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Old February 17th 09, 05:25 PM posted to rec.radio.amateur.homebrew
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Posts: 12
Default 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
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Old February 18th 09, 03:20 AM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Nov 2008
Posts: 77
Default 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
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Old February 21st 09, 09:38 PM posted to rec.radio.amateur.homebrew
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First recorded activity by RadioBanter: Nov 2008
Posts: 23
Default 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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