Topband: Single antenna port xcvr but want to employ separate receive antenna

[James Rodenkirch]

I've used the loop and a KD9SV preamp  with the  vertical before, JC, and no overload problems ...I run QRP power during Top Band contests.
Your cautionary notes are noted and appreciated!
Jim R. K9JWV

> From: n4is at comcast.net
> To: rodenkirch_llc at msn.com; topband at contesting.com
> Date: Mon, 13 Jan 2014 11:33:21 -0500
> Subject: Re: Topband: Single antenna port xcvr but want to employ	separate	receive antenna
> 
> Hi James
> 
> There are several solutions for a separated receive port. However let me
> comment on some details,
> 
> 1- Small Delta loop. To be a receiver antenna the antenna gain need to be
> less than 20 db, why ? simple. Connect a power meter and a 50 ohms load on
> the Small  Delta loop and measure how much power is captured from the TX
> antenna, I know several guy the burn the RX port on ICOM and YAESU radios
> using transmit antennas as receiver and injecting 100W into the RX port when
> transmitting with a legal limit amplifier.  Port isolation and RF protection
> must be the first concern for any solution. If the antenna used for RX is
> resonant on the same TX band , you  can really burn you RX front end. 
> 
> 2- Switch speed. The receive port need to switch fast than TX port. 20ms is
> not enough, most small frame relays switch around 20ms , To play safe it is
> necessary < 10 ms. Another thing to consider.
> 
> 3- The RX antenna only will add some SN if it adds some directivity,
> otherwise the attenuator at -20db will  do the same job.
> 
> 4-  Isolation, on low bands if you have s9+10db noise and only 50 db
> isolation between the RX and TX port, the signal from the TX antenna will be
> add to you RX signal degrading the signal to noise and reducing side and
> back nulls form the RX antenna.
> 
> I can list another several reason to the subject but the T/R switch is a
> very important part of the receiver system if you want to have some
> improvement on the signal noise. 
> I sent one RTR-1 to T6LG to use with a good Preamp from KD9SV and a Delta
> Flag antenna using twisted pair. Without the RTR-1 the system would not
> perform well as it did.
> 
> Just my two cents.
> 
> Regards
> JC
> N4IS
> 
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of James
> Rodenkirch
> Sent: Monday, January 13, 2014 8:36 AM
> To: Top Band Contesting
> Subject: Topband: Single antenna port xcvr but want to employ separate
> receive antenna
> 
> Have my vertical working great and have a small Delta-loop low band receive
> antenna BUT the Ten Tec Jupiter doesn't have a separate receive antenna like
> a K2, for instance (I borrowed a K2 to try out but the buttons/controls are
> to small for me to operate as I have a severe case of peripheral neuropathy,
> courtesy of Agent Orange).So, I am up and running and will be in the CQ 160
> contest at the end of January but have no means, currently, of switching
> rapidly 'tween the top loaded vertical and loop. A T/R switch won't "do it"
> for me....so looking at a DX Engineering RTR-1A but sure don't like the
> price!!http://www.dxengineering.com/parts/dxe-rtr-1a
> Anyone have an RTR-1 or 1A that is excess to their needs and willing to sell
> OR have another idea of how I can employ a separate receive antenna when I
> have one antenna port?
> Thank you, in advance, for any replies....off line replies work for me.
> 72/73, Jim Rodenkirch K9JWV 		 	   		  
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