[Moon] Re: [Moon-net] Cavity question RX1AS PA 144Mhz

[Oene Spanjer]

Thanks to All who responded and I got several comments
in the same direction.
I am helped vy much and now know that I should use the
advised 55mm tube.
As Harm and Conrad stated, there will be too much compromised
in using the smaller diameter and off course I want to get the
best out of it !
Bodo gave me a link to a program by Agilent at
http://www.hp.woodshot.com/appcad/appcad.htm which is
very helpfull in calculating the cavity !

73 to All
Oene
PA3CWN



----- Original Message ----- 
From: "Conrad G0RUZ" <conrad at g0ruz.com>
To: "'Moon-Net'" <moon-net at list-serv.davidv.net>; "'Moon'" 
<moon at moonbounce.info>
Sent: Friday, July 20, 2007 4:51 PM
Subject: Re: [Moon-net] Cavity question RX1AS PA 144Mhz


>
> The approximate impedance can be calculated from 138log10*(1.08* D/d). All
> you need to do to preserve things is keep the ratio of the diameters the
> same. Basically the inverse of what F1CXX did, in this case the box could 
> be
> made 124 mm x 124 mm, but I personally would not do it. The whole cooling
> arrangement will be compromised, there will be more stray capacitance and
> the tuning may become more critical. F1CXX did the right thing, his looks
> like it won't fall over :-)
>
> 73
>
> Conrad G0RUZ
>
>
>
>
> -----Original Message-----
> From: moon-net-bounces at list-serv.davidv.net
> [mailto:moon-net-bounces at list-serv.davidv.net] On Behalf Of Oene Spanjer
> Sent: 20 July 2007 11:22
> To: Moon-Net; Moon
> Subject: [Moon-net] Cavity question RX1AS PA 144Mhz
>
> Hello All,
>
> I am building a RX1AS design PA right now and it has a half wave tube
> connected to the anode as resonator.
> This tube has a diameter of 55 mm and the lenth of the total resonator
> including cooler is 53 cm.
> The housing is 170mm by 170mm.
>
> I want to use a 40mm tube so the whole impedance of the resonator will
> change. I think it is going upwards.
> Now my question is what effect will this be ??  Too much mismatch ?
> and do I need to lenthen or shorten the resonator to get it in resonance ?
>
> I want to keep the same housing distances, but my feeling tells me that it
> should change also with 40mm tube, because the whole line can be seen as
> coax.
>
> Maybe it is best to use 55 mm tube instead, but I was just curious and
> cannot find any software that calculates it for me The tube used will be a
> GS-35b The info I refering to,  is at
> www.pa3csg.hoeplakee.nl/GS35-2M/GS35-2M.html
>
> Thanks in advance !
>
> 73 and have nice summer holidays !
> Oene
> PA3CWN
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