Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?
On Wed,3/23/2016 11:38 PM, Mark van Wijk, PA5MW wrote: The problem is that while listening to your receiving antennas, there is also some signal from the transmit antenna getting through thanks to the internal cross-talk of your rig's TX/RX relay. There are many heads to this snake, but also many fixes. This post is about crosstalk, NOT interaction. First, there is coupling between the antennas themselves. Cross-band interference between transmit antennas can be greatly reduced by the use of bandpass filters, but these filters don't help with RX antennas not within the filter loop. Second, there is coupling due to leakage capacitance between relays, poor layout of relay boxes, and currents within our stations. My station uses a 6x2 relay box to distribute monoband antennas between rigs for SO2R, but some have a lot more crosstalk than others. Last spring, I replaced an Array Solutions Six-Pak with a 4O3A box. I measured both boxes for isolation using the DG8SAQ VNWA -- the 4O3A unit had more than 20 dB better isolation than the SixPak. But even with that improvement in hardware, I still found isolation insufficient, so I bought a spool of BuryFlex and a box of Amphenol 83-1SP (solder-type coax connectors) and replaced every piece of coax in my station and made sure that all were wrench-tight. (I didn't count, but I'd guess about 25 cables). That provided another 10 dB or so (not measured, but looking at P3 traces while operating). Another issue I still need to address is bandpass filters on RX antennas. I often use my Beverages up to 30M. My K3 can handle the signal strength without damage, but while contesting, I hear very strong harmonics there. In one of the early chapters of his classic book, "Managing Interstation Interference," W2VJN advises us to begin by measuring the coupling between our antennas so that we understand the levels of crosstalk that can be present. It's easy to do that with a vector network analyzer like the DG8SAQ VNWA. [Note that antenna analyzers are NOT network analyzers -- they are single-port devices. The difference is that a VNA is a 2-port device, so it can measure BOTH impedance and the gain (or loss) between input and output ports.] We can, of course, make these measurements with gear as simple as an amplitude-calibrated RF generator and a calibrated voltmeter (anything from a scope to a spectrum analyzer). The VNWA 3e is a real bargain. It's full spec to 500 MHz, reduced spec to 1.3 GHz, and self-powers from the USB connection to your computer. I paid about $750 shipped to my home in W6 about 3 years ago for a unit with calibration kit. http://sdr-kits.net/VNWA3_Description.html 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RXantenna cros-stalk. What do you do?
Good point. On 160 there was also a relatively nearby 829KHz AM BC station. The RDX PI4YLC Field-Day-style station used an OM-Power 6 BPF in its TX path. But no additional BPF or AM BCB HP filter in the RX path. A mistake I should have recognized. Thanks for the test procedure. Will use that additionally for sure at home and at any FD QTH in the future. 73 Mark, PA5MW -Original Message- From: JC Sent: Thursday, March 24, 2016 1:14 PM To: 'Mark van Wijk, PA5MW' ; 'william radice' ; topband@contesting.com Subject: Re: Topband: Post contest season: TX antenna vs RXantenna cros-stalk. What do you do? I was wondering what people do besides the obvious 'kill the TX antenna input during RX mode' ?<< There are several reasons why it is necessary to detune the TX antenna during RX, however disconnecting the center of the TX coax during RX on 160m is a MUST. If you don't understand the problem you never implement the solution. Some broadcast signal can reach -10 dbm or even 0 dbm. Most radios have very poor isolation and pin 1 problem on both the RX input and TX input. In order to open the center pin at the antenna feed point you need a fast vacuum relay to avoid hot switch. For an inverted L it will improve all RX antennas removing re-radiation noise from the TX antenna. Open the circuit between the transverter and the amplifier is a good idea. You need a fast relay but it can be small. Filters must be strong enough to hold at least 200w with low insertion loss. The test to know if you have this problem is simple, disconnect the RX antenna and use a 50ohms, shielded load to terminate the RX input. Tune on the AM band and if you hear strong BC signals coming from you TX antenna during RX with the RX port terminated with 50 ohms you have some homework to do. No carriers at all indicate that you have shield, grounding and choking in good shape, if you hear strong AM signals means that you have isolation and common node noise problems. If the BC signal can come in all QRN and other noise sources also can come in and raise the noise floor of the receiver. My station is quiet, I cannot detect any trace or light carrier doing the test above. Regards JC N4IS _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RX antennacros-stalk. What do you do?
Hi Kees, That is what I successfully do at home, because my 160m vertical re-radiates to my RX antennes. But at the recent RDXC PI4YLC FD contest station both the 40 and 80m full-size deltaloops were not detuned or switched to GND or anything. The YL ops wanted to be able to listen to them as well as the separate RX antennes anyway. 73 Mark, PA5MW -Original Message- From: Kees Nijdam Sent: Thursday, March 24, 2016 11:05 AM To: Mark van Wijk, PA5MW Subject: Re: Topband: Post contest season: TX antenna vs RX antennacros-stalk. What do you do? Hi Mark, When receiving on my RX antennas, my transmit verticals are detuned by decoupling them from the feedline. A floating 1/4 wave verical is completely dead and not reradiating signals. Kees, PE5T -- From: "Mark van Wijk, PA5MW"Sent: Thursday, March 24, 2016 7:38 AM To: "william radice" ; Subject: Re: Topband: Post contest season: TX antenna vs RX antennacros-stalk. What do you do? Hi Bill, I think this is not what I meant here; I also do use BPF's and the Front End Savers. The problem is that while listening to your receiving antennas, there is also some signal from the transmit antenna getting through thanks to the internal cross-talk of your rig's TX/RX relay. I was wondering what people do besides the obvious 'kill the TX antenna input during RX mode' ? 73 Mark, PA5MW -Original Message- From: william radice Sent: Tuesday, March 22, 2016 2:05 PM To: topband@contesting.com Subject: Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do? Serious multi-op contest stations face this issue all the time. Most use individual band filters and they almost completely eliminate the issue. At our station we used the Dunestar filters for operating positions on different bands. As for 160 I personally use the KD9SV "front end saver" and it does the job completely. BILL K4OWR On 3/22/2016 5:44 AM, Mark van Wijk wrote: Now that we are 'sort of in post contest season mode' and sharing some good ideas, there is another question: During recent Field-day setups I noticed severe cross-talk issues between TX antennas and the separate RX antenna circuits. For sure any TX/R relay circuitry offers roughly 50-65 dB dampening. So, during a contest with >S9+30 signals received on the large TX antennas (Deltaloop for 40m and 80m) these would still show up S1 - S4 on the FD station's K3 RX input. At home I normally de-tune my backyard TX antenna(switch to GND during RX) to avoid noise pickup at the RX antennas, so I never noticed this. Question 1: how do you manage the TX-RX cross-talk at your setup? - switch TX antenna to GND during RX - switch-in en external attenuator, so the cross-talk is below noise level, but you are still able to use the TX antenna during RX - any other solution? Question 2: is there any other basic circuitry or setup in a basic contest station which offer possible similar negative side effects? 73, Mark PA5MW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RXantenna cros-stalk. What do you do?
Hi Terry, I have no access to the K3's as they belong to someone else. But I learned there is no such thing as total isolation. Not even with the Frond end savers, unless they incorporate several relays in series. But I did check my TT ORION using the Elecraft XG3 generator; isolation is abt 65dB You do the math when you have 9+40 signals on a large antenna like a fullsize TX deltaloop on 40 & 80m 73 Mark, PA5MW -Original Message- From: Terry Posey Sent: Thursday, March 24, 2016 12:04 PM To: 'Mark van Wijk, PA5MW' ; 'william radice' ; topband@contesting.com ; Eric Swartz -WA6HHQ, Elecraft Subject: Re: Topband: Post contest season: TX antenna vs RXantenna cros-stalk. What do you do? Hi Mark - I have not experienced K3 TX/RX antenna isolation problems with my station configuration. I expect that if there is an isolation problem with your rig's TX and external RX antenna routing/switching, that problem would be nearly impossible to quantify using your station's TX and RX antennas. The rig's TX/RX isolation would need to be measured on the bench, using good laboratory grade equipment. Perhaps, Elecraft can provide a list of expected isolation values that were measured for each of the TX and external RX antenna routing/switching configurations possible with the K3 and K3S. Those measurements would surely have been done during the rigs' design performance verification tests. GL 73, Terry K4RX ++ Hi Bill, I think this is not what I meant here; I also do use BPF's and the Front End Savers. The problem is that while listening to your receiving antennas, there is also some signal from the transmit antenna getting through thanks to the internal cross-talk of your rig's TX/RX relay. I was wondering what people do besides the obvious 'kill the TX antenna input during RX mode' ? 73 Mark, PA5MW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?
>>I was wondering what people do besides the obvious 'kill the TX antenna input during RX mode' ?<< There are several reasons why it is necessary to detune the TX antenna during RX, however disconnecting the center of the TX coax during RX on 160m is a MUST. If you don't understand the problem you never implement the solution. Some broadcast signal can reach -10 dbm or even 0 dbm. Most radios have very poor isolation and pin 1 problem on both the RX input and TX input. In order to open the center pin at the antenna feed point you need a fast vacuum relay to avoid hot switch. For an inverted L it will improve all RX antennas removing re-radiation noise from the TX antenna. Open the circuit between the transverter and the amplifier is a good idea. You need a fast relay but it can be small. Filters must be strong enough to hold at least 200w with low insertion loss. The test to know if you have this problem is simple, disconnect the RX antenna and use a 50ohms, shielded load to terminate the RX input. Tune on the AM band and if you hear strong BC signals coming from you TX antenna during RX with the RX port terminated with 50 ohms you have some homework to do. No carriers at all indicate that you have shield, grounding and choking in good shape, if you hear strong AM signals means that you have isolation and common node noise problems. If the BC signal can come in all QRN and other noise sources also can come in and raise the noise floor of the receiver. My station is quiet, I cannot detect any trace or light carrier doing the test above. Regards JC N4IS _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?
I am using 2xTS590 and never had any issues either. 73s Filipe CT1ILT CR6K Sent from my Huawei Mate 8 Em 24/03/2016 12:05 p.m., "Terry Posey"escreveu: > Hi Mark - > > I have not experienced K3 TX/RX antenna isolation problems with my station > configuration. I expect that if there is an isolation problem with your > rig's TX and external RX antenna routing/switching, that problem would be > nearly impossible to quantify using your station's TX and RX antennas. The > rig's TX/RX isolation would need to be measured on the bench, using good > laboratory grade equipment. > > Perhaps, Elecraft can provide a list of expected isolation values that were > measured for each of the TX and external RX antenna routing/switching > configurations possible with the K3 and K3S. Those measurements would > surely have been done during the rigs' design performance verification > tests. > > GL > > 73, > Terry K4RX > > ++ > Hi Bill, > > I think this is not what I meant here; I also do use BPF's and the Front > End > Savers. > > The problem is that while listening to your receiving antennas, there is > also some signal from the transmit antenna getting through thanks to the > internal cross-talk of your rig's TX/RX relay. > > I was wondering what people do besides the obvious 'kill the TX antenna > input during RX mode' ? > > 73 Mark, PA5MW > > _ > Topband Reflector Archives - http://www.contesting.com/_topband > _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?
Hi Mark - I have not experienced K3 TX/RX antenna isolation problems with my station configuration. I expect that if there is an isolation problem with your rig's TX and external RX antenna routing/switching, that problem would be nearly impossible to quantify using your station's TX and RX antennas. The rig's TX/RX isolation would need to be measured on the bench, using good laboratory grade equipment. Perhaps, Elecraft can provide a list of expected isolation values that were measured for each of the TX and external RX antenna routing/switching configurations possible with the K3 and K3S. Those measurements would surely have been done during the rigs' design performance verification tests. GL 73, Terry K4RX ++ Hi Bill, I think this is not what I meant here; I also do use BPF's and the Front End Savers. The problem is that while listening to your receiving antennas, there is also some signal from the transmit antenna getting through thanks to the internal cross-talk of your rig's TX/RX relay. I was wondering what people do besides the obvious 'kill the TX antenna input during RX mode' ? 73 Mark, PA5MW _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do?
Hi Bill, I think this is not what I meant here; I also do use BPF's and the Front End Savers. The problem is that while listening to your receiving antennas, there is also some signal from the transmit antenna getting through thanks to the internal cross-talk of your rig's TX/RX relay. I was wondering what people do besides the obvious 'kill the TX antenna input during RX mode' ? 73 Mark, PA5MW -Original Message- From: william radice Sent: Tuesday, March 22, 2016 2:05 PM To: topband@contesting.com Subject: Re: Topband: Post contest season: TX antenna vs RX antenna cros-stalk. What do you do? Serious multi-op contest stations face this issue all the time. Most use individual band filters and they almost completely eliminate the issue. At our station we used the Dunestar filters for operating positions on different bands. As for 160 I personally use the KD9SV "front end saver" and it does the job completely. BILL K4OWR On 3/22/2016 5:44 AM, Mark van Wijk wrote: Now that we are 'sort of in post contest season mode' and sharing some good ideas, there is another question: During recent Field-day setups I noticed severe cross-talk issues between TX antennas and the separate RX antenna circuits. For sure any TX/R relay circuitry offers roughly 50-65 dB dampening. So, during a contest with >S9+30 signals received on the large TX antennas (Deltaloop for 40m and 80m) these would still show up S1 - S4 on the FD station's K3 RX input. At home I normally de-tune my backyard TX antenna(switch to GND during RX) to avoid noise pickup at the RX antennas, so I never noticed this. Question 1: how do you manage the TX-RX cross-talk at your setup? - switch TX antenna to GND during RX - switch-in en external attenuator, so the cross-talk is below noise level, but you are still able to use the TX antenna during RX - any other solution? Question 2: is there any other basic circuitry or setup in a basic contest station which offer possible similar negative side effects? 73, Mark PA5MW _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband