DEMI 2MLDPA and 6700

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Wa t to order the new DEMI rig for my 6700 for some EME work... Any suggestions as to ordering with split or common feed line??? Any comments from those going this at all??
Tbx
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AH0U

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Posted 2 years ago

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Simon Lewis

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depends on a number of things ....

Mostly around preamps / amps. Do you have a preamp already or one in mind?

The reason why they do split line is to reduce the requirements for relays on the mast head.

To be honest I never understood it myself - I have a number of preamps that use 2 relays in the masthead box all successfully - even split lines need a switch somewhere that needs PTT - 12V etc

You can also reduce the number of relays in split lines by not switching the amp round the rx path I guess.

But its horses for courses as the mast head preamp gives you best bang on noise figure and gain enough to overcome losses in relays.

How are you going to integrate the PA?

Cheers

Simon ZL4PLM
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AH0U

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First of all, t x fer the reply.
I have a Henry 3002 amp. That has internal relax to bypass the amp on TX... So I thought I would run one 7/8 hardline from the amp to the mast mounted DEMI preamp that I would switch out of the line with a couple of vaccine DEMI relays that I have .... So I thought of using one coax line and bypassing the preamp on transmit all switch with a sequencer... Maybe even the one in the 6700.... Thoughts????
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Reg

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I previously owned a DEMI 2MLDPA.  From my perspective the EME related issue is only that it does not accept a 10 MHz Reference signal.  Even if your FLEX-6700 has a GPSDO you are at the mercy of the internal LO in the 2MLDPA.  It's fine for most modes but you should carefully evaluate the modes that you will operate and the required frequency stability.

On the matter of mast mounted pre-amps I recently purchased a Beko HPP-144 mast mounted preamp.  It is the first mast mount preamp that will pass 2.5 KW (headroom) on transmit.  

With a FLEX-6700 you will have no difficulty making EME contacts without an amplifier.

Reg (FLEX-6700+GPSDO owner)
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Simon Lewis

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the PA bricks are only gain blocks they are not transverters - they have no 10 MHz in as they do not have a LO in or any mixing - the blocks are simply a preamp and a PA in one unit with some switching. I could in effect do the same with a 144 high gain preamp and a MMIC/Brick PA stage and a relay/PPT section.

I'm not sure of the DEMI relay handling for power - on EME you need to plan for 100pc duty on components - JT65 at 1.5KW will find every hole in your station real fast - that lossy jumper its gonna get hot - poor relays, its gonna go, badly fitted N types - say bye bye to the centre pins - I have had them all :)

You can bypass the preamp using a high power relay that can handle the power you have .. prob 1KW?? I use a couple Narda relays and they can handle a couple KW ok. You can run a lower spec LMR400 or similar on rx around the amp and split the line on rx easy. The other important spec on the relay is isolation! - You might want to double switch the rx preamp. Just remember that 1.5KW at 60 dB isolation is still 15 mW at the preamp and thats enough to destroy it ... really needs no more than 1mW at the preamp port.

Sequencer - install a simple one from W6PQL etc - make sure you switch everything in sequence n slow - no need to rush - even 0.5 sec from RX to TX and back again and even more so if your switching a big relay contacts. 

Keep asking away :)

Cheers

Simon
(Edited)
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AH0U

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not sure I understand as the 2MLDP is an amplifier so why would it have a 10MHZ input???
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Chris DL5NAM

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EA4GLI - 8P9EH - Salvador

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Do we know what is the NF of the XVTR in the Flex 6700?
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John-K3MA

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Does anyone know how the Flex 6700 controls the new DEMI 2MLDPA with the remote option and USB that plugs into the back of the 6700?  There is not details in their manual except to say

"Through your latest version of Software for the FLEX 6500 and 6700 series products, you will be able to toggle the LDPA on and off for use. Toggling the LDPA off places it in the Bypass mode to allow additional amplifiers or Transverter to utilize the same port utilized by the LDPA. You will also have full control of the external Mast Mount LNA control that was described previously"

I cannot find any information on what is the latest version of SmartSDR that does this and what is the functioning of the GUI interface.

John K3MA
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Chris DL5NAM

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John i don't know is it helpful for you. There is another brand who offer this kind of PA and he offer a circuit diagram "how to use it". Sorry, if i am wrong.

http://shop.kuhne-electronic.de/module/mysydeshop/webforms/download_file.php?file=1964
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John-K3MA

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Chris thank you for the information.  I am specifically looking for the details on the SmartSDR remote control functionality that appears to be available for the DEMI unit from their manual.
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Simon Lewis

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info you need is here - not yet released