[hpsdr] Using Mercury to monitor final amplifier transmit signal

[Tom Cathey]

Thanks, guys.

Yes, this helps, Joe.

That's what I thought - Merc is receiving the display signal thru the 
connector.  So I need to download W5WC's RX1 version to get the duplex to 
display an external signal from the amplifier.

It pays to know what the actual final signal is doing for IMD.  The Penny 
may be -60 dB 3rd order, but many amplifiers these days are lucky to break 
above -30dB.  And with poor tuning or overdriving they can be in the -20's. 
This includes some solid state amplifiers that I've tested.

I just built up a very clean 4CX-350FJ  grid driven linear that has about 
40Db of gain.  10 mW in and 100 W output.  Penny is the driver.   The cool 
thang is the 3rd order IMD measures out to about -50dB when running 25W out. 
This is a perfect driver for an 8877.  The IMD bottleneck then becomes the 
8877.  That's why I need the high level display - to keep an eye on the 8877 
amp.


I'll download the RX1 and give it a go.

Thanks again, Joe!

Tom, K1JJ



-----Original Message----- 
From: Joe Martin K5SO
Sent: Friday, February 08, 2013 1:02 AM
To: Tom Cathey
Cc: HPSDR List
Subject: Re: [hpsdr] Using Mercury to monitor final amplifier transmit 
signal

Hi Tom,

Sorry for the confusion.  To run DUPLEX mode with PowerSDR you need to run 
Doug W5WC’s RX1 version of PowerSDR v2.2 (11/24/12).  It has a “DUP” button 
on the front panel that the RX2 version does not have.

When you transmit with the DUP button active your panadapter display shows 
the Rx spectrum during transmit as well as during receive.  By tuning your 
Mercury Rx freq to your Tx freq you may monitor the frequency on which you 
are transmitting.  This displayed signal is the signal that arrives at the 
BNC input connector on Mercury when running in DUP mode.

Works here.

Maybe this info helps?

73,  Joe K5SO


On Feb 7, 2013, at 10:03 PM, Tom Cathey wrote:

> ***** High Performance Software Defined Radio Discussion List *****
>
>
> Joe and Phil,
>
> I tried to disable the signal displayed by Mercury when Penny is 
> transmitting.  It is always there, even when I remove the ant BNC plug off 
> the back of Merc's board.  It appears to be coming in from somewhere else, 
> like thru the board connector.
>
> Is this the way it should be?  Or am I toggled on for the duplex mode 
> without realizing it?  How is the duplex mode enabled?
>
> Bottom line is, with or without an antenna or even a connector on the ant 
> input to the Merc, when Penny is transmitting,  Penny's signal is strong 
> and stable on the Merc pan display. This is with no external amplifier 
> connected. I would like to see this low level signal disappear so that I 
> can then inject some external sampled RF from the amplifier into Merc's 
> ant input.
>
> What am I missing?
>
> Tom, k1JJ
> 

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