Antenna Separation

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  • Updated 3 months ago
Greetings to one and all!

I have a question about antenna arrangement to minimize multi-band interference and band rejection.

I just purchased a 6700 and want to add a DEMI 2MLDPArC amplifier for 2m, a Q5 L222-28r2 Transverter for 220 MHz, and a Q5 L432-28r2 Transverter for 430 MHz operation.  I have VERY limited room and would like to place all four antennas on top of the same 30 ft telescopic mast placed in a cross layout.  Each arm of the cross is 1m from the center, for a total of 2m apart on each arm of the mount and 1.4m diagonally to the adjacent antenna.  Based upon your knowledge and experience, will I have interference between antennas and transverters?   Is there enough band rejection in these various transverters and 6700 to reject the fundamental and the harmonics of the other bands?  Unfortunately I am not able to have vertical separation of the antennas and have limited ability to have horizontal separation.  The telescopic mast is 8ft tall in it’s collapsed position and 30ft in the extended position.

I have not yet purchased the antennas, but am planning:  the MFJ-1796 that operates on 40m. 20m, 15m, 10m, 6m, and 2m for HF, and Cushcraft antennas ARX-450B for 450MHz, ARX-220B for 220 MHz, and ARX-2B for 2m operation.  I am already considering not installing the 2m components on the MFJ-1796 so I don’t over-load the HF if I am operating the 2m through the XVTR port/Rx ports.

The plan is to have a variation of the posted full duplex 2m/430Mhz that is posted on the website.  The 2m would always be received through RX A and the 220 and 430 would be switched into the RX B port.

Do you think this will work and is the antenna separation and band rejection in the transverters adequate? 

Thank you so much for your assistance!!!


Jeremy

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Jeremy Gugel

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Posted 3 months ago

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Sergey, R5AU

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Hi Jeremy !
i guess easyliest description to reach full duplex without trouble described are here- https://www.amsat.org/a-simple-desense-filter-for-mode-j-satellites/
i have tested : with 144/432 yagi with ccommon feed over duplexer
- isolation over 45db(min) 
- with power on 2m ~25watts visible signal on PAN of my flex ~ S5-7
 i am using 2m Amp and 432 transverter by DEMI. In case you need more level of isolation you can use same duplexer for 2m separetely as a filter.

(Edited)
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Jeremy Gugel

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Thank you for the suggestion!
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Jeremy Gugel

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The next problem appears to be finding appropriate parts.  There are a number of candidates for the 2m/430MHz duplexer, the problem is the 2m/220MHz part for the Q5 50W Transverter.  I have been searching for hours and have only found two parts that have 2m/220MHz in their title.  The problem is, upon reading the specification, the 220MHz bandwidth is actually a couple of hundred megahertz, so it will also pass the 70cm band.  The other issue is power handling.  The Q5 transverter is 50W, so I would want at least a 100W part.  I am leery of placing a 50W part with a 50W transverter because it is not clear what their definition of power handling is.  This is a VERY LONG WINDED way of saying, can anyone please suggest some parts?
Many Thanks!

Jeremy
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Sergey, R5AU

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Jeremy, you can choose desired passband/reject filter from well known vendor: https://procom.dk/products/filters/band-pass-filters  That parts are well known and tested by many HAM`s  or choose as well suitable from here: https://www.diamondantenna.net/Product_Catalog/plexers.html
probably MX324 will be good enought ?
(Edited)
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Jeremy Gugel

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Hi Sergey!

Do you know if they make a bandpass filter/duplexer for the 1.25m band?  It appears all the parts listed are for either higher or lower frequencies.

Many Thanks!

Jeremy
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Jeremy Gugel

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SUCCESS!!!
It looks like the Diamond MX214 duplexer is narrowband and covers just the 1.25m band!  Unless anyone has a different suggestion, this one looks like it will work:

https://www.diamondantenna.net/mx214d.html


Sergey, I really appreciate your help with my problem!!!  I also apologize that I did not see your comment pointing to Diamond in the first place!

Jeremy


(Edited)
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Sergey, R5AU

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Jeremy no worries at all, BTW need to keep in mind unused ports on duplexer/diplexers should be terminated, for ex. with any like: https://www.digikey.com/products/en/connectors-interconnects/coaxial-connectors-rf-terminators/382?k...
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Jeremy Gugel

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Definitely understood - Thanks!

Jeremy