Topband: To clamp or NOT...that IS the question
Hi Tom, You said : "What works OK in one place will almost always not work the same in another" You just confirmed what I was trying to say, and that is in some applications it just might work. If I had not tried simple clamp diodes in my application I would have made my system complicated via relays and control signals when they really were not needed. Same thing goes for the W7IUV preamp, if I had not tried using it without a front end saver I would have gone and spent money and complicated my system when it was not really needed. But after reading that W7IUV did not use a front end saver with his preamp I tried the same and could not be happier with the results. I'm suggesting that Jim try clamp diodes if he so desires and if he notices intermod then he should remove them and try a more complicated/elegant solution. Don (wd8dsb) _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: 9Y 160
Saw this on another reflector. Look for 9y4W Friday and Saturday nights. Folks, I am in Tobago and I have been monitoring the condx on 160 for the last few days. After the turbulences last week conditions have improved significantly and I was able to make a number of QSOs into Europe last night. I will check the next two nights over the weekend as well. Let’s hope for the best. Please call with moderate CW speed… you are not as loud as you may think you are ;-) 73 Andy 9Y4W Bernie McClenny, W3UR Editor of The Daily DX, The Weekly DX and How's DX? Two week trial - http://www.dailydx.com/trial.html https://twitter.com/dailydx 410-489-6518 _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: To clamp or NOT...that IS the question
I use protection diodes on the front end of my W1FB preamps (as well as before an IC amp in the preamp, and on the output of the preamp) and have never been able to detect receiver performance degradation on 160 meters due to the clamping diodes (had to include the diode clamps before the IC amp in the W1FB preamp to prevent continuous failures of this IC when transmitting). What works OK in one place will almost always not work the same in another. Intermod is a function of the TOTAL voltage of all the signal sources at the point where the diodes are. This is why some systems work with diodes, and some systems completely fall apart. The problem can come from a hundred small signals, each signal far below threshold, or just one large signal near threshold. Impedance also matters, both in band and out-of-band. A regular diode is about .5 volts or before peak it starts to generate junk, some are less and some slightly more. Assuming .5 volts peak, that would be .35 volts RMS. .35V RMS is only 4 dBm at 50 ohms. This would be the peak composite voltage level, not the single tone or composite power calculated from the simple sum of powers. This paper would apply: www.minicircuits.com/app/AN60-037.pdf _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: To clamp or NOT...that IS the question
Hi Jim and gang, I use protection diodes on the front end of my W1FB preamps (as well as before an IC amp in the preamp, and on the output of the preamp) and have never been able to detect receiver performance degradation on 160 meters due to the clamping diodes (had to include the diode clamps before the IC amp in the W1FB preamp to prevent continuous failures of this IC when transmitting). On the rare occasion (only happens during a contest) when I've heard what sounds like ever so slight intermod I switch to my TX vertical for RX and the odd phenomena has always still been present so I've never been able to find fault with my added diode protection system. I have half size pennants feeding my preamp and they have an approximate gain of -46 dbi, and suspect this is the key to my success with diodes as clamps (very low input levels from my RX antennas). Therefore I certainly don't agree with avoiding diode clamps 100% of the time, as I believe they should be considered on a case by case basis depending on the gain of your RX antenna, etc. I also have W7IUV preamps and don't use diode clamps with them at all since their front ends appear bullet proof based on the transistor used. P.S. I only run 100 watts output, but my TX vertical is within 30 or 40 feet of my RX pennants. 73, Don (wd8dsb) _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: FW: KD9SV Products
Congratulations Gary You have excellent products. Sometimes need good Marketing to the people know them 73, Jorge CX6VM/CW5W -Mensaje original- De: Topband [mailto:topband-boun...@contesting.com] En nombre de kd9sv Enviado el: viernes, 17 de enero de 2014 04:33 p.m. Para: topband@contesting.com Asunto: Topband: FW: KD9SV Products The first time it didn't post so trying the other email address.de gary, kd9sv _ From: kd9sv [mailto:kd...@comcast.net] Sent: Thursday, January 16, 2014 3:11 PM To: Topband-Bounces (topband-boun...@contesting.com) Subject: KD9SV Products Just a quick note to let all the Top Band enthusiasts know that DX Engineering now has exclusive rights to all of KD9SV Low Band Products. Thanks and best 73 and DX in the upcoming contest. Gary, kd9sv --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: FW: KD9SV Products
The first time it didn't post so trying the other email address.de gary, kd9sv _ From: kd9sv [mailto:kd...@comcast.net] Sent: Thursday, January 16, 2014 3:11 PM To: Topband-Bounces (topband-boun...@contesting.com) Subject: KD9SV Products Just a quick note to let all the Top Band enthusiasts know that DX Engineering now has exclusive rights to all of KD9SV Low Band Products. Thanks and best 73 and DX in the upcoming contest. Gary, kd9sv --- This email is free from viruses and malware because avast! Antivirus protection is active. http://www.avast.com _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: To clamp or NOT...that IS the question
Hello Jim, 3x fast relays, 2x switching transistors, 3x resistors and box with connectors... You have KD9SV front-end saver. No diodes, no RX performance degradation. I never had issue on my K3 with KD9SV saver in ext.RX front-end. Let me know I will send You the drawing. Hope it helps my friend, best regards, 73 - Petr, OK1RP http://160mband.blogspot.com On Fri, Jan 17, 2014, at 06:37 PM, James Rodenkirch wrote: > > > > A friend of mine is building me a switching arrangement with a reed relay > to switch between my transmit antenna and a receive delta loop to the one > antenna input for my Ten Tec Jupiter (I operate at QRP levels for > contests). > As an added measure of protection for the KD9SV low noise pre-amp I use > with my 160/80 delta loop antenna, he believes clamping the RX antenna > port or shunting to ground during TX sounds like a nice thing. But, he's > seen arguments that clamping receiver input with diodes degrades the > receiver performance. He find this believable, but I don't know how true > it is, e.g., he knows KD1JV claims his RX performance is achieved by > using 2N7000 FETs to do T/X switching. > He has a bunch of 2N7000 and will probably use one to turn on the relay. > He can turn on another one along with the relay driver that will shunt > the RX antenna port to ground but he wonders if that would degrade > receiver performance. > Thoughts? 72/72, Jim Rodenkirch K9JWV > > > _ > Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Re: Topband: To clamp or NOT...that IS the question
Not lkely, I think, Jim. I presume the FET would have some significant bias ( perhaps 5-12 V) on its drain when it is not conducting, so relatively large signals are not very likely to produce non-linearities and intermod or cross modulation as the diodes might. My TCW. Of course on could also add an additional relay (perhaps mercury wetted) right at the RX port to clamp it when thetX is enabled. 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of James Rodenkirch Sent: Friday, January 17, 2014 12:38 PM To: Top Band Contesting Subject: Topband: To clamp or NOT...that IS the question A friend of mine is building me a switching arrangement with a reed relay to switch between my transmit antenna and a receive delta loop to the one antenna input for my Ten Tec Jupiter (I operate at QRP levels for contests). As an added measure of protection for the KD9SV low noise pre-amp I use with my 160/80 delta loop antenna, he believes clamping the RX antenna port or shunting to ground during TX sounds like a nice thing. But, he's seen arguments that clamping receiver input with diodes degrades the receiver performance. He find this believable, but I don't know how true it is, e.g., he knows KD1JV claims his RX performance is achieved by using 2N7000 FETs to do T/X switching. He has a bunch of 2N7000 and will probably use one to turn on the relay. He can turn on another one along with the relay driver that will shunt the RX antenna port to ground but he wonders if that would degrade receiver performance. Thoughts? 72/72, Jim Rodenkirch K9JWV _ Topband Reflector Archives - http://www.contesting.com/_topband _ Topband Reflector Archives - http://www.contesting.com/_topband
Topband: To clamp or NOT...that IS the question
A friend of mine is building me a switching arrangement with a reed relay to switch between my transmit antenna and a receive delta loop to the one antenna input for my Ten Tec Jupiter (I operate at QRP levels for contests). As an added measure of protection for the KD9SV low noise pre-amp I use with my 160/80 delta loop antenna, he believes clamping the RX antenna port or shunting to ground during TX sounds like a nice thing. But, he's seen arguments that clamping receiver input with diodes degrades the receiver performance. He find this believable, but I don't know how true it is, e.g., he knows KD1JV claims his RX performance is achieved by using 2N7000 FETs to do T/X switching. He has a bunch of 2N7000 and will probably use one to turn on the relay. He can turn on another one along with the relay driver that will shunt the RX antenna port to ground but he wonders if that would degrade receiver performance. Thoughts? 72/72, Jim Rodenkirch K9JWV _ Topband Reflector Archives - http://www.contesting.com/_topband
