Re: MN-2000 Technical implementation
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I agree with Jim, VE7RF, except the configuration could be thought of as two series connected L-networks. Starting at the source end (TX, RX, TVCR) the first L-network is a shunt capacitance then a series inductance. The following L-network is a shunt capacitance then a series capacitance to the load (antenna). I guess the network could also be thought of as a different theme on the Pi-L network.
The present issue of QEX has an article on L-notworks. It is not for the faint of heart as it contains a lot of "j-omega", i.e., mathematics. If nothing else, one can view the various types of L-networks, one being the capacitance/capacitance type described above.
73,
On Sunday, April 2, 2023 at 01:10:33 PM EDT, Sean (KK6BEB) <seanlynch@...> wrote:
Thanks Bill and thanks Jim for the reference to the schematic. I¡¯m learning a lot. KK6BEB?
This looks like a T network. This configuration?is not as common as the Pi and L. The attached artical is just one of many on the web that discuss how these networks work. It may not be the best article, it was just one I thought looked like it would address your questions.
On Sun, Apr 2, 2023 at 9:32?AM Jim VE7RF < jim.thom@...> wrote: Both the references sited, are not even close to? the MN-2000.
IF u look at the schematic for the MN-2000, it consist of a PI network, followed by a series variable cap in the output leg to the ant.?
The 1st....' C1 cap' consists of a mess of paralleled? fixed? mica caps, that are progressively switched in by the progressive bandswitch.? ?On 10m, they use 5 x? 68 pf caps in parallel. Reason is, the mica caps don't handle RF current at the upper HF freqs, so 5 are used in parallel.? However, the mica's are stable, and don't drift.? On each lower band, a bigger and bigger mica is added to the grand total..that makes up the 'C1' cap.? ?The coil assy is identical to what's used in the L4B linear amp.? The bandswitch in the MN-2000 is also identical to the bandswitch in the L4B linear.?
The C2 cap in the MN-2000 is a 20-245 pf? air variable. The C3 cap is also a 20-245 pf air variable, but is wired in series with the output..then off to the ant.??
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Here's?a link to the manual...which includes the schematic at the end.?
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