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 <[email protected]> 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 !!! >> >> 73....Douglas, 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" <[email protected]> >> To: "Charles Cu nningham" <[email protected]>; "'topBand List'" >> <[email protected]> >> 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
