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Transmitter filter relay switching?
This is with regards to a medium-power (~50W) CW transmitter that I am
building for 40, 20, 15, & 10m. I would like to use relays to switch the output filters, but have no idea what kind of relay I will need. Dr Sabin mentioned that a high-quality relay is required (http:// http://www.google.com/url?url=http:/...Ii0baYXpyphcAw ) but I have been unable to find anything specific. Could anybody please direct me to a resource that would help me answer this question? Thank you very much. For reference, the transmitter is a redesign of the classic '60s "inexpensive 75W transmitter", originally by Lew McCoy (I believe), one version of which can be found at (http://www.mines.uidaho.edu/ ~glowbugs/inexpensive75wattxmitter.pdf ). It is a simple crystal- controlled 6AG7 followed by an 807 amplifier at 75W input (50W output). The filters are from Ed Wetherhold's article- (available at http://www.arrl.org/tis/info/pdf/9902044.pdf ) 7th order "Chebyshev With Added Zero" to give better second harmonic attenuation. Best regards, Ross, NS7F |
#2
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Transmitter filter relay switching?
On Feb 17, 11:25*am, "Ross, NS7F" wrote:
This is with regards to a medium-power (~50W) CW transmitter that I am building for 40, 20, 15, & 10m. I would like to use relays to switch the output filters, but have no idea what kind of relay I will need. Dr Sabin mentioned that a high-quality relay is required (http://www.google.com/url?url=http:/...f03/t/3d5e036f... ) but I have been unable to find anything specific. Could anybody please direct me to a resource that would help me answer this question? Thank you very much. For reference, the transmitter is a redesign of the classic '60s "inexpensive 75W transmitter", originally by Lew McCoy (I believe), one version of which can be found at (http://www.mines.uidaho.edu/ ~glowbugs/inexpensive75wattxmitter.pdf ). It is a simple crystal- controlled 6AG7 followed by an 807 amplifier at 75W input (50W output). The filters are from Ed Wetherhold's article- (available athttp://www.arrl.org/tis/info/pdf/9902044.pdf) 7th order "Chebyshev With Added Zero" to give better second harmonic attenuation. Best regards, Ross, NS7F My friend used to do something similar at the antenna and using SPST contacotrs that were used to switch an air conditioner compressor on and off. Three of these could easily fit under a Pi-net coil. Ill try to find picks and part numbers. Jimmie |
#3
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Transmitter filter relay switching?
On Tue, 17 Feb 2009 08:25:16 -0800, Ross, NS7F wrote:
This is with regards to a medium-power (~50W) CW transmitter that I am building for 40, 20, 15, & 10m. I would like to use relays to switch the output filters, but have no idea what kind of relay I will need. Dr Sabin mentioned that a high-quality relay is required (http:// http://www.google.com/url?url=http:/...om/g/d5a7ff03/ t/3d5e036fddd024eb/d/355b6c8e64361096%3Fhl%3Den%26ie%3DUTF-8%26oe%3Dutf-8% 26q%3Dsabin%2Brelay%2Bband%2Bfilter%23355b6c8e6436 1096&ei=u-SaSdCSGIOU- wGVlcGnBQ&sa=t&ct=res&cd=1&source=groups&usg=AFQjC NHG7VKozzInElLsIi0baYXpyphcAw ) but I have been unable to find anything specific. Could anybody please direct me to a resource that would help me answer this question? Thank you very much. For reference, the transmitter is a redesign of the classic '60s "inexpensive 75W transmitter", originally by Lew McCoy (I believe), one version of which can be found at (http://www.mines.uidaho.edu/ ~glowbugs/inexpensive75wattxmitter.pdf ). It is a simple crystal- controlled 6AG7 followed by an 807 amplifier at 75W input (50W output). The filters are from Ed Wetherhold's article- (available at http://www.arrl.org/tis/info/pdf/9902044.pdf ) 7th order "Chebyshev With Added Zero" to give better second harmonic attenuation. Best regards, Ross, NS7F I've found that for RF below 2m, about any really will work within reason. Bad relays to use are reed relays or any relays where the RF leads are wrapped or parallel with large surfaces. Yaesu and Icom use smaller DIP based relays just like the ones at radio shack. I would simply calculate the current at the power level you need and use the appropriate relay. I use "KP" relays all the time. even in the 2m band. |
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