[MRCA] [armyradios] RE: AB-1241 - DC current rating?

[W2HX]

Thanks, how does one rate a capacitor's power handing capability? I've seen WVDC ratings, but what do I look for?  
And John - if I put the cap between the antenna and the tuner, then wouldn't the tuner tune out the capacitance? Or do I still need to look at something around 50 ohm at HF?

 
73 Eugene W2HX
 

-----Original Message-----
From: mrca-bounces at mailman.qth.net [mailto:mrca-bounces at mailman.qth.net] On Behalf Of WA5CAB at cs.com
Sent: Wednesday, April 25, 2012 2:26 PM
To: mrca at mailman.qth.net
Subject: Re: [MRCA] [armyradios] RE: AB-1241 - DC current rating?

Plus the current rating of the capacitor must be adequate for the transmitter output power into 50 ohms.  I.e., you can't use a standard disk ceramic.

In a message dated 04/25/2012 13:05:49 PM Central Daylight Time, jfor at quikus.com writes: 
> There are two typed of DC blocks...  One has a capacitor in the center 
> conductor only; the other in both the center and shield. You want the 
> former.
> 
> Look at the spec sheet for the block. You want the capacitor's 
> impedance to be <<50 Ohms at your lowest operating frequency. This 
> easy enough at microwave frequencies, but more of a challenge at HF.
> 
> -John
> 
> ================
> 
> 
> 
> >Yes that is a good suggestion. Would a series cap do the trick (isn't
> that
> >whats in a dc block?) And if so, what effect would that have on 
> >antenna impedance and tuning it out?
> >Thanks
> >
> >
> >
> >73 Eugene W2HX
> >
> >
> >-----Original Message-----
> >From: D. Platt [mailto:jeepp at comcast.net]
> >Sent: Wednesday, April 25, 2012 12:27 PM
> >To: W2HX
> >Cc: 'armyradios at yahoogroups.com'; mrca at mailman.qth.net
> >Subject: Re: [MRCA] AB-1241 - DC current rating?
> >
> >I don't think you want to present DC to a virtual short, in any case, 
> >whether or not the transformer or the radio could accept/stand it..  
> >Why not simply add a coaxial DC block to the transmission line and 
> >eliminate the issue, altogether.  Just a suggestion...
> >
> >de Jeep - K3HVG
> >
> >On 4/25/2012 12:01 PM, W2HX wrote:
> >>Hi there. I am referring to the "hubcap" stand often used with the 
> >>AS-2259/GR NVIS antenna.  This base has a dc resistance of zero 
> >>because of a transformer within it.  I am looking to use this with a 
> >>radio that has a DC voltage on the antenna BNC, but current limited to about 30ma.
> >>Anyone have an opinion whether a constant 30ma DC current on this 
> >>transformer would be tolerated by the transformer in the base?
> >>
> >>http://www.prc68.com/I/Images/AB1241_PRC104.jpg
> >>(image courtesy Brooke N6GCE)
> >>
> >>
> >>73 Eugene W2HX
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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