen on >> transmit antenna B while the main is listening and transmitting on A, and to >> listen on A while main is listening and transmitting on B. This allows for >> diversity reception. >> >> "...here's my question: My two antennas are located so each is in the >> other's null, but they are not far apart, maybe 50 feet at most. When I >> transmit, I don't hear any carrier-operated relays or see any adverse >> reactions, but I'm still not sure that it's okay. The manual sez "well >> isolated," but what I'm looking for is some objective way to test or >> measure. Can anyone tell me how I can establish for sure that I can, or >> cannot, transmit on A when the sub is connected to B, and vice versa? " >> >> Any info (especially first-hand knowledge) would be much appreciated. > Connect a simple diode milliwattmeter to the feed from the RX antenna. > All it needs is a 47 ohm resistor, a 1N914/4148 diode, a .01uF ceramic > cap and your DVM. (This is truly a "Construction 101" project - can > anyone supply a suitable web reference, please?) > > Gently ramp up the power to the TX antenna, and see how much power is > coming back on the RX input. Repeat with every combination of bands and > antennas. > > Also read "Managing Interstation Interference" by George Cutsogeorge > W2VJN: > <http://www.inrad.net/product.php?productid=248&cat=148&page=1> > > The first chapter is available as a free download and contains key > information about power levels for receiver front-end damage. The K3 can > protect itself... but as you say, you should make sure it doesn't have > to. > > For diversity I am using an active antenna based on a small horizontal > dipole, which works very well in combination with the low-band > verticals. Checking with the milliwattmeter and gradually ramping up to > full TX power, both the active antenna and the K3 are well enough > protected by the cross-polarization. But the 20-10m beam is horizontal > and also much closer, so additional protection is needed on those bands. > > > 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 |
Re: Transmitting while listening in diversity mode
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In reply to this post by Tony Estep
Tony,
Most of the time I work in diversity on 160 and 80 when in contest. I tested the antenna setup by transmitting in one antenne and measure the power delivered by the other antenna to a 50ohm resistor. As long as the power (worst case situation) is low enough (I use a 10mW limit) there's no problem. (BTW, for the people who want to know, my powermeter can measure from -50dBm to +30dBm) I'd like to add a question: what do other people use as a limit? 73 Arie PA3A Op 7-1-2011 1:27, Tony Estep schreef: > Nobody commented on my question last night, but I'd still like to hear from > your collective wisdom, so here's a repeat: I set up my sub-rx to listen on > transmit antenna B while the main is listening and transmitting on A, and to > listen on A while main is listening and transmitting on B. This allows for > diversity reception. > > "...here's my question: My two antennas are located so each is in the > other's null, but they are not far apart, maybe 50 feet at most. When I > transmit, I don't hear any carrier-operated relays or see any adverse > reactions, but I'm still not sure that it's okay. The manual sez "well > isolated," but what I'm looking for is some objective way to test or > measure. Can anyone tell me how I can establish for sure that I can, or > cannot, transmit on A when the sub is connected to B, and vice versa? " > > Any info (especially first-hand knowledge) would be much appreciated. > > 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 |
Re: Transmitting while listening in diversity mode
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Thanks to Don, Ian, Jack and Arie for all the excellent info. I'm good to go
now. 73, Tony KT0NY ______________________________________________________________ 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 |
Re: Transmitting while listening in diversity mode
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If the power coupled to the RX antenna is too high, or you just want to be safe, add a small relay in the RX antenna feedline to disconnect it and ground the RX input on transmit. Radio Shack 275-241 works well. I run the 12V coil on 70 V, with a series resistor, to make it switch faster, but it would probably be fast enough for QSK on 12 V. A reed relay would probably be barely audible.
If the sound of the relay bothers you, the same can be done with PIN diodes, though it's a bit more complicated. One could probably just copy the circuit of one of the switches in the K3. 73, Scott K9MA Scott Ellington Madison, Wisconsin USA ______________________________________________________________ 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 |
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In reply to this post by Tony Estep
An IRC Model 196 is an excellent solution. I have them on my K2 and K3. I think they're available from Array Solutions. 73! Ken Kopp - K0PP [hidden email] http://tinyurl.com/7lm3m5 ______________________________________________________________ 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 |
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