Amp Switching

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  • Updated 5 years ago
Have two different HF amps.  Am considering cabling Amp1 to Ant1 and Amp2 to Ant2 on the 6700, then using an antenna switch with 60 dB of rated isolation.  In theory this puts >250mV on the Ant2 terminal when I'm transmitting on Ant1.  Is this a problem?
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Asher - K0AU

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Posted 5 years ago

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Tim - W4TME, Customer Experience Manager

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It is close, but it shouldn't damage the SCU.  250 mV(rms) is about 355 mV(peak) which equates to +1 dBm.  The SCU, if enabled, can handle in excess of +5 dBm input signal.  If the SCU connected to unused antenna is not active (no panadapters or slices are open and attached to it), then you have additional isolation when the radio's internal relays are not latched.

Either way, I'd be careful none the less.
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Asher - K0AU

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Tim,

Thanks!  Too close for comfort.  Calculated voltage at 1500W into a 1:1 SWR with 60dB isolation is 274mV rms. 

I can build a patch panel with more port to port isolation.
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Tim - W4TME, Customer Experience Manager

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Always better safe than sorry.
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Greg

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Asher,

If you are interested, I have something you may be able to use for this.  Its a thick aluminum backpane with 6 pairs of amphenol SO239 barrel connectors.  Email if interested.

73
Greg

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Lee, Elmer

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I use a patch panel  its more flexible and harder to make mistakes plus greater isolation.  I have the antennas on separate coaxes and then every thing else (all inputs and outputs)  from gear including watt meters tuners etc  appears on the panel in a 4x8 matrix.  This way I can pull the antennas completely when I shut the station.  The panel is screwed to the leg of my operating table so its very convenient to change things around 

73  W9OY
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Lee, Elmer

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The panel on the right allows any amp tx switch to be connected to any radio tx switch. Its just 1/4 phone plugs
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Tim - W4TME, Customer Experience Manager

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NICE SHACK!
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Asher - K0AU

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Are those barrel connectors or is there any hidden matrix cross-connect?
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Lee, Elmer

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All barrel connectors. The matrix is all out front except I did place the IO boxes for the swr meters directly behind the panel. I made 4 extra holes for expansion. The antenna coax comes in as free cables and they plug into the matrix when in use and lay on the floor when not in use. It makes it dead easy to update the shack with new gear etc.
(Edited)
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k0eoo

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very nice Lee,

I remember we had antenna patch panels on our ship like that.  The only difference was the patch cables and connectors were rated at 5kw and all the unused antennas automatically shorted to ground when not connected to a rig...  They were push-on-snap-lock connectors.  I see that type at swap meets on occasion....
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Paul Christensen, W9AC, Elmer

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What I've long thought about is a 19" universal coaxial patch panel that works like the multimedia panels seen for home CAT5/6, BNC, RCA, and speaker banana jacks where a panel uses all uniform cutouts say...10 on top and 10 on the bottom in a 3RU height.  Then, a smaller filler panel is fastened into the larger opening where the filler panels come in sizes cut for N, SO-239, BNC, RCA, and possibly SMA. 

I could easily lay this out in Front Panel Express software.  In small quantities, the panels are kinda' pricy -- but not too bad in larger quantities.   Possibly this has been thought about before.  Anyone know a source?  MFJ sells a 6x6 patch panel but there's no connector flexibility. 

Paul, W9AC

(Edited)
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Asher - K0AU

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PM me. Thinking along similar lines.