Topband: FRONT END SAVER
There is nothing magical about a front end saver, IMHO. Several years ago I built my first, a simple unit employing a pair of Panasonic PCB-type relays which grounded both the RX antenna port on my transceiver and the beverage antenna input to the preamp/switching system on transmit. As long as you do not intend to use full break-in this system works very well and costs peanuts to build; after some 15 years running a KW or better no problems have ever occurred, and I have duplicated this simple design at other stations. Of course, you can build a fancier unit which will handle full break-in and perhaps have a few bells and whistles included, but the basic unit will serve the purpose for most hams running separate antennas for RX and TX. Bill VE3CSK/VE3NH _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
I'm not sure goosing the pull-in voltage is always a good idea. It may shorten the initial closing time a bit, but (depending on the relay) it can aggravate contact bounce, doing more harm than good. It also stresses the relay. 73, Jim w8zr Sent from my iPhone On Aug 30, 2015, at 10:57 AM, Martin Kratoska mar...@centrum.cz wrote: It is here: http://www.somis.org/ 73, Martin, OK1RR Dne 30.8.2015 v 16:32 Larry napsal(a): Measures (K6???) did a relay speed-up scheme for QSK on an SB220, I don't remember the details but it was something like hitting the relay with higher than usual coil voltage/current and it shortened up the relay pull-in time. It might be more complicated in this application than needed. I don't have the URL to Measures' site but it can probably be found by a search. 73, Larry W6NWS -Original Message- From: Douglas Ruz (CO8DM) Sent: Sunday, August 30, 2015 8:41 AM To: Tom W8JI ; Charles Cu nningham ; 'topBand List' Subject: Re: Topband: KD9SV-OK1RR relays ??? Tom and all members of the list thanks for your ideas and time . I have a plan B: I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It is an FT80C, the commercial version with metallic chassis) few months ago. I was using that BNC to feed an SDR receiver using the same antenna. If i add a SPDT switch also on the rear panel and RE-WIRE the BNC connection i can get an RX port in my old radio and can connect an RX antenna...like modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX and BNC for RX)...i made few mods to my radio, so, i know it very well... Maybe that will help...of course, i must add then an Front End Saver...still need a fast relay !!! Maybe the Plan A with a 5mS relay will be more easy...still need a fast relay too !!! 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla - Original Message - From: Tom W8JI w...@w8ji.com To: Charles Cu nningham charlie-cunning...@nc.rr.com; 'topBand List' topband@contesting.com Sent: Sunday, August 30, 2015 12:27 AM Subject: Re: Topband: KD9SV-OK1RR relays ??? It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. In receive mode the collector-base junction would have substantial reverse bias and the transistor can be chosen for low collector-base capacitance. With a fast switch like a 2N708 or something similar the switching time will, of course, FAR outperform a relay closure time. This thread might have splintered. I was responding to this: Your FT-747 only has one antenna input. It does not have a second receiver. It doesn't even have a receive-only antenna input. You cannot transmit and receive at same time. Why do you need a front end saver? If it is a transceiver without an RX antenna point, the problem is adding a receive antenna to a transceiver that does not have a receive port. If it is a transceiver with an RX port, the requirement for an external front end saver and what will work depends on the antennas, the power, the transceiver, and the antenna spacing. A front end saver can be very simple with some radios, more complicated, or not needed at all. An external switch is never easy to do correctly, unless the radio has good TX RX switching time sequencing. I'm unclear what the application is, but a 10 mS relay is really too slow for either application. The sequencing issues I pointed out apply to both systems. 73 Tom _ 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 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: FRONT END SAVER
Bill, I don't know the complete list of radios that need one, but I do know that more than one IC-751A and IC-765 have been damaged without some kind of protection against RF getting in through the separate RX ANT input. 73, Mike www.w0btu.com On Sun, Aug 30, 2015 at 6:08 AM, Bill Liz ma...@isp.ca wrote: There is nothing magical about a front end saver ... _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
How about back-to-back 1N4148 diodes (2 in series) across the RX path, and a #47 incandescent lamp between those and the Beverage? That's what I do here, among other things. Those are in series with my preamp, which is almost always on. There's also some variable resistance in series with the lamp and the Beverage switching relays. I do that so that the signal from the Beverage is equal with the RX signal from the inverted-L. 73, Mike www.w0btu.com On Sat, Aug 29, 2015 at 8:06 PM, Charles Cu nningham charlie-cunning...@nc.rr.com wrote: It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
I have also used bi-directional 1N4148 diodes across the antenna path, but I'm re-thinking that approach - If the diodes are not preceded by a good bandpass - or at least, a hipass filter in the antenna lead, I'd be concerned in some instances about the possibility of intermod from nearby, or strong BC stations. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Mike Waters Sent: Sunday, August 30, 2015 3:52 PM To: Charles Cunningham Cc: topband; Tom W8JI Subject: Re: Topband: KD9SV-OK1RR relays ??? How about back-to-back 1N4148 diodes (2 in series) across the RX path, and a #47 incandescent lamp between those and the Beverage? That's what I do here, among other things. Those are in series with my preamp, which is almost always on. There's also some variable resistance in series with the lamp and the Beverage switching relays. I do that so that the signal from the Beverage is equal with the RX signal from the inverted-L. 73, Mike www.w0btu.com On Sat, Aug 29, 2015 at 8:06 PM, Charles Cu nningham charlie-cunning...@nc.rr.com wrote: It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
The mast of my RX flag is 20-25 ft from my 160/80m shunt fed tower. I run a KW+ on the low bands. I use an Array Solutions AS-RXFEP RF Limiter (aka FES etc.) in line with the flag at the rig’s RX Ant IN. The RXFEP uses a gas discharge tube and a pair of matching transformers with back-to-back diodes in between. I favor this passive approach which avoids having to deal with any relay and sequencing issues when QSK. https://www.arraysolutions.com/Products/as_rxfep.htm The “manual” link shows the schematic. I also use a W3NQN BCB filter (from AS). I have had my K3’s COR (carrier operated relay) trigger on 80m depending upon the orientation of the flag. A not so obvious RF path of some sort. This issue was solved by placing the BCB ahead of the FEP. I recommend the RXFEP if you want a passive non-relay solution. If you have strong local BC stations, the W3NQN brick wall BCB filter works wonders. Steve WB6RSE _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Array Solutions offers a 'RX Front End Protector' based on back-to-back 1N4148 diodes. Schematic: http://www.ok1rr.com/public/rxfep.png more details: http://www.arraysolutions.com/Products/as_rxfep.htm manual (also pictures of clipping etc.) http://www.arraysolutions.com/images/AS-RXFEPdatasheet.pdf It works as described, no problems although it can cause spurious radiations on densely equipped multi-multi contest sites using very high power amps. For single TX DXer it can be possibly preferred over relay devices we talked about. Anyway, you test! BTW if the AS-RXFEP will be housed in a plastic box it will provide a lot of additional CM suppression. 73, Martin, OK1RR Dne 30.8.2015 v 21:52 Mike Waters napsal(a): How about back-to-back 1N4148 diodes (2 in series) across the RX path, and a #47 incandescent lamp between those and the Beverage? That's what I do here, among other things. Those are in series with my preamp, which is almost always on. There's also some variable resistance in series with the lamp and the Beverage switching relays. I do that so that the signal from the Beverage is equal with the RX signal from the inverted-L. 73, Mike www.w0btu.com On Sat, Aug 29, 2015 at 8:06 PM, Charles Cu nningham charlie-cunning...@nc.rr.com wrote: It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: FRONT END SAVER
There is nothing magical about a front end saver, IMHO. Several years ago I built my first, a simple unit employing a pair of Panasonic PCB-type relays which grounded both the RX antenna port on my transceiver and the beverage antenna input to the preamp/switching system on transmit. As long as you do not intend to use full break-in this system works very well and costs peanuts to build; after some 15 years running a KW or better no problems have ever occurred, and I have duplicated this simple design at other stations. Hi Bill, It is easy to assume there is nothing critical about a front end saver (a poor name in many applications) when we think we have one that works, but it does a lot more than saving the front end. Besides preventing damage, it also keeps radios from generating clicks and spurious signals. Some radios and installations do not need these systems, some do. Some systems not needing them (or being critical) doesn't mean they are all not critical. They are system dependent for antenna types, antenna physical layout, radio type, and power level. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It is an FT80C, the commercial version with metallic chassis) few months ago. I was using that BNC to feed an SDR receiver using the same antenna. If i add a SPDT switch also on the rear panel and RE-WIRE the BNC connection i can get an RX port in my old radio and can connect an RX antenna...like modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX and BNC for RX)...i made few mods to my radio, so, i know it very well... There you go. That is a good solution. Now you know you cannot directly transmit into the receiver antenna. Once you do that preventing excessive RF voltage back into the receiver is much easier, but it still requires an fast system. I would also use a hard clamp system and fuse for level, not just a single relay. For just a very few extra components, it can be hundreds of times more reliable! When we get so much for so little, it is worth considering. When I see a front end saver without a fuse or clamp system, I know it is not a safe design. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
It is here: http://www.somis.org/ 73, Martin, OK1RR Dne 30.8.2015 v 16:32 Larry napsal(a): Measures (K6???) did a relay speed-up scheme for QSK on an SB220, I don't remember the details but it was something like hitting the relay with higher than usual coil voltage/current and it shortened up the relay pull-in time. It might be more complicated in this application than needed. I don't have the URL to Measures' site but it can probably be found by a search. 73, Larry W6NWS -Original Message- From: Douglas Ruz (CO8DM) Sent: Sunday, August 30, 2015 8:41 AM To: Tom W8JI ; Charles Cu nningham ; 'topBand List' Subject: Re: Topband: KD9SV-OK1RR relays ??? Tom and all members of the list thanks for your ideas and time . I have a plan B: I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It is an FT80C, the commercial version with metallic chassis) few months ago. I was using that BNC to feed an SDR receiver using the same antenna. If i add a SPDT switch also on the rear panel and RE-WIRE the BNC connection i can get an RX port in my old radio and can connect an RX antenna...like modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX and BNC for RX)...i made few mods to my radio, so, i know it very well... Maybe that will help...of course, i must add then an Front End Saver...still need a fast relay !!! Maybe the Plan A with a 5mS relay will be more easy...still need a fast relay too !!! 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla - Original Message - From: Tom W8JI w...@w8ji.com To: Charles Cu nningham charlie-cunning...@nc.rr.com; 'topBand List' topband@contesting.com Sent: Sunday, August 30, 2015 12:27 AM Subject: Re: Topband: KD9SV-OK1RR relays ??? It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. In receive mode the collector-base junction would have substantial reverse bias and the transistor can be chosen for low collector-base capacitance. With a fast switch like a 2N708 or something similar the switching time will, of course, FAR outperform a relay closure time. This thread might have splintered. I was responding to this: Your FT-747 only has one antenna input. It does not have a second receiver. It doesn't even have a receive-only antenna input. You cannot transmit and receive at same time. Why do you need a front end saver? If it is a transceiver without an RX antenna point, the problem is adding a receive antenna to a transceiver that does not have a receive port. If it is a transceiver with an RX port, the requirement for an external front end saver and what will work depends on the antennas, the power, the transceiver, and the antenna spacing. A front end saver can be very simple with some radios, more complicated, or not needed at all. An external switch is never easy to do correctly, unless the radio has good TX RX switching time sequencing. I'm unclear what the application is, but a 10 mS relay is really too slow for either application. The sequencing issues I pointed out apply to both systems. 73 Tom _ 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: KD9SV-OK1RR relays ???
Tom and all members of the list thanks for your ideas and time . I have a plan B: I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It is an FT80C, the commercial version with metallic chassis) few months ago. I was using that BNC to feed an SDR receiver using the same antenna. If i add a SPDT switch also on the rear panel and RE-WIRE the BNC connection i can get an RX port in my old radio and can connect an RX antenna...like modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX and BNC for RX)...i made few mods to my radio, so, i know it very well... Maybe that will help...of course, i must add then an Front End Saver...still need a fast relay !!! Maybe the Plan A with a 5mS relay will be more easy...still need a fast relay too !!! 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla - Original Message - From: Tom W8JI w...@w8ji.com To: Charles Cu nningham charlie-cunning...@nc.rr.com; 'topBand List' topband@contesting.com Sent: Sunday, August 30, 2015 12:27 AM Subject: Re: Topband: KD9SV-OK1RR relays ??? It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. In receive mode the collector-base junction would have substantial reverse bias and the transistor can be chosen for low collector-base capacitance. With a fast switch like a 2N708 or something similar the switching time will, of course, FAR outperform a relay closure time. This thread might have splintered. I was responding to this: Your FT-747 only has one antenna input. It does not have a second receiver. It doesn't even have a receive-only antenna input. You cannot transmit and receive at same time. Why do you need a front end saver? If it is a transceiver without an RX antenna point, the problem is adding a receive antenna to a transceiver that does not have a receive port. If it is a transceiver with an RX port, the requirement for an external front end saver and what will work depends on the antennas, the power, the transceiver, and the antenna spacing. A front end saver can be very simple with some radios, more complicated, or not needed at all. An external switch is never easy to do correctly, unless the radio has good TX RX switching time sequencing. I'm unclear what the application is, but a 10 mS relay is really too slow for either application. The sequencing issues I pointed out apply to both systems. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Tom - Maybe we should say backwards T/R relay when we mean the reverse, of what we did with real T/R relays when I was a kid. All of my rigs used 120VAC outboard relay coils! FT-747 is indeed notorious for T/R timing issues, its semi-break-in so severely truncating the leading element on CW like many rigs of its era, such a great delay between key down and RF out that the ARRL reviewer recommended against using the rigs semi-break-in and instead recommending for manual T/R changeover. Tim N3QE On Sun, Aug 30, 2015 at 12:27 AM, Tom W8JI w...@w8ji.com wrote: It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. In receive mode the collector-base junction would have substantial reverse bias and the transistor can be chosen for low collector-base capacitance. With a fast switch like a 2N708 or something similar the switching time will, of course, FAR outperform a relay closure time. This thread might have splintered. I was responding to this: Your FT-747 only has one antenna input. It does not have a second receiver. It doesn't even have a receive-only antenna input. You cannot transmit and receive at same time. Why do you need a front end saver? If it is a transceiver without an RX antenna point, the problem is adding a receive antenna to a transceiver that does not have a receive port. If it is a transceiver with an RX port, the requirement for an external front end saver and what will work depends on the antennas, the power, the transceiver, and the antenna spacing. A front end saver can be very simple with some radios, more complicated, or not needed at all. An external switch is never easy to do correctly, unless the radio has good TX RX switching time sequencing. I'm unclear what the application is, but a 10 mS relay is really too slow for either application. The sequencing issues I pointed out apply to both systems. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Measures (K6???) did a relay speed-up scheme for QSK on an SB220, I don't remember the details but it was something like hitting the relay with higher than usual coil voltage/current and it shortened up the relay pull-in time. It might be more complicated in this application than needed. I don't have the URL to Measures' site but it can probably be found by a search. 73, Larry W6NWS -Original Message- From: Douglas Ruz (CO8DM) Sent: Sunday, August 30, 2015 8:41 AM To: Tom W8JI ; Charles Cu nningham ; 'topBand List' Subject: Re: Topband: KD9SV-OK1RR relays ??? Tom and all members of the list thanks for your ideas and time . I have a plan B: I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It is an FT80C, the commercial version with metallic chassis) few months ago. I was using that BNC to feed an SDR receiver using the same antenna. If i add a SPDT switch also on the rear panel and RE-WIRE the BNC connection i can get an RX port in my old radio and can connect an RX antenna...like modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX and BNC for RX)...i made few mods to my radio, so, i know it very well... Maybe that will help...of course, i must add then an Front End Saver...still need a fast relay !!! Maybe the Plan A with a 5mS relay will be more easy...still need a fast relay too !!! 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla - Original Message - From: Tom W8JI w...@w8ji.com To: Charles Cu nningham charlie-cunning...@nc.rr.com; 'topBand List' topband@contesting.com Sent: Sunday, August 30, 2015 12:27 AM Subject: Re: Topband: KD9SV-OK1RR relays ??? It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. In receive mode the collector-base junction would have substantial reverse bias and the transistor can be chosen for low collector-base capacitance. With a fast switch like a 2N708 or something similar the switching time will, of course, FAR outperform a relay closure time. This thread might have splintered. I was responding to this: Your FT-747 only has one antenna input. It does not have a second receiver. It doesn't even have a receive-only antenna input. You cannot transmit and receive at same time. Why do you need a front end saver? If it is a transceiver without an RX antenna point, the problem is adding a receive antenna to a transceiver that does not have a receive port. If it is a transceiver with an RX port, the requirement for an external front end saver and what will work depends on the antennas, the power, the transceiver, and the antenna spacing. A front end saver can be very simple with some radios, more complicated, or not needed at all. An external switch is never easy to do correctly, unless the radio has good TX RX switching time sequencing. I'm unclear what the application is, but a 10 mS relay is really too slow for either application. The sequencing issues I pointed out apply to both systems. 73 Tom _ 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: KD9SV-OK1RR relays ???
Tom is right about this thread splintered. It is bugging me to hear several very common misconceptions going on for years. 1- A preamp is part of the radio, not the antenna. As such, when you add a preamp, you are changing the RADIO performance, not fixing the antenna gain. For low bands IP3 is a must, even for radios that claim + 30db because IP3 has a very poor performance on low bands. For example: IC7600, any KW station on 160m 5 miles away can wipe weak signals on the band due to reciprocal mixing. You can do a quick check on how bad it is; if you hear a strong carrier on 1810, 1820 or 1830, you definitely have a problem. 2- Adding a preamp 20 db. gain you drop the IP3 by 20 db, making the radio almost useless. 3- RX antenna has low gain and most people understand that it offsets the IP3 problem. The issue is that RX antenna gain changes with frequency, a FLAG , EWE K9AY have -20 db. gain on 160, but close to minus 0.5 db. gain on 7 MHz . So, the strong signals on 6MHz 9 MHs 10 to 12 MHz, can cause a real damage on weak signal reception. A good band pass filter in the front and another in the back of the preamp is a MUST for most radios. Using only a good high pass AM BC filter helps half of the needed protection, all preamps need a good AM BC filter for 160m operation, and only the NORTON preamps can perform without a band pass filter bit, but it is not enough. 4- Adding to the problem of increasing the gain and reducing the IP3, the size of feed lines, rotor cables and most of all other cables connected to your station (like 144 MHz vertical with 120 ft. of coax cable makes a good vertical for 1.8 MHz) , are near 1/4 wave long on low bands. It means those wires are indeed vertical or long wires receiving high amount of energy and feeding your ground connection. All of them must be grounded in several places to break the 1/4 wave problem and fix the common mode noise issue. Using a choke near the ground next to the radio can even reduce the noise floor on 20m. Not taking care of common mode noise can make any preamp useless. 5- Noise figure is another huge misconception. GAIN does not improve signal to noise ratio, actually all preamps and any electronic circuit, adds noise to the output and decrease the signal to noise ratio. THE SNR OR NF IS FREQUENCY DEPENDENT and the all available equipment starts the measurement at 10 MHz and above. NF looks good on GHz for several new devices, but, what about 1.8 MHz? The noise figure on low bands can be as bad as 10 db. NF, in some cases even more (the MHz devices are only good for cellphones) Most radios already have 5 db. NF (internal preamp on) and 20 db. NF (internal preamp off). You will really need a preamp better than 5 db. to improve the signal to noise ratio, or you are just adding problems to your RX. The W7UIV preamp with 5db NF is 100% useless for receiving weak signals on top-band, if you increase the audio gain and decrease the RF gain in your radio, you will improve the receiving signal to noise ratio better than adding a preamp with 18db / 5db. noise figure. In this situation there are no signal to noise improvement at all!. You dont need it! What is the difference between increasing the audio gain in 20 db. or adding a 20 db. preamp with the same radio NF? NONE, just an AGC comfort for strong signal handle. Here is what bugs me the most, some statements like You don't need a good 1 dB NF preamp on low bands, or You don't need a preamp at all. These are the most misconception urban legends ever believed. The NF concept is based on degradation of the signal to noise radio. It means that, when the power noise is the same as the power of the signal, the ratio is 3 db. - half noise, half signal. In this case the degradation is close to 2 db., which is the button line. The SNR needs to be 3db. or better for you to be able to copy a weak CW signal or 8 to 10 db. for you to copy a weak SSB signal. So, where is the antenna noise floor? The antenna noise floor is depended of the intensity of the signal delivered from the antenna at the input of the receiver in dBm, it has absolutely nothing to do with the band itself. A minus 120 dBm signal is the same on 1.8 MHz and 144 MHz . The confusion starts with the noise on low bands. Several reports, like ITU 372, show that, in 95% of the time, the atmospheric noise is very high on low band and very low on HF, but, how about the other 5%? Guess what , in 5% of the time the atmospheric noise in 160m gets low as 100K (1db NF) on 2 MHz and 5000 K on 10 MHz (20db NF). As you can see, the concept of equivalent noise temperature is very complex for even the most experienced engineers, and I will not cover it here. When there is atmospheric noise we dont even turn on the radio, so, 95% does not mean much because we only use the radio on low bands when the atmospheric noise is low. For example, on that winter morning after a light rain the noise on 160m can be as low as -125dbm, this will be lower
Re: Topband: KD9SV-OK1RR relays ???
On Sun,8/30/2015 7:32 AM, Larry wrote: Measures (K6???) did a relay speed-up scheme for QSK on an SB220, I don't remember the details but it was something like hitting the relay with higher than usual coil voltage/current and it shortened up the relay pull-in time. My neighbor, Bob Wolbert, K6XX, has worked for Elecraft for several years. Many years ago, he published a circuit like what you're describing. He credits it to Tony, K1KP. http://www.k6xx.com/radio/fastrely.pdf http://www.k6xx.com/ikanrite.html#fastrely 73, Jim K9YC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
I'm not sure goosing the pull-in voltage is always a good idea. It may shorten the initial closing time a bit, but (depending on the relay) it can aggravate contact bounce, doing more harm than good. It also stresses the relay. Done properly, it doesn't hurt a thing. The proper way is to use current limiting. It is safe to run 50 volt supplies on most 12 volt relays, but there is a point of diminishing returns on speed. The high initial voltage ramps up the magnetic field faster, but it does not cause excessive heat or current. This is because the relay starts at near zero mA from inductance. None of this matters, though. Using a relay on make for protection is a bad idea. The de-active state should be used for protection, and the active energized state used to allow RX. _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
That's similar to mine, but mine has two 1N4148 diodes in series, back-to-back, total of four diodes. However, after I did that, I got to thinking that it would be better with only two. Or that there was no need for four. (Don't ask me to explain, it's been a long time since I've thought about that.) 73, Mike www.w0btu.com On Sun, Aug 30, 2015 at 5:00 PM, Martin Kratoska mar...@centrum.cz wrote: Array Solutions offers a 'RX Front End Protector' based on back-to-back 1N4148 diodes. Schematic: http://www.ok1rr.com/public/rxfep.png _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
I read it a long time ago on Measures; website. I never used it. I didn’t have an SB220. I just remembered that it was a relay speed up scheme. I mentioned it just in case may help with speeding up a slower relay. The original poster would have to consider if the scheme would be suitable under the circumstances and would it satisfy the suggestions of Tom (W8JI) about the transfer speed. There may be better schemes around or even relays that are fast enough. 73, Larry W6NWS From: Garry Shapiro Sent: Sunday, August 30, 2015 6:27 PM To: Larry Subject: Re: Topband: KD9SV-OK1RR relays ??? You may be confusing Measures (AG6K) with Wolbert (K6XX) who has published a simple speed-up circuit as you describe. Garry, NI6T On 8/30/2015 7:32 AM, Larry wrote: Measures (K6???) did a relay speed-up scheme for QSK on an SB220, I don't remember the details but it was something like hitting the relay with higher than usual coil voltage/current and it shortened up the relay pull-in time. It might be more complicated in this application than needed. I don't have the URL to Measures' site but it can probably be found by a search. 73, Larry W6NWS -Original Message- From: Douglas Ruz (CO8DM) Sent: Sunday, August 30, 2015 8:41 AM To: Tom W8JI ; Charles Cu nningham ; 'topBand List' Subject: Re: Topband: KD9SV-OK1RR relays ??? Tom and all members of the list thanks for your ideas and time . I have a plan B: I added a BNC female connector in the rear panel of my old Yaesu, FT747 (It is an FT80C, the commercial version with metallic chassis) few months ago. I was using that BNC to feed an SDR receiver using the same antenna. If i add a SPDT switch also on the rear panel and RE-WIRE the BNC connection i can get an RX port in my old radio and can connect an RX antenna...like modern radios...Switch Pos A (main antenna at SO239)...Pos B (SO239 for TX and BNC for RX)...i made few mods to my radio, so, i know it very well... Maybe that will help...of course, i must add then an Front End Saver...still need a fast relay !!! Maybe the Plan A with a 5mS relay will be more easy...still need a fast relay too !!! 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla - Original Message - From: Tom W8JI mailto:w...@w8ji.com To: Charles Cu nningham mailto:charlie-cunning...@nc.rr.com; 'topBand List' mailto:topband@contesting.com Sent: Sunday, August 30, 2015 12:27 AM Subject: Re: Topband: KD9SV-OK1RR relays ??? It seems to me that a very fast operating preamp protection circuit could be constructed employing a good fast saturating NPN switching transistor across the antenna path. In receive mode the collector-base junction would have substantial reverse bias and the transistor can be chosen for low collector-base capacitance. With a fast switch like a 2N708 or something similar the switching time will, of course, FAR outperform a relay closure time. This thread might have splintered. I was responding to this: Your FT-747 only has one antenna input. It does not have a second receiver. It doesn't even have a receive-only antenna input. You cannot transmit and receive at same time. Why do you need a front end saver? If it is a transceiver without an RX antenna point, the problem is adding a receive antenna to a transceiver that does not have a receive port. If it is a transceiver with an RX port, the requirement for an external front end saver and what will work depends on the antennas, the power, the transceiver, and the antenna spacing. A front end saver can be very simple with some radios, more complicated, or not needed at all. An external switch is never easy to do correctly, unless the radio has good TX RX switching time sequencing. I'm unclear what the application is, but a 10 mS relay is really too slow for either application. The sequencing issues I pointed out apply to both systems. 73 Tom _ 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: KD9SV-OK1RR relays ??? (RX Front End Protector)
That's similar to mine, but mine has two 1N4148 diodes in series, back-to-back, total of four diodes. However, after I did that, I got to thinking that it would be better with only two. Or that there was no need for four. (Don't ask me to explain, it's been a long time since I've thought about that.) You probably used four diodes for a good reason. 20 dB is 2.73 volts RMS across 75 ohms. That is 3.86 volts peak. If you use back-to-back diodes, the system clamps at .7 volts peak and mixes at lower levels. That's like 5-10 dBm or less for the sum of all signal power. Remember that clamp is seeing the vector sum of voltages from ALL the signals on the RX antenna, not just signals on the band you are using or the signal you are listening to. I can't use diodes here because of IMD, so I use a hard limiting clamp that is preset by a Zener diode. Why would anyone want a clamp system that reduces the IM DR of a modern receiver? If you pay all that money for an RX, why not use it? I would think your 4 diodes are the absolute minimum to use almost any receiver's full dynamic range. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: Fast relay ???
Martin, Tom and all members of the list, The AS RXFEP is very nice but it is very expensive. I prefer the KD9SV modify by Martin, OK1RR...it is very easy to build but i need only the relays...someone can help me to get those relays ???...are they available at digikey or mouser ??? The circuit is very easy to duplicate but i just need the fast relays. Thanks, 73Douglas, CO8DM No creo que haya alguna emoción más intensa para un inventor que ver alguna de sus creaciones funcionando. Esa emoción hace que uno se olvide de comer, de dormir, de todo. - Nikola Tesla _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
remember the details but it was something like hitting the relay with higher than usual coil voltage/current and it shortened up the relay pull-in time. It might be more complicated in this application than needed. I don't have the URL to Measures' site but it can probably be found by a search. The protection system should default on, not default off. If a relay is used, the NC contacts should short the line or NO contacts disconnect the line. It must be done this way because you do not want a connection or trigger failure to damage the receiver, or cause a spurious issue (which is most frequent). The receive antenna connection has to be allowed through willful application of relay voltage, not through removal of voltage. Since the relay should be energized for RX and de-energized for transmit, the critical time is release time. The only way to speed release is avoid excessive holding current, and not use a clamp diode or any load across the relay coil. The transceiver and station relay control line, which normally pulls low in transmit, allows relay voltage when high (transmit off). This allows the receive system connection by activating the RX relay. When the TX line pulls low, the RX relay deactivates and the system goes to transmit ready. If you forget to connect the RX system control line, it all just stays safely in TX mode and you would notice no RX antenna. If you lose the 12V for the protection, it all stays in TX mode. This way you cannot operate without protection. If you do it by a protection system that activates with voltage, control can fail a half dozen ways and you might not know. An additional benefit is when the station is off, the RX antenna is disconnected. If you look at circuits in things like the MFJ1025, you will see both a protection circuit (a fuse lamp and diodes) and a relay that connects the radio to the antenna and disconnects the receive function with any loss of relay voltage. We never want a protection relay that activates by application of protection relay coil voltage. The whole problem is solved by just buying one of the many dozens of fairly fast relays. It's easy to find things in the 2-3 millisecond range for less than $3. The only issue is if the radio sequencing is good. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Hello to All; Many years ago Alpha used a very nice QSK sequencing circuit for the Alpha 77, NOT 77DX,D,SX, just the plain 77 ( 1971). It used a RJ1a and a reed-relay, a couple of diodes and a resistor. It was powered with 55 volts. Worked very good and I have the diagram. I have used it for years at 1.5 kW and no problems. 73 de Price W0RI On Sunday, August 30, 2015 7:01 PM, Tom W8JI w...@w8ji.com wrote: I'm not sure goosing the pull-in voltage is always a good idea. It may shorten the initial closing time a bit, but (depending on the relay) it can aggravate contact bounce, doing more harm than good. It also stresses the relay. Done properly, it doesn't hurt a thing. The proper way is to use current limiting. It is safe to run 50 volt supplies on most 12 volt relays, but there is a point of diminishing returns on speed. The high initial voltage ramps up the magnetic field faster, but it does not cause excessive heat or current. This is because the relay starts at near zero mA from inductance. None of this matters, though. Using a relay on make for protection is a bad idea. The de-active state should be used for protection, and the active energized state used to allow RX. _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Mike, The Array Solutions device also uses the transformers to increase the voltage at the diodes then steps it back down which means that the diodes are not doing their limiting at 50 ohms. Therefore, your set of 2 series diodes or even one diode each direction is limiting at a higher power level than the Array Solutions device. From the QST article. The transformer increases the voltage level to allow limiting by a pair of back-to-back diodes and then another transformer matches the output to a 50 ohm receiver input. Jim - KR9U -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Mike Waters Sent: Sunday, August 30, 2015 6:23 PM To: mar...@centrum.cz Cc: topband Subject: Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector) That's similar to mine, but mine has two 1N4148 diodes in series, back-to-back, total of four diodes. However, after I did that, I got to thinking that it would be better with only two. Or that there was no need for four. (Don't ask me to explain, it's been a long time since I've thought about that.) 73, Mike www.w0btu.com On Sun, Aug 30, 2015 at 5:00 PM, Martin Kratoska mar...@centrum.cz wrote: Array Solutions offers a 'RX Front End Protector' based on back-to-back 1N4148 diodes. Schematic: http://www.ok1rr.com/public/rxfep.png _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Perhaps common-mode isolation of currents induced in the antenna coax shield?? Charlie, K4OTV Lee K7TJR k7...@msn.com wrote: Hmmm, I wonder why the Array Solutions circuit board picture shows MCL 1:1 transformers. Sounds fishy to me. Even the waveform pictures show clipping at a 1:1 with one diode voltage. Hmmm? Lee K7TJR _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Well, that's certainly true, Lee. I was just wondering aloud, if the transformers were indeed 1:1, if the point might be common-mode isolation like we work to achieve in the transformers of our flag, pennant and KAZ antennas - although in those cases the matching transformer also matches the 50/75 ohm feedline to a higher impedance of 800-1000 ohms. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Lee K7TJR Sent: Monday, August 31, 2015 12:17 AM To: topband@contesting.com Subject: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector) Sorry Charlie, I don't think I made my thoughts very clear. James was quoting from a QST article that there was an impedance transformation because of the transformers. This was to make a higher voltage at the diodes. My point was that if the transformers being used on their circuit board are 1:1 then there is no impedance transformation and the diodes are fed with the straight RF from the RX antenna at the 50 ohm level. The design must have changed after the QST article or something. The QST description is incorrect if they are using 1:1 transformers as shown in their circuit board pictures. Lee K7TJR _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Since I am the original reason that Gary KD9SV built the first Front End Saver device after we determined why I blew the front end many many years ago of my IC-765 radio. I thought I might add one more very important thing to what ever version of a Front End saver you guys decide to buy or build. In all of Gary KD9SV's many boxes he builds Your Amplifier is prevented from operating if the box fails for any reason. If a relay fails or there is no power to the box regardless of what happens then No Amplifier. Meaning regardless of the failure the max your going to have out there from transmit antenna to receive antenna is whatever your 100 watt radio will do. Most likely not enough to smoke the Pre-Amp and or the Radio. So please be sure to add that item to your version of the FES. John k9uwa John Goller, K9UWA Jean Goller, N9PXF Antique Radio Restorations k9...@arrl.net Visit our Web Site at: http://www.JohnJeanAntiqueRadio.com 4836 Ranch Road Leo, IN 46765 USA 1-260-637-6426 _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Sorry Charlie, I don't think I made my thoughts very clear. James was quoting from a QST article that there was an impedance transformation because of the transformers. This was to make a higher voltage at the diodes. My point was that if the transformers being used on their circuit board are 1:1 then there is no impedance transformation and the diodes are fed with the straight RF from the RX antenna at the 50 ohm level. The design must have changed after the QST article or something. The QST description is incorrect if they are using 1:1 transformers as shown in their circuit board pictures. Lee K7TJR _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
I believe the point of having the transformers in their circuit is to limit the maximum output. A transformer (ferrite in this case) can only output whatever maximum current determined by the core saturation level. They are relying on this property of the transformers to limit the current into the clipping diodes. I believe it was ICE that came up with this technique sometime way back. The diodes set the voltage level of clipping and the transformers limit the maximum current or power into the diodes. The combination realizes a somewhat soft clipping level with a fixed maximum output. Common mode isolation comes for free along with the design. Lee K7TJR _ Topband Reflector Archives - http://www.contesting.com/_topband
