T-20/ARC-5

ve3lyx
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Re: T-20/ARC-5

Messaggio: #20648 ve3lyx
17/10/2016, 23:36

I have two ARC5 tx. One on 160M and one on 80M. I have installed a Key jack where your blue tag is on one. The other was already done when I bought it. I key the cathode (bypassing the relay but it is still in there) I do not have a MD 7 modulator but do a lot of AM. SO I built a modulator that plugs in the key jack and puts a 6y6 in series with the 1625's cathodes and ground. A 6sl7 controls the 6y6 and amplifies the mic input. It works and while not 100% modulation I can use the radios on AM anytime without any inside mods. If I had a M7 modulator I would use it but in the meantime I can still enjoy them. The circuit is from 1956 ARRL handbook and is simple to build.
donVE3LYX

ve3lyx
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Re: T-20/ARC-5

Messaggio: #21021 ve3lyx
06/11/2016, 4:49

Also, le condesatori di accopiamento will fail . I always replace that with a .01 uf 2kv ceramic. When it goes it will be a phantom failure and you won't know what is wrong. I now replace them as soon as they arrive , before putting power to them. I use the rule I learned when working. "First time , could have happened to anyone. Second time, I forgot. Third time shame on me." There will be no third time here. Now that you know there need be no first time failure . Just replace it
don VE3LYX

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IK0MOZ
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Re: T-20/ARC-5

Messaggio: #21060 IK0MOZ
07/11/2016, 10:31

Referreing to modulation problems for those TX series, following the Don/VE3LYX suggestion I found on the net the 1956 ARRL handbook article. Really very simple and (solved the tubes problem) I am tried to built it for my T-22/ARC-5. Before to start, I should be very interested to know the opinion and comments about this system from the group members. I know that this kind of sets are quite popular and to get the possibility to modulate them without the rare MD-7 should be a wonderfull opportunity. Mario/MOZ

In riferimento alla indicazione di Don ho trovato in rete l'articolo del 1956. L'idea mi sembra ottima. Vorrei sapere che ne pensate. mario
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ImmagineImmagine # ARO 301/0Immagine WS 19 Group # 15 Mario IK0MOZ

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roberto burdese
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Re: T-20/ARC-5

Messaggio: #21067 roberto burdese
07/11/2016, 13:14

" A Simple Grid Modulator",l'ho letto attentamente, meglio di niente, ho anche notato che sulla edizione del handbook 1957, non è più stato proposto, e comunque, "ultima spiaggia" in alternativa alla modulazione di placca e G2, che distingue la serie ARC-5 dal SCR-274. Voglio però aggiungere, che uno dei punti interessanti di questo circuito, è che non richiede di una alimentazione anodica aggiuntiva in quanto questa, è fornita dal circuito modulato. "BR"
ImmagineImmagine # ARO 305/0 Immagine Roberto I0BR

ve3lyx
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Re: T-20/ARC-5

Messaggio: #21088 ve3lyx
08/11/2016, 10:39

I have been using mine successfully for about 5 years. It is a very practical piece of shack equipment.
donVe3LYX

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IW1FQG
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Re: T-20/ARC-5

Messaggio: #21089 IW1FQG
08/11/2016, 11:05

Playing with tube equipment is fun, but I'm always cautiuous ... if not, a piece of shack equipment might turn into a piece of SHOCK equipment! :lol:

73,
Ugo IW1FQG

ve3lyx
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Re: T-20/ARC-5

Messaggio: #21105 ve3lyx
08/11/2016, 18:22

I am always aware of the hazard especially when working with Linear amps. However since this modulator is in the cathode to ground circuit there is some measure of safety. It also steals all its B voltage from the ARC 5 there is a measure of protection there as well. However still all the rules apply. When checking high voltage circuits I often unplug from the PSU and power the B circuit with a 9 volt and clip leads. Much safer then working on a "Hot" radio .
donVe3LYX


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