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Everyham's Amp

Jan 19th, 12:58

effirlem

Joined: Mar 23rd 2013, 12:22
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I read the article about building an amp that was in the January QST. I even ordered the 2014 handbook so that I could read the article there. This got my interest up to point that I am now ordering parts to build my own amp. In the parts list of "Everyham's Amplifier" there is no mention of "K1 or K2". And now my question. What is the proper relay to use and where can I get one?

Mel...
Jan 20th, 15:26

W1VT

Joined: Apr 4th 1998, 00:00
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Mouser 653-G6A-274P40-DC12
This relay is used by Phil AD5X as the input relay.
HF Amplifier QSK Switch
http://www.ad5x.com/articles.htm

Lots of choices for the output relay, depending on your needs.
An 10-15A open frame relay is the cheapest option--which was reliably used in many amplifiers, including the Heathkit SB-220.
Many hams will upgrade this to a vacuum relay when they need fast switching speeds--a QSK modification is typically done to allow advanced CW operators to hear stations while they are sending. Coaxial relays are designed for RF switching and offer improved SWR performance at 10M, but for many hams, they are too costly, unless they get a great deal on the surplus market.

Zack W1VT
ARRL Senior Lab Engineer
Jan 21st, 04:50

effirlem

Joined: Mar 23rd 2013, 12:22
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Thanks Zack, this will give me a place to start looking. I have some 12 volt relays but I believe that the current rating on them is too small, 3 amps.

Mel...
Jan 21st, 19:16

W1VT

Joined: Apr 4th 1998, 00:00
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W8ZR asked about an inexpensive RF capable relay on the Towertalk forum and got this recommendation

Tyco/Shrack RTB14012

http://lists.contesting.com/_towertalk/2007-12/msg00252.html
Jan 22nd, 05:04

effirlem

Joined: Mar 23rd 2013, 12:22
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Total Posts: 0
Thanks again for another lead. I have some of the automotive relays that they talk about in the link, but I am leery about using them in the amp.

Mel...
Mar 4th, 14:28

effirlem

Joined: Mar 23rd 2013, 12:22
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OK, got the relay situation straightened out. Bought a relay off Ebay that is a replacement for the relay in a Heathkit SB200. Now I have another concern. In the PDF of the "Every Ham's Amp", the schematic of the power supply shows one leg of the transformer connected to the diodes at a point where they are "+" to "-". The other leg of the transformer is connected the the capacitor bank where they are "+" to "+". Am I missing something here? Every other schematic that I have looked at says that they should be "+" to "-".
Mar 4th, 15:39

W1VT

Joined: Apr 4th 1998, 00:00
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Figure 5 is a voltage doubler circuit. It is usually cheaper to use a voltage doubler circuit than to get a transformer that will allow you to use more conventional rectifier circuits when you need the high voltages required for amplifiers.

The Heathkit SB-220 also uses a voltage doubler circuit, but with a special low resistance windings that allows the use of a full wave, rather than a half wave circuit. Voltage regulation will suffer if you try to use a full wave circuit with a typical transformer.

Zack Lau W1VT
ARRL Senior Lab Engineer
Mar 4th, 19:00

effirlem

Joined: Mar 23rd 2013, 12:22
Total Topics: 0
Total Posts: 0
Thanks for the info Zack. I see where the doubler in Fig.2 is basically the same as the one in Fig. 5. Never thought about half wave/full wave. So I will just proceed with my project.

Mel
WD8NNL

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