[hpsdr] Using Mercury to monitor final amplifier transmit signal

[Joe Martin K5SO]

Tom, 

To answer your question of how you might couple to your high power output, here as an example, I use two high-power directional couplers in series that are actually designed for microwave use; mine happen to be Narda 20 dB couplers designed for the 0.95-2 GHz range but when used at HF the coupling port provides much high attenuation than 20 dB at the coupling port.  The straight through ports can easily handle 1KW at HF and the coupling port at HF frequencies yields greater than 80 dB of attenuation.  Using two in series yields greater than 160 dB of attenuation that can then be fed directly to the input of Mercury.  This allows me to monitor my output signal at safe levels into Mercury when transmitting at 1KW.  

To connect two directional couplers as I indicate above,  connect the straight-through ports of one from KW PA, through to the antenna, then connect the coupling port of the first with a to the straight-through port of the second with a dummy load on the straight-through output of the second, then connect the coupling port of the second directly to Mercury.  

To obtain, say, an S-9 signal on your Mercury from a 1KW transmit signal you need about 130 dB of attenuation.  How you get that amount of attenuation is unimportant, using microwave directional couplers was handy for me because I happened to have them.

If you don’t happen to have any such directional couplers, an alternative method could be to switch a short whip antenna (an inch or two long) onto Mecury when transmitting in duplex mode in order to receive a sample of the "off the air” Tx signal being transmitted by your Tx antenna.  

There are numerous ways to accomplish what you wish to do.   You simply need to arrange to attenuate your Tx signal by 130 dB or so before putting the signal into Mercury.  

73,  Joe K5SO  


On Feb 7, 2013, at 1:46 AM, Phil Harman wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> 
>> Phil:  For your idea of using a relay, how do I disconnect the path to the
>> Penny sampling first?  Where does it come into Mercury?  Does Penny RF
>> sampling come in thru the antenna that needs to be part of the proposed
>> relay switching or it it at a lower level?
>> 
>> 
> 
> There is no specific sampling path - the signal from Penny to Mercury is
> simply RF leakage, perhaps via the T/R relay.
> 
> In which case if you can provide a low level sniff of the RF out from your
> linear and feed that to Mercury when on Tx you have your solution.
> 
> 73 Phil...VK6APH
> 
> 
> 
> 
>> 
>> 
>> 
>> 
>> 
>> -----Original Message-----
>> From: Phil Harman
>> Sent: Thursday, February 07, 2013 12:49 AM
>> To: Joe Martin K5SO
>> Cc: Tom Cathey ; hpsdr at openhpsdr.org
>> Subject: Re: [hpsdr] Using Mercury to monitor final amplifier transmit
>> signal
>> 
>> Hi Tom,
>> 
>> You could use one of the open collector outputs in Penny to operate an RF
>> relay that, when on Transmit, connected the antenna on Mercury to an RF
>> sampler at the output of the amplifier.
>> 
>> 73 Phil...VK6APH
>> 
>> 
>> _______________________________________________
>> HPSDR Discussion List
>> To post msg: hpsdr at openhpsdr.org
>> Subscription help:
>> http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
>> HPSDR web page: http://openhpsdr.org
>> Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/
>> 
>> 
> 
> 
> _______________________________________________
> HPSDR Discussion List
> To post msg: hpsdr at openhpsdr.org
> Subscription help: http://lists.openhpsdr.org/listinfo.cgi/hpsdr-openhpsdr.org
> HPSDR web page: http://openhpsdr.org
> Archives: http://lists.openhpsdr.org/pipermail/hpsdr-openhpsdr.org/


 1360248270.0