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LF: Re: Re: Re: 475 kc Exiter /JUMA

To: <[email protected]>
Subject: LF: Re: Re: Re: 475 kc Exiter /JUMA
From: "mal hamilton" <[email protected]>
Date: Thu, 31 May 2012 18:01:23 -0000
References: <8BE4322932454ABBAF36917E7F0B7293@uwePC> <CAMFjj70+gM-ukas=NGMLyYwpL_wKnr-Mx3B6JH23XTr7yk_k9A@mail.gmail.com> <[email protected]> <034701cd3f1d$b69fa650$1502a8c0@Clemens04> <[email protected]> <63351021B87046C482A1433665C54902@uwePC> <000d01cd3f47$8f89e7e0$0401a8c0@xphd97xgq27nyf>
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PS
G4JNT built a 700w LF rig out of junk and has published the info to this group. Difficult to justify the high cost of Kits that have to be built and produce only 60W.
g3kev
 
----- Original Message -----
Sent: Thursday, May 31, 2012 4:08 PM
Subject: LF: Re: Re: 475 kc Exiter /JUMA

Uwe
I could build the same specification 60w rig for NO cost out of my junk box hi. The rig seems expensive for a kit and only 60 watts
The Ropex 130 w rig for 136 Khz was less than £200 new and already built, even that was expensive. I built a 1Kw rig for almost nothing out of my junk box and still have after many years.
I also have a couple of MF marine transmitters suitable for 500 lying in my garage !!
de mal/g3kev
 
----- Original Message -----
Sent: Thursday, May 31, 2012 3:10 PM
Subject: LF: Re: 475 kc Exiter /JUMA

Hi,
here is the  bill for my new JUMA TX500
 
Subtotal: 299.00€
Postage & Packaging: 26.00€
Tax: 68.77€
Grand Total: 393.77€
 
I´s by the way the 3rd kit I am building ( all bevore where built for others ..) but thats for my self ..
 
Uwe DK1KQ

 
Sent: Thursday, May 31, 2012 1:43 PM
Subject: Re: LF: 475 kc Exiter /JUMA
 
Hi Clemens,

Oh, OK. But anyway it was a very good hint to mention the JUMA 500 TX since it leads me to the CMCD design and this paper which nicely describes the problem of the VMCD desgin which i am trying in my first tests.
The output C of the FETs is the problem. Since i want to have a relatively high power (100W) at 12V DC, the primary impedance is very low. So i have to use FETs with a very low on-resistance, ideally as low as possible of course. To find them is no problem (e.g. IRFP4368), but the output C is much to high then. I tried a IRZF48N (2 of them of course) as a compromise between RDSon and Cout but am just getting 60% efficiency at 70W in the first attempt. That's not acceptable for a /p PA that has to stay compact, i.e. without a big heat sink and/or a fan...

The basics are well explained in this paper, makes fun to read :-)

73, Stefan/DK7FC

Am 31.05.2012 13:08, schrieb Clemens Paul:
It costs 300 Euro which is not to much.

Unfortunately you have to add 23%VAT tax within EU and shipping costs
which I estimate to 30-40 Euro.
So we end up somewhere around 400 Euro.
Interesting kit,though.

73
Clemens
DL4RAJ


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