Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Makes sense, Lee Charlie -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Lee K7TJR Sent: Monday, August 31, 2015 12:44 AM To: topband@contesting.com Subject: 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 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
FYI - The S-QSK boards are now spoken for. Thanks for the replies. Paul, W9AC _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
Another option for "front end" sequencing control involves the use of a microcontroller to time R=>T and the the reverse switching events. For the past two years, I've been using an Arduino Nano-based controller to manage amplifier switching as well as a PIN diode T/R switch to silently control RF switching of a Drake C line. To date, RF ingress has not been an issue. The Nano's I/O is completely optically isolated with the use of external photo transistors and photo-relays. The photo-relays are used to drive heftier devices like vacuum relays, PIN diodes, and Zener bias switching. The board has an integrated RF sample port such that switching events cannot occur in the presence of RF. Where RF needs to be sampled away from board, an external RF sampling board is used. In both sampling versions, RF is sensed down to less than 50 mW of power. The board samples up to 4 inputs (including RF presence) and switches a maximum of 8 output channels. To the point of this message topic, the same board also emulates the KD9SV "Front End Saver." On my QRZ.com page, I have written the C++ code to start basic control of the FES. Need more devices switched or need to conveniently change delay times? Just activate another port by modifying the software. Or, change switch times in 1 ms increments with a simple software edit. The board includes two optional relay coil accelerator circuits, and includes W8ZR's idea of using a small muRata DC-DC converter, bootstrapped to the +12V supply to generate +24V to power common vacuum relays. More board info is available in the 2014 ARRL Handbook or on my QRZ.com page. One only populates the parts on the board of interest. For example, if relay coil acceleration is not of interest, the parts are omitted and does not affect the rest of the board's operation. I still have a few bare boards remaining. PM if there's an interest. Paul, W9AC _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ??? (RX Front End Protector)
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." Here are the problems: 1.) The peak voltage at 75 ohms and 100 mW (20 dBm) is almost 4 volts. 2.) Receiver impedances are all over the place. I've seen them as low as 20 ohms, and as high as 150 ohms. Most of those I measured are closer to 40-80 ohms. 3.) The voltage at the diodes is the vector sum of all signal voltages. If you have a wide band antenna, there can be considerable net voltage from many hundreds of small signals summing. I can light a 12V filament lamp dull red off my Beverages at night, and I am 30-40 miles from the closest active AM BCB station. It is the sum of hundreds of signal from hundreds of miles that is the problem. 4.) Receivers limit the signal range to something centered around the selected band, so they don't see that wide swath of summed voltages. The diodes in a limiter do. 5.) The miniciruits transformer mix and create IMD, and are very sensitive to dc current, even at pretty low levels. The point where they add IMD is so unpredictable compared to limiting, they are not a good choice in receive systems. This is especially true when you have no idea how many hundreds of signals that transformer has to process at the randowm receive systems in the field. (I tried them for antenna and amplifiers and abandoned them back in the 70's. My eight element look antenna array initially used them, but the LORAN signals and AM BCB signals killed them). The last thing in the world useful for RX protection is a soft limiter. It has to be a hard clamp, set just safely below whatever RX port voltage might threaten equipment. No clamping or distortion until that point. Premature limiting does absolutely no good, and potentially many bad things. If you pay thousands of dollars for a receiver that has a wide spaced dynamic range of over 100 dB, why would want to make it into 1970's Yaesu FT101 performance with a limiter? Remember, this is not a few signals in the passband. The diodes are pre-filter, and they clip at the sum of all the hundreds of small signals across them. If you use diodes, they become more acceptable is a modest amount of pre-filtering is used to keep needless signals (especially the AM BCB) out. 73 Tom _ 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: 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: 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 ???
than the noise on 80m or 40m. Guess which weak signal may show up on that day, Africa? VK0? That DX expedition you need for a new one... you bet. The other 95 % of the time, the NF has no SNR impact if the signal is 10db above the noise floor, including the internal noise. The degradation is approximately 10% for a bad preamp and 1 % for a good preamp, it actually does not mean anything. The preamp just reduces the damage of the noise problem on the electronic circuit, it does not increase anything else, 10% reduction is, in practice, the same as 1% or 0.1%. The gain I sonly important when you cascade the preamp with the radio, the noise contribution of the radio will be its NF divided by the gain the preamp in front of the radio. A radio with a 20 db. NF, with a 20 db. gain preamp in front, will impact the NF of the system by 20/20 = 1db, so, if your preamp has 2 db. NF on 160m, the system will have a 3 db. NF. The trick is that 95 % of the time you won't need the preamp at all, it will only be needed in that 5% or 1% of the time to work that weak signal from Africa for a new one on 160m.!! 6- Timing is a really huge problem and a sequencer is also a must. Here is a very simple TX/RX antenna sequencer that I have been using for several years that works very well. For CW the fix is very simple, use the sequencer controlling your amplifier and preamp, and use a new design CW electronic key that delays the dits and dots 30ms or more, 80ms to 100ms is a good choice to work up to 25 wpm. That simple feature grounds the PTT and waits all relays to bounce, after all is stable, it will start sending the CW key to the radio. Also, most new CW circuits has tail delay to wait the CW kick back. The small NEC AE2 relays or equivalent are fast enough and also very small. The ideal relay is the G6K with 80 db. isolation at 2MHz Douglas, my suggestion for you is that: use that out-put BNC after the internal TR/RX relay, add two relays sequencer like the G3SEK bellow http://www.ifwtech.co.uk/g3sek/dx-book/sequencer/ Dont mess with open frame relays not designed for RF, the lack of shield you kill your RX performance. Use tin steel plated boxes, they are easy to find on any food can, the aluminum enclosure does not cut magnetic field, it also does not help to cut noise from switching power supply or PC monitors. A shield and a good band pass filter will help you a lot . Based on my experience with EWE FLAG's and WF in the last 10 years, I recommend you to use no more than 10 db. gain preamp for single EWE, FLAG and Beverage antennas (all are vertical RX antennas). For dual phased EWE, FLAGS or vertical WF, 20 db. gain is enough (use the internal preamp only during very quiet days). A NORTON preamp (K8ZOA) is the only preamp that I recommend, it has low NF and high IP3. For horizontal loops 20 db. gain is enough, and for phased horizontal loops, like HWF, a 40 db. gain preamp is necessary. KD9SV has a new preamp with 40 db. gain and 1dB NF that I recommend for phased horizontal loops. Also try to use a delay CW electronic key like K1EL winkey (the new K16 IC is just US$8) or any new design with delay and tail adjustment. Several logging programs also have CW machine with delay feature. My 20 cents. N4IS JC -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Douglas Ruz (CO8DM) Sent: Sunday, August 30, 2015 8:42 AM To: Tom W8JI w...@w8ji.com; Charles Cu nningham charlie-cunning...@nc.rr.com; 'topBand List' topband@contesting.com 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
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
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
Topband: KD9SV-OK1RR relays ???
Hi Martin, OK1RR, I tried email direct to you but it was not possible. I am sorry about the other member of the list. It is about the FRONT END SAVER relays: I have two different relays here and i would like to know if i can use one of them in your design: I have HFD2 Subminiature DIP relay: -Matching standard 16 pin socket. -DPDT -100 million operations - Operate time 4ms and release time 3ms. -Capacitance: Contact to coil 5pF and contact set to contact 1,5 pF I have also HFD41 relay: -SPDT relay -10 million operations -Operation time 10mS -Not sure about capacitance. Maybe i have to RE-DESIGN the PCB but that is very easy. Any idea???...Thanks, 73Douglas, CO8DM _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
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? It needs a preamp saver or a receiver antenna saver, not a front end saver. Any old relay will not work. Here is what the sequence is: 1.) The radio antenna port is connected through a small relay to the receive preamp output, or to the receive antenna 2.) The key is closed 3.) At time X, after the key is closed, something tells the receiver relay to release 4.) At the same time as the key is pressed, something tells the transmitter to transmit. Let's call this delay time Y. Now this is where the problem is. Many radios, especially the less expensive radios with a single antenna, have a Y time as short as X time. Some have X a little longer than Y, some have Y a little longer than X. There is no guarantee without looking at the radio on ALL modes if X time is shorter than X. Almost all radios are not 10mS, the relay time you suggested as a limit. Almost all radios are shorter than that, and some actually transmit while the external relay line is held low. There is an additional problem in a few radios. There are a few radios that tell the relay control line to release while they are still transmitting. At the end of a transmission, when you stop transmitting, a few radios will actually turn the external circuits off **before** they stop putting out RF power. I actually had to add a RF interlock in T-R relays for amplifiers just for those radios. Any relay used for this application should be as fast as possible. It should NOT have a diode across the coil, because that slows the release time down considerably. I would say the safe minimum speed for most radios would be about a 5 mS relay transfer, including bounce. A few radios will be worse than that, and have almost no delay. They would require a very fast relay, or a sequencing system. Some radios are designed so poorly they tell the external things to transfer while RF is present. Those radios cannot be fixed without external interlock systems. By the way, if this does not damage the RX system, it will cause contact spark clicks. It will also fold some radios back into SWR protect because the relay transfers with TX RF applied. The crummy interface timing in radios has been a nightmare ever since the first transceiver came out, and continues to be a problem today. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Hi Douglas, I am sorry to tell you that none of the relays you have is good for the front end saver. They are usual small signal relays but a reed relay should be used. The most important thing is not the capacitance (assumed that the front end saver is used on 160, 80 and possibly 40 m), but the switching times. I would recommend to take part in a group buy. AFAIK David, G3WGN, organized a group buy/PCB fabrication of 80 units, possibly he may have rests for sale. 73, Martin, OK1RR Dne 29.8.2015 v 18:15 Douglas Ruz (CO8DM) napsal(a): Hi Martin, OK1RR, I tried email direct to you but it was not possible. I am sorry about the other member of the list. It is about the FRONT END SAVER relays: I have two different relays here and i would like to know if i can use one of them in your design: I have HFD2 Subminiature DIP relay: -Matching standard 16 pin socket. -DPDT -100 million operations - Operate time 4ms and release time 3ms. -Capacitance: Contact to coil 5pF and contact set to contact 1,5 pF I have also HFD41 relay: -SPDT relay -10 million operations -Operation time 10mS -Not sure about capacitance. Maybe i have to RE-DESIGN the PCB but that is very easy. Any idea???...Thanks, 73Douglas, CO8DM _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Doug - 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 you are adding an outboard relay keyed from the amp control line of the FT-747 to allow you to have separate transmit and receive antennas, that's great. Any old relay with less than 10ms make/break time will work fine there. You still don't need a front end saver, because your rig still cannot be hooked to both transmit and receive antenna at same time. Tim N3QE On Sat, Aug 29, 2015 at 12:15 PM, Douglas Ruz (CO8DM) co...@frcuba.co.cu wrote: Hi Martin, OK1RR, I tried email direct to you but it was not possible. I am sorry about the other member of the list. It is about the FRONT END SAVER relays: I have two different relays here and i would like to know if i can use one of them in your design: I have HFD2 Subminiature DIP relay: -Matching standard 16 pin socket. -DPDT -100 million operations - Operate time 4ms and release time 3ms. -Capacitance: Contact to coil 5pF and contact set to contact 1,5 pF I have also HFD41 relay: -SPDT relay -10 million operations -Operation time 10mS -Not sure about capacitance. Maybe i have to RE-DESIGN the PCB but that is very easy. Any idea???...Thanks, 73Douglas, CO8DM _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Tim, Yes, you are absolutely right 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 - Original Message - From: Tim Shoppa tsho...@gmail.com Cc: topBand List topband@contesting.com Sent: Saturday, August 29, 2015 3:05 PM Subject: Re: Topband: KD9SV-OK1RR relays ??? Doug - 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 you are adding an outboard relay keyed from the amp control line of the FT-747 to allow you to have separate transmit and receive antennas, that's great. Any old relay with less than 10ms make/break time will work fine there. You still don't need a front end saver, because your rig still cannot be hooked to both transmit and receive antenna at same time. Tim N3QE _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: KD9SV-OK1RR relays ???
Is there a reason to favor relays over taking a pin diode to ground to short the input during tx? Art NK8X ᐧ On Sat, Aug 29, 2015 at 2:31 PM, Martin Kratoska mar...@centrum.cz wrote: Hi Douglas, I am sorry to tell you that none of the relays you have is good for the front end saver. They are usual small signal relays but a reed relay should be used. The most important thing is not the capacitance (assumed that the front end saver is used on 160, 80 and possibly 40 m), but the switching times. I would recommend to take part in a group buy. AFAIK David, G3WGN, organized a group buy/PCB fabrication of 80 units, possibly he may have rests for sale. 73, Martin, OK1RR Dne 29.8.2015 v 18:15 Douglas Ruz (CO8DM) napsal(a): Hi Martin, OK1RR, I tried email direct to you but it was not possible. I am sorry about the other member of the list. It is about the FRONT END SAVER relays: I have two different relays here and i would like to know if i can use one of them in your design: I have HFD2 Subminiature DIP relay: -Matching standard 16 pin socket. -DPDT -100 million operations - Operate time 4ms and release time 3ms. -Capacitance: Contact to coil 5pF and contact set to contact 1,5 pF I have also HFD41 relay: -SPDT relay -10 million operations -Operation time 10mS -Not sure about capacitance. Maybe i have to RE-DESIGN the PCB but that is very easy. Any idea???...Thanks, 73Douglas, CO8DM _ 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 ???
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
Re: Topband: KD9SV-OK1RR relays ???
Hello all 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. One can also add a few ohms in series with the antenna lead to reduce the requirements for collector current in the saturating switch. That approach should help with the switching speed and contact bounce issues. However, if the radio design is poor and there are T/R sequencing issues - those will require additional means to correct or deal with the improper T/R sequencing problems. The turnoff time for the saturating switch, even at low forced gains should be fast enough to cope with very fast keying speeds. Just a thought. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Saturday, August 29, 2015 6:14 PM To: topBand List Subject: Re: Topband: KD9SV-OK1RR relays ??? 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? It needs a preamp saver or a receiver antenna saver, not a front end saver. Any old relay will not work. Here is what the sequence is: 1.) The radio antenna port is connected through a small relay to the receive preamp output, or to the receive antenna 2.) The key is closed 3.) At time X, after the key is closed, something tells the receiver relay to release 4.) At the same time as the key is pressed, something tells the transmitter to transmit. Let's call this delay time Y. Now this is where the problem is. Many radios, especially the less expensive radios with a single antenna, have a Y time as short as X time. Some have X a little longer than Y, some have Y a little longer than X. There is no guarantee without looking at the radio on ALL modes if X time is shorter than X. Almost all radios are not 10mS, the relay time you suggested as a limit. Almost all radios are shorter than that, and some actually transmit while the external relay line is held low. There is an additional problem in a few radios. There are a few radios that tell the relay control line to release while they are still transmitting. At the end of a transmission, when you stop transmitting, a few radios will actually turn the external circuits off **before** they stop putting out RF power. I actually had to add a RF interlock in T-R relays for amplifiers just for those radios. Any relay used for this application should be as fast as possible. It should NOT have a diode across the coil, because that slows the release time down considerably. I would say the safe minimum speed for most radios would be about a 5 mS relay transfer, including bounce. A few radios will be worse than that, and have almost no delay. They would require a very fast relay, or a sequencing system. Some radios are designed so poorly they tell the external things to transfer while RF is present. Those radios cannot be fixed without external interlock systems. By the way, if this does not damage the RX system, it will cause contact spark clicks. It will also fold some radios back into SWR protect because the relay transfers with TX RF applied. The crummy interface timing in radios has been a nightmare ever since the first transceiver came out, and continues to be a problem today. 73 Tom _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
