RE: [Elecraft] Re: RF Coupleing
that is why the Top Ten AB antenna switches use two relays to gain isolation... bill At 02:04 PM 7/17/2008, Jim Brown wrote: On Wed, 16 Jul 2008 21:15:14 -0700, Ron D'Eau Claire wrote: >In this case Eric is saying there may be a leakage path through a relay. Right. Almost all problems have more than one component. In problems like this one, the sum is the algebraic sum of all of the leakage paths. Relays DO have capacitively coupled leakage. I think I'm hearing numbers on the order of -60 dB, which is pretty respectable for an antenna relay or switch. I've measured numbers on the order of -50 - -55 with the Alpha Delta switches. 73, Jim K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Re: RF Coupleing
On Wed, 16 Jul 2008 21:15:14 -0700, Ron D'Eau Claire wrote: >In this case Eric is saying there may be a leakage path through a relay. Right. Almost all problems have more than one component. In problems like this one, the sum is the algebraic sum of all of the leakage paths. Relays DO have capacitively coupled leakage. I think I'm hearing numbers on the order of -60 dB, which is pretty respectable for an antenna relay or switch. I've measured numbers on the order of -50 - -55 with the Alpha Delta switches. 73, Jim K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Re: RF Coupleing
Quite true Jim. In this case Eric is saying there may be a leakage path through a relay. That doesn't affect how RF behaves in coax, but if that relay is leaking RF it can explain how controlling RF leakage elsewhere, such as by using coax, might not help. In both cases, theory supports reality. As you said, one must know enough - not just about electronics theory - but enough about the situation to understand what to expect. Ron AC7AC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Jim Brown Sent: Wednesday, July 16, 2008 5:15 PM To: Elecraft List Subject: Re: [Elecraft] Re: RF Coupleing On Wed, 16 Jul 2008 13:59:26 -0700, Eric Swartz - WA6HHQ, Elecraft wrote: >Unfortunately theory does not always match reality. Theory ALWAYS matches reality -- when you know enough about both. :) >(i.e. there >are more variables than the person applying the theory is aware of..) Like I said. :) >In >this case we tried coax and it had no impact on improving isolation. >The predominant leakage path is inside the ant switching relay. Makes sense. Jim K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
It is spelled COUPLING, NOT coupleing... hard to believe no one corrected yet. - Original Message - From: "Jim Brown" <[EMAIL PROTECTED]> To: "Elecraft List" Sent: Wednesday, July 16, 2008 8:14 PM Subject: Re: [Elecraft] Re: RF Coupleing On Wed, 16 Jul 2008 13:59:26 -0700, Eric Swartz - WA6HHQ, Elecraft wrote: Unfortunately theory does not always match reality. Theory ALWAYS matches reality -- when you know enough about both. :) (i.e. there are more variables than the person applying the theory is aware of..) Like I said. :) In this case we tried coax and it had no impact on improving isolation. The predominant leakage path is inside the ant switching relay. Makes sense. Jim K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Re: RF Coupleing
Yes. Each conductor carries one phase. Depending upon how you measure what's going on, I think it may indicate only 1/2 the total. For example, try measuring the voltage with respect to the earth. Each side will indicate 1/2 of the total voltage but, since they're opposite in sign, they add producing the total voltage. I believe current will work the same way if you can measure each side independently of the other. An interesting question. I don't believe I've really given it a lot of thought Ron -Original Message- Ron - Don't you mean that the center conductor carries all of the RF current, and the inside of the coaxial cable shield carries an equal amount of current, but of opposite phase? - Jim, KL7CC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
On Wed, 16 Jul 2008 13:59:26 -0700, Eric Swartz - WA6HHQ, Elecraft wrote: >Unfortunately theory does not always match reality. Theory ALWAYS matches reality -- when you know enough about both. :) >(i.e. there >are more variables than the person applying the theory is aware of..) Like I said. :) >In >this case we tried coax and it had no impact on improving isolation. >The predominant leakage path is inside the ant switching relay. Makes sense. Jim K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Re: RF Coupleing
If I had a dollar for every time I did what the theory told me to do just to find that doing something completely different ended up being the right answer. I find this to be the case often when doing ESD and EMI work. Usually after you find the answer you can make up what the problem was by using the theory but there are so many variables that you don't know about that you can't go straight from theory to the answer. You go from theory to stuff to try but not to the answer! -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Eric Swartz - WA6HHQ, Elecraft Sent: Wednesday, July 16, 2008 1:59 PM To: Ron D'Eau Claire Cc: 'Elecraft'; Wayne Burdick Subject: Re: [Elecraft] Re: RF Coupleing Ron - Unfortunately theory does not always match reality. (i.e. there are more variables than the person applying the theory is aware of..) In this case we tried coax and it had no impact on improving isolation. The predominant leakage path is inside the ant switching relay. Please do not post that though as Wayne will make the official statement when he has time. e Ron D'Eau Claire wrote: > Lennart's comments fit my experience. There isn't a "ground loop" formed by > using coax and it does eliminate much of the RF currents floating about at > random inside the rig. > > With the RF current flowing at the center pin connected to coax, the RF > energy must propagate along the *inside* of the coax, with RF currents > flowing on the outside of the center conductor and on the *inside* surface > of the shield. There is only one significant path for the RF: through the > coax. > > Since the center conductor, carrying 1/2 of the RF current, is electrically > isolated from the rest of the rig, there is nothing to encourage RF current > to flow from the connector outer conductor through the metal cabinet to some > other terminal. As noted, RF isn't DC or low-frequency AC. Indeed, it's > useful to consider a wire (or coax) carrying RF as a sort of "wave-guide"; > not the classic stuff used at microwaves, but nevertheless a guide that > directs the RF energy. In that respect, the RF energy flows through the > space between the conductors while inducing RF currents along the surfaces > of those conductors. In coax, the RF energy flows through the dielectric > between the center and shield. That's why dielectric has such a huge effect > on the electrical length of a piece of coax. It retards the RF wave > propagation. > > If a bare wire is used, the RF will flow between it and some convenient > conductor connected to the shielded side of the conductor, such as the > cabinet, pc board ground, etc. That produces an RF field that fills the > space between them which might include lots of other circuits in which the > RF field induces currents. Those are currents that can cause mischief if > they get into an RF-sensitive circuit. > > In any design where I want to isolate the RF I use coaxial cable on all > internal RF connections. Generally it's "overkill" but that's the luxury of > building a one-only homebrew project in which a few extra dollars in parts > is insignificant. That's not the case in something that must be manufactured > at a competitive price and at a profit. That requires engineering expertise > that can evaluate exactly where additional shielding is needed and how much. > > As I often note, engineering is all about making compromises. Great > engineering is about making great compromises. > > Yes, a "hood" on back of a female SO239 might be good, but I've found little > need for one at HF. It might be needed in this case if extreme isolation is > wanted, but I'd be surprised if that were the case. > > Ron AC7AC > > > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Lennart Michaëlsson > > Vic, > I would not go for that solution because the insulated part of the coax > inside the cabinet would reradiate anything coming on the coax from the > outside. Best solution is short piece of coax grounded on the inside of > cabinet AND at the antenna tuner. That is my opinion, humbly yours Len > SM7BIC > > That's certainly part of the problem. But just adding a ground wire might > create a ground loop. I guess the best way to do it would be to insulate the > SO239's from the chassis, and use hoods on them with coax! > -- > 73, > Vic, K2VCO > Fresno CA > http://www.qsl.net/k2vco ___ > Elecraft mailing list > Post to: Elecraft@mailman.qth.net > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth
Re: [Elecraft] Re: RF Coupleing
That's OK Eric, we won't tell. It will be our secret. - Jim, KL7CC Eric Swartz - WA6HHQ, Elecraft wrote: Ahh - The dangers of cc: lists on email. Looks like I just answered 'officially' to the list :-) 73, Eric WA6HHQ _..._ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
Ahh - The dangers of cc: lists on email. Looks like I just answered 'officially' to the list :-) 73, Eric WA6HHQ _..._ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
Ron - Don't you mean that the center conductor carries all of the RF current, and the inside of the coaxial cable shield carries an equal amount of current, but of opposite phase? - Jim, KL7CC Ron D'Eau Claire wrote: Since the center conductor, carrying 1/2 of the RF current, is electrically isolated from the rest of the rig, ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
Ron - Unfortunately theory does not always match reality. (i.e. there are more variables than the person applying the theory is aware of..) In this case we tried coax and it had no impact on improving isolation. The predominant leakage path is inside the ant switching relay. Please do not post that though as Wayne will make the official statement when he has time. e Ron D'Eau Claire wrote: Lennart's comments fit my experience. There isn't a "ground loop" formed by using coax and it does eliminate much of the RF currents floating about at random inside the rig. With the RF current flowing at the center pin connected to coax, the RF energy must propagate along the *inside* of the coax, with RF currents flowing on the outside of the center conductor and on the *inside* surface of the shield. There is only one significant path for the RF: through the coax. Since the center conductor, carrying 1/2 of the RF current, is electrically isolated from the rest of the rig, there is nothing to encourage RF current to flow from the connector outer conductor through the metal cabinet to some other terminal. As noted, RF isn't DC or low-frequency AC. Indeed, it's useful to consider a wire (or coax) carrying RF as a sort of "wave-guide"; not the classic stuff used at microwaves, but nevertheless a guide that directs the RF energy. In that respect, the RF energy flows through the space between the conductors while inducing RF currents along the surfaces of those conductors. In coax, the RF energy flows through the dielectric between the center and shield. That's why dielectric has such a huge effect on the electrical length of a piece of coax. It retards the RF wave propagation. If a bare wire is used, the RF will flow between it and some convenient conductor connected to the shielded side of the conductor, such as the cabinet, pc board ground, etc. That produces an RF field that fills the space between them which might include lots of other circuits in which the RF field induces currents. Those are currents that can cause mischief if they get into an RF-sensitive circuit. In any design where I want to isolate the RF I use coaxial cable on all internal RF connections. Generally it's "overkill" but that's the luxury of building a one-only homebrew project in which a few extra dollars in parts is insignificant. That's not the case in something that must be manufactured at a competitive price and at a profit. That requires engineering expertise that can evaluate exactly where additional shielding is needed and how much. As I often note, engineering is all about making compromises. Great engineering is about making great compromises. Yes, a "hood" on back of a female SO239 might be good, but I've found little need for one at HF. It might be needed in this case if extreme isolation is wanted, but I'd be surprised if that were the case. Ron AC7AC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lennart Michaëlsson Vic, I would not go for that solution because the insulated part of the coax inside the cabinet would reradiate anything coming on the coax from the outside. Best solution is short piece of coax grounded on the inside of cabinet AND at the antenna tuner. That is my opinion, humbly yours Len SM7BIC That's certainly part of the problem. But just adding a ground wire might create a ground loop. I guess the best way to do it would be to insulate the SO239's from the chassis, and use hoods on them with coax! -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Re: RF Coupleing
Lennart's comments fit my experience. There isn't a "ground loop" formed by using coax and it does eliminate much of the RF currents floating about at random inside the rig. With the RF current flowing at the center pin connected to coax, the RF energy must propagate along the *inside* of the coax, with RF currents flowing on the outside of the center conductor and on the *inside* surface of the shield. There is only one significant path for the RF: through the coax. Since the center conductor, carrying 1/2 of the RF current, is electrically isolated from the rest of the rig, there is nothing to encourage RF current to flow from the connector outer conductor through the metal cabinet to some other terminal. As noted, RF isn't DC or low-frequency AC. Indeed, it's useful to consider a wire (or coax) carrying RF as a sort of "wave-guide"; not the classic stuff used at microwaves, but nevertheless a guide that directs the RF energy. In that respect, the RF energy flows through the space between the conductors while inducing RF currents along the surfaces of those conductors. In coax, the RF energy flows through the dielectric between the center and shield. That's why dielectric has such a huge effect on the electrical length of a piece of coax. It retards the RF wave propagation. If a bare wire is used, the RF will flow between it and some convenient conductor connected to the shielded side of the conductor, such as the cabinet, pc board ground, etc. That produces an RF field that fills the space between them which might include lots of other circuits in which the RF field induces currents. Those are currents that can cause mischief if they get into an RF-sensitive circuit. In any design where I want to isolate the RF I use coaxial cable on all internal RF connections. Generally it's "overkill" but that's the luxury of building a one-only homebrew project in which a few extra dollars in parts is insignificant. That's not the case in something that must be manufactured at a competitive price and at a profit. That requires engineering expertise that can evaluate exactly where additional shielding is needed and how much. As I often note, engineering is all about making compromises. Great engineering is about making great compromises. Yes, a "hood" on back of a female SO239 might be good, but I've found little need for one at HF. It might be needed in this case if extreme isolation is wanted, but I'd be surprised if that were the case. Ron AC7AC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lennart Michaëlsson Vic, I would not go for that solution because the insulated part of the coax inside the cabinet would reradiate anything coming on the coax from the outside. Best solution is short piece of coax grounded on the inside of cabinet AND at the antenna tuner. That is my opinion, humbly yours Len SM7BIC That's certainly part of the problem. But just adding a ground wire might create a ground loop. I guess the best way to do it would be to insulate the SO239's from the chassis, and use hoods on them with coax! -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
SV: [Elecraft] Re: RF Coupleing
Vic, I would not go for that solution because the insulated part of the coax inside the cabinet would reradiate anything coming on the coax from the outside. Best solution is short piece of coax grounded on the inside of cabinet AND at the antenna tuner. That is my opinion, humbly yours Len SM7BIC That's certainly part of the problem. But just adding a ground wire might create a ground loop. I guess the best way to do it would be to insulate the SO239's from the chassis, and use hoods on them with coax! -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
Don Wilhelm wrote: Vic, The K3 uses only a single wire to connect to the SO-239 jacks. The return path is through the chassis metal. If one adds a direct return path from the SO-239, that eliminates the potential for a haphazard path for the return current. While a chassis return may be good enough in one situation, let's suppose that the builder did not tighten the SO-239 mounting screws adequately, or the mounting hardware has begun to oxidize, then the return path becomes more 'iffy'. Attaching a return wire from a lug on the SO-239 to the board ground provides a fixed return path that is not dependent on the chassis. Note that the return currents for the two antenna connections can possibly interfere with each other if there is any small voltage differential on the chassis (there always is a differential, the question is just how small a differential is tolerable). That's certainly part of the problem. But just adding a ground wire might create a ground loop. I guess the best way to do it would be to insulate the SO239's from the chassis, and use hoods on them with coax! -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
I had a similar isolation problem between ANT 1 and ANT 2 in my KAT100, discovered by accident after working somebody in EU on 15m using a shielded dummy load connected to ANT 2. Replacing the bare leads between the switching relay and connectors with coax increased the isolation significantly, but I also had to add a smallish relay at the ANT 1 / ANT 2 switching relay K18 to ground the connection not in use to achieve acceptable isolation on the higher bands. A DPDT relay to both switch and ground together with coax would of course be a better method. YMMV with the K3. 73, Geoff GM4ESD Stewart Baker wrote on Wednesday, July 16, 2008 at 5:23 PM David, A very good point. Although the space is rather restricted for RG58/U it should be possible to fit some of the smaller diameter cable such as that used to connect between VHF/UHF PCB's. I have some silver braided coax that would be suitable. It would have little adverse effect over such a small length, but might provide additional isolation. Food for thought... 73 Stewart G3RXQ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
On Wed, 16 Jul 2008 13:12:22 -0400, Don Wilhelm wrote: >The K3 uses only a single wire to connect to the SO-239 jacks. The >return path is through the chassis metal. If one adds a direct return >path from the SO-239, that eliminates the potential for a haphazard path >for the return current. While a chassis return may be good enough in >one situation, One of the first things they teach you in EMC 101 (they have those courses in some of the better EE schools) is that at RF, current will follow coax and ignore a much better DC path, while at DC and low audio, it follows Ohm's Law. Those single wire jumpers are simply bad RF design, and are a major cause of the isolation deficiency noted. The connection back through the chassis is only good at and near DC, because it adds the inductance (and loop area) of that wire jumper and the chassis return to the RF path. Those jumpers should be coax. Period. 50/75 ohms doesn't matter much, it simply needs to be sufficinet for the voltage and current at those points. 73, Jim Brown K9YC ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
Vic, The K3 uses only a single wire to connect to the SO-239 jacks. The return path is through the chassis metal. If one adds a direct return path from the SO-239, that eliminates the potential for a haphazard path for the return current. While a chassis return may be good enough in one situation, let's suppose that the builder did not tighten the SO-239 mounting screws adequately, or the mounting hardware has begun to oxidize, then the return path becomes more 'iffy'. Attaching a return wire from a lug on the SO-239 to the board ground provides a fixed return path that is not dependent on the chassis. Note that the return currents for the two antenna connections can possibly interfere with each other if there is any small voltage differential on the chassis (there always is a differential, the question is just how small a differential is tolerable). 73, Don W3FPR Vic K2VCO wrote: I was told by Elecraft that one of the reasons for the poor isolation between the antenna ports is this: if you don't have the subreceiver installed, then the KAT3 subreceiver port is unterminated. So either install the KRX3 :-) or plug a 50-ohm resistor into the port -- it's on the top rear corner of the KAT3. I haven't tried this (I have a KRX3). I will add that I am not terribly happy with the isolation between the ports even with the subreceiver installed. Don Wilhelm wrote: As an alternative to coax, try using twisted pair - pull a couple pairs out of a short length of CAT-5 cable. One of the pair would be grounded at each end (will require adding a solder lug at the SO-239 jack). 73, Don W3FPR ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
I was told by Elecraft that one of the reasons for the poor isolation between the antenna ports is this: if you don't have the subreceiver installed, then the KAT3 subreceiver port is unterminated. So either install the KRX3 :-) or plug a 50-ohm resistor into the port -- it's on the top rear corner of the KAT3. I haven't tried this (I have a KRX3). I will add that I am not terribly happy with the isolation between the ports even with the subreceiver installed. Don Wilhelm wrote: As an alternative to coax, try using twisted pair - pull a couple pairs out of a short length of CAT-5 cable. One of the pair would be grounded at each end (will require adding a solder lug at the SO-239 jack). 73, Don W3FPR Stewart Baker wrote: David, A very good point. Although the space is rather restricted for RG58/U it should be possible to fit some of the smaller diameter cable such as that used to connect between VHF/UHF PCB's. I have some silver braided coax that would be suitable. It would have little adverse effect over such a small length, but might provide additional isolation. Food for thought... 73 Stewart G3RXQ On Wed, 16 Jul 2008 12:14:03 -0400, David Robertson wrote: Stewart, Your posting is good information however one of the factors of isolation between ANT 1 and 2 can be how the pigtail leads from the 2 SO239 connectors and the antenna coupler board are dressed. It would seem easy to have these nonshielded wires crossing or near each other. The space seems too tight to use rg58/U cable. this could mean that depending how those wires were dressed the coupling would be different between all K3's. 73 Dave KD1NA From: Stewart Baker <[EMAIL PROTECTED]> Subject: Re: [Elecraft] Re: KAT3 ATU and SPE Expert 1K-FA Amplifier To: Dave G4AON <[EMAIL PROTECTED]>, Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="ISO-8859-1" I made some measurements of the isolation between ANT 1 & ANT 2 on my K3. There is little difference between ATU & BYPASS. Unable to do 50MHz. 1.9MHz 58.1dB 3.7MHz 51.9dB 5.1MHz 49.2dB 7.0MHz 47.1dB 10MHz 44.7dB 14MHz 42.5dB 18MHz 40.8dB 21MHz 39.2dB 24MHz 37.1dB 28MHz 35.7dB So on 60m for 100W from ANT 1 there will be 1mW from ANT 2. 73 Stewart G3RXQ -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Re: RF Coupleing
As an alternative to coax, try using twisted pair - pull a couple pairs out of a short length of CAT-5 cable. One of the pair would be grounded at each end (will require adding a solder lug at the SO-239 jack). 73, Don W3FPR Stewart Baker wrote: David, A very good point. Although the space is rather restricted for RG58/U it should be possible to fit some of the smaller diameter cable such as that used to connect between VHF/UHF PCB's. I have some silver braided coax that would be suitable. It would have little adverse effect over such a small length, but might provide additional isolation. Food for thought... 73 Stewart G3RXQ On Wed, 16 Jul 2008 12:14:03 -0400, David Robertson wrote: Stewart, Your posting is good information however one of the factors of isolation between ANT 1 and 2 can be how the pigtail leads from the 2 SO239 connectors and the antenna coupler board are dressed. It would seem easy to have these nonshielded wires crossing or near each other. The space seems too tight to use rg58/U cable. this could mean that depending how those wires were dressed the coupling would be different between all K3's. 73 Dave KD1NA From: Stewart Baker <[EMAIL PROTECTED]> Subject: Re: [Elecraft] Re: KAT3 ATU and SPE Expert 1K-FA Amplifier To: Dave G4AON <[EMAIL PROTECTED]>, Message-ID: <[EMAIL PROTECTED]> Content-Type: text/plain; charset="ISO-8859-1" I made some measurements of the isolation between ANT 1 & ANT 2 on my K3. There is little difference between ATU & BYPASS. Unable to do 50MHz. 1.9MHz 58.1dB 3.7MHz 51.9dB 5.1MHz 49.2dB 7.0MHz 47.1dB 10MHz 44.7dB 14MHz 42.5dB 18MHz 40.8dB 21MHz 39.2dB 24MHz 37.1dB 28MHz 35.7dB So on 60m for 100W from ANT 1 there will be 1mW from ANT 2. 73 Stewart G3RXQ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG - http://www.avg.com Version: 8.0.138 / Virus Database: 270.5.0/1555 - Release Date: 7/16/2008 6:43 AM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Re: RF Coupleing
David, A very good point. Although the space is rather restricted for RG58/U it should be possible to fit some of the smaller diameter cable such as that used to connect between VHF/UHF PCB's. I have some silver braided coax that would be suitable. It would have little adverse effect over such a small length, but might provide additional isolation. Food for thought... 73 Stewart G3RXQ On Wed, 16 Jul 2008 12:14:03 -0400, David Robertson wrote: > Stewart, > Your posting is good information however one of the factors of isolation between ANT 1 > and 2 can be how the pigtail leads from the 2 > SO239 connectors and the antenna coupler board are dressed. It would seem easy to have > these nonshielded wires crossing or near each other. The space seems too tight to use > rg58/U cable. this could mean that depending how those wires were dressed the coupling > would be different between all K3's. > > 73 > > Dave KD1NA > > > From: Stewart Baker <[EMAIL PROTECTED]> > Subject: Re: [Elecraft] Re: KAT3 ATU and SPE Expert 1K-FA Amplifier > To: Dave G4AON <[EMAIL PROTECTED]>, > Message-ID: <[EMAIL PROTECTED]> > Content-Type: text/plain; charset="ISO-8859-1" > > I made some measurements of the isolation between ANT 1 & ANT 2 on > my K3. > > There is little difference between ATU & BYPASS. Unable to do > 50MHz. > > 1.9MHz 58.1dB > 3.7MHz 51.9dB > 5.1MHz 49.2dB > 7.0MHz 47.1dB > 10MHz 44.7dB > 14MHz 42.5dB > 18MHz 40.8dB > 21MHz 39.2dB > 24MHz 37.1dB > 28MHz 35.7dB > > So on 60m for 100W from ANT 1 there will be 1mW from ANT 2. > > 73 > Stewart G3RXQ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
