Re: [Elecraft] Coax Switch between two rigs
Scott, K3YT, wrote: I think my K2 is an excellent rig and will not risk it by hooking it up to a coax switch with another rig. Point well taken, Scott. Certainly the discussion here has raised my awareness of the issue of switch isolation, and I'll do something different (other than relying on a single MFJ switch) to protect my radios. 73, Chuck NI0C ___ 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] Coax Switch between two rigs
Tony, N2TK/KP2 wrote: Guess I have been lucky. For the past year or so I have been using a Daiwa 2 position coax switch between my K2 and TS-950SDX to the amp. While listening on the 950 through the coax switch I listen to the K2 on the low bands using my receive antennas. If I want to use the K2 to transmit I use the coax switch. So far no problems. 73, N2TK/NP2, Tony Guess I've been lucky, too. I use an MFJ 1702B two-position coax switch to switch a single antenna between two Ten Tec rigs. I've also gotten by with switching the antenna between my KX1 and the Omni 6 feeding an AL-80B amplifier, running 800 watts! 73, Chuck NI0C ___ 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] Coax Switch between two rigs
Maybe you will remain lucky. I just think it is a risky practice and I will continue to keep my transceiver outputs separated. All it takes is one time to smoke a nice rig and you learn. I guess it is like using the ground terminal (third prong) of an 120v AC outlet for an RF ground. Poor practice, but guys do it and say it works. I think my K2 is an excellent rig and will not risk it by hooking it up to a coax switch with another rig. 73, Bob Scott K3YT (originally WD8PLA) 29 years of heating the air with wire) ___ 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] Coax Switch between two rigs
My measurements on ham grade coax switches show 40 dB or less isolation between positions. IN FACT, 60 dB is high even for a commercial grade switch. The simple types from MFJ that are wires to a multiposition wafer switch do not shield quite long wire runs from the adjacent connectors. Those are the long rectangular boxes with UHF jacks all in one row. Stuart K5KVH ___ 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: Re: [Elecraft] Coax Switch between two rigs
My measurements on ham grade coax switches show 40 dB or less isolation between positions. IN FACT, 60 dB is high even for a commercial grade switch. The simple types from MFJ that are wires to a multiposition wafer switch do not shield quite long wire runs from the adjacent connectors. Those are the long rectangular boxes with UHF jacks all in one row. Really? I don't think switching two radios is as big of a deal as the comments in this thread imply. After all, think of all the 100W transceivers where 100W of RF is switched right next to very sensitive circuits (ie the receiver!). I use two K2/100's and switch them to various antennas using an Array Solutions SixPak switch. That switch has a measured isolation between radio ports of 80 dB: http://www.arraysolutions.com/Products/sixpak.htm I would generally trust measurements made by Array Solutions. Many other contesters use this or similar switches. I have no problem listening on another band while transmitting at 1500W on the other radio (unless I am too close to a harmonic). Tor N4OGW/5 ___ 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] Coax Switch between two rigs
Hi Lee, If your coax switch had 60db of isolation between ports (that's about the most you could expect for small $$$), that would mean that a 100 watt signal into Port A would produce a 0.1 milliwatt signal on Port B. While 0.1milliwatt into the receiver on Port B shouldn't destroy the front end, it is a whopping big signal. I used to switch my boatanchor rigs with coax switches, but finally decided to use the method described by Don (the old 'disconnect and short' method). I have carried this method over to my QRP rigs. I use a piece of aluminum angle stock from the local hardware store with HF feedthrough connectors, to connect to the rigs. The antenna goes to one of the rigs, and the other connectors have shorting plugs in them. Ron makes an excellent point about SWR. One tune-up into a high SWR (who hasn't done that?), could ruin your day. I'll trade the inconvenience of disconnecting the unused rig for the peace of mind that neither rig will be over-stressed. You can probably still monitor one rig with the other without having a direct connection. 73, ed - k9ew ___ 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] Coax Switch between two rigs
Just to clarify... I never have 2 rigs connected to one antenna with a switch. That is just asking for trouble. If I do a rig receive comparison, I remove all mikes paddles, footswitches etc so I do not accidentally key up. As another fellow said there can still be a lot of signal on the shield/ground. Just not worth the risk. Here in South Florida I disconnect the rigs from the coax switches when they are not in use. 73 de Bob K3YT ___ 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] Coax Switch between two rigs
What you say is interesting! I have a new coax switch that I just purchased simply for being able to switch between my Icom 706 and K1. I only have one radio on at a time. I use my tuner to switch between the 2 antennas which is the Gap Challenger or W5GI G5RV. On the G5RV I can disconnect the coax outside the window I can ground both antennas from the tuner or simply disconnect the coax from both antennas from the tuner and in 10 years we have had one lightening strike and it did not harm the radio equipment. Now what you say is, that having a switch to switch between 2 radios with one antenna is asking for trouble. How so? I think what you are saying is the fear of keying a rig without an antenna hooked to it. Paul, KD3JF EX: WA4JGI, WA8TER Central Maryland FM19qd (Map Grid Square) - Original Message From: [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Thursday, March 2, 2006 11:01:51 AM Subject: Re: [Elecraft] Coax Switch between two rigs Just to clarify... I never have 2 rigs connected to one antenna with a switch. That is just asking for trouble. If I do a rig receive comparison, I remove all mikes paddles, footswitches etc so I do not accidentally key up. As another fellow said there can still be a lot of signal on the shield/ground. Just not worth the risk. Here in South Florida I disconnect the rigs from the coax switches when they are not in use. 73 de Bob K3YT ___ 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] Coax Switch between two rigs
OKI know that this might be a dumb questions, but before I do a dumb thing I want to ask the question. I have two rigs...one of which is the K2/100. I have a two position coaxial switch (I think it is a Diawa CX201A) that I picked up at a hamfest. Is there enough isolation between the two positions where I could switch between two rigs? I don't want to blow out the front end of either rig. I would think that if you are using one rig, the other rig shouldn't be on or if it is on should not be on the same band. Again, would this be something stupid to do or is it something that is done routinely? Lee- K0WA In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some and use it. If you can't find any common sense, ask for help from somebody who has some common sense. ___ 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] Coax Switch between two rigs
On Mar 1, 2006, at 6:06 AM, Lee Buller wrote: OKI know that this might be a dumb questions, but before I do a dumb thing I want to ask the question. I have two rigs...one of which is the K2/100. I have a two position coaxial switch (I think it is a Diawa CX201A) that I picked up at a hamfest. Is there enough isolation between the two positions where I could switch between two rigs? I don't want to blow out the front end of either rig. I would think that if you are using one rig, the other rig shouldn't be on or if it is on should not be on the same band. Again, would this be something stupid to do or is it something that is done routinely? Lee- K0WA I am not familiar with the Daiwa switch, but the ones I use (Alpha- Delta and MFJ) ground the unused sections and the isolation is quite good. Bob, N7XY ___ 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] Coax Switch between two rigs
Lee, It all depends on the switch - some isolate quite well, but others are really bad. If you want ot be really safe, rig up a relay for each transceiver to do the switching task and short the coax going to the unused transceiver. 73, Don W3FPR -Original Message- OKI know that this might be a dumb questions, but before I do a dumb thing I want to ask the question. I have two rigs...one of which is the K2/100. I have a two position coaxial switch (I think it is a Diawa CX201A) that I picked up at a hamfest. Is there enough isolation between the two positions where I could switch between two rigs? I don't want to blow out the front end of either rig. I would think that if you are using one rig, the other rig shouldn't be on or if it is on should not be on the same band. Again, would this be something stupid to do or is it something that is done routinely? Lee- K0WA ___ 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] Coax Switch between two rigs
Lee Buller wrote: OKI know that this might be a dumb questions, but before I do a dumb thing I want to ask the question. I have two rigs...one of which is the K2/100. I have a two position coaxial switch (I think it is a Diawa CX201A) that I picked up at a hamfest. Is there enough isolation between the two positions where I could switch between two rigs? I have used that same switch to switch between two K2/100's and they have both survived for over a year. Also have used an old BW three position switch to switch between three radios (2 K2/100's and an IC-746) with no problems on any of the radios. I don't think the BW is a grounding switch and I know the Diawa isn't. 73HankK8DD ___ 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] Coax Switch between two rigs
The Daiwa CS201 DOES ground the unused terminal. Check it out. K3YT ___ 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] Coax Switch between two rigs (long)
If you yield to temptation and buy the Elecraft 1KW or 1.5 KW (almost here according to a well placed representative last night) amp, or if you use any amp, be VERY careful about switching as you describe. Of course most QRPers would not dream of defecting to the dark side, but a few do from time to time. The switches mentioned in this thread do not have any or tight specs on port to port isolation. Commercial switches such as the Transco's are speced at 50-60 db port isolation. I learned this after frying a transceiver front end with a consumer grade switch which did ground the unused terminal. A contesting buddy educated me about the need for a high isolation positive contact crossover or transfer switch. Another thing I have learned over the years is that most ground systems are RF hot to a certain extent in many very well built ham installations. For instance, W8JI, RF designer par excellence for DXEngineering and previously for many companies, tells me that despite his extensive ground system --with a ring surrounding his building ( his system is intended to protect the electronics from lightning attacking his 300' and smaller tower farm), his ground system is RF hot. Maybe I should say RF warm. What I mean is that if he (or I) look with a spectrum analyzer ( or listen with a receiver) at the RF noise that comes off a connection to the station ground, you find that the station ground may make a pretty decent RX antenna. The signals may be many dB down from what's coming off your wire or yagi, but they are there in areas with less than perfect earth. If your ground system shows signals 30-40dB down and you are QRO you may have a problem. I also found out about this the hard way. Just for fun, try connecting a short wire from the cover screw on an AC receptacle to a receiver input terminal. You might be surprised as to the signal pickup--including various power system noise sources. So if you are going to use rig switching, especially if using an amp, you do want to make sure that the switch shorts the unused transceiver input. There is a neat way to check whether you are going to experience a dangerous amount of RF pickup. If you can find a Radio Shack that still has and can find hobbyist parts, look for their grain of wheat miniature incandescent bulbs. They have some that are rated at 6v/25ma etc, but you want the one rated at 1.5V/25ma. Solder it to a coax connector and screw it into an unoccupied port on your switch. Crank up your tx/amp to the max power you are going to use and key the TX. Watch the bulb. If you see nothing from the lamp, you are ok. If you see a dull glow, be worried about just how consistent your switch is (I have an Alpha Delta--which I use now only for beverage switching) which shows variable performance, the reason for which is apparent if you open it up and look at the guts). If you see a bright glow or pop the bulb don't even think about using the switch. I have squirreled away the info somewhere, but one of the Beverage gurus has calculated that the typical modern rig is probably borderline with about 15ma being driven into the RX, either through a connection to a RX antenna like a beverage, or power flowing into the transceiver antenna connection when the transceiver is in the receive mode. By the way, that bulb in series with a RX antenna with back-to-back signal diodes across the RX antenna jack, makes a pretty decent protector/indicator when used in low-band dxing. I combined this with ON4UNs front end protection box and have found it very useful. Bob W2WG -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Wednesday, March 01, 2006 10:17 AM To: [EMAIL PROTECTED] Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] Coax Switch between two rigs The Daiwa CS201 DOES ground the unused terminal. Check it out. K3YT ___ 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] Coax Switch between two rigs (long)
Lee - K0WA I concur with these comments from Robert Carroll regarding commercial/military types of switches. You need to be very careful if you use any of the typical amateur type of coax switches. I have 3 stations connected to the same antenna switching network. The three position switch I use came from a swapmeet, and is an Amphenol Model 3N60M10-1 which I tested with a signal generator to determine adequate isolation before installing it. All 3 transceivers can be turned on at the same time on the same frequency, and the selected transceiver can transmit 100 watts which will produce input signals on the other two radios of approximately S9 to 10dB over S9. There are 500 watt amplifiers on two of the setups, but I do not turn on the idle radios when using the amplifiers (although I probably could). One of these transceivers is sometimes my K2. I Also have Icom, Yaesu, and Kenwood in the arrangement. At my barn workshop, I use a pair of Transco p/n CON6AB which are 6 position selector coax switches. Again, these were purchased at a swapmeet and tested before being placed into service. These are used to interconnect antennas and radios between two work benches. The radios are Icom, kenwood, and Collins - but can be whatever I am working on at the time. The collins runs over 500 watts. All these coax switches were made for commercial/military applications, and they all utilize N type connectors. Bird also makes some nice switches for this type of application. Bottom line is that you can do what you are considering, but just select your switches carefully, and test their port-to-port isolation before you interconnect the equipment. Other types of switches might be useable, but take lots of care with your testing before interconnecting the equipment. You can rule some of them out just by listening to a strong station with your antennas connected, and then switch to an open port. Do you still hear the station very weakly? If so, that is a clue to be careful. For example, many of my BW coax switches, Heath antenna tuner with switchable inputs, and MFJ antenna tuner with switchable inputs do not have good isolation for this type of application. Don't misunderstand what I am saying Lee. I use a wide variety of coax switches in my station, but, when it comes to interconnecting radios with a switch, I only use high quality tested switches. In regard to the switches that ground the unused ports, these are also a part of my antenna switching arrangement, but I use them in other parts of my antenna switching system to ground out the incoming antenna feedlines as well as grounding the coax going to the radios. Lots of ways to skin a cat. (Then you can get into spark plugs on 450 ohm balanced line, etc., etc) Have fun Lee. 73, Bill, K5GCW -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of ROBERT CARROLL Sent: Wednesday, March 01, 2006 11:21 AM To: elecraft@mailman.qth.net Subject: RE: [Elecraft] Coax Switch between two rigs (long) If you yield to temptation and buy the Elecraft 1KW or 1.5 KW (almost here according to a well placed representative last night) amp, or if you use any amp, be VERY careful about switching as you describe. Of course most QRPers would not dream of defecting to the dark side, but a few do from time to time. The switches mentioned in this thread do not have any or tight specs on port to port isolation. Commercial switches such as the Transco's are speced at 50-60 db port isolation. I learned this after frying a transceiver front end with a consumer grade switch which did ground the unused terminal. A contesting buddy educated me about the need for a high isolation positive contact crossover or transfer switch. Another thing I have learned over the years is that most ground systems are RF hot to a certain extent in many very well built ham installations. For instance, W8JI, RF designer par excellence for DXEngineering and previously for many companies, tells me that despite his extensive ground system --with a ring surrounding his building ( his system is intended to protect the electronics from lightning attacking his 300' and smaller tower farm), his ground system is RF hot. Maybe I should say RF warm. What I mean is that if he (or I) look with a spectrum analyzer ( or listen with a receiver) at the RF noise that comes off a connection to the station ground, you find that the station ground may make a pretty decent RX antenna. The signals may be many dB down from what's coming off your wire or yagi, but they are there in areas with less than perfect earth. If your ground system shows signals 30-40dB down and you are QRO you may have a problem. I also found out about this the hard way. Just for fun, try connecting a short wire from the cover screw on an AC receptacle to a receiver input terminal. You might be surprised as to the signal pickup--including various power system noise sources. So if you are going
Re: [Elecraft] Coax Switch between two rigs (long)
G'day,
| There is a neat way to check whether you are going to experience a
dangerous
| amount of RF pickup. If you can find a Radio Shack that still has and
can
| find hobbyist parts, look for their grain of wheat miniature
incandescent
| bulbs. They have some that are rated at 6v/25ma etc, but you want the
one
| rated at 1.5V/25ma. Solder it to a coax connector and screw it into an
| unoccupied port on your switch. Crank up your tx/amp to the max power
you
| are going to use and key the TX. Watch the bulb. If you see nothing
from
| the lamp, you are ok. If you see a dull glow, be worried about just how
| consistent your switch is (I have an Alpha Delta--which I use now only
for
| beverage switching) which shows variable performance, the reason for
which
| is apparent if you open it up and look at the guts).
The Yaesu FT-101 had a lamp in series with the RX side of the TX/RX change
over relay. When I was in the Antarctic ('74 - '76) and running traffic
on the main station (1.5kW) it was not unusual to see the lamp flashing
along with the CW or SSB if I left the antenna on the '101. Never hurt
it.
Regards,
Mike VP8NO
___
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