Re: [Elecraft] Fw: Fw: Don't have a 50W dummy load
Hi bob - Your post was far from stupid. On this reflector we welcome all questions of this type. Please feel free to post as ask as needed. You will certainly get a lot of responses, some closer to the mark than others. At least one will be exactly what you are looking for. We certainly have an verbose group though! I never expected to see so many dummy load emails in my inbox.. So let's close this thread at this time inthe interest of keeping list volume under control. 73, Eric List Moderator elecraft.com On 3/25/2015 5:51 PM, Bob Gibson via Elecraft wrote: You guys are right!! SORRY FOR MY STUPID POST!! Sixty years ago I did not have money for a dummy load..ENJOY 73s Bob W5RG - Forwarded Message - From: Fred Jensen k6...@foothill.net To: elecraft@mailman.qth.net Sent: Wednesday, March 25, 2015 6:41 PM Subject: Re: [Elecraft] Fw: Don't have a 50W dummy load Ummm ... several reasons. Resistance component of an incandescent bulb impedance varies with the temperature [brightness] of the filament. They are also somewhat reactive. Push-pull vacuum tubes and link coupling didn't care about SWR, I don't even remember the term in the ham lexicon until the Pi-network and 50 ohm output was invented. They're also not very good at the dummy part. N6BT, of Force 12 fame, is fairly famous for his phased illuminator, 3 300 watt bulbs mounted on his deck railing in a V arrangement on which he worked all continents. More than once I made contacts while using a 100 watt bulb as my dummy load. If you're going to use the paralleled metal film resistor construction method, be sure to keep the resistor leads short and spaced them from each other. Lead inductance will start to become a factor on 6 m and up. I built mine with 40 2K 2W resistors and it works find at 100W if used intermittently. It's air cooled. Don't know how much putting it in oil would improve the dissipation. 73, Fred K6DGW - Northern California Contest Club - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015 - www.cqp.org On Mar 25, 2015, at 14:25, Bob Gibson via Elecraft elecraft@mailman.qth.net wrote: HOW ABOUT A LAMP WITH 100 WATT BLUB, THATS ALL US OLD GUYS HAD! 73s Bob W5RG __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to w...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to elist_c...@elecraft.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
[Elecraft] Fw: Fw: Don't have a 50W dummy load
You guys are right!! SORRY FOR MY STUPID POST!! Sixty years ago I did not have money for a dummy load..ENJOY 73s Bob W5RG - Forwarded Message - From: Fred Jensen k6...@foothill.net To: elecraft@mailman.qth.net Sent: Wednesday, March 25, 2015 6:41 PM Subject: Re: [Elecraft] Fw: Don't have a 50W dummy load Ummm ... several reasons. Resistance component of an incandescent bulb impedance varies with the temperature [brightness] of the filament. They are also somewhat reactive. Push-pull vacuum tubes and link coupling didn't care about SWR, I don't even remember the term in the ham lexicon until the Pi-network and 50 ohm output was invented. They're also not very good at the dummy part. N6BT, of Force 12 fame, is fairly famous for his phased illuminator, 3 300 watt bulbs mounted on his deck railing in a V arrangement on which he worked all continents. More than once I made contacts while using a 100 watt bulb as my dummy load. If you're going to use the paralleled metal film resistor construction method, be sure to keep the resistor leads short and spaced them from each other. Lead inductance will start to become a factor on 6 m and up. I built mine with 40 2K 2W resistors and it works find at 100W if used intermittently. It's air cooled. Don't know how much putting it in oil would improve the dissipation. 73, Fred K6DGW - Northern California Contest Club - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015 - www.cqp.org On Mar 25, 2015, at 14:25, Bob Gibson via Elecraft elecraft@mailman.qth.net wrote: HOW ABOUT A LAMP WITH 100 WATT BLUB, THATS ALL US OLD GUYS HAD! 73s Bob W5RG __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to w...@yahoo.com __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Fw: Fw: Don't have a 50W dummy load
Oh Shucks at some point elmers all used a lamp for a dummy load back in the day with Pi tuning you could transfer a lot of your output to a lamp,,, on 6 meters , as I recall ,, parts of the filament would be brighter than other parts we could talk about RF burns HAR Bob K3DJC On Thu, 26 Mar 2015 00:51:58 + (UTC) Bob Gibson via Elecraft elecraft@mailman.qth.net writes: You guys are right!! SORRY FOR MY STUPID POST!! Sixty years ago I did not have money for a dummy load..ENJOY 73s Bob W5RG Subject: Re: [Elecraft] Fw: Don't have a 50W dummy load Ummm ... several reasons. Resistance component of an incandescent bulb impedance varies with the temperature [brightness] of the filament. They are also somewhat reactive. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
Re: [Elecraft] Fw: Fw: Don't have a 50W dummy load
On Wed, Mar 25, 2015 at 8:11 PM, riese-k3...@juno.com wrote: ...at some point elmers all used a lamp for a dummy load back in the day with Pi tuning... - Yep, back in 1958 I loaded up my first home-brew transmitter (6146, of course) with a 100W bulb and I am one of the many hams who can claim to have made a qso using the bulb for an antenna, on 40M cw. The output capacitor of my pi-net was one of those double-gang 365 uuf per gang broadcast receiver jobbies. Tony KT0NY __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
