[Milsurplus] ARB Antenna capacitor

[Hue Miller]

Yes, i think that's along the lines of what i was thinking. WIth all the 

additional capacitance to ground otherwise seen right at the ARB 

antenna.

-Hue
 

> From: n4fs at eozinc.com
> To: kargo_cult at msn.com; milsurplus at mailman.qth.net
> Subject: RE: [Milsurplus] ARB Antenna capacitor
> Date: Mon, 9 Dec 2013 09:41:21 -0500
> 
> What about simply, minimizing the effects of "suckout". 73 - Mike 
> 
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960 
> 
> -----Original Message-----
> From: milsurplus-bounces at mailman.qth.net
> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Hue Miller
> Sent: Monday, December 09, 2013 12:09 AM
> To: milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] ARB Antenna capacitor
> 
> My thinking was that this condenser would have minimal effect in attenuating
> stray oscillator inputs. I was thinking that the overall antenna capacity as
> seen by the ARB with multiple receivers connected plus the circuit through
> the ATC might be deemed ?too? far off the design "standard" capacity. A
> condenser of 36pF would pretty well define that antenna capacity, since it
> is a multiple lower than would be seen by the rest of the outboard wiring.
> Would a high capacity at the ARB antenna post detune the antenna's resonant
> circuit? I do not know. More wisdom (more inputs from others) is required.
> The impedance of the 36pF at 4495 kcs (for example :) is about 1000 ohms.
> Yes, that would make for a filter effect, considering the low impedance of
> the ARB input circuit to off-resonance frequencies. However for stray
> oscillator inputs at the same frequency the ARB is receiving, 1000 ohms, I
> think, is like, forgettable, considering the ARB input impedance.
> It was worth the question for me to learn that this was not a hammy mod.
> I believe I first saw it in a surplus store where most of the avionics of
> some plane had showed up, ARB, ATC, and who knows what else.
> -Hue
> 
> -----Original Message-----
> From: Mike Hanz
> Sent: Sunday, December 08, 2013 8:34 PM
> To: Hue Miller ; milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] ARB Antenna capacitor
> 
> On 12/8/2013 7:02 PM, Hue Miller wrote:
> > So the series capacitor was to somehow discriminate against, how? ( 
> > Not getting it. ) And not to diminish the total antenna capacity, nor 
> > to somehow protect the receiver?
> 
> Why would one want to decrease the antenna capacity seen from an ARB's
> perspective, Hue? I haven't found the mica transmitting cap on the ARB
> antenna input used in any other system other than where multiple receivers
> were attached to a common receive antenna. That should tell you something
> about its deployment. What we do know is that it is possible to reduce
> interaction through de facto bandpass filters, using inherent set antenna
> input capacities and inductances. What we do not know at the moment is
> whether the intent was to diminish interference from the ARB or the command
> sets. Further research is needed.
> 
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